Cellular Immune Responses to Live Attenuated Japanese Encephalitis (JE) Vaccine SA14-14-2 in Adults in a JE/Dengue Co-Endemic Area.

BACKGROUND: Japanese encephalitis (JE) virus (JEV) causes severe epidemic encephalitis across Asia, for which the live attenuated vaccine SA14-14-2 is being used increasingly. JEV is a flavivirus, and is closely related to dengue virus (DENV), which is co-endemic in many parts of Asia, with clinically relevant interactions. There is no information on the human T cell response to SA14-14-2, or whether responses to SA14-14-2 cross-react with DENV. We used live attenuated JE vaccine SA14-14-2 as a model for studying T cell responses to JEV infection in adults, and to determine whether these T cell responses are cross-reactive with DENV, and other flaviviruses. METHODS: We conducted a single arm, open label clinical trial (registration: clinicaltrials.gov NCT01656200) to study T cell responses to SA14-14-2 in adults in South India, an area endemic for JE and dengue. RESULTS: Ten out of 16 (62.5%) participants seroconverted to JEV SA14-14-2, and geometric mean neutralising antibody (NAb) titre was 18.5. Proliferation responses were commonly present before vaccination in the absence of NAb, indicating a likely high degree of previous flavivirus exposure. Thirteen of 15 (87%) participants made T cell interferon-gamma (IFNγ) responses against JEV proteins. In four subjects tested, at least some T cell epitopes mapped cross-reacted with DENV and other flaviviruses. CONCLUSIONS: JEV SA14-14-2 was more immunogenic for T cell IFNγ than for NAb in adults in this JE/DENV co-endemic area. The proliferation positive, NAb negative combination may represent a new marker of long term immunity/exposure to JE. T cell responses can cross-react between JE vaccine and DENV in a co-endemic area, illustrating a need for greater knowledge on such responses to inform the development of next-generation vaccines effective against both diseases. TRIAL REGISTRATION: clinicaltrials.gov (NCT01656200).

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.

Innate immune mechanisms in Japanese encephalitis virus infection: effect on transcription of pattern recognition receptors in mouse neuronal cells and brain tissue.

Very little information is available on the role of innate immune mechanisms in Japanese encephalitis virus (JEV) infection. This study was designed to investigate the role of all Pattern Recognition Receptors (PRRs) in JEV infection in a mouse neuronal cell line in comparison to events that occur in vivo, using JEV infected suckling and adult mice. Analysis of mRNA expression was carried out using RT-PCR for detection of PRR genes and their downstream pathway genes, while a PCR array technique was used to examine the complete transcription analysis. Amongst the various innate immune receptors, TLR3 gene exhibited differential expression in JEV-infected Neuro2a, in suckling mice and adult mouse brain cells but not in uninfected control cells. The downstream events of TLR3 were confirmed by increased mRNA expression of IRF3 and interferon-ß in JEV-infected Neuro2a cells and suckling mice brain tissue. To confirm the functional significance of this observation, TLR3 gene silencing experiments were carried using specific siRNA in Neuro2a cells. The results revealed a significant enhancement of JEV replication in TLR3 gene silenced JEV-infected Neuro2a cells, thereby suggesting that TLR3 serves a protective role against JEV. The expression levels of other PRRs varied. JEV-infected adult mice showed significant upregulation of TLR2 and MDA5 as compared to JEV-infected suckling mice and Neuro2a cells. In addition, upregulation of Myd88 and IRF7 was also noted in adult mice. These observations, coupled with the fact that adult mice infected with JEV exhibited longer survival rates, suggests that the host antiviral TLR2 response seen in adult mice was eventually countered by the virus by using MDA5 receptor. Our findings suggest that different PRRs appear to be involved in JEV infection in Neuro2a cells and brains of suckling and adult mice.

Diversity of circulating rotavirus strains in children hospitalized with diarrhea in India, 2005-2009.

BACKGROUND: India accounts for 22% of the 453,000 global rotavirus deaths among children <5 years annually. The Indian Rotavirus Strain Surveillance Network provides clinicians and public health partners with valuable rotavirus disease surveillance data. Our analysis offers policy-makers an update on rotavirus disease burden with emphasis on regional shifts in rotavirus strain epidemiology in India. METHODS: Children <5 years requiring hospitalization for acute gastroenteritis were selected from 10 representative hospitals in 7 cities throughout India between November 2005 through June 2009. We used a modified World Health Organization protocol for rotavirus surveillance; stool specimens were collected and tested for rotavirus using enzyme immunoassay and reverse-transcription polymerase chain reaction. RESULTS: A total of 7285 stool specimens collected were tested for rotavirus, among which 2899 (40%) were positive for rotavirus. Among the 2899 rotavirus detections, a G-type could not be determined for 662 (23%) and more than one G type was detected in 240 (8%). Of 1997 (69%) patients with only one G-type, the common types were G1 (25%), G2 (21%), G9 (13%), and G12 (10%). The proportion of rotavirus infections attributed to G12 infections rose from 8% to 39% in the Northern region and from 8% to 24% in the Western region. CONCLUSIONS: This study highlights the large, ongoing burden of rotavirus disease in India, as well as interesting regional shifts in rotavirus strain epidemiology, including an increasing detection of G12 rotavirus strains in some regions. While broad heterotypic protection from rotavirus vaccination is expected based on pre- and post-licensure data from other settings, effectiveness assessments and rotavirus strain monitoring after vaccine introduction will be important.