James T. Richards

Recurrent Genital Herpes Simplex Virus Infection in Guinea Pigs

After recovery from initial genital herpes simplex virus (HSV) infections, female guinea pigs developed spontaneous recurrent infections characterized by discrete erythematous or vesicular herpetic lesions on the external genital skin. HSV type 2 (HSV2) caused significantly more recurrent infections in guinea pigs than did HSV type 1 (HSV1). HSV2-infected animals demonstrated a significant decline in frequency of recurrences over time. The viral nature of the recurrent lesions was confirmed by recovery of infectious HSV, detection of HSV antigen, and histologic examination. Latent HSV2 could be demonstrated in dorsal root ganglia and external genital skin after recovery from the primary infection. Recurrent genital HSV infection in the guinea pig shares many features with recurrent genital herpes in humans and provides a model for studying the relationship between latency and recurrences and for exploring methods for control of recurrent disease.

Antiviral Activity of Extracts from Marine Algae

Extracts of two species of marine algae, Constantinea simplex and Farlowia mollis, were tested for antiviral activity in tissue culture and in experimental infections of mice. Treatment of confluent mouse embryo fibroblast cell monolayers with either compound before viral inoculation was effective in inhibiting the replication of herpes simplex virus type 1 and type 2, vaccinia virus, and vesicular stomatitis virus, but not encephalomyocarditis virus, Semliki Forest virus, or murine cytomegalovirus. Prophylactic administration of these extracts was effective in reducing final mortality or prolonging the mean day of death of animals inoculated by the intraperitoneal, intracerebral, or intranasal routes with herpes simplex virus type 2. When therapy was initiated after viral inoculation or at a site other than that of viral inoculation, no significant effect on mortality or on mean day of death was observed. Neither preparation was effective in mice inoculated intraperitoneally with encephalomyocarditis virus, Semliki Forest virus, or murine cytomegalovirus or in animals infected intravaginally with herpes simplex virus type 2. The prophylactic but not therapeutic antiviral activity of these preparations seriously limits their potential use in human herpes simplex virus infections.

Optimal treatment of herpes simplex virus encephalitis in mice with oral acyclovir

The effect of oral or intraperitoneal administration of acyclovir was evaluated in four experimental models of herpes simplex virus (HSV) encephalitis in mice. Mice were inoculated with HSV-1 or HSV-2 intracerebrally or with HSV-2 intranasally, intraperitoneally, or intravaginally. With all four routes of inoculation, oral acyclovir therapy significantly reduced mortality when started as late as 72 to 96 hours after viral challenge. Intraperitoneal acyclovir was not effective in protecting mice inoculated intravaginally, but was effective if given 24 to 48 hours after intracerebral or intranasal challenge and as late as 96 hours after intraperitoneal infection. Oral acyclovir was more active than intraperitoneal treatment in all four model infections. Levels of acyclovir inhibitory for HSV in cell culture were maintained in plasma and brain tissue throughout oral treatment but lasted only three to six hours after each intraperitoneal treatment. These results suggest that acyclovir may be useful in treating serious HSV infections in humans.

Alteration of Mortality and Pathogenesis of Three Experimental Herpesvirus hominis Infections of Mice with Adenine Arabinoside 5′-Monophosphate, Adenine Arabinoside, and Phosphonoacetic Acid

The therapeutic effectiveness of adenine arabinoside 5′-monophosphate (ara-AMP), adenine arabinoside (ara-A), and phosphonoacetic acid (PAA) was compared in three experimental Herpesvirus hominis type 2 infections of mice. In animals inoculated with H. hominis by the intracerebral or intraperitoneal route, both ara-AMP and ara-A were highly effective in reducing mortality even when treatment was begun 48 to 96 h after viral inoculation. ara-AMP was the most effective in both models in that treatment could be initiated 24 to 48 h later in the course of infection than with ara-A and still confer significant protection. In mice inoculated intraperitoneally, protection due to ara-AMP therapy was associated with reduced replication of virus in visceral organs and complete inhibition of transmission of virus to the brain. PAA treatment of mice inoculated intraperitoneally was effective in reducing mortality only if initiated shortly after infection. Treatment with PAA did not reduce mortality of mice inoculated intracerebrally but did prolong the mean day of death. When mice were inoculated intranasally with H. hominis, none of the three drugs altered final mortality; however, treatment with ara-AMP did prolong the mean day of death. Treatment with ara-AMP effectively reduced viral replication in the lung and liver in this model infection, but failed to prevent transmission of virus through the trigeminal nerves from the nasopharynx to the brain.

Effect of acyclovir treatment on acute and chronic murine cytomegalovirus infection

Murine cytomegalovirus (MCMV) is inhibited in vitro by 1 to 2 microM acyclovir. Therapy of a systemic MCMV infection in weanling mice with acyclovir was only minimally effective when drug was administered intraperitoneally, while oral administration by addition of acyclovir to the drinking water was highly efficacious in mice with disseminated MCMV. Effective therapy was characterized by reduction of virus titers in lung, liver, spleen, and kidney. In mice chronically infected with MCMV, treatment for 30 days with oral acyclovir eliminated or reduced virus titers in all target organs except the salivary gland. Therapeutic efficacy in this model infection using oral administration of acyclovir could be correlated with the achievement of acyclovir levels in the plasma of experimental animals two to 10 times greater than the mean inhibitory concentration for MCMV in vitro throughout treatment. The lack of efficacy observed when drug was administered intraperitoneally was associated with acyclovir levels exceeding 1 microM for one to three hours after each dose.

A comparison of phosphonoacetic acid and phosphonoformic acid activity in genital herpes simplex virus type 1 and type 2 infections of mice

The activity of phosphonoacetic acid (PAA) and phosphonoformic acid (PFA) against four strains of herpes simplex virus type 1 (HSV-1) and four strains of HSV-2 were compared in tissue culture and in a murine model of genital herpes. In mouse embryo fibroblast cells, both drugs were three-fold more active against the HSV-1 strains than against the HSV-2 strains. In contrast, in the animal model infections, PAA appeared to be more active against the HSV-2 strains, while PFA was equally effective against both HSV types. In mice infected intravaginally with HSV-2 and treated with intravaginal 5% PAA, none of the treated mice became infected, replication of virus in the genital tract was completely inhibited, none of the infected mice died from encephalitis, and latent infection in lumbosacral ganglia of surviving animals was completely prevented. In HSV-1 genital infection treated with PAA, 20-60% of mice became infected, replication of virus in the genital tract was strikingly reduced, none of the infected mice died, and latent infection was completely prevented. In both HSV-2 and HSV-1 genital infections, 20-70% of animals treated with 8% PFA became infected, growth of virus in the genital tract was reduced significantly but not completely suppressed, mortality was variably altered, and there was a trend towards reduction in the frequently of latent infection. These results indicate that HSV-1 strains are more sensitive to PAA and PFA in tissue culture, but the HSV-2 strains are generally more amenable to therapy in the murine model of genital herpes. Although PAA appeared to be more active that PFA in the genital infection, both drugs significantly altered the course of the infection. Since dermal toxicity associated with PAA precludes its use in humans and since PFA is already undergoing trials in patients with recurrent herpes labialis, the current results suggest that topical PFA deserved further evaluation in the treatment of mucocutaneous HSV infections, including genital herpes.

Topical butylated hydroxytoluene treatment of genital herpes simplex virus infections of guinea pigs

The effect of topical treatment with butylated hydroxytoluene (BHT) was evaluated in primary and recurrent genital herpes simplex virus type 2 (HSV-2) infection of guinea pigs. In the first experiment, treatment with placebo, 5%, 10%, or 15% BHT was initiated 48 h after viral inoculation and continued 4 times daily for 15 days. During primary infection no differences in maximum lesion severity or titers of virus in lesions were observed, however, lesion duration was reduced in BHT-treated animals resulting in a significantly smaller lesion score-day area under the curve. In a second experiment using U.S.P. mineral oil as an additional placebo, BHT placebo and 15% BHT in a double blind trial, similar results were obtained. Treatment of the recurrent infection in either experiment failed to alter the number of recurrent episodes or days with lesions.

Acyclovir treatment of experimental genital herpes simplex virus infections. I. Topical therapy of type 2 and type 1 infections of mice

Intravaginal inoculation of mice with herpes simplex virus (HSV) provides a model infection of genital herpes to determine the effectiveness of potential antiviral agents. topical (intravaginal) treatment with 1% or 5% acyclovir (ACV) in an ointment of gel vehicle initiated 3, 6 or 24 h after inoculation with HSV type 2, significantly inhibited viral replication in the genital tract and usually reduced final mortality. Treatment with 5% ACV initiated 48 or 72 h after infection also reduced vaginal virus titers but did not alter final mortality. When mice were inoculated with HSV type 1 treatment with 5% ACV significantly reduced viral replication in the genital tract when begun as late as 72 h. In HSV-2 infected mice, treatment initiated 3 h but not 24 h after infection prevented the establishment of latent infection in sacral ganglie. These results suggest that topical ACV may be effective antiviral agent for primary genital herpes in humans.