Patent Application
20160068843
The present invention relates to compositions and methods for use of resistance-proof siRNA therapeutics for prevention and treatment of influenza viral infections.
Influenza A virus is one of the most prevalent respiratory tract infections in humans (Michaelis et al. 2009). Twenty to fifty million U.S. citizens are infected annually resulting in 40,000 deaths. In addition, respiratory virus infections, including flu, are considered to be the leading cause of exacerbation of asthma (Cohen and Castro 2003). For these reasons, the flu virus is considered a significant health threat and a top priority biodefense pathogen by the CDC and National Institutes of Health (NIH). The high risk associated with natural and artificial (bioweapon) flu infection is derived from a number of sources including (1) the ease by which the virus is distributed via aerosol, (2) its ability to escape protective immunity by frequent changes in viral antigens (antigenic drift) and (3) the periodic emergence of new virulent strains resulting from the reassortment of RNA segments between viruses from two different species (antigenic shift). Antigenic drift is the virologic basis for seasonal flu epidemics, while antigenic shift is theorized to be the source of pandemic infections.
Recently, the World Health Organization (WHO) has reported a disturbing increase in the incidence of H5N1 avian influenza infections in human populations. Since 1995, multiple countries have reported outbreaks of H5N1 (Balicer et al. 2007; Uyeki 2009). While the majority of documented cases involve direct viral transfer from wildfowl to human, the WHO and CDC are sufficiently concerned about potential human-to-human transmission to have issued repeated alerts of a H5N1 pandemic. In April 2009, a so-called swine-origin influenza A (H1N1) virus (2009 H1N1 or S-OIV), was identified in Mexico (Dawood et al. 2009). This viral strain originates from triple-reassortant swine flu and is readily transmitted between humans. After its discovery, 2009 H1N1 rapidly spread throughout the world within few weeks. From April to October 17, it was estimated by CDC that 14 million to 34 million infectious cases, 63,000 to 153,000 hospitalizations, and 2,500 to 6,000 2009 H1N1-related deaths occurred. In addition, the epidemiological data indicates that this disease primarily affects people younger than 65 years old, very different from seasonal influenza. Although the death rate caused by 2009 H1N1 was only about 0.45%, lower than the 1918 pandemic (an estimate of 2.5%) and avian flu outbreaks (about 60%), multiple concerns exist. First, mutations in the virus may lead to a more pathogenic strain that increases mortality. Second, since the more deadly avian flu (H5N1; >62%) has also been demonstrated in swine and humans, it is possible that recombination between the 2 strains in either species may result in a highly pathogenic and deadly strain that can migrate readily between species. Third, 2009 H1N1 may reassort with the seasonal flu strains that are resistant to some of the antivirals. This will result in significant difficulties in treating the infected patients.
Currently, two strategies, vaccines and small molecule therapeutics, are utilized to control the spread of flu. Vaccines are predominantly developed from killed or cold-adapted viruses and take advantage of the host immune system to provide limited immunity. While reductions in flu related illness and deaths can be attributed to this approach, especially among high-risk individuals, there are several reasons why vaccines offer limited protection from pandemics. First, the most commonly developed vaccines are based on inactivated viruses. These reagents induce only weak immunity that provides protection for brief (6 month) periods. In light of the facts that 1) only 60-80% of the immunocompetent population and 30-40% of individuals with chronic respiratory ailments (e.g. COPD, asthma) or compromised immune systems receive sufficient protection from vaccination (Kunisaki and Janoff 2009), and 2) vaccines fail to provide protection if administered after infection, alternative approaches are needed to adequately protect the population. A second shortcoming of vaccines involves the complex relationship that exists between the rapid evolution of flu and the limitations associated with reformulating and producing sufficient quantities of vaccines for large populations. The constant evolution of viral antigens frequently renders the previous year's vaccine ineffective and places significant reliance on epidemiological/surveillance data to accurately predict future circulating strains. While these approaches are frequently adequate, the flu outbreak of 2003 and the pandemic in 2009, where predictive models failed to accurately forecast the circulating serotypes and vaccine production capabilities were incapable of responding in a timely manner, demonstrate the need for alternative technologies that can rapidly counter newly emerging serotypes.
In addition to vaccines, there are currently four antiviral drugs approved by the U.S. Food and Drug Administration (US FDA). Two of these agents, amantadine and rimantadine, target the viral ion channel protein, M2. The remaining drugs, zanamivir and oseltamivir, inhibit the function of neuraminidase (NA). While both classes of compounds effectively reduce the severity and duration of flu infections, their efficacy is only limited to the first 24-48 hours after the development of symptoms and can often be associated with side effects. Of still greater concern is the emergence of stable and transmissible drug resistant flu strains (Griffiths 2009; Schirmer and Holodniy 2009). Though the frequency at which NA-targeting drug resistance arises can vary considerably and the associated virulence of resistant strains is often attenuated, exceptions (e.g. the E116G mutation) have been documented (Lackenby et al. 2008). Resistance to oseltamivir has also been identified in the 2009 pandemic virus (www.who.int). Thus, development of a new and flexible anti-flu therapeutic platform is essential.
RNA interference (RNAi) is a naturally occurring, highly specific mode of gene regulation. The mechanics of RNAi are both exquisite and highly discriminating (Siomi and Siomi 2009). At the onset, short (19-25 bp) double stranded RNA sequences (referred to as short interfering RNAs, siRNAs) associate with the cytoplasmically localized RNA Interference Silencing Complex (RISC) (Jinek et al. 2009). The resultant complex then searches messenger RNAs (mRNAs) for complementary sequences, eventually degrading (and/or attenuating translation of) these transcripts. Scientists have co-opted the endogenous RNAi machinery to advance a wide range of basic studies. As siRNAs can be designed to target virtually any gene and can be introduced into cells by a variety of methods, RNAi, represents a highly flexible platform by which researchers and clinicians can control diseases including viral infectious diseases. RNAi has been employed to target a wide range of human pathogenic viruses, including flu and other emerging respiratory infectious viruses (Ge et al. 2003 and 2004; Tompkins et al. 2004; Li et al. 2005, Zhou et al. 2007; McSwiggen and Seth 2008; Zhou et al. 2008; Cheng et al. 2009; Sui et al. 2009). The ability of RNAi to 1) efficiently limit viral replication without reliance on host immune functions, and 2) target multiple genes and/or sequences simultaneously, makes this an ideal therapeutic approach for pathogens that have rapidly evolving genomes (e.g. flu). In particular, siRNA therapeutics may benefit specific patient populations such as infants or the elderly who do not produce a strong immune response to a vaccine and may not have full protection from such a program.
The mutation rate of the influenza virus is estimated to be 1.5×10-5 per nucleotide per infection cycle (Parvin et al. 1986). This high frequency of mutation is the underlying basis behind the emergence of variants (escapers) that are resistant to current M2- and NA-targeting chemotherapeutics (Lackenby et al. 2008; Colman 2009). Though RNAi mediated gene knockdown exhibits a degree of resilience to changes in the siRNA target sequence, mismatches in key positions (including nucleotides localized to the siRNA sequence (positions 2-7 of the antisense strand) and target cleavage (positions 9-11) regions can significantly disrupt siRNA efficacy. Multiple studies in which single siRNAs have been developed to target viral pathogens (e.g. HIV, polio virus, Hepatitis B and C viruses) have documented the emergence of escapers. In most of these cases, resistant virus contains one or more changes in the sequence of the siRNA target site (Gitlin et al. 2005; Grimm et al. 2006; von Eije et al. 2008). Mutations in the sequence outside of the siRNA target site were also found in HIV resistant mutants (Leonard et al. 2008). The changes in the RNA secondary structure or/and an evolutionary tuning of viral transcriptional regulation may serve as evasion mechanisms. As escaper populations appear rapidly, novel strategies must be identified if effective RNAi-based viral therapeutics are to become a reality.
Therapeutic strategies that may prevent and/or reduce the emergence of resistant variants include: (1) targeting regions of essential (viral) genes that are highly conserved, and (2) targeting two or more viral genes simultaneously. Moreover, as the rate at which two resistance inducing mutations occur is the product of the frequency of either mutation occurring separately (i.e. 2.25×10-10 per infection cycle), multigene targeting is expected to lessen the frequency at which resistant viral pathogens appear (Gitlin et al. 2005; Grimm et al. 2006; von Eije et al. 2008). We predict that strategies that incorporate both approaches: multiple-gene targeting of conserved regions, will yield the most effective therapeutic platform to combat influenza by RNAi.
There are many biological barriers and factors that protect the lungs from foreign particles, such as a thick and elastic mucus layer that may bind inhaled drugs and remove them via mucus clearance mechanism, low basal and stimulated rates of endocytosis on the apical surfaces of well-differentiated airway epithelial cells, the presence of RNase extra- and intra-cellularly, and the presence of endosomal degradation systems in the target cells, among others. Overcoming the difficulties concerning respiratory tract delivery and effective cellular entry and function will pave the way for siRNA as a pulmonary flu therapeutic. In addition, the delivery vehicle and mode of administration must be chosen to be appropriate to the stage of the infection and provide the fastest onset of silencing at the required site of action, e.g. early stage infection/prophylaxis at the lungs and later stage disease through systemic administration. Among them, pulmonary delivery through inhalation provides a noninvasive means for site specific administration to different regions of the lung—resulting in increased bioavailability and fewer adverse effects than with intravenous administration. In a pandemic setting this delivery approach will allow ease of administration directly by patients. In addition, the findings that flu virus is capable of infecting vascular endothelial cells and that endothelial cells express both human and avian flu receptors have urged the development of vascular endothelial cell-directed delivery of antiviral to control some of the systemic syndromes caused by the virus (Sumikoshi et al. 2008; Yao et al. 2008).
Intranasal (i.n.) delivery of siRNA in a mouse model system has successfully reduced expression of a number of endogenous pulmonary targets. Similarly, i.n. delivery of siRNAs targeting a range of viral pathogens (including flu, SARS, and RSV) have successfully knocked down viral gene expression and diminished viral titers (Ge et al. 2004; Bitko et al. 2005; Li et al. 2005). Some delivery carriers were also shown to deliver siRNAs to the mouse lungs via intravenous injection (Ge et al. 2004). In summary, development of formulations for pulmonary delivery of siRNA should be further advanced.
The present invention relates to compositions and methods for use of resistance-proof siRNA therapeutics for prevention and treatment of influenza viral infections. As used herein, the term “resistance-proof” means able to meet the challenge of viral resistance due to viral mutations and antigenic drift by continuing to target the changed viruses.
The compositions include a pharmaceutical composition comprising an siRNA molecule that targets a conserved region of an influenza virus gene and a pharmaceutically acceptable polymeric carrier. In one embodiment, the polymeric carrier condenses the molecules to form a nanoparticle.
In a preferred embodiment, the composition comprises at least two different siRNA molecules and a pharmaceutically acceptable carrier. One of the siRNA molecules targets a conserved region of an influenza virus gene and the other siRNA molecule targets a conserved region of a different influenza virus gene. The genes can be in the same virus strain or in two different virus strains. The composition can include one or more additional siRNA molecules that target still other influenza virus genes in the same virus strain or in different virus strains.
As used herein, an “siRNA molecule” or an “siRNA duplex” is a duplex oligonucleotide, that is a short, double-stranded polynucleotide, that interferes with the expression of a gene in a cell, after the molecule is introduced into the cell, or interferes with the expression of a viral gene. SiRNA molecules are chemically synthesized or otherwise constructed by techniques known to those skilled in the art. Such techniques are described in U.S. Pat. Nos. 5,898,031, 6,107,094, 6,506,559, 7,056,704 and in European Pat. Nos. 1214945 and 1230375, which are incorporated herein by reference in their entireties.
Whenever a single siRNA molecule is described herein, it should be understood that the description can apply to more than one of the molecules in the preferred composition. Except for structural differences because the two or more siRNA molecules target conserved regions in different viral genes, the molecules can be the same in structure. For example, they can have the same number of base pairs. The molecules can also have additional structural differences. For example, they may differ in length, i.e., the number of base pairs that each contains.
One or more of the ribonucleotides comprising the molecule can be chemically modified by techniques known in the art. In addition to being modified at the level of one or more of its individual nucleotides, the backbone of the oligonucleotide can be modified. Additional modifications include the use of small molecules (e.g. sugar molecules), amino acids, peptides, cholesterol, and other large molecules for conjugation onto the siRNA molecule.
In the present invention, the siRNA molecules target conserved regions of influenza virus genes. As used herein, “target” or “targets” means that the molecule binds to a complementary nucleotide sequence in an influenza virus gene, which is an RNA molecule, or it binds to mRNA produced by the gene. This inhibits or silences the expression of the viral gene and/or its replication. As used herein, a “conserved region” of an influenza virus gene is a nucleotide sequence that is found in more than one strain of the virus, is identical among the strains, rarely mutates, and is critical for viral infection and/or replication and/or release from the infected cell.
In one embodiment, the siRNA molecule is a double-stranded oligonucleotide with a length of about 16 to about 35 base pairs. In one aspect of this embodiment, the molecule is a double-stranded oligonucleotide with a length of about 19 to about 27 base pairs. In another aspect of this embodiment, it is a double-stranded oligonucleotide with a length of about 21 to about 25 base pairs. In still another aspect of this embodiment, it is a double-stranded oligonucleotide with a length of about 25 base pairs. In all of these aspects, the molecule may have blunt ends at both ends, or sticky ends with overhangs at both ends (unpaired bases extending beyond the main strand), or a blunt end at one end and a sticky end at the other. In one particular aspect, it has blunt ends at both ends.
In one embodiment, the sequences comprising the siRNA molecule have no homology to a mammalian gene. In one aspect of this embodiment, the mammal is a human, mouse, ferret, or monkey.
The siRNA molecule targets any influenza virus, including influenza A and influenza B. In one embodiment, the influenza virus is an influenza A virus. This virus includes subtypes H1N1, H3N2, H5N1, H7N2, H7N9, and H9N2 among others of the form HxNy denoting the types of hemagglutinin and neuraminidase sequences.
The siRNA molecule targets the conserved region of any influenza virus gene. In one embodiment, the virus gene is an influenza A virus gene selected from the group consisting of M2, PA, PB (including PB1 and PB2), and NP.
In one aspect of this embodiment, the siRNA molecule targets the M2 gene of the influenza A H1N1, H3N2, H5N1, H7N2, H7N9, and H9N2 subtypes. In a further aspect of this embodiment, the siRNA molecule comprises the sense sequence: 5′-GAGCGAGGACUGCAGCGUAGACGCU-3′.
In another aspect of this embodiment, the siRNA molecule targets the NP gene of the influenza A H1N1, H3N2, H5N1, H7N2, H7N9, and H9N2 subtypes. In a further aspect of this embodiment, the siRNA molecule comprises the sense sequence: 5′-GUGUGGAUGGCAUGCCACUCUGCTG-3′.
In still another aspect of this embodiment, the siRNA molecule targets the influenza A PB1 gene. In a further aspect, the influenza A PB1 gene is the H1N1 PB1 gene, and the siRNA molecule is selected from the group consisting of PB1a, 5′-UGGCAAAUGUUGUGAGAAAdTdT-3′ (sense sequence), PB1b, 5′-UGAGAAAGAUGAUGACUAAdTdT-3′ (sense sequence), PB1c, 5′-UGACAUGAGUAUUGGAGUAdTdT-3′(sense sequence), and PB1d, 5′-CCUGCAAGUUAGUGGGAAUdTdT-3′(sense sequence).
In still another aspect of this embodiment, the siRNA molecule targets the influenza A PA gene. In a further aspect, the influenza PA gene is the H1N1 PA gene, and the siRNA molecule is selected from the group consisting PAa, 5′-GGAUAGAACUUGAUGAAAUdTdT-3′(sense sequence), PAb, 5′-GAGAAGAUCCCAAGGACAAdTdT-3′ (sense sequence), and PAc, 5′-GGAAGGCUCUAUUGGGAAAdTdT-3′(sense sequence).
In one embodiment, the siRNA molecule of the composition is selected from the molecules listed in Tables 2, 4, and 5. In one aspect of this embodiment, the siRNA molecule comprises the sense sequence: 5′-ACGCUGCAGUCCUCGCUCACUGGG-3′ and the antisense sequence: 5′-CCCAGUGAGCGAGGACUGCAGCGUA-3′. In another aspect, the siRNA molecule comprises the sense sequence: 5′-GCAAUUGAGGAGUGCCUGAdTdT-3′ and the antisense sequence: 5′-UCAGGCACUCCUCAAUUGCdTdT-3′.
The siRNA molecules of the invention also include ones derived from those listed in Tables 2, 4, and 5 and otherwise herein. The derived molecules can have less than the 25 base pairs shown for each molecule, down to 16 base pairs, so long as the “core” contiguous base pairs remain. That is, once given the specific sequences shown herein, a person skilled in the art can synthesize molecules that, in effect, “remove” one or more base pairs from either or both ends in any order, leaving the remaining contiguous base pairs, creating shorter molecules that are 24, 23, 22, 21, 20, 19, 18, 17, or 16 base pairs in length. Thus, the derived molecules consist of: a) 24 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; b) 23 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; c) 22 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; b) 21 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; d) 20 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; e) 19 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; f) 18 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; g) 17 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5; and h) 16 contiguous base pairs of any one or more of the molecules in Tables 2, 4, and 5. It is not expected that molecules shorter than 16 base pairs would have sufficient activity or sufficiently low off-target effects to be pharmaceutically useful; however, if any such constructs did, they would be equivalents within the scope of this invention.
Alternatively, the derived molecules can have more than the 25 base pairs shown for each molecule, so long as the 25 contiguous base pairs remain. That is, once given the specific sequences shown in the tables, a person skilled in the art can synthesize molecules that, in effect, “add” one or more base pairs to either or both ends in any order, creating molecules that are 26 or more base pairs in length and containing the original 25 contiguous base pairs.
In one embodiment, the siRNA molecule includes a potency enhancing motif. As used herein, the term “potency-enhancing motif” means an RNA sequence included in the siRNA molecule that increases the therapeutic effect of the molecule in an animal model compared to the same molecule without the sequence. For example, when the molecules are tested in a virus-challenged mouse model, they exhibit much more potent antiviral activity than other influenza-specific siRNA molecules not containing this motif, even though the two types of influenza-specific siRNA molecules have the same antiviral activity in a cell culture test. An example of such a motif is the sequence: sense, 5′-ACUCC-3′; antisense, 5′-GGAGU-3′.
The siRNA molecule may also include an immune-stimulating motif. Such motifs can include specific RNA sequences such as 5′-UGUGU-3′ (Judge et al., Nature Biotechnology 23, 457-462 (1 Apr. 2005)), 5′-GUCCUUCAA-3′ (Hornung et al., Nat. Med. 11, 263-270(2005). See Kim et al., Mol Cell 24; 247-254 (2007). These articles are incorporated herein by reference in their entireties. These are siRNA sequences that specifically activate immune responses through Toll-like receptor (TLR) activation or through activation of key genes such as RIG-I or PKR. In one embodiment, the motif induces a TH1 pathway immune response. In another embodiment, the motif comprises 5′-UGUGU-3′, 5′-GUCCUUCAA-3′, 5′-GGGxGG-3′ (where x is A, T, G and C), or CpG motifs 5′-GTCGTT-3′.
The pharmaceutical compositions of the invention preferably contain more than one type of siRNA molecule, wherein each molecule targets a different conserved region of an influenza virus gene or a conserved region of different influenza virus genes. In one embodiment comprising a composition with two different siRNA molecules, one siRNA molecule comprises the sense sequence: 5′-UACGCUGCAGUCCUCGCUCACUGGG-3′; and the antisense sequence: 5′-CCCAGUGAGCGAGGACUGCAGCGUA-3,′ and the other siRNA molecule comprises the sense sequence: 5′-GCAAUUGAGGAGUGCCUGAdTdT-3′ and the antisense sequence: 5′-UCAGGCACUCCUCAAUUGCdTdT-3′.
The pharmaceutically acceptable carrier is a polymer. Examples of polymers include a biodegradable histidine-lysine polymer, a biodegradable polyester, such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA), and poly(lactic-co-glycolic acid) (PLGA), a polyamidoamine (PAMAM) dendrimer, (Polyallylamine (PAA) and poly(dimethylaminoethyl methacrylate) (PDMAEM), a cationic lipid, or a PEGylated PEI. Cationic lipids include DOTAP, DOPE, DC-Chol/DOPE, DOTMA, and DOTMA/DOPE.
In one embodiment, the carrier is a histidine-lysine copolymer that forms a nanoparticle with the siRNA molecule. In one aspect of this embodiment, the diameter of the nanoparticle is about 100 nm to about 400 nm. In another aspect of this embodiment, the composition is a lyophilized powder.
In one embodiment, the polymeric carrier further comprises a Pegylated-PEI with a molecular weight smaller than 6KD.
The compositions of the invention are used prophylactically or therapeutically against influenza infections, especially influenza A infections. A prophylactically or therapeutically effective amount of the composition is administered to the subject. The term “subject” refers to any animal, including humans. Thus, the invention includes a prophylactic method of preventing an influenza infection in a subject or reducing the severity of a subsequent infection, and it includes a therapeutic method of treating an influenza infection in a subject. In one embodiment, the subject is a mammal. In one aspect of this embodiment, the mammal is a laboratory animal, such as a rodent, ferret, or non-human primate. In a particular embodiment, the mammal is a human.
The compositions are administered by techniques known to those skilled in the art. For example, they may be administered intravenously, intraperitoneally, and via the airway, such as intranasally. The dosages are determinable by those skilled in the art, given the teachings contained herein.
As used herein, the singular forms “a,” “an,” and “the” refer to one or more, unless the context clearly indicates otherwise.
The following examples illustrate certain aspects of the invention and should not be construed as limiting the scope thereof.
Gene sequences are obtained from the databases of sequenced flu genes (1) and imported into the siRNA predictor tool (2). The predictor tool identifies all potential siRNAs of a given length (e.g. 25mer) against the gene and the list is exported and saved. Using an siRNA analysis tool, each gene in the database is evaluated to determine identity with the siRNA sequence. A score is applied to each strain of influenza based on degree of identity with the siRNA sequence and region of identity.
SiRNA therapeutics may benefit specific patient populations such as infants or the elderly who do not produce a strong immune response to a vaccine and may not have full protection from such a program. The cross reactivity between siRNA against H1N1 and H5N1 strains of the virus will hopefully provide a significant benefit should the rapid ability to spread evidenced by the former virus be combined with the highly pathogenic and lethal effects of the latter.
Using our bioinformatics programs we have identified 25mer blunt ended siRNAs against key regions of genes important to the replication lifecycle of influenza viruses. These genes included M2, PB and PA genes but each and every gene of all influenza viruses can be included in this list. The software for siRNA prediction determines siRNAs of a given length (19-25 base blunt ended duplex RNAs) that have identity to a gene that we are aiming to silence. A flow chart showing the process can be found in
The score is further adjusted based on the need to cover specific viral strains e.g. a higher weighting (100%) can be applied for H1N1 and H5N1 strains than, say H3N2 which may not be prevalent in an outbreak or pandemic. The output is a list of siRNA sequences and the range of viral strains that may respond to gene silencing by the siRNA. At this point we would refine the algorithm by empirically evaluating the activity of the most interesting siRNAs for each molecular viral target by measuring the effect of single siRNAs transfected in MDCK cells in vitro on viral titer in these cells. Upon identification of the most potent siRNAs we would then examine combinations of 2 or 3 of these with in vivo models (animal models) to observe effects on decreasing viral titer of H5N1 or H1N1 strains after intranasal administration of the siRNA either as a single entity or as a cocktail (of 3 distinct siRNAs).
The software predicts siRNAs with appropriate thermodynamic properties, removes known immune stimulating motifs and those siRNAs which were not within the appropriate range for GC content (35-65%). A list of the siRNA sequences that meet our final criteria is exported to a file and saved on a computer hard drive. Another software tools then opens the siRNA list file and sequentially examines each record in the database for identity between the predicted siRNA sequence and the gene sequence for the viral strain and gene. Two searches can be made: 1) for exact identity between siRNA sequence and gene sequence across all bases and 2) a partial match—where specific bases within the siRNA do not match exactly with the paired gene sequence. In the latter case the software outputs the region of the siRNA where there is an exact match in capital letters e.g. CCATCGTTCCAAGGGTACGGCATAA would imply that an siRNA with this sequence would match exactly with the complementary sequence in the targeted gene. In this case the match would be 100%. If a region is not identical with the predicted gene sequence it is represented by small case letters for the bases. E.g. an siRNA against the same sequence as the first case but which differed at the last base would be written as CCATCGTTCCAAGGGTACGGCATAa. It is well known that the minimum effective length of an siRNA that can silence a gene with high potency is a 19 base duplex. In the example given this was predicting a 25mer siRNA.
We have previously demonstrated that a 25mer is more potent than a 19mer in silencing a gene in vitro. To ensure optimal thermodynamic properties for the siRNAs it is important that the first 2 bases do not include a T or A while it is better that the last 2 bases in the siRNA ARE a T or A. The reason for this is that it is believed that such bases allow the duplex siRNA to unwind more easily and pairing of the antisense strand within Dicer. While a region of identity in many siRNAs can include both a T and an A base at the terminus, it is sometimes not feasible to identify an siRNA with absolute identity in this region. Consequently, if the base pairing in the terminal region is not exact this may help with efficacy of the siRNA. Therefore our algorithm for scoring predicted siRNA sequences provides a weighting for siRNAs that meet all of our criteria (exact identity along entire length AND have the correct bases at both the 2 start bases and 2 end bases in the sequence). Such a sequence would be weighted according to the formula:
[(Predicted siRNA length−minimum effective siRNA length)*(consecutive base matches)]/number of base mismatches+1.E.g.,in our example,a25mer with exact identity would score as follows[(25−19)*(25)]/1)=150.
If we had a 25 mer siRNA with the following sequence CCA TCG TTC CAA GGG TAO GGC ATA A, i.e., 1 base mismatch at the end, the value would look like [(25−19)*(24)]/2)=72. A sequence as follows CCA TCG TTC CAA GGG TAO GTC ATA A would score [(25−19)*(19)]/2)=57 so a base mismatch further from the terminus would reduce the score. Further, a sequence like CCA TCG TTC CAA GGG TAO Gttccgg where all of the last 6 bases match would be scored as [(25−19)*(19)]/6)=19. This provides an estimate of how to rank the siRNAs of interest to pursue against a viral strain. Additional weighting can be provided based on the prevalent disease strain in the general population (e.g. H1N1 versus H5N1 for example) or even within a strain the isolate that is being observed most frequently.
After identification of the siRNA sequences that meet our criteria, additional software tools allow comparison between these siRNA sequences and a database containing all gene sequences of sequenced strains of the influenza viruses (a combined list from the NCBI flu database and biohealthbase files). The bioinformatics tools identify influenza strains exhibiting 100% identity to the predicted siRNA sequences and output from the queries provided the viral gene the siRNA would recognize and the strain of the virus in which that sequence was found. Additionally we can get a value incorporating the weighting score which allows for siRNAs which are not identical to the entire gene region of interest. Interestingly, siRNAs against one viral gene did not show overlap with other viral genes. Furthermore, as shown below in
By identifying siRNA sequences against other key target genes within the virus and then looking at overlap between the number of strains of flu that these siRNA cocktails may then target we have shown that a combination of an siRNA against M2 with broad strain specificity (
We can see that strain coverage increases to ˜500 fully sequenced flu viruses. The degree of coverage for H1N1 and H5N1 is about equal suggesting these selected siRNAs may be targeting conserved regions within many of these sequenced strains. We also see coverage of less pathogenic strains such as H3N2 with the combined sequences. Such conservation in gene regions may provide a point of vulnerability for the influenza virus since these regions may be expected to exhibit lower frequencies of mutation and make them better targets for therapeutic intervention. By multiplexing the therapeutic strategy (delivery of siRNAs against more than one viral gene) we can expect to further limit the potential escape of the virus from therapeutic pressure by mutation in a single gene. The prospect of mutation in two genes at point covered specifically by siRNA sequences is extremely unlikely.
Even by including these two siRNAs in a cocktail we may target as many as 500 of the ˜1700 H1N1 strains in the biohealthbase database and a similar number of H5N1 strains. The cross-targeting between these 2 virus types means we will provide a single therapeutic against a geographically widespread but less pathogenic virus (H1N1**; producing 816 deaths in 134503 cases; or a 0.6% death rate) with cross reactivity against the less widespread but more lethal avian flu virus (H5N1; producing 254 deaths from 406 cases; a 62% death rate).
There are 2 ways to predict siRNAs against conserved regions of viral genes. One way is to align all the genes from multiple strains and identify overlapping regions within the gene and then determine whether siRNAs with relevant pharmacological properties can be designed against these specific regions. This approach severely limits the number of siRNAs that can be predicted and siRNAs designed with these criteria may exhibit lower potency in gene silencing.
The method we have chosen is to predict siRNAs de novo against each gene sequence within all sequenced viral strains applying the optimal thermodynamic criteria for siRNA potency. This provides a database containing siRNAs that can rapidly be pressed into use in a cocktail of multi-targeted siRNAs. After the siRNA sequences are predicted we then compare the predicted siRNA sequence across all genes in all viral strains to identify those that exhibit the ability to show identity to and silence the gene in the largest number of species. We will then compare the strain coverage that might be expected when we combine siRNAs against select genes into a cocktail targeting three distinct genes. Furthermore, we designed criteria into our selection algorithm that can provide a “weighting” for the most prevalent flu strain in the general population and allows tailoring of a cocktail to aid in treatment of flu. The ability to rapidly synthesize and characterize siRNAs together with the fact that an siRNA of the same length demonstrates similar charge and hydrophobicity as well as molecular weight makes the formulation of such siRNAs very much easier than a vaccine or small molecule. Consequently a delivery vehicle that shows delivery of one siRNA sequence to the lung may be expected to deliver an siRNA against a distinct sequence with equal efficacy. This benefit means that as the predominant flu virus changes—either seasonally or geographically—the siRNA therapeutic cocktail can also be rapidly tailored to ensure therapeutic benefit to patients.
Currently our algorithms and predictions have been based on siRNA sequence identity with the gene target within a virus gene. SiRNAs as short as 19mer have been demonstrated to effectively silence genes in vitro and in vivo. Since our siRNAs are 25 bases in length, there may be some sequence redundancy that will still allow complete silencing of a target gene. We are building tools to allow examination of regions that may not be 100% identical to the siRNA sequence across all bases but which show identity in 19 consecutive bases. The ability to identify those genes that do not exhibit complete identity along all 25 bases of the siRNA may increase the number of viral strains that can possibly be targeted by an siRNA. The prediction algorithm provides an increased weighting for genes with identity across all 25 bases and a weighting of the results based on a change in the expected thermodynamic properties can be made where shorter regions overlap (see above). Such a scoring scale allows increased scores for consecutive regions of identity.
The siRNAs predicted from our algorithms are further evaluated with in vitro assays and the algorithm modified to incorporate the empirical results based on efficacy of the siRNAs against viral titer. In this way possible regions within the viral genome with secondary structure that inhibits the pairing of the siRNA and the gene within DICER can be excluded from consideration for siRNA prediction. As we identify these regions their sequence may be included in an exclusion algorithm for the siRNAs to be tested. The data obtained from these studies will allow us to predict siRNAs with the greatest scope of viral inhibition to be included in a therapeutic cocktail that can be administered intranasally.
One study (
The viral nucleic acid drug screening needs strict laboratory conditions, such as H5N1 or H1N1 may require BSL-3 condition. In order to screen siRNA inhibitors targeting the influenza virus in an ordinary (BL-2) laboratory, we used the viral gene segments amplified by PCR from cDNA of H1N1 viral genome and subcloned them into a Luciferase reporter gene vector. As a result, we were able to screen the siRNA inhibitors and other types of drugs against viruses in our BL-2 laboratories.
The psiCHECK™-2 Vector is designed to provide a quantitative and rapid approach for optimization of RNA interference (RNAi) activity. These vectors enable the monitoring of changes in expression of a target gene fused to the reporter gene. In this vector, Renilla Luciferase is used as a primary reporter gene, and the gene of interest can be cloned into the multiple cloning region located downstream of the Renilla Luciferase translational stop codon. Initiation of the RNAi process toward a gene of interest can result in cleavage and subsequent degradation of fusion mRNA. Measurement of decreased Renilla Luciferase activity is a convenient indicator of RNAi effect.
The cDNAs of H1N1 were kindly provided by Prof. BJ Zheng of University of Hong Kong. The restriction enzymes were obtained from Fermentas Corp. and were dissolved in the buffer supplied by the manufacturer. X-gal and IPTG were purchased from Solarbio Corp. (Solarbio Corp., Sigma Chemical Co.). All other enzymes and reagents used in this study were described previously. Hela cells were obtained from Institute of Biochemistry and Cell Biology, SIBS, CAS. Taq DNA polymerase, T4 DNA ligase and pMD19-T vector were purchased from Takara Co., Ltd. The psiCHECK™-2 Vector was purchased from Promega Corporation.
Amplification of Influenza Genes.
The cDNA of H1N1 was used as the template with primer sequences employed in the amplification designed with Primer 5.0 software. The primers were synthesized by Generay Biotechnology (Shanghai, China) and their sequences are shown in Table 1. Underlines were the SgfI site and PmeI site, respectively. The polymerase chain reaction (PCR) was carried out on a MG96+/LongGene Peltier Thermal Cycler (Hangzhou, China). NS, PB1 and M used the following PCR parameters 94° C. for 4 min followed by 35 cycles of 94° C. for 20 s, 58° C. for 30 s and 72° C. for 2 min, with a final extension step at 72° C. for 10 min. NP and NA used the following PCR parameters: 94° C. for 4 min followed by 35 cycles of 94° C. for 20 s, 54° C. for 30 s and 72° C. for 2 min, with a final extension step at 72° C. for 10 min. PB2 used the following PCR parameters: 94° C. for 4 min followed by 35 cycles of 94° C. for 20 s, 59° C. for 30 s and 72° C. for 2 min, with a final extension step at 72° C. for 10 min. HA used the following PCR parameters: 94° C. for 4 min followed by 35 cycles of 94° C. for 20 s, 57° C. for 30 s and 72° C. for 1.5 min, with a final extension step at 72° C. for 10 min.
Generation of Recombinant Vectors
The PCR products were separated on 1.5% (w/v) agarose gels. The relevant bands were extracted and recovered from the agarose gels using a UNIQ-10 DNA gel extraction kit (Shanghai Sangon Biological Engineering Technology and Service Co. Ltd, China). The purified gene fragments were inserted into the pMD19-T vector (Takara, Japan) according to the manufacturer's instructions. The recombinant T vectors were digested with restriction enzymes SgfI and PmeI. The relevant bands were extracted and recovered from the agarose gels using a UNIQ-10 DNA gel extraction kit (Shanghai Sangon Biological Engineering Technology and Service Co. Ltd, China). The purified gene fragments and the psiCHECK-2 vevtor was digested with the restriction enzymes SgfI and PmeI ligated at 16° C. with T4 DNA ligase. The vector was transformed into competent E. coli DH5a using a CaCl2 method and then transformed clones were selected on agar plates containing Amp+. The positive recombinant clones were confirmed by colony PCR and restriction enzyme digestion. The sequences of the inserted fragments were confirmed by digestion with SgfI and PmeI.
Cell Culture and Transfection Conditions
Hela cells were cultured on RPMI 1640 (HyClone) supplemented with 10% fetal bovine serum, 50 units/mL penicillin, and 50 Ag/mL streptomycin (HyClone). Cells were incubated in a humidified 5% CO2 atmosphere at 37° C. Cell transfection was performed with the plasmid (0.04 ug/50 ul medium) and siRNA (0.02 nM, 0.1 nM, 0.5 nM, 2.5 nM, 12.5 nM and 62.5 nM) using Lipofectamine 2000 (Invitrogen). The complexes of plasmids and Lipofectamine 2000 or siRNA and Lipofectamine 2000 were prepared according to the manufacturer's protocols. The solution of Lipofectamine 2000 was added dropwise to the solution of plasmid DNA or the solution of siRNA. 4-5 h later, the medium was replaced with RPMI 1640 medium containing 10% fetal bovine serum, and the cells were incubated for another 12 h.
Analysis of Luciferase Activity
For analysis of Luciferase activity, Hela cells were seeded in 96-well culture dishes (5000 cells each well) 12 h before transfection and transfected with recombinant vectors and siRNAs, every group had three repeats. Luciferase was measured using the Dual Luciferase Kit (Promega, Madison, Wis.) following manufacturer's instructions and read in a luminometer (Promega, Madison, Wis.). In this assay, the activities of Photinus pyralis and Renilla reniformis Luciferases are measured sequentially from a single sample. The firefly reporter is measured first by adding Luciferase Assay Reagent II to generate a luminescent signal. After quantifying the firefly luminescence, this reaction is quenched, and the Renilla Luciferase reaction is simultaneously initiated by adding Stop & Glo® Reagent to the same tube.
Amplification of H1N1 Gene Sequences with PCR
In order to amplify the influenza genes NS, PB1, M, NP, NA, PB2 and HA from the cDNA of H1N1, we designed the specific primer pairs (Table 1) for each of those gene sequences with the SgfI and PmeI restriction sites in either forward primers or reverse primers. Specific NS gene (˜650 bp), PB1 gene (˜350 bp) and M gene (˜750 bp) sequences have been amplified (
TA Cloning Obtained the Specific Subclones
In order to identify whether the genes of interest have been subcloned, we performed the TA cloning with the amplified DNA fragments purified from the PCR products. After inserting the DNA fragments into the T vector, we digested the plasmids using restriction enzymes SgfI and PmeI and resulted in successful subclones with NS inserts about 2.7 kb and 650 bp respectively (
Construction of the Recombinant Luciferase Vectors
Influenza gene fragments were inserted into the vector psiCHECK-2 efficiently. Digestions of these plasmids with SgfI and PmeI have confirmed that all plasmids contain two inserted DNA fragments. The NS inserts into psiCHECK-2 vector is about 6.3 kb and 650 bp respectively (
After inserting the psiCHECK-2 vector with other gene sequences, the gel electroporation assay was applied for evaluation of the correct insertions.
Five Figures (from 9 to 13) were used to demonstrate that correct sequence alignments of the subcloning sequences covering NS (
Screening the Potent siRNAs by Dual-Luciferase Reporter Assay System
We investigated whether the siRNAs designed could knock down the target genes by dual-Luciferase assay system. Co-transfection of siRNAs and recombinant Luciferase vectors in Hela cells was performed to examine the changes in Luciferase activities. Down regulation of the Luciferase expression was observed when the psicheck-2 vectors containing the NS gene fragment and a selected siRNA-NS were co-transfected in Hela cells (
The viral nucleic acid drug screening needs strict laboratory conditions. We successfully constructed the influenza viral gene dual-Luciferase repoter vectors psi-NS, psi-PB1, psi-M, psi-NP, psi-NA, psi-HA and psi-PB2, so that we can screen the drugs against viruses in an ordinary laboratory. The results indicated that the effects siRNA-25mer inhibitors are seemingly better than siRNA-21 mer inhibitors.
Sixteen siRNA Oligos were Tested
The siRNA sequences are 25 mer in length and listed in Table 2, were ordered from Qiagen (Germantown, Md.) covering multiple key genes of influenza A (H1N1).
5′-GCCCAGUGAGCGAGGACUGCAGCGU-3′
Cell Lines and Viruses Used in the Experiments
MDCK was maintained in MEM or DMEM (Invitrogen, USA) supplemented with 10% heat-inactivated fetal bovine serum_(FBS) and antibiotics (100 U penicillin G/mL and 100 μg streptomycin/mL). Influenza virus strain A/New Caledonia/—20/1999 (H1N1) used in the experiment was prepared in MDCK cells and virus titers were determined by TCID50. All experiments with H1N1 virus were performed in BSL-3 laboratory. The siRNAs were reverse transfected to MDCK cells using Lipofectamine™ RNAiMAX (Invitrogene, USA) as described in the company's instruction. After incubating the cells for 16, 18 hrs, the cells were infected with the viruses and followed by detection of viral replication. 24 hours after infection, RNA were extracted from the cells and followed by real time RT-PCR to detect the relative quantities of replicated viral RNA.
Real-Time RT-PCR
Real-time RT-PCR was carried out as described previously [39]. Briefly, H1N1 infected MDCK and Mock_MDCK were harvest at 24 hr after infection. Total RNA was extracted from the_infected cell samples using RNeasy RNA isolation Kit (Qiagen,_Germany) and reverse transcribed using Superscript II Reverse Transcriptase and Oligo dT primer (Invitrogene, USA), according_to the manufacturer's protocol. Viral mRNA copies were measured by SYBR green M63000 Real-Time PCR System (Stratagene, USA), using primers NP-Forward: 59-GAC CAG GAG TGG AGG AAA CA-39, NP-Reverse: 59-CGG CCA TAA TGG TCA CTC TT-39; M2-Forward: 59-CGT CGC TTT AAA TAC GGT TTG-39, M2-Reverse: 59-CGT CAA CAT CCA CAG CAT TC-39 b-Actin-Forward: 59-CGT ACCACT GGC ATC GTG AT-39, b-Actin-Reverse: 59-GTG TTG GCG TAC AGG TCT TTG-39. The reactions were performed at 95° C. 10 mins, 40 cycles of 95° C. 1 min, 60° C. 1 min, 72° C. 1 min, followed by melting curve analysis according to instrument documentation (Stratagene M63000). All reactions were done in triplicates and the results were normalized by b-action.
Based on these results, we can determine at certain degree the potencies of some siRNA oligos for silencing the viral genes which may inhibit viral replication and infection. As indicated in
The same group of siRNA oligos as shown in Table 2 was tested in a different laboratory.
Cell Lines and Viruses Used in the Experiments
MDCK was maintained in MEM or DMEM (Invitrogen, USA) supplemented with 10% heat-inactivated fetal bovine serum_(FBS) and antibiotics (100 U penicillin G/mL and 100 μg streptomycin/mL). Influenza virus strain A/New Caledonia/—20/1999 (H1N1) used in these experiments was prepared in MDCK cells and virus titers_were determined by TCID50. All experiments with H1N1 virus were performed in BSL-3 laboratory.
Preparation and Transfection of siRNAs
The siRNAs targeting M, NP, or PA, or PB1 gene of H1N1 influenza virus (Table 2) were ordered from Qiagen. The siRNAs were reverse transfected to MDCK cells using Lipofectamine™ RNAiMAX (Invitrogen, USA) as described in company's instruction. After incubating the cells for 16′18 hrs, the cells were infected with the viruses and followed by detection of viral replication. 24 hours after infection, RNA were extracted from the cells and followed by real time RT-PCR to detect the relative quantities of replicated viral RNA.
Influenza Virus Infection and Viral Load Detection
MDCK cell line in 24-well plates was infected with viruses at moi of 0.005, 0.5 (2 mg/mL trypsin was used in the infection process of H1N1). After incubation for 1 hr, the infected medium was removed and MEM without FBS was added. Cell supernatants were collected at different time points. The viral load was detected by hemagglutination (HA) and/or plaque assays as described previously [39]. Briefly, the HA assay was carried out in U-bottom 96 well plates. Serial 2-fold dilutions of virus samples were mixed with an equal volume of a 0.5% suspension of turkey erythrocytes (Lampire Biologic Laboratories, Pipersville, USA) and incubated at room temperature (RT) for 45 mins. Wells containing an adherent, homogeneous layer of erythrocytes were scored as positive. For plaque assay, serial 10-fold dilutions of virus sample were added into a monolayer of MDCK cells. After 1 hr incubation, the virus was removed and the cultures were overlaid with 1% semi solid agar-MEM. Three days after infection, plaques were visualized by staining of crystal violent.
The siRNA oligos were reverse transfected to MDCK cells using Lipofectamine™ RNAiMAX (Invitrogene, USA) as described in company's instruction. After incubated the cells for 16, 18 hrs, the cells were infected with the viruses and followed by detection of viral replication. The NPa-siRNA and NPc-siRNA have IC50 around 50-100 μM. The M2b-siRNA and M2d-siRNA have IC50 about 25 μM (see labels in Table 3). These observations are consistent with the other evaluations demonstrated in the
A similar procedure was applied for evaluation of 36 siRNA oligos with homologues to PB1 and PA genes of influenza A virus for their antiviral activities with MDCK cell culture. The potent siRNA oligos (Table 4) were selected based on their IC50 for silencing PB1 and PA genes of influenza A virus (H1N1) resulting viral titer downregulation in the cell culture. Interestingly, PB1 siRNAs are more potent (IC50<12.5 μM) than PA siRNAs (IC50<25 μM), and all 8 siRNA oligos have exhibited potent anti-H1N1 activity with IC50<25 μM. Based on this study and the previous study with 25mer siRNA, we can see that the length of siRNA duplexes did not show significant difference regarding their antiviral activities. Therefore, in our future in vivo study, we will test both 21 mer and 25mer siRNA oligos for their antiviral potencies.
Cell Dissociation
Culture medium from 90% confluence MDCK culture was discarded. Cells were washed with 10 ml PBS. MDCK was dissociated using by 4 ml Trypsin/EDTA at 37° C. for 20 to 30 minutes. Trysin activity was neutralized by 20 ml MEM medium+10% FBS+P/S, and cells pelleted by centrifugation at 300×g, 5 minutes. Cells were resuspended in MEM medium+10% FBS, counted with a haemocytometer and normalized cell to 2×105 cell per ml for reverse transformation.
siRNA Preparation
siRNA (20 numole) was dissolved in 200 ul DEPC-treated water to give 100 pmole per ul stock. Lipofectamine RNAimax was diluted 1:1000 with Opti-MEMi medium. On a 96 well round bottom suspension culture plate, 195 ul diluted lipofectamine was added to to row A, and 100 ul to each well from row B to row H. 5 ul dissolved siRNA each from the siRNA panel was added to a well in row A. The samples were mixed thoroughly by pipette up-and-down.
Virus Challenge (Performed in P3 Lab)
All siRNA transfected cells were washed with PBS twice. SOHI H1N1 (p6,2×105 PFU/ml) was diluted with MEM containing 2 ug/ml TPCK-Trypsin to final 200 PFU/ml. 100 ul diluted virus was added to each well, to give a final 20 PFU/well (˜0.001 moi). After incubation for 48 hours at 37° C., in a CO2 incubator, the cytopathic effect (CPE) was scored, and the rough viral titre was checked with haemagglutination assay. The viral titer can also be quantified by
real-time PCR.
HKP-siRNA Nanoparticle
Histidine-lysine polymers (HKP) have been applied for siRNA delivery in vitro and in viva A pair of the HK polymer species, H3K4b and H3K(+H)4b, has a Lysine backbone with four branches containing multiple repeats of Histidine, Lysine or Asparagine. When this HKP aqueous solution was mixed with siRNA at a N/P ratio of 4:1 by mass, the nanoparticles (average size of 150 nm in diameter) were self-assembled (
Measurement of HKP-siRNA Nanoparticles
Using Brookhaven Particle Sizer 90 Plus, we have measured HKP-siRNA nanoparticles for their average size and Zeta-potential in addition to the electron microscopic observation.
Primary Cell siRNA Delivery with HKP
To establish in vitro silencing system, we explored cells for both tranfectability and responsiveness to IL-13 stimulation with mouse embryo fibroblast (MEF) cell model. Cell responsiveness to IL-13 was seen with high transfection efficiency with Ribojuice and HKP. Over many cell lines studied, MEF cells released eotaxin from IL-13 induction in a dose-dependent response (data not shown). Next, we tested the transfection efficiency in vitro with available transfection reagents, among them, ribojuice (similar to jetPEI) and HKP have given best results. Over 93% of MEF cells have been transfected with those two reagents using florescent siGLO siRNA as an indicator, measured by flow cytometry analysis (
Respiratory Tract siRNA Delivery
We further tested HKP-siRNA nanoparticle for respiratory track delivery. To compare the delivery efficiency of HKP-siRNA, we also included D5W (5% glucose) and DOTAP in the testing groups. The Kunming mice (25 g in average) were treated by HKP-siRNA nanoparticle solution, D5W and DOTAP with Cyclophilin B specific siRNAs, through both intranasal and intratracheal deliveries. The device used in the study came from BioLITE Intubation Illumination System, HKP-siRNA formulation was administrated with 50 μl in volume each time. From
Small Molecular Weight PEG and PEI
The PEG8 and PEI1.8K is one pair and PEG4.57-PEI25K represents another pair for the small molecular weight PEG-PEI conjugation. The preferred N/P ratio for this type of PEG-PEI/siRNA nanoplex is 7 to 10. To calculate the N/P ratio for the first carrier using the following formula: N/P=325×{[(m/17800)×41.86]/n}. Where N is mole number of N in the co-polymer molecule and P is mole number of P in the siRNA, (m) is the gram number of PEG-PEI, and (n) is the gram number of siRNA. For example: N/P is 10, and siRNA is 0.00003 (30 μg), you have: 10=325×{[(m/17800)×41.86]/0.00003}, therefore: M=[(10/325)×0.00003]/41.86]×17800=0.000392 g (392 μg). We can translate the N/P ratio (10) for PEG8-PEI1.8K/siRNA into the w/w ratio: 393/30=13/1.
Prepare PEG-PEI-siRNA Solution
An aqueous solution of siRNA was added drop-wise to DEPC-treated water containing PEG-PEI while vortexing. Different copolymer concentrations were used to provide polymer-siRNA nanocomplexes with different N/P ratios. After addition, the mixture was vortexed for an additional 20 seconds and then allowed to incubate at room temperature for 30 minutes before analyses or use. When N/P ration 10, When using 3 μg siRNA per dose, 39 μg of PEG-PEI should be used, When using 10 μg siRNA per dose, 130 μg of PEG-PEI should be used, When using 30 μg siRNA per dose, 390 μg of PEG-PEI should be used. Total volume for each dose should be 100 μl. When N/P ration 7, When using 3 μg siRNA per dose. 27 μg of PEG-PEI should be used. When using 10 μg siRNA per dose, 90 μg of PEG-PEI should be used. When using 30 μg siRNA per dose, 270 μg of PEG-PEI should be used. Total volume for each dose should be 100 μl.
For the Second Carrier
To calculate the N/P ratio for the second carrier using the following formula: N/P=325×{[(m/34140)×581.39]/n}. Where N is mole number of N in the co-polymer molecule and P is mole number of P in the siRNA, (m) is the gram number of PEG-PEI, and (n) is the gram number of siRNA. For example: N/P is 10, and siRNA is 0.00003 (30 μg), you have: 10=325×{[(m/34140)×581.39]/0.00003}, therefore: M=[(10/325)×0.00003]/581.39]×34140=0.0000542 g (54 μg), We can translate the N/P ratio (10) for PEG4.57-PEI25K/siRNA into the w/w ratio: 54/30=1.8/1. An aqueous solution of siRNA (300 μg/mL) was added drop-wise to DEPC-treated water containing PEG-PEI (395 μg/ml) while vortexing. Different copolymer concentrations were used to provide polymer-siRNA nanocomplexes with different N/P ratios. After addition, the mixture was vortexed for an additional 20 seconds and then allowed to incubate at room temperature for 30 minutes before analyses or use. When N/P ration 10: When using 3 μg siRNA per dose, 4.8 μg of PEG-PEI should be used; When using 10 μg siRNA per dose, 18 μg of PEG-PEI should be used; When using 30 μg siRNA per dose, 54 μg of PEG-PEI should be used. Total volume for each dose should be 100 μl. When N/P ration 7: When using 3 μg siRNA per dose, 3.9 μg of PEG-PEI should be used; When using 10 μg siRNA per dose, 13 μg of PEG-PEI should be used; When using 30 μg siRNA per dose, 39 μg of PEG-PEI should be used. Total volume for each dose should be 100 μl. Optional: Particle size was determined by dynamic light scattering (DLS) on a 90 plus particle size analyzer (Brrokhaven Instruments, Holtzville, N.Y. USA)
Mouse Model with H5N1 Viral Challenge
Female Balb/c mice at age of 4-6 weeks were used for establishment of H5N1 challenged model for evaluation of the prophylactic and therapeutic benefit of siRNA therapeutic in vivo. Most cohort groups had five mice and a couple of them had ten mice. The mice were challenged with H5N1 virus (strain A/Vietnam/1194/04) at a 10 times of LD50. All 5 animals in the control group died between 7-10 days after viral inoculation through nasal drops.
Prevention Treatment
Mice were given PEG-PEI-siRNA via intra-tracheal instillation with 100 μg (siRNA)/100 μl D5W solution one day before viral inoculation and then additional 100 μg (siRNA)/100 μl D5W solution was given at the same time of the viral inoculation. The siRNA used in this study was selected from a number of previous studies and it is a 21 mer siRNA containing a “potency-enhancing motif”. When 100 μg of NP specific siRNA packaged with PEG-PEI nanoparticle formulation was intranasally or intratracheally addressed (100 μg/dose×2) to the healthy mice before the viral challenge, 100% of the testing mice were survived and fully recovered, even if they were viral challenged later. If only one of 100 μg/dose was used, the survival rate dropped to 60%. If the dosage of siRNA was further decreased, the survival rate is further dropped into 40% (
Therapeutic Treatment
After the viral challenge for 12 hours or 24 hours, various dosages of PEG-PEI-siRNA were used for therapeutic treatment evaluation. When 100 μg/dose at 4 times/daily for two days was applied, 60% of mice were survived. When 100 μg/dose at 3 times/daily for three days was applied, only 40% of mice were survived (
An Interesting Motif
Due to the protection potency of certain siRNA sequences, a 5 nucleotide motif was identified: Sense, 5′-ACUCC-3′; Antisense, 5′-GGAGU-3′. Although the exact mechanism of action of this motif for improving the infected animal survival is not clear, the experiments for prophylactic and therapeutic benefits are very substantial.
Prophylactic Treatment with or without the Motif
We selected siRNA oligos against for influenza genes: NP, PB1, PB2 and PA. Three siRNA oligos were selected to target each of these genes with one oligo containing the motif but other two oligos are not. For prevention treatment, 100 μg of PEG-PEI-siRNA was intratracheally administrated to the animals one day before the viral inoculation. Another 100 μg of PEG-PEI-siRNA was intranasally administrated to the animals at the same time as the viral inoculation.
Therapeutic Treatment with or without the Motif
Based upon the prophylactic treatment result, we selected siRNA specific to NP gene of influenza A for the therapeutic treatment evaluation. At 24 hour time point post viral inoculation, we dose animals with PEG-PEI-siRNA with different regimens: on day one, 200 μg for intravenous administration and 100 μg for intranasal administration; on day two, 100 μg for intranasal administration; on day four, 100 μg for intranasal administration; and on day six, 100 μg for intranasal administration. As the result, animals treated with PEG-PEI-siRNA containing PEM have 60% survival rate, otherwise 0% survival in the control group. The study were conducted twice with N=10 and N=5 with the same results (
Based upon the studies on the prophylactic and therapeutic treatments with or without PEM, we decided to compare the selected siRNA drug (PEG-PEI-siRNANP) with Ribavirin, Zanamivir and a different siRNA inhibitor (also targeting NP gene of influenza A) published by a different group. Ten mice per group were challenged by 10 times LD50 of H5N1 virus strain A/Vietnam/1194/04. 24 hours after viral inoculation, the mice were treated with regimens illustrated in
We use the following figures to explain how we identify potent siRNA sequences with broad coverage against most influenza viral genes.
In order to select a group of siRNA sequences with potent anti-influenza virus using cell culture assays, Influenza virus A/California/07/09(H1N1)pmd09 from the viral strain collection of the Center for Disease Control (CDC, Atlanta, Ga., USA) was cultivated in the allantoic cavity of the 9-11 day old chicken embryos for 48 hours at 36° C. MDCK cell line (ATCC CLL-34) from the collection of the Research Institute of Influenza RF MPHSD (RII) was used. Cells were cultured in the Minimum Essential Medium (MEM) in 24 and 96-well plates until the formation of a cell monolayer and then used for the further experiments. For cell transfection, siRNA duplexes (Table 5)-polycation complexes were prepared at the ratio N:P=3:1. To investigate transfection efficiency with the fluorescently labeled siRNA, the cells were incubated with the complexes for 24 hours. Complexes against the cellular genes siRNAc were also incubated with the cells for 24 hours. When studying the antiviral activity of siRNA as a prophylactic or therapeutic, the cells were incubated with the complexes for 1 hour and 24 hours respectively. Transfection of MDCK cells with Lipofectamine was performed in accordance with manufacturer recommendations.
To study antiviral activity of siRNA cells, MDCK cells were inoculated with the virus dose of 0.1 TCID50 (50% of tissue culture infective dose) per cell. After 1-hour incubation, unattached virus was removed by washing with PBS. Then, siRNA-polycation complexes or siRNA complexes with lipofectamine were mixed with virus cultivation medium and the composed medium was added to each well with infected MDCK cells. Virus cultivation medium consisted of MEM containing 0.5% albumin (Calbiochem), 1 μl/ml trypsin (Fluka No293610), and 16 mM HEPES pH 7. 4 (Sigma NoH4034-500G) and 20 μg/ml ciprofloxacin. Plates were incubated in CO2 incubator at 37° C. and 5% CO2, and the culture fluid was collected after 24 hours incubation. To determine the virus infectious titers, ten-fold serial dilutions (10-1-10-6) were prepared from the samples of the culture fluid with the culture medium. MDCK cells were infected with diluted samples and incubated for 48 hours. After that, virus replication was measured by hemagglutination in the plates. The hemagglutination reaction was performed with 1% chicken red blood cells (RBC). Virus titer was considered as reciprocal to the final dilution of the inoculumable to cause cytopathogenic effect in 50% of cells and was expressed as 50% infecting doses. The antiviral activity of the studied complexes was determined by their ability to exhibit a lower infectious viral titer in comparison with the control values (
Through two-two pairing, we are able to identify a pair of siRNA duplexes with further improved antiviral activity in H1N1 challenged MDCK cell culture. The combination of #89/#103 siRNA pair demonstrated stronger anti-influenza activity than either single siRNA at the same concentration (
Effects of combining 2 siRNAs (one against M2 and the other against PA) on antiviral effects against Influenza strains H1N1 (left), H3N2 (middle) and H5N2 (right). siRNAs were administered in PAA at various concentrations ranging between 5 nM and 40 nM. The bar at the rear right of each figure represents the viral titer measured in the presence of the vehicle alone. As the concentration of each siRNA is increased we see a dose dependent decrease in viral titer against each viral strain. Notice that in each case a combination of 20 nM of each of the siRNAs was more potent than 40 nM of either siRNA alone (front left bar in each figure).
We tested the antiviral activity of combined #89/#103 siRNA pair packaged with PAA through I.P. administration of siRNAs against M2 And PA genes, we observed a dose-dependent inhibition of lethality in mice exposed to H1N1. The PAA packaged siRNAs were administered through I.P. injection to mice exposed to a mouse-adpated H1N1 strain (A/California/07/09 (H1N1)pdm09). In placebo treated animals˜50% died 8 days after exposure. Administration of 10 mg/Kg of the combination siRNAs 24 h post exposure to the virus resulted in >80% survival after 11 days and this value was equivalent to the effect seen using 25 mg/Kg of Tamiflu (
Between late March and early May of 2013, a newly identified form of influenza, H7N9, was responsible for an outbreak in China that produced respiratory disease in patients with with more than 30% mortality. We therefore quickly screened the siRNA duplexes that have been tested active against H1N1 using H7N9 challenged MDCK cell culture. The bioinformatics search identified 100% homology among 7 different strains of H7N9 reported in China (Table 6).
The siRNA therapeutics we used with PEG-PEI mediated intranasal instillation into the H5N1 viral challenged mice, using a regimen of 100 ug per dose, twice a day for two days, started 24 hours post viral challenge, exhibited 60% survival rate of treated mice, compared to the results of 40% for Zanamivir treatment, 0% for Ribavirin and other siRNA attempts.
Therefore, both siRNA #103 (specific to PA gene) and siRNA#105 (specific to NP gene) have homology to both H1N1 and H7N9 viral sequences. Where #105 has been validated with either H1N1 or H7N9 challenged MDCK cells resulted in potent anti-influenza activity with IC50<7 nM. We hypothesize that a combination of the siRNA #103/#105 pair will be very active against both H1N1 and H7N9.
All publications, including issued patents and published patent applications, and all database entries identified by url addresses or accession numbers are incorporated herein by reference in their entirety.
Although this invention has been described in relation to certain embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein may be varied considerably without departing from the basic principles of the invention.
This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/669,108, filed Jul. 8, 2012, which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/049505 | 7/7/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61669108 | Jul 2012 | US |
