New advances in anti-HSV chemotherapy.

Treatment of human herpes simplex virus (HSV) diseases represents an important goal, as herpetic infections are not controlled by vaccination. Many therapeutic agents have been developed and used for HSV infections and several alternative natural compounds are under investigation. Most of the drugs clinically employed against HSV types 1 and 2 are represented by guanosine nucleoside analogues, such as aciclovir and aciclovir-like drugs. The emergence of aciclovir-resistant virus strains provided a stimulus for increased search of new effective agents. Alternative drugs are other nucleoside analogues, such as the vidarabine, brivudin, and cidofovir, or pyrophosphate analogues such as foscarnet, that showed efficacy for HSV infections refractory to aciclovir. However, the risk of adverse effects reported for available anti-herpetic compounds and the frequent development of drug-resistant strains of HSV following therapeutic treatment generate the need for new antiviral agents. In the last years, several studies have been carried out on the anti-HSV activity of different components of innate host defences such as cationic antimicrobial peptides. The antiviral activity of these peptides often appears to be related to the viral adsorption and entry process or is a result of a direct effect on the viral envelope. Other natural compounds, extracts from medicinal plants employed in ethnomedicine and displaying marked anti-herpetic activity, are at present under investigation to determine the scientific evidence and rationale for their clinical use. This review discusses the anti-HSV activity of compounds licensed for clinical use and promising natural molecules.