Pollak Cora N, Wanke María Magdalena, Estein Silvia M, Delpino M Victoria, Monachesi Norma E, Comercio Elida A, Fossati Carlos A, Baldi Pablo C
Instituto de Estudios de la Inmunidad Humoral (IDEHU, CONICET-UBA), Cátedra de Inmunología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina.
Servicio de Teriogenología, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Buenos Aires, Argentina.
Clin Vaccine Immunol. 2015 Mar;22(3):274-81. doi: 10.1128/CVI.00653-14. Epub 2014 Dec 24.
VirB proteins from Brucella spp. constitute the type IV secretion system, a key virulence factor mediating the intracellular survival of these bacteria. Here, we assessed whether a Th1-type immune response against VirB proteins may protect mice from Brucella infection and whether this response can be induced in the dog, a natural host for Brucella. Splenocytes from mice immunized with VirB7 or VirB9 responded to their respective antigens with significant and specific production of gamma interferon (IFN-γ), whereas interleukin-4 (IL-4) was not detected. Thirty days after an intraperitoneal challenge with live Brucella abortus, the spleen load of bacteria was almost 1 log lower in mice immunized with VirB proteins than in unvaccinated animals. As colonization reduction seemed to correlate with a Th1-type immune response against VirB proteins, we decided to assess whether such a response could be elicited in the dog. Peripheral blood mononuclear cells (PBMCs) from dogs immunized with VirB proteins (three subcutaneous doses in QuilA adjuvant) produced significantly higher levels of IFN-γ than cells from control animals upon in vitro stimulation with VirB proteins. A skin test to assess specific delayed-type hypersensitivity was positive in 4 out of 5 dogs immunized with either VirB7 or VirB9. As both proteins are predicted to locate in the outer membrane of Brucella organisms, the ability of anti-VirB antibodies to mediate complement-dependent bacteriolysis of B. canis was assessed in vitro. Sera from dogs immunized with either VirB7 or VirB9, but not from those receiving phosphate-buffered saline (PBS), produced significant bacteriolysis. These results suggest that VirB-specific responses that reduce organ colonization by Brucella in mice can be also elicited in dogs.
布鲁氏菌属的VirB蛋白构成IV型分泌系统，这是介导这些细菌在细胞内存活的关键毒力因子。在此，我们评估了针对VirB蛋白的Th1型免疫反应是否能保护小鼠免受布鲁氏菌感染，以及这种反应能否在布鲁氏菌的天然宿主犬体内诱导产生。用VirB7或VirB9免疫的小鼠脾细胞对各自抗原产生反应，显著且特异性地分泌γ干扰素（IFN-γ），而未检测到白细胞介素-4（IL-4）。在用活布鲁氏菌流产株腹腔攻击30天后，用VirB蛋白免疫的小鼠脾脏中的细菌载量比未接种疫苗的动物低近1个对数。由于定植减少似乎与针对VirB蛋白的Th1型免疫反应相关，我们决定评估这种反应能否在犬体内引发。用VirB蛋白（在QuilA佐剂中皮下注射三次）免疫的犬外周血单核细胞（PBMC）在体外经VirB蛋白刺激后，产生的IFN-γ水平显著高于对照动物的细胞。在5只接种VirB7或VirB9的犬中，有4只的评估特异性迟发型超敏反应的皮肤试验呈阳性。由于这两种蛋白预计定位于布鲁氏菌生物体的外膜，因此在体外评估了抗VirB抗体介导犬布鲁氏菌补体依赖性细菌溶解的能力。用VirB7或VirB9免疫的犬的血清可产生显著的细菌溶解，而接受磷酸盐缓冲盐水（PBS）的犬的血清则不能。这些结果表明，在小鼠中能减少布鲁氏菌在器官定植的VirB特异性反应在犬中也能引发。
