Genomic organization of the human spumaretrovirus and its relatedness to AIDS and other retroviruses.

The human spumaretrovirus (HSRV) isolated from a nasopharynx carcinoma patient 17 years ago has a RNA genome 11 kb in size. It encodes besides the gag, pol, and env genes several novel genes (S1 and bel 1, 2, and 3) that are comparable to the regulatory genes R, X, tat, art, and 3'-orf of the human (HIVs) and simian immunodeficiency viruses (SIVs) with respect to genomic location and to sizes of the putative gene products. A comparison between the HIV protein sequences of the pol and the novel genes to the corresponding gene product sequences of HSRV revealed that HSRV is related to the lentiviruses but occupies a distinct phylogenetic placement of its own. A detailed analysis of the reverse transcriptase domain allows the construction of a phylogenetic tree for the known retroviral subfamilies and/or groups, including the oncoviruses, the lentiviruses, the spumaviruses, the HLTV-BLV group, and the D-type viruses. Regions of the putative novel HSRV gene products with segmental protein sequence homology to the regulatory protein of other human retroviruses are discussed. The results strengthen the view that HSRV and its novel genes should be studied in comparison to the new genes of acquired immunodeficiency syndrome (AIDS) viruses and human T cell leukemia viruses (HTLV).