Effects of long-term acyclovir chemosuppression on serum IgG antibody to herpes simplex virus

Oral antiviral therapy for prevention of genital herpes outbreaks in immunocompetent and nonpregnant patients

BACKGROUND

Genital herpes is caused by herpes simplex virus 1 (HSV-1) or 2 (HSV-2). Some infected people experience outbreaks of genital herpes, typically, characterized by vesicular and erosive localized painful genital lesions.

OBJECTIVES

To compare the effectiveness and safety of three oral antiviral drugs (acyclovir, famciclovir and valacyclovir) prescribed to suppress genital herpes outbreaks in non-pregnant patients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the search portal of the World Health Organization International Clinical Trials Registry Platform and pharmaceutical company databases up to February 2014. We also searched US Food and Drug Administration databases and proceedings of seven congresses to a maximum of 10 years. We contacted trial authors and pharmaceutical companies.

SELECTION CRITERIA

We selected parallel-group and cross-over randomized controlled trials including patients with recurrent genital herpes caused by HSV, whatever the type (HSV-1, HSV-2, or undetermined), with at least four recurrences per year (trials concerning human immunodeficiency virus (HIV)-positive patients or pregnant women were not eligible) and comparing suppressive oral antiviral treatment with oral acyclovir, famciclovir, and valacyclovir versus placebo or another suppressive oral antiviral treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected eligible trials and extracted data. The Risk of bias tool was used to assess risk of bias. Treatment effect was measured by the risk ratio (RR) of having at least one genital herpes recurrence. Pooled RRs were derived by conventional pairwise meta-analyses. A network meta-analysis allowed for estimation of all possible two-by-two comparisons between antiviral drugs.

MAIN RESULTS

A total of 26 trials (among which six had a cross-over design) were included. Among the 6950 randomly assigned participants, 54% (range 0 to 100%) were female, mean age was 35 years (range 26 to 45.1), and the mean number of recurrences per year was 11 (range 6.3 to 17.8). Duration of treatment was two to 12 months. Risk of bias was considered high for half of the studies and unclear for the other half. A total of 14 trials compared acyclovir versus placebo, four trials compared valacyclovir versus placebo and 2 trials compared valacyclovir versus no treatment. Three trials compared famciclovir versus placebo. Two trials compared valacyclovir versus famciclovir and one trial compared acyclovir versus valacyclovir versus placebo.We analyzed data from 22 trials for the outcome: risk of having at least one clinical recurrence. We could not obtain the outcome data for four trials. In placebo-controlled trials, there was a low quality evidence that the risk of having at least one clinical recurrence was reduced with acyclovir (nine parallel-group trials, n = 2049; pooled RR 0.48, 95% confidence interval (CI) 0.39 to 0.58), valacyclovir (four trials, n = 1788; pooled RR 0.41, 95% CI 0.24 to 0.69), or famciclovir (two trials, n = 732; pooled RR 0.57, 95% CI 0.50 to 0.64). The six cross-over trials showed larger treatment effects on average than the parallel-group trials. We found evidence of a small-study effect for acyclovir placebo-controlled trials (adjusted pooled RR 0.61, 95% CI 0.49 to 0.75). In analyzing parallel-group trials by daily dose, no clear evidence was found of a dose-response relationship for any drug. In head-to-head trials, the risk of having at least one recurrence was increased with valacyclovir rather than acyclovir (one trial, n = 1345; RR 1.16, 95% CI 1.01 to 1.34) and was not significantly different from that seen with famciclovir as compared with valacyclovir (one trial, n = 320; RR 1.18, 95% CI 0.86 to 1.63).We included 16 parallel-arm trials in a network meta-analysis and we were unable to determine which of the drugs was most effective in reducing the risk of at least one clinical recurrence (after adjustment for small-study effects, pooled RR 0.83, 95% CI 0.61 to 1.11 for valacyclovir vs acyclovir; pooled RR 1.04, 95% CI, 0.71 to 1.49 for famciclovir vs acyclovir; and pooled RR 1.26, 95% CI 0.89 to 1.75 for famciclovir vs valacyclovir). Safety data were sought but were reported as total numbers of adverse events.

AUTHORS' CONCLUSIONS

Owing to risk of bias and inconsistency, there is low quality evidence that suppressive antiviral therapy with acyclovir, valacyclovir or famciclovir in pacients experiencing at least four recurrences of genital herpes per year decreases the number of pacients with at least one recurrence as compared with placebo. Network meta-analysis of the few direct comparisons and the indirect comparisons did not show superiority of one drug over another.

Persistence of infectious herpes simplex virus type 2 in the nervous system in mice after antiviral chemotherapy

Young adult mice were inoculated with herpes simplex virus type 2 (HSV-2) in the ear pinna. A relatively severe infection resulted, and 45% of the mice died by 11 days postinfection. Therapy at 1 mg/ml by means of the drinking water with either famciclovir for periods of 5 or 10 days or valaciclovir for 5, 10, 15, or 20 days decreased clinical signs and reduced mortality to 15% or less. Throughout a period of 27 days, mice were tested daily for the presence of infectious virus in the ear pinna, brain stem, and ipsilateral trigeminal ganglia. Virus was cleared from these tissues in surviving, untreated animals by 12 days postinfection, and no infectious virus was detected subsequently in any tissue. Furthermore, no infectious virus was detected after day 9 in mice that had been treated with famciclovir. In mice that had received valaciclovir therapy, however, infectious virus was repeatedly detected in the trigeminal ganglia and brain stem tissue samples up to 7 days after treatment was discontinued. To date, no specific mechanism to account for these results has been discovered; however, possible mechanisms for the persistence of potentially infectious virus in neural tissue of treated mice are discussed.

Acyclovir treatment of skin lesions results in immune deviation in mice infected cutaneously with herpes simplex virus

Clinical observations indicate that the antibody response to herpes simplex virus (HSV) in patients undergoing acyclovir treatment is reduced and, although the exact mechanism is not clear, some authors interpret it as immunosuppression. In order to clarify the mechanism, we cutaneously infected mice with HSV-1 and treated the resulting skin lesions with acyclovir. The immune response to infection and treatment in these mice was then analysed. Acyclovir treatment was given orally (20 mg/kg, three times daily), starting on day 0 (D0), 2 (D2) or 4 (D4) after infection and continuing until day 10. The serum antibody titre and the severity of skin lesions were significantly higher in the shortest treatment group (D4) than in the longer treatment groups (D0 and D2). In contrast, a skin test analysing delayed-type hypersensitivity (DTH) to HSV antigen showed that the D0 and D2 groups exhibited stronger DTH than the D4 group. Acyclovir treatment failed to cause a dissociation between DTH and antibody production in mice immunized with inactivated HSV antigen. However, acyclovir treatment in infected mice suppressed the development of skin lesions and resulted in a dissociation between DTH response and antibody production, indicating a typical immune deviation. This was supported by a change in the ratio of the isotype antibody IgG2a to IgG1. The treatment of skin lesions with acyclovir reduced the level of antibody response, as observed clinically. This indicates that the reduced antibody response in patients treated with acyclovir may be, at least in part, due to immune deviation and not immunosuppression.

Comparison of the Western immunoblot assay and a glycoprotein G enzyme immunoassay for detection of serum antibodies to herpes simplex virus type 2 in patients with AIDS

Herpes simplex virus type 2 (HSV-2) seroprevalence in 68 patients with AIDS was 77% by Western blot (immunoblot) and 44% by glycoprotein G-2 immunoassay. Each of 16 patients with culture-proven HSV-2 infection was positive by Western blot versus 8 by glycoprotein G-2 immunoassay. No differences in age, race, duration of AIDS, acyclovir usage, or HSV-1 seroprevalence were found to explain differences in sensitivity.

Herpes simplex virus in immunocompromised patients: growing evidence of drug resistance

Antiviral drugs have proven effective in treatment of herpesvirus infections and in prevention of reactivation of latent virus. The prototype drug is acyclovir. Herpes simplex virus (HSV) is susceptible to acyclovir. There is increasing evidence in immunocompromised patients of acyclovir-resistant HSV causing clinical disease. Mechanisms of HSV resistance to acyclovir are known. These findings have implications for the future development and clinical use of antiviral drugs.