IMMUNOMODULATORY EFFECTS OF NITAZOXANIDE AND RELATED MOLECULES

Background: Nitazoxanide (Alinia®, NTZ) and its active circulating metabolite tizoxanide (TIZ) belong to a new class of anti-infective agents active against parasites, anaerobic bacteria, and viruses. Nowadays, NTZ is licensed in the United States for the treatment of diarrhea caused by Cryptosporidium parvum and Giardia lamblia in adults and children older than twelve months of age. The amplitude of the spectrum of pathogens targeted by NTZ and new-generation non-nitro thiazolides, makes it very unlikely that the action of these compounds is mediated by a pathogen-specific mechanism(s), suggesting instead that thiazolides act as immunomodulants. To date, the potential effect of these compounds on immune responses has nevertheless not been analysed. In particular, because innate immunity and type 1 interferons are pivotal in early and effective antiviral immune responses that are not antigen-restricted, it is plausible to hypothesize that thiazolides could potentiate this arm of the immune system. To verify this possibility, we performed extensive in vitro analyses on the immunomodulatory effects of TIZ and the second generation non-nitro thiazolide RM4848 using two different models of viral infection: Influenza and HIV-1. Methods: Peripheral blood mononuclear cells (PBMCs) from 20 healthy donors were stimulated with influenza virus antigen (FLU) or infected with HIV-1BaL strain and cultured in presence/absence of TIZ or RM4848. Thiazolide effects on innate immunity were examined by evaluating TLRs expression on monocytes, IFN-secretion by dendritic cells, cytokine and chemokine production, mRNA expression of multiple genes involved in TLR, type I IFN and in cholesterol metabolism pathways. Results: Thiazolides are associated with strong immunomodulatory effects. Notably, these compounds, both in FLU-stimulated and in HIV-1-infected cells, significantly increase: 1) TLR-expression on monocytes, 2) IFN production, 3) chemokine and cytokine production, 4) mRNA expression of different genes operating in the TLR and type I IFN pathways, 5) genes involved in cholesterol metabolism and efflux. Conclusions: Data herein show that thiazolides are potent type I IFN inducers, triggering a selective activation of several IFN-stimulated gene (ISG) pathway. Thus, increased expression of innate antiviral factors and the different modulation of genes involved in cholesterol metabolism and efflux suggest a new mechanism of action mediated by thiazolides.