Transcriptome Analysis and In Situ Hybridization for FcaGHV1 in Feline Lymphoma

Lymphoma is one of the most common malignancies in domestic cats. The lymphomagenicpotential of Felis catus gammaherpesvirus 1 (FcaGHV1), a common infection in domestic cats,is unknown. In other species, including humans, cellular transformation by gammaherpesvirusesis typically mediated by viral genes expressed during latency. We analysed tumour RNA, fromdiffuse large B-cell lymphomas (DLBCL) appearing in cats coinfected with FcaGHV1 and felineimmunodeficiency virus (FIV) (n = 10). Analysis was done by high throughput transcriptomesequencing and reverse transcription PCR. A limited repertoire of FcaGHV transcripts was identifiedin five tumors, including homologs of oncogenic latency-associated transcripts, latency-associatednuclear antigen (LANA, ORF73) and vFLIP (F7), lytic genes (ORF50, ORF6, ORF59, F10), and an ORFunique to FcaGHV1, F20. In situ hybridization of FIV-associated DLBCLs (n = 9), post-transplantlymphomas (n = 6) and high-grade B and T-cell intestinal lymphomas (n = 8) identified a single casein which FcaGHV1 nucleic acid was detectable. These results demonstrate that FcaGHV1 transcriptscan be detected in some FIV-associated lymphomas, but with a low copy number, precludingassessment of a potential role for FcaGHV1 in lymphomagenesis. Future investigation of the FcaGHV1transcriptome in clinical samples might employ viral enrichment and greater sequencing depth toenhance the retrieval of viral reads. Our results suggest prioritization of a subset of intestinal T-celltumors and large granular lymphocyte lymphoma, for study.