In vitro interactions between viruses and Candida biofilm.

BACKGROUND Candida albicans is known as one of the major cause of infections related to biofilms forming on medical devices such as catheters, artifical vales, prostheses which become a source invasive candidiasis with a high mortality rates (30-50%). So far, only few studies investigated the interactions between human pathogenic viruses and biofilms, mainly focused on water biofilms. To our knowledge, there are no studies on the interplay between biofilms in humans and viruses. In this study, we studied whether Herpes Simplex Virus type 1 (HSV-1) and Coxsackievirus type B5 (CoxB5) can be encompassed in Candida biofilm, retaining their infectivity, and then be released. Moreover, we investigated the ability of Candida biofilm to hold non adhering HSV-1 infected cells within the matrix. METHODS Candida albicans biofilms were grown in tissue culture microplates and then exposed to HSV-1 or CoxB5 for 48h: after deep washing and energetic scapring of the wells to remove the matrix, the residual presence of virus was end-point titrated on VERO cells. In parallel, wells with a strain of non-biofilm producer Candida albicans (planktonic) and negative controls with only medium were processed at the same way. Alternatively, Candida biofilms were exposed to non adhering HSV-1-infected cells and then, after washing and scraping, the number of living cells attached to the biofilms and virus titer were determined. RESULTS AND DISCUSSION Both free virus particles of HSV-1 and CoxB5 and HSV-1 infected cells remained embedded in the biofilmf with a significantly higher load than in the presence of planktonic Candida or in the negative controls. Candida biofilm can be a reservoir for viruses.