Detection of Felis catus gammaherpesvirus 1 (FcaGHV1) in peripheral blood B- and T-lymphocytes in asymptomatic, naturally-infected domestic cats

• FcaGHV1 DNA detected in circulating B and T lymphocytes in domestic cats.
• Peripheral FcaGHV1 load fluctuates widely in healthy, chronically-infected cats.
• qPCR of blood taken at a single time-point will fail to detect some FcaGHV-infected cats.
• A role for FcaGHV1 in FIV-associated lymphoid malignancies is supported.

The domestic cat is natural host to both feline immunodeficiency virus and Felis catus gammaherpesvirus 1 (FcaGHV1). Comparative data suggest that these agents might act as synergistic copathogens in feline AIDS-related lymphoma. To identify leucocyte subsets harbouring gammaherpesvirus DNA, whole blood from 5 healthy, FcaGHV1-infected cats was labelled with monoclonal antibodies to feline CD21, CD4, CD8 and CD14 for 4-way fluorescence-activated cell sorting. FcaGHV1gB qPCR was performed on DNA extracted from purified fractions and whole blood longitudinally. FcaGHV1 DNA was detected in CD21+, CD4+, CD8+, but not CD14+ cells. Variation in whole blood load, up to 19,788 copies/106cells, was detected in individual cats over time. FcaGHV1 DNA was undetectable in one cat on one occasion highlighting that qPCR of whole blood from a single time point will not detect all cases of FcaGHV1 infection. Further investigation of the role of FcaGHV1 in feline lymphoid malignancies is warranted.