Abstract
We evaluated enzyme-linked immunosorbent assay (ELISA) specificity for measuring seroantibody responses to two types of retroviral infections in domestic cats: feline immunodeficiency virus (FIV) and feline foamy virus (FFV). We compared the seroreactivity of specific pathogen-free (SPF) cat sera, sera from SPF cats inoculated with either FIV or FFV, and field isolates (e.g., shelter or privately owned cats). Sera from SPF cats experimentally infected with the cognate virus had significantly lower background in both FIV and FFV ELISAs compared to sera from negative field isolates. ELISA values for SPF cats exposed to either FIV or FFV tended to have higher OD values on the opposite ELISA antigen plate. FIV nonspecific background absorbance was greater than that of FFV, and 10 of 15 sera samples from FIV seronegative field samples were measured in the indeterminant range. These findings highlight that exposure to off-target pathogens elicit antibodies that may nonspecifically bind to antigens used in binding assays; therefore, validation using sera from SPF animals exposed during controlled infection results in the setting of a cutoff value that may be inappropriately low when applied to field samples. Our work also suggests that infection of domestic cats with pathogens other than FIV results in antibodies that cross-react with the FIV Gag antigen.
Highlights
Serologic assays are routinely used for evidence of exposure to pathogens, typically by assessing antibodies to a specific antigenic epitope to the pathogen of interest in blood samples collected from individuals or populations of humans or animals [1]
We developed standard antigen-enzyme-linked immunosorbent assay (ELISA) serologic detection assays for the assessment of exposure to feline immunodeficiency virus (FIV) and feline foamy virus (FFV)
56 individual serum samples were tested (31 samples for FIV and 61 samples for FFV), (Table 1). These included samples from specific pathogen-free (SPF) cats exposed to tissue culture supernatant without virus (Sham); SPF cats inadvertently infected with feline parvovirus (SPF FPV+); SPF cats experimentally infected with FIV, FFV, or vaccinated with FIV; and several cats from
Summary
Serologic assays are routinely used for evidence of exposure to pathogens, typically by assessing antibodies to a specific antigenic epitope to the pathogen of interest in blood samples collected from individuals or populations of humans or animals [1]. Identifying nonspecific binding is crucial for developing novel serologic assays as this type of binding can falsely lead to elevated levels of the analyte measured [3]. This can cause results to fall within the indeterminate range, or, with high enough nonspecific binding, can result in false positive reactions.
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