Antimicrobial activities of human biofluids and their antimicrobial peptide fractions against Candida albicans

It is known that human biological fluids contain antimicrobial protective factors that include antimicrobial peptides (AMP). Concentrations of AMP vary in different biofluids and tissues. The aim of the present study is to estimate the total antimicrobial activity of different human biofluids in comparison with the activity of their AMP fractions as markers of local immunity. The antimicrobial activities of serum (SE), vaginal fluid (VF), saliva (SA), water-soluble part of skin secretion (SS) and urine (UR) of 6 healthy women, 22-25 years old, were measured by the spectrophotometric method based on the ability of the above-mentioned biofluids to disrupt the cytoplasmic membrane of Candida albicans [Patent RF No 2602298]. The results were evaluated as the percent of dye penetrated into dead cells of treated yeast cell suspensions compared to the control ones. The medians of total and AMP activities are SE – 86.6% and 33.7%; VF – 24.8% and 21.9%; SA – 18.3% and 10.9%; SS – 12.8% and 2.8%; UR – 10.0% and 0.0%, respectively. The highest level of immune defense occurs in SA whereas the lowest in UR. The antimicrobial activity of AMP in VF is maximal compared to the other biofluids. Levels of total and AMP activities of SA, SS and UR have high positive correlation between each other (Pirson’s correlation coefficients r ≥ 0,700), while none of them correlated with the activities of VF (r ≤ 0,300). Using the most appropriate method of antimicrobial activity estimation the differences between biofluids of healthy human tissues of different localization are demonstrated for the first time.