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The development of an enzyme linked immunosorbent assay for the detection of
antibodies to equid herpesvirus type 1 in horse sera.
Bachelor of Philosophy
1983
Peter Dudley Jolly
Abstract
An Enzyme Linked Immunosorbent Assay (ELISA) was developed to detect
antibodies against equid herpesvirus type (EHV-1) in equine sera. Several methods of
ELISA antigen preparation were examined in an effort to find the one most suitable
for seroepidemiological purposes. The antigens were compared by titrating them
against 32 foal sera with wide ranging serum neutralization test (SNT) titres to the
same strain of EHV-1. ELISA antigen prepared by polyethylene glycol precipitation
of a crude EHV-1 infected cell culture extract was found to perform similarly to
highly purified EHV-1 virus.
Logit transformations of individual serum titration curves were used to titre sera and
to compare titration curves generated by each antigen. Significant differences
(P<0.01) were found between slopes of titration curves generated by each antigen
preparation, however end point titres showed a high degree of correlation e.g., 98.9%
for crude vs highly purified virus extracts. The use of highly purified virus as ELISA
antigen produced antibody titres that showed the best correlation with the SNT, and
that best differentiated neutralising antibody titres. However, differences observed
between antigen preparations were small, and for practical reasons such as relative
ease of production, economy, and high yield, the crude infected cell culture extract
was chosen for subsequent use.
Comparisons of ELISA and SNT antibody titres over a larger number of foal sera
showed a high correlation (71.9%), with ELISA titres being approximately 100 to
100,000 times greater than those of SNT. Approximately one-half of the sera
negative by SNT were positive by ELISA, but the majority of these had low ELISA
titres. No sera tested were negative by ELISA and positive by SNT. It was concluded
that the ELISA developed in this study was ahighly sensitive and specific method for
the detection of antibodies to EHV-1 in equine sera.