Immunogenicity and protection against Haemophilus parasuis infection after vaccination with recombinant virulence associated trimeric autotransporters (VtaA)

Haemophilus parasuis is the etiological agent of Glässer's disease in swine, characterized by fibrinous polyserositis, polyarthritis and meningitis. The lack of a vaccine against a broad spectrum of strains has limited the control of the disease. Recently, virulence associated trimeric autotransporters (VtaA) were described as antigenic proteins of H. parasuis. In this study 6 VtaA were produced as recombinant proteins and used to immunize snatch-farrowed, colostrum-deprived piglets. Immunized animals developed specific systemic and mucosal antibodies. The protective capacity of the anti-VtaA antibodies was evaluated by the inoculation of 3 × 108 or 6 × 106 colony forming units (CFU) of the highly virulent strain Nagasaki. Vaccinated animals had a delayed course of disease and 33 or 57%, respectively, of the animals survived the lethal challenge. The partial protection achieved with the recombinant VtaA supports their potential as candidates to be included in future vaccine formulations against H. parasuis.