Patent Application
20150252332
1. Field of the Invention
The present disclosure relates to hybrid virus. Specifically, the present disclosure relates to novel Autographa californica multiple nucleopolyhedrovirus (AcMNPV) based hybrid baculovirus capable of infecting at least two different hosts.
2. Description of Related Art
The baculoviruses have been divided into four genera: Alphabaculovirus (nucleopolyhedroviruses (NPVs) isolated from Lepidoptera), Betabaculoviruses (granuloviruses (GV) isolated form Lepidoptera), Gammabaculoviruses (NPVs isolated from hymenoptera) and Deltabaculoviruses (NPVs isolated from Dipter). While GVs contain only one nucleocapsid per envelope, NPVs contain either single (SNPV) or multiple (MNPV) nucleocapsids per envelope. The enveloped virions are further occluded in granulin matrix in GVs and polyhedrin in NPVs.
Baculoviruses have a restricted range of hosts that they can infect, which is typically restricted to a limited number of closely related insect species. Since baculoviruses are not harmful to humans, they are considered to be a safe option as biological agents to produce exogenous proteins in baculoviruses—permissive insect cells or larvae. For example, proteins produced by baculoviruses have been used as therapeutic cancer vaccines with several immunologic advantages over proteins derived from mammalian sources (Betting et al., “Enhanced immune stimulation by a therapeutic lymphoma tumor antigen vaccine produced in insect cells involves mannose receptor targeting to antigen presenting cells”. 2009 Vaccine 27 (2): 250-9).
What would be useful for the application of baculoviruses in industry or in agriculture, would be to devise improved baculoviruses with a wider host range that they can infect, hence allowing baculoviruses carrying genes of proteins of interest to be used in mass protein production method; or as bioinsecticides, for a wider range of insect hosts may be reached.
The present disclosure provides a novel AcMNPV based hybrid baculovirus capable of infecting at least two different insect hosts and its uses for producing exogenous proteins such as toxic proteins in these hosts. Accordingly, the novel AcMNPV hybrid baculovirus is useful as a cross host bio-insecticide, for at least two different insect hosts are permissive to this novel AcMNPV hybrid baculovirus.
It is the first object of the present disclosure to provide an Autographa californica multiple nucleopolyhedrovirus (AcMNPV) based hybrid baculovirus capable of infecting at least two different hosts. The AcMNPV based hybrid baculovirus comprises at least Maruca vitrata multiple nucleopolyhedrovirus (MaviMNPV) genes of lef1, orf1629, pk1, CDS1, CDS2, and lef2; and AcMNPV/MaviMNPV-hybrid genes of egt (SEQ ID NO: 1) and orf152 (SEQ ID NO:2).
In some optional embodiments, the AcMNPV based hybrid baculovirus may further include a first nucleic acid encoding a first fluorescent protein, which is any of green fluorescence protein (GFP), enhanced green fluorescence protein (EGFP), Discosoma sp. red fluorescent protein (DsRed), blue fluorescence protein (BFP), enhanced yellow fluorescent proteins (EYFP), Anemonia majano fluorescent protein (amFP), Zoanthusfluorescent protein (zFP), Discosoma fluorescent protein (dsFP), or Clavularia fluorescent protein (cFP).
The AcMNPV based hybrid baculovirus is capable of infecting both AcMNPV-permissive cells or insect larvae, as well as MaviMNPV-permissive cells or insect larvae. According to some examples, the AcMNPV-permissive cells may be any of S. furgiperda IPBL-9 (Sf9), Sf21 or High-five (Hi-5) cells; and the AcMNPV-permissive insect larvae are Trichoplusia ni or Spodoptera frugiperda. In other examples, the MaviMNPV-permissive cells are NTU-MV532 cells; and the MaviMNPV-permissive insect larvae are Maruca Vitrata.
It is the second object of the present disclosure to provide a method of producing an exogenous protein in an insect host. The method includes steps of:
(a) co-transfecting the insect host with the AcMNPV based hybrid baculovirus having a first nucleic acid encoding the first fluorescent protein of the present disclosure, and a transfer vector, wherein the transfer vector comprises in sequence, a promoter, a second nucleic acid operably linked to the promoter and encodes the exogenous protein, an IRES element, and a third nucleic acid operably linked to the IRES element and encodes a second fluorescent protein, wherein the first and second fluorescent proteins emit fluorescence at different wavelengths;
(b) isolating the transfected host that emits fluorescence of the second fluorescent protein;
(c) cultivating the isolated host of step (b); and
(d) harvesting the exogenous protein from the cultivated host of step (c).
According to one preferred embodiment of the present disclosure, the IRES element of the transfer vector is a portion of a Rhopalosiphum padi virus (RhPV) IRES sequence at least 90% identical to SEQ ID NO: 3.
According to preferred embodiments of the present disclosure, the insect host may be AcMNPV-permissive cells or insect larvae, as well as MaviMNPV-permissive cells or insect larvae. According to further examples, the AcMNPV-permissive cells may be any of Sf9, Sf21 or Hi-5 cells; and the AcMNPV-permissive insect larvae are Trichoplusia ni or Spodoptera frugiperda. In other examples, the MaviMNPV-permissive cells are NTU-MV532 cells; and the MaviMNPV-permissive insect larvae are Maruca Vitrata.
According to embodiments of the present disclosure, the exogenous protein may be any of an insect toxic protein, a therapeutic protein or a reporter protein. In one example, the exogenous protein is an insect toxic protein, preferably a protein toxic to Lepidoptera.
In some embodiments of the present disclosure, the first and second fluorescent proteins may be respectively selected from the group consisting of GFP, EGFP, DsRed, BFP, EYFP, amFP, zFP. dsFP, and cFP. In one preferred example, the first and second fluorescent proteins are EGFP and DsRed, respectively.
The details of one or more embodiments of the invention are set forth in the accompanying description below. Other features and advantages of the invention will be apparent from the detail descriptions, and from claims.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description, appended claims and the accompanying drawings, where:
The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.
“Nucleotide sequence”, “polynucleotide” or “nucleic acid” can be used interchangeably and are understood to mean, according to the present disclosure, either a double-stranded DNA, a single-stranded DNA or products of transcription of the said DNAs (e.g., RNA molecules). It should also be understood that the present disclosure does not relate to genomic polynucleotide sequences in their natural environment or natural state. The nucleic acid, polynucleotide, or nucleotide sequences of the invention can be isolated, purified (or partially purified), by separation methods including, but not limited to, ion-exchange chromatography, molecular size exclusion chromatography, or by genetic engineering methods such as amplification, subtractive hybridization, cloning, sub-cloning or chemical synthesis, or combinations of these genetic engineering methods.
The percentage of identity between a subject sequence and a reference standard can be determined by submitting both sequences to a computer analysis with any parameters affecting the outcome of the alignment set to the default position. Optimal alignment of sequences for aligning a comparison window are well known to those skilled in the art and may be conducted by tools such as the homology alignment algorithm, include, but are not limited to GAP, BESTFIT, FASTA, and TFASTA (Accelrys Inc., Burlington, Mass., USA). An “identity fraction” for aligned segments of a test sequence and a reference sequence is the number of identical components which are shared by the two aligned sequences divided by the total number of components in the reference sequence segment, i.e., the entire reference sequence or a smaller defined part of the reference sequence. Percent sequence identity is represented as the identity fraction times 100. The comparison of one or more nucleic acid sequences may be to a full-length nucleic acid sequence or a portion thereof, or to a longer nucleic acid sequence. In some instances, a subject sequence and the reference standard can exhibit the required percent identity without the introduction of gaps into one or both sequences. In many instances, the extent of identity will be evident without computer assistance
The term “operably linked” refers to nucleotide sequences which are linked in the proper reading frame, whether to encode a mRNA transcript of a desired gene product or for a desired regulatory control. Operably linked can also mean that both the first and second nucleic acids are encoded by the same transcription unit. Translation of both such proteins can be regulated by various modes, including cap-dependent translation of the first open-reading-frame (ORF) located furthermost 5′ on the transcription unit. Translation of the second ORF located downstream of the first ORF can be regulated by an IRES. Alternatively, both the first and second genes can be encoded by one ORF, yielding one contiguous polypeptide with both biological activities.
The term “toxic” as used herein meant that the exogenous proteins produced by the method of the present disclosure with the aid of the identified AcMNPV based hybrid baculovirus are lethal to Lepidoptera insects.
The singular forms “a”, “and”, and “the” are used herein to include plural referents unless the context clearly dictates otherwise.
The practices of this invention are hereinafter described in detail with respect to a novel AcMNPV based hybrid baculovirus capable of infecting at least two different insect hosts. This novel AcMNPV based hybrid baculovirus are thus useful as a means for producing exogenous proteins, such as insect toxic proteins, in at least two different insect hosts, hence the novel AcMNPV based hybrid baculovirus of the present disclosure may act as an insecticide capable of reaching a wider range of hosts.
The first objective of the present disclosure is to provide an Autographa californica multiple nucleopolyhedrovirus (AcMNPV) based hybrid baculovirus. The AcMNPV based hybrid baculovirus is capable of infecting at least two different hosts and is characterized in having at least Maruca vitrata multiple nucleopolyhedrovirus (MaviMNPV) genes of lef1, orf1629, pk1, CDS1, CDS2, and lef2; and AcMNPV/MaviMNPV-hybrid genes of egt (SEQ ID NO: 1) and orf152 (SEQ ID NO:2).
The AcMNPV based hybrid baculovirus of the present disclosure is produced by co-infecting a first insect host, such as an AcMNPV-permissive insect cell line or larvae or a MaviMNPV-permissive cell line or larvae, with a recombinant AcMNPV virus capable of expressing a first fluorescent protein, and a recombinant MaviMNPV virus capable of expressing a second fluorescent protein, in which the first and second fluorescent protein emit fluorescence at different wavelengths. In one preferred embodiment, the first host is an AcMNPV-permissive insect cell line Sf21.
Suitable fluorescent protein that may be used in the present disclosure includes, but is not limited to, green fluorescence protein (GFP), enhanced green fluorescence protein (EGFP), Discosoma sp. red fluorescent protein (DsRed), blue fluorescence protein (BFP), enhanced yellow fluorescent proteins (EYFP), Anemonia majano fluorescent protein (amFP), Zoanthus fluorescent protein (zFP), Discosoma fluorescent protein (dsFP), and Clavularia fluorescent protein (cFP). According to one preferred example, the recombinant AcMNPV virus and the recombinant MaviMNPV virus are engineered to express DsRed and EGFP, respectively. Accordingly, the first insect host of Sf21 cells successfully infected with the recombinant AcMNPV virus will emit red fluorescence due to the expression of DsRed, whereas those Sf21 cells successfully infected with the recombinant MaviMNPV virus will emit green fluorescence. If, however, the Sf21 cells were successfully co-infected with both recombinant viruses, then an emission of a yellow fluorescence is expected due to the expression of both DsRed and EGFP. Accordingly, Sf21 cells emitting yellow fluorescence are chosen and the supernatant of these cells are collected and used to infect another batch of insect cells; the cultivation is monitored by the expression of fluorescent proteins until a single plaque is obtained.
To verify whether the virus collected from the single plaque contains hybrid genes, a second insect host, or a host differs from the previous host of Sf21 cells is subsequently infected with such virus. In one preferred example, the second insect host is MaviMNPV-permissive cells or larvae. Amplification procedures are repeated again until another single viral plaque is obtained, and virus collected therefrom is subject to whole genome sequence analysis, which confirmed the identified hybrid virus is AcMNPV based hybrid baculovirus and comprises at least Maruca vitrata multiple nucleopolyhedrovirus (MaviMNPV) genes of lef1, orf1629, pk1, CDS1, CDS2, and lef2; and AcMNPV/MaviMNPV-hybrid genes of egt (SEQ ID NO: 1) and orf152 (SEQ ID NO:2).
According to the preferred embodiment of the present disclosure, the AcMNPV/MaviMNPV-hybrid gene of egt (SEQ ID NO: 1) is at least 85% identical to its AcMNPV counterpart or its MaviMNPV counterpart; whereas the AcMNPV/MaviMNPV-hybrid gene of orf152 (SEQ ID NO:2) is at least 90% identical to its AcMNPV counterpart and at least 60% identical to its MaviMNPV counterpart.
Further, the AcMNPV based hybrid baculovirus is characterized in containing the nucleic acid that encodes the second fluorescent protein originated from the recombinant MaviMNPV virus in its genomic DNA. Suitable fluorescent protein includes, but is not limited to, GFP, EGFP, DsRed, BFP, EYFP, amFP, zFP, dsFP, and cFP. In the preferred example, the AcMNPV based hybrid baculovirus is characterized in containing the nucleic acid that encodes EGFP.
The thus identified AcMNPV based hybrid baculovirus is capable of infecting both AcMNPV-permissive cells or insect larvae, as well as MaviMNPV-permissive cells or insect larvae. In some examples, the AcMNPV-permissive cells may be any of Sf9, Sf21 or Hi-5 cells; and the AcMNPV-permissive insect larvae are Trichoplusia ni or Spodoptera frugiperda. In other examples, the MaviMNPV-permissive cells are NTU-MV532 cells; and the MaviMNPV-permissive insect larvae are Maruca Vitrata.
Since the afore-identified AcMNPV based hybrid baculovirus is capable of infecting at least two different types of insect hosts, it is therefore a useful means for delivering foreign genes to different insect hosts. Accordingly, the second object of the present disclosure is to provide a method of producing an exogenous protein in an insect host by use of the AcMNPV based hybrid baculovirus of the present disclosure.
In the present method, an insect host, either AcMNPV-permissive or MaviMNPV-permissive cells or insect larvae are co-transfected with the afore-identified AcMNPV based hybrid baculovirus of the present disclosure, which contains a first nucleic acid encoding a first fluorescence protein (e.g., EGFP), and a transfer vector. The transfer vector is constructed to comprise in sequence, a promoter, a second nucleic acid operably linked to the promoter and encodes the exogenous protein, an internal initiation of translation (IRES) element, and a third nucleic acid operably linked to the IRES element and encodes a second fluorescent protein; in which the first and second fluorescent proteins emit fluorescence at different wavelengths. The extent of transfection of the insect host is monitored by the expression of the first and second fluorescent proteins respectively delivered by the AcMNPV based hybrid baculovirus of the present disclosure and the transfer vector. If homologous recombination occurred between the AcMNPV based hybrid baculovirus of the present disclosure and the transfer vector, the DNA segment comprising the first fluorescent protein in the AcMNPV based hybrid baculovirus of the present disclosure would be replaced by the DNA segment comprising the exogenous protein and the second fluorescent protein of the transfer vector, therefore, allowing the AcMNPV based hybrid baculovirus of the present disclosure to deliver and express the exogenous protein gene carried by the transfer vector, to and in the insect host, by monitoring the co-expressed second fluorescent protein (such as DsRed) in the host. The insect host that emits the second fluorescence protein may then be isolated and further amplified, so as to mass produce the exogenous protein.
Suitable promoter for use in the transfer vector is any of a polyhedrin (polh) promoter, a cytomegalovirus (CMV) promoter, a CAG promoter composed of chicken β-actin promoter and CMV enhancer, and etc. In one example, the promoter is a polh promoter.
IRES sequences are distinct regions of RNA molecules that are able to attract the eukaryotic ribosome to the mRNA molecule and, therefore, allow translation initiation to occur. It is common that IRESes are located at the 5′-untranslated region (5′UTR) of some RNA viruses such as small RNA viruses or hepatitis C viruses and allow translation of the RNAs in a cap-independent manner. When an IRES element is placed between two open reading frames (ORFs) in an eukaryotic mRNA molecule, it can drive translation of the downstream protein coding region independently of the 5′-cap structure bound to the 5′-end of the mRNA molecule. In such setup, both proteins are produced in the host cell. Any known IRES sequence, either natural or chimeric, may be used to construct the transfer vector of in the present disclosure. According to preferred embodiments of the present disclosure, the IRES element of the transfer vector is a portion of a Rhopalosiphum padi virus (RhPV) IRES sequence at least 90% identical to SEQ ID NO: 3.
Exogenous proteins that may be expressed in the insect host using the AcMNPV based hybrid baculovirus of the present disclosure include at least, therapeutic proteins, insect toxic proteins or a combination thereof. Accordingly, depending on the desired exogenous proteins to be expressed, the AcMNPV based hybrid baculovirus of the present disclosure may turn the insect host into a bio-factory for mass production of therapeutic proteins, which include, but are not limited to, albumin, globulins (e.g., α-globulin), monoclonal antibodies, interferons, insulin, epidermal growth factor (EGF), erythropoietin, blood factors, and blood clotting factors. Alternatively, the AcMNPV based hybrid baculovirus of the present disclosure may carry genes of insect toxic proteins, preferably, proteins that are toxic to Lepidoptera, and act as a bio-insecticide that is effective to at least two different insect hosts. Examples of insect toxic proteins include, but are not limited to, ricin, cholera toxin, botulism toxin, scorpion neurotoxin or diphtheria toxin.
According to preferred embodiments of the present disclosure, the insect host may be AcMNPV-permissive cells or insect larvae, as well as MaviMNPV-permissive cells or insect larvae. According to further examples, the AcMNPV-permissive cells may be any of Sf9, Sf21 or Hi-5 cells; and the AcMNPV-permissive insect larvae are Trichoplusia ni or Spodoptera frugiperda. In other examples, the MaviMNPV-permissive cells are NTU-MV532 cells; and the MaviMNPV-permissive insect larvae are Maruca Vitrata.
In some embodiments of the present disclosure, the first and second fluorescent proteins may be respectively selected from the group consisting of GFP, EGFP, DsRed, BFP, EYFP, amFP, zFP, dsFP, and cFP. In one preferred example, the first and second fluorescent proteins respectively conferred by the AcMNPV based hybrid baculovirus of the present disclosure and the transfer vector are EGFP and DsRed, respectively.
To provide those skilled in the art the tools to use the present disclosure, the AcMNPV based hybrid baculovirus and host cells of this invention may be assembled to kits. The components included in the kits are viral vector, enzymatic agents for making recombinant viral constructs, cells for amplification of the viruses, and reagents for transfection and transduction into the host cells, as well as description in a form of pamphlet, tape, CD, VCD or DVD on how to use the kits.
The following examples illustrate the construction and identification of the hybrid baculovirus of the present invention and the use thereof in the production of an exogenous protein in two different insect hosts. The examples are illustrative only, and do not limit the scope of the present invention.
Cell Culture
S. furgiperda IPBL-sf21 insect cell line (herein after “Sf21 cells”) and NTU-MV532 cells derived from insect larvae of Maruca Vitrata were cultured in TNM-FH medium containing 8-10% heat-inactivated fetal bovine serum (FBS) until a confluent cell monolayer was obtained.
Measurement of EGFP or DsRed in Cell Extract
Four days after viral infection, the infected cells were lysed in 300 μl of lysing solution containing 100 mM potassium phosphate (pH 7.8), 1 mM EDTA, 10% Triton X-100, and 7 mM β-mercaptoethanol. After centrifugation at 15,200×g for 30 min, the lysate supernatant (100 μl) was taken for fluorescence measurement. The fluorescence intensities of EGFP and DsRed were measured using a Cary Eclipse Fluorescence spectrophotometer (Varian) with excitation and emission wavelength set at 488 nm and 507 nm, respectively.
Whole Genome Sequencing
The genome of the hybrid AcMv of example 1.2 was sequenced by Illumina MiSeq (Re-sequencing, 2×250 bp). The sequence was De novo assembly by Zerbino D R et al. in “Velvet: algorithms for de novo short read assembly using de Bruijn graphs” (Genome research 2008, 18 (5): 821-829).
Western Blot Analysis
After the cells were infected with the recombinant viruses for 4 days, the proteins in the cell extracts were separated by SDS-PAGE according to the procedure of Laemmli on a mini ProteinII system (Bio-Rad). The SDS-PAGE separated proteins were electrotransferred to a PVDF (polyvinyldiene difluoride) membrane (Millipore), which was then blocked with Tris-buffered saline (TTBS: 100 mM Tris, pH 7.4, 100 mM NaCl, and 0.1% Tween 20) containing 5% BSA (Sigma) at room temperature for 1 h with gentle shaking on an orbital shaker. Subsequently, membranes were incubated overnight at 4 with PBS-diluted (1:2000) anti-PCV2 antibody. Unbound antibodies were removed by three 5-min washes in TTBS buffer at room temperature with shaking. Membranes were then incubated with 1:2.500 diluted alkaline phosphate (AP) secondary antibodies (Jackson) for 1 h at room temperature. The AP on the membrane was detected by an enhanced chemiluminescence kit (Pierce) following the protocol provided by the manufacturer.
1.1 Plasmid Construction and Virus Generation
1.1.1 Construction and Generation of egfp-Mavi
The egfp-Mavi was constructed in accordance with the procedures described by Chen Y R et al. in “Genomic and host range studies of Maruca vitrata nucleopolyhedrovirus” (J. General Virology 2008, 89: 2315-2330).
1.1.2 Construction and Generation of Ac-DsRed
The DsRed gene (derived from plasmid pDsRed-N1, ClonTech, USA) was subcloned into the pBlubac4.5 transfer vector and the resulting plasmid was named pBacDsRed. The pBacDsRed (0.8 ug) was cotransfected with viral DNA Bac-N-Blue (0.2 ug, Invitrogen, USA) into Sf21 cells using Cellfectin (1 ul, Invitrogen, USA) and the resulting recombinant virus was purified by end point dilution and named Ac-DsRed.
1.1.3 Construction and Generation of Ac-egfp
The egfp gene (derived from plasmid pEGFP-C1, ClonTech, USA) was subcloned into the pBlubac4.5 transfer vector and the resulting plasmid was named pBacDsRed. The pBacDsRed (0.8 ug) was cotransfected with viral DNA Bac-N-Blue (0.2 ug, Invitrogen, USA) into Sf21 cells using Cellfectin (1 ul, Invitrogen, USA) and the resulting recombinant virus was purified by end point dilution and named Ac-egfp.
1.1.4 Construction of pMv-L-PCV2-RP110-DsRed
The fragment of PCV2-RP110-DsRed was chemically synthesized and cloned into pUC18 cloning vector to generate the plasmid pUC18-PCV2-RP110-DsRed. The baculovirus transfer vector pMv-polh-total with XhoI was then digested and ligated with the PCV2-RP110-DsRed DNA fragment (derived from pUC18-PCV2-RP110-DsRed by restriction enzyme XhoI and Sal) by T4 DNA ligase and the resultant recombinant transfer plasmid was named pMv-L-PCV2-RP110-DsRed.
1.2 Generation of Hybrid AcMv Baculovirus
Spodoptera frugiperda 21 (Sf21) cells were seeded at a density of 2×105/well and cultivated in a media containing 10% FBS. Half an hour later, the cells were co-infected with egfp-Mavi virus of example 1.1.1 and recombinant Ac-DsRed virus of example 1.1.2 at the multiplicity of infection (moi) of 1 and 10, respectively. 1.5 to 2 hours after the infection, the media were replaced by fresh culture media supplemented with 10% FBS, and the cells were incubated at 27° C. for 5 days to allow the recombination of egfp-Mavi virsus and Ac-DsRed virus. As depicted in photographs in
Five days post-infection, the culture medium in cells as depicted in
The selected desired hybrid AcMv virus of Example 1.2 was subject to further analysis including cross host infection analysis and whole genome sequencing.
2.1 Cross Host Infection Analysis
To test whether the selected hybrid AcMv virus of Example 1.2 did possess cross host infection capability, both AcMNPV-permissive cells (e.g., Sf21 or Hi-5 cells) and MaviMNPV-permissive cells (e.g., NTU-MV532 cells) were infected with the selected hybrid AcMv virus of Example 1.2, and the infection was monitored by the measurement of green fluorescence emitted by the expressed EGFP. Results are illustrated in
For Sf21 cells, which are permissive to AcMNPV and non-permissive to MaviMNPV, hence only cells infected with AcMNPV (i.e., Ac-egfp) and/or hybrid AcMv virus were capable of emitting green fluorescence, whereas no fluorescence was observed for cells infected with MaviMNPV (i.e., egfp-Mavi) (
The respective time courses of the expressed EGFP in AcMNPV-permissive and MaviMNPV-permissive cells resulted from the infected hybrid AcMv virus of Example 1.2 were also analyzed, and results are depicted in
For AcMNPV-permissive cells, the level of EGFP in Sf21 cells infected with hybrid AcMv virus of Example 1.2 or Ac-egfp started to increase on the second day post infection, and reached its peak on the fifth day; whereas the expressed level of EGFP remained relatively unchanged if cells were infected with egfp-Mavi (
Taken together, the results in
2.2 Whole Genome Sequencing
To identify the genes responsible for the cross host infection capability of the hybrid AcMv virus of Example 1.2, the virus was subject to whole genome sequencing, and sequence identity of each gene was then compared with corresponding AcMNPV and MaviMNPV genes. The results are summarized in Table 1.
As evidenced from Table 1, the hybrid AcMv virus of Example 1.2 obviously possessed a backbone of AcMNPV, with 90% of genes identical to those of AcMNPV, and only those near the polyhedron locus of AcMNPV were replaced by approximately 10-kb DNA fragment of MaviMNPV. ORFs derived from MaviMNPV included, EGFP, ORF1629, pk1, CDS1, CDS2, lef1, pe38, CDS57, ptp, CDS58, CDS59, and lef2. In addition, some hybrid ORFs were generated as well, which included egt (SEQ ID NO: 1) and Orf152 (SEQ ID NO: 2).
In this example, to verify whether the hybrid AcMv baculovirus of example 1.2 may help producing proteins in two different host cells, (i.e., AcMNPV-permissive cells and MaviMNPV-permissive cells), PCV2-cap was used as an example of an exogenous protein, and a transfer vector containing PCV2-cap was constructed in according to procedures described in example 1.1.4 (i.e., pMv-L-PCV2-RP110-DsRed).
In Sf21 cells, since they are permissive to AcMNPV, hence cells infected with the control hybrid AcMv virus of Example 1.2 (i.e., vAM-egfp) were capable of expressing EGFP and thus produced green fluorescence (
Similar observation was also found in NTU-MV532 cells, in which green fluorescence was produced in cells infected with the control hybrid AcMv virus of Example 1.2 (i.e., vAM-egfp) (
PCV2-cap harvested from the infected host cells were also analyzed by coomassie blue staining (data not shown) and further confirmed by western blot analysis. In western blot analysis, the anti-PCV2 antibody was used to detect PCV2-cap protein (
It will be understood that the above description of embodiments is given by way of example only and that various modifications may be made by those with ordinary skill in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those with ordinary skill in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.
