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.
Tewari
D
D
Department of Veterinary Medicine, University of Cambridge, U.K.
Gibson
J S
JS
Slater
J D
JD
O'Neill
T
T
Hannant
D
D
Allen
G P
GP
Field
H J
HJ
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