Enhanced immune responses against Japanese encephalitis virus using recombinant adenoviruses coexpressing Japanese encephalitis virus envelope and porcine interleukin-6 proteins in mice

Construction and Evaluation of the Immunogenicity and Protective Efficacy of Recombinant Replication-Deficient Human Adenovirus-5 Expressing Genotype VII Newcastle Disease Virus F Protein and Infectious Bursal Disease Virus VP2 Protein

Newcastle disease (ND) and infectious bursal disease (IBD) are two key infectious diseases that significantly threaten the health of the poultry industry. Although existing vaccinations can effectively prevent and treat these two diseases through multiple immunizations, frequent immunization stresses significantly impact chicken growth. In this study, three recombinant adenoviruses, rAd5-F expressing the NDV (genotype VII) F protein, rAd5-VP2 expressing the IBDV VP2 protein, and rAd5-VP2-F2A-F co-expressing F and VP2 proteins, were constructed using the AdEasy system. The F and VP2 genes of the recombinant adenoviruses could be transcribed and expressed normally in HEK293A cells as verified by RT-PCR and Western blot. The three recombinant viruses were shown to have similar growth kinetics as rAd5-EGFP. Compared with the PBS and rAd5-EGFP groups, SPF chickens immunized with recombinant adenoviruses produced higher antibody levels, more significant lymphocyte proliferation, and significantly higher CD4+/CD3+ and CD8+/CD3+ cells in peripheral blood. The survival rate of SPF chickens immunized with rAd5-F and rAd5-VP2-F2A-F after the challenge with DHN3 was 100%, and 86% of SPF chickens showed no viral shedding at 7 dpc. The survival rate of SPF chickens immunized with rAd5-VP2 and rAd5-VP2-F2A-F after the challenge with BC6/85 was 86%. rAd5-VP2 and rAd5-VP2-F2A-F significantly inhibited bursal atrophy and pathological changes compared to the rAd5-EGFP and PBS groups. This study provides evidence that these recombinant adenoviruses have the potential to be developed into safe and effective vaccine candidates for the prevention and control of ND and IBD.

Enhanced Immune Responses Against Japanese Encephalitis Virus Infection Using Japanese Encephalitis Live-Attenuated Virus Adjuvanted with Montanide GEL 01 ST in Mice

Japanese encephalitis virus (JEV) is one of the major causes of acute encephalitis in human and animal. To prevent JEV infection, an effective live-attenuated vaccine is needed. In the article, JEV attenuated strain, SCYA201201 of GI genotype, which was mixed with 10% concentrate GEL 01 ST adjuvant (Montanide™ GEL 01 ST), was selected for a vaccine candidate and its immunogenicity was evaluated in mice. Our results showed that JEV mixed with GEL 01 ST elicited production of both IgG1 and IgG2a antibodies, and enhanced virus-specific crossprotective intergenotypic response in mice. Proliferation of splenocytes was observed in all immunized groups and a relatively higher proliferation activity was detected in JEV mixed with GEL 01 ST group (p < 0.05). In the JEV + 10% GEL 01 ST vaccinated group, the proportion of CD4⁺ T cells in spleen was significantly higher than that of control group (p < 0.05), and the yields of interleukin (IL)-2, IL-4, and interferon-γ in the splenocyte supernatant were also significantly higher than that of control group (p < 0.05). Moreover, complete protection was provided after JEV challenge in mice in JEV mixed with GEL 01 ST group, and early immunity was detected in those mice immunized with JEV mixed with GEL 01 ST. These findings confirm that GEL 01 ST can enhance JEV live-attenuated immunogenicity, and JEV +10% GEL 01 ST used as vaccine candidates provide protection against JEV infection in a mouse model, which could be used as potential vaccine candidates in pig.

Aerosol and Contact Transmission Following Intranasal Infection of Mice with Japanese Encephalitis Virus

The Japanese encephalitis virus (JEV), a causative agent of severe viral encephalitis in humans, has a biological cycle fluctuating between transmission in mosquitoes and avian species and amplification in pigs. Contact transmission of JEV was recently shown in pigs in the absence of arthropod vectors. Here, we show JEV transmission between infected and contact mice and further demonstrate that JEV transmission occurs between animals via aerosols, as both viral RNA and infectious JEV were detected in direct contact- and aerosol-exposed contact animals. The results of this study change our understanding of JEV transmission in densely populated regions and may help to explain JEV outbreaks without the presence of arthropod vectors.

A recombinant adenovirus expressing the E protein of duck Tembusu virus induces protective immunity in duck

Duck Tembusu virus disease, caused by the duck Tembusu virus (DTMUV), can lead to a severe reduction in egg production and growth retardation in laying ducks and ducklings, respectively. In this study, we engineered a novel recombinant adenovirus expressing the E protein of DTMUV (rAd-E) in AAV-293 cells (analyzed by western blot and indirect immunofluorescence assays). Intramuscular immunization of Cherry Valley ducks with rAd-E was performed to evaluate host cellular and humoral immune responses. Compared to the phosphate-buffered saline administered group and the negative control wild-type adenovirus (wtAd) group, the rAd-E vaccinated group showed increased cellular and humoral responses. The results from the cytokine release and lymphocyte proliferation assays showed that rAd-E induced a stronger cellular immune response than the control group (P<0.01), 4 weeks after primary immunization. The results of enzyme-linked immunosorbent and virus neutralization assays showed that rAd-E induced higher titers of specific neutralizing antibodies, 2 weeks after primary immunization. The DTMUV challenge experiment showed a higher survival rate (80%) of ducks in the rAd-E group, when challenged with 0.5 ml (ELD₅₀=10^−2.67/0.2 ml) of the DTMUV strain AH-F10. These results indicate that rAd-E effectively protects ducks against DTMUV infection. Therefore, rAd-E could be a vaccine candidate to provide an effective and safe method for prevention and control of DTMUV infection.