Isolation and tissue distribution of type-C virus and viral components from a gibbon ape ( Hylobates lar) with lymphocytic leukemia

A seven-year-old male gibbon ape ( Hylobates lar) with malignant lymphoma and leukemia was obtained from a colony in Bermuda. Tissues obtained at necropsy were infiltrated with tumor cells to varying degrees, the most extensively involved being the kidneys, ureters, liver, lymph nodes, heart, salivary glands, and mesentery. These cells showed typical lymphoblast morphology. Type-C virus particles were abundant in the plasma and were detectable in all tissues tested. Intracytoplasmic virus was seen in some nonleukemic parenchymal cells. However, budding virus particles were observed only from the leukemic peripheral blood lymphoblasts. Tissue extracts contained viral p30, reverse transcriptase, viral RNA, and proviral DNA in amounts which generally correlated with the degree of leukemic cell infiltration. Viral markers were particularly abundant in tissue from the region of the oral cavity. Proviral DNA was found in all tissues except muscle and brain, which contained little or no leukemic cell infiltration. Replicating virus was transmitted to heterologous cells in tissue culture from many tissues, including muscle and brain. This virus, called GaLV H was classified as a member of the gibbon ape leukemia virus-simian sarcoma (simian sarcoma-associated) virus group by comparative tests of the antigenic relatedness of p30 and reverse transcriptase, and by nucleotide sequence homology of RNA from this virus and from other members of this group. These results: (a) highlight the extraordinary replication of this type of virus in gibbons; (b) further implicate this virus group in the etiology of spontaneous gibbon ape leukemia; (c) suggest that the oral route is a likely mode of virus transmission; and (d) fail to provide evidence for a genetic reservoir of virus outside of the tumor cells.