Immune response in dogs experimentally infected with Paracoccidioides brasiliensis

The aim of the present study was to evaluate the immune response of young dogs experimentally infected with Paracoccidioides brasiliensis. Six dogs were infected intravenously with P. brasiliensis and one control dog was inoculated with sterile saline. The infected animals were sacrificed in groups of two at 1, 6 and 12 months after infection. During the experimental period, the immune responses of the dogs to the fungus were followed by ELISA (IgM and IgG), by the immunodiffusion test and by the skin test with gp43. After killing the dogs, samples from several organs were submitted to histopathological analysis (H&E and Grocott stains) but the fungus was not observed in any tissue. Attempts to isolate the fungus from these tissue samples were also unsuccessful. All infected dogs, except one, reacted positively to the immunodiffusion and skin tests. All infected dogs showed a humoral immune response to the gp43 antigen detected by ELISA. The IgM and IgG response peaked by the first and second month, respectively. We conclude that young dogs appear to be resistant to the development of paracoccidioidomycosis.