Genome Analysis of Small-Ruminant Lentivirus Genotype E: a Caprine Lentivirus with Natural Deletions of the dUTPase Subunit, vpr -Like Accessory Gene, and 70-Base-Pair Repeat of the U3 Region

Abstract

The nucleotide sequence of the highly divergent small-ruminant lentivirus genotype E has been determined. The full genome consists of 8,418 nucleotides and lacks two large portions corresponding nearly to the entire dUTPase subunit of the pol and vpr-like accessory genes. Moreover, the 70-bp repeat of the U3 region of the long terminal repeat was observed to be deleted. Interestingly, this lentivirus genotype is able to persist in a local breed population, and retrospective analysis revealed its presence in milk samples collected in 1999. gag sequences obtained from a flock coinfected with the B1 and E genotypes revealed that the evolutionary rates of the two viruses were quite similar. Since a reduced viral load and/or disease progression was observed for viruses with artificially deleted dUTPase and vpr-like genes, it is proposed that this viral cluster be designated a low-pathogenicity caprine lentivirus.The small-ruminant lentiviruses (SRLVs) are a genetically and antigenically heterogeneous group of viruses infecting sheep and goats, leading to persistent infection and chronic debilitating diseases. The majority of SRLV isolates can be classified into two main phylogenetic clusters: genotype A, involving maedi-visna virus-like strains, and genotype B, including caprine arthritis-encephalitis virus (CAEV)-like isolates, originally isolated from sheep and goats, respectively. Additional genotypes include Norwegian (genotype C) (4) and Swiss and Spanish (genotype D) (15, 18) isolates and the recently described Italian caprine isolates (genotype E) identified in flocks in which the local Roccaverano goat breed was prevalent (5). Interestingly, as for other indigenous goat breeds, typical clinical signs of lentiviral infection had never been observed in Italy before the introduction of imported breeds carrying the B1 subtype in the early 1980s.SRLVs possess a complex genome comprising the gag, pol, and env structural genes and the vif, tat, and rev accessory genes. The low-pathogenicity SRLVs characterized so far have shown that deletions or mutations in the long terminal repeat (LTR) may be associated with variations in virulence, likely due to the presence of replication enhancer elements such as AP1, AML, tumor necrosis factor-␣, and gamma interferon response elements (1, 11). Additional information about virulence factors has been produced in in vitro and in vivo studies by using genetic manipulation of infectious molecular clones (7,8,10,19,23). The dUTPase subunit, encoded by the pol gene, has been found to be dispensable for viral replication (12); however, dUTPase-negative strains produce less-severe lesions, restricted to the injection site (20). The tat gene of SRLV has been recently designated vpr-like, based on its primary protein structure and some functional similarities to human immunodeficiency virus type 1 Vpr protein (21). The CAEV tat (hereafter named vpr-like) gene increases the viral load, tissue distribution, and inflammatory lesion severity over that of the vpr deletion counterpart (9).In ...

Immunization against Small Ruminant Lentiviruses

“…Genotype E1 was firstly discovered in the Roccaverano goat breed from Piedmont (Italy) as a highly divergent SRLV [38]. Analysis in vivo showed that although the virus does not cause detectable pathological signs; genotype E is prevalent and has been hiding from standard serological tests, due to its highly divergent structural proteins, and has also been inadvertently undetected by breeders and practitioners, due to the absence of symptoms.…”

Small ruminant lentivirus genotype E is widespread in Sarda goat

“…A previously described ELISA test was used to serotype samples, consisting of 109 P16-25 recombinant antigen derived from genotypes B (strain IT-Pi1) and E 110 (strain Roccaverano) (Reina et al, 2009a). Briefly, ELISA microplatesA c c e p t e d M a n u s c r i p t 7 (Immunomaxi TPP) were coated with 100 ng of each recombinant antigen and 112 water as negative control.…”

Detailed analysis of the promoter activity of an attenuated lentivirus

“…These viruses induce persistent infections in goats and sheep, and less frequently in wild ruminants (Bertoni & Blacklaws, 2010;Bertoni & Blatti-Cardinaux, 2016;Minardi da Cruz, et al, 2013 ). Clinical manifestations such as arthritis, mastitis, pneumonia and leukoencephalomyelitis occur only in a minority of the infected individuals, depending on the genetic background of the animals and the virulence of the infecting strain (Blacklaws, 2012;Heaton et al, 2012;Ramirez et al, 2013;Reina et al, 2009;White & Knowles, 2013). SRLV are principally transmitted from mother to offspring via ingestion of infected milk or colostrum, and by aerosol between animals in close contact (Blacklaws et al, 2004).…”

“…Sequence analyses showed that all the virulence genes, such as vif, dUTPase and vpr (tat), were intact and could not explain the low virulence of these strains. Indeed, SRLV strains carrying natural or targeted mutations of these virulence genes were shown to be attenuated in vivo (Grego et al, 2007;Harmache et al, 1995aHarmache et al, , b, 1996aKristbjornsdottir et al, 2004;Reina et al, 2009;Turelli et al, 1996Turelli et al, , 1997.…”