Patent Application
20090137501
This invention relates to resistance genes, and to uses thereof. More particularly, the present invention relates to genes involved in immune resistance to infection.
It is known in the art that it is possible to diagnose a predisposition to certain diseases with the use of marker genes. For example, oncogenes or tumour suppressor genes are widely regarded as being indicative of a susceptibility to certain cancers, especially in view of the associations between mutated oncogenes and deleted tumour suppressor genes and certain cancers. Additionally, genes have been identified, such as the BRCA genes, which are taken to be predictive of a greater risk of contracting cancers, for example breast cancers. It is also known that some individuals are highly susceptible or resistant to infection, especially viral infection. Prediction of disease susceptibility is beneficial for those possessing predisposing genes in order to avoid unnecessary contacts with known aetiological agents, chemicals, or viruses, and to take known and developing preventative means. It is also useful in the design of a vaccine against viral disease or for gene therapy. In addition, prediction of the speed of disease progression may allow opportunity for individualized, more efficient management of therapy.
Additionally, the development of an effective vaccine against major viral diseases such as human immunodeficiency virus (HIV) infection is a pressing matter with global socioeconomic ramifications. HIV is the causative agent of acquired immunodeficiency syndrome (AIDS). One of the keys to the development of such a vaccine is the understanding of the mechanisms of natural resistance against HIV infection. In this regard, the absence of clinical progression in some HIV-1-infected individuals and the lack of detectable HIV-1 genome despite multiple and repeated exposure to this virus in some apparently resistant groups of people are two notable phenomena when considering the development of preventative and therapeutic means to HIV infection. Several host genes have been associated with possible resistance against HIV infection and with either delayed or accelerated development of AIDS after HIV seroconversion [reviewed in 1]. These host genes include genes encoding chemokine receptors and cytokines, killer immunoglobulin-like receptors (KIRs) that serve as natural killer cell receptors, and those within the major histocompatibility complex (MHC) [1-11].
Some of the individuals who are naturally resistant possess a mutated HIV co-receptor gene known as CCR5Δ32 [1-5] However, this mutation is recessive and the homozygosity that confers resistance against HIV entry into cells is only rarely found. Thus, the above mutation cannot account for the majority of individuals who show spontaneous resistance against HIV infection. Among existing human clusters showing natural resistance against HIV infection, there is a distinct group of people known as HIV-exposed sero-negatives (ESNs) or as HIV-1-exposed but uninfected individuals (EUIs) who have evidence of multiple and repeated exposure to HIV, but nevertheless possess no serum IgG antibodies reactive to HIV [12, 13]. EUIs show strong HIV-1 antigen-specific T-lymphocyte responses and HIV-1-reactive mucosal IgA production despite the absence of detectable plasma HIV-1 RNA and HIV-1 cDNA from peripheral blood mononuclear cells (PBMCs) [14-16]. Detection of HIV antigen-specific T-lymphocyte responses and of HIV-reactive IgA antibodies in urethral or vaginal secretions from these ESNs/EUIs indicate that they have been exposed to HIV but the exposure has not resulted in infection [12-17]. Attempts to associate the ESN/EUI status with the previously reported genetic polymorphisms have so far been unsuccessful [10, 14]. Demonstration of HIV-1-neutralizing activity exerted by the mucosal IgA isolated from EUIs [17-19] has suggested that rapid production and class switching of HIV-1-neutralizing antibodies might contribute to the presumable immune resistance against HIV infection. Protective roles of neutralizing antibodies against HIV-1-related simian immunodeficiency virus (SIV) or pathogenic chimeras between HIV-1 and SIV have also been demonstrated by passive transfer and vaccine-induced active immunization experiments in non-human primates [20-23]. However, the degree of protection afforded by the generation of various HIV-specific immune responses in humans has not been established and neither immunological nor genetic correlates of presumable protection against HIV infection are currently known.
It was recently shown that APOBEC3G, a cellular enzyme belonging to the apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) family cytidine deaminases, has a broad antiretroviral activity [24-27]. Thus, after the penetration of HIV into target cells and the initiation of reverse transcription of viral genomic RNA into DNA, APOBEC3G induces the conversion of cytosine to uracil in minus strand cDNA leading to a failure of reverse transcriptase and to a very high number of G-to-A mutation in the integrated proviral genome that greatly reduces viral fitness [24, 25, 28]. HIV Vif protein counteracts the activity of APOBEC3G by forming a complex with it in the cytoplasm and by impeding its packaging into virions, thus preventing editing mutations upon entry of the newly generated viral particles into target cells [29, 30]. The interaction with Vif stimulates APOBEC3G degradation by ubiquitine-proteasome pathway [30-33] and increases viral replication. This explains the biological properties of Vif which are to facilitate HIV replication and enhance the infectivity of progeny virions 10- to 100-fold. The importance of the Vif-APOBEC interplay in determining HIV infectiousness is further strengthened by the observation that cell lines that are permissive to the replication of vif-deleted HIV do not express APOBEC3G [29, 34].
Even more recently, a second DNA-editing enzyme, APOBEC3F, was found to be involved in the resistance of human cells against HIV infection [35-37]. APOBEC3F is also packaged into HIV virions and inhibits their infectivity by specifically binding to the Vif protein. APOBEC3G and APOBEC3F are co-expressed in non-permissive human cells where they form heterodimers [37]. Importantly, the antiviral activity of APOBEC3F is partially resistant to Vif, resulting in a more pronounced 5′GA-to-5′AA bias, and thus in a stronger impairment of HIV replication [38]. However, there is no known direct effect of APOBEC3G and APOBEC3F on immune cells, and the possible differences in the expression of these DNA mutator proteins have not been associated with the stronger and/or earlier immune responses upon HIV exposure observed in the above ESNs/EUIs.
In a mouse model, resistance to Friend murine leukaemia virus (FV) is controlled by a number of genetic factors, and complex immune responses, including B, T and NK cell responses, are required for efficient protection and survival of the animals. See Table 1 below.
By studying the Rfv3 locus in mice and DNA samples from EUI individuals, with their informed consent, the inventors found that EUIs possess distinct rare alleles at microsatellite loci within a region of human chromosome that is syntenic to the area of mouse chromosome 15 containing the retrovirus resistance gene, Rfv3. In International Patent Application No WO 2004/035825 the inventors described specific genotypes or polymorphisms which are associated with resistance to HIV infection in the ESNs/EUIs in European individuals (in Italy).
The present inventors have now identified the genes and their regulatory elements implicated in naturally acquired immune resistance against the establishment of HIV infection known as the ESN or EUI status. The results described herein suggest that genes and their regulatory elements now identified by the inventors represent the genetic factor(s) that allow some people to mount anti-HIV immune responses upon exposure to HIV. It is likely that the combination of some of these factors is linked to the fact that some individuals take much longer to progress to AIDS as opposed to the majority.
Hence, the present inventors have identified a number of genes and their regulatory elements implicated in immune resistance to infection, particularly viral infection and more particularly HIV infection.
The identification of these genes and their regulatory elements involved in immune resistance to infection enables a series of novel modes of treatment as well as vaccine strategies and modes of diagnosis.
The present inventors have already determined that one or more genes located in the region of human chromosome 22 that is syntenic to the region of mouse chromosome 15 between the loci D15Mit68 and D15Mit107 and their gene products (a polypeptide encoded by such gene, or a fragment of said polypeptide), is usable in the treatment or prevention of infection.
In this respect, it has been shown that the gene is a homologue or orthologue of one of the mouse genes listed in Table 2 which shows a significantly different level of expression in A/vySn strain of mice that fail to mount rapid antibody responses to FV infection compared to (B10.A×A/WySn)F1 mice that produce FV-neutralizing antibodies by 14 days after infection. The present inventors have now determined that the human gene is a homologue or orthologue of a mouse gene selected from the list in Table 2 inclusively but not exclusively including Q8CCA5 (APOL3), 2600013G09Rik (RABL4), Rac2, Card10, D230019K20Rik (KA93_Human), Q9D6D6 (Tob2), 2610019103Rik (C22orf18) and Tnfrsf13c (Baffr).
Homologous and orthologous genes are genes from different species which have similar nucleotide sequences. Sequence similarity may be readily determined using computer programs known in the art such as those in the Wisconsin Package™ (Accelrys Inc., CA, USA). Where the observed sequence similarity is hypothesized to be because the genes share a common evolutionary origin, the genes are termed “homologous”, however this term is also often used loosely to indicate merely that gene sequences are very similar. The term “orthologous” is also applied to genes from different species that are hypothesized to have evolved from a common ancestor.
Accordingly, in a first aspect, this invention provides an isolated nucleic acid encoding a gene which is a homologue or orthologue of a mouse gene selected from the list in table 2 particularly, but not exclusively, containing Q8CCA5 (APOL3), 2600013G09Rik (RABL4), Rac2, Card10, D230019K20Rik (KA93_Human), Q9D6D6 (Tob2), 2610019103Rik (C22orf18) and Tnfrsf13c (Baffr).
In addition, the gene is preferably one of the following human genes which show significantly different expression levels between ESNs/EUIs and HIV-1-infected individuals upon in vitro stimulation of their PBMCs with HIV-1 antigens, or at which locus significant genetic differences are demonstrated between ESNs and HIV-1-infected individuals as groups, such as, for example, the genes Rac2, PSCD4, Card10, and Grap2. The most preferred of these genes is Rac2 or PSCD4.
The genes recited above (Q8CCA5 or APOL3, 2600013G09Rik or RABL4, Rac2, PSCD4, Card10, D230019K20Rik or KA93_Human, Grap2, Q9D6D6 or Tob2, 2610019103Rik or C22orf18, and Tnfrsf13c or Baffr) all encode proteins or polypeptides. One or more of genes and the proteins or polypeptides encoded by these genes (and their secondary or tertiary derivatives) must be involved in the observed immune resistance to infection.
Accordingly, the present invention also provides the use of the protein or polypeptide encoded by one or more of these genes in the treatment or prophylaxis of infection, particularly viral infection, and for their use in a person who has been diagnosed as suffering from an infection or who has been identified as having a predisposition to infection may be beneficial in the treatment or prevention of infection, respectively. Preferably, the infection is a viral infection, most preferably a retroviral infection and especially HIV infection.
Advantageously, a mixture of polypeptides according to the invention, i.e. polypeptides encoded by different genes located in the region of human chromosome 22 that is syntenic to the region of mouse chromosome 15 between the loci D15Mit68 and D15Mit107, or fragments thereof, may be used in the treatment or prevention of infection. Such a mixture is expected to be more effective in treating or preventing infection than one polypeptide on its own.
Additionally, the glycosylation, sulphonation, phosphorylation, acetylation or other addition or substitution products, homologues, splice variants, transcription variants or products derivable from the nucleonic acid sequence of the genes may be used for this purpose and hence are considered to constitute part of the present invention.
Polypeptides according to the invention are coded by genes associated with naturally occurring immune resistance against establishment of HIV infection. Hence, any molecule that mimics or facilitates the action of the polypeptides according to the invention can potentially be used as a drug to enhance a vaccine regimen or to stimulate antibody production in already infected people. Such molecules are therefore part of the present invention.
For example, since Rac2 is known to be involved in T-cell activation, and as such it is possible to make a drug which mimics or facilitates the action of the expression product of this gene in T cells, or it is possible to target the downstream signals to activate T cells. The gene Card10 and its expression product can be used in the same way.
Furthermore, polypeptides according to the invention, and drugs that mimic or facilitate their action, may be used to induce or promote stronger immunoglobulin (Ig) response in a subject and to induce or promote class switching by using in combination with a vaccine regimen.
The present inventors have already determined that one or more genes located in the region of human chromosome 22 that is syntenic to the region of mouse chromosome 15 between the loci D15Mit68 and D15Mit107, or their encoded polypeptide products or fragments of said polypeptides, can be used in the manufacture of a medicament for the treatment or prevention of infection.
It has now been found that a surprising beneficial effect is found when the genes are selected inclusively but not exclusively from the following group: Q8CCA5 or APOL3, 2600013G09Rik or RABL4, Rac2, PSCD4, Card10, D230019K20Rik or KA93_Human, Grap2, Q9D6D6 or Tob2, 2610019103Rik or C22orf18, and Tnfrsf13c or Baffr and their polypeptides derived from the said genes are used.
Preferably the medicament comprising one or more of the gene products from the above genes is used for the treatment or prevention of a viral infection, such as an infection caused by a retrovirus, for example an oncovirus, a lentivirus, or a spumavirus. HTLV and BLV (bovine leukaemia virus) are examples of oncoviruses which cause leukaemia. HIV and SIV are examples of lentiviruses which cause inflammatory and wasting disease. Human spumavirus is an example of a spumavirus. Most preferably the medicament is for the treatment or prevention of HIV infection.
Where the medicament is for the prevention or prophylaxis of infection, the medicament is suitably a vaccine.
In a third aspect, the invention also provides vaccine comprising one or more polypeptides encoded by the genes or one or more isolated nucleic acid selected particularly, but not exclusively, from the following group: Q8CCA5 or APOL3, 2600013G09Rik or RABL4, Rac2, PSCD4, Card10, D230019K20Rik or KA93_Human, Grap2, Q9D6D6 or Tob2, 2610019103Rik or C22orf18, and Tnfrsf13c or Baffr and a pharmaceutically acceptable carrier. Suitable pharmaceutically acceptable carriers are well known in the art.
In a fourth aspect, the invention provides a method of treating or preventing infection comprising administering a pharmaceutically effective amount of one or more polypeptides or fragments of said polypeptides encoded by genes selected particularly but not exclusively from the following group: Q8CCA5 or APOL3, 2600013G09Rik or RABL4, Rac2, PSCD4, Card10, D230019K20Rik or KA93_Human, Grap2, Q9D6D6 or Tob2, 2610019103Rik or C22orf18, and Tnfrsf13c or Baffr.
As noted in the introduction, the present inventors have previously described microsatellite markers which appear to be associated with immune resistance to HIV infection in a group of ESNs and mapped these to a region of chromosome 22 that is syntenic to the area of mouse chromosome 15 containing a retrovirus resistance gene Rfv3 (molecular identity unknown). The inventors have now identified the genes in this same region which are differentially expressed in mice that are capable or incapable of producing virus-neutralizing antibodies upon FV infection and this provides the first indication of the molecular identities responsible for early immune resistance to virus infection.
Further, the present inventors have now demonstrated that some genes in the syntenic region of human chromosome 22 are expressed higher in PBMCs of ESNs than in those of HIV-1-infected individuals upon stimulation with HIV-1 antigens. Moreover, these differences are associated with base changes in the nucleic acid sequence of their regulatory elements. These findings enable the manipulation of the mechanism of immune resistance to prevent or treat infection and for the determination of products which can be used for this purpose. This may be done at the level of the gene product, as outlined above, at the level of the regulation of gene expression as exemplified below, or at the level of the gene itself, by gene therapy.
Hence, in a fifth aspect, the invention provides a method of treating or preventing infection comprising augmenting or inhibiting expression of one or more genes located in the region of human chromosome 22 that is syntenic to the region of mouse chromosome 15 between the loci D15Mit68 and D15Mit107.
The preferred genes are selected from the list consisting inclusively but not exclusively from the following: Q8CCA5 or APOL3, 2600013G09Rik or RABL4. Rac2, PSCD4, Card10, D230019K20Rik or KA93_Human, Grap2, Q9D6D6 or Tob2, 2610019103Rik or C22orf18, and Tnfrsf13c or Baffr.
If a gene as described herein shows high expression, for example, in (B10.A×A/WySN)F1 mice relative to expression in A/WySn mice, or in humans a gene shows high expression in ESNs/EUIs relative to HIV-1-infected individuals, it may be considered as gene associated with resistance or a “resistance gene”. Conversely, if a gene as described herein shows high expression in A/WySn mice relative to expression in (B10.A×A WySn)F1 mice, or a gene shows high expression in HIV-1-infected individuals relative to ESNs/EUIs, it may be considered as a gene associated with susceptibility or a “susceptibility gene”. In direct gene therapy or a therapy based on the regulation of gene expression to prevent or treat viral infection, it is desirable to restore or augment expression of resistance genes but inhibit or prevent expression of susceptibility genes. It is a feature of the present invention that target genes for such therapy have been identified and that gene therapy products can be designed for these targets.
Host genetic factors influencing viral entry and replication and immune responses against retroviral infections have been extensively studied by using mouse models [38-41]. Friend mouse leukaemia virus complex (FV) is composed of replication-competent Friend mouse leukaemia helper virus (F-MuLV) and defective spleen focus-forming virus. FV induces rapid proliferation of infected erythroid progenitor cells upon inoculation into immunocompetent adult mice of susceptible strains. Persistent infection of FV associated with severe immunosuppression ultimately causes the emergence of mono- or oligoclonal expansion of leukaemia cells due to an insertional activation of a cellular transcription factor or disruption of a tumour suppressor gene. Host gene loci, Fv1, Fv2, and Fv4, that directly control the viral entry and replication in the target cells have been identified [42-45]. However, even when the host animals share the same susceptible genotypes at the above loci, the rate of disease development and progression still changes drastically depending on host genotypes at several loci that influence immune responses to FV antigens [40]. Two major histocompatibility complex (MHC) class II loci directly restrict the T helper cell recognition of the viral envelope antigen [46, 47], while a class I locus influences the production of cytokines from viral antigen-specific T-cells [48]. Another locus mapped in the MHC class Ib region may affect natural killer cell functions [49, 50]. Yet another host locus that has been mapped in chromosome 15, and thus is irrelevant to MHC, strongly influences the persistence of viraemia after FV infection [40, 51-53]. Genotypes at the same non-MHC locus also influence the production of cytotoxic antibodies that modulate the expression of viral antigens on infected cell surfaces [54]. However, possible relationship between the persistence of viraemia and production of virus-neutralizing antibodies has not been directly examined. The inventors have performed linkage analyses on a mouse locus that is postulated to be connected with immune activation that may be responsible for resistance of the various mouse strains to FV and linked to their ability to respond to FV infection with virus-neutralizing antibodies. An extension of this mouse study to syntenic regions in ESN/EUI humans unexpectedly led to a demonstration of human chromosomal markers that are associated with strong immune responses to HIV-1 in HIV-uninfected individuals, as described in International patent publication no. WO 2004/035825.
The gene Rfv3 was originally defined as a single autosomal gene that determines whether mice infected with Friend leukaemia retrovirus recovered from viraemia by 30 to 60 days after infection or not [40, 51]. This gene has been mapped to mouse chromosome 15 [52, 53], although its molecular identity is still unknown. Immune resistance against Friend retrovirus infection is also influenced by genes of mouse major histocompatibility complex (MHC), H2, which control T-lymphocyte responses to the viral envelope and gag antigens [40, 46, 49 and 55]. When tested in congenic strains, early production of virus-neutralizing antibodies was observed in mice that possessed either a resistant allele (Rfv3r) at the Rfv3 locus or a responder haplotype (H2b) at mouse MHC, suggesting that Rfv3 and H2 may effect the immune system through a common pathway. Moreover, mice possessing both an Rfv3r allele and an H2b haplotype showed even higher levels of virus-neutralizing antibodies and a higher frequency of IgM to IgG class switching in comparison with the H2a/b mice lacking an Rfv3r, further indicating that Rfv3, in cooperation with H2, might regulate a T-helper cell function. This was of potential relevance to why HIV-specific IgA production, in the apparent absence of IgG, can be detected in ESNs, especially because HIV-1 antigen-specific T helper cell responsiveness and patterns of cytokine production from T cells may differ between ESN and HIV-infected individuals [14, 16, 19].
The Rfv3 locus had been mapped in mouse chromosome 15 between the D15Mit1 and D15Mit118 loci (
The microarray chips were used to analyse levels of expression of genes located within the above region of chromosome 15 in Rfv3s's mice (that have median survival time of 40 days post infection with 15 spleen focus-forming units of Friend virus and which also lack the production of F-MuLV-neutralizing antibodies at post inoculation days (PID) 14 and 20) and Rfv3r/s mice (that have median survival time of 70 days post infection with 15 spleen focus-forming units of Friend virus and produce, F-MuLV-neutralizing antibodies at PID 20) following inoculation with Friend virus complex, as described in the example.
Overall levels of expression and their differences between Rfv3s/s A/WySn and Rfv3r/s (B10.A×A/WySn)F1 mice of genes located within the above chromosome 15 region were largest at PID 9. An example of the resultant microarray images is shown in
Genes of interest revealed by the present study therefore include inclusively but not exclusively all those genes listed in Table 2 which fulfil the above criteria.
Genes selected as being of particular interest include:
As described, the present inventors have previously mapped genes associated with the HIV-exposed but uninfected status in a segment of human chromosome 22 that is linked with microsatellite markers D22S277, D22S272, and D22S423 (International patent publication no. WO 2004/035825) [61]. Further, a disruption of linkage disequilibrium across the chromosome 22 loci at the D22S276 locus, which is telomeric to the above three loci, was observed only in the group of HIV-exposed but uninfected individuals but not in the groups of HIV-infected or healthy control individuals, indicating that a possible chromosomal recombination and/or mutation might have taken place only in the ancestors of the ESN/EUI individuals at the area surrounding this locus. The above result on the disruption of linkage disequilibrium at the D22S276 locus indicates that the putative gene that confers immune resistance against the establishment of HIV infection may exist in the region of human chromosome 22 centromeric to the D22S276 locus.
To ensure that the current patient population used to generate current data was the same as the population used in [6]), the present inventors genotyped and compared the profiles carrying out a similar analysis at allele 229 of the D22S423 locus. The number of enrollees possessing the allele 229 at the D22S423 locus was significantly higher among the ESN than among the HIV-infected individuals (28/68 of ESNs tested were genotype 229 at D22S423 versus only 11/70 in HIV+ group); P=0.0012 by Fisher).
To further narrow down the chromosomal region where the putative immune resistance gene is located, we genotyped 74 HIV-exposed but uninfected and 77 HIV-infected individuals enrolled from the same geographical region at loci of single nucleotide polymorphism (SNPs) SNP loci were selected based upon their location on chromosome 22 between the APOL3 and A4GALT loci to cover the above candidate region. The segment between the APOL3 and A4GALT includes the region syntenic to the segment of mouse chromosome 15 that harbors the host resistance gene, Rfv3 [58]. In addition, two other criteria for the selection of SNP loci to be genotyped were: 1/reported frequencies of different alleles among Caucasians (SNP Browser ver. 3.0, Applied Biosystems, Foster City, Calif.) with each low-frequency allele expected to be found in roughly 20 to 40% of the tested individuals, and 2/unskewed distribution of the SNP loci within the above chromosomal segment.
Table 3 and
Locations of these genetic loci are shown in
The numbers of individuals possessing the indicated allele 1 are significantly higher among the ESNs under a dominant gene hypothesis at the Card10, CDC42EP1, and GRAP2 loci, and the most highly significant difference between the ESN and HIV-infected individuals was observed at the CDC42EP1 locus (P=0.0043), as described in the Example 3 below.
In addition to the genotyping at the above SNP loci, expression levels of all the genes located in the above candidate region was compared between the HIV-exposed but uninfected and HIV-infected individuals. To detect the possible changes in the expression of host genes that are associated with observed immune resistance against HIV infection without being biased by host factors other than HIV resistance and environmental factors, we stimulated peripheral blood mononuclear cells prepared from each examined individuals with the mixture of promiscuous HIV-1 antigens, and prepared total RNA before and after the antigenic stimulation. Changes in gene expression were then compared between peripheral blood mononuclear cells of each single individual before and after the antigenic stimulation at 1 hour and at 6 hours. As the expression of the tested genes were not significantly different between the cells before stimulation and those at 1 hour after the stimulation, all comparisons of expression in response to antigenic stimulation was carried out at 1 hour and at 6 hours post stimulation. Of the genes investigated, two genes RAC2 and Q9H7Q0 (PSCD4) showed an increase in expression levels at 6 hours after the stimulation in ESNs but not in HIV+ population. All other tested genes did NOT show a significant increase. The levels of increase found are about 20%, and are consistent, as shown in
Microarray analyses were performed as described for the expression of mouse genes above.
Soon after the culture for the antigenic stimulation, PBMCs were treated with RNAlater (Ambion, Inc.). Total RNA was extracted from PBMCs by using the TRIzol reagent (Invitrogen Life Technologies, Carlsbad, Calif.) according to the manufacturer's instructions. Complementary DNA (CDNA) was produced from total RNA in the presence of RNase inhibitor (Promega Corporation, Madison, Wis.) by using the T7-oligo (dT) 24 primer (5′-GCCCAGTGAATTGTAATACGACTCACTATAGGGAGG CGGTTTTTTTTTTT TTTTTTTTTTTTT-3′, PROLIGO Japan, Kyoto, Japan) and SuperScript II reverse transcriptase (Invitrogen) according to the manufacturer's instructions. Resultant cDNA was purified with PCR purification kit (QIAGEN, K. K., Tokyo, Japan). Biotinylated cRNA was prepared by using Bio-16-UTP (Enzo Life Sciences, Inc., Farmingdale, N.Y.) and MEGAscript transcription kit (Ambion, Inc., Austin, Tex.), and resultant cRNA was purified by using RNeasy kit (QIAGEN, K. K.).
Accordingly, in a further aspect, the invention provides the identification of two genes, RAC2 and PSCD4 (also known and listed in
The present invention also provides isolated nucleic acids encoding RAC2 and PSCD4 for use in medicine. These nucleic acids are also usable in the preparation of a vaccine for the prophylaxis of infection, such as viral infection and especially HIV infection.
Additionally, the invention provides oligo- or polynucleotides encoded by SEQ Id No: 1 or by SEQ ID No: 2 of
Accordingly, the invention also provides a method of treating or preventing infection, the method comprising administering a pharmaceutically effective amount of one or more chemical compound, synthetic oligonucleotide such as siRNA, or polypeptide binding to nucleic acid as hereinbefore described or functional fragments of said regulatory element of the genes to an individual in need of such treatment.
The invention also includes a method of treating or preventing infection, the method comprising augmenting or inhibiting expression of one or more genes encoding a polypeptide as hereinbefore described in an individual in need of such treatment.
In a further aspect, the invention also provides the use of a polypeptide as hereinbefore described or antibody raised thereto in a method of screening of compounds for functional homologues of said polypeptides.
The present invention also provides a method of determining disease progression by being able to identify the mechanism and pathway of viral infection and its resistance. Thus the invention also provides a method and compounds which can be used to modify the disease-progression as well as to determine an appropriate course of treatment in an individual.
Embodiments of the invention will now be described, by way of example only, with reference to the following examples as illustrated by the appended drawings of which:—
Rfv3s/s A/WySn mice that lack the production of F-MuLV-neutralizing antibodies at post-inoculation days (PID) 14 and 20 and Rfv3r/s (B10.A×A/WySn)F1 mice that produce F-MuLV-neutralizing antibodies by PID 14 were inoculated with 150 spleen focus-forming units (SFFU) of Friend virus complex (FV), and the infected mice were killed at PIDs 5, 9, and 13. Control mice were not inoculated with FV. Immediately after the mice were killed, the spleen was removed from each mouse and frozen by pressing between two blocks of dry ice. Total RNA was extracted by using the TRIzol reagent (Invitrogen Life Technologies, Carlsbad, Calif.) according to the manufacturer's instructions. Complementary DNA (cDNA) was produced from total RNA in the presence of RNase inhibitor (Promega Corporation, Madison, Wis.) by using the T7-oligo (dT) 24 primer (5′-GCCCAGTGMTTGTAATACGACTCACTATAGGGAGGCGGTTTTTTTTTTT TTTTTTTTTTTTT-3′, PROLIGO Japan, Kyoto, Japan) and SuperScript II reverse transcriptase (Invitrogen) according to the manufacturer's instructions. Resultant cDNA was purified with PCR purification kit (QIAGEN, K. K., Tokyo, Japan). Biotinylated cRNA was prepared by using Bio-16-UTP (Enzo Life Sciences, Inc., Farmingdale, N.Y.) and MEGAscript transcription kit (Ambion, Inc., Austin, Tex.), and resultant cRNA was purified by using RNeasy kit (QIAGEN, K. K.).
The Rfv3 locus had been mapped in mouse chromosome 15 between the D15Mit68 and D15Mit107 loci (
Overall levels of expression and their differences between A/WySn and (B10.A×A/WySn) F1 mice of genes located within the above chromosome 15 region were largest at PID 9. An example of the resultant microarray images is shown in
Based on the previous identification of genetic markers associated with early immune resistance against repeated exposure to HIV-1 located in the region of human chromosome 22 that is syntenic to mouse chromosome 15 where the Rfv3 gene was mapped (International patent publication no. WO 2003/035825;
In addition to the above analyses on the expression of mouse genes in FV-infected, resistant and susceptible animals, the inventors have also generated HUMAN microarray data.
Expression levels of all the genes located in the above candidate region was compared between the HIV-exposed but uninfected and HIV-infected individuals. Our previous analyses have shown that peripheral blood mononuclear cells prepared from HIV-exposed but uninfected individuals produce significantly larger amount of IFN-γ than those from HIV-exposed individuals upon stimulation with a mixture of HIV-1 Env and Gag antigens [14, 16, 57, 58, 61] Patterns of gene expression between individuals may change based on their age, sex, time-point of sample collection in a year or even in a day, and environmental factors including infectious agents, allergens, and food. To detect the possible changes in the expression of host genes that are associated with observed immune resistance against HIV infection without being biased by the above host and environmental factors, we stimulated peripheral blood mononuclear cells prepared from each examined individuals with the mixture of promiscuous HIV-1 antigens (a pool of six synthetic peptides from gag of HIV-1 at 2.5 μM final concentration plus a pool of five synthetic peptides from the gp160 envelope of HIV-1 at 2.5 μM final concentration) as described previously [14, 61], and prepared total RNA before and after the antigenic stimulation as described for Example 1. Changes in gene expression were then compared between peripheral blood mononuclear cells of each single individual before and after the antigenic stimulation. Microarray analyses were performed as described for the expression of mouse genes in Example 1 using CostomArray 12K (CombiMatrix Corporation, Mukilteo, Wash.). Two to 10 specific probes were designed for each of the genes enlisted in
The data shown in
In
Among all the genes tested for their expression, two genes, Rac2 and PSCD4 (also known and listed in
Ratios of expression levels at 1 h and 6 h after the antigenic stimulation were calculated for the probes with which the expression level at 1 h was >250. Expression levels <250 suggested that the probe used reacted poorly. Averages of the 1 h/6 h ratios in ESNs were consistently higher that in HIV+individuals as seen in
In addition to gene SNP analysis real time PCR was used to confirm the increased expression in Rac2 and PSCD4 in response to HIV specific antigen stimulation.
We have shown that Rac2 and CSCD4 are induced only in PBMCs of ESNs but not in those of HIV-1-infected individuals upon HIV-1 antigenic stimulation. Rac2 is a member of the RAS superfamily of small GTP-binding proteins, and is selectively expressed in type 1 helper T lymphocytes (Th1) in mice Rac2 induces the IFN-γ promoter through cooperative interaction of the NF-κB and p38 MAP kinase pathways. Since we have shown that T cells from ESN individuals produce higher levels of IFN-γ than those from HIV-infected or healthy control individuals upon stimulation with HIV-1 antigens (mentioned above), the observed higher expression of Rac2 upon HIV antigenic stimulation is likely to explain the higher levels of IFN-γ production in ESN individuals. PSCD4 may also be directly involved in the immune resistance of ESN individuals, because this gene is 69% identical to the PSCD1, which is know to be expressed high in natural killer and T lymphocytes [59]
SNPs genotyping analyses also indicated that genes located near the Rac2 and PSCD4 are involved in the immune resistance phenotype of the ESN individuals. As shown in Table 4, numbers of individuals possessing the indicated allele 1 are significantly higher among the ESNs under a dominant gene hypothesis at the Card10, CDC42EP1, and GRAP2 loci, and the most highly significant difference between the ESN and HIV-infected individuals was observed at the CDC42EP1 locus (P=0.0043). In Table 4 The numbers of individuals possessing and not possessing allele 1 between the ESN and HIV-infected groups were compared by Fisher's exact probability test. 1=homozygous for allele 1; ½=heterozygous; and 2=, homozygous for allele 2 (alleles as listed in Table 3).
2001 [58] indicated that genotypes at the SNP loci throughout the chromosome 22 region between the APOL3 and A4GALT are highly linked in the ESN individuals but not in the HIV-infected individuals. See
Since the SNP loci at which the numbers of individuals possessing the indicated allele 1 are significantly different between the ESN and HIV-infected groups are physically close to the two genes, Rac2 and PSCD4, whose expression levels after the HIV antigenic stimulation are higher in the ESN individuals (see
Gene expressions are controlled by promoter and enhancer sequences, and these controlling elements, unlike non-functional portions of a chromosome, are relatively conserved in their sequences between different species. In the case of our analyses, Rac2 and CSCD4 that are located next to each other on chromosome 22 but are in opposite translational directions (as shown in
As shown in
Thus, genomic sequences of these two regions were determined by using the PCR primers shown in
Frequencies of individuals possessing the each allele were compared between the ESN and HIV-infected groups. At the region 2, 10 out of the 22 ESN individuals possessed the T to G SNP indicated above, while only 2 out of the 15 HIV-infected individuals tested possessed the G allele at the same locus (λ2=4.2, P=0.04), suggesting that these SNPs are likely to be associated with the observed higher expression of Rac2 and PSCD4 in ESNs.
All the results shown here indicate that 1) genetic polymorphisms in the Rac2-PSCD4-Card10-CDC42EP1 region of human chromosome 22 is associated with HIV-exposed but uninfected status, 2) Rac2 and PSCD4 that are functionally associated with T cell activation and at least the former has been associated with IFN-γ production from T helper cells, are expressed higher in the ESN than HIV-infected individuals after the stimulation of peripheral blood mononuclear cells with HIV-1 antigens, and 3) a T to G polymorphism in the putative enhancer region between the Rac2 and PSCD4 genes are apparently highly accumulated in the ESN individuals.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0428301.6 | Dec 2004 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2005/005078 | 12/28/2005 | WO | 00 | 10/17/2008 |
