Immunization with Brucella VirB proteins reduces organ colonization in mice through a Th1-type immune response and elicits a similar immune response in dogs.

POLLAK C; WANKE, MARÍA M; ESTEIN S; DELPINO MV; MONACHESI, NORMA; COMERCIO EA; FOSSATI CA; BALDI PC

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2015 vol. 22 p. 274 - 281

1932-6203

Colonizationin Mice through a Th1-Type Immune Response and Elicits a Similar ImmuneResponse in Dogs CoraN. Pollak, María Magdalena Wanke, Silvia M. Estein, M.Victoria Delpino,* Norma E. Monachesi, Elida A. Comercio, CarlosA. Fossati, Pablo C. Baldi Institutode Estudios de la Inmunidad Humoral (IDEHU, CONICET-UBA), Cátedra deInmunología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires,Buenos  Aires, Argentinaa; Servicio de Teriogenología, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Buenos Aires,Argentinab; Laboratorio de Inmunología, Departamento de Sanidad Animal yMedicina Preventiva, Centro de Investigación Veterinaria de Tandil (CIVETAN,CONICET), Facultad de Ciencias Veterinarias, Universidad Nacional del Centro dela Provincia de Buenos Aires, Tandil, Argentina VirB proteins from Brucella spp. constitutethe type IV secretion system, a key virulence factor mediating theintracellular survival of these bacteria. Here, we assessed whether a Th1-typeimmune response against VirB proteins may protect mice from Brucella infectionand whether this response can be induced in the dog, a natural host for Brucella.Splenocytes from mice immunized  with VirB7 or VirB9 responded to theirrespective antigens with significant and specific production of gammainterferon  (IFN-_), whereas interleukin-4 (IL-4) was notdetected. Thirty days after an intraperitoneal challenge with live Brucella abortus,the spleen load of bacteria was almost 1 log lower in mice immunized with VirBproteins than in unvaccinated animals. As colonization reduction seemed tocorrelate with a Th1-type immune response against VirB proteins, we decided toassess  whether such a response could be elicited in the dog. Peripheralblood mononuclear cells (PBMCs) from dogs immunized with VirB proteins (threesubcutaneous doses in QuilA adjuvant) produced significantly higher levels ofIFN-_ than cells from control animalsupon in vitro stimulation with VirB proteins. A skin test to assessspecific delayed-type hypersensitivity was positive in 4 out of 5 dogsimmunized with either VirB7 or VirB9. As both proteins are predicted to locatein the outer membrane of Brucella organisms, the ability of anti-VirBantibodies to mediate complement-dependent bacteriolysis of B. canis wasassessed in vitro. Sera from dogs immunized with either VirB7 or VirB9,but not from those receiving phosphate-buffered saline (PBS), produced significantbacteriolysis. These results suggest that VirB-specific responses that reduceorgan colonization by Brucella in mice can be also elicited in dogs.