Introduction: Is viral shedding a surrogate marker for transmission of genital herpes?

Genital herpes, caused by either herpes simplex virus type 1 or 2 (HSV-1 and HSV-2), is a significant public health problem worldwide. It increases the risk of infection with HIV, upregulates HIV after infection and can be associated with serious morbidity and mortality. It is now known that clinical and subclinical viral reactivation with resultant shedding from anogenital mucosa occurs frequently, resulting in transmission during sexual contact. Sexual transmission of HSV infection is common, even between monogamous individuals. Antiviral therapy reduces the frequency and degree of viral shedding and lowers the transmission rate in discordant monogamous couples, although transmission can still occur in people prescribed antiviral therapy. These encouraging data raise important questions for the management of genital HSV infection, particularly with regard to the prevention of transmission. Although the quantity of virus present is clearly important in transmission of some viruses, it is not clear whether this is the case for HSV transmission. Ideally, a surrogate marker needs to be able to identify individuals with detectable amounts of virus, and differentiate them from individuals with detectable amounts of virus that are transmissible. The aim of this supplement is to explore the issues surrounding the validation of surrogate markers of transmission of HSV, using examples from other human viral diseases, and to review the available evidence. In the future, exploration of these issues may shed light on management and prevention strategies. In particular, the results may clarify what evidence is required to warrant prescribing a drug for reducing HSV transmission, and for which patient populations this strategy is appropriate.

Lessons from HIV and hepatitis viruses.

Surrogate markers are an important component in the process of investigating management and prevention strategies, and for increasing understanding of viral diseases. The importance of surrogate markers and applied statistical models is particularly true for HIV. For HIV infection, the development of such methods provides new approaches for evaluation of HIV therapies and vaccines, and for the study of HIV transmission and its pathogenesis. The complex natural history of hepatitis B infection demonstrates that viral load is not the only predictor of transmission of this virus; for hepatitis C infection, viral load per se is not a prognostic factor for disease progression, but cumulative viral load may affect the outcome, and therapy is aimed at eliminating active viral replication.

HSV shedding.

Viral shedding of HSV occurs frequently in infected individuals. HSV is shed asymptomatically from multiple anatomical sites and shedding, like exposure, is a significant risk for transmission. However, the relationship between shedding frequency, viral titer and transmission is unknown. HSV-2 shedding is affected by the site and time since acquisition of infection. The advent of sensitive PCR techniques has shown that the magnitude and frequency of viral shedding is higher than shown previously with viral culture techniques. It has also clearly demonstrated that suppressive (daily) antiviral therapy reduces clinical and subclinical reactivation rates, and has been successfully used in the prevention of recurrent oral and genital HSV infections. A recent study has demonstrated that daily antiviral therapy with valaciclovir can significantly reduce transmission of HSV-2 between discordant heterosexual couples in monogamous relationships.

HSV-2 transmission.

A number of important risk factors for the acquisition of HSV-2 have been established including female gender, black or Hispanic ethnic origin, HIV infection, age, and increased number of sexual partners. Transmission is influenced by a number of biological factors such as sexual behavior, use of condoms, duration of relationships, and knowledge of a partner's serologic status. Vertical transmission (transmission of HSV from mother to neonate) is potentially life-threatening; neonatal HSV infection is associated with significant morbidity and mortality. The valaciclovir transmission study provides evidence that an antiviral agent can interrupt the transmission of a viral sexually transmitted disease between serologically discordant sexual partners. This review explores the importance of the cofactors that affect transmission, and makes recommendations on considerations for the prophylactic use of antiviral agents for the prevention of transmission in other patient populations.

Kinetics of hepatitis B viral load during 48 weeks of treatment with 600 mg vs 100 mg of lamivudine daily.

Oral therapy for chronic hepatitis B remains suboptimal. Mathematical modelling of viral decay kinetics to rapidly assess potential antiviral regimens has proved valuable for human immunodeficiency virus and cytomegalovirus. We defined the kinetics of viral replication in 10 chronic hepatitis B patients randomized to lamivudine 100 mg vs 600 mg for 48 weeks. Viral decay kinetics conformed to a biphasic pattern in nine of 10 subjects. Persons receiving 600 mg daily of lamivudine exhibited a 1.6-fold faster decay rate in the infected cell compartment (0.028/day vs 0.017/day, P = 0.06) and a greater overall change in serum viral load when compared with those receiving 100 mg (4.06 vs 1.52 log(10) copies/mL, P = 0.08). More potent therapy appeared to result in more rapid decrease in the infected cell population. Studies using mathematical modelling of viral decay may be a useful method to evaluate single or combination therapy for HBV infection in vivo.

Preclinical evaluation of docusate as protective agent from herpes simplex viruses.

Prevention of sexually transmitted infections (STIs) is key to public health efforts to control these diseases. An effective vaginal microbicide could provide topical, broad-spectrum prevention against the transmission of several STI pathogens. Docusate is a sulfated surfactant and, as such, may inactivate viral pathogens by disrupting viral envelopes and/or denaturing/disassociating proteins. Accordingly, the in vitro efficacy and toxicity of docusate (dioctyl sodium sulfosuccinate; Zorex; Meditech Pharmaceuticals, Inc., Scottsdale, Arizona) against herpes simplex viruses (HSV) were evaluated. Docusate was effective in vitro against wild type and drug-resistant strains of HSV type 1 and 2 with EC(90-100) (effective concentration giving 90-100% virus yield reduction) of approximately 0.005% (w/v). Sodium dodecyl sulfate (SDS) was equipotent, however, docusate was somewhat less toxic to uninfected Vero cells compared with SDS after 2 days incubation (docusate CC(50) approximately 0.01% vs. SDS approximately 0.005%). The cytotoxicity profiles of docusate were time- and dose-dependent and thus associated with the frequency of use. Kinetics of inactivation examined by pre-mixing virus and drug in a time-course experiment demonstrated that docusate could reach its EC(90-100) within 30 min. Docusate pretreatment of cells was associated with a 45% reduction in infectivity of those cells, despite a triple washing procedure. Once infected, an approximate 30% plaque reduction was observed with treatment.

Clinical efficacy of topical docosanol 10% cream for herpes simplex labialis: A multicenter, randomized, placebo-controlled trial.

BACKGROUND: Recurrent herpes simplex labialis (HSL) occurs in 20% to 40% of the US population. Although the disease is self-limiting in persons with a healthy immune response, patients seek treatment because of the discomfort and visibility of a recurrent lesion. OBJECTIVE: Our purpose was to determine whether docosanol 10% cream (docosanol) is efficacious compared with placebo for the topical treatment of episodes of acute HSL. METHODS: Two identical double-blind, placebo-controlled studies were conducted at a total of 21 sites. Otherwise healthy adults, with documented histories of HSL, were randomized to receive either docosanol or polyethylene glycol placebo and initiated therapy in the prodrome or erythema stage of an episode. Treatment was administered 5 times daily until healing occurred (ie, the crust fell off spontaneously or there was no longer evidence of an active lesion) with twice-daily visits. RESULTS: The median time to healing in the 370 docosanol-treated patients was 4.1 days, 18 hours shorter than observed in the 367 placebo-treated patients (P =.008; 95% confidence interval [CI]: 2, 22). The docosanol group also exhibited reduced times from treatment initiation to (1) cessation of pain and all other symptoms (itching, burning, and/or tingling; P =.002; 95% CI: 3, 16.5); (2) complete healing of classic lesions (P =.023; 95% CI: 1, 24.5); and (3) cessation of the ulcer or soft crust stage of classic lesions (P <.001; 95% CI: 8, 25). Aborted episodes were experienced by 40% of the docosanol recipients versus 34% of placebo recipients (P =.109; 95% CI for odds ratio: 0.95, 1.73). Adverse experiences with docosanol were mild and similar to those with placebo. CONCLUSION: Docosanol applied 5 times daily is safe and effective in the treatment of recurrent HSL. Differences in healing time compared favorably with those reported for the only treatment of HSL that has been approved by the Food and Drug Administration.

Current recommendations for the treatment of genital herpes.

The incidence of genital herpes continues to increase in epidemic-like fashion. Aciclovir (acyclovir) has been the original gold standard of therapy. The recent addition of famciclovir and valaciclovir as antiherpes drugs has improved convenience as well as the efficacy of treatment. Although aciclovir remains a widely prescribed and reliable drug, its administration schedule falls short of the ease of usage that the newer nucleoside analogues offer, for both episodic and suppressive therapy. Suppression of symptomatic disease and asymptomatic shedding from the genitalia have both become popular approaches, if not the primary targets of antiviral therapy. Knowing that asymptomatic disease leads to most cases of transmission strongly suggests that suppression with antiviral agents could reduce transmission risk in discordant couples. Unfortunately, the role for antivirals in reducing transmission remains to be proven in clinical trials. Neonatal herpes is now successfully treated using aciclovir. Current randomised clinical trials are examining aciclovir and valaciclovir administration, as well as safety and efficacy for post-acute suppressive therapy. Prevention of recurrences in pregnancy is also a topic under investigation, with a view to reducing the medical need for Cesarean section, or alternatively (and far less likely to be accomplished) to protect the neonate. Although resistance is largely limited to the immunocompromised and a change in resistance patterns is not expected, several drugs are available for the treatment of aciclovir-resistant strains of herpes simplex. Foscarnet is the main alternative with proven efficacy in this setting. Unfortunately, administration of foscarnet requires intravenous therapy, although a single anecdote of topical foscarnet efficacy in this setting has been published. Alternatives include cidofovir gel, which is not commercially available but can be formulated locally from the intravenous preparation. Less effective alternatives include trifluridine and interferon. Future possibilities for treatment of genital herpes include a microparticle-based controlled-release formulation of aciclovir and resiquimod (VML-600; R-848). The search for an effective therapeutic vaccine for genital herpes has not been successful to date, although a live virus glycoprotein H-deficient (DISC) vaccine is currently in clinical trials. Recent data suggest that seronegative women are protected (albeit, not fully) by a glycoprotein D recombinant vaccine with adjuvant. Despite the established safety and convenience of current treatment options, better suppressive options and topical treatment options are much needed. Studies using existing agents as potential tools to avoid Cesarean section, or transmission to neonate or partner are ongoing. Both vaccines and antivirals may eventually play a role in prevention of infection.

Improving the management of genital herpes.

Most patients with herpes simplex virus infection have mild or subclinical disease and fail to seek medical attention or are misdiagnosed. But inexpensive and accurate new serologies are being developed. Chronic suppressive therapy in patients with frequent recurrences reduces viral shedding and may reduce transmission.

A multicenter phase I/II dose escalation study of single-dose cidofovir gel for treatment of recurrent genital herpes.

A randomized, double-blind, clinic-initiated, sequential dose-escalation pilot study was performed to compare the safety and efficacy of single applications of 1, 3, and 5% cidofovir gel with placebo in the treatment of early, lesional, recurrent genital herpes at five Canadian outpatient sites. Ninety-six patients began treatment within 12 h of lesion appearance and were evaluated twice daily until healing of the lesion occurred. Cidofovir gel at all strengths significantly decreased the median time to negative virus culture in a dose-dependent fashion (3.0 days in the placebo group versus 2.2, 1.3, and 1.1 days in the 1, 3, and 5% cidofovir gel treatment groups, respectively; P = 0.02, 0.0001, and 0.0003, respectively). A trend toward a reduction in the median time to complete healing in association with treatment was present, but the differences were not statistically significant (5.0 days in the placebo group versus 4.3, 4.1, and 4.6 days in the 1, 3, and 5% cidofovir gel treatment groups, respectively). Application site reactions occurred in 3, 5, 19, and 22% of the patients in these four groups, respectively. Treatment-associated lesion recrudescence with delayed healing, which is suggestive of local toxicity, was observed in three patients treated with 5% cidofovir gel and one patient treated with 3% cidofovir gel. In summary, single-dose application of cidofovir gel confers a significant antiviral effect on lesions of recurrent genital herpes. Additional studies are warranted to further identify the optimal efficacious dose of cidofovir in association with the maximum gel strength that can be tolerated.

Infectious aortitis due to penicillin-resistant Streptococcus pneumoniae.

Infectious aortitis is uncommon and typically affects elderly immunocompromised men, with a Salmonella or Staphylococcal infection of an atheromatous or aneurysmal aorta. We present a fit young man who developed infectious aortitis with peripheral embolization due to a penicillin-resistant Streptococcus pneumoniae bacteremia.

Topical undecylenic acid for herpes simplex labialis: a multicenter, placebo-controlled trial.

A multicenter, patient-initiated, double-blind, placebo-controlled trial of 15% undecylenic acid cream was conducted with 573 patients with recurrent herpes labialis. Treatment was applied 5 or 6 times daily until crusting and then thrice daily until healing. Patients were assessed daily until 48 h after crusting and then every other day until healing. Undecylenic acid significantly reduced the incidence and duration of viral shedding and the duration and severity of itching but did not increase abortive episodes or reduce times to healing, crusting, or progression of lesion size. When treatment was initiated during the prodrome, the time to crusting was reduced (P = .02) and the area under the symptom-time curve for pain and tenderness was reduced, approaching statistical significance (P = .06). Active treatment was well tolerated but caused dysgeusia and local irritation. Undecylenic acid 15% cream reduces viral shedding in recurrent herpes labialis, but clinical benefits are minimal and largely restricted to patients initiating therapy during the prodrome.

Homopolymer mutational hot spots mediate herpes simplex virus resistance to acyclovir.

In the majority of cases, the mechanism underlying the resistance to acyclovir (ACV) of herpes simplex viruses (HSVs) is thymidine kinase (TK) deficiency. Plaque isolates from eight ACV-resistant (ACVr) clinical isolates from AIDS patients, of which five reactivated, were sequenced to determine the genetic lesion within the tk gene conferring resistance and whether this may have correlated with reactivation potential. Mutations were clustered within two homopolymer nucleotide stretches. Three plaque isolates (1737-14, 90-150-3, and 89-650-5) had insertion mutations within a stretch of 7 guanosines, while two isolates (89-063-1 and 89-353-1) had frameshift mutations within a stretch of 6 cytosines (a deletion and an insertion, respectively). Mutations resulted in premature termination codons, and the predicted 28- and 32-kDa truncated TK products were detected by Western blot analysis of virus-infected cell extracts. The repair of one homopolymer frameshift mutation (in isolate 1737-14) restored TK activity, demonstrating that this mutation is the basis of TK deficiency. Of the five reactivated isolates, four were TK deficient and contained frameshift mutations while the fifth retained TK activity because of its altered-TK or Pol- phenotype. These data demonstrate that the majority of ACVr clinical isolates contain frameshift mutations within two long homopolymer nucleotide stretches which function as hot spots within the HSV tk gene and produce nonfunctional, truncated TK proteins.

Famciclovir (FAMVIR).

Famciclovir is an antiviral with efficacy and safety comparable to aciclovir, but famciclovir's more favorable pharmacokinetic profile enables a less frequent dosing regimen. Future trials will likely determine famciclovir's role in the suppression of HBV.

Spontaneous reactivation of thymidine kinase-deficient, acyclovir-resistant type-2 herpes simplex virus: masked heterogeneity or reversion?

Herpes simplex virus (HSV) strain 1737, acyclovir-resistant and uniformly thymidine kinase-deficient (tkD) by all conventional assays, clinically reactivated in an AIDS patient in the absence of antiviral drug pressure. Investigation of its neurovirulence and latency characteristics in a mouse model using a tkD plaque isolate (1737-14), however, yielded a neurovirulent, homogeneous, acyclovir-sensitive, tk wild type (tkWT) strain (1737-14ME), while trigeminal ganglia from a surviving animal yielded a heterogeneous tkD/tkWT population (1737-14/10(5)B). Heterogeneity may have arisen due to selection of a preexisting tkWT subpopulation or to genetic reversion. "Ultralow" levels of tk, undetectable by conventional means, may be sufficient for reactivation while retaining the acyclovir-resistant phenotype. A possible mechanism for spontaneous reactivation of 1737 is in vivo complementation between heterogeneous tk populations. Eradication of acyclovir-resistant, tkD virus does not ensure subsequent reactivations to be acyclovir-sensitive, and alternating antivirals may be required for effective therapy.

New antiherpesvirus agents. Their targets and therapeutic potential.

Of the large number of agents under development for the treatment of herpes virus infections [herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV)], only ten have apparently reached clinical development. Aciclovir was approved for the treatment of HSV infections over 10 years ago, and it remains an important and reliable antiviral agent. Recent approvals in some countries of valaciclovir for VZV infection and famciclovir for both HSV and VZV infections demonstrate the rapidity of change in this field. Intravenous ganciclovir and foscarnet are approved for the treatment of CMV infection in the immunocompromised patient. Five of the antiherpetic drugs under current clinical development are nucleoside analogues or their prodrugs; another is a phosphorylated nucleoside (nucleotide). Four of the nucleoside agents-penciclovir, famciclovir, valaciclovir and lobucavir-are being developed for the management of HSV and VZV infections. Valaciclovir is also being developed for the prevention of CMV infections and famciclovir and lobucavir for the treatment of hepatitis B virus infection. Oral ganciclovir, lobucavir, ISIS 2922 and cidofovir are being developed for the suppression of CMV infections in immunocompromised patients. Sorivudine has been studied in VZV infections. n-Docosanol is under development for HSV infections, and cidofovir is being developed for both HSV and CMV infections, as well as for treatment of other viral diseases. Traditionally, the adverse effects associated with anti-CMV compounds have been more difficult to manage and are acceptable clinically only because of the severity of the underlying infection and lack of safer therapeutic alternatives. In general, toxicity issues continue to be problematic in the anti-CMV arena, although newer agents have improved the situation to some extent. In contrast, the safety of anti-HSV compounds has traditionally been excellent, establishing a safety standard that must be met by newer agents entering the field.