Griffithsin Protects Mice from Genital Herpes by Preventing Cell-to-Cell Spread

Abstract

e Griffithsin, which binds N-linked glycans on gp120 to prevent HIV entry, has the most potent HIV-1 inhibitory activity described for any antiviral lectin and is being developed for topical preexposure prophylaxis. The current studies were designed to further assess its potential by exploring its activity against herpes simplex virus 2 (HSV-2), a cofactor for HIV acquisition, in vitro and in a murine model. Safety was evaluated by examining its impact on epithelial barrier integrity in polarized cultures and testing whether repeated intravaginal dosing potentiates the susceptibility of mice to genital herpes. Griffithsin displayed modest inhibitory activity against HSV-2 if present during viral entry but completely blocked plaque formation if present postentry, reduced plaque size, and prevented cell-to-cell spread. These in vitro findings translated to significant protection against genital herpes in mice treated with 0.1% griffithsin gel. Griffithsin, but not placebo gel, prevented viral spread (visualized with a luciferase-expressing virus), significantly reduced disease scores, and resulted in greater survival (P < 0.05, log rank test). Protection persisted when HSV-2 was introduced in seminal plasma. Although griffithsin triggered a small decline in transepithelial electrical resistance in polarized cultures, this did not translate to any significant increase in the ability of HIV to migrate from the apical to the basolateral chamber nor to an increase in susceptibility to HSV-2 in mice treated with griffithsin gel for 7 days. These findings demonstrate that griffithsin inhibits HSV-2 by a unique mechanism of blocking cell-to-cell spread and support its further development for HIV and HSV-2 prevention.

Vaginally Delivered Tenofovir Disoproxil Fumarate Provides Greater Protection than Tenofovir against Genital Herpes in a Murine Model of Efficacy and Safety

“…The increased susceptibility was associated with modest increases in inflammatory mediators in the genital tract and disruption of the epithelial barrier. In contrast, 1% TFV gel, 0.5% PRO 2000, and 0.1% griffithsin gel did not increase the risk of HSV infection in this model (15,17,19). These findings suggest that this relatively inexpensive small-animal model may provide a biomarker of microbicide safety.…”

Griffithsin-Modified Electrospun Fibers as a Delivery Scaffold To Prevent HIV Infection

“…We observed that all EFs were nontoxic to cells in all three vaginal cell lines, with the cells showing greater than 93% viability after treatment, indicating their potential for future translation in vivo. We expected favorable cytotoxicity results, as a feature of this platform is that an FDA-approved polymer is used with the promising biologic GRFT, which has demonstrated outstanding safety profiles both in vitro and in vivo (46,56). These results are particularly important for translation in vivo, as cytotoxicity and inflammation have been shown to increase the propensity for infection in clinical trials (2)(3)(4)(5)7).…”

“…For the adhesive surface moiety, the biological antiviral lectin GRFT was selected, as it has been demonstrated to bind to and to have antiviral efficacy against a variety of viruses, including HIV-1 and HSV-2 (44)(45)(46)(47)(48)(49)(50)(51). Previous work by our groups has demonstrated that GRFT has an exceptionally potent HIV-1-inhibitory capability as a multivalent front-line HIV entry inhibitor (49)(50)(51)(52)(53)(54), and of the biologically based inhibitors, GRFT has exceptionally potent anti-HIV activity, inactivating HIV-1 immediately upon contact (51,52).…”

“…Previous work by our groups has demonstrated that GRFT has an exceptionally potent HIV-1-inhibitory capability as a multivalent front-line HIV entry inhibitor (49)(50)(51)(52)(53)(54), and of the biologically based inhibitors, GRFT has exceptionally potent anti-HIV activity, inactivating HIV-1 immediately upon contact (51,52). Furthermore, a 0.1% GRFT gel was shown to protect mice against intravaginal HSV-2 challenge, making it a leading protein-based antiviral candidate providing multipurpose protection against both HSV-2 and HIV-1 STIs (46). Moreover, to the benefit of intravaginal administration, GRFT lacks the capacity to induce proinflammatory cytokines in human peripheral blood mononuclear cells, is resistant to a broad array of human proteases, and is stable in the presence of culture medium from vaginal microbes, retaining anti-HIV activity for up to 10 days, even when some of the six carbohydrate binding sites are occupied (55,56).…”

“…Mechanistically, GRFT has been shown to bind the terminal mannose N-linked glycan residues on viral envelope surfaces (51,55,(57)(58)(59). For HIV-1, GRFT is believed to bind to gp120 on the virion and neutralize the virus at entry, whereas for HSV-2, GRFT inhibits infection via the glycoprotein (gP) conformational changes expressed during cell-to-cell spread (46). For both HIV and HSV (among other viruses), these strong interactions between virus gPs and GRFT result in an irreversible biological effect (56) that we hypothesize inactivates the virus, resulting in physicochemical protection.…”