Prophylactic Administration of Gut Microbiome Metabolites Abrogated Microglial Activation and Subsequent Neuroinflammation in an Experimental Model of Japanese Encephalitis

Short-chain fatty acids (SCFAs) are gut microbial metabolic derivatives produced during the fermentation of ingested complex carbohydrates. SCFAs have been widely regarded to have a potent anti-inflammatory and neuro-protective role and have implications in several disease conditions, such as, inflammatory bowel disease, type-2 diabetes, and neurodegenerative disorders. Japanese encephalitis virus (JEV), a neurotropic flavivirus, is associated with life threatening neuro-inflammation and neurological sequelae in infected hosts. In this study, we hypothesize that SCFAs have potential in mitigating JEV pathogenesis. Postnatal day 10 BALB/c mice were intraperitoneally injected with either a SCFA mixture (acetate, propionate, and butyrate) or PBS for a period of 7 days, followed by JEV infection. All mice were observed for onset and progression of symptoms. The brain tissue was collected upon reaching terminal illness for further analysis. SCFA-supplemented JEV-infected mice (SCFA + JEV) showed a delayed onset of symptoms, lower hindlimb clasping score, and decreased weight loss and increased survival by 3 days (p < 0.0001) upon infection as opposed to the PBS-treated JEV-infected animals (JEV). Significant downregulation of inflammatory cytokines TNF-α, MCP-1, IL-6, and IFN-Υ in the SCFA + JEV group relative to the JEV-infected control group was observed. Inflammatory mediators, phospho-NF-kB (P-NF-kB) and iba1, showed 2.08 ± 0.1 and 3.132 ± 0.43-fold upregulation in JEV versus 1.19 ± 0.11 and 1.31 ± 0.11-fold in the SCFA + JEV group, respectively. Tissue section analysis exhibited reduced glial activation (JEV group─42 ± 2.15 microglia/ROI; SCFA + JEV group─27.07 ± 1.8 microglia/ROI) in animals that received SCFA supplementation prior to infection as seen from the astrocytic and microglial morphometric analysis. Caspase-3 immunoblotting showed 4.08 ± 1.3-fold upregulation in JEV as compared to 1.03 ± 0.14-fold in the SCFA + JEV group and TUNEL assay showed a reduced cellular death post-JEV infection (JEV-6.4 ± 1.5 cells/ROI and SCFA + JEV-3.7 ± 0.73 cells/ROI). Our study critically contributes to the increasing evidence in support of SCFAs as an anti-inflammatory and neuro-protective agent, we further expand its scope as a potential supplementary intervention in JEV-mediated neuroinflammation.

Activation of type I interferon antiviral response in human neural stem cells

BACKGROUND

Neural stem cells (NSCs) residing in the central nervous system play an important role in neurogenesis. Several viruses can infect these neural progenitors and cause severe neurological diseases. The innate immune responses against the neurotropic viruses in these tissue-specific stem cells remain unclear.

METHODS

Human NSCs were transfected with viral RNA mimics or infected with neurotropic virus for detecting the expression of antiviral interferons (IFNs) and downstream IFN-stimulated antiviral genes.

RESULTS

NSCs are able to produce interferon-β (IFN-β) (type I) and λ1 (type III) after transfection with poly(I:C) and that downstream IFN-stimulated antiviral genes, such as ISG56 and MxA, and the viral RNA sensors RIG-I, MDA5, and TLR3, can be expressed in NSCs under poly(I:C) or IFN-β stimulation. In addition, our results show that the pattern recognition receptors RIG-I and MDA5, as well as the endosomal pathogen recognition receptor TLR3, but not TLR7 and TLR8, are involved in the activation of IFN-β transcription in NSCs. Furthermore, NSCs infected with the neurotropic viruses, Zika and Japanese encephalitis viruses, are able to induce RIG-I-mediated IFN-β expression.

CONCLUSION

Human NSCs have the ability to activate IFN signals against neurotropic viral pathogens.

Limited susceptibility of mice to Usutu virus (USUV) infection and induction of flavivirus cross-protective immunity

Flaviviruses are RNA viruses that constitute a worrisome threat to global human and animal health. In Europe, West Nile virus (WNV) outbreaks have dramatically increased in number and severity in recent years, with dozens of human and horse deaths and a high avian mortality across the continent. Besides WNV, the only clinically relevant mosquito-borne flavivirus detected so far in Europe has been the Usutu virus (USUV), which after being reported for the first time in Austria in 2001, quickly spread across Europe, causing a considerable number of bird deaths and neurological disorders in a few immunocompromised patients. Even though USUV infects multiple avian species that develop antibodies, there is little information about USUV susceptibility, pathogenicity and cross-reactive immunity. Here, the susceptibility of suckling and adult mice to USUV infection and the induction of cross-protective immunity against WNV challenge have been addressed.

Virus-induced transcriptional changes in the brain include the differential expression of genes associated with interferon, apoptosis, interleukin 17 receptor A, and glutamate signaling as well as flavivirus-specific upregulation of tRNA synthetases

Flaviviruses, particularly Japanese encephalitis virus (JEV) and West Nile virus (WNV), are important causes of virus-induced central nervous system (CNS) disease in humans. We used microarray analysis to identify cellular genes that are differentially regulated following infection of the brain with JEV (P3) or WNV (New York 99). Gene expression data for these flaviviruses were compared to those obtained following infection of the brain with reovirus (type 3 Dearing), an unrelated neurotropic virus. We found that a large number of genes were up-regulated by all three viruses (using the criteria of a change of >2-fold and a P value of <0.001), including genes associated with interferon signaling, the immune system, inflammation, and cell death/survival signaling. In addition, genes associated with glutamate signaling were down-regulated in infections with all three viruses (criteria, a >2-fold change and a P value of <0.001). These genes may serve as broad-spectrum therapeutic targets for virus-induced CNS disease. A distinct set of genes were up-regulated following flavivirus infection but not following infection with reovirus. These genes were associated with tRNA charging and may serve as therapeutic targets for flavivirus-induced CNS disease. IMPORTANCE Viral infections of the central nervous system (CNS) are an important cause of morbidity and mortality. Treatment options for virus-induced CNS disease are limited, and for many clinically important neurotropic viruses, no specific therapy of proven benefit is currently available. We performed microarray analysis to identify genes that are differentially regulated in the brain following virus infection in order to identify pathways that might provide novel therapeutic targets for virus-induced CNS disease. Although several studies have described gene expression changes following virus infection of the brain, this report is the first to directly compare large-scale gene expression data from different viruses. We identified genes that are differentially regulated in infection of the brain with viruses from different families and those which appear to be specific to flavivirus infections.

Detection of Usutu virus infection in a healthy blood donor from south-west Germany, 2012

From September 2011 until November 2012, 31 serum samples from German patients with clinically suspected acute Usutu virus (USUV) infections were tested for USUV-specific antibodies. All samples tested negative. In addition, 4,200 serum samples from healthy blood donors from south-west Germany were collected in January 2012 and also analysed for the presence of specific antibodies. One sample tested positive for USUV-IgG and -IgM. Thus, the seroprevalence of USUV antibodies in healthy blood donors from south-west Germany was low in January 2012.

[Long-term seroprotection against Japanese encephalitis using an inactivated vaccine (Jevax)]

Japanese encephalitis vaccine (Jevax) is an inactivated vaccine using the Nakayama viral strain. Until 2007, Jevax was the only Japanese encephalitis vaccine available in France but the duration of seroprotection after vaccination and exact timing of booster injections was unclear for travelers from non-endemic areas. The purpose of this report is to describe the results of a retrospective study in which neutralizing antibody levels were measured in 71 subjects previously vaccinated with Jevax. All subjects underwent testing at the Pasteur Institute Medical Center as part of preparation for humanitarian missions to endemic Japanese encephalitis areas in 2005-2006. A neutralizing antibody level greater than or equal to 20 was considered as protective. Findings showed that 49 of the 71 subjects (69%) still had protective antibody levels at a median of 4 years after the last Jevax immunization. In multivariate analysis, the only factor correlated with long-term seroprotection was the total number of vaccinations received. Based on these findings, it was concluded that long-term seroprotection after Jevax vaccination requires repeated booster injections even in subjects frequently exposed to the virus. No correlation was found between seroprotection and the interval between the booster injections.

Induction of indistinguishable gene expression patterns in rats by Vero cell-derived and mouse brain-derived Japanese encephalitis vaccines

Transcriptomics is an objective index that reflects the overall condition of cells or tissues, and transcriptome technology, such as DNA microarray analysis, is now being introduced for the quality control of medical products. In this study, we applied DNA microarray analysis to evaluate the character of Japanese encephalitis (JE) vaccines. When administered into rat peritoneum, Vero cell-derived and mouse brain-derived JE vaccines induced similar gene expression patterns in liver and brain. Body weights and blood biochemical findings were also similar after administration of the two vaccines. Our results suggest that the two JE vaccines are likely to have equivalent characteristics with regard to reactivity in rats.

Explaining Usutu virus dynamics in Austria: model development and calibration

Usutu virus (USUV), a flavivirus of the Japanese encephalitis virus complex, was for the first time detected outside Africa in the region around Vienna (Austria) in 2001 by Weissenböck et al. [Weissenböck, H., Kolodziejek, J., Url, A., Lussy, H., Rebel-Bauder, B., Nowotny, N., 2002. Emergence of Usutu virus, an African mosquito-borne flavivirus of the Japanese encephalitis virus group, central Europe. Emerg. Infect. Dis. 8, 652-656]. USUV is an arthropod-borne virus (arbovirus) circulating between arthropod vectors (mainly mosquitoes of the Culex pipiens complex) and avian amplification hosts. Infections of mammalian hosts or humans, as observed for the related West Nile virus (WNV), are rare. However, USUV infection leads to a high mortality in birds, especially blackbirds (Turdus merula), and has similar dynamics with the WNV in North America, which, amongst others, caused mortality in American robins (Turdus migratorius). We hypothesized that the transmission of USUV is determined by an interaction of developing proportion of the avian hosts immune and climatic factors affecting the mosquito population. This mechanism is implemented into the present model that simulates the seasonal cycles of mosquito and bird populations as well as USUV cross-infections. Observed monthly climate data are specified for the temperature-dependent development rates of the mosquitoes as well as the temperature-dependent extrinsic-incubation period. Our model reproduced the observed number of dead birds in Austria between 2001 and 2005, including the peaks in the relevant years. The high number of USUV cases in 2003 seems to be a response to the early beginning of the extraordinary hot summer in that year. The predictions indicate that >70% of the bird population acquired immunity, but also that the percentage would drop rapidly within only a couple of years. We estimated annually averaged basic reproduction numbers between R (0)=0.54 (2004) and 1.35 (2003). Finally, extrapolation from our model suggests that only 0.2% of the blackbirds killed by USUV were detected by the Austrian USUV monitoring program [Chvala, S., Bakonyi, T., Bukovsky, C., Meister, T., Brugger, K., Rubel, F., Nowotny, N., Weissenböck, H., 2007. Monitoring of Usutu virus activity and spread by using dead bird surveillance in Austria, 2003-2005. Vet. Microbiol. 122, 237-245]. These results suggest that the model presented is able to quantitatively describe the process of USUV dynamics.

Survival of mice immunized with monoclonal antibodies against glycoprotein E of Japanese encephalitis virus before or after infection with Japanese encephalitis, West Nile, and Dengue viruses

In the present study, the effect of monoclonal antibodies (MAbs) against glycoprotein E (gE) of Japanese encephalitis virus (JEV) strain 733913 administered 1 day before or 2 days after intracerebral (i.c.) challenge with West Nile virus (WNV) strain 68856 or Dengue virus (DENV-2) strain P23085, was studied in mice. Furthermore, two JEV strains belonging to group II (strains 641686 and 691004) that have lost reactivity against virus-specific MAbs were also used in passive immunization experiments. MAbs as ascitic fluids were administered intraperitoneally (i.p.) in mice. Hemagglutination-inhibition- (HAI) positive JEV-specific (Hs-3) MAbs given 2 days after the virus infection showed reduced mortality along with increased survival of mice challenged with WNV or with DENV-2. Also the HAI-positive flavivirus cross-reactive (Hx) MAbs produced a marginal increase in the survival of mice challenged with both JEV strains 641686 and 691004 belonging to the group II. As the MAbs reacting with HAI-positive JEV-specific (Hs) and HAI-negative JEV-specific (NHs) epitopes were neutralizing and protective in mice against JEV strain 733913 challenge, the results indicated presence of the cross-protection phenomenon that might be occurring in some of the localities endemic for the three closely related flaviviruses.

Recent change of the antigenicity and genotype of Japanese encephalitis viruses distributed on Okinawa Island, Japan

In this study, five isolates of Japanese encephalitis virus (JEV) were obtained from swine serum samples collected on Okinawa Island, Japan, between 2002 and 2003. All five JEV isolates belonged to genotype 1, and JEV isolates obtained from the island before 1992 were genotype 3. Genotype 1 was known to be distributed from northern Thailand to Cambodia and recently expanded to Australia, Vietnam, the Republic of Korea, and Japan. However, phylogenetic analysis showed that the source of the newly emerging genotype 1 in Asia is different from that in Australia. Sero-epidemiologic investigations showed that serum samples collected from 1985 to 1988 from JEV-immune swine neutralized both the Naha Meat 54 strain (1985 JEV Okinawan isolate from swine, genotype 3) and the Oki 431S strain (2002 JEV Okinawan isolate from swine, genotype 1), and many samples collected in 2002 neutralized the Oki 431S strain but not the Naha Meat 54 strain. These results strongly suggest that the genotype and antigenicity of JEV on Okinawa Island have changed significantly over the past decade.

Serological evidence of continuing high Usutu virus (Flaviviridae) activity and establishment of herd immunity in wild birds in Austria

Usutu virus (USUV), family Flaviviridae, has been responsible for avian mortality in Austria from 2001 to 2006. The proportion of USUV-positive individuals among the investigated dead birds decreased dramatically after 2004. To test the hypothesis that establishment of herd immunity might be responsible, serological examinations of susceptible wild birds were performed. Blood samples of 442 wild birds of 55 species were collected in 4 consecutive years (2003--2006). In addition, 86 individuals from a birds of prey rehabilitation centre were bled before, at the peak, and after the 2005 USUV transmission season in order to identify titre dynamics and seroconversions. The haemagglutination inhibition test was used for screening and the plaque reduction neutralization test for confirmation. While in the years 2003 and 2004 the proportion of seropositive wild birds was <10%, the percentage of seroreactors raised to >50% in 2005 and 2006. At the birds of prey centre, almost three quarters of the owls and raptors exhibited antibodies before the 2005 transmission season; this percentage dropped to less than half at the peak of USUV transmission and raised again to almost two thirds after the transmission season. These data show a from year to year continuously increasing proportion of seropositive wild birds. The owl and raptor data indicate significant viral exposure in the previous season(s), but also a number of new infections during the current season, despite the presence of antibodies in some of these birds. Herd immunity is a possible explanation for the significant decrease in USUV-associated bird mortalities in Austria during the recent years.

Detection of seroconversion to West Nile virus, Usutu virus and Sindbis virus in UK sentinel chickens

We previously reported evidence of West Nile virus (WNV) circulation in UK birds, probably introduced by migratory birds from overseas. We now demonstrate WNV-specific seroconversion in sentinel chickens raised on an English farm. Maternal neutralizing antibodies to WNV in hatchlings declined within three weeks. During the following months, healthy chickens developed WNV neutralizing antibodies that were confirmed by immunoblotting and indirect immunofluorescence tests using WNV antigens. The proportion of seropositive chickens was higher for WNV than for Usutu virus or Sindbis virus. Attempts to isolate infectious virus or to detect viral RNA in the sera, failed.

[Influence of JEV E-HSP70 (Mycobacterium tuberculosis) fusion protein on immune response in BALB/c mice]

JEV infection can cause severe central nerve system disease which result in high mortality or developing permanent neurological sequelae in more than half of the survivors. The envelope (E) protein of JEV is the major antigen peptide fused to it. A recombinant hsp70 protein expression vector pPICZalpha-E-HSP70 in methylotrophic yeast Pichia pastoris was developed that permits major antigenic segment of JEV E protein fused to the amino terminus of M. tuberculosis hsp70. This core vector avoided inclusion bodies formed in Escherichia coli and complex purification. Moreover,it ruled out contamination of LPS. Two other vectors pPICZalpha-E and pPICZalpha-HSP70 were also constructed. The two vectors were constructed by routine molecular technique. All vectors were transformed into yeast X-33 by electroporation. Expression of the fusion protein in yeast was induced by the addition of methanol every 24 hours and analysed by SDS-PAGE and western blot. Major antigenic segment of E protein was produced at a yield of 290 mg per litter of culture, hsp70 protein at a yield of 178 mg per litter of culture and E-HSP70 fusion protein at a yield of 33 mg per litter of culture in methylotrophic yeast Pichia pastoris. To examine cell and body immune response after BALB/c mice were immunized with E-hsp70 fusion protein expressed in Pichia pastoris, there were three groups with ten mice in each group. 5.7 microg (50pmol) of E-hsp70 fusion protein, 2.2 microg (50pmol) major antigenic segment of E protein and a mixture of hsp70 and major antigenic segment of E protein (1:1) including 3.5 microg (50pmol) Hsp70 and 2.2 microg (50pmol) major antigenic segment of JEV E protein were used per mouse i.p. on day 0 and day 21. The production of mIL-2 was quantitated by semi-quantitative RT-PCR. Besides, proliferation of lymphocytes was measured by MTT and titers of antibody was determined by ELISA. These data show that the fusion protein is a more powerful antigen than major antigenic segment of JEV E protein. So it also illustrates the effectiveness of hsp70 in eliciting a humoral and cellular response to an attached molecule in the absence of adjuvant and affirms the potential utility of hsp70 in vaccine development.

Immunogenicity and protective efficacy in mice of a formaldehyde-inactivated Indian strain of Japanese encephalitis virus grown in Vero cells

P20778, an Indian strain of Japanese encephalitis virus (JEV) obtained from Vellore in the Southern India, was grown in Vero cells cultured on microcarriers in a spinner flask. The virus was formalin-inactivated and its immunogenicity and protective efficacy in mice were tested in comparison with a commercially available vaccine. Our studies indicated that formalin-inactivated JEV P20778 induced high levels of protective immunity in mice. Virus inactivation with formalin at 22 degrees C, which required shorter incubation period, was found to be as good or better to virus inactivation at 4 degrees C for generating high titers of anti-JEV antibodies. Similarly, the 22 degrees C-inactivated virus generated JEV neutralizing antibody titers as good or higher than those induced by the 4 degrees C-inactivated virus. Thus, for the vaccine production, inactivation of JEV with formalin at 22 degrees C would be a preferred method as it is faster and does not require cold room storage.

Immunogenicity in mice of a cationic microparticle-adsorbed plasmid DNA encoding Japanese encephalitis virus envelope protein

Previously, we described a plasmid pMEa, synthesizing the anchored form of Japanese encephalitis virus (JEV) envelope protein that generated virus-neutralizing antibodies in mice upon intra-muscular injection. The immunized mice showed significant protection against lethal JEV challenge. In order to improve the efficacy of plasmid DNA immunization against JEV, methods need to be employed that would enhance neutralizing antibody titers. Plasmid DNA adsorbed to cationic microparticles has recently been shown to significantly improve its immunogenicity. In the present study, we have adsorbed the plasmid pMEa on cationic microparticles and have compared its immunogenicity with the naked plasmid DNA. As seen in ELISA, the microparticle-adsorbed DNA induced higher titers of anti-JEV antibodies when compared to those induced by the naked DNA. No difference, however, was seen in JEV neutralization titers. The microparticle-adsorbed DNA induced a mixed Th1-Th2 kind of immune responses as opposed to Th1 type of immune responses elicited by the naked DNA.

Prevalence of antibody to Japanese encephalitis virus nonstructural 1 protein among racehorses in Japan: indication of natural infection and need for continuous vaccination

Japanese encephalitis virus (JEV) causes fatal diseases in equines as well as humans. In Japan, racehorses are vaccinated with inactivated JE vaccine every year and no equine JE cases have been reported since 1986. However, the current reduction in JEV activity in nature has raised an argument against the requirement of continuous vaccination. Here, we studied natural infection rates in racehorses to address the issue. To identify naturally-infected individuals from vaccinated populations, we used an immunostaining method for detecting antibodies to JEV nonstructural 1 (NS1) protein. A total of 779 horses in eight nationwide locations showed NS1 antibody prevalences ranging from 15 to 73%. NS1 antibody prevalences among 2-year-old individuals that had spent one epizootic season in a particular location, therefore representing annual infection rates, were 15-67%. Individuals aged >/=3 years showed higher NS1 antibody titers than the 2-year-olds, suggesting that NS1 antibody levels were boosted by repeated exposures to JEV antigen over >/=2 epizootic seasons. These results indicate that horses in Japan are exposed to natural JEV infections, confirming the need for continuous vaccination for protecting horses from JE.

Sub-fragments of the envelope gene are highly protective against the Japanese encephalitis virus lethal infection in DNA priming—protein boosting immunization strategies

The envelope (E) gene of Japanese encephalitis virus (JEV) plays a major protective role against JEV infection. In order to locate the part of E gene that is responsible for this protection, an N-terminal fragment EA (nucleotide number 933-1877 bp of JEV genome) and a C-terminal fragment EB (nucleotide number 1851-2330 bp of JEV genome) from E gene were prepared. Both of these fragments were used in the form of recombinant proteins (rEA and rEB) and plasmid DNA (pEA, pM15EA and pEB) for immunizations. Recombinant EA protein (rEA) was previously found to be non-protective because it was expressed in an insoluble form. Plasmid EA (pEA) was also found to be non-protective unless it is preceded by a 15 mer signal peptide derived from the very C-terminal of the membrane gene (M) of JEV to form pM15EA plasmid indicating the importance of the signal peptide in the expression of EA immunogenicity. Although pM15EA and pEB are both immunogenic and protective against JEV lethal infection, the protection by both fragments however is not optimal. Even when pM15EA and pEB were used together for immunization, maximum protection as those induced by control vaccine was not achieved. However, if individual fragments (EA or EB) were used in a DNA priming-protein boosting or protein priming-DNA boosting strategy, high levels of protection were achieved by both fragments. This was especially true for EA fragment where the level of protection against JEV lethal infection was equal to that induced by commercially available vaccine alone. The protection correlated very well with the neutralizing antibody titers and the T helper cell involved in this process in mainly the Th1 type.

Serological evidence of West Nile virus, Usutu virus and Sindbis virus infection of birds in the UK

The introduction and rapid dispersal of the African flavivirus West Nile virus (WNV) throughout North America, and the high fatality rate due to encephalitis in birds, horses, other wildlife species and humans, has attracted major attention worldwide. Usutu virus, another flavivirus, came to prominence in 2001, when it was identified as the agent responsible for a drop in the bird population in Austria; previously this encephalitic virus was found only in birds and mosquitoes in Africa. Sindbis virus, a pathogenic alphavirus that causes arthritis, is widespread throughout Africa, Europe, Asia and Australia, infecting a range of arthropods and vertebrates and is genetically related to encephalitic viruses in North America. Currently there is no evidence that any of these viruses cause disease in the UK. Here the presence of virus-specific neutralizing antibodies is reported in the sera of resident and migrant birds in the UK, implying that each of these viruses is being introduced to UK birds, possibly by mosquitoes. This is supported by nucleotide sequencing that identified three slightly different sequences of WNV RNA in tissues of magpies and a blackbird. The detection of specific neutralizing antibodies to WNV in birds provides a plausible explanation for the lack of evidence of a decrease in the bird population in the UK compared with North America. The potential health risk posed to humans and animals by these viruses circulating in the UK is discussed.

Antibodies against prM protein distinguish between previous infection with dengue and Japanese encephalitis viruses

BACKGROUND

In Southeast Asia, dengue viruses often co-circulate with other flaviviruses such as Japanese encephalitis virus, and due to the presence of shared antigenic epitopes it is often difficult to use serological methods to distinguish between previous infections by these flaviviruses.

RESULTS

Convalescent sera from 69 individuals who were known to have had dengue or Japanese encephalitis virus infection were tested by western blotting against dengue, Japanese encephalitis and West Nile virus antigens. We determined that individuals who had been infected with dengue viruses had IgG responses against the premembrane protein of dengue viruses but not Japanese encephalitis, whereas individuals who had been infected with Japanese encephalitis had IgG specific for the premembrane protein of Japanese encephalitis virus but not the dengue viruses. None reacted with the premembrane protein of West Nile virus. Using the Pearson Chi Square test, it was determined that the difference between the two groups was highly significant with a p value of <0.001.

CONCLUSION

The use of flavivirus premembrane protein in seroepidemiological studies will be useful in determining what flaviviruses have circulated in a community.

Antiviral cytotoxic T cells cross-reactively recognize disparate peptide determinants from related viruses but ignore more similar self- and foreign determinants

We have investigated the reactivities of cytotoxic T (Tc) cells against the two immunodominant, H-2K(k)-restricted determinants from the FLAVIVIRUS: Murray Valley encephalitis virus (MVE), MVE(1785) (REHSGNEI) and MVE(1971) (DEGEGRVI). The respective Tc cell populations cross-reactively lysed target cells pulsed with determinants from the MVE(1785)- and MVE(1971)-corresponding positions of six other flaviviruses, despite low sequence homology in some cases. Notably, anti-MVE(1785) Tc cells recognized a determinant (TDGEERVI) that shares with the determinant used for stimulation only the carboxyl-terminal amino acid residue, one of two H-2K(k) anchor residues. These reactivity patterns were also observed in peptide-dependent IFN-gamma production and the requirements for in vitro restimulation of memory Tc cells. However, the broad cross-reactivity appeared to be limited to flavivirus-derived determinants, as none of a range of determinants from endogenous mouse-derived sequences, similar to the MVE-determinants, were recognized. Neither were cells infected with a number of unrelated viruses recognized. These results raise the paradox that virus-immune Tc cell responses, which are mostly directed against only a few "immunodominant" viral determinants, are remarkably peptide cross-reactive.

Evaluation of ELISA-based sero-diagnosis of dengue fever in travelers

Diagnosis of dengue virus infection in travelers is often based on commercially available ELISA-based serological assays and not on the more difficult and costly procedures of Hemagglutination inhibition (HI), virus isolation or RT-PCR. These standard assays are not quantitative and are designed to diagnose primary and secondary dengue virus infections by testing for IgG and IgM antibodies. However, cross reactivity between various flaviviruses and the fact that most travelers today are prevaccinated against Japanese encelphalitis (JE) and yellow fever (YF) create a potential problem in such diagnosis. Our study was aimed at measuring the extent of false positive diagnosis in prevaccinated travelers which we have assessed by testing for dengue IgG and IgM antibodies in a group of prevaccinated healthy travelers using the PanBio indirect IgG ELISA and IgM capture ELISA kits. The IgM test was negative in all healthy vaccinees, thus, being highly specific. However, the kit had a disadvantage, which was recognized in other travelers clinically ill with dengue fever (DF), in which the IgM response was detected only 4-8 days after onset of the clinical symptoms. The IgG test yielded 11-17 and 15-44% positives in healthy travelers vaccinated against JE and YF, respectively. We conclude that the specificity of the IgG-ELISA assay in prevaccinated travelers is much lower than in unvaccinated populations. Thus, an IgG-positive results in a vaccinated traveler and IgM negative result during the 1st week of the illness period, are both inconclusive.

Does the concurrent administration of an inactivated hepatitis A vaccine influence the immune response to other travelers vaccines?

BACKGROUND

Travelers seeking protection from hepatitis A also often need protection against other infections, prevalent at their destinations.

METHODS

A total of 396 volunteers received not only a hepatitis A vaccine but also either a vaccine against polio, hepatitis B, diphtheria, tetanus, yellow fever, Japanese encephalitis, typhoid fever or rabies according to their individual needs. We investigated the potential influence of the hepatitis A vaccination on the immune response to the other travelers vaccines that were administered concurrently.

RESULTS

With seroprotection rates of 100% for yellow fever, Japanese encephalitis and rabies immunization and tetanus boosters our data demonstrate that the concurrent administration of hepatitis A vaccine does not compromise the immune response of these vaccines. Also for oral typhoid, hepatitis B and diphtheria vaccination we did not detect a negative influence of concurrent hepatitis A vaccine administration as compared with respective vaccinations when given alone. Prior to vaccination, more than one third of our subjects lacked protective antibody levels against diphtheria and only 44% of initially seronegative travelers seroconverted to an anti-diphtheria titer > or = 0.01 mIU/mL, supporting a need for an additional dose. Furthermore, only two thirds of the vaccinees tested prior to vaccination were protected against polio type 3, and the seroconversion rate following the administration of oral polio vaccine, was lower for viral type 3 (80%), as has been previously demonstrated in settings without concurrent other vaccinations.

CONCLUSION

No negative effect of concurrent travelers vaccinations on the immune response of a hepatitis A vaccine has been detected in a previous report, and, likewise our data suggest no impairment of the antibody response of these travelers vaccines by the concurrent administration of the hepatitis A vaccine.

Isolation of homologous arbovirus cultures from heterologous mixtures using limit dilution and virus-specific enzyme immunoassays

Viral cultures were identified recently that contained both Kunjin virus and the closely related flavivirus West Nile. The observation that the KUN virus population grew more efficiently in a mosquito cell line (C6/36) while the WN population replicated more effectively in mammalian cells (Vero) allowed enrichment for either virus by culturing the mixture in the appropriate cell line. Limit dilution of the enriched virus preparations was then performed by infecting microtitre cultures with serial ten fold dilutions. Culture wells that contained a pure population of virus were then identified by immunostaining fixed cell monolayers with virus-specific monoclonal antibodies. Subsequent passage of the 'cloned' viruses in either C6/36 or Vero cells and analysis of the infected cultures by specific monoclonal antibody staining, PCR and nucleotide sequencing confirmed the identity of the virus and that in each case an homogeneous virus population had been obtained. This procedure is particularly useful for isolating virus populations from heterogeneous mixtures that fail to develop discrete plaques in infected cell monolayers.

No changes in paired viral antibody titers during the course of acute schizophrenia

Although there have been many studies surveying the prevalence of specific viral antibodies in a large cohort of patients with schizophrenia, changes in antibody levels during the course of acute illness have not been fully investigated. We conducted a preliminary study investigating levels of antibodies to 5 herpesviruses (herpes simplex virus type 1, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus and human herpesvirus type 6) and 6 other viruses (measles, rubella, mumps, influenza A and B and Japanese encephalitis viruses) in paired sera of 8 patients with acute onset or exacerbation of schizophrenia. Assay for specific immunoglobulin M (IgM) antibody was also performed for herpesviruses and mumps. Neither any relevant change in antibody levels nor appearance of specific IgM antibody was observed for any of the viruses in any of the patients investigated. It is unlikely that the active infection or reactivation of these viruses has direct causal relationship to schizophrenia in these patients.

Primary and booster immune responses to SA14-14-2 Japanese encephalitis vaccine in Korean infants

Attenuated SA14-14-2 Japanese encephalitis (JE) vaccine has been administered safely and effectively to more than 100 million children in China since 1988 and recently, licensure of the vaccine in Korea has been sought. In the first clinical evaluation of the vaccine outside of China, we monitored side effects in 84 children and evaluated antibody responses to a single dose given as primary JE vaccination in 68 children, 1-3 years old (mean age 27 months). No significant adverse events were noted. Neutralizing antibodies (geometric mean titer [GMT] of 188) were produced in 96% of the 68 subjects. In 10 other children who previously had been immunized with two or three doses of inactivated JE vaccine, the booster administration of SA14-14-2 vaccine produced an anamnestic response in all, with a GMT of 3378. In a comparison group of 25 children previously immunized with two doses of inactivated vaccine, neutralizing antibody titers were detected in 16 (64%). Viral specific IgM was detected in nine primary vaccinees (13%) but in others, IgM may have declined to undetectable levels in the four week postimmunization sample. Live attenuated SA14-14-2 JE vaccine is a promising alternative to the only commercially available JE vaccine for national childhood immunization programs in Asia.

[Analysis on the immuno-effects of two different Japanese encephalitis virus vaccines]

319 infants aged 5-18 months were divided in to 2 groups and immunized with Japanese encephalitis virus inactivated vaccine and live attenuated vaccine respectively. Under the detection of serum antibody, a 3.76% serum antibody positive rate was revealed before the immunization. However, after the basic immunization the serum positive rates of the two vaccines reached 59.56% and 56.08% respectively but still under the protective level. The infants were then given booster injection one year later. The serum positive rates reached 94.62% and 98.21% respectively 1 month later. When six months after the booster immunization, the positive rates were 72.34% and 94.74% respectively. According to the results, the following immunization order was recommend. For inactivated vaccine: 2 injections are given with an interval of 7-10 days for basic immunization and booster immunization be given in the second and third years. For live attenuated vaccine: one injection is given for basic immunization then booster dose be given in the second year and 4-5 years later.

[Production of purified Japanese encephalitis vaccine from Vero cells with roller bottles]

OBJECTIVE

To study the production process of purified Japanese encephalitis (JE) vaccine from Vero cells cultivated in roller bottles to improve the quality of JE vaccine.

METHODS

The 15 L roller bottles were used for propagation of Vero cells and JE virus, then the virus was inactivated, concentrated, treated by protamine sulphate, purified by sucrose gradient density centrifugation and lyophylized as final product.

RESULTS

Three batches of high quality lyophylized vaccine were produced and the quality control tests of vaccine for human use had been passed.

CONCLUSION

Using roller bottles to cultivate continuous cell line-Vero cells for JE vaccine production is feasible.

Japanese encephalitis virus antibody among normal individuals of Dibrugarh area, upper Assam

In a hospital based study in Dibrugarh upper Assam carried out over a period of one year, 250 normal individuals, were screened for antibody to Japanese encephalitis Virus. 44 individuals (17.6%) showed antibody to JE virus. The highest numbers were found in July and August, each 40%, and lowest in January (4%). The ratio of apparent to inapparent infection in this study was found to be 9.1 : 100, which is lower than reported in Assam earlier, but slightly higher than predicted for India as a whole.

Adverse reactions to Japanese encephalitis vaccine in travellers

Vaccination against Japanese Encephalitis (JE) has been carried out extensively in many Asian countries for the past 20 years. The vaccine was generally considered to be effective and of low reactogenity. However, since 1989 an unusual number of systemic reactions characterized mainly by generalized urticaria and/or angioedema following JE vaccination were reported from Australia, Canada and Denmark, 860 travellers were recruited during a period of 16 months for a prospective study with the aim to investigate the type and incidence of side effects following JE vaccination (JEV) in German travellers. 826 received a primary immunization (2 injections at days 0 and 7-14) and 34 received a single booster injection. A detailed standardized questionnaire was distributed to all vaccinees after the first injection. A total of 509 questionnaires could be evaluated, which represents a return rate of 59.2%. 46% of the vaccinees reported about no adverse events at all. 54% reported about one or more adverse effects. Local reactions at the injection site were observed by 209 vaccinees, while 65 reported about systemic side effects like headache, fever, dizziness and generalized rash. There was no significant difference following first or second injection of the primary immunization or the booster injection, respectively, regarding incidence, severity or type of side effects. 2.2% of the vaccinees reporting reactions sought medical advice and 1.8% were judged unfit for work for an average of 2.2 days. The amount of systemic reactions might indicate a potential hazard of serious anaphylactic reactions. Unlike hepatitis A. Japanese encephalitis is an extremely rare disease in travellers. Therefore, the risk of acquiring the disease when travelling to affected areas without prior immunization should be considered against the risk of developing serious side effects after vaccination. We conclude that JEV should remain restricted to travellers with an increased risk of acquiring JE.

Antigenic analysis of Japanese encephalitis viruses in Asia by using monoclonal antibodies

Based on our previous study using monoclonal antibodies against three Japanese encephalitis (JE) virus strains, Nakayama-RFVL, Beijing 1 and Kamiyama, 25 JE virus strains isolated mainly in Japan and some from Southeast Asia between 1935 and 1979 fell into five antigenic groups, Nakayama, Beijing 1, Kamiyama, Muar and 691004. In the present study, monoclonal antibodies against Muar and 691004 strains were produced to analyze immunological characteristics of JE virus in detail. We obtained the Muar group-specific antibody and three anti-691004 monoclonal antibodies which showed different reactivities. Furthermore, antigenic comparison of the 22 JE virus strains isolated in Asia between 1963 and 1984 was performed by using the 15 monoclonal antibodies characterized by the different reactivities against the above five antigenic groups. Of these 22 strains, the 17 strains reacted with the Kamiyama group-specific monoclonal antibody, but anti-Nakayama, anti-Beijing 1 and anti-Muar group-specific monoclonal antibodies showed no reactivities with any of the strains. This suggested that the currently prevalent JE virus strains in Asia belonged to the Kamiyama group. The other five strains, ThCMP 1982, KE083, KE093, 733913 and Ling, did not react with the above four group-specific monoclonal antibodies, but all except the KE093 strain showed a similar pattern to the Kamiyama strain on the basis of the reactivities against the other 11 antibodies. The KE093 strain isolated from Thailand in 1983 showed immunologically outstanding difference from other strains.

Immunodominant epitopes on the NS1 protein of MVE and KUN viruses serve as targets for a blocking ELISA to detect virus-specific antibodies in sentinel animal serum

Two mosquito-borne flaviviruses, Murray Valley encephalitis (MVE) and Kunjin (KUN), are the aetiological agents of Australian encephalitis. MVE causes a severe and potentially fatal form of the disease while KUN is responsible for only a few relatively mild cases. Therefore it is important that serological tests used in flavivirus surveillance differentiate between infections with these two viruses. However, this has been hampered in the past by the close antigenic relationships between flaviviruses in traditional serological assays. An epitope blocking ELISA using MVE-specific and KUN-specific monoclonal antibodies (mAb) reacting to the non-structural protein NS1 of these viruses and a flavivirus group-specific mAb reacting to the envelope (E) protein was assessed for testing sentinel animals for seroconversion to specific flavivirus infections. Using these assays we were able to detect serum antibodies to a variety of flavivirus in laboratory infected rabbits, and naturally infected chickens and in the case of primary infections, differentiate those caused by KUN or MVE. These assays are now used routinely in our laboratory for testing chicken sera from sentinel flocks in the Kimberley and Pilbara regions of north Western Australia.

Glycosylation and antigenic variation among Kunjin virus isolates

Previous studies have found Kunjin (KUN) virus isolates from within Australia to be genetically homogenous and that the envelope protein of the type strain (MRM61C) was unglycosylated and lacked a potential glycosylation site. We investigated the extent of antigenic variation between KUN virus isolates from Australia and Sarawak using an immunoperoxidase assay and a panel of six monoclonal antibodies. The glycosylation status of the E protein of each virus was also determined by N glycosidase F (PNGase F) digestion and limited sequence analysis. The results showed that KUN viruses isolated within Australia oscillated between three antigenic types defined by two epitopes whose expression was influenced by passage history and host cell type. In contrast an isolate from Sarawak formed a stable antigenic type that was not influenced by passage history and was distinct from all Australian isolates. PNGase F digestions of KUN isolates indicated that 19 of the 33 viruses possessed a glycosylated E protein. Nucleotide sequence of the 5' third of the E gene of selected KUN isolates revealed that a single base change in PNGase F sensitive strains changed the tripeptide N-Y-F (amino acids 154-156 of the published sequence) to the potential glycosylation site N-Y-S. Further analysis revealed that passage history also had a significant influence on glycosylation.

Isolation of Batai virus from sentinel domestic pig from Kolar district in Karnataka State, India

Batai virus was isolated from the blood sample of one sentinel piglet out of 34 used to monitor the activity of the Japanese encephalitis (JE) virus at Madikere village in Kolar district, Karnataka State, India. This is the first report of the isolation of Batai virus from a mammal.

Kinetics and cross-reactivity of the virus-specific antibody-forming cells in mice during primary and secondary infection with Japanese encephalitis virus and related flaviviruses

A modified antibody-forming cell assay was used to enumerate splenocytes secreting antibodies to Japanese encephalitis (JE) virus and four other flaviviruses in infected cells as the target antigens. The optimal viral antigen expression for the assay was standardized in the infected cells for each virus and the incubation time varied depending of the cell line and the virus. The kinetics of response of JE virus-infected mice readily showed IgG isotype switching. Antibody-forming splenocytes of mice primed or boosted with one flavivirus could distinguish, in variable proportions, the homologous virus antigen from heterologous ones depending on the serocomplex of the virus. Antibody-forming cells from flavivirus-infected mice were flavivirus specific as evidenced by the lack of recognition of Getah virus (alphavirus) antigen. After JE virus-infected mice were cross-primed with another flavivirus, the IgG-forming cell response resembled the secondary response to both viruses but had higher affinity to JE virus than to the cross-priming virus.

Avipox virus-vectored Japanese encephalitis virus vaccines: use as vaccine candidates in combination with purified subunit immunogens

An avipox virus, canarypox (ALVAC), which is naturally host-range restricted, was used to construct recombinants encoding the Japanese encephalitis virus (JEV) prM, E and NS1 genes (vCP107) and prM and E genes (vCP140). Mice immunized with these recombinant viruses produced JEV neutralizing antibodies and were protected from lethal JEV challenge. Protection was also observed in mice immunized with a subunit vaccine candidate, consisting of extracellular particles (EPs; RNA-free subviral membrane vesicles containing prM/M and E proteins) derived from HeLa cell cultures infected with a JEV-vaccinia recombinant. Mice primed with vCP107 and boosted with EPs had higher antibody levels than mice immunized twice with EPs alone, although the levels were comparable to that obtained in mice immunized twice with the recombinant virus. Mice immunized with a mixture of recombinant virus (vCP107) plus EPs had neutralizing antibody titres higher than mice immunized with the recombinant virus or EPs alone.