Characterization of hepatitis E-specific cell-mediated immune response using IFN-γ ELISPOT assay

Abstract

In developing countries, hepatitis E (HEV) and hepatitis A (HAV) are the major causes of acute viral hepatitis with similar fecooral modes of transmission. In contrast to the high seroprevalence of hepatitis A infection, a low seroprevalence of HEV among children in endemic areas has been reported. These data suggest the possibility that silent HEV infection is undiagnosed by the current available methods. Many of the serological tests used for HEV diagnosis have poor specificity and are unable to differentiate among different genotypes of HEV. Moreover, the RT-PCR used for HEV isolation is only valid for a brief period during the acute stage of infection. Cell-mediated immune (CMI) responses are highly sensitive, and long lasting after sub-clinical infections as shown in HCV and HIV. Our objective was to develop a quantitative assay for cell-mediated immune (CMI) responses in HEV infection as a surrogate marker for HEV exposure in silent infection. Quantitative assessment of the CMI responses in HEV will also help us to evaluate the role of CMI in HEV morbidity. In this study, an HEV-specific interferon-gamma (IFN-γ) ELISPOT assay was optimized to analyze HEV-specific CMI responses. We used peripheral blood mononuclear cells (PBMC) and sera from experimentally infected chimpanzees and from seroconverted and control human subjects to validate the assay. The HEV-specific IFN-γ ELISPOT responses correlated strongly and significantly with anti-HEV ELISA positive/negative results (rho=0.73, p=0.02). Moreover, fine specificities of HEV-specific T cell responses could be identified using overlapping HEV ORF2 peptides.

Host Immune Status and Response to Hepatitis E Virus Infection

“…6 cells. The authors suggested that the robust IgG antibody and cell-mediated responses detected in one well-studied U.S. patient who had traveled to Egypt 2 months prior to the study were likely due to (re)exposure in adulthood rather than to persistent cellular immunity from childhood (249).…”

Age-related changes in magnitude and diversity of cross-reactive CD4+ T-cell responses to the novel pandemic H1N1 influenza hemagglutinin

“…Thus, in agreement with a prior study [17], these longer peptides preferentially stimulated CD4 ϩ T cells. The secretion of interferon-␥ (IFN-␥) was detected by ELISPOT assays [18] Cultured lymphocytes were added at 5 ϫ 10 4 cells/well in quadruplicate and stimulated with peptide pools or media containing identical DMSO concentration for 18 hours at 37ЊC. Phytohemagglutinin (PHA; Sigma, St. Louis, MO) at 5 g/ml was used as a positive control.…”

Autochthonous Hepatitis E Virus Infections: A New Transfusion-Associated Risk?

“…Novel techniques, such as an HEV-specific interferon-gamma (IFN-γ) ELISPOT that measure HEV-specific cell-mediated immune responses are not yet suitable for routine use [76]. This assay might provide a better measure of prior HEV exposure than seroprevalence studies.…”