Vaccination protects B cell-deficient mice against an oral challenge with mildly virulent Toxoplasma gondii

Prior studies have demonstrated that B cells are important components of protection in vaccinated mice challenged intraperitoneally with a highly virulent type I strain of Toxoplasma gondii parasites. However, it is not known whether B cells are required for vaccinated mice to successfully resist a more physiologically relevant challenge infection with a mildly virulent type II strain of T gondii. To investigate that question, we vaccinated B cell-deficient C57BL/6 (muMT) mice with an attenuated strain of T gondii and challenged them with a potentially lethal oral dose of type II T gondii cysts. Vaccinated muMT mice survived the challenge as well as vaccinated B6 controls, controlled parasites equally well in critical tissues, produced equivalent levels of mRNA for several type I cytokines, and exhibited comparably mild histopathology. Thus, a vaccine can protect against infection with a mildly virulent type II strain of T gondii in the absence of a B cell-dependent immune response. (C) 2004 Elsevier Ltd. All rights reserved.