Immunomodulation as a treatment strategy for genital herpes: review of the evidence

Successful application of prime and pull strategy for a therapeutic HSV vaccine

One promising approach for a herpes simplex virus vaccine uses a vaccine to prime and a chemoattractant to pull immune cells into the genital tract. We evaluated subunit vaccines (prime) and imiquimod (pull) in the guinea pig (gp) model of recurrent Herpes simplex virus type-2 (HSV-2). Following vaginal HSV-2 infection, gps were vaccinated with various combination of glycoproteins and adjuvant with or without subcutaneous or local applications of imiquimod after infection. Animals were examined daily for recurrent lesions and vaginal swabs collected for recurrent shedding. Although both the vaccines alone and imiquimod alone reduced recurrent HSV disease, the combination of local imiquimod and vaccine (Prime and Pull) was the most effective. In the first study, immunization with the trivalent vaccine alone or imiquimod alone decreased recurrent disease. However, the largest decrease was with the combination of vaccine and local imiquimod (P < 0.001 vs. placebo or vaccine alone). No effect on recurrent shedding was observed. In the second study, recurrent disease scores were similar in the PBS control group and the trivalent-immunized group treated with subcutaneous imiquimod however, significant reductions with glycoprotein vaccines and local imiquimod (p < 0.01 vs. placebo) were noted. The number of qPCR-positive recurrent swabs, ranged from 5 to 11% in the vaccinated+local imiquimod groups compared 29% in the PBS control group (P < 0.05). No recurrent swab samples from vaccinated groups were culture positive. We conclude that the strategy of prime (subunit HSV vaccine) and topical pull (intravaginal/topical imiquimod) decreased recurrent HSV more effectively than vaccine alone.

“Prime and pull” vaccination strategies involve an initial vaccination followed by the local application of a stimulant such as chemokines to recruit immune cells to infection target areas such as the mucosa. David Bernstein and colleagues investigate the efficacy of a prime and pull approach in a guinea pig model of recurrent genital Herpes simplex virus 2 (HSV-2) infection. Animals were vaccinated with HSV-2 glycoproteins in adjuvant with or without subcutaneous or topical (vaginal) exposure to the immune stimulant imiquimod to act as the “pull”. Animals with topical imiquimod show superior control of HSV-2 infection and improved recruitment of CD8⁺ T cells to the vaginal epithelium. Topical application of imiquimod demonstrates better control than subcutaneous imiquimod suggesting that “pulling” might be a useful approach in HSV vaccination.

In vivo microbiome and associated immune markers: New insights into the pathogenesis of vaginal dysbiosis

The microbiota fulfils a key role in the training and function of the immune system, which contributes to the symbiosis between the host and complex microbial communities. In this study, we characterized the interplay between vaginal bacteria and local immune mediators during dysbiosis in selected women of reproductive age who were grouped according to Nugent’s criteria. The abundance of Gardnerella vaginalis and Bifidobacterium breve was increased in the intermediate dysbiotic status, while the presence of a plethora of non-resident bacteria characterized the group with overt vaginosis. In response to these increases, the anti-inflammatory IL1ra and pro-inflammatory IL2 increased, while the embryo trophic factors FGFβ and GMCSF decreased compared to the healthy milieu. A specific pattern, including IL1α, IL1β, IL8, MIG, MIP1α and RANTES, distinguished the intermediate group from the vaginosis group, while IL5 and IL13, which are secreted by Th2 cells, were significantly associated with the perturbation of the commensals Lactobacilli, Gardnerella and Ureaplasma. Summarizing, we postulate that although the dysbiotic condition triggers a pro-inflammatory process, the presence of a steady state level of Th2 may influence clinical manifestations. These results raise clinically relevant questions regarding the use of vaginal immunological markers as efficacious tools to monitor microbial alterations.

Insights on the mechanism of action of immunostimulants in relation to their pharmacological potency. The effects of imidazoquinolines on TLR8

Imidazoquinolines are powerful immunostimulants (IMMS) that function through Toll-like receptors, particularly TLR7 and TLR8. In addition to enhancing the immune response, IMMS also function as antineoplastic drugs and vaccine adjuvants. These small compounds display almost the same molecular structure, except in some cases in which atom in position 1 varies and changes the imidazole characteristics. A variable acyclic side chain is also always attached at atom in position 2, while another chain may be attached at atom in position 1. These structural differences alter immune responses, such as the production of interferon regulatory factor and nuclear factor-κB (IRF-NFκB). In this work, quantum mechanics theory and computational chemistry methods were applied to study the physicochemical properties of the crystal binding site of TLR8 complexed with the following six IMMS molecules: Hybrid-2, XG1-236, DS802, CL075, CL097 and R848 (resiquimod). The PDB IDs of the crystals were: 4R6A, 4QC0, 4QBZ, 3W3K, 3W3J, and 3W3N respectively. Thus, were calculated, the total energy, solvation energy, interaction energy (instead of free energy) of the system and interaction energy of the polar region of the IMMS. Additionally, the dipole moment, electrostatic potential, polar surface, atomic charges, hydrogen bonds, and polar and hydrophobic interactions, among others, were assessed. Together, these properties revealed important differences among the six TLR8-immunostimulant complexes, reflected as different interaction energies and therefore different electrostatic environments and binding energies. Remarkably, the interaction energy of a defined polar region composed of the highly polarized N3, N5 atoms and the N11 amino group, acted as a polar pharmacophore that correlates directly with the reported immunopharmacological potency of the six complexed molecules. Based on these results, it was concluded that accurate physicochemical analysis of the crystal binding site could reveal the binding energy (measured as interaction energy) and associated molecular mechanism of action between IMMS and TLR8. These findings may facilitate the development and design of improved small molecules with IMMS properties that are targeted to the TLR system and have enhanced pharmacological effectiveness and reduced toxicity.

Viral and Nonviral Uses of Imiquimod: A Review

Background:

Imiquimod is a topical immunomodulator that is indicated for the treatment of external genital and perianal warts. This drug has been recently approved for the treatment of actinic keratoses and superficial basal cell carcinoma. There is a growing body of evidence for its effectiveness in treating a variety of other skin conditions.

Objective:

This review examines the role of imiquimod 5% cream in the treatment of skin diseases such as actinic keratoses, basal cell carcinoma, Bowen's disease, lentigo maligna, and extramammary Paget's disease.

Methods:

Published literature containing the words “Imiquimod” or “Aldara” was reviewed and summarized.

Results:

This agent has demonstrated indirect antiviral and antitumor effects in animal models. Although the exact mechanism of action is unknown, imiquimod is an agonist for toll-like receptor (TLR) 7 and is thought to act by inducing cytokines, such as interferon alpha (IFN-α), interleukin-12 (IL-12), and tumor necrosis factor alpha (TNF-α). These cytokines trigger the immune system to recognize the presence of a viral infection or tumor and the associated lesion is ultimately eradicated. Side effects are generally well tolerated with local skin reactions reported most frequently.

Conclusion:

Imiquimod has been shown to be a safe and effective treatment for a variety of skin conditions.

Prophylactic and therapeutic modulation of innate and adaptive immunity against mucosal infection of herpes simplex virus

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) are the most common cause of genital ulceration in humans worldwide. Typically, HSV-1 and 2 infections via mucosal route result in a lifelong latent infection after peripheral replication in mucosal tissues, thereby providing potential transmission to neighbor hosts in response to reactivation. To break the transmission cycle, immunoprophylactics and therapeutic strategies must be focused on prevention of infection or reduction of infectivity at mucosal sites. Currently, our understanding of the immune responses against mucosal infection of HSV remains intricate and involves a balance between innate signaling pathways and the adaptive immune responses. Numerous studies have demonstrated that HSV mucosal infection induces type I interferons (IFN) via recognition of Toll-like receptors (TLRs) and activates multiple immune cell populations, including NK cells, conventional dendritic cells (DCs), and plasmacytoid DCs. This innate immune response is required not only for the early control of viral replication at mucosal sites, but also for establishing adaptive immune responses against HSV antigens. Although the contribution of humoral immune response is controversial, CD4(+) Th1 T cells producing IFN-γ are believed to play an important role in eradicating virus from the hosts. In addition, the recent experimental successes of immunoprophylactic and therapeutic compounds that enhance resistance and/or reduce viral burden at mucosal sites have accumulated. This review focuses on attempts to modulate innate and adaptive immunity against HSV mucosal infection for the development of prophylactic and therapeutic strategies. Notably, cells involved in innate immune regulations appear to shape adaptive immune responses. Thus, we summarized the current evidence of various immune mediators in response to mucosal HSV infection, focusing on the importance of innate immune responses.

Topical SMIP-7.7, a toll-like receptor 7 agonist, protects against genital herpes simplex virus type-2 disease in the guinea pig model of genital herpes

BACKGROUND

Development of more effective therapies for genital herpes simplex virus type-2 (HSV-2) infections remains a priority. The toll-like receptors (TLR) are attractive targets for the immunomodulation of primary and recurrent genital herpes infection. The guinea pig model of genital HSV-2 disease was therefore used to evaluate the efficacy of a new TLR-7 agonist, SMIP-7.7.

METHODS

The effects of SMIP-7.7 at concentrations between 0.90% and 0.09% were compared to the vehicle control or Aldara(®) (3M Health Care Limited, Northridge, CA, USA) as treatment for genital HSV-2 infections. Following intravaginal inoculation of Hartley guinea pigs with 10(6) pfu HSV-2 (MS strain), animals were treated intravaginally beginning at 36 h post-infection. Animals were evaluated for acute disease, acute virus replication, recurrent disease and shedding, as well as infection of the dorsal root ganglia.

RESULTS

Treatment with SMIP-7.7 significantly decreased mean total lesion scores during primary infection (all doses, P<0.01 compared with vehicle control, and similar to Aldara(®)). Vaginal virus titres were reduced in treated animals compared with vehicle control (P<0.001 for each treatment versus vehicle control on day 4). Treatment with SMIP-7.7 also significantly decreased the number of recurrent lesion days, the number of days with recurrent virus shedding and the infection of the dorsal root ganglia compared to the vehicle control, and was similar to Aldara(®). As opposed to Aldara(®), SMIP-7.7 did not induce fever or weight loss during treatment.

CONCLUSIONS

SMIP-7.7 improves the outcome of primary and recurrent HSV-2 disease comparable to Aldara(®) but without some of the side effects associated with Aldara(®).

Involvement of interferon-gamma genetic variants and intercellular adhesion molecule-1 in onset and progression of generalized vitiligo

Interferon-gamma (IFN-γ) is a paracrine inhibitor of melanocytes and genetic variability due to intron 1 polymorphisms in IFNG has been reported to be associated with increased risk for several autoimmune diseases. The aim of present study was to determine whether intron 1 +874A/T (rs2430561) and CA microsatellite (rs3138557) polymorphisms in IFNG are associated with generalized vitiligo (GV) susceptibility and expression of IFNG and intercellular adhesion molecule-1 (ICAM1) affects the disease onset and progression. Here we report that IFNG CA microsatellite but not +874A/T may be a genetic risk factor for GV; however, +874T allele plays a crucial role in increased expression of IFNG mRNA and protein levels which could affect the onset and progression of the disease. Active GV patients showed increased IFNG levels compared to stable GV patients. The genotype-phenotype analysis revealed that IFNG expression levels were higher in patients with +874 TT genotypes and 12 CA repeats. Patients with the early age of onset showed higher IFNG expression and female GV patients showed higher IFNG and ICAM1 expression implicating gender biasness and involvement of IFN-γ in early onset of the disease. Moreover, the increased IFN-γ levels in patients lead to increased ICAM1 expression, which could be a probable link between cytokines and T-cell involvement in pathogenesis of GV.

Focal epithelial hyperplasia - an update

Focal epithelial hyperplasia (FEH) is an asymptomatic benign mucosal disease, which is mostly observed in specific groups in certain geographical regions. FEH is usually a disease of childhood and adolescence and is generally associated with people who live in poverty and of low socioeconomic status. Clinically, FEH is typically characterized by multiple, painless, soft, sessile papules, plaques or nodules, which may coalesce to give rise to larger lesions. Human papillomavirus (HPV), especially genotypes 13 and 32, have been associated and detected in the majority of FEH lesions. The clinical examination and social history often allow diagnosis, but histopathological examination of lesional tissue is usually required to confirm the exact diagnosis. FEH sometimes resolves spontaneously however, treatment is often indicated as a consequence of aesthetic effects or any interference with occlusion. There remains no specific therapy for FEH, although surgical removal, laser excision or possibly topical antiviral agents may be of benefit. There remains no evidence that FEH is potentially malignant.

Imiquimod suppresses propagation of herpes simplex virus 1 by upregulation of cystatin A via the adenosine receptor A1 pathway

Imiquimod is recognized as an agonist for Toll-like receptor 7 (TLR7) in immunocompetent cells. TLR7, as well as TLR3 and TLR8, triggers the immune responses, such as the production of type I interferons (IFNs) and proinflammatory cytokines via recognition of viral nucleic acids in the infected cells. In this study, we proposed that imiquimod has an IFN-independent antiviral effect in nonimmune cells. Imiquimod, but not resiquimod, suppressed replication of human herpes simplex virus 1 (HSV-1) in FL cells. We analyzed alternation of gene expression by treatment with imiquimod using microarray analysis. Neither type I IFNs, nor TLRs, nor IFN-inducible antiviral genes were induced in imiquimod-treated FL cells. Cystatin A, a host cysteine protease inhibitor, was strongly upregulated by imiquimod and took a major part in the anti-HSV-1 activity deduced by the suppression experiment using its small interfering RNA. Upregulation of cystatin A was suggested to be mediated by antagonizing adenosine receptor A(1) and activating the protein kinase A pathway. Imiquimod, but not resiquimod, was shown to interact with adenosine receptor A(1). Imiquimod-induced anti-HSV-1 activity was observed in other cells, such as HeLa, SiHa, and CaSki cells, in a manner consistent with the cystatin A induction by imiquimod. These results indicated that imiquimod acted as an antagonist for adenosine receptor A(1) and induced a host antiviral protein, cystatin A. The process occurred independently of TLR7 and type I IFNs.

Mucosal treatments for herpes simplex virus: insights on targeted immunoprophylaxis and therapy

Herpes simplex virus (HSV) serotypes 1 and 2 establish lifelong infections that can produce reactivated pools of virus at mucosal sites where primary infections were initiated. No approved vaccines are available. To break the transmission cycle, interventions must either prevent infection or reduce infectivity at mucosal sites. This article discusses the recent experimental successes of immunoprophylactic and therapeutic compounds that enhance resistance and/or reduce viral loads at genital and ocular mucosa. Current data indicate Toll-like receptor agonists and selected immunomodulating compounds effectively increase the HSV infection threshold and hold promise for genital prophylaxis. Similarly, immunization at genital and extragenital mucosal sites is discussed. Finally, preclinical success with novel immunotherapies for ocular HSV that address herpetic keratitis and corneal blindness is reviewed.

Efficiency of anaferon in complex therapy of genital herpes

We studied clinical efficiency and IFN-inducing activity of anaferon in chronic recurrent genital herpes with high incidence of relapses. The use of anaferon in complex therapy reduced the duration of intoxication symptoms and local symptoms, shortened the duration of the relapse, activated expression of IFN-gamma mRNA, and improved IFN-gamma-producing capacity of blood leukocytes.

Treatment of feline herpesvirus-1 associated disease in cats with famciclovir and related drugs

BACKGROUND

Feline herpesvirus 1 (FHV-1) is a common cause of ocular and upper respiratory disease in cats and kittens, and a potential cause of eosinophilic dermatitis.

HYPOTHESIS

The systemic anti-herpes drug, famciclovir (Famvir; Novartis), would be effective in the clinical management of disease attributable to FHV-1, including conjunctivitis, keratitis, corneal sequestra, rhinosinusitis and FHV-1 associated dermatitis.

CLINICAL OUTCOME

Oral famciclovir was used to treat signs considered referable to FHV-1 in 10 cats: four had primary ocular disease, two had rhinosinusitis and four had FHV-1 associated dermatitis. Patients treated in Australia (five cats) and Europe (one cat) were given 62.5 mg of famciclovir once or twice daily. Four cats treated in the USA were given 125 mg three times daily. Famciclovir was uniformly well tolerated and, in all cases, had a positive impact on the patient's condition. The apparent improvement in lesions was superior to what had been achieved previously using other therapeutic strategies. One cat with severe destructive rhinosinusitis was significantly improved by a 4-month course of famciclovir in combination with antibacterials. Corneal sequestra detached in two out of three cats treated; cats with ocular signs were qualitatively more comfortable, with reduced clinical signs and an improved appearance of the eyes. Critically, oral famciclovir therapy was considered more convenient than topical ocular therapy. All four cats with FHV-1 associated dermatitis improved substantially, although relapse occurred subsequently in three patients. A further cat with presumptive FHV-1 associated dermatitis responded to topical aciclovir cream before famciclovir could be sourced.

CONCLUSIONS

Famciclovir appears to be a promising systemic drug for treating diseases associated with FHV-1 infection. More rigorous clinical trials are required to optimise the dosing regimen for safe and effective specific anti-herpes treatment in feline clinical medicine.

TLR7 and CD40 cooperate in IL-6 production via enhanced JNK and AP-1 activation

During vaccination or infection, adaptive and innate immune receptors of B cells are engaged by microbial antigens/ligands. A better understanding of how innate and adaptive signaling pathways interact could enlighten B lymphocyte biology as well as aid immunotherapy strategies and vaccine design. To address this goal, we examined the effects of TLR stimulation on BCR and CD40-induced B cell activation. Synergistic production of IL-6 was observed in both human and mouse primary B cells stimulated through B cell antigen receptors, CD40 and TLR7, and these two receptors also cooperated independently of BCR signals. The enhanced IL-6 production was dependent upon the activity of c-Jun kinase (JNK) and cFos. Dual stimulation through CD40 and TLR7 markedly enhanced JNK activity. The increased level of active JNK in dual-stimulated cells was accompanied by an increase in the level of active AP-1 monomers cJun and cFos. The stimulation of B cells through both CD40 and TLR7 therefore enhanced the production of cytokines through increased JNK signaling and AP-1 activity. In addition, the dual stimulation increased cFos/AP-1 species in stimulated cells, effectively expanding the repertoire of AP-1 dimers as compared to singly stimulated B cells.

TLR7 and TLR8 as targets in cancer therapy

Small-molecule agonists at Toll-like receptor 7 (TLR7) and TLR8 have sparked a vivid interest in cancer research owing to their profound antitumoral activity. The lead compound of the imidazoquinoline family, imiquimod, is marketed as a topical formulation. It is efficacious against many primary skin tumors and cutaneous metastases. Using different imidazoquinoline species, distinct functions of TLR7 and TLR8 have been discovered. The predominant antitumoral mode of action of these agents is TLR7/8-mediated activation of the central transcription factor nuclear factor-kappaB, which leads to induction of proinflammatory cytokines and other mediators. Cutaneous dendritic cells are the primary responsive cell type and initiate a strong Th1-weighted antitumoral cellular immune response. Recent research has shown that dendritic cells themselves acquire direct antitumoral activity upon stimulation by imiquimod. In addition, there are a number of secondary effects on the molecular and cellular level that can be explained through the activation of TLR7/8. The proinflammatory activity of imiquimod, but not resiquimod, appears to be augmented by suppression of a regulatory mechanism, which normally limits inflammatory responses. This is achieved independently of TLR7/8 through interference with adenosine receptor signaling pathways. Finally, at higher concentrations imiquimod exerts Bcl-2- and caspase-dependent proapoptotic activity against tumor cells.

Possible mechanisms in the induction of vitiligo-like hypopigmentation by topical imiquimod

The pathogenesis of vitiligo was examined for clues to the pigmentary changes that may occur after treatment with topical imiquimod. The literature varies on the pigmentary changes induced by topical use of imiquimod. The US Food and Drugs Administration lists 68 reports of pigmentary changes out of a total of 1257 reports related to imiquimod lodged from 1997 to 2003. Some studies describe vitiligo-like hypopigmentation associated with imiquimod treatment of genital warts (as with the patient described in this report), molluscum contagiosum, basal cell carcinoma, extramammary Paget's disease and murine melanoma. Other studies report hyperpigmentation associated with imiquimod. The possible mechanisms of hypopigmentation associated with imiquimod treatment are discussed, including antibodies found in sera of patients with vitiligo to nonpigment cell antigens, cytoplasmic pigment cell antigens and pigment cell-surface antigens; stimulation by imiquimod of both the innate immune response and cell-mediated adaptive immunity; and increased sensitivity of melanocytes to oxidative stress. The vitiligo-like hypopigmentation following topical imiquimod treatment is in line with the mode of action of this drug.

Correlation between the nature of immunity induced by different immunogens and the establishment of latent infection by wild-type pseudorabies virus

To assess the correlation between the nature of immunity induced by different types of immunogens and the establishment of latent infection by wild-type pseudorabies virus (PrV), we used a murine model immunized with different immunogens, the PrV modified live vaccine (MLV), inactivated vaccine (IAV), and commercial oil-adjuvant subunit vaccine (OSV), via either intranasal (i.n.) or intramuscular (i.m.) route. Both MLV and IAV induced a different nature of immunity biased to Th1- and Th2-type, respectively, as judged by the ratio of PrV-specific IgG isotypes (IgG2a/IgG1) and the profile of cytokine IL-2, IL-4, and IFN-gamma production. In contrast, the OSV induced a lower isotype IgG2a to IgG1 ratio and higher level of IL-2 production. The MLV (inducing Th1-type) provided more effective protection against a virulent wild-type PrV challenge than IAV and OSV (inducing Th2- and mixed type, respectively). In addition, the MLV impeded the establishment of a latent infection with wild-type PrV, and the decrease in the PrV latency load by immunization with the MLV appeared to be mediated by the immune T-cells. These results demonstrate the substantial role of the immune responses driven by preceding vaccination in modulating the establishment of PrV latency caused by the post-infection of a field virus.

In vitro effects of recombinant zebrafish IFN on spring viremia of carp virus and infectious hematopoietic necrosis virus

In order to evaluate the effects of fish recombinant interferon (rIFN) on fish pathogenic rhabdoviruses, the zebrafish (Danio rerio) IFN (DreIFN) allele B gene was cloned and expressed in Escherichia coli. In addition, the effects of recombinant DreIFN (rDreIFN) on spring viremia of carp virus (SVCV), infectious hematopoietic necrosis virus (IHNV), and vesicular stomatitis virus (VSV) were surveyed in fish and chicken cells. The mature peptide of DreIFN allele B gene encodes 163 amino acids. Residues 3 and 98 are a pair of cysteines that likely form an intrachain disulfide bridge. rDreIFN protein was detected as a band at 21.6 kDa by SDS-PAGE. The purified rDreIFN has anti-SVCV and anti-IHNV activity of 3 x 10(4) U/mg-10(7) U/mg. The results indicate that rDreIFN has higher activity against SVCV and IHNV on epithelioma papulosum cyprinid (EPC) than on grass carp (C. idellus) ovary (CO) cell lines and no activity against VSV on chick embryo fibroblasts (CEF).

CpG oligodeoxynucleotides protect newborn mice from a lethal challenge with the neurotropic Tacaribe arenavirus

The innate immune system is key to limiting the early spread of most pathogens and directing the development of Ag-specific immunity. Recently, a number of synthetic molecules that activate the innate immune system by stimulating TLRs have been identified. Among them, synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs (CpG ODNs) were shown to activate TLR9-bearing B cells, macrophages, and dendritic cells to induce a strong proinflammatory milieu and a type 1-biased immune response that protects mice from a variety of parasitic, bacterial, and viral infections. Although the protective effect of CpG ODN in adult mice was well established, its effectiveness in neonates, which have lower numbers of dendritic, B, and T cells and tend to favor Th2 responses, was unclear. This study uses the New World arenavirus Tacaribe, a neurotropic pathogen that is lethal in newborn mice, to explore the effectiveness of TLR-mediated innate immune responses. Neonatal BALB/c mice treated with CpG ODN at the time of infection had reduced viral load (p < 0.01) and increased survival (52%, p < 0.001 i.p.; 36%, p < 0.05 intranasally). Protection was achieved in mice treated no later than 3 days postchallenge and appears to be mediated by an increase in Ag-specific Abs (IgG and IgM) and to require inducible NO synthase expression and NO production. To our knowledge, this is the first study assessing the mechanisms by which CpG ODN can protect mice from a neurotropic viral infection.

Viral and Nonviral Uses of Imiquimod: A Review

BACKGROUND

Imiquimod is a topical immunomodulator that is indicated for the treatment of external genital and perianal warts. This drug has been recently approved for the treatment of actinic keratoses and superficial basal cell carcinoma. There is a growing body of evidence for its effectiveness in treating a variety of other skin conditions.

OBJECTIVE

This review examines the role of imiquimod 5% cream in the treatment of skin diseases such as actinic keratoses, basal cell carcinoma, Bowen's disease, lentigo maligna, and extramammary Paget's disease.

METHODS

Published literature containing the words "Imiquimod" or "Aldara" was reviewed and summarized.

RESULTS

This agent has demonstrated indirect antiviral and antitumor effects in animal models. Although the exact mechanism of action is unknown, imiquimod is an agonist for toll-like receptor (TLR) 7 and is thought to act by inducing cytokines, such as interferon alpha (IFN-alpha), interleukin-12 (IL-12), and tumor necrosis factor alpha (TNF-alpha). These cytokines trigger the immune system to recognize the presence of a viral infection or tumor and the associated lesion is ultimately eradicated. Side effects are generally well tolerated with local skin reactions reported most frequently.

CONCLUSION

Imiquimod has been shown to be a safe and effective treatment for a variety of skin conditions.

Topical Immunotherapy: What's New

Further understanding of the pathogenesis of dermatologic conditions at a molecular level has led to targeted therapies. The topical immune response modifiers have contributed significantly to the treatment of cutaneous diseases. New topical remedies, particularly the Toll-like receptor agonists and calcineurin inhibitors, have added to the clinical armamentarium and have further advanced clinicians' ability to treat a wide variety of benign, premalignant, and malignant conditions. Furthermore, these agents have contributed to the understanding of the disease process. The next decade will witness even greater advances in targeted immunotherapies for dermatologic disease.

Mechanism of Action and Emerging Role of Immune Response Modifier Therapy in Dermatologic Conditions

Immune response modifiers (IRMs) are agents that target the body's immune system (i.e., cytokines, receptors, and inflammatory cells) to combat disease. Topical IRM therapies, which encompass both proinflammatory and immunosuppressive therapeutics, have been used to successfully treat a number of dermatologic conditions. Proinflammatory treatments include Toll-like receptor agonists (e.g., imiquimod 5% cream) and interferon (e.g., interferon-alpha) therapies, which have been used in the treatment of external genital warts, basal cell carcinoma, and other dermatologic diseases. Immunosuppressive therapies include topical and intralesional corticosteroids, anti-tumor necrosis factor agents (e.g., infliximab and etanercept), and anti-CD4+ T-cell agents, including calcineurin inhibitors and mycophenolate. These agents have been used to treat a number of conditions, including atopic and seborrheic dermatitis and psoriasis. This article reviews the mechanism of action of IRMs and the application of IRMs in several dermatologic diseases.

Effect of interferon-alpha and interferon-inducers on West Nile virus in mouse and hamster animal models

The recent West Nile virus (WNV) outbreak in the United States has increased the need to identify effective therapies. Studies were conducted in cell culture and in rodent animal models to determine the efficacy of interferon-alpha (IFN-alpha), interferon (IFN) inducers and ribavirin, alone or in combination with IFN, in treating WNV. Intraperitoneal injection of IFN-alpha B/D (qd for 7 days), polyI-polyC(12)U [Ampligen (every other day for 7 days)] and topically applied imiquimod (qd for 7 days), administered from 1 day before viral challenge, were effective in protecting, respectively, 100%, 100% and 70% of BALB/c mice from mortality induced by subcutaneous injection of WNV. When IFN-alpha B/D or Ampligen treatments were delayed to 4-6 h before viral challenge in mice, efficacy was greatly diminished. Infected Syrian golden hamsters treated with interferon alphacon-1 (Infergen) and Ampligen 4-6 h before viral challenge gained more weight and had a greater survival than saline-treated animals. A combination study of subcutaneously administered Infergen (5 to 0.05 microg/kg/day) and ribavirin (75 to 7.5 mg/kg/day) in >7 week old hamsters demonstrated that Infergen was slightly efficacious in reducing mortality and disease signs; however, it was not synergistic in its antiviral effects when combined with ribavirin. Ribavirin treatment alone increased mortality of infected hamsters. The reduced mortality correlated with reduced plasma viraemia. Since WNV-infected patients have already been treated with IFN and ribavirin and future clinical trials have been suggested, this first report of IFN alone or in combination with ribavirin in WNV-infected animal models might provide useful information for subsequent treatment of patients.

Resiquimod is a modest adjuvant for HIV-1 gag-based genetic immunization in a mouse model

DNA vaccines have been effective at generating useful immune responses in many animal species. However, it is clearly desirable to increase their potency. The identification of adjuvants that increase their cell-mediated immune (CMI) response is therefore an important goal. Resiquimod is an imiquimod analog proven to activate dendritic cells through TLR-7. The adjuvant capacity of resiquimod has not, to our knowledge, been studied in the context of genetic immunization. Here, we studied resiquimod as an adjuvant for plasmid vaccine therapy by intra-muscular immunization of BALB/c mice with HIV-1 gag DNA vaccine without and with several concentrations of resiquimod (ranging from 5-100nM). We observed that resiquimod moderately enhanced IFN-gamma production as measured by a peptide-based ELISPOT assay compared to that obtained in mice immunized with DNA gag only. Antigen-specific T-cell proliferation studies showed a several-fold increase in the stimulation index in mice immunized with DNA gag +50 nM of resiquimod as compared to mice receiving DNA gag alone. Antibody titer also increased, while the antibody isotyping data showed a strong Th1 biased type response. Analysis of cytokine production in serum samples demonstrated a stronger Th1 cytokine bias in the presence of resiquimod. Furthermore, relevant increase in IL-4 production, as measured by ELISPOT assay, was not observed. Our results show that resiquimod can have modest adjuvant activity, in a DNA formulation, driving the immune system towards a cell-mediated immune response. Additional studies involving this adjuvant for DNA vaccines are underway.

The imidazoquinolines and their place in the therapy of cutaneous disease

The imidazoquinolines arose from efforts to develop a nucleoside analogue. Although molecularly similar to nucleosides, the imidazoquinolines did not have nucleoside-like activity. However, the imidazoquinolines induced immune modulatory cytokines, in part, because of their ability to activate toll receptors (TLR)s. Imiquimod, the first FDA-approved imidazoquinoline, has been marketed as a 5% cream, which is approved for the therapy of genital warts. The advantage of imiquimod therapy over other therapies for genital warts is the decrease in recurrence rate with the establishment of an adaptive immunological response or immunological memory/surveillance response. As tumours and viral infections are handled similarly by the immune system, there has been great interest in the use of topical imiquimod for the treatment of cutaneous neoplasms, particularly non-melanoma skin cancers. Future efforts in imidazoquinoline research is focused around the development of analogues with modifications in the immunological profiles, potency and penetration parameters that better focus these new analogues for the therapy of specific intracellular infections and neoplasms, as well as the development of imidazoquinolines for conditions related either directly or indirectly to patterns of immune dysregulation.

Imiquimod

PURPOSE OF REVIEW

Imiquimod is the first member of a new class of immune response modifiers; it was first approved in 1997 for the topical treatment of external genital and perianal warts. It is an imidazoquinoline, a novel synthetic compound which is an immune response stimulator, enhancing both the innate and acquired immune pathways (particularly T helper cell type 1-mediated immune responses) resulting in antiviral, antitumour and immunoregulatory activities. The mechanism of action of imiquimod involves cytokine induction in the skin, which then triggers the host's immune system to recognize the presence of a viral infection or tumour, ultimately to eradicate the associated lesion.

RECENT FINDINGS

Imiquimod, a patient-applied topical 5% cream is clinically efficacious and safe in the management of condylomata acuminata and other warty manifestations of human papillomavirus infections. Although not licensed for use against other viral skin infections, preliminary data suggest imiquimod's success against molluscum contagiosum, caused by a poxvirus. Initial studies with imiquimod for the management of HPV-related intraepithelial dysplasias (bowenoid papulosis/vulvar intraepithelial neoplasia) as well as for ultraviolet-induced skin lesions such as actinic keratoses, Bowen's disease, and basal cell carcinomas show great promise in immunocompetent and immunosuppressed patients.

SUMMARY

In the future, imiquimod and newer generations of imidazoquinolines (resiquimod) require further investigation for potential clinical utility in treating other cutaneous and mucosal viral infections, dysplasias and neoplasia, as well as potential vaccine adjuvants.

Pathogenesis and potential antiviral therapy of complications of smallpox vaccination

Vaccination against smallpox may result in a variety of complications, ranging in severity from benign to lethal. Universal vaccination was halted in the US in 1972, so almost half the present population has never been vaccinated. Because side effects occur most often in first-time vaccinees, current plans for rapid large-scale vaccination in the event of bioterrorist attack raise concerns about the occurrence of a large number of adverse events. Most complications result from the excessive replication of vaccinia virus, making them potential targets for antiviral therapy. Effective treatment is especially needed for persons with atopic dermatitis or eczema, who are unusually susceptible to the initiation and spread of vaccinia infection because of defects of innate immunity in the skin, and for individuals with defective cell-mediated immunity, who are unable to eliminate vaccinia infection once it has begun. In the past, many complications were treated with vaccinia immune globulin (VIG) and/or the antiviral drug methisazone, but neither was tested in placebo-controlled trials. New antiviral drugs are now available, but have not yet been evaluated for treating vaccinia infections in humans. Both laboratory research and clinical studies are needed to help prevent serious complications in any major vaccination campaign.

Therapeutic Options for Herpes Simplex Infections

Herpes simplex viruses are responsible for a number of disease states in infected individuals. Capable of establishing latent infection, herpes simplex can reactivate, causing pain, discomfort, and psychosocial consequences. Because no cure is available, treatment modalities for herpes simplex infection are required, from both personal and public health standpoints. To date, therapy has centered around the use of antiviral drugs to control infection and suppress recurrences. To expand the scope of available treatments, efforts have focused on the development of vaccines against herpes simplex virus and new agents such as immune response modifiers. Recent data suggest that these new agents are promising in their therapeutic potential.

Inhibition of IgE production by the imidazoquinoline resiquimod in nonallergic and allergic donors

The aim of this study was to examine whether the immune modulator resiquimod, which belongs like imiquimod to the imidazoquinolines, is capable of influencing IgE synthesis. Peripheral blood mono-nuclear cells from normal donors and patients with atopic dermatitis and with seasonal allergic rhinitis were analyzed in the presence of resiquimod, anti-CD40+interleukin-4 stimulation for induction of IgE, and anti-CD40+interleukin-4 in the presence of resiquimod, respectively. Our data show that spontaneous IgE production was inhibited in the presence of resiquimod, which was strongest at 10 ng per ml in both groups of allergic patients. Inhibition of IgE production after anti-CD40+interleukin-4 stimulation in the presence of resiquimod (10 ng per ml) was comparable between all the groups. In normal donors median inhibition of IgE synthesis was 93%, in seasonal allergic rhinitis patients 77%, and in patients with atopic dermatitis 72%. In order to rule out antiproliferative effects of resiquimod, which might influence IgE production, we also studied proliferation of peripheral blood mononuclear cells from normal donors, which remained unchanged in the presence of resiquimod at 0.1-10 ng per ml but was inhibited at 100 or 1000 ng per ml. In search of possible mechanisms responsible for the observed inhibition of IgE production, we analyzed the expression and production of molecules that are known to modulate IgE production, namely CD23 and interferon-gamma. CD23 expression on B cells was lower in the presence of resiquimod (10 ng per ml) in anti-CD40+interleukin-4 stimulated cells, whereas interferon-gamma was strongly induced (4-6-fold) by resiquimod (10 ng per ml). Furthermore, by using neutralizing interferon-gamma monoclonal antibodies, we show that inhibition of IgE production occurred in an interferon-gamma-dependent manner. Taken together our results show that resiquimod is a potent modulator of IgE production in vitro in normal but also in allergic donors.