An Enzyme-Linked Immunosorbent Assay Using Nuclear Antigen for Detection of Feline Herpesvirus 1 Antibody

Abstract

Abstract. To detect antibody against feline herpesvirus 1 (FHV-1) in the sera of cats, the sensitivity and specificity of an enzyme-linked immunosorbent assay (ELISA) using nuclear antigen was investigated. The standardized optical density readings (ODs) of the ELISA obtained by the 1-step serum dilution (1:80) method were compared with the serum neutralization test (SNT) results, with a correlation of 0.993, and with the hemagglutination inhibition (HI) test results, with a correlation of 0.851. The ODs for the ELISA titers were obtained using the serial serum dilution method and were compared with the SNT results, with a correlation of 0.933, and with the HI test results, with a correlation of 0.987. In the experimental infection of 4 specificpathogen-free cats, the results of different serologic tests (SNT and HI) and the ELISA using the serial serum dilution method revealed rapid production of antibodies after inoculation, whereas the ELISA using the onestep serum dilution method indicated that titers increased more slowly. These results indicate that with the present ELISA using nuclear antigen, there are fewer demands on time and labor, making the method convenient for monitoring FHV-1 infection.Feline herpesvirus 1 (FHV-1) was first isolated in 1958. 8 The virus causes upper respiratory disease or, in some cases, keratitis. 33 After clinical manifestations, cats recover from the disease, become subclinical virus carriers, and have recurrent infections. In some cases, kittens are infected by the queen. 17 In catteries, pet shops, pet hotels, etc., where cats are kept in large numbers, the detection of cats with clinical manifestations or inapparent FHV-1 infection and the postvaccination antibody level are considered important for the control and prevention of the disease.The serum neutralization test (SNT) is the most common serologic test used for the detection of FHV-1-infected cats, 3,7,9,31,32 but the serum neutralizing antibody to FHV-1 is difficult to detect by conventional SNT because of the poor immunogenicity of FHV-1. SNTs have been somewhat improved by the addition of complement. These tests either have detected only high titers 21 or have not been effective. 32 The hemagglutination inhibition (HI) test gives a higher titer than SNT 13 and is useful for detection of antibody. 31 The fluorescent antibody technique, 5 when compared with the HI test, provides similar results (G. Suzuki, personal communication).Enzyme-linked immunosorbent assay (ELISA) has been used for diagnosis of many viral diseases, 12,34 in-