Animal lentivirus vaccines: problems and prospects

Potential of Nanoparticles Chitosan for Delivery pcDNA3.1-tat

The development of Jembrana disease vaccine is importance to prevent the loss of Bali cattle industry in Indonesia. This study aims to prepare a Jembrana DNA vaccine. The data Tat protein sequences gained from NCBI and the consensus process has been finished by the MultAlign program, and then Cloning of the pcDNA3.1-tat has been successfully performed on E. coli DH5α and confirmed by PCR, restriction analysis and sequencing. The propagated plasmids were prepared as DNA-chitosan complex and physiochemical characterized using Particle Size Analyzer. Complex with a 1:2 (wt/wt) ratio of DNA and chitosan have a mean diameter of 268.5 nm and zeta potential +25.1 mV and the value of Cytotoxicity Assay 80-90% as compared to the untreated cells that used as negative control, so it can be concluded that nanoparticles chitosan has good potential as a carrier agent for pcDNA3.1-tat.

In Vitro Evaluation of Chitosan-DNA Plasmid Complex Encoding Jembrana Disease Virus Env-TM Protein as a Vaccine Candidate

Introduction

The development of Jembrana disease vaccine is an important effort to prevent losses in the Bali cattle industry in Indonesia. This study aims to prepare a Jembrana DNA vaccine encoding the transmembrane portion of the envelope protein in pEGFP-C1 and test the success of its delivery in culture cells using a chitosan-DNA complex.

Material and Methods

Cloning of the DNA vaccine was successfully performed on E. coli DH5α and confirmed by colony PCR, restriction analysis and sequencing. The plasmids were prepared as a chitosan complex using the complex coacervation method and physicochemically characterised using a particle size analyser. A transfection assay was performed in HeLa cells with 4 h exposure, and mRNA expression was assessed at 24 h post transfection.

Results

With a 1:2 (wt./wt.) ratio of DNA and chitosan, the complexes have a mean diameter of 236 nm, zeta potential value of + 17.9 mV, and showed no high toxicity potential in the HeLa cells. This complex successfully delivered the DNA into cells, as shown by the presence of a specific RT-PCR product (336 bp). However, the real-time PCR analysis showed that the delivery with chitosan complex resulted in lower target mRNA expression when compared with a commercial transfecting agent.

Conclusion

pEGFP-env-tm JDV as a candidate vaccine can be delivered as the chitosan-DNA complex and be expressed at the transcription level in vitro. This initial study will be used for further improvement and evaluation in vivo.

SNPs in APOBEC3 cytosine deaminases and their association with Visna/Maedi disease progression

The Apolipoprotein B mRNA-editing catalytic polypeptide-like 3 (APOBEC3) genes are able to inhibit the replication of a wide range of exogenous retroviruses, as well as endogenous retroviruses and retrotransposons. Three APOBEC3 genes, named APOBEC3Z1, APOBEC3Z2 and APOBEC3Z3, have been described in sheep. In this work the three genes have been screened in order to identify polymorphisms. No polymorphism was detected for the A3Z2 and A3Z3 genes but 16 SNPs and a 3-bp deletion were found in the A3Z1 gene. A thermoestability prediction analysis was applied to the detected amino acidic SNPs by three different programs. This analysis revealed a number of polymorphisms that could affect the protein stability. The SNPs of the 3'UTR were tested to detect alterations on the predicted microRNA target sites. Two new microRNA target sites were discovered for one of the alleles. Two SNPs were selected for association studies in relation with the retroviral disease Visna/Maedi in Latxa and Assaf sheep breeds. Although association analyses resulted unconclusive, probably due to the unsuitability of the SNP allele frequency distribution of the selected polymorphisms in the analyzed breeds, these genes remain good candidates for association studies.

Comparison of a maedi-visna virus CA-TM fusion protein ELISA with other assays for detecting sheep infected with North American ovine lentivirus strains

A maedi-visna virus CA-TM fusion protein ELISA (MVV ELISA) was evaluated for the detection of antibody in sheep infected with North American ovine lentivirus (OvLV). The results of the MVV ELISA were compared with other assays for OvLV antibody and with viral infection in an intensively studied group of 38 sheep with a high prevalence of OvLV infection and disease. The sensitivity, specificity, and concordance of assays for OvLV antibody (MVV ELISA, indirect ELISA, Western blot, and AGID), virus (virus isolation, PCR, antigen ELISA), and OvLV-induced disease in each animal were compared with OvLV infection status as defined by a positive result in two or more of the assays. Five sheep met the criteria for absence of OvLV infection. The sensitivity of the MVV ELISA in detecting OvLV infected sheep was 64%, whereas the sensitivity of the other three tests for antibody ranged from 85 to 94%. All the antibody assays were 100% specific in this group of animals. Of the assays for virus, the PCR test had the highest sensitivity and the best concordance with OvLV infection, but it also had the lowest specificity of any of the virus or antibody assays. Among the antibody tests, the concordance of the MVV ELISA compared most favorably with the AGID test for detecting OvLV-infected sheep. Analysis of serum samples from 28 lambs experimentally-infected with one of three North American strains of OvLV suggested that there were no significant strain differences detectable by antibody assay. Twenty virus-inoculated lambs were positive by both the MVV ELISA and the AGID test, five lambs were MVV ELISA negative and AGID test positive, and three lambs were MVV ELISA positive and AGID test negative. No pre-inoculation samples were positive by either assay. In a longitudinal study involving seven lambs, antibodies to OvLV were detected by AGID 3-5 weeks post-inoculation, but were not detected by MVV ELISA until 5-10 weeks post-inoculation. Among 128 naturally and experimentally-infected sheep that were seropositive in the AGID test, the overall sensitivity of the MVV ELISA was higher in the naturally infected sheep (84%) than in the experimentally infected sheep (69%). The data indicated that the MVV ELISA represents a less sensitive, but specific alternative for the detection of OvLV antibodies.

Maedi-Visna and ovine progressive pneumonia

Maedi-Visna and ovine progressive pneumonia are disease of sheep that are caused by ovine lentivirus and characterized by chronic inflammation of the lungs, mammary glands, joints, and central nervous system. Although tremendous progress in research has led to a better understanding of the pathogenesis of these diseases, many questions still remain. Much of the mystery is the result of the complexity of the ovine lentivirus genome and the intricate interactions of the virus with the host during replication. Discoveries in molecular virology are shedding light on these interactions and novel approaches to prevent and control lentivirus infections are being explored. There is hope that some of these approaches will eventually be used to eradicate these diseases.

In vitro response of lymphocytes from bronchoalveolar lavage fluid and peripheral blood to mitogen stimulation during natural maedi-visna virus infection

To investigate the effects of maedi-visna virus (MVV) infection on cell-mediated immunity, the in vitro response of bronchoalveolar lavage fluid (BALF) and peripheral blood (BP) lymphocytes (PBL) to exogenous mitogen was analysed. BALF and PBL from control (n = 9) and MVV-infected (n = 7) animals were cultured fro 3 days in the presence and absence of concanavalin A (Con A). Lymphocyte expression of the interleukin-2 receptor (IL-2R) antigen, a parameter of lymphocyte activation, was quantified by dual-colour flow cytometry using the bovine anti-IL-2R monoclonal antibody IL-A111. IL-2R expression by lymphocytes in BALF and PB from control and MVV-infected animals, with and without Con A stimulation, were compared. In the absence of Con A stimulation, the proportion of cultured BALF CD8+ and gamma delta T cells expressing IL-2R was significantly (P < 0.05) lower for MVV-infected animals than for controls. After Con A stimulation the proportion of BALF CD4+ lymphocytes from MVV-infected animals that expressed IL-2R remained significantly (P < 0.05) lower than for controls. Comparisons within group showed that, after Con A stimulation, the proportion of all the T cell subsets in the control group expressing IL-2R, namely CD4+ (P < 0.001), CD8+ (P < 0.001) and gamma delta T cells (P < 0.05), was significantly increased. In the MVV-infected group, this increase was significant (P < 0.05) for CD4+ and CD8+ T cells, but not for gamma delta T cells. In vitro mitogen stimulation of PB T lymphocytes from both control and MVV-infected animals induced a significant elevation in the proportion of all T cell subsets expressing IL-2R when compared to cultured unstimulated control cells. However, there was considerable heterogeneity in the response to Con A of PB T cells from both groups of animals. The expression of IL-2R followed a different pattern to that of BALF lymphocytes, the proportion of unstimulated gamma delta / IL-2R+ T cells from MVV-infected animals being significantly (P < 0.05) higher than that of controls, and the proportion of cultured unstimulated CD8+ / IL-2R+ T cells from MVV-infected animals being significantly (P < 0.05) lower than that from controls. From these studies it can be concluded that the BALF T lymphocyte immune dysfunction observed during natural MVV infection, characterized by impaired IL-2R expression, is maintained under in vitro conditions.

Feline immunodeficiency virus: an interesting model for AIDS studies and an important cat pathogen

The lentivirus feline immunodeficiency virus (FIV) is a widespread pathogen of the domestic cat that is mainly transmitted through bites, although other means of transmission are also possible. Its prevalence ranges from 1 to 10% in different cat populations throughout the world, thus representing a large reservoir of naturally infected animals. FIV resembles the human immunodeficiency virus (HIV) in many respects. Similarities include the structural features of the virion, the general organization and great variability of the genome, the life cycle in the infected host, and most importantly, the pathogenic potential. Infection is associated with laboratory signs of immunosuppression as well as with a large variety of superinfections, tumors, and neurological manifestations. Our understanding of FIV is steadily improving and is providing important clues to the pathogenesis of immunodeficiency-inducing lentiviruses. The cellular receptor for FIV is different from the feline equivalent of the human CD4 molecule used by HIV; nevertheless, the major hallmark of infection is a progressive loss of CD4+ T lymphocytes as in HIV infection. The mechanisms by which FIV escapes the host's immune responses are being actively investigated. FIV causes lysis of infected T cells and also appears to predispose these cells to apoptosis. Infection of macrophages and other cell types has also been documented. For reasons yet to be understood, antibody-mediated neutralization of fresh FIV isolates is very inefficient both in vitro and in vivo. Vaccination studies have provided some encouraging results, but the difficulties encountered appear to match those met in HIV vaccine development. FIV susceptibility to antiviral agents is similar to that of HIV, thus providing a valuable system for in vivo preclinical evaluation of therapies. It is concluded that in many respects FIV is an ideal model for AIDS studies.

Experiments with inactivated visna-maedi vaccine

Sixteen Icelandic sheep were vaccinated against Visna-Maedi infection with formalin inactivated whole virus vaccine to which alun was added as an adjuvant. Western Blots showed that all the vaccinees responded to the major proteins of the virus. They all developed neutralizing antibodies ranging in titers from 1/8-1/256 at maximum for individual sheep. Passive transfer of antibodies and neutralizing activity from vaccinated ewes to their lambs was demonstrated. Exposure of the 16 vaccinees and their 16 unvaccinated control sheep to natural infection is attempted by housing them with heavily infected sheep. After 9 months of exposure there is no seroconversion in the unvaccinated group. Only time can tell, whether or not such conventional vaccination with inactivated vaccine protects the vaccinees.

Epitope analysis of capsid and matrix proteins of North American ovine lentivirus field isolates

Monoclonal antibodies (MAbs) directed against two phenotypically distinct ovine lentivirus (OvLV) strains were generated by fusion of BALB/c SP2/0-Ag 14 myeloma cells with spleen cells from mice immunized with purified OvLV. Hybridomas were selected by indirect enzyme-linked immunosorbent assay (ELISA) and analysis of reactivity on immunoblots. The majority (17 of 21) of the MAbs recognized the gag-encoded capsid protein, CA p27, of both strains. Four other MAbs recognized a smaller structural protein, presumably a matrix protein, MA p17. Three distinct epitopes on CA p27 and one on MA p17 were distinguished by the MAbs with competition ELISA. MAbs from each epitope group were able to recognize 17 North American field isolates of OvLV and the closely related caprine arthritis-encephalitis virus (CAEV). Analysis of the data indicated that these epitopes were highly conserved among naturally occurring isolates. A representative MAb from each epitope group of anti-CA p27 MAbs reacted with four field strains of OvLV and CAEV on immunoblots. An anti-MA p17 MAb recognized the same OvLV strains on immunoblots but failed to recognize CAEV. MAbs which recognize conserved epitopes of gag-encoded lentivirus proteins (CA p27 and MA p17) are valuable tools. These MAbs can be used to develop sensitive diagnostic assays and to study the pathogenesis of lentivirus infections in sheep and goats.

Inactivated simian immunodeficiency virus vaccine failed to protect rhesus macaques from intravenous or genital mucosal infection but delayed disease in intravenously exposed animals

Eight rhesus macaques were immunized four times over a period of 8 months with a psoralen-UV-light-inactivated whole simian immunodeficiency virus vaccine adjuvanted with threonyl muramyl dipeptide. Eight unvaccinated control animals received adjuvant alone. Only the vaccinated animals made antibodies before challenge exposure to the viral core and envelope as determined by Western blotting (immunoblotting) and virus-neutralizing antibodies. Ten days after the final immunization, one-half of the vaccinated and nonvaccinated monkeys were challenged exposed intravenously (i.v.) and one-half were challenge exposed via the genital mucosa with virulent simian immunodeficiency virus. All of the nonvaccinated control monkeys became persistently infected. In spite of preexisting neutralizing antibodies and an anamnestic antibody response, all of the immunized monkeys also became persistently infected. However, there was evidence that the clinical course in immunized i.v. infected animals was delayed. All four mock-vaccinated i.v. challenge-exposed animals died with disease from 3 to 9 months postchallenge. In contrast, only one of four vaccinated i.v. challenge-exposed monkeys had died by 11 months postchallenge.