Increase of Kynurenic Acid after Encephalomyocarditis Virus Infection and Its Significances

The moust symptoms of piglets infected with Encephalomyocarditis virus (EMCV) are related to breeding difficulty, circulation insufficiency, depression and occurrence of high lethality. An increase of tryptophan metabolism in the periphery and in the central nervous system (CNS) in human and non-human subjects with inflammatory diseases has been suggested. We investigated an alterations of tryptophan metabolite i.e. kynurenic acid (KYNA) level in the serum of piglets after EMC virus infection. In addition, we investigated the markers of immune stimulation i.e. neopterin and β2-microglobulin.

KYNA was determined by high performance liquid chromatography method, while neopterin and β2-microglobulin by ELISA method. Piglets with an age of 8 weeks were infected intranasal and orally with the EMC virus. Blood samples were collected before virus inoculation at day 0 (control) and at 1, 2, 3 and 4 days post inoculation (DPI) and piglets as control subjects were used, too.

In EMCV infected piglets we observed a time dependent alteration of investigated parameters. KYNA level increased significantly and at 3 DPI was 341% of CO, p<0.001 and at 4 DPI an enhancement was 242% of CO, p<0.001, respectively. Neopterin increased moderately after EMCV infection and at 4 DPI was 130% of CO, p<0.05. Serum β2-microglobulin was slightly lowered and at 4 DPI was 86% of CO, p<0.05. Present data indicate an marked increase of kynurenine metabolism in the periphery after EMCV infection and an moderate activation of immune system.

A marked increase of KYNA and a moderate enhancement of neopterin indicate sensibility of kynurenine metabolism to EMCV infection. Lowering of ß2-microgobulin might relate to development of events leading to the lethality. We suggest that due to viral infection an increase of KYNA might contribute to the inpairment of organs in the periphery and CNS function and might participate by sudden death.