Presence of co-infection between bovine leukemia virus and bovine herpesvirus 1 in herds vaccinated against bovine respiratory complex.

The aim of this study was molecular identification of bovine leukemia virus and possible co-infection with bovine respiratory disease complex (BRDC) viral agents in Mexican dairy herds. We collected 533 blood samples from cattle vaccinated against the BRDC virus in 9 states across Mexico. Peripheral blood leukocytes were removed and genetic material was extracted to detect bovine leukemia virus (BLV), bovine herpesvirus 1 (BoHV-1), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus 3 (BPIV-3), and bovine respiratory syncytial virus (BRSV) infection using polymerase chain reaction. We identified high BLV infection rates in 270 cattle (50.65%). One hundred and thirty-three cows (24.95%) tested positive for BoHV-1, of which 65 samples were positive for both viruses (BoHV-1 and BLV) and 68 were only positive for BoHV-1. Only 4 samples tested positive for BPIV-3 and no sample was positive for BVDV or BRSV. Relative risk and odds ratio analyses did not identify that the presence of BLV infection favors BoHV-1 co-infection in vaccinated herds.

Le but de cette étude était l'identification moléculaire du virus de la leucémie bovine et une éventuelle co-infection par des agents viraux du complexe des maladies respiratoires bovines (BRDC) dans des troupeaux laitiers mexicains. Nous avons recueilli 533 échantillons de sang de bovins vaccinés contre le virus BRDC dans neuf états du Mexique. Les leucocytes du sang périphérique ont été prélevés et le matériel génétique a été extrait pour détecter le virus de la leucémie bovine (BLV), le virus de l'herpès bovin 1 (BoHV-1), le virus de la diarrhée virale bovine (BVDV), le virus parainfluenza bovin 3 (BPIV-3), et le virus respiratoire syncytial bovin (BRSV) par réaction d'amplification en chaîne par la polymérase. Nous avons identifié des taux élevés d'infection par le BLV chez 270 bovins (50,65 %). Cent trente-trois bovins (24,95 %) ont été testés positifs pour le BoHV-1, desquels 65 échantillons étaient positifs pour les deux virus (BoHV-1 et BLV) et 68 étaient uniquement positifs pour le BoHV-1. Seuls quatre échantillons ont été testés positifs pour le BPIV-3 et aucun échantillon n'a été positif pour le BVDV ou le BRSV. Les analyses du risque relatif et des rapports de cotes n'ont pas identifié que la présence d'une infection par le BLV favorise la co-infection par le BoHV-1 dans les troupeaux vaccinés.(Traduit par les auteurs).

Signature patterns in region V4 of small ruminant lentivirus surface protein in sheep and goats.

The env gene in Small Ruminant Lentiviruses (SRLV) encodes the surface glycoprotein (SU) that divides into conserved (C1-C4) and variable regions (V1-V5). SRLV region V4 has been found to be homologous to the V3 region of human lentivirus (HIV). HIV V3 is responsible for tropism and the development of nervous clinical patterns when there is a tendency to conserve amino acids in specific "signature pattern" positions. The goal of this study was to identify signature patterns in the V4 region of the SU, which is encoded by the SRLV env gene. Secondarily, to understand how these signature patterns are associated with different clinical status in naturally infected sheep and goats. Starting with 244 samples from seropositive animals from nine Mexican states, we amplified the V4 region using nested PCR and obtained 49 SRLV sequences from peripheral blood leukocytes. Based on phylogenetic analysis results, we identified three groups: asymptomatic genotypes A (Ssx GA) and B (Ssx GB), as well as animals with arthritic presentation, genotype B (A GB). Similarity levels between group sequences ranged from 67.9%-86.7%, with a genetic diversity ranging from 12.7%-29.5% and a dN / dS ratio that indicated negative selection. Analyses using Vespa and Entropy programs identified four residues at positions 54, 78, 79 and 82 in SU region V4 as possible signature patterns, although with variable statistical significance. However, position 54 residues "N" (p = 0.017), "T" (p = 0.001) and "G" (p = 0.024) in groups A GB, Ssx GA and Ssx GB respectively, best characterized the signature patterns. The results obtained identified a signature pattern related to different genotypes and clinical status by SRLV in sheep and goats.

Lack of association between amino acid sequences of the bovine leukemia virus envelope and varying stages of infection in dairy cattle.

We collected 724 blood samples from dairy cattle from six Mexican states, and tested them for the presence of antibodies against BLV using a commercial ELISA test. Our study groups consisted of 32 samples: 12 asymptomatic cows, 12 cows with lymphocytosis and 8 samples of tumor tissue of the abomasum and heart of cattle with lymphoma. We designed three pairs of primers to amplify the complete BLV env gene, and obtained a fragment of 1548 nucleotides in length with the sequenced products. According to the phylogenetic tree we constructed to identify the viral genotype, 96.87 % of the sequences grouped into genotype 1, while a single sample from a cow with lymphocytosis (3.13 %) was associated with genotype 3 sequences. The similarity between the Mexican BLV sequences ranged from 0.985-1.00. In addition, the proportion of non-synonymous and synonymous mutations indicated negative selection. We did not identify any conserved residues in the viral protein sequences that could be related to BLV infection stage in cattle. Proviral quantification was performed using quantitative polymerase chain reaction, and we used Mood´s median test as statistical analysis. We found no significant association between proviral load and phase of infection. The sequences showed high similarity without any association between BLV surface glycoprotein and the different infection stages, nor differences in the proviral load. BLV genotype 1 was identified as prevalent in the studied samples, and for the first time in Mexico, we identified BLV genotype 3 in cattle.