Detecção molecular e análise filogenética de vírus respiratório sincicial bovino (BRSV) em swabs e tecido pulmonar de bovinos adultos

Abstract

Bovine respiratory syncytial viruses virus (BRSV) is one of the etiologic agents of pneumonia in young cattle. Few studies have been made aiming detection of the virus in samples collected from adult animals, especially those asymptomatic bovines. However, it is assumed that infections in these groups may occur mostly asymptomatic and this would be an important mechanism for maintaining of BRSV in herds. In this study, the goal was to conduct an analysis of the occurrence of asymptomatic infections by BRSV in lung samples (n=68) and nasal swabs (209) taken from adult animals collected in abattoirs from Southern and Southeastern Brazil respectively, to detect via polymerase chain reaction the occurrence of infected animals in populations of adult cattle. The samples that resulted positive (6) on RT-PCR were subsequently subjected to cutting with restriction enzymes and sequencing for genetic characterization (2 samples). All samples belongs to subgroup B of BRSV, which is reported as the one circulating in Brazil. The results obtained demonstrate that BRSV may be present in samples taken from adult animals, which is in agreement the hypothesis that infections in adults run in a sub-clinical way that may be of importance as a maintenance mechanism of the virus in bovine herds. RESUMO.-O vírus respiratório sincicial bovino (BRSV) é um dos agentes etiológicos de pneumonias em bovinos jovens. Poucos estudos foram realizados visando à detecção do agente em amostras coletadas de animais adultos, e em especial de bovinos assintomáticos. No entanto, presume--se que as infecções ocorridas nestes grupos possam ocorrer em sua maioria de forma assintomática e este seria um mecanismo importante para manutenção do BRSV nos rebanhos. No presente estudo, o objetivo foi realizar uma análise da prevalência de infecções assintomáticas pelo BRSV em pulmões (n=68) e swabs nasais (209) coletados de bovinos adultos coletadas em frigoríϐicos da região Sul e Sudeste respectivamente, no sentido de detectar por intermédio de reação da polimerase em cadeia qual a taxa de animais infectados em populações de animais adultos onde não ocorram sinais clínicos da infecção. As amostras positivas à RT-PCR (6) foram posteriormente submetidas ao corte com enzimas de restrição (REA) e sequenciamento para caracterização genética do gene F (2 das amostras). Todas as amostras se enquadram no subgrupo B de BRSV, o grupo circulante no Brasil conforme estudos anteriores. Os resultados obtidos demonstram que o BRSV pode estar presente em amostras obtidas de animais sadios, reforçando a hipótese de que infecções subclínicas

Molecular characterization of Brazilian wild-type strains of bovine respiratory syncytial virus reveals genetic diversity and a putative new subgroup of the virus

“…herds were shown to be genetically related to subgroup I (Domingues et al 2011). However, when compared with the BRSV sequences in this study, the nt divergences ranged from 15 to 17.3% (26 to 30% at the aa level).…”

Detection of an untyped strain of bovine respiratory syncytial virus in a dairy herd

“…Despite these hypotheses, the fact that the BRSV-UnespJab-1 strain did not amplify for the G protein gene remains unknown. The BRSV characterization, either using monoclonal antibodies or sequencing, do not always permit to classify the isolates according to the subgroups described in the literature, showing many untyped strains (FURZE et al, 1994SCHRIJVER et al, 1996a;SCHRIJVER et al, 1998). However, it is not available an untyped BRSV F protein gene sequence in GenBank to compare with the BRSV-UnespJab-1.…”

“…The subgroup A and AB were found in European countries, United States and Japan (FURZE et al, 1994;STINE;HOPPE;CLAYTON, 1997;LARSEN;TJORNEHOJ;VIUFF, 2000;NETTLETON et al, 2003;YAEGASHI et al, 2005) while the subgroup B was isolated in United Kingdom in the 1970s and later was rediscovered in Brazil (NETTLETON et al, 2003;ALMEIDA et al, 2006;VALARCHER;. All the known Brazilian isolates are classified in this subgroup (ARNS et al, 2003;ALMEIDA et al, 2006;SPILKI et al, 2006;ARNS, 2008;ARNS, 2011).…”

“…The BRSV viral envelope glycoproteins play an important role in infectivity, viral replication and immune response (FURZE et al, 1994). The G protein mediates the attachment of the virus to host cells, and the fusion protein (F) is responsible for virus penetration through fusion between the viral and host cell membranes, resulting in multinucleated giant cells (VALARCHER;.…”

“…The unclassified isolates were denominated as untyped (FURZE et al, 1994; VAN DER POEL et al, 1994;SCHRIJVER et al, 1996a;WOELK;HOLMES, 2001). The importance of this diversity regarding immunoprophylaxis is not yet completely understood, since it is not known whether vaccination against one BRSV subgroup induces cross-protection, as the natural infection ( VAN DER POEL et al, 1994;SCHRIJVER et al, 1996b).…”