Pathogenic mechanisms underlying
paracoccidioidomycosis are still poorly understood. A well-established murine model of resistance (mouse lineage A/Sn) and susceptibility (lineage B10.A) to P. brasiliensis pulmonary
infection was here employed to compare immune response to gp43, the major antigenic component of the fungus. Mice were infected and their cellular and humoral immunity to gp43 were investigated for up to 16 weeks. In both mouse strains, challenge with gp43 indistinguishably evoked a typical
immediate-hypersensitivity response, followed by a 24-h late-phase reaction consistent with the same type of immunological activation.
IL-4 was detected in cultures of gp43-stimulated lymph node cells only in susceptible animals 2 weeks post-
infection, while
IL-5 was found throughout the study in both mouse strains.
IL-10 appeared in the supernatants of stimulated cells from resistant and susceptible animals in increasing amounts as
infection advanced. Conversely,
interferon (IFN)-gamma was produced under gp43 stimulation only by cells from A/Sn animals. The humoral response was characterized by low levels of anti-gp43. Titration of
IgG isotypes, however, revealed a predominance of
IgG1.
IgG2a levels were highest in resistant animals, whereas
IgG2b levels were highest in susceptible mice. In conclusion, immunity induced by gp43 exhibits common features in A/Sn and B10.A phenotypes, such as
immediate hypersensitivity, late phase reaction and high levels of
IL-10, but some differences between the strains are also seen.