Griffithsin and Carrageenan Combination To Target Herpes Simplex Virus 2 and Human Papillomavirus

Abstract

Extensive preclinical evaluation of griffithsin (GRFT) has identified this lectin to be a promising broad-spectrum microbicide. We set out to explore the antiviral properties of a GRFT and carrageenan (CG) combination product against herpes simplex virus 2 (HSV-2) and human papillomavirus (HPV) as well as determine the mechanism of action (MOA) of GRFT against both viruses. We performed the experiments in different cell lines, using time-of-addition and temperature dependence experiments to differentiate inhibition of viral attachment from entry and viral receptor internalization. Surface plasmon resonance (SPR) was used to assess GRFT binding to viral glycoproteins, and immunoprecipitation and immunohistochemistry were used to identify the specific glycoprotein involved. We determined the antiviral activity of GRFT against HSV-2 to be a 50% effective concentration (EC50) of 230 nM and provide the first evidence that GRFT has moderate anti-HPV activity (EC50 = 0.429 to 1.39 μM). GRFT blocks the entry of HSV-2 and HPV into target cells but not the adsorption of HSV-2 and HPV onto target cells. The results of the SPR, immunoprecipitation, and immunohistochemistry analyses of HSV-2 combined suggest that GRFT may block viral entry by binding to HSV-2 glycoprotein D. Cell-based assays suggest anti-HPV activity through α6 integrin internalization. The GRFT-CG combination product but not GRFT or CG alone reduced HSV-2 vaginal infection in mice when given an hour before challenge (P = 0.0352). While GRFT significantly protected mice against vaginal HPV infection when dosed during and after HPV16 pseudovirus challenge (P < 0.026), greater CG-mediated protection was afforded by the GRFT-CG combination for up to 8 h (P < 0.0022). These findings support the development of the GRFT-CG combination as a broad-spectrum microbicide.

Griffithsin: An Antiviral Lectin with Outstanding Therapeutic Potential

“…In in vitro studies, GRFT showed weak-to-moderate activity in blocking HSV-2 entry, yet it was capable of inhibiting cell-to-cell spread with IC 50 s in the nanomolar range [34,42]. In in vivo studies using a murine model, a gel containing 0.1% GRFT significantly protected mice from HSV-2 challenge compared to the control group.…”

“…Though GRFT treatment led to a small decline in epithelial barrier integrity in polarized cell cultures, no increase in HIV migration was observed establishing its safety for HSV-2 prevention [42]. In vitro binding and immunoprecipitation studies suggest GRFT blocks HSV-2 infection by interacting with one of the four glycoproteins involved in HSV-2 entry, namely glycoprotein D [34]. …”

“…In vitro experiments have shown that GRFT has anti-HPV activity ranging from the high nanomolar to the low micromolar range [34]. HPV is a non-enveloped virus.…”

“…HPV is a non-enveloped virus. Interestingly, it was found that GRFT does not block the initial attachment of the virus to the cell; instead, it acts in a late step in the HPV entry process [34]. Data suggests that GRFT interacts with the HPV secondary receptor α6 integrin, decreasing its availability on the cell surface.…”

“…Data suggests that GRFT interacts with the HPV secondary receptor α6 integrin, decreasing its availability on the cell surface. GRFT decreased HPV 16 pseudovirus (PsV) vaginal infection in a murine model [34]. …”