Transcriptome Analysis and In Situ Hybridization for FcaGHV1 in Feline Lymphoma

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