Complete Genome Sequences of Two Novel European Clade Bovine Foamy Viruses from Germany and Poland

Abstract

bBovine foamy virus (BFV), or bovine spumaretrovirus, is an infectious agent of cattle with no obvious disease association but high prevalence in its host. Here, we report two complete BFV sequences, BFV-Riems, isolated in 1978 in East Germany, and BFV100, isolated in 2005 in Poland. Both new BFV isolates share the overall genetic makeup of other foamy viruses (FV). Although isolated almost 25 years apart and propagated in either bovine (BFV-Riems) or nonbovine (BFV100) cells, both viruses are highly related, forming the European BFV clade. Despite clear differences, BFV-Riems and BFV100 are still very similar to BFV isolates from China and the United States, comprising the non-European BFV clade. The genomic sequences presented here confirm the concept of high sequence conservation across most of the FV genome. Analyses of cell culture-derived genomes reveal that proviral DNA may specifically lack introns in the env-bel coding region. The spacing of the splice sites in this region suggests that BFV has developed a novel mode to express a secretory but nonfunctional Env protein. Bovine foamy virus (BFV), also designated bovine syncytial virus or spumavirus, belongs to the subfamily of Spumaretrovirinae within the Retroviridae. Foamy viruses (FV) are complex retroviruses with a unique molecular biology and capacity to cross host species borders (1, 5). There is no obvious disease associated with FV infections, but FVs have high levels of prevalence in their respective animal hosts, while the few human infections are linked to zoonotic transmission of simian FVs to human beings (9, 12).Here, we report two complete BFV consensus sequences, BFV-Riems from East Germany (GenBank accession number JX307862) and BFV100 from Poland (GenBank accession number JX307861), which were generated by PCR amplification and sequencing of from three to seven individual amplicons per genomic region. BFV genomic DNA templates were obtained from infected primary calf trachea cell cultures (KTR) for BFVRiems (4) and immortalized canine CF2Th cells for BFV100 (7). The overall genetic organization of both isolates displays all FV characteristics. When comparing the two European isolates, overall and local sequence identity is 98% for coding regions and 97% for the noncoding regions of the long terminal repeats. In contrast, similarity to BFV isolates from the United States (GenBank accession number NC001831.1) (3) and China (GenBank accession number AY134750.1) (13) is 93% across coding and noncoding regions, reflecting high genetic relatedness. Here, we propose a European and a non-European clade of BFV isolates, as clustering of the non-European BFV isolates in phylogenetic analyses suggests common ancestry, perhaps through the sale or husbandry of BFV-positive cattle.We have recently established serology-based BFV detection systems for animal and human screening, as BFV is known to be present in the human food chain through products such as raw milk (1,8,10). Based on data presented here, we are confident that these systems will cover a...

Similar Patterns of Infection with Bovine Foamy Virus in Experimentally Inoculated Calves and Sheep

“…Additionally, a single pattern of polymorphism (A to G) in a short fragment of 569 nucleotides (nt) from bet was also observed at position 92 only in isolates C1, C3, and C4. This result showed a clear correlation between geographic origin of the isolates and the pattern of genomic changes and may be a result of genetic alterations in local BFV strains as mutations were not detected in isolate C2 or the reference Polish isolate BFV 100 (GenBank accession number JX307861) (43).…”

Identification of Novel, Highly Expressed Retroviral MicroRNAs in Cells Infected by Bovine Foamy Virus

“…A comparison of the sequences of the BFV miRNAs defined in Table 1 shows that they are all fully conserved across the four reported BFV sequences, including sequences obtained for Chinese, American, and European BFV isolates (15). Indeed, the entire 122-nt BFV pri-miRNA sequence is fully conserved, with the exception of two nucleotides in the terminal loop of the miR-BF2 stem-loop that, based on previous work (31), are not predicted to affect miRNA processing or expression.…”

“…Three animals were experimentally infected with the Polish BFV100 isolate (17), which is highly related to but distinct from the German BFV Riems isolate (15), by intravenous inoculation of 5 ϫ 10 6 Cf2Th cells infected with BFV100. Two calves were inoculated with the same number of uninfected Cf2Th cells and served as negative controls, as described previously (18).…”

“…The BFV Riems isolate was initially propagated by cocultivation of infected and uninfected calf trachea cells (15). Subsequently, BFV was adapted to grow by cocultivation with Madin-Darby bovine kidney (MDBK) cells maintained in Dulbecco's modified Eagle's medium (DMEM; Sigma) supplemented with 10% fetal horse serum (Sigma).…”

Non-Simian Foamy Viruses: Molecular Virology, Tropism and Prevalence and Zoonotic/Interspecies Transmission

“…The sequence identity fluctuates between 96%–99%. BFV isolates from China and USA (BFV USA and BFV China ) arise from the same branching node, forming a clade just as BFV 100 (Poland) and BFV Riems (Germany) form the European clade (see Table 2) [31]. If BFV and the equine foamy virus (EFV) derived from a common ancestor far back in the early Eocene epoch (~50 mya) when pre-cattle and horses first hit the ground this would be the earliest time point for a possible infection with FVs.…”