Japanese encephalitis: the virus and vaccines

Small Molecule Inhibitor of ATPase Activity of HSP70 as a Broad-Spectrum Inhibitor against Flavivirus Infections

Flaviviruses including Zika virus, Dengue virus, Japanese Encephalitis virus, and Yellow Fever virus cause heavy burdens to public health around the world. No specific antiviral drug is available in the clinic against these flavivirus infections. Heat-shock protein 70 (HSP70) has recently been proven to be a promising antiviral target against Zika virus and Dengue virus. Here, we report that Apoptozole, a small molecule inhibitor of ATPase activity of HSP70, has broad-spectrum anti-flavivirus potential. The mode of action analysis revealed that Apoptozole acted at the post-entry step. Transcriptome analysis revealed that genes related to cholesterol metabolism, fatty acid synthesis, and innate immunity were differentially expressed after treatment with Apoptozole. In vivo data suggested Apoptozole exerted protection effects against Zika virus (ZIKV) infection in a mouse model by enhancing the innate immune response, which suggested a novel anti-ZIKV mechanism of HSP70 inhibitors.

Mosquito Cell-Derived Japanese Encephalitis Virus-Like Particles Induce Specific Humoral and Cellular Immune Responses in Mice

The Japanese encephalitis virus (JEV) is the major cause of an acute encephalitis syndrome in many Asian countries, despite the fact that an effective vaccine has been developed. Virus-like particles (VLPs) are self-assembled multi-subunit protein structures which possess specific epitope antigenicities related to corresponding native viruses. These properties mean that VLPs are considered safe antigens that can be used in clinical applications. In this study, we developed a novel baculovirus/mosquito (BacMos) expression system which potentially enables the scalable production of JEV genotype III (GIII) VLPs (which are secreted from mosquito cells). The mosquito-cell-derived JEV VLPs comprised 30-nm spherical particles as well as precursor membrane protein (prM) and envelope (E) proteins with densities that ranged from 30% to 55% across a sucrose gradient. We used IgM antibody-capture enzyme-linked immunosorbent assays to assess the resemblance between VLPs and authentic virions and thereby characterized the epitope specific antigenicity of VLPs. VLP immunization was found to elicit a specific immune response toward a balanced IgG2a/IgG1 ratio. This response effectively neutralized both JEV GI and GIII and elicited a mixed Th1/Th2 response in mice. This study supports the development of mosquito cell-derived JEV VLPs to serve as candidate vaccines against JEV.

The pre-existing cellular immunity to Japanese encephalitis virus heterotypically protects mice from Zika virus infection

Zika virus (ZIKV) and Japanese encephalitis virus (JEV) are closely related flaviviruses, ZIKV circulates in the population that has been JEV vaccinated in Southeast Asian countries. This alerts that a pre-existing immunity to JEV would impact ZIKV infection and/or pathogenesis. Herein we showed that the pre-existing immunity to JEV SA14-14-2 vaccination provided an ample protection against non-lethal or lethal dose of ZIKV infection in mice. This was in sharp contrast to the passive immunization of JEV antibodies, which failed to affect ZIKV infection or pathogenesis in mice, albeit these antibodies exhibited cross-reactivity and antibody dependent enhancement (ADE) of ZIKV infection in vitro. Furthermore, we determined that JEV vaccine-elicited CD8⁺ T cells were required to mediate the heterotypic protection of ZIKV infection, which cross-reacted to ZIKV E and NS5 antigens (E_294-302 and NS5_2839-2848). Adoptive transfer of these CD8⁺ T cells could partially protect the mice from ZIKV challenge. Therefore, although short of epidemiological evidence, these results suggested that cross-reactive CD8⁺ T cells activated by JEV vaccination could protect potential ZIKV infection in human populations.

Discordant Activity of Kaempferol Towards Dengue Virus and Japanese Encephalitis Virus

Kaempferol, a plant-derived flavonoid, has been reported to have activity against Japanese encephalitis virus (JEV) in BHK-21 cells. To determine the broader utility of this compound, we initially evaluated the activity of kaempferol against JEV and dengue virus (DENV) in HEK293T/17 cells. Results showed no significant antiviral activity against either virus. We subsequently investigated the activity of kaempferol against both JEV and DENV in BHK-21 cells. Results showed a significant inhibition of JEV infection but, surprisingly, a significant enhancement of DENV infection. The effect of kaempferol on both host protein expression and transcription was investigated and both transcriptional and translational inhibitory effects were observed, although a more marked effect was observed on host cell protein expression. Markedly, while GRP78 was increased in DENV infected cells treated with kaempferol, it was not increased in JEV infected cells treated with kaempferol. These results show that cellular alteration induced by one compound can have opposite effects on viruses from the same family, suggesting the presence of distinct replication strategies for these two viruses.

Virus Like Particles (VLP) as multivalent vaccine candidate against Chikungunya, Japanese Encephalitis, Yellow Fever and Zika Virus

Mosquito borne viral diseases are an emerging threat as evident from the recent outbreak of Zika virus (ZIKV) as well as repeated outbreaks of Chikungunya (CHIKV), Yellow fever (YFV) and Japanese encephalitis (JEV) virus in different geographical regions. These four arboviruses are endemic in overlapping regions due to the co-prevalence of the transmitting mosquito vector species Aedes and Culex. Thus, a multivalent vaccine that targets all four viruses would be of benefit to regions of the world where these diseases are endemic. We developed a potential Virus Like Particle (VLP) based multivalent vaccine candidate to target these diseases by using stable cell lines that continuously secrete VLPs in the culture supernatants. Moreover, inclusion of Capsid in the VLPs provides an additional viral protein leading to an enhanced immune response as evident from our previous studies with ZIKV. Immunization of Balb/c mice with different combinations of Capsid protein containing VLPs either as monovalent, bivalent or tetravalent formulation resulted in generation of high levels of neutralizing antibodies. Interestingly, the potential tetravalent VLP vaccine candidate provided strong neutralizing antibody titers against all four viruses. The 293 T stable cell lines secreting VLPs were adapted to grow in suspension cultures to facilitate vaccine scale up. Our stable cell lines secreting individual VLPs provide a flexible yet scalable platform conveniently adaptable to different geographical regions as per the need. Further studies in appropriate animal models will be needed to define the efficacy of the multivalent vaccine candidate to protect against lethal virus challenge.

Rapid differential detection of genotype I and III Japanese encephalitis virus from clinical samples by a novel duplex TaqMan probe-based RT-qPCR assay

Japanese Encephalitis (JE) is an acute infectious disease that threatens both human and pig populations throughout Asia. JE is caused by the Japanese Encephalitis Virus (JEV), of which genotype III (GIII) had been the most prevalent strain throughout Asia, but recent studies have shown that genotype I (GI) has replaced GIII as the predominant version. Pigs and mosquitoes play a primary role in JEV transmission. However, a method for the rapid differentiation between JEV G I and G III remains unavailable. This study aimed to establish a rapid JEV genotyping method using novel duplex TaqMan RT-qPCR assay.specific primer and probes located in the PrM/M gene that were able to specifically differentiate GI and GIII JEV, was selected as the duplex TaqMan RT-qPCR target.The specificity, sensitivity and reproducibility test of this assay were validated. The sensitivity of the assay was 10 genomic RNA copies for both GI and GIII JEV in field mosquito and pig samples,and more sensitive than the current methods. In addition, the novel assay can be completed in less than 1 h. Therefore, This duplex TaqMan RT-qPCR assay is a promising tool for rapid differential detection and epidemiology of GI and GIII JEV strains in China. The results showed that co-circulation of GI and GIII infections with GI infection being more prevalent in pigs or mosquitoes in eastern China.

Screening of Natural Extracts for Inhibitors against Japanese Encephalitis Virus Infection

The mosquito-borne Japanese encephalitis virus (JEV) causes serious illness worldwide that is associated with high morbidity and mortality. Currently, there are no effective drugs approved for the treatment of JEV infection. Drug-repurposing screening is an alternative approach to discover potential antiviral agents. In this study, high-content screening (HCS) of a natural extracts library was performed, and two hit FDA-approved Na⁺/K⁺-ATPase inhibitors, ouabain and digoxin, were identified as having robust efficiency against JEV infection with the selectivity indexes over 1,000. The results indicated that ouabain and digoxin blocked the JEV infection at the replication stage by targeting the Na⁺/K⁺-ATPase. Furthermore, it was proven that ouabain significantly reduced the morbidity and mortality caused by JEV in a BALB/c mouse model. This work demonstrated that Na⁺/K⁺-ATPase could serve as the target of treatment of JEV infection, and ouabain has the potential to be developed as an effective anti-JEV drug.

Recommendations for the use of Japanese encephalitis vaccines

Japanese encephalitis (JE) is a mosquito-borne viral infection which is prevalent in Taiwan. The virus circulates in an enzootic cycle in pigs which serve as amplifying hosts. Outbreaks typically occur during summer. A universal vaccination program using 4-shot mouse brain-derived inactivated vaccine has successfully controlled JE epidemics in Taiwan since 1968. More than 90% of JE cases in recent years were older than 20 years in Taiwan. Because of several drawbacks, mouse brain-derived vaccine has been replaced by newer generation JE vaccines, including inactivated Vero cell-derived vaccine and live chimeric vaccine. The present article describes the recommendations in Taiwan for the use of new JE vaccines and the schedules for shifting between different JE vaccines.

The Japanese Encephalitis Virus NS1' Protein Inhibits Type I IFN Production by Targeting MAVS

Japanese encephalitis virus (JEV) is a mosquito-borne Flavivirus that causes severe neurologic disease in humans. NS1' is a NS1-related protein only reported in the Japanese encephalitis serogroup members of Flavivirus It is produced through programmed -1 ribosomal frameshift in NS2A. Our previous study demonstrated that JEV NS1' could antagonize type I IFN (IFN-I) production, but the mechanism is still unclear. In the current study, we found that JEV NS1' inhibits the expression of MAVS, and knockdown of MAVS hampers inhibition of IFN-β induction by NS1', suggesting that JEV NS1' inhibits IFN-I production by targeting MAVS. This finding is further supported by the result of the in vivo assay that showed the similar mortality caused by NS1'-deficient virus and its wild type virus in MAVS-deficient mice. Based on our previous sequencing results of noncoding RNA in JEV-infected cells, microRNA-22 (miR-22) was identified to be a key regulator for MAVS expression during JEV infection. Furthermore, we demonstrated that JEV NS1' could induce the expression of miR-22 by increasing the binding of transcriptional factors, CREB and c-Rel, to the promoter elements of miR-22. Taken together, our results reveal a novel mechanism by which JEV NS1' antagonizes host MAVS by regulating miR-22, thereby inhibiting the IFN-I production and facilitating viral replication.

Evaluation of Japanese encephalitis virus E and NS1 proteins immunogenicity using a recombinant Newcastle disease virus in mice

Japanese encephalitis (JE) is the most important cause of acute encephalitis syndrome (AES). Japanese encephalitis virus (JEV), the prototype member of the JE serocomplex, belongs to the genus Flavivirus. The immunogenic proteins envelope (E) and non-structural protein 1 (NS1) of JEV are widely explored for the development of vaccines and diagnostics against JEV. However, there are underlying concerns such as the risk of reversion of live-attenuated vaccines to high virulence, the incomplete inactivation of pathogens in inactivated vaccines and partial vaccine coverage. Newcastle disease virus (NDV) is an efficient viral vaccine vector to express several human and animal immunogenic proteins. In the present study, we have developed a recombinant NDV (rNDV), individually expressing the E and NS1 proteins of JEV (rNDV-Ejev and rNDV-NS1jev). The recovered rNDV-Ejev and rNDV-NS1jev were characterized in 9-day-old SPF embryonated chicken eggs and in cell culture. The vaccination of rNDV-Ejev and rNDV-NS1jev showed effective immunity against JEV upon intranasal immunization in BALB/c mice. The rNDVs vaccination produced effective neutralization antibody titers against both NDV and JEV. The cytokine profiling of the vaccinated mice showed an effective Th1 and Th2 mediated immune response. The study also provided an insight that E, when used in combination with NS1 could reduce the efficacy of only E based immunization in mice. Our results suggested rNDV-Ejev to be a promising live viral vectored vaccine against JEV. This study implies an alternative and economical strategy for the development of a recombinant vaccine against JEV.

Autophagy Promotes Duck Tembusu Virus Replication by Suppressing p62/SQSTM1-Mediated Innate Immune Responses In Vitro

Duck Tembusu virus (DTMUV) has recently appeared in ducks in China and the key cellular determiners for DTMUV replication in host cells remain unknown. Autophagy is an evolutionarily conserved cellular process that has been reported to facilitate flavivirus replication. In this study, we utilized primary duck embryo fibroblast (DEF) as the cell model and found that DTMUV infection triggered LC3-II increase and polyubiquitin-binding protein sequestosome 1 (p62) decrease, confirming that complete autophagy occurred in DEF cells. The induction of autophagy by pharmacological treatment increased DTMUV replication in DEF cells, whereas the inhibition of autophagy with pharmacological treatments or RNA interference decreased DTMUV replication. Inhibiting autophagy enhanced the activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and interferon regulatory factor 7 (IRF7) pathways and increased the p62 protein level in DTMUV-infected cells. We further found that the overexpression of p62 decreased DTMUV replication and inhibited the activation of the NF-κB and IRF7 pathways, and changes in the NF-κB and IRF7 pathways were consistent with the level of phosphorylated TANK-binding kinase 1 (p-TBK1). Opposite results were found in p62 knockdown cells. In summary, we found that autophagy-mediated p62 degradation acted as a new strategy for DTMUV to evade host innate immunity.

DHA Sensor GPR120 in Host Defense Exhibits the Dual Characteristics of Regulating Dendritic Cell Function and Skewing the Balance of Th17/Tregs

In addition to functioning as an antioxidant, anti-inflammatory and age-defying cellular component, DHA impacts the immune system by facilitating the pathogen invasion. The mechanism through which DHA regulates immune suppression remains obscure. In our study, we postulated that DHA might interact with GPR120 to shape the dendritic cell (DC) differentiation and subsequently drive T cell proliferation during the virus infection. In vitro, the proportion of costimulatory molecules and HLA-DR on DC that generated from exogenous and endogenous (fad3b expression) DHA supplemented mice were significantly lower than wild-type mice. Given the importance of FAs, DHA is not only a critical cellular constituent but also a cell signaling molecule and FA deficiency reduces DC generation; we used GPR120^-/- mice to determine whether DHA receptor deficiency disorders DC maturation processing. Novelty, the expression of GPR120 on DC from wild-type (WT) mice was inversely related to DC activation and DC from the GPR120^-/- mice maintained a spontaneous maturation status. In vivo, both the excessive activation of GPR120 by DHA and the deletion of GPR120 effectively skewed the balance of Th17/Tregs and reduced the production of VNA and protection of vaccination. Overall, our results revealed a mechanism that the GPR120 self-regulation plays a crucial role in sensing DHA variation, which provides a new prospect for therapeutic manipulation in autoimmune diseases and the design of a vaccine adjuvant.

Vaccines the tugboat for prevention-based animal production

The world population is growing at a faster rate day-by-day and the demands for animal products are also increasing to meet the food security worldwide. For sustained production of animals products, healthy livestock and poultry farming are the major concerns as animals are susceptible to various infectious agents viz. bacteria, virus, and parasites leading to huge economical losses in the form of livestock’s morbidity and mortality. Besides, zoonotic nature of some infectious pathogens of animals is also raising concern for human safety. Vaccination of animals against various diseases present in different geographical regions is a best known strategy for prevention of different disease outbreaks both in organized and unorganized livestock and poultry sectors. Vaccines had played a major role in eradication of different dreaded diseases of livestock sectors globally. In this article we have discussed different vaccine types, various vaccine strategies used for the development of more efficacious and safe vaccines and commercially available vaccines for livestock and poultry.

Serological Evidence of Japanese Encephalitis Virus Circulation in Asian Children From Dengue-Endemic Countries

Background

Japanese encephalitis virus (JEV) is a zoonotic, mosquito-borne flavivirus, distributed across Asia. Infections are mostly mild or asymptomatic, but symptoms include neurological disorders, sequelae, and fatalities. Data to inform control strategies are limited due to incomplete case reporting.

Methods

We used JEV serological data from a multicountry Asian dengue vaccine study in children aged 2–14 years to describe JEV endemicity, measuring antibodies by plaque reduction neutralization test (PRNT₅₀).

Results

A total 1479 unvaccinated subjects were included. A minimal estimate of pediatric JEV seroprevalence in dengue-naive individuals was 8.1% in Indonesia, 5.8% in Malaysia, 10.8% in the Philippines, and 30.7% in Vietnam, translating to annual infection risks varying from 0.8% (in Malaysia) to 5.2% (in Vietnam). JEV seroprevalence and annual infection estimates were much higher in children with history of dengue infection, indicating cross-neutralization within the JEV PRNT₅₀ assay.

Conclusions

These data confirm JEV transmission across predominantly urban areas and support a greater emphasis on JEV case finding, diagnosis, and prevention.

How Central Is the Domestic Pig in the Epidemiological Cycle of Japanese Encephalitis Virus? A Review of Scientific Evidence and Implications for Disease Control

Despite the existence of human vaccines, Japanese encephalitis (JE) remains the leading cause of human encephalitis in Asia. Pigs are described as the main amplifying host, but their role in JE epidemiology needs to be reassessed in order to identify and implement efficient control strategies, for both human and animal health. We aimed to provide a systematic review of publications linked to JE in swine, in terms of both individual and population characteristics of JE virus (JEV) infection and circulation, as well as observed epidemiological patterns. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to select and analyze relevant articles from the Scopus database, 127 of which were included in the review. Pigs are central, but the implication of secondary hosts cannot be ruled out and should be further investigated. Although human vaccination cannot eradicate the virus, it is clearly the most important means of preventing human disease. However, a better understanding of the actual involvement of domestic pigs as well as other potential JEV hosts in different JEV epidemiological cycles and patterns could help to identify additional/complementary control measures, either by targeting pigs or not, and in some specific epidemiological contexts, contribute to reduce virus circulation and protect humans from JEV infection.

Elevation of Cleaved p18 Bax Levels Associated with the Kinetics of Neuronal Cell Death during Japanese Encephalitis Virus Infection

Japanese encephalitis virus (JEV) infection induces uncontrolled neuronal apoptosis, leading to irreversible brain damage. However, the mechanism of JEV-induced neuronal apoptosis has not been clearly elucidated. This study aimed to investigate both virus replication and neuronal cell apoptosis during JEV infection in human neuroblastoma SH-SY5Y cells. As a result, the kinetic productions of new viral progeny were time- and dose-dependent. The stimulation of SH-SY5Y cell apoptosis was dependent on the multiplicity of infections (MOIs) and infection periods, particularly during the late period of infection. Interestingly, we observed that of full-length Bax (p21 Bax) level started to decrease, which corresponded to the increased level of its cleaved form (p18 Bax). The formation of p18 Bax resulting in cytochrome c release into the cytosol appeared to correlate with JEV-induced apoptotic cell death together with the activation of caspase-3/7 activity, especially during the late stage of a robust viral infection. Therefore, our results suggest another possible mechanism of JEV-induced apoptotic cell death via the induction of the proteolysis of endogenous p21 Bax to generate p18 Bax. This finding could be a new avenue to facilitate novel drug discovery for the further development of therapeutic treatments that could relieve neuronal damage from JEV infection.

Partial cross-protection between Japanese encephalitis virus genotype I and III in mice

Genotype III (GIII) Japanese encephalitis virus (JEV) predominance has gradually been replaced by genotype I (GI) over the last 20 years in many Asian countries. This genotype shift raises concerns about the protective efficacy of Japanese encephalitis (JE) vaccines, as all of the currently licensed JE vaccines are derived from GIII strains. In this study, we conducted vaccination-challenge protection assays to evaluate the cross-protective efficacy of GI- or GIII-derived vaccines against the challenge of a heterologous genotype using a mouse challenge model. Titration of the neutralizing antibodies elicited by SA14-14-2 live-attenuated JE vaccine (SA14-14-2 vaccine), a GIII-derived vaccine, indicated that the titer of neutralizing antibodies specific to heterologous genotype GI stain was significantly lower than that specific to homologous genotype GIII strain in both pigs and mice immunized with the SA14-14-2 vaccine. Vaccination of mice with SA14-14-2 vaccine or a GIII-inactivated vaccine at high and medium doses completely protected vaccinated mice against challenge with the homologous genotype GIII strains, but failed to provide the vaccinated mice complete protection against the challenge of heterologous genotype GI strains. The protection rates against GI strain challenge were 60%–80%, showing that these vaccines were partially protective against GI strain challenge. Additionally, vaccination of mice with a GI-inactivated vaccine conferred 100% protection against the challenge of homologous genotype GI strains, but 50%–90% protection against the challenge of heterologous genotype GIII strains, showing a reduced protective efficacy of a GI-derived vaccine against GIII strain challenge. Overall, these observations demonstrated a partial cross-protection between GI and GIII strains and suggested a potential need for new JE vaccine strategies, including options like a bivalent vaccine, to control both genotype infection.

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that causes Japanese encephalitis (JE) in humans and reproductive disorders in pigs. JEV is phylogenetically classified into five genotypes. JEV genotype III (GIII) was historically dominant throughout most of Asia, but has been replaced by genotype I (GI) over the last 20 years in many Asian countries. Amino acid variations in JEV envelope protein play major roles in determination of antigenicity. Elicitation of cross-neutralizing antibodies for GI and GIII strains has been reported, showing an antigenic difference between the two genotypes. These amino acid differences in JEV envelope proteins raise a concern about the protective efficacy of JE vaccines against the emerged GI strain infection, because all currently licensed JE vaccines are derived from GIII strains. We evaluated the protective efficacy of JE vaccines against the heterologous genotype strain using a mouse challenge model and found a partial cross-protection between GI- or GIII-derived vaccines against the challenge of the heterologous genotype. This partial cross-protective efficacy suggested a potential need for a new JE vaccine, one solution may be a bivalent vaccine, to control infection with either genotype. However, more comprehensive studies should be conducted to address the partial cross-protective efficacy of JE vaccines against the heterologous genotype strains using JEV natural hosts such as pigs.

Potential Risks Associated with Japanese Encephalitis Prevalence in Shandong Province, China

Japanese encephalitis (JE), which is caused by the Japanese encephalitis virus (JEV), is a zoonotic, vector-borne neurotropic disease that remains a major cause of viral encephalitis in Asia. JEV is spread to humans through mosquitoes, and its primary transmission vector is Culex tritaeniorhynchus. Mosquitoes were sampled from three collection sites: Hanzhuang town in Weishan County, Taibai Lake in Jining city, and Dongping Lake in Shandong Province, China. Pyrethroid insecticide resistance bioassays were conducted using adult mosquitoes. Cx. tritaeniorhynchus and C. pipiens pallens populations in Hanzhuang town and Dongping Lake showed resistance to pyrethroid insecticides, and populations in Taibai Lake showed incipient resistance. Coquillettidia ochracea populations in Hanzhuang town presented resistance as well, while in Taibai Lake, resistance was incipient. A total of 16,711 mosquitoes were collected, identified, and divided into 346 pools for JEV testing. Cx. tritaeniorhynchus had the advantage of being a local mosquito species. Overall, 31 (22.96) of the 135 pools of Cx. Tritaeniorhynchus were positive for JEV. The overall maximum likelihood estimates of Cx. tritaeniorhynchus, C. pipiens pallens, and Cq. ochracea indicated pooled infection rates of 5.29/1000 mosquitoes (95% confidence interval [CI] = 3.67-7.42), 1.60/1000 mosquitoes (95% CI = 0.82-2.85), and 6.39/1000 mosquitoes (95% CI = 0.39-32.23), respectively. There were no significant differences in the pooled infection rates between the districts. The resistance to pyrethroids has increased the difficulty in controlling the mosquito vectors, especially JEV-positive mosquitoes. Given the changes in the JEV transmission vectors, the spatial and temporal diversity and the dynamic variety of mosquito species, insecticide resistance and global warming have the potential to facilitate the transmission of JE to humans.

Clinical analysis of psychiatric symptoms of Japanese encephalitis during the convalescent Period: A single center study in Chongqing, China

BACKGROUND

This study aimed to analyze clinical and imaging features of children with severe Japanese encephalitis (JE), and to analyze causes and solutions for psychiatric symptoms of JE during the convalescent period.

METHODS

We analyzed clinical information for 78 children with severe JE at the Department of Neurology, Department of Infection, and Department of Rehabilitation in our hospital during 2014-2016. Seventy-eight cases of severe JE were divided into patients with psychiatric symptoms and no psychiatric symptoms groups. We focused on analysis of the patients with psychiatric symptoms group.

RESULTS

The incidence of psychiatric symptoms during the convalescent period was 46.15% (36/78). Antipsychotic drugs can effectively control psychiatric symptoms and shorten duration of symptoms. Seventy-one patients underwent reexamination with a head MRI. Of these, 8 cases (8/36 = 22.22%) in patients with psychiatric symptoms group showed new lesions in the basal ganglia, insula, and hippocampus. During the 12-month follow-up, two cases showed reappearance of psychiatric symptoms that had been relieved previously.

CONCLUSION

This study found that severe JE cases revealed a considerable proportion with psychiatric symptoms during the convalescent period.

A common conserved peptide harboring predicted T and B cell epitopes in domain III of envelope protein of Japanese Encephalitis Virus and West Nile Virus for potential use in epitope based vaccines

Japanese encephalitis virus (JEV) and West Nile virus (WNV) are two major mosquito borne flaviviruses belonging to same serocomplex. JEV is transmitted by Culex mosquitoes and the reservoir host for the virus is pigs and/or water birds. WNV is also transmitted by Culex mosquitoes and reservoir host in this case is birds. It can also be transmitted through contact with other infected animals, their blood, or other tissues. The envelope protein of these viruses is the major source of epitopes and provides protective immunity. Bioinformatics tools were used to identify conserved epitopes in the envelope protein of these viruses. A conserved peptide "TPVGRLVTVNPFV" present in both the viruses containing predicted T and B cell epitopes was found. The model of one of the predicted epitope was generated and upon docking it bound in the groove of HLA-A0201 Class I MHC molecule. Further, it was amenable to proteasomal cleavage enhancing its chances of processing by cytosolic pathway. The peptide was found to be non toxic, non allergenic and stable in mammalian cells based on database search. The population coverage was pan world and nearly 70% identity of the peptide was found in the Zika virus envelope protein. The peptide was located in the domain III of envelope protein which is the exposed domain therefore B cell receptors may recognize this peptide easily. The conserved peptide containing T and B cell epitopes can have future application for designing epitope based vaccines for both JEV and WNV.

Development of a reverse genetics system for Japanese encephalitis virus strain SA14-14-2

Japanese encephalitis virus SA14-14-2 (JEV SA14-14-2) is a widely used vaccine in China and other southeastern countries to prevent Japanese encephalitis in children. In this study, a stable infectious cDNA clone of JEV SA14-14-2 with a low copy number pACYC177 vector dependent on the T7 promoter and T7 terminator was developed. Two introns were inserted into the capsid gene and envelope gene of JEV cDNA for gene stability. Hepatitis delta virus ribozyme (HDVr) was engineered into the 3' UTR cDNA of JEV for authentic 3' UTR transcription. The rescued virus showed biological properties indistinguishable from those of the parent strain (JEV SA14-14-2). The establishment of a JEV SA14-14-2 reverse genetics system lays the foundation for the further development of other flavivirus vaccines and viral pathogenesis studies.

[Mosquito microbiota and its influence on disease vectorial transmission]

Mosquitoes (Diptera: Culicidae) are found worldwide. Around 100 among 3500 mosquito species are known to be vectors of parasites and viruses, responsible for infectious diseases including malaria and dengue. Mosquitoes host diverse microbial communities that influence disease transmission, either by direct interference or via affecting host immunity and physiology. These microbial communities are present within diverse tissues, including the digestive tract, and vary depending on the sex of the mosquito, its developmental stage, and ecological factors. This review summarizes the current knowledge about the mosquito microbiota, defined as a community of commensal, symbiotic or pathogenic microbes harboured by a host. We first describe the current knowledge on the diversity of the microbiota, that includes bacteria, fungi, parasites and viruses and on its modes of acquisition throughout the mosquito life cycle. We then focus on microbial interactions within the mosquito gut, which notably affect vector competence, and on host-microbe interactions affecting mosquito fitness. Finally, we discuss current or potential methods based on the use of microbes or microbial products to interfere with pathogen transmission or to reduce mosquito lifespan and reproduction.

HLA Class II Genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 Are Associated With the Antibody Response to Inactivated Japanese Encephalitis Vaccine

Aim: The objective of this study was to evaluate the association of the human leukocyte antigen (HLA) class II genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 with the humoral immune response elicited by inactivated Japanese encephalitis (JE) vaccine (IJEV).

Methods: A total of 373 individuals aged 3–12 years in the Inner Mongolia Autonomous Region in China, who received two doses of IJEV at 0 and 7 days, were enrolled in the current study. Based on the individuals' specific JE virus (JEV)-neutralizing antibodies (NAbs), they were divided into a seropositive and a seronegative group. HLA-DRB1, HLA-DPB1, and HLA-DQB1 were genotyped using a sequencing-based typing method. Next, the association of the HLA class II genes and their haplotypes with antibody response was evaluated.

Results: Based on NAbs, a total of 161 individuals were classified as seropositive and 212 as seronegative. DQB1^*02:01 was significantly associated with JEV seropositivity (P < 0.001, OR = 0.364, 95% CI: 0.221–0.600), while DQB1^*02:02 was significantly associated with JEV seronegativity (P = 5.03 × 10⁻⁶, OR = 7.341, 95% CI: 2.876–18.736). The haplotypes DRB1^*07:01-DPB1^*04:01-DQB1^*02:01, DRB1^*15:01-DPB1^*02:01-DQB1^*06:02, DRB1^*07:01-DQB1^*02:01, and DPB1^*02:01-DQB1^*06:02 were very frequent in the seropositive group, while DRB1^*07:01-DPB1^*17:01-DQB1^*02:02, DRB1^*07:01-DQB1^*02:02, and DPB1^*17:01-DQB1^*02:02 were very frequent in the seronegative group. The presence of DRB1^*01:01, DRB1^*04:05, DRB1^*09:01, DRB1^*12:02, DRB1^*13:02, and DRB1^*14:01 was associated with a higher geometric mean titer (GMT) of NAbs than that of DRB1^*11:01 at the DRB1 locus (P < 0.05). At the DPB1 locus, the presence of DPB1^*05:01 was associated with higher GMTs than that of DPB1^*02:01 and DPB1^*13:01 (P < 0.05), and the presence of DPB1^*04:01 and DPB1^*09:01 was associated with higher GMTs than that of DPB1^*13:01 (P < 0.05).

Conclusions: The present study suggests that HLA class II genes may influence the antibody response to IJEV.

Drug Repurposing for Japanese Encephalitis Virus Infection by Systems Biology Methods

Japanese encephalitis is a zoonotic disease caused by the Japanese encephalitis virus (JEV). It is mainly epidemic in Asia with an estimated 69,000 cases occurring per year. However, no approved agents are available for the treatment of JEV infection, and existing vaccines cannot control various types of JEV strains. Drug repurposing is a new concept for finding new indication of existing drugs, and, recently, the concept has been used to discover new antiviral agents. Identifying host proteins involved in the progress of JEV infection and using these proteins as targets are the center of drug repurposing for JEV infection. In this study, based on the gene expression data of JEV infection and the phenome-wide association study (PheWAS) data, we identified 286 genes that participate in the progress of JEV infection using systems biology methods. The enrichment analysis of these genes suggested that the genes identified by our methods were predominantly related to viral infection pathways and immune response-related pathways. We found that bortezomib, which can target these genes, may have an effect on the treatment of JEV infection. Subsequently, we evaluated the antiviral activity of bortezomib using a JEV-infected mouse model. The results showed that bortezomib can lower JEV-induced lethality in mice, alleviate suffering in JEV-infected mice and reduce the damage in brains caused by JEV infection. This work provides an agent with new indication to treat JEV infection.

Mosquito-Borne Diseases

Mosquito-borne diseases have become more common as previously geographically isolated diseases have spread globally. Chikungunya, dengue, Japanese encephalitis, malaria, West Nile, yellow fever, and Zika are a few of the common and emerging viral diseases spread by mosquitoes. A thorough patient history, physical, and knowledge of diagnostic testing based on symptom duration is important to make a quick and accurate diagnosis. Because the treatment for many of these diseases is supportive, the emphasis is on reducing risk and spread of infection.

Rapid response to an emerging infectious disease - Lessons learned from development of a synthetic DNA vaccine targeting Zika virus

Vaccines are considered one of the greatest advances in modern medicine. The global burden of numerous infectious diseases has been significantly reduced, and in some cases, effectively eradicated through the deployment of specific vaccines. However, efforts to develop effective new vaccines against infectious pathogens such as influenza, Human immunodeficiency virus (HIV), dengue virus (DENV), chikungunya virus (CHIKV), Ebola virus, and Zika virus (ZIKV) have proven challenging. Zika virus is a mosquito-vectored flavivirus responsible for periodic outbreaks of disease in Africa, Southeast Asia, and the Pacific Islands dating back over 50 years. Over this period, ZIKV infections were subclinical in most infected individuals and resulted in mild cases of fever, arthralgia, and rash in others. Concerns about ZIKV changed over the past two years, however, as outbreaks in Brazil, Central American countries, and Caribbean islands revealed novel aspects of infection including vertical and sexual transmission modes. Cases have been reported showing dramatic neurological pathologies including microcephaly and other neurodevelopmental problems in babies born to ZIKV infected mothers, as well as an increased risk of Guillain-Barre syndrome in adults. These findings prompted the World Health Organization to declare ZIKV a public health emergency in 2016, which resulted in expanded efforts to develop ZIKV vaccines and immunotherapeutics. Several ZIKV vaccine candidates that are immunogenic and effective at blocking ZIKV infection in animal models have since been developed, with some of these now being evaluated in the clinic. Additional therapeutics under investigation include anti-ZIKV monoclonal antibodies (mAbs) that have been shown to neutralize infection in vitro as well as protect against morbidity in mouse models of ZIKV infection. In this review, we summarize the current understanding of ZIKV biology and describe our efforts to rapidly develop a vaccine against ZIKV.

Effective inhibition of different Japanese encephalitis virus genotypes by RNA interference targeting two conserved viral gene sequences in vitro and in vivo

Japanese encephalitis is a zoonotic, mosquito-borne, infectious disease caused by Japanese encephalitis virus (JEV), which is prevalent in China. At present, there are no specific drugs or therapies for JEV infection, which can only be treated symptomatically. Lentivirus-mediated RNA interference (RNAi) is a highly efficient method to silence target genes. In this study, two lentiviral shRNA, LV-C and LV-NS5, targeting the conserved viral gene sequences were used to inhibit different JEV genotypes strains in BHK21 cells and mice. The results showed that LV-C significantly inhibited JEV genotype I and genotype III strains in cells and mice. Quantitative RT-PCR analysis showed that JEV mRNA were reduced by 83.2-90.9% in cells by LV-C and that flow cytometry analysis confirmed the inhibitory activity of LV-C. The viral titers were reduced by about 1000-fold in cells and the brains of suckling mice by LV-C, and the pretreatment of LV-C protected 60-80% of mice against JEV-induced lethality. The inhibitory activities of LV-NS5 in cells and mice were weaker than those of LV-C. These results indicate that RNAi targeting of the two conserved viral gene sequences had significantly suppressed the replication of different JEV genotypes strains in vitro and in vivo, highlighting the feasibility of RNAi targeting of conserved viral gene sequences for controlling JEV infection.

Activation of neuronal N-methyl-D-aspartate receptor plays a pivotal role in Japanese encephalitis virus-induced neuronal cell damage

BACKGROUND

Overstimulation of glutamate receptors, especially neuronal N-methyl-D-aspartate receptor (NMDAR), mediates excitatory neurotoxicity in multiple neurodegenerative diseases. However, the role of NMDAR in the regulation of Japanese encephalitis virus (JEV)-mediated neuropathogenesis remains undisclosed. The primary objective of this study was to understand the function of NMDAR to JEV-induced neuronal cell damage and inflammation in the central nervous system.

METHODS

The effect of JEV-induced NMDAR activation on the progression of Japanese encephalitis was evaluated using the primary mouse neuron/glia cultures and a mouse model of JEV infection. A high-affinity NMDAR antagonist MK-801 was employed to block the activity of NMDAR both in vitro and in vivo. The subsequent impact of NMDAR blockade was assessed by examining the neuronal cell death, glutamate and inflammatory cytokine production, and JEV-induced mice mortality.

RESULTS

JEV infection enhanced the activity of NMDAR which eventually led to increased neuronal cell damage. The data obtained from our in vitro and in vivo assays demonstrated that NMDAR blockade significantly abrogated the neuronal cell death and inflammatory response triggered by JEV infection. Moreover, administration of NMDAR antagonist protected the mice from JEV-induced lethality.

CONCLUSION

NMDAR plays an imperative role in regulating the JEV-induced neuronal cell damage and neuroinflammation. Thus, NMDAR targeting may constitute a captivating approach to rein in Japanese encephalitis.

Early Events in Japanese Encephalitis Virus Infection: Viral Entry

Japanese encephalitis virus (JEV), a mosquito-borne zoonotic flavivirus, is an enveloped positive-strand RNA virus that can cause a spectrum of clinical manifestations, ranging from mild febrile illness to severe neuroinvasive disease. Today, several killed and live vaccines are available in different parts of the globe for use in humans to prevent JEV-induced diseases, yet no antivirals are available to treat JEV-associated diseases. Despite the progress made in vaccine research and development, JEV is still a major public health problem in southern, eastern, and southeastern Asia, as well as northern Oceania, with the potential to become an emerging global pathogen. In viral replication, the entry of JEV into the cell is the first step in a cascade of complex interactions between the virus and target cells that is required for the initiation, dissemination, and maintenance of infection. Because this step determines cell/tissue tropism and pathogenesis, it is a promising target for antiviral therapy. JEV entry is mediated by the viral glycoprotein E, which binds virions to the cell surface (attachment), delivers them to endosomes (endocytosis), and catalyzes the fusion between the viral and endosomal membranes (membrane fusion), followed by the release of the viral genome into the cytoplasm (uncoating). In this multistep process, a collection of host factors are involved. In this review, we summarize the current knowledge on the viral and cellular components involved in JEV entry into host cells, with an emphasis on the initial virus-host cell interactions on the cell surface.

Zika virus vaccines: immune response, current status, and future challenges

Zika virus (ZIKV) is the most recent mosquito-transmitted virus to cause a global health crisis following its entrance into a naïve population in the Western Hemisphere. Once the ZIKV outbreak began investigators rapidly established small and large animal models of pathogenesis, developed a number candidate vaccines using different platforms, and defined mechanisms of protection. In this review, we characterize the adaptive immune response elicited by ZIKV infections and vaccines, the status of ongoing clinical trials in humans, and discuss future challenges within the field.

Evolving Epidemiology of Japanese Encephalitis: Implications for Vaccination

PURPOSE OF REVIEW

We examine the present global burden of Japanese encephalitis (JE) in endemic populations, summarize published cases in travelers since 2009, examine current guidelines for vaccination for international travelers, and consider challenges in prevention of this vector-borne disease.

RECENT FINDINGS

We identified 11 JE cases in travelers that were published in peer-reviewed literature since 2009. JE incidence in endemic countries appears to be declining but the number of JE cases reported to the World Health Organization (WHO) varied from estimates derived from other published reports based on serosurveys or sentinel surveillance. Current JE vaccines appear to be safe and are not associated with delayed hypersensitivity in contrast to the older mouse brain vaccine. Given differences between WHO-reported cases and local surveillance data, future research on true incidence is needed. Regular assessment will inform JE risk in travelers. National and international guidelines on JE vaccination varied; we suggest areas for improvement.

Age-related differences in humoral and cellular immune responses after primary immunisation: indications for stratified vaccination schedules

Immunosenescence is characterised by reduced B and T cell responses. Evidence shows that booster vaccinations are less effective in elderly people, but data on the efficacy of primary immunisation are sparse. We conducted a monocentric, open label, phase IV trial to compare immune responses to primary vaccinations using the inactivated, adjuvanted Japanese Encephalitis vaccine by 30 elderly people (mean 69, range 61-78 years) and 30 younger people (mean 24, range 18-30 years). Humoral and cellular immune responses were analysed in relation to age and cytomegalovirus (CMV) seropositivity. Vaccine-specific antibody titres were significantly lower in elderly participants and 47% of them were non- or low responders after the two doses of the vaccine neo-antigen. The reduced humoral immune responses in elderly people correlated with reduced cytokine production, such as interferon gamma (IFN-γ) in vitro, as well as higher frequencies of late-differentiated effector and effector memory T cells and T regulatory cells. These cellular changes and lower antibody titres were particularly prominent in CMV-seropositive elderly participants. If primary vaccination before the age of 60 is not possible, elderly patients may require different vaccination strategies to ensure sufficient long-lasting immunity, such as adapted or accelerated schedules and the use of different adjuvants.

Chemokine receptor antagonist block inflammation and therapy Japanese encephalitis virus infection in mouse model

Japanese encephalitis (JE) is a viral encephalitis disease caused by infection with the Japanese encephalitis virus (JEV). The virus can cross the blood-brain barrier and cause death or long-term sequela in infected humans or animals. In this study, we first investigated the distribution of JEV infection in brain and further analyzed the dynamic change in inflammation related genes, chemokines, as well as pathological characteristics. Results demonstrated that CCR2 and CCR5 antagonist could significantly inhibit the inflammation. The mice treated with CCR2 and CCR5 antagonists had a higher survival rate between 60% and 70%, respectively. In summary, our study thoroughly illustrated the characteristics of the dynamic change in inflammation related genes and chemokines induced by JEV infection. We further indicated that CCR5 and CCR2 are potential targets for treatment of JE.

DDX5 RNA Helicases: Emerging Roles in Viral Infection

Asp-Glu-Ala-Asp (DEAD)-box polypeptide 5 (DDX5), also called p68, is a prototypical member of the large ATP-dependent RNA helicases family and is known to participate in all aspects of RNA metabolism ranging from transcription to translation, RNA decay, and miRNA processing. The roles of DDX5 in cell cycle regulation, tumorigenesis, apoptosis, cancer development, adipogenesis, Wnt-β-catenin signaling, and viral infection have been established. Several RNA viruses have been reported to hijack DDX5 to facilitate various steps of their replication cycles. Furthermore, DDX5 can be bounded by the viral proteins of some viruses with unknown functions. Interestingly, an antiviral function of DDX5 has been reported during hepatitis B virus and myxoma virus infection. Thus, the precise roles of this apparently multifaceted protein remain largely obscure. Here, we provide a rapid and critical overview of the structure and functions of DDX5 with a particular emphasis on its role during virus infection.

Understanding modern-day vaccines: what you need to know

Vaccines are considered to be one of the greatest public health achievements of the last century. Depending on the biology of the infection, the disease to be prevented, and the targeted population, a vaccine may require the induction of different adaptive immune mechanisms to be effective. Understanding the basic concepts of different vaccines is therefore crucial to understand their mode of action, benefits, risks, and their potential real-life impact on protection. This review aims to provide healthcare professionals with background information about the main vaccine designs and concepts of protection in a simplified way to improve their knowledge and understanding, and increase their confidence in the science of vaccination ( Supplementary Material ). KEY MESSAGE Different vaccine designs, each with different advantages and limitations, can be applied for protection against a particular disease. Vaccines may contain live-attenuated pathogens, inactivated pathogens, or only parts of pathogens and may also contain adjuvants to stimulate the immune responses. This review explains the mode of action, benefits, risks and real-life impact of vaccines by highlighting key vaccine concepts. An improved knowledge and understanding of the main vaccine designs and concepts of protection will help support the appropriate use and expectations of vaccines, increase confidence in the science of vaccination, and help reduce vaccine hesitancy.

Seasonal Patterns of Japanese Encephalitis and Associated Meteorological Factors in Taiwan

The persistent transmission of Japanese encephalitis virus (JEV) in Taiwan necessitates exploring the risk factors of occurrence of Japanese encephalitis (JE). The purpose of this study was to assess the relationship between meteorological factors and the incidence of JE in Taiwan. We collected data for cases of JE reported to the Taiwan Centers for Disease Control (Taiwan CDC) from 2000 to 2014. Meteorological data were obtained from the Taiwan Central Weather Bureau. The relationships between weather variability and the incidence of JE in Taiwan were determined via Poisson regression analysis and a case-crossover methodology. During the 15-year study period, a total of 379 cases of JE were reported. The incidence of JE showed significant seasonality, with the majority of cases occurring in summertime (for oscillation, p < 0.001). The number of JE cases started to increase at temperatures of 22 °C (r² = 0.88, p < 0.001). Similarly, the number of JE cases began to increase at a relative humidity of 70-74% (r² = 0.75, p < 0.005). The number of JE cases was positively associated with mean temperature and relative humidity in the period preceding the infection. In conclusion, the occurrence of JE is significantly associated with increasing temperature and relative humidity in Taiwan. Therefore, these factors could be regarded as warning signals indicating the need to implement preventive measures.

Development of a stable Japanese encephalitis virus replicon cell line for antiviral screening

Japanese encephalitis virus (JEV), an important pathogen in Eastern and Southern Asia and the Pacific, has spread to Australia and other territories in recent years. Although the vaccine for JEV has been used in some countries, development of efficient antiviral drugs is still an urgent requirement. Replicon systems have been widely used in the research of viral replication and antiviral screening for West Nile virus (WNV), yellow fever virus (YFV) and dengue virus (DENV). Here, a novel JEV replicon harboring the Rluc and Pac gene (JEV-Pac-Rluc-Rep) was constructed. Furthermore, we established a BHK-21 cell line harboring JEV-Pac-Rluc-Rep (BHK-21_/PAC/Rluc cell line) through continuous puromycin selection. Characterization of cell line stability showed that the replicon RNA could persistently replicate in this cell line for at least up to 10 rounds of passage. Using a known flavivirus inhibitor, the JEV replicon cell line was validated for antiviral screening. The JEV replicon cell line will be a valuable tool for both compound screening and viral replication studies.

Heat shock protein 90β in the Vero cell membrane binds Japanese encephalitis virus

The pathogenesis of Japanese encephalitis virus (JEV) is complex and unclearly defined, and in particular, the effects of the JEV receptor (JEVR) on diverse susceptible cells are elusive. In contrast to previous studies investigating JEVR in rodent or mosquito cells, in this study, we used primate Vero cells instead. We noted that few novel proteins co‑immunoprecipitated with JEV, and discovered that one of these was heat shock protein 90β (HSP90β), which was probed by mass spectrometry with the highest score of 60.3 after questing the monkey and human protein databases. The specific HSP90β‑JEV binding was confirmed by western blot analysis under non‑reducing conditions, and this was significantly inhibited by an anti‑human HSP90β monoclonal antibody in a dose‑dependent manner, as shown by immunofluorescence assay and flow cytometry. In addition, the results of confocal laser scanning microscopic examination demonstrated that the HSP90β‑JEV binding occurred on the Vero cell surface. Finally, JEV progeny yields determined by plaque assay were also markedly decreased in siRNA‑treated Vero cells, particularly at 24 and 36 h post‑infection. Thus, our data indicate that HSP90β is a binding receptor for JEV in Vero cells.

Guidelines for the prevention of travel-associated illness in older adults

International travel to the developing world is becoming more common in elderly patients (defined here as individuals greater than 65 years old). When providing pre-travel counseling, providers must appreciate the changing physiology, comorbidities, immunity and pharmacokinetics associated with the aging process to prepare elderly patients for the stressors of international travel. These guidelines present an evidence-based approach to pre-travel counseling, immunization, and pharmacology concerns unique to elderly patients seeking care in a travel clinic setting.

Expression of domain III of the envelope protein from GP-78: a Japanese encephalitis virus

Acute encephalitis caused by the Japanese encephalitis virus (JEV) represents a growing epidemic and is a cause for concern in Southeast Asia. JEV is transmitted to humans through the bite of the Culicine mosquito species. The virus genome comprising of an RNA strand also encodes the envelope protein (E) which surrounds the virus. The E protein aids in fusion of virus with the cellular membrane of the host cell with the help of three structurally distinct domains (DI, DII, DIII) that are connected by flexible hinge regions. Of these domains, DIII (JEV-DIII) has been reported to interact with the cellular membrane, aid viral entry and viral replication. Hence JEV-DIII has the potential to be an antigen that can provide immune protection to a JEV infection. In this study, we describe the cloning and expression of DIII of GP-78, a virulent strain of JEV prevalent in India. Our data clearly shows that JEV-DIII expressed from pVAC1 in HEK293T cells is membrane targeted. To our knowledge, this is the first demonstration of a recombinant construct that may block JEV entry into the cells and/or evoke specific antibodies against JEV. Future studies will reveal if our construct will elicit significant immune responses which will alleviate or ameliorate the pro-inflammatory responses induced by JEV.

A Japanese Encephalitis Virus Vaccine Inducing Antibodies Strongly Enhancing In Vitro Infection Is Protective in Pigs

The Japanese encephalitis virus (JEV) is responsible for zoonotic severe viral encephalitis transmitted by Culex mosquitoes. Although birds are reservoirs, pigs play a role as amplifying hosts, and are affected in particular through reproductive failure. Here, we show that a lentiviral JEV vector, expressing JEV prM and E proteins (TRIP/JEV.prME), but not JEV infection induces strong antibody-dependent enhancement (ADE) activities for infection of macrophages. Such antibodies strongly promoted infection via Fc receptors. ADE was found at both neutralizing and non-neutralizing serum dilutions. Nevertheless, in vivo JEV challenge of pigs demonstrated comparable protection induced by the TRIP/JEV.prME vaccine or heterologous JEV infection. Thus, either ADE antibodies cause no harm in the presence of neutralizing antibodies or may even have protective effects in vivo in pigs. Additionally, we found that both pre-infected and vaccinated pigs were not fully protected as low levels of viral RNA were found in lymphoid and nervous system tissue in some animals. Strikingly, the virus from the pre-infection persisted in the tonsils throughout the experiment. Finally, despite the vaccination challenge, viral RNA was detected in the oronasal swabs in all vaccinated pigs. These latter data are relevant when JEV vaccination is employed in pigs.