Evaluation of a computer-assisted, kinetics-based enzyme-linked immunosorbent assay for detection of coronavirus antibodies in cats

Abstract

A computer-assisted, kinetics-based enzyme-linked immunosorbent assay was adapted for the detection of coronavirus antibodies in feline serum. An alkaline antigen diluent (carbonate-bicarbonate buffer, pH 9.6) used in initial experiments produced diffuse, nonspecific color reactions in both viral and control antigen cuvettes which were correlated, paradoxically, with coronavirus antibody levels in test sera. These interfering reactions were minimized by use of lower-pH antigen diluents such as water and phosphate-buffered saline. Background kinetics-based enzyme-linked immunosorbent assay reactivity directed against a noncoronaviral component of antigen tissue culture fluids could then detected in numerous sera, particularly in samples with lower titers. Much of this reactivity was shown to be associated with bovine gamma globulins in cell culture fluid. It was not serum lot or species specific, since a variety of bovine serum lots as well as individual lots of serum from other mammalian and avian species reacted. Reactivity was markedly reduced when cells for antigen preparation were grown in gamma globulin-free bovine serum. Generation of corrected slope values from the kinetics-based enzyme-linked immunosorbent assay made it possible to correct for residual background reactivity in individual test sera and thus eliminate a potentially major source of false-positive reactions. Collectively, these studies indicated that the control of nonspecific reactivity in feline coronavirus serology is absolutely essential to obtain useful estimates of specific antibody responses.

Feline infectious peritonitis

“…FCoV is distributed worldwide in household and wild cats [27,28]. The virus is endemic especially in environments in which many cats are kept together in a small space (eg, catteries, shelters, pet stores).…”

Transmissibility of the contagious equine metritis organism for the cat

“…Sahu et al [29] found the ELISA markedly superior to the complement-fixation and certain other serological tests for the detection of CEM-infected mares. However, even using the kinetics-based ELISA or KELA system, which is a highly sensitive technique for quantitation of serum antibody levels [17], very little evidence was found to indicate that the cats in this study, even those that became infected, responded serologically on single or repeated exposure to CEMO.…”

“…The KELA procedure was essentially similar to that described by Jacobson et al [16] and Barlough et al [17]. Assays were conducted on Gilford EIA-PR50's (Gilford Instruments, Inc., Oberlin, OH) interfaced with a PDP11/34A computer (Digital Instru-ment Corp, Maynard, MA).…”

An enzyme-linked immunosorbent assay using canine coronavirus-infected CRFK cells as antigen for detection of anti-coronavirus antibody in cat

“…globulin associated) of serum samples to the antigen preparations is often an additional problem. It has been described that most but not all of false-positive reactions are attributable to recent vaccination [17,27,30,31]. Some kinds of cell culture vaccines prepared for use in cats have been commonly utilized in Japan as well.…”