Caracterização molecular do gene L1 de um provável novo tipo de papilomavírus bovino identificado no Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Papillomaviruses (PVs) comprise a highly diverse group of non-enveloped oncovirus classified in Papillomaviridae family, whose genome consists of a circular double-stranded DNA molecule. Depending on nucleotide identity presented in structural protein L1, 10 types of bovine papillomavirus (BPV) are described in cattle, being each of them located in genera Deltapapillomavirus (BPV-1 and -2), Epsilonpapillomavirus (BPV-5 and -8), Xipapillomavirus (BPV-3, -4, -6, -9, and -10), and an yet assigned genus (BPV-7). Infection by diverse BPV types has been associated with different clinical outcomes in cattle, being the cutaneous papillomatosis considered as an important cause of economic losses. The identification of viral types involved with either clinical manifestations or assintomatic infections, has been mainly performed by PCR assay, both in cattle and humans. Since the L1 is considered as the most conserved protein in PVs, consensus and degenerate primers, manifesting a high degree of nucleotide identity with sequences in L1 ORF, has been designed to detect a broad range of viral types in clinical specimens. The aim of the current study is to state the phylogenetic position of a previously identified putative new BPV type (BPV/BR-UEL2) detected in Paraná state, Brazil, through the molecular characterization of its L1 gene. The BPV/BR-UEL2 was isolated from a papilloma located in the axillary region of a dairy cow. As the previous FAP sequence analysis had revealed our isolate as closest related to BPV type 4, alignments of L1, L2, LCR genomic regions of some Xipapillomavirus representatives (BPV-3, -4, and -6), were used on design of degenerate primers. In addition, the previously described FAP primer pair was also employed both in the original form as in combination with the designed primers. The first L1 segment of the Brazilian isolate could be achieved by a semi-nested PCR system (SN-PCR) employing L2Bf/FAP64 primers in the first round, and L2Bf/L1Br primer pair in the second round, which yielded an amplicon of 435 bp. The use of the FAP59/FAP64 (475 bp) and L1Bf/LCRBr (1128 bp) primer sets allowed the amplification of the remaining portions of the same gene. These three overlapping amplicons obtained from the L1 ORF were submitted to cloning and then sequenced. Phylogenetic analysis with complete L1 ORF sequences revealed the BPV/BR-UEL2 isolate as related with BPV types held in Xipapillomavirus genus, displaying the highest L1 nucleotide sequence similarity with BPV type 4 (78%), what suggests its classification in the Xipapillomavirus genus. In Brazil, despite the relatively common occurrence of BPV infections, the identification of BPV types in cattle herds is still sporadic. Recently, the use of the FAP59/FAP64 primer pair enabled the identification of four putative new BPV types, not yet described around the world, from cattle from Parana state. In the present study, we determine the phylogenetic position of one of these viral types, which was detected from a cutaneous lesion of a dairy cow. The realization of further studies involving the molecular epidemiology of BPV infections, in Brazilian cattle herds as much in diverse geographical areas around the world, could indicate its prevalence throughout the cattle as well as check its association with cutaneous lesions.

ASSUNTO(S)

bovino - doenças cattle - diseases papillomavirus diseases doenças do vírus do papiloma

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