Evaluation of Viral Migration of Different Variants of Equid Alphaherpesvirus 1 in the Central Nervous System of Hamsters by Immunohistochemistry

Abstract

The intranasal inoculation of equid alphaherpesvirus1 (EHV-1) Brazilian variants A4/72, A9/92, A3/97, Iso72/10 and the Argentine variant AR4 in a Syrian hamster model Mesocricetus auratus induced severe encephalitis. Clinical signs included weight loss, lethargy, somnolence, anorexia, and intense salivation two days post-inoculation (dpi), followed by neurological signs such as loss of proprioception, walking in circles, spastic paralysis, seizures, recumbency and death at 3 rd dpi (A9/92 and A4/72 variants) and 4 th dpi. Respiratory signs such as dyspnea and serosanguinous nasal discharge were also observed. Histopathological changes in brain included mixed inflammatory infiltrate with predominance of mononuclear cells, neuronal degeneration, liquefactive necrosis, hemorrhagic foci, leptomeningitis, perivascular edema, mononuclear infiltration, and perivascular cuffing. Immunohistochemical examination showed viral replication in neurons restrict predominantly to olfactory bulb and frontal cortex (variants AR4 and A3/97) and in groups of cells from distant regions, such as the caudal diencephalon and rostral mesencephalon (variants Iso72/10) and absence of viral antigen labeling of variants A9/92 and A4/72 despite these variants were the most neurovirulent, so new experiments not staggered in days but in hours post inoculation are needed to better understand the viral migration of these variants.