Production and characterization of biologicals for disease diagnosis and pathological evaluation of elephant endotheliotropic herpesvirus (EEHV)

Elephant endotheliotropic herpesviruses (EEHV) belong to the family Herpesviridae and cause a highly fatal hemorrhagic infection in elephants. EEHV poses a global threat to the already endangered elephant population. Since EEHV is a non-cultivable virus, there is a scarcity of specific diagnostics, therapeutics, and vaccines. In this study, our objective was to develop biologicals for diagnosis and pathological studies against the most prevalent EEHV1A/1B. We expressed two truncated fragments of the DNA polymerase, glycoprotein B (gB), and glycoprotein (gL) of EEHV in the prokaryotic system. Hyperimmune serum against the purified antigens was raised in rabbits and guinea pigs. We validated the reactivity of this hyperimmune serum using western blotting, ELISA, and immune-histochemistry on known positive infected tissues. Samples collected from 270 animals across various states in India were evaluated with these biologicals. The raised antibodies successfully demonstrated virus in immune-cytochemistry. Additionally, all known positive samples consistently exhibited significant inhibition in the OD values when used in the competitive format of ELISA across all four antigens when compared to the serum collected from known negative animals. An apparent sero-prevalence of 10 % was observed in the randomly collected samples. In summary, our study successfully developed and validated biologicals that will be invaluable for EEHV diagnosis and control.