ABSTRACT
Bovine leukemia virus (BLV) and human T-lymphotropic virus type 1 (HTLV-1) are closely related d-retroviruses that induce hematological diseases. HTLV-1 infects about 15 million people worldwide, mainly in subtropical areas. HTLV-1 induces a wide spectrum of diseases (e.g., HTLV-associated myelopathy/tropical spastic paraparesis) and leukemia/lymphoma (adult T-cell leukemia). Bovine leukemia virus is a major pathogen of cattle, causing important economic losses due to a reduction in production, export limitations and lymphoma-associated death. In the absence of satisfactory treatment for these diseases and besides the prevention of transmission, the best option to reduce the prevalence of d-retroviruses is vaccination. Here, we provide an overview of the different vaccination strategies in the BLV model and outline key parameters required for vaccine efficacy.
Subject(s)
Deltaretrovirus Infections/prevention & control , Deltaretrovirus/immunology , Vaccination , Viral Vaccines/immunology , Animals , Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Cattle , Deltaretrovirus/physiology , Deltaretrovirus Infections/virology , Enzootic Bovine Leukosis/prevention & control , Enzootic Bovine Leukosis/virology , HTLV-I Infections/prevention & control , Human T-lymphotropic virus 1/immunology , Human T-lymphotropic virus 1/physiology , Humans , Leukemia Virus, Bovine/immunology , Leukemia Virus, Bovine/physiology , Vaccines, Attenuated/immunologyABSTRACT
Previous studies have classified the env sequences of bovine leukemia virus (BLV) provirus from different locations worldwide into between two and four genetic groupings. These different studies gave unique names to the identified groups and no study has yet integrated all the available sequences. Thus, we hypothesized that many of the different groups previously identified actually correspond to a limited group of genotypes that are unevenly distributed worldwide. To examine this hypothesis, we sequenced the env gene from 28 BLV field strains and compared these sequences to 46 env sequences that represent all the genetic groupings already identified. By using phylogenetic analyses, we recovered six clades, or genotypes, that we have called genotypes 1, 2, 3, 4, 5 and 6. Genotypes 1-5 have counterparts among the sequence groupings identified previously. One env sequence did not cluster with any of the others and was highly divergent when compared with the six genotypes identified here. Thus, an extra genotype, which we named 7, may exist. Similarity comparisons were highly congruent with phylogenetic analyses. Furthermore, our analyses confirmed the existence of geographical clusters.