Solar simulator-induced herpes simplex labialis: use in evaluating treatment with acyclovir plus 348U87

Interventions for prevention of herpes simplex labialis (cold sores on the lips)

BACKGROUND

Herpes simplex labialis (HSL), also known as cold sores, is a common disease of the lips caused by the herpes simplex virus, which is found throughout the world. It presents as a painful vesicular eruption, forming unsightly crusts, which cause cosmetic disfigurement and psychosocial distress. There is no cure available, and it recurs periodically.

OBJECTIVES

To assess the effects of interventions for the prevention of HSL in people of all ages.

SEARCH METHODS

We searched the following databases up to 19 May 2015: the Cochrane Skin Group Specialised Register, the Oral Health Group Specialised Register, CENTRAL in the Cochrane Library (Issue 4, 2015), MEDLINE (from 1946), EMBASE (from 1974), LILACS (from 1982), the China National Knowledge Infrastructure (CNKI) database, Airiti Library, and 5 trial registers. To identify further references to relevant randomised controlled trials, we scanned the bibliographies of included studies and published reviews, and we also contacted the original researchers of our included studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of interventions for preventing HSL in immunocompetent people.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials, extracted data, and assessed the risk of bias. A third author was available for resolving differences of opinion.

MAIN RESULTS

This review included 32 RCTs, with a total of 2640 immunocompetent participants, covering 19 treatments. The quality of the body of evidence was low to moderate for most outcomes, but was very low for a few outcomes. Our primary outcomes were 'Incidence of HSL' and 'Adverse effects during use of the preventative intervention'.The evidence for short-term (≤ 1 month) use of oral aciclovir in preventing recurrent HSL was inconsistent across the doses used in the studies: 2 RCTs showed low quality evidence for a reduced recurrence of HSL with aciclovir 400 mg twice daily (risk ratio (RR) 0.26, 95% confidence interval (CI) 0.13 to 0.51; n = 177), while 1 RCT testing aciclovir 800 mg twice daily and 2 RCTs testing 200 mg 5 times daily found no similar preventive effects (RR 1.08, 95% CI 0.62 to 1.87; n = 237; moderate quality evidence and RR 0.46, 95% CI 0.20 to 1.07; n = 66; low quality evidence, respectively). The direction of intervention effect was unrelated to the risk of bias. The evidence from 1 RCT for the effect of short-term use of valaciclovir in reducing recurrence of HSL by clinical evaluation was uncertain (RR 0.55, 95% CI 0.23 to 1.28; n = 125; moderate quality evidence), as was the evidence from 1 RCT testing short-term use of famciclovir.Long-term (> 1 month) use of oral antiviral agents reduced the recurrence of HSL. There was low quality evidence from 1 RCT that long-term use of oral aciclovir reduced clinical recurrences (1.80 versus 0.85 episodes per participant per a 4-month period, P = 0.009) and virological recurrence (1.40 versus 0.40 episodes per participant per a 4-month period, P = 0.003). One RCT found long-term use of valaciclovir effective in reducing the incidence of HSL (with a decrease of 0.09 episodes per participant per month; n = 95). One RCT found that a long-term suppressive regimen of valaciclovir had a lower incidence of HSL than an episodic regimen of valciclovir (difference in means (MD) -0.10 episodes per participant per month, 95% CI -0.16 to -0.05; n = 120).These trials found no increase in adverse events associated with the use of oral antiviral agents (moderate quality evidence).There was no evidence to show that short-term use of topical antiviral agents prevented recurrent HSL. There was moderate quality evidence from 2 RCTs that topical aciclovir 5% cream probably has little effect on preventing recurrence of HSL (pooled RR 0.91, 95% CI 0.48 to 1.72; n = 271). There was moderate quality evidence from a single RCT that topical foscarnet 3% cream has little effect in preventing HSL (RR 1.08, 95% CI 0.82 to 1.40; n = 295).The efficacy of long-term use of topical aciclovir cream was uncertain. One RCT found significantly fewer research-diagnosed recurrences of HSL when on aciclovir cream treatment than on placebo (P < 0.05), but found no significant differences in the mean number of participant-reported recurrences between the 2 groups (P ≥ 0.05). One RCT found no preventive effect of topical application of 1,5-pentanediol gel for 26 weeks (P > 0.05). Another RCT found that the group who used 2-hydroxypropyl-β-cyclo dextrin 20% gel for 6 months had significantly more recurrences than the placebo group (P = 0.003).These studies found no increase in adverse events related to the use of topical antiviral agents.Two RCTs found that the application of sunscreen significantly prevented recurrent HSL induced by experimental ultraviolet light (pooled RR 0.07, 95% CI 0.01 to 0.33; n = 111), but another RCT found that sunscreen did not prevent HSL induced by sunlight (RR 1.13, 95% CI 0.25 to 5.06; n = 51). These RCTs did not report adverse events.There were very few data suggesting that thymopentin, low-level laser therapy, and hypnotherapy are effective in preventing recurrent HSL, with one to two RCTs for each intervention. We failed to find any evidence of efficacy for lysine, LongoVital® supplementation, gamma globulin, herpes simplex virus (HSV) type I subunit vaccine, and yellow fever vaccine in preventing HSL. There were no consistent data supporting the efficacy of levamisole and interferon, which were also associated with an increased risk of adverse effects such as fever.

AUTHORS' CONCLUSIONS

The current evidence demonstrates that long-term use of oral antiviral agents can prevent HSL, but the clinical benefit is small. We did not find evidence of an increased risk of adverse events. On the other hand, the evidence on topical antiviral agents and other interventions either showed no efficacy or could not confirm their efficacy in preventing HSL.

Ribonucleotide reductase inhibitors hydroxyurea, didox, and trimidox inhibit human cytomegalovirus replication in vitro and synergize with ganciclovir

Ganciclovir (GCV) is a deoxyguanosine analog that is effective in inhibiting human cytomegalovirus (HCMV) replication. In infected cells GCV is converted to GCV-triphosphate which competes with dGTP for incorporation into the growing DNA strand by the viral DNA polymerase. Incorporated GCV promotes chain termination as it is an inefficient substrate for elongation. Because viral DNA synthesis also relies on cellular ribonucleotide reductase (RR) to synthesize deoxynucleotides, RR inhibitors are predicted to inhibit HCMV replication. Moreover, as dGTP competes with GCV-triphosphate for incorporation, RR inhibitors may also synergize with GCV by reducing intracellular dGTP levels and there by promoting increased GCV-triphosphate utilization by DNA polymerase. To investigate potential of RR inhibitors as anti-HCMV agents both alone and in combination with GCV, HCMV-inhibitory activities of three RR inhibitors, hydroxyurea, didox, and trimidox, were determined. In both spread inhibition and yield reduction assays RR inhibitors had modest anti-HCMV activity with 50% inhibitory concentrations ranging from 36±1.7 to 221±52μM. However, all three showed significant synergy with GCV at concentrations below their 50% inhibitory and 50% toxic concentrations. These results suggest that combining GCV with relatively low doses of RR inhibitors could significantly potentiate the anti-HCMV activity of GCV in vivo and could improve clinical response to therapy.

A practical UV source to induce Herpes simplex labialis lesions in the clinic

BACKGROUND

Ultraviolet (UV) sources have been used to clinically induce herpes simplex lesions in the lips of susceptible individuals.

METHODS

This study reports the optimization of a UV source for studies involving multiple clinical laboratory sites and subsequent clinical UV induction of cold sore lesions. We describe novel adaptations of a commercially available broadband UV phototherapy lamp that facilitate determination of individual's minimal erythemal dose (MED) and expose the lips with minimal risk of viral transmission to or between the volunteers and technicians.

CLINICAL RESULTS

The source performed well in a clinical setting, with 171 of 386 subjects (44%) developing lesions, an induction rate similar to spectrally similar UV sources.

CONCLUSIONS

The advantages of consistent and reproducible exposure geometry, additional UV shielding and biological hygiene achieved by our method significantly enhance the execution of UV-induced herpes simplex labialis studies.

Effect of foscarnet cream on experimental UV radiation-induced herpes labialis

A topical 3% foscarnet cream formulation was evaluated for its ability to treat experimental UV radiation (UVR)-induced herpes labialis in a double-blind study. Healthy adult volunteers with a history of sunlight-induced herpes labialis were randomly assigned at four centers to receive either foscarnet cream (n = 152) or a vehicle control (n = 150). Following measurement of the minimal erythematous dose (MED), the subjects' lips were exposed to 4 MEDs of UV light. Subjects applied the cream on the UVR-exposed area approximately eight times daily beginning immediately after UVR exposure and continuing for 7 days, or until all lesions had a minimum of 4 days of treatment. There were no significant differences between groups in the percentages of subjects that developed any lesion, aborted lesions (did not progress beyond a papule), immediate lesions (developed within 48 h of UVR), or delayed classic lesions (developed 48 h to 7 days after UVR). Treatment with foscarnet significantly reduced the mean lesion area (49 versus 81 mm2; P = 0.01), the maximum lesion area (80 versus 141 mm2; P = 0.01), and the time to healing (P = 0.03) of the delayed classic lesions (n = 78). There was also a trend for a decrease in the mean duration of these lesions (156 versus 191 h; P = 0.08) and the duration of pain (3.9 versus 4.3 days; P = 0.06) in foscarnet-treated subjects. There were no clinically significant adverse reactions. These data suggest that topical foscarnet can be efficacious and deserves further evaluation for the treatment of herpes labialis.