Hepatitis Division, National Institute of Virology, Microbial Containment Complex, Sus road, Pashan, Pune-411021, India.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Hepatitis E virus (HEV) is a major cause of waterborne acute viral hepatitis in developing countries. HEV infection leads to fatal manifestations in about 20% pregnant women. A recombinant ORF2 protein-based vaccine underwent a successful phase-III clinical trial in Nepal recently. We have developed a candidate vaccine with 150 aa. ORF2 peptide giving promising results in challenge studies in rhesus monkeys, which merits further evaluation in clinical trials. Currently we use recombinant ORF2-based ELISAs for anti-HEV IgM and IgG detection. Aim was to develop a test to differentiate between antibodies induced with vaccine and natural HEV infection. For that 123 aa ORF3 protein and 1–111 aa peptide of ORF2 (N-ORF2) (not the part of candidate vaccine) were made. Reactivity of human serum samples a)from acute viral hepatitis patients representing 3 outbreaks (n=150), b) sporadic non-A non-B hepatitis cases (n=132) and c) sequential serum samples of two rhesus monkeys experimentally infected with genotype-1 HEV (from 0–8 weeks post infection) were evaluated in ELISA. Overall positivity of human serum samples in ELISA was: i) ORF2: IgM-40.77% (115/242) and IgG- 71.98% (203/242); ii) N-ORF2: IgM-11.34% (32/242) and IgG-24.82% (70/242); iii) ORF3: IgM-17.37% (49/242) and IgG-52.83% (149/242). Anti-HEV IgG testing with ORF3 antigen would be method of choice in detecting HEV infections in vaccinated individuals. Experimentally infected monkey sera showed excellent correlation in anti-HEV IgG detection with ORF2 and N-ORF2 antigens. However reactivity was very poor with ORF3. Hence in monkeys N-ORF2 based ELISA would be used.
