IMMUNOHISTOCHEMICAL IDENTIFICATION OF CAPRINE ARTHRITIS-ENCEPHALITIS VIRUS IN PARAFFIN-EMBEDDED SPECIMENS FROM NATURALLY INFECTED GOATS

The expression of caprine arthritis-encephalitis virus capsid protein was studied in seropositive naturally infected asymptomatic goats (10) , seropositive naturally infected encephalitic kids (12) and goats (4) , and noninfected control goats (3). Rabbit antiserum to recombinant v iral capsid and matrix proteins were used in a biotin-streptavidin-alk aline phosphatase complex immunohistochemical method on sections of fo rmalin-and ethanol-fixed tissue specimens. Macrophages in inflamed are as of the lung (8/12), in the brain (5/16), and in the spinal cord (4/ 16) from encephalitic animals harbored viral antigens, as revealed by immunohistochemistry and use of a capsid protein-specific antiserum. A ltogether 12/16 encephalitic animals tested positive for viral antigen . Viral antigens were found in 5/10 seropositive asymptomatic goats in macrophages located in the lung (3), the udder (1), and the medulla o f lymph nodes (4). None of the control animals tested positive for vir al antigen. Ethanol fixation showed highest sensitivity, and the lowes t antigen concentration that revealed a positive signal discernible fr om background was twofold higher in ethanol-fixed specimens than in fo rmalin-fixed specimens. The evaluation was performed on artificial ant igen substrates embedded with defined concentrations of recombinant vi ral capsid protein. Immunohistochemistry is a valuable supplement to t he methods presently available for diagnosis in cases suspicious of ca prine arthritis-encephalitis.