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Arginine, among the amino acids, has demonstrated unique properties, including suppression of protein-protein interactions and virus inactivation. We investigated the effects of arginine on the infectivity of human herpesvirus 2 (HHV-2) and the potential application of arginine as a chemotherapeutic agent against genital herpes. Arginine directly inactivated HHV-2 and characterization of the inactivation demonstrated that 1 M arginine at pH 4.3 inactivated the virus more efficiently compared to 0.1 M citrate or 1 M sodium chloride, indicating that neither acidic pH nor ionic strength alone is sufficient for virus inactivation. The effect of arginine was rapid and concentration-dependent. Although virus inactivation was efficient at an acidic pH, arginine inactivated the virus even at a neutral pH, provided that a higher arginine concentration and prolonged incubation time were used. In addition, arginine suppressed the multiplication of HHV-2 under the conditions at which its effect on cell viability was insignificant. Pilot mouse model studies revealed a marked suppression of death by arginine when the mice were infected with HHV-2 through the vaginal route, followed by an intermittent application of acidic arginine by vaginal instillation.

Hot water extracts of coffee grinds and commercial instant coffee solutions have been shown to exhibit marked antiviral and virucidal activities against herpes simplex virus type 1 (HSV-1). Specifically, it has been shown that caffeine and N-methyl-pyridinium formate inhibit the multiplication of HSV-1 in HEp-2 cells. The present study examined the virological properties and the antiviral activity of caffeic acid against HSV-1. Caffeic acid inhibited the multiplication of HSV-1 in vitro, while chlorogenic acid, a caffeic acid ester with quinic acid, did not. These reagents did not have a direct virucidal effect. The one-step growth curve of HSV-1 showed that the addition of caffeic acid at 8 h post infection (h p.i.) did not significantly affect the formation of progeny viruses. An analysis of the influence of the time of caffeic acid addition, revealed that addition at an early time post infection remarkably inhibited the formation of progeny infectious virus in the infected cells, but its addition after 6 h p.i. (i.e., the time of the completion of viral genome replication) did not efficiently inhibit this process. These results indicate that caffeic acid inhibits HSV-1 multiplication mainly before the completion of viral DNA replication, but not thereafter. Although caffeic acid showed some cytotoxicity by prolonged incubation, the observed antiviral activity is likely not the secondary result of the cytotoxic effect of the reagent, because the inhibition of the virus multiplication was observed before appearance of the notable cytotoxicity.

Acidic pH is frequently used to inactivate viruses. We have previously shown that arginine synergizes with low pH in enhancing virus inactivation. Considering a potential application of the acid inactivation of viruses for the prevention and treatment of superficial virus infection at body surfaces and fixtures, herein we have examined the effects of various electrolytes on the acid-induced inactivation of the herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), the influenza A virus (IAV) and the poliovirus upon their incubation at 30˚C for 5 min. Eight electrolytes, i.e., phosphate, NaCl, glutamate, aspartate, pyrrolidone carboxylate, citrate, malate and acetate were tested. No detectable inactivation of the poliovirus was observed under the conditions examined, reflecting its acid-resistance. HSV-1 and HSV-2 responded similarly to the acid-treatment and electrolytes. Some electrolytes showed a stronger virus inactivation than others at a given pH and concentration. The effects of the electrolytes were virus-dependent, as IAV responded differently from HSV-1 and HSV-2 to these electrolytes, indicating that certain combinations of the electrolytes and a low pH can exert a more effective virus inactivation than other combinations and that their effects are virus-specific. These results should be useful in designing acidic solvents for the inactivation of viruses at various surfaces.

N-methyl-pyridinium formate, a novel component of coffee extracts, inhibited the multiplication of both DNA and RNA viruses. In the presence of the compound, the progeny viral yields of both herpes simplex virus type 1 (HSV-1) and poliovirus in HEp-2 cells and those of influenza virus type A in MDCK cells decreased with increasing concentrations of the compound, although the degree of viral sensitivity to this compound differed. In addition, none of these viruses were directly inactivated by the compound at the concentrations tested. Characterization of the mode of action of this compound against HSV-1 multiplication revealed that it inhibits the viral growth primarily at the initial step of virus multiplication, i.e., within 2 h after the onset of multiplication, although the virus multiplication was affected by the compound throughout the multiplication cycle. In addition, this compound showed a significant cytotoxic effect, although the observed antiviral effect was unlikely to be attributed to the cytotoxic effect.

Viral clearance is a primary concern for parenteral protein biopharmaceuticals. Low pH, detergent/solvent wash, or heating, called pasteurization, has been the main process for virus inactivation. Detergent/solvent wash is also used to treat superficial infectious diseases, including herpes simplex virus (HSV) infections. Herein we examined virus inactivation effects of acidic arginine on HSV type 2 (HSV-2) as a function of pH and temperature in an attempt to find solvent conditions that are effective for virus inactivation, yet are compatible with in vivo applications. Aqueous arginine at 0.7 M was highly effective on HSV-2, more so at lower pH and higher temperature. Its effects were stronger than 0.1 M citrate, 0.1 M citrate/0.6 M NaCl or 0.7 M citrate at any pH and temperature. This demonstrates that strong virus inactivation effects of arginine are not simply due to ionic strength or high concentration and arginine possesses a unique property that results in irreversible damage in virus particles. Such strong virus inactivation effects can be used in vivo for certain superficial infectious diseases, such as genital infections.

We investigated the effects of arginine on the multiplication of herpes simplex virus type 1 (HSV-1) and the potential of arginine as an antiherpetic agent. Arginine suppressed the growth of HSV-1 concentration-dependently. Inhibition of HSV-1 by arginine leveled off at 50-60 mM, although the higher concentration was not suitable as an antiviral agent due to cytotoxicity. 'Time of addition' experiments revealed that arginine was particularly effective when added within 6 h post-infection (h p.i.), suggesting that the reagent sensitive step is in the early stages of the infection. A one-step growth curve of HSV-1 in the presence of 30 mM arginine revealed that: i) the latent period was significantly extended, ii) the rate of formation of progeny infectious virus decreased and iii) the final yield of progeny virus decreased to 1%. The addition of arginine at 8 h p.i., after the completion of viral DNA replication in the virus multiplication, allowed the normal formation of progeny virus in the subsequent 4 h, confirming that arginine does not directly interfere with the formation of progeny infectious virus. In addition, arginine also inhibits several RNA viruses.