Microbicidal activity of neutrophils is inhibited by isolates from recurrent vaginal candidiasis (RVVC) caused by Candida albicans through fungal thioredoxin reductase

• The RVVC isolates of C. albicans induce neutrophil migration.
• The RVVC isolates of C. albicans induce low HOCl production by neutrophils.
• The RVVC isolates of C. albicans do not induce microbicidal activity of neutrophils.
• The RVVC isolates of C. albicans induce neutrophil oxygen consumption.
• The RVVC isolates of C. albicans have high reduced thiol levels.

Vulvovaginal candidiasis (VVC) is characterized by an infection of the vulva and vagina, mainly caused by Candida albicans, a commensal microorganism that inhabits the vaginal, digestive, and respiratory mucosae. Vulvovaginal candidiasis affects approximately 75% of women, and 5% develop the recurrent form (RVVC). The aim of the present study was to evaluate whether neutrophils microbicidal response is triggered when activated with RVVC isolates caused by C. albicans. Our results showed that RVVC isolates induced neutrophil migration but significantly decrease the microbicidal activity of neutrophils, compared with VVC and ASS isolates. The microbicidal activity of neutrophils is highly dependent on the production of reactive oxygen species/reactive nitrogen species (ROS/RNS). However, this isolate induced detoxification of ROS/RNS produced by neutrophils, reflected by the high level of thiol groups and by the oxygen consumption. Therefore, RVVC isolates induced biochemical changes in the inflammatory response triggered by neutrophils, and these effects were mainly related to the detoxification of ROS/RNS through the thioredoxin reductase (TR), a key antioxidant enzyme in fungi. This might be one of the resistance mechanisms triggered by RVVC caused by C. albicans.