Modulation of the serological response of specific pathogen-free (EHV-free) foals to EHV-1 by previous infection with EHV-4 or a TK-deletion mutant of EHV-1.
EHV-1 was inoculated into specific pathogen-free (SPF) foals in order to study uncomplicated primary responses. Infection resulted in a strong serological response recognizing EHV-1-specific antigens; this contrasts with a previous publication where a weak response was recorded in SPF animals. Antibodies to EHV-1 were readily detected by four techniques (virus neutralization, complement fixation, Western blots and immune precipitation), yet there was comparatively little cross-reaction to EHV-4 target antigen. Re-inoculation with the same virus strain stimulated antibodies to EHV-1 but no additional antigens were recognized and antibodies cross-reacting with EHV-4 antigens were not enhanced. Having characterized the uncomplicated primary response to EHV-1 in SPF foals, further animals were exposed to either EHV-4 or a thymidine kinase-deficient mutant of EHV-1 prior to challenge with w/t EHV-1 to investigate how these infections might modulate the immune responses to EHV-1 or 4. Primary inoculation with EHV-4 or with a thymidine kinase-deficient mutant of EHV-1 produced productive infections as evidenced by virus shedding and pyrexia. In both these cases, however, in contrast to that with w/t EHV-1, the serological response was very weak. Re-infection of foals primed with either EHV-4 or TK-deficient EHV-1 with w/t EHV-1 resulted in a strong response to EHV-1 antigens detected by all four methods. In addition, in the foals given a primary inoculation with EHV-4, superinfection with EHV-1 resulted in a strong cross-reactive response to EHV-4 target antigens. The relevance of these observations to the interpretation of previously reported serological responses to EHVs in SPF and naturally reared animals is discussed.
Department of Veterinary Medicine, University of Cambridge, U.K.
D
D
Tewari
J S
JS
Gibson
J D
JD
Slater
T
T
O'Neill
D
D
Hannant
G P
GP
Allen
H J
HJ
Field
D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis / Q000276:immunology; D000956:Antigens, Viral / Q000276:immunology; D015153:Blotting, Western; D002460:Cell Line; D003429:Cross Reactions; D006023:Glycoproteins / Q000276:immunology; D006564:Herpesviridae / Q000276:immunology; D006566:Herpesviridae Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D004861:Herpesvirus 1, Equid / Q000201:enzymology / Q000276:immunology* / Q000302:isolation & purification; D006734:Horse Diseases / Q000276:immunology* / Q000382:microbiology; D006736:Horses; D011817:Rabbits; D013047:Specific Pathogen-Free Organisms; D013937:Thymidine Kinase / Q000378:metabolism
D000914:Antibodies, Viral; D000956:Antigens, Viral; D006023:Glycoproteins; D013937:Thymidine Kinase