Thiazolides Elicit Anti-Viral Innate Immunity and Reduce HIV Replication

Alinia® (NTZ) is a first-in-class thiazolide (TZD) with an in vitro activity against parasites, anaerobic bacteria, and viruses1,2,3. This compound is currently approved in the United States in the treatment of diarrhea caused by Cryptosporidium parvum and Giardia intestinalis4,5. It is also approved in Latin America, Egypt, India and Bangladesh for the therapy of a broad range of intestinal protozoan and helminthic infections, and is available upon Emergency Use Authorization in Canada, Australia, Japan and the European Union. NTZ and its active metabolite tizoxanide (TIZ) also inhibit the replication of a broad range of RNA and DNA viruses, and NTZ was shown to be effective in clinical trials against diarrhea caused by rotavirus and norovirus, uncomplicated influenza A and B, as well as hepatitis B (HBV) and C (HCV) infections6,7,8,9,10,11,12. A large number of thiazolides closely related to the chemical structure of NTZ have been recently synthesized and tested for their anti-viral activity. RM-5038 in particular, whose active circulating metabolite is known as RM-4848, was selected for complete development due to its efficacy against C. parvum11,12,13. The wide spectrum of thiazolides activity was recently confirmed by in vitro data indicating an effect of these compounds against HIV. Thus: 1) the association between reverse transcriptase inhibitors (RTI) and NTZ is effective against HIV-1 replication14, and 2) NTZ decreases HIV-1 replication in monocyte-derived macrophages (MDM)15. We have recently shown that TIZ and RM-4848 up-regulate a number of genes involved in the TLR- and type I IFN signal transduction pathways [Trabattoni D. and Gnudi F. Personal Communication]. In particular, thiazolides increased the expression of TLR7 and 8, molecules that sense viral-derived components and trigger immune responses against RNA and DNA viruses via the induction of type I IFNs. Type I IFNs are essential antiviral proteins that activate a wide array of effectors collectively indicated as IFN-stimulated genes (ISGs). Many of these ISGs inhibit viruses at particular stages of their life cycle16,17,18,19,20 and were shown to be upregulated in HIV-1 exposed seronegative individuals (HESN)21,22. Natural resistance to HIV-1 is thought to result from a favorable genetic and immunologic milieu that, if reproduced in individuals that are not naturally gifted by such favorable profile, could result in induced resistance to this virus21,22. TLR7 and 8 stimulation, in particular, was shown to elicit strong innate immune responses and the transcription of ISGs with antiviral properties in HESN23. Because in vitro exposure of PBMCs to thiazolides stimulates the activation of an immune profile that resembles that observed in HESNs, and NTZ was shown to have an antiviral activity that synergizes with that of other drugs, we verified whether in vitro susceptibility to HIV infection could be modulated by TIZ or RM-4848.