Serum Antibody Profile during Colonization of the Mouse Gut by <i>Candida albicans</i>: Relevance for Protection during Systemic Infection

<i>Candida albicans</i> is a commensal microorganism in the oral cavity and gastrointestinal and urogenital tracts of most individuals that acts as an opportunistic pathogen when the host immune response is reduced. Here, we established different immunocompetent murine models to analyze the antibody responses to the <i>C. albicans</i> proteome during commensalism, commensalism followed by infection, and infection (C, C+I, and I models, respectively). Serum anti-<i>C. albicans</i> IgG antibody levels were higher in colonized mice than in infected mice. The antibody responses during gut commensalism (up to 55 days of colonization) mainly focused on <i>C. albicans</i> proteins involved in stress response and metabolism and differed in both models of commensalism. Different serum IgG antibody-reactivity profiles were also found over time among the three murine models. <i>C. albicans</i> gut colonization protected mice from an intravenous lethal fungal challenge, emphasizing the benefits of fungal gut colonization. This work highlights the importance of fungal gut colonization for future immune prophylactic therapies

The Acidic Ribosomal Stalk Proteins Are Not Required for the Highly Specific Inactivation Exerted by α‑Sarcin of the Eukaryotic Ribosome

The ribosomal sarcin/ricin loop (SRL) is the target of ribosome-inactivating proteins like the <i>N</i>-glycosidase ricin and the fungal ribotoxin α-sarcin. The eukaryotic ribosomal stalk directly interacts with several members of the <i>N</i>-glycosidase family, favoring their disruption of the SRL. Here we tested this hypothesis for the ribotoxin α-sarcin. Experiments with isolated ribosomes, cell-free translation systems, and viability assays with <i>Saccharomyces cerevisiae</i> strains defective in acidic stalk proteins showed that the inactivation exerted by α-sarcin is independent of the composition of the ribosomal stalk. Therefore, α-sarcin, with the same ribosomal target as ricin, seems to access the SRL by a different pathway