Bernd Maurer

Nucleotide sequence analysis of the env gene and its flanking regions of the human spumaretrovirus reveals two novel genes.

Recombinant clones that represent the 3′ part of the genome of the human spumaretrovirus (foamy virus) were established from viral DNA and from DNA complementary to viral RNA. The recombinant clones were characterized by blot hybridizations and nucleotide sequence analysis. The deduced protein sequence of the clones at their 5′ ends was found to be homologous to the 3′ domain of retroviral reverse transcriptases. Downstream of a small intergenic pol‐env region a long open reading frame of 985 amino acid residues was identified that according to its genomic location, size, glycosylation signals, and hydrophobicity profile closely resembles the lentiviral env genes. The spumaretroviral env gene is followed by two open reading frames, termed bel‐1 and bel‐2 which are located between env and the long terminal repeat region. The long terminal repeat of 1259 nucleotides is preceded by a polypurine tract and contains the canonical signal sequences characteristic for transcriptional regulation of retroviruses. The provisional classification of the spumaretrovirus subfamily is discussed.

Molecular cloning of the genome of human spumaretrovirus

DNA of human spumaretrovirus (HSRV) was cloned from both cDNA and from viral DNA into phage lambda and bacterial plasmid vectors. The recombinant plasmids harboring viral DNA were characterized by Southern blot hybridization and restriction mapping. Physical maps were constructed from cDNA and found to be colinear with the restriction maps obtained from viral DNA. The recombinant clones isolated contained viral DNA inserts which range in size from 2.2 kb to 15.4 kb. The recombinant clones allowed to construct a physical map of the complete HSRV provirus of 12.2 kb.

Identification of the major immunogenic structural proteins of human foamy virus

We have identified the major immunogenic structural proteins of the human foamy virus (HFV), a distinct member of the foamy virus subfamily of Retroviridae. Radiolabelled viral proteins were immunoprecipitated from HFV-infected cells by foamy virus antisera of human and non-human primate origin. Precipitated viral proteins were in the range of 31K to 170K. Labelling of proteins with [14C]glucosamine or with [35S]methionine in the presence of tunicamycin, as well as endo-beta-N-acetylglycosaminidase H and F treatment of [35S]methionine-labelled proteins, revealed three viral glycoproteins of approximately 170K, 130K and 47K, most likely representing the env gene-encoded precursor, the surface glycoprotein and the transmembrane protein of HFV, respectively.

The 3'-orf protein of human immunodeficiency virus 2 shows sequence homology with the bel3 gene of the human spumaretrovirus.

The primary amino acid sequence within a domain of 89 residues of the central part of the 3′‐orf protein (p27 3′‐orf) of human immunodeficiency virus (HIV‐2) shares homology with the middle and carboxy‐terminal portion of the bel3 gene product of human spumaretrovirus (HSRV). In addition, a limited region of the tat protein of HIV‐2 but not HIV‐1 shows a 28% degree of homology to the deduced protein sequence of the bel1 gene product of HSRV. Comparison between the viral sequences suggests that the 3′‐orf and bel1 gene product of HSRV could serve similar functions to those in HIV‐2.