A prime-boost combination of a three-protein cocktail and multiepitopic MVA as a vaccine against Babesia bigemina elicits neutralizing antibodies and a Th1 cellular immune response in mice.

In the intraerythrocytic protozoan parasites of the genus Babesia both innate and adaptive immune responses are necessary to confer protection against clinical disease. In particular, the adaptive immune response involves the production of neutralizing antibodies as well as the presentation of parasite antigens to CD4+ T lymphocytes by professional antigen-presenting cells. Therefore, the development of alternative vaccines that replace the use of live attenuated strains should include relevant epitopes targeting both B and T cell responses. The aim of this study was to design new Babesia bigemina immunogens and evaluate the humoral and cellular responses in mice. To achieve this, three B. bigemina recombinant antigens called Apical Membrane Antigen 1 (AMA-1), Rhoptry Associated Protein 1 (RAP-1) and the Thrombospondin Related Anonymous Protein 1 (TRAP-1) were obtained. Besides, two recombinant modified vaccinia virus Ankara vectors coding for chimeric constructs containing bioinformatically predicted B and T cell epitopes from the same three antigens were generated. These immunogens were evaluated in prime-boost heterologous schemes. Among the combinations tested, priming with a cocktail of the three proteins followed by a booster immunization with a mix of both viruses induced the highest activation of IFN-γ+ CD4+ and CD8+ antigen-specific T cell responses. Remarkably, all vaccine schemes containing antigen cocktails also induced antibodies that were capable of neutralizing merozoite invasion of bovine erythrocytes in vitro at a level comparable to an anti B. bigemina hyperimmune bovine serum. Our results offer a new perspective for vaccines against B. bigemina combining bioinformatics predictions and prime-boost immunization regimes for future control measures against bovine babesiosis.

BHV-1 vaccine induces cross-protection against BHV-5 disease in cattle.

Protection against BHV-5 disease induced by inactivated BHV-1 or BHV-5 based vaccines was analysed. Two groups of calves were subcutaneously immunized with an inactivated BHV-1 or BHV-5 based vaccine. A third group was not vaccinated and used as control. In the post-vaccination period, we studied the humoral and cellular immune response resulting similar to both groups. The efficacy of the vaccines was tested after intranasal challenge of the calves with a virulent Argentinean BHV-5 isolate (A-663). All control animals developed neurological signs associated with BHV-5 infection and high levels of virus shedding. Calves immunized with the BHV-1 and BHV-5 inactivated vaccines were protected against BHV-5 disease. Our study provides evidence that strongly support the existence of cross-protection between BHV-1 and BHV-5 in calves. Even though this has already been suggested by previous works, this is the first time an exhaustive study of the immune response is performed and typical clinical BHV-5 meningoencephalitis signs are reproduced in an experimental BHV-5 challenge trial.

Bovine herpes virus gD protein produced in plants using a recombinant tobacco mosaic virus (TMV) vector possesses authentic antigenicity.

A tobacco mosaic virus (TMV)-based vector was utilized for expression of a cytosolic form of the bovine herpesvirus type 1 (BHV-1) protein glycoprotein D (gDc). Nicotiana benthamiana plants were harvested 7 days after inoculation with RNA transcripts derived from the TMV-gDc recombinant virus. Recombinant gDc protein of expected electrophoretic mobility accumulated in inoculated leaves to a concentration of about 20 micrograms/g of fresh leaf tissue. Oil-based vaccines were formulated with crude foliar extracts to immunize mice parentally. After a single injection, animals developed a sustained and specific response to both the isolated gD and native virus particles. Cattle vaccinated with the same gDc containing extracts developed specific humoral and cellular immune responses directed against both the viral gD and BHV-1 particles. Most importantly, animals vaccinated with the plant-produced gDc showed good levels of protection after challenge with the virulent BHV-1. Virus excretion was drastically reduced in these animals, reaching levels comparable to animals vaccinated with a commercial BHV-1 vaccine. The positive immunological characterization obtained for the gDc, indicated that an important part of the natural conformation was retained in the plant recombinant protein.