Design and Synthesis of Bovine Leukemia Virus-Associated Peptide-Based Qβ Conjugate Eliciting Long-Lasting Neutralizing Antibodies in Mice.

Bovine leukemia virus (BLV) is a C-type retrovirus of cattle that causes huge economic losses with high infection rates in the majority of countries worldwide. To develop an anti-BLV vaccine, we constructed a peptide conjugate using the envelope glycoprotein gp51-peptide epitope, a putative receptor-binding site. This highly antigenic peptide was covalently linked to a mutant bacteriophage carrier (mQβ) using two different linker strategies, isothiocyanate (NCS) and dinitrophenyl adipate. Both constructs elicited higher anti-BLV peptide IgG titers than the corresponding conjugate with keyhole limpet hemocyanin protein carrier (gold standard) in mice with the NCS linker strategy requiring less sample processing. The mQβ-gp51-peptide construct is the first BLV peptide-based vaccine candidate to generate durable immunity (>539 days), which recognized both native gp51 protein and BLV particles and significantly decreased fusion of a susceptible cell line exposed to infectious BLV. These results support the high translational and animal health potential of the vaccine construct.