The agmatine-containing poly(amidoamine) polymer AGMA1 was recently shown to inhibit the infectivity of several viruses, including human papillomavirus 16 (HPV-16), that exploit cell surface heparan sulfate proteoglycans (HSPGs) as attachment receptors. The aim of this work was to assess the antiviral activity of AGMA1 and its spectrum of activity against a panel of lowrisk and high-risk HPVs and to elucidate its mechanism of action. AGMA1 was found to be a potent inhibitor of mucosal HPV types (i.e., types 16, 31, 45, and 6) in pseudovirus-based neutralization assays. The 50% inhibitory concentration was between 0.34 g/ml and 0.73 g/ml, and no evidence of cytotoxicity was observed. AGMA1 interacted with immobilized heparin and with cellular heparan sulfates, exerting its antiviral action by preventing virus attachment to the cell surface. The findings from this study indicate that AGMA1 is a leading candidate compound for further development as an active ingredient of a topical microbicide against HPV and other sexually transmitted viral infections.
Human papillomaviruses (HPVs) are members of the Papillomaviridae family of double-stranded DNA nonenveloped viruses (1). The 8-kb HPV genome is enclosed in a capsid shell comprising major (L1) and minor (L2) structural proteins. Most of the HPVs belonging to the Alphapapillomavirus genus are sexually transmitted and infect the anogenital mucosa. For the great majority of immunocompetent individuals, HPV infections are transient, causing asymptomatic epithelial infections or benign epithelial hyperplasia. Genital warts are the most common lesions, caused mainly by HPV-6 and HPV-11. Small proportions of men and women fail to control viral infections and develop HPV-related malignancies, including carcinoma of the cervix, vulva, vagina, penis, anus, or oropharynx. Several HPV types belonging to HPV species 7 (HPV-18, HPV-39, HPV-45, HPV-59, and HPV-68) or species 9 (HPV-16, HPV-31, HPV-33, HPV-35, HPV-52, HPV-58, and HPV-67) can confer high oncogenic risk. HPV-16 and HPV-18 cause about 70% of all cases of invasive cervical cancer worldwide (followed by HPV-31, HPV-33, and HPV-45) (2).It has been estimated that more than 528,000 new cases of cervical cancer occur every year, and cervical cancer caused 266,000 deaths worldwide in 2012 (3, 4). Eighty-five percent of cervical cancer cases occur in women living in low-socioeconomic settings, primarily due to a lack of access to effective cervical cancer screening programs. No anti-HPV drugs are available to cure HPV lesions; therefore, the current treatments are ablative and directed at the abnormal cells associated with HPV, rather than at the virus itself. The development of new ways to prevent genital infections is essential in order to reduce the burden of HPV diseases. Two prophylactic vaccines, Gardasil and Cervarix, are currently available. The first is designed to protect against oncogenic HPV types 16 and 18 and low-risk HPV types 6 and 11 and therefore is preventive against both cancer and genital warts (5); the ...