Detection and molecular characterization of bovine leukemia virus in Philippine cattle

Abstract

Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis, which is the most common neoplastic disease of cattle. BLV infects cattle worldwide, imposing a severe economic impact on the dairy cattle industry. However, there are no comprehensive studies on the distribution of BLV in the Philippines, and the genetic characteristics of Philippine BLV strains are unknown. Therefore, the aim of this study was to detect BLV infections in the Philippines and determined their genetic variability. Blood samples were obtained from 1116 cattle from different farms on five Philippine islands, and BLV provirus was detected by BLV-CoCoMo-qPCR-2 and nested PCR targeting BLV long terminal repeats. Out of 1116 samples, 108 (9.7 %) and 54 (4.8 %) were positive for BLV provirus, as determined by BLV-CoCoMo-qPCR-2 and nested PCR, respectively. Of the five islands, Luzon Island showed the highest prevalence of BLV infection (23.1 %). Partial env gp51 genes from 43 samples, which were positive for BLV provirus by both methods, were sequenced for phylogenetic analysis. Phylogenetic analysis based on a 423-bp fragment of the env gene revealed that Philippine BLV strains clustered into either genotype 1 or genotype 6. Substitutions were mainly found in antigenic determinants, such as the CD4(+) T-cell epitope, the CD8(+) T-cell epitope, the second neutralizing domain, B and E epitopes, and these substitutions varied according to genotype. This study provides comprehensive information regarding BLV infection levels in the Philippines and documents the presence of two BLV genotypes, genotypes 1 and 6, in this population.

Molecular characterization of bovine leukemia virus from Moldovan dairy cattle

“…Similarly, the presence of more than one genotype of BLV in certain geographical areas has been reported by Camargos et al . [36], Zhao et al [28] and Polat et al [37]. In our previous work, we also reported the presence of well-separated BLV genogroups composed of isolates of similar geographical origin with a close genetic relationship to each other [8].…”

First Molecular Characterization of Bovine Leukemia Virus Infections in the Caribbean

“…Genotypes shown on the right are according to Lee et al, Polat et al, and Moratorio et al [21, 22, 27, 28]. Numbers at the branches show bootstrap support (1,000 replicates).…”

“…Neighbor-joining (NJ) phylogenetic trees were constructed using the Tamura-Nei model [20, 27] and robustness of clusters assessed by bootstrapping 1,000 replicates. Maximum-likelihood (ML) phylogenetic analysis was preformed to confirm the results.…”

Genetic diversity of bovine leukemia virus worldwide

“…A total of seven BLV genotypes have been identified in samples from Asia (G-1, -2, -3, -4, -6, -7 and -10): genotype -1, -2 and -3 in Japan (Licursi et al 2003;Zhao & Buehring 2007;Matsumura et al 2011;Inoue et al 2011); genotype -1 and -3 in Korea (Lim et al 2009;Lee et al 2015); genotype -1 and -6 in The Philippines (Polat et al 2015); genotype-1, -6…”

“…In addition, infected-cattle were also reintroduced into some of European countries; Take an example, BLV was introduced into the UK through breeding animals from Canada in 1968and 1973(EPAHW 2015 and -10 (in Thailand and Myanmar) are observed only in geographically close areas, probably due to exchange of animals between these countries (Lee et al 2016;Polat et al 2016b). Genotype-6 and -7 are also widely distributed, possibly via cattle importation and animal trading between countries (Polat et al 2015;Ochirkhuu et al 2016). …”