Immune response of vaccinated and non-vaccinated mice to Coccidioides posadasii infection

An immunogenic, recombinant protein of the fungal respiratory pathogen, Coccidioides posadasii, was previously identified as a beta- 1,3-glucanosyltransferase homolog (Gel 1) and shown to confer protection to C57BL/6 mice against coccidioidomycosis. However, little is known about the nature of the humoral and cellular immune responses of these vaccinated mice to intranasal infection with a lethal inoculum of C. posadasii spores compared to non-immune control animals. Our studies showed that protective immunity in mice vaccinated with two 1 mu g doses of the recombinant Gell (rGell) plus adjuvant was characterized by high titers of antigen-specific IgG2c and elevated levels of interleukin (IL)-12 and interferon-gamma (IFN-gamma) production at 7-14 days post-challenge compared to significantly lower levels of the respective antibody and cytokines in non-immune, infected mice. Mice immunized with either 0.2 or 5 mu g doses of rGel I plus adjuvant were less well protected and showed evidence of a marked decrease in the level of T helper-type I (T-H 1) immune response. Early T-H 1 immune regulation is essential for protection against pulmonary infection with Coccidioides, and the dose of the rGel I vaccine narrowly defines the nature of immune response in the lungs of infected mice. (c) 2005 Elsevier Ltd. All rights reserved.