Possible Cross Reactivity of Feline and White-tailed Deer Antibodies Against the SARS-CoV-2 Receptor Binding Domain

Abstract

In late 2019, a novel coronavirus began circulating within humans in central China. It was designated SARS-CoV-2 because of its genetic similarities to the 2003 SARS coronavirus (SARS-CoV). Now that SARS-CoV-2 has spread worldwide, there is a risk of it establishing new animal reservoirs and recombination with native circulating coronaviruses. To screen local animal populations in the United States for exposure to SARS-like coronaviruses, we developed a serological assay using the receptor binding domain (RBD) from SARS-CoV-2. SARS-CoV-2's RBD differs from common human and animal coronaviruses allowing us to identify animals previously infected with SARS-CoV or SARS-CoV-2. Using an indirect ELISA for SARS-CoV-2's RBD, we screened serum from wild and domestic animals for the presence of antibodies against SARS-CoV-2's RBD. Surprisingly pre-pandemic feline serum samples submitted to the University of Tennessee Veterinary Hospital were ~70% positive for anti-SARS RBD antibodies. This was independent of prior infection with a feline coronavirus (FCoV), eliminating the possibility of FCoV cross-reactivity. We also identified several white-tailed deer from South Carolina that were also positive for anti-SARS-CoV-2 antibodies. These results bring up an intriguing possibility of a circulating agent (likely a coronavirus) with enough similarity to the SARS RBD to generate cross-reactive antibodies. Finding seropositive cats and white-tailed deer prior to the current SARS-CoV-2 pandemic, further highlights our lack of information about circulating coronaviruses in other species.