Immunotherapy based on Pythium insidiosum mycelia drives a Th1/Th17 response in mice

Pythium insidiosum is an oomycete that affects mammals, especially humans and horses, causing a difficultto-treat disease. Typically, surgical interventions associated with antimicrobial therapy, immunotherapy, or both are the preferred treatment choices. PitiumVac (R) is a therapeutic vaccine prepared from the mycelial mass of P. insidiosum and is used to treat Brazilian equine pythiosis. To better understand how PitiumVac (R) works, we analyzed the composition of PitiumVac (R) and the immune response triggered by this immunotherapy in mice. We performed an enzymatic quantification that showed a total glucan content of 21.05% +/- 0.94 (alpha-glucan, 6.37% +/- 0.77 and (1,3)(1,6)-beta-glucan, 14.68% +/- 0.60) and mannose content of 1.39% +/- 0.26; the protein content was 0.52 mg ml(-1) +/- 0.07 mg ml(-1). Healthy Swiss mice (n = 3) were subcutaneously preimmunized with one, two, or three shots of PitiumVac (R) and immunization promoted a relevant Th1 and Th17 responses compared to nonimmunization of mice. The highest cytokine levels were observed after the third immunization, principally for IFN-gamma, IL-17A, IL-6, and IL-10 levels. Results of infected untreated (Pythiosis) and infected treated (Pythiosis + PVAC) mice (n = 3) showed that PitiumVac (R) reinforces the Th1/Th17 response displayed by untreated mice. The (1,3)(1,6)-beta-glucan content can be, at least in part, related to this Th1/Th17 response.