Cell-mediated immune responses in healthy children with a history of subclinical infection with Japanese encephalitis virus: analysis of CD4+ and CD8+ T cell target specificities by intracellular delivery of viral proteins using the human immunodeficiency virus Tat protein transduction domain

Japanese Encephalitis Virus Persistence in Porcine Tonsils Is Associated With a Weak Induction of the Innate Immune Response, an Absence of IFNγ mRNA Expression, and a Decreased Frequency of CD4+CD8+ Double-Positive T Cells

In humans, Japanese encephalitis virus (JEV) causes a devastating neurotropic disease with high mortality, whereas in pigs, the virus only causes mild symptoms. Besides tropism to the central nervous system, JEV seems to harbor a particular tropism for the tonsils in pigs. This secondary lymphoid organ appears to act as a reservoir for the virus, and we show that it is found up to 21 days post infection at high viral titers. The immune response in the tonsils was studied over time upon intradermal inoculation of pigs. Entry of the virus in the tonsils was accompanied by a significant increase in anti-viral OAS1 and IFNβ mRNA expression. This limited antiviral response was, however, not sufficient to stop JEV replication, and importantly, no IFNγ or innate inflammatory cytokine mRNA expression could be observed. Strikingly, the persistence of JEV in tonsils was also associated with a significant decreased frequency of CD4⁺CD8⁺ double-positive T lymphocytes. Furthermore, it is important to note that JEV persistence in tonsils occurred despite a strong induction of the adaptive immune response. JEV-specific antibodies were found after 6 days post infection in serum, and cell-mediated immune responses upon NS3 restimulation of PBMCs from experimentally infected pigs showed that CD4⁺CD8⁺ double-positive T cells were found to display the most prominent proliferation and IFNγ production among lymphocyte subtypes. Taken together, these results suggest that an inadequate induction of the innate immune response and the absence of an IFNγ antiviral response contribute to the persistence of JEV in the tonsils and is associated with a decrease in the frequency of CD4⁺CD8⁺ double-positive T cells.

Differential expression of circulating microRNAs in serum: Potential biomarkers to track Japanese encephalitis virus infection

Japanese encephalitis is one of the serious vector-borne viral encephalitis diseases found worldwide and poses a major threat to public health. Most Japanese encephalitis virus (JEV) infections are subclinical; only 1: 250 to 1:1000 infected persons develop clinical presentations. Delay in proper diagnosis of JE affects the timeliness of treatment initiation and increases the mortality rate in patients. Therefore, there is an extreme need to develop potential biomarkers, which might improve the diagnosis and can become the basis for development of new therapeutics. The microRNAs (miRNAs/or miRs) are small noncoding RNAs of 17-24 nucleotides that are known to regulate about 60% of human genes. Although miRNAs have been found to regulate various aspects of innate and adaptive immune responses, less information on circulating miRNAs in JE is known. The study of JEV infected human serum miRNAs will provide novel information for the diagnosis of JE as well as for the improvement of disease outcome. Total RNA, including miRNA, was extracted from serum followed by the complementary DNA (cDNA) synthesis by using sequence-specific primers. cDNA was amplified using target-specific TaqMan MicroRNA Assay. Real-time polymerase chain reaction data was normalized using both exogenous (cel-miR-39) and endogenous (hsa-miR-93) controls. We have found significantly altered expression of miR-155 and miR-21 in serum of JEV infected patients as compared to healthy controls, revealing their role as a a noninvasive biomarker in JE. A significant correlation between miRNAs and JE was observed that offers the basis for miRNAs to serve as a new component to develop possible therapeutic strategies for JE in near future.

Blocking HSV-1 glycoprotein K binding to signal peptide peptidase reduces virus infectivity in vitro and in vivo

HSV glycoprotein K (gK) is an essential herpes protein that contributes to enhancement of eye disease. We previously reported that gK binds to signal peptide peptidase (SPP) and that depletion of SPP reduces HSV-1 infectivity in vivo. To determine the therapeutic potential of blocking gK binding to SPP on virus infectivity and pathogenicity, we mapped the gK binding site for SPP to a 15mer peptide within the amino-terminus of gK. This 15mer peptide reduced infectivity of three different virus strains in vitro as determined by plaque assay, FACS, and RT-PCR. Similarly, the 15mer peptide reduced ocular virus replication in both BALB/c and C57BL/6 mice and also reduced levels of latency and exhaustion markers in infected mice when compared with control treated mice. Addition of the gK-15mer peptide also increased the survival of infected mice when compared with control mice. These results suggest that blocking gK binding to SPP using gK peptide may have therapeutic potential in treating HSV-1-associated infection.

Signal peptide peptidase (SPP) and HSV-1 glycoprotein K (gK) are essential genes in the host and virus, respectively. SPP and gK genes are both highly conserved. Previously we reported that gK binding to SPP is important for virus infectivity in vitro and in vivo. In this study we have identified the gK binding site to SPP and have shown that a gK peptide that blocks gK binding to SPP can block HSV-1 infectivity in vitro and in vivo using different strains of virus and mice. Thus, the ability of this peptide to block gK binding to SPP may be a useful tool to control HSV-1-induced eye disease in patients with herpes stromal keratitis (HSK).

Japanese Encephalitis Vaccines

Purpose of review

As an eminently vaccine-preventable disease, encephalitis caused by Japanese encephalitis virus (JEV) has attracted an unusually high degree of attention from those seeking to develop viral vaccines. Since the 1950s, all types of JEV vaccines including inactivated, recombinant and live attenuated ones have been licensed. As an example of an extremely successful endeavour, the time is ripe for reviewing the development of JEV vaccines and probing the reasons behind their uniform success.

Recent findings

Vaccines against JEV have come a long way since the first licensing in the mid-1950s of the mouse brain-grown-inactivated virus preparations, to the present day live-attenuated virus vaccines. A survey of the various inactivated and live vaccines developed against JEV provides a striking insight into the impressive safety and efficacy of all the vaccines available to prevent encephalitis from JEV. This review juxtaposes studies to understand naturally acquired immunity against JEV that have mostly been published post-2000, compares these with those elicited by vaccines and highlights the paucity of data on cell-mediated immune responses elicited by JEV vaccines.

Summary

This article not only seeks to make available the immense salient literature on this endeavour in one collection, but also queries the basis for the remarkable success of JEV vaccines, not least of which may be the ease of protecting against encephalitis caused by JEV. To conclude, the true test of the ingenuity of those dedicated to the pursuit of viral vaccines would be success against viral diseases such as HIV-AIDS and dengue that pose a far greater challenge to scientists.

Human T cell responses to Japanese encephalitis virus in health and disease

Japanese encephalitis (JE) virus (JEV) is an important cause of encephalitis in children of South and Southeast Asia. However, the majority of individuals exposed to JEV only develop mild symptoms associated with long-lasting adaptive immunity. The related flavivirus dengue virus (DENV) cocirculates in many JEV-endemic areas, and clinical data suggest cross-protection between DENV and JEV. To address the role of T cell responses in protection against JEV, we conducted the first full-breadth analysis of the human memory T cell response using a synthetic peptide library. Ex vivo interferon-γ (IFN-γ) responses to JEV in healthy JEV-exposed donors were mostly CD8(+) and targeted nonstructural (NS) proteins, whereas IFN-γ responses in recovered JE patients were mostly CD4(+) and targeted structural proteins and the secreted protein NS1. Among patients, a high quality, polyfunctional CD4(+) T cell response was associated with complete recovery from JE. T cell responses from healthy donors showed a high degree of cross-reactivity to DENV that was less apparent in recovered JE patients despite equal exposure. These data reveal divergent functional CD4(+) and CD8(+) T cell responses linked to different clinical outcomes of JEV infection, associated with distinct targeting and broad flavivirus cross-reactivity including epitopes from DENV, West Nile, and Zika virus.

Design and evaluation of a polytope construct with multiple B and T epitopes against Tembusu virus infection in ducks

Tembusu virus (TMUV) is a newly emerging pathogenic flavivirus that is causing massive economic loss in Chinese poultry industry; until now, there is no effective vaccine or drug for its prevention. Epitope-based vaccination is a promising approach to achieve protective immunity and to avoid immunopathology. In present study, based on in silico epitope selection, we optimized and proposed a polytope DNA vaccine (pVAX1-rTEM) consisting B-cell and T cell epitopes from the TMUV envelope (E) protein. The immunogenicity and protective efficacy of constructed polytope DNA vaccine was assessed by in vitro and in vivo experiments. In in vitro assays, the expressed pVAX1-rTEM showed reactivity with Tembusu positive serum. Its protective efficacy against TMUV infection was evaluated in ducks. The results showed that pVAX1-rTEM was highly immunogenic and could elicit high titer neutralizing antibodies and cell-mediated immune responses. These results indicate that pVAX1-rTEM may be a promising candidate vaccine for prevention of TMUV infection.

Japanese encephalitis: development of new candidate vaccines

Japanese encephalitis (JE) is the most common form of viral encephalitis that appears in the form of frequent epidemics of brain fever throughout Southeast Asia, China and India. The disease is caused by a Flavivirus named Japanese encephalitis virus that is spread to humans by mosquitoes. An internationally approved mouse brain-derived inactivated vaccine has been available that is relatively expensive, gives immunity of uncertain duration and is not completely safe. Cell culture-derived inactivated and attenuated JE vaccines are in use in China, but these are not produced as per the norms acceptable in most countries. Several new promising JE vaccine candidates have been developed, some of which are under different stages of clinical evaluation. These new candidate JE vaccines have the potential to generate long-lasting immunity at low cost.

Pathogenic and vaccine strains of Japanese encephalitis virus elicit different levels of human macrophage effector functions

In India, Japanese encephalitis virus (JEV) remains one of the major causative agents of pediatric encephalitis. Macrophages support various neurotropic viruses and influence the immune response. However, the functional status of human macrophages during JEV infection remains unidentified. In this study, we examined the cytokine response and co-stimulatory marker levels in primary human monocyte derived macrophages (MDMs) infected with JE057434 (neurovirulent, primary clinical isolate) or SA14-14-2 (non-neurovirulent, live-attenuated vaccine) JEV strains. We also examined the differential susceptibility of these JEV strains to antiviral effects of interferon and nitric oxide. The results indicate that both JEV strains are capable of inducing various cytokines (type-I IFN, TNFα, IL6 and IL8) and co-stimulatory molecules (CD86 and CD80) in MDMs. However, they varied in replication potential and corresponding interferon sensitivity. SA14-14-2 was highly susceptible to interferon and nitric oxide when compared to JE057434. Thus, reduction in infectious virion production and increased sensitivity of SA14-14-2 towards interferon in MDMs could potentially play a role in limiting viral spread to additional target tissues.

Preclinical and clinical development of YFV 17D-based chimeric vaccines against dengue, West Nile and Japanese encephalitis viruses

Dengue viruses (DENV), West Nile virus (WNV) and Japanese encephalitis virus (JEV) are major global health and growing medical problems. While a live-attenuated vaccine exists since decades against the prototype flavivirus, yellow fever virus (YFV), there is an urgent need for vaccines against dengue or West Nile diseases, and for improved vaccines against Japanese encephalitis. Live-attenuated chimeric viruses were constructed by replacing the genes coding for Premembrane (prM) and Envelope (E) proteins from YFV 17D vaccine strain with those of heterologous flaviviruses (ChimeriVax technology). This technology has been used to produce vaccine candidates for humans, for construction of a horse vaccine for West Nile fever, and as diagnostic reagents for dengue, Japanese encephalitis, West Nile and St. Louis encephalitis infections. This review focuses on human vaccines and their characterization from the early stages of research through to clinical development. Phenotypic and genetic properties and stability were examined, preclinical evaluation through in vitro or animal models, and clinical testing were carried out. Theoretical environmental concerns linked to the live and genetically modified nature of these vaccines have been carefully addressed. Results of the extensive characterizations are in accordance with the immunogenicity and excellent safety profile of the ChimeriVax-based vaccine candidates, and support their development towards large-scale efficacy trials and registration.

The heat shock protein 27 (Hsp27) operates predominantly by blocking the mitochondrial-independent/extrinsic pathway of cellular apoptosis

Heat shock protein 27 (Hsp27) is a molecular chaperone protein which regulates cell apoptosis by interacting directly with the caspase activation components in the apoptotic pathways. With the assistance of the Tat protein transduction domain we directly delivered the Hsp27 into the myocardial cell line, H9c2 and demonstrate that this protein can reverse hypoxia-induced apoptosis of cells. In order to characterize the contribution of Hsp27 in blocking the two major apoptotic pathways operational within cells, we exposed H9c2 cells to staurosporine and cobalt chloride, agents that induce mitochondria-dependent (intrinsic) and -independent (extrinsic) pathways of apoptosis in cells respectively. The Tat-Hsp27 fusion protein showed a greater propensity to inhibit the effect induced by the cobalt chloride treatment. These data suggest that the Hsp27 predominantly exerts its protective effect by interfering with the components of the extrinsic pathway of apoptosis.

Virus-specific cytolytic antibodies to nonstructural protein 1 of Japanese encephalitis virus effect reduction of virus output from infected cells

We demonstrate the presence of nonstructural protein 1 (NS1)-specific antibodies in a significant proportion of convalescent-phase human serum samples obtained from a cohort in an area where Japanese encephalitis virus (JEV) is endemic. Sera containing antibodies to NS1 but not those with antibodies to other JEV proteins, such as envelope, brought about complement-mediated lysis of JEV-infected BHK-21 cells. Target cells infected with a recombinant poxvirus expressing JEV NS1 on the cell surface confirmed the NS1 specificity of cytolytic antibodies. Mouse anti-NS1 cytolytic sera caused a complement-dependent reduction in virus output from infected human cells, demonstrating their important role in viral control. Antibodies elicited by JEV NS1 did not cross lyse West Nile virus- or dengue virus-infected cells despite immunoprecipitating the NS1 proteins of these related flaviviruses. Additionally, JEV NS1 failed to bind complement factor H, in contrast to NS1 of West Nile virus, suggesting that the NS1 proteins of different flaviviruses have distinctly different mechanisms for interacting with the host. Our results also point to an important role for JEV NS1-specific human immune responses in protection against JE and provide a strong case for inclusion of the NS1 protein in next generation of JEV vaccines.

Evaluation of Japanese encephalitis virus DNA vaccine candidates in rhesus monkeys [Macaca mulatta]

We have previously described DNA vaccine candidates against Japanese encephalitis virus (JEV) that were immunogenic in mice. Present study was conducted to evaluate their immunogenicity in rhesus monkeys (Macaca mulatta) and compare it with the commercial mouse brain-derived, formalin-inactivated vaccine. Groups of four monkeys were immunized with either pMEa (expressing the anchored form of the envelope protein along with the pre-membrane protein of JEV) or pMEs (expressing the secretory form of the envelope protein along with pre-membrane protein of JEV) by intra-muscular (IM, using needle) or intra-dermal (ID, using gene gun) routes. Following primary immunization with 1mg plasmid DNA given IM, or 5 microg plasmid DNA given ID, the monkeys were boosted after 1 and 2 months with 0.5mg DNA given IM or 5 microg DNA given ID, and observed for a period of 6 months. After the second booster, most of the monkeys sero-converted and developed JEV neutralizing antibodies, albeit of low titer. Importantly however, following a sham challenge with the mouse brain-derived inactivated JEV vaccine given 6 months after immunization, the neutralizing antibody titers rose rapidly indicating a vigorous anamnestic response. Based on the JEV neutralizing antibody response following the vaccination and the extent of anamnestic response generated in the immunized monkeys, plasmid pMEa was superior to pMEs. This study indicates that the JEV candidate DNA vaccine is capable of generating protective levels of JEV neutralizing antibodies in rhesus monkeys and prime the immune system effectively against a subsequent exposure to JEV.

The memory T cell response to West Nile virus in symptomatic humans following natural infection is not influenced by age and is dominated by a restricted set of CD8+ T cell epitopes

We examined the West Nile virus (WNV)-specific T cell response in a cohort of 52 patients with symptomatic WNV infections, including neuroinvasive and non-invasive disease. Although all virus proteins were shown to contain T cell epitopes, certain proteins, such as E, were more commonly targeted by the T cell response. Most patients exhibited reactivity toward 3-4 individual WNV peptides; however, several patients exhibited reactivity toward >10 individual peptides. The relative hierarchy of T cell reactivities in all patients showed a fixed pattern that was sustained throughout the 12-mo period of the current study. Surprisingly, we did not observe any relationship between age and either the breadth or magnitude of the T cell response following infection. We also did not observe a relationship between disease severity and either the breadth or magnitude of the T cell response. The T cell epitopes were distributed in a non-random fashion across the viral polyprotein and a limited number of epitopes appeared to dominate the CD8(+) T cell response within our cohort. These data provide important new insight into the T cell response against WNV in humans.

Evaluation of recombinant Kunjin replicon SIV vaccines for protective efficacy in macaques

Persistent gag-specific T cell immunity would be a useful component of an effective HIV vaccine. The Flavivirus Kunjin replicon was previously engineered to persistently express HIV gag and was shown to induce protective responses in mice. We evaluated Kunjin replicon virus-like-particles expressing SIVgag-pol in pigtail macaques. Kunjin-specific antibodies were induced, but no SIV-specific T cell immunity were detected. Following SIVmac251 challenge, there was no difference in SIV viremia or retention of CD4 T cells between Kunjin-SIVgag-pol vaccine immunized animals and controls. An amnestic SIV gag-specific CD8 T cell response associated with control of viremia was observed in 1 of 6 immunized animals. Refinements of this vector system and optimization of the immunization doses, routes, and schedules are required prior to clinical trials.

Conserved amino acids 193–324 of non-structural protein 3 are a dominant source of peptide determinants for CD4+ and CD8+ T cells in a healthy Japanese encephalitis virus-endemic cohort

Our earlier identification of the non-structural protein 3 (NS3) of Japanese encephalitis virus (JEV) as a dominant CD4+ as well as CD8+ T cell-eliciting antigen in a healthy JEV-endemic cohort with a wide HLA distribution implied the presence of several epitopes dispersed over the length of the protein. Use of various truncated versions of NS3 in lymphocyte stimulation and interferon (IFN)-γ secretion assays revealed that amino acids (aa) 193–324 of NS3 were comparable with, if not superior to, the full-length protein in evoking Th1 responses. The potential of this 14·4 kDa stretch to stimulate IFN-γ production from both subtypes of T cells in a manner qualitatively and quantitatively similar to the 68 kDa parent protein suggested the presence within it of both class I and II epitopes and demonstrated that the entire immunogenicity of NS3 was focused on aa 193–324. Interestingly, this segment contained five of the eight helicase motifs of NS3. Analysis of variability of the NS3 protein sequence across 16 JEV isolates revealed complete identity of aa 219–318, which is contained within the above segment, suggesting that NS3-specific epitopes tend to cluster in relatively conserved regions that harbour functionally critical domains of the protein.