Development of a candidate DNA vaccine against Maedi-Visna virus

In silico discovery of epitopes of gag and env proteins for the development of a multi-epitope vaccine candidate against Maedi Visna Virus using reverse vaccinology approach

Maedi Visna Virus (MVV) causes a chronic viral disease in sheep. Since there is no specific therapeutic drug that targets MVV, development of a vaccine against the MVV is inevitable. This study aimed to analyze the gag and env proteins as vaccine candidate proteins and to identify epitopes in these proteins. In addition, it was aimed to construct a multi-epitope vaccine candidate. According to the obtained results, the gag protein was detected to be more conserved and had a higher antigenicity value. Also, the number of alpha helix in the secondary structure was higher and transmembrane helices were not detected. Although many B cell and MHC-I/II epitopes were predicted, only 19 of them were detected to have the properties of antigenic, non-allergenic, non-toxic, soluble, and non-hemolytic. Of these epitopes, five were remarkable due to having the highest antigenicity value. However, the final multi-epitope vaccine was constructed with 19 epitopes. A strong affinity was shown between the final multi-epitope vaccine and TLR-2/4. In conclusion, the gag protein was a better antigen. However, both proteins had epitopes with high antigenicity value. Also, the final multi-epitope vaccine construct had a potential to be used as a peptide vaccine due to its immuno-informatics results.

Small ruminant lentivirus capsid protein (SRLV-p25) antigenic structural prediction and immunogenicity to recombinant SRLV-rp25-coupled to immunostimulatory complexes based on glycyrrhizinic acid

Small ruminant lentiviruses (SRLV) infect sheep and goats resulting in significant economic losses. This study evaluated for the first time the predicted conformational structure of the SRLV-capsid-protein 25 (SRLV-p25) and analyzed the antigenicity of recombinant protein (SRLV-rp25) in mice by coupling to an immunostimulatory complexes based on glycyrrhizinic acid liposomes (GAL) and tested plasma from goats and sheep naturally infected. Analysis in silico and conformational structure of SRLV-p25 (genotype B-FESC-752) showed similar characteristics to other lentiviral capsids. The efficient expression of SRLV-rp25 was confirmed by Western blot. The humoral immune responses in mice showed an increased level of antibodies from day 21 to 35 of the SRLV-rp25-GAL and SRLV-rp25-ISCOM® groups and the cellular immune response showed no significant difference in IL-10 levels (P >.05), however, a significant difference (P <.001) was observed when comparing SRLV-rp25-GAL with SRLV-rp25 groups. Immunoreactivity toward SRLV-rp25 revealed 61% of positive samples from naturally infected goats and sheep.

Small ruminant lentivirus capsid protein (SRLV-p25) antigenic structural prediction and immunogenicity to recombinant SRLV-rp25-coupled to immunostimulatory complexes based on glycyrrhizinic acid

Small ruminant lentiviruses (SRLV) infect sheep and goats resulting in significant economic losses. This study evaluated for the first time the predicted conformational structure of the SRLV-capsid-protein 25 (SRLV-p25) and analyzed the antigenicity of recombinant protein (SRLV-rp25) in mice by coupling to an immunostimulatory complexes based on glycyrrhizinic acid liposomes (GAL) and tested plasma from goats and sheep naturally infected. Analysis in silico and conformational structure of SRLV-p25 (genotype B-FESC-752) showed similar characteristics to other lentiviral capsids. The efficient expression of SRLV-rp25 was confirmed by Western blot. The humoral immune responses in mice showed an increased level of antibodies from day 21 to 35 of the SRLV-rp25-GAL and SRLV-rp25-ISCOM® groups and the cellular immune response showed no significant difference in IL-10 levels (P &gt;.05), however, a significant difference (P &lt;.001) was observed when comparing SRLV-rp25-GAL with SRLV-rp25 groups. Immunoreactivity toward SRLV-rp25 revealed 61% of positive samples from naturally infected goats and sheep.

DNA Vaccines Against Maedi-Visna Virus

Maedi-visna virus (MVV) is an ovine retrovirus of the Lentivirus genus, responsible for a chronic and progressive disease of sheep with a high prevalence all over the world. Therefore, measures aiming at the control of MVV infection are necessary, and the development of DNA vaccines may be the ideal approach. A DNA vaccine is an antigen-encoding bacterial plasmid designed to mimic infections safely, with ability to generate both humoral and cellular long-lasting immune responses once it is delivered to the host.Here, we describe the development and evaluation of DNA vaccines against ovine maedi-visna virus. The first step is the design of the vaccines, including the choice of the backbone vector and the nucleotide sequences to use as antigen-encoding sequences. Once constructed, the vaccines may be produced with high quality for use in in vitro and in vivo tests. In vitro assays are performed through transfection of animal cells to confirm the expression of the protein, while in vivo tests are carried out by mouse and/or sheep immunization in order to check humoral and cellular responses to the vaccines and conclude about their efficiency. Several approaches may be later performed in order to enhance the effectiveness of the vaccines, such as the introduction of targeting sequences, the use of a prime-boost strategy, the administration of a combined vaccine, and the use of liposomes as delivery vehicle.

Enhancement of DNA vaccine efficacy by intracellular targeting strategies

Immune response against an encoded antigenic protein can be elicited by including targeting sequences to DNA vaccines that promote protein sorting to processing pathways, related with antigen presentation by major histocompatibility complexes (MHC). Candidate DNA vaccines coding for neuraminidase 3 of the avian influenza virus were designed to encode different sequences that direct the protein to specific cellular compartments such as endoplasmic reticulum (i.e., adenovirus E1A), lysosomes (i.e., LAMP), and the combination of protein targeting to the endoplasmic reticulum and lysosome (i.e., E1A-LAMP). The DNA vaccine prototypes were engineered by biomolecular techniques and subsequently produced in E. coli cells. The biological activity of the vaccines was tested firstly in vitro, in Chinese hamster ovary cells, through flow cytometry and real-time polymerase chain reaction analysis. Then, an essential in vivo study was performed in chickens, in order to evaluate the efficacy of DNA prototype vaccines, by measuring the antibody production by enzyme-linked immunosorbent assay.

Immunization against small ruminant lentiviruses

Multisystemic disease caused by Small Ruminant Lentiviruses (SRLV) in sheep and goats leads to production losses, to the detriment of animal health and welfare. This, together with the lack of treatments, has triggered interest in exploring different strategies of immunization to control the widely spread SRLV infection and, also, to provide a useful model for HIV vaccines. These strategies involve inactivated whole virus, subunit vaccines, DNA encoding viral proteins in the presence or absence of plasmids encoding immunological adjuvants and naturally or artificially attenuated viruses. In this review, we revisit, comprehensively, the immunization strategies against SRLV and analyze this double edged tool individually, as it may contribute to either controlling or enhancing virus replication and/or disease.