Immunostimulatory activity of Pichia kluyveri, Hanseniaspora uvarum, Candida intermedia, Saccharomyces boulardii and their derivatives on RAW 264.7 macrophages

Yeasts are a group of microorganisms with structural and metabolic characteristics that influence their recognition by immune cells resulting in a species-specific response. Although Saccharomyces boulardii is a widely studied probiotic yeast, immunostimulation by non-Saccharomyces yeasts still underexplored. Therefore, the aim of this study was to characterize the response induced in macrophages stimulated by yeasts Pichia kluyveri, Hanseniaspora uvarum, Candida intermedia and their derivatives: heat-killed cells, supernatant and DNA. RAW 264.7 murine macrophages were stimulated in vitro for 24 h and the response generated was evaluated by analyzing mRNA transcription of cytokines (IL2, IL4, IL10, IL13, IL23, TNF-alpha), transcription factors (Bcl6, NFkB;, STAT3), Toll-like receptor 2 (TLR2) and YM1 protein. Viable and heat-killed cells of P. kluyveri and H. uvarum were responsible for high levels of relative mRNA transcription of transcription factors and TLR2 (between 2-8-fold increase), however were able to induce only low transcription levels for analyzed cytokines (approximately 2-fold increase). Viable cells of C. intermedia were able to stimulate a significant transcription of IL4 (7.6-fold increase) and Bcl6 (4-fold increase), while heat-killed cells stimulated the highest level of TNF-alpha (2.4-fold increase) among yeasts and their derivatives. Furthermore, supernatant from C. intermedia culture induced significant (p < 0.05) levels of TLR2 (4.4-fold increase), being the only one among supernatants to present high levels of relative mRNA transcription of TLR2. Data found in this work arouse interest in further studies on interaction between non-Saccharomyces yeasts and immune system cells, mainly referring to immunomodulatory capacity.