Effects of therapy with an immunomodulator (imiquimod, R-837) alone and with acyclovir on genital HSV-2 infection in guinea-pigs when begun after lesion development

Engaging Pattern Recognition Receptors in Solid Tumors to Generate Systemic Antitumor Immunity

Malignant tumors frequently exploit innate immunity to evade immune surveillance. The priming, function, and polarization of antitumor immunity fundamentally depends upon context provided by the innate immune system, particularly antigen presenting cells. Such context is determined in large part by sensing of pathogen specific and damage associated features by pathogen recognition receptors (PRRs). PRR activation induces the delivery of T cell priming cues (e.g. chemokines, co-stimulatory ligands, and cytokines) from antigen presenting cells, playing a decisive role in the cancer immunity cycle. Indeed, endogenous PRR activation within the tumor microenvironment (TME) has been shown to generate spontaneous antitumor T cell immunity, e.g., cGAS-STING mediated activation of antigen presenting cells after release of DNA from dying tumor cells. Thus, instigating intratumor PRR activation, particularly with the goal of generating Th1-promoting inflammation that stokes endogenous priming of antitumor CD8⁺ T cells, is a growing area of clinical investigation. This approach is analogous to in situ vaccination, ultimately providing a personalized antitumor response against relevant tumor associated antigens. Here I discuss clinical stage intratumor modalities that function via activation of PRRs. These approaches are being tested in various solid tumor contexts including melanoma, colorectal cancer, glioblastoma, head and neck squamous cell carcinoma, bladder cancer, and pancreatic cancer. Their mechanism (s) of action relative to other immunotherapy approaches (e.g., antigen-defined cancer vaccines, CAR T cells, dendritic cell vaccines, and immune checkpoint blockade), as well as their potential to complement these approaches are also discussed. Examples to be reviewed include TLR agonists, STING agonists, RIG-I agonists, and attenuated or engineered viruses and bacterium. I also review common key requirements for effective in situ immune activation, discuss differences between various strategies inclusive of mechanisms that may ultimately limit or preclude antitumor efficacy, and provide a summary of relevant clinical data.

Current and future direction in treatment of HPV-related cervical disease

Human papillomavirus (HPV) is the most common sexually transmitted virus in the world. About 70% of cervical cancers are caused by the most oncogenic HPV genotypes of 16 and 18. Since available prophylactic vaccines do not induce immunity in those with established HPV infections, the development of therapeutic HPV vaccines using E6 and E7 oncogenes, or both as the target antigens remains essential. Also, knocking out the E6 and E7 oncogenes in host genome by genome-editing CRISPR/Cas system can result in tumor growth suppression. These methods have shown promising results in both preclinical and clinical trials and can be used for controlling the progression of HPV-related cervical diseases. This comprehensive review will detail the current treatment of HPV-related cervical precancerous and cancerous diseases. We also reviewed the future direction of treatment including different kinds of therapeutic methods and vaccines, genome-editing CRISPR/Cas system being studied in clinical trials. Although the progress in the development of therapeutic HPV vaccine has been slow, encouraging results from recent trials showed vaccine-induced regression in high-grade CIN lesions. CRISPR/Cas genome-editing system is also a promising strategy for HPV cancer therapy. However, its safety and specificity need to be optimized before it is used in clinical setting.

Trial watch: FDA-approved Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) have first been characterized for their capacity to detect conserved microbial components like lipopolysaccharide (LPS) and double-stranded RNA, resulting in the elicitation of potent (innate) immune responses against invading pathogens. More recently, TLRs have also been shown to promote the activation of the cognate immune system against cancer cells. Today, only three TLR agonists are approved by FDA for use in humans: the bacillus Calmette-Guérin (BCG), monophosphoryl lipid A (MPL) and imiquimod. BCG (an attenuated strain of Mycobacterium bovis) is mainly used as a vaccine against tuberculosis, but also for the immunotherapy of in situ bladder carcinoma. MPL (derived from the LPS of Salmonella minnesota) is included in the formulation of Cervarix®, a vaccine against human papillomavirus-16 and -18. Imiquimod (a synthetic imidazoquinoline) is routinely employed for actinic keratosis, superficial basal cell carcinoma, and external genital warts (condylomata acuminata). In this Trial Watch, we will summarize the results of recently completed clinical trials and discuss the progress of ongoing studies that have evaluated/are evaluating FDA-approved TLR agonists as off-label medications for cancer therapy.

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.

The immunomodulator, ammonium trichloro[1,2-ethanediolato-O,O']-tellurate, suppresses the propagation of herpes simplex virus 2 by reducing the infectivity of the virus progeny

Persistent investigations for the identification of novel anti-herpetic drugs are being conducted worldwide, as current treatment options are sometimes insufficient. The immunomodulator, ammonium trichloro[1,2‑ethanediolato‑O,O']‑tellurate (AS101), a non‑toxic tellurium (Ⅳ) compound, has been shown to exhibit anti‑viral activity against a variety of viruses in cell cultures and in animal models. In the present study, the anti‑viral activity of AS101 against herpes simplex virus (HSV)‑1 and 2 was investigated in vitro. The results demonstrated that AS101 significantly restricted HSV‑2-induced plaque formation and reduced the infectivity of the HSV‑2 yield, while HSV‑1 was affected to a lesser extent. The incubation of mature HSV‑1 and HSV‑2 viruses with AS101 had no effect on viral infectivity, indicating that the compound interrupts de novo viral synthesis. The addition of AS101 at up to 9 h post‑infection had almost the same effect as did the addition of the drug together with the virus (it maintained 80% of its total anti‑viral capacity). Quantitative PCR and immunofluoresence staining of viral structural proteins revealed that the viral DNA and protein synthesis stages were not interrupted by the administration of AS101. By contrast, in the presence of the compound, significantly fewer viable viruses (≥2 log reduction) were recovered from the AS10‑treated cell cultures. Of note, when we determined the viability of the intracellular virus, formed in the presence of the compound, a less severe (≤1 log) effect was observed. Taken together, these data strongly suggest that AS101 primarily interferes with late stages of viral replication, such as viral particle envelopment or egress, leading to the production of a defective virus progeny.

Superior efficacy of helicase-primase inhibitor BAY 57-1293 for herpes infection and latency in the guinea pig model of human genital herpes disease

The efficacy of BAY 57-1293, a novel non-nucleosidic inhibitor of herpes simplex virus 1 and 2 (HSV-1 and HSV-2), bovine herpesvirus and pseudorabies virus, was studied in the guinea pig model of genital herpes in comparison with the licensed drug valaciclovir (Valtrex). Early therapy with BAY 57-1293 almost completely suppressed the symptoms of acute HSV-2 infection, and reduced virus shedding and viral load in the sacral dorsal root ganglia by up to three orders of magnitude, resulting in decreased latency and a greatly diminished frequency of subsequent recurrent episodes. In contrast, valaciclovir showed only moderate effects in this set of experiments. When treatment was initiated late during the course of disease after symptoms were apparent, that is, a setting closer to most clinical situations, the efficacy of therapy with BAY 57-1293 was even more pronounced. Compared with valaciclovir, BAY 57-1293 halved the time necessary for complete healing. Moreover, the onset of action was fast, so that only very few animals developed new lesions after treatment commenced. Finally, in a study addressing the treatment of recurrent disease in animals whose primary infection had remained untreated BAY 57-1293 was efficient in suppressing the episodes. In summary, superior potency and efficacy of BAY 57-1293 over standard treatment with valaciclovir was demonstrated in relevant animal models of human genital herpes disease in terms of abrogating an HSV infection, reducing latency and the frequency of subsequent recurrences. Furthermore, BAY 57-1293 shortens the time to healing even if initiation of therapy is delayed.

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.

Immunomodulation by roquinimex decreases the expression of IL-23 (p19) mRNA in the brains of herpes simplex virus type 1 infected BALB/c mice

Herpes simplex virus (HSV) is a common neurotropic virus which infects epithelial cells and subsequently the trigeminal ganglia (TG) and brain tissue. We studied how immunomodulation with roquinimex (Linomide) affects the course of corneal HSV infection in BALB/c mice. BALB/c mice have also been used in a model for HSV-based vectors in treating an autoimmune disease of the central nervous system (CNS). We addressed the questions of how immunomodulation affects the local as well as the systemic immune response and whether roquinimex could facilitate the spread of HSV to the CNS. The cytokine response in the brain and TG was studied using a quantitative rapid real-time RT-PCR method. We were interested in whether immunomodulation affects the expression of the recently described Th1-cytokine IL-23p19 in the brain and TG. The expression of IL-23 mRNA was decreased in brains of roquinimex-treated BALB/c mice. Also the expression of IL-12p35 and IFN-gamma mRNAs decreased. No significant changes were seen in IL-4 and IL-10 mRNA expression. The cytokine response was also studied using supernatants of stimulated splenocytes by EIA. Roquinimex treatment suppressed the production of IFN-gamma and also the production of IL-10 in HSV-infected BALB/c mice.

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.

Effect of an immunomodulator on the efficacy of an attenuated vaccine against avian pneumovirus in turkeys

Since 1997, avian pneumovirus (APV) has caused estimated annual losses of $15 million to the Minnesota turkey industry. In order to develop an attenuated live vaccine against APV, we serially passaged a Minnesota isolate of APV (APV/MN/turkey/1-a/97) in vitro in cell cultures for 41 passages. Laboratory experiments with this high-passage virus (P41) indicated that the attenuated virus provided immunogenic protection to turkeys against challenge with virulent APV, although some birds showed mild to moderate dinical signs after inoculation. To reduce the residual pathogenicity of P41, while maintaining its immunogenicity, we decided to vaccinate turkeys with P41 in the presence of an immunomodulator, S-28828 (1-n-butyl-2-ethoxymethyl-1H-imidazo[4,5-c]quinolin-4-amine-hydrochloride), which is a potent cytokine inducer. The combined inoculation of S-28828 (5 mg/kg body weight) and P41 resulted in a significant reduction in the incidence of virus-induced clinical signs in comparison with birds that received P41 without immunomodulator (P < 0.05). Only 17% of birds inoculated with S-28828 + APV P41 showed mild respiratory symptoms at 5 days postinoculation as compared with 46% of the vaccinated turkeys that did not receive S-28828. Vaccination with either P41 or with P41 + S-28828 protected turkeys against dinical signs and viral replication after challenge with virulent APV. These results indicate that immunomodulators, such as S-28828, may act as good vaccine adjuvants that can reduce the pathogenicity but maintain the immunogenicity of partially attenuated vaccines.

Imiquimod

Imiquimod is the first of the immune response modifiers to stimulate a localized immune response to treat infectious skin conditions. The reported TLR-7 activation to provoke an immune response suggests that imiquimod might mimic a microbial antigen. The immune response initiated by induced production of IFN-alpha and TFN-alpha is specifically aimed at an infectious antigen and appears mediated (in part) by enhanced migration of Langerhans' cells to regional lymph nodes. The approved indication for imiquimod is for treatment of genital warts. The drug has demonstrated a 50% to 60% clearance rate and a 12% to 20% recurrence rate for this indication (Table 1). This recurrence rate is the lowest reported among the currently recommended treatment modalities. The self-applied treatment avoids costly and painful office-based procedures. Case reports and open-label studies have demonstrated the efficacy of imiquimod in treating some cases of common, plantar, and flat warts, as well as molluscum contagiosum and leishmaniasis. Common and plantar warts respond better to imiquimod in combination with cryosurgery, occlusion, and keratolytics. Reports of successful imiquimod treatment of granuloma annulare, alopecia areata, and vitiligo might suggest an infectious etiology to those conditions, although this hypothesis is highly speculative.

External genital warts: diagnosis, treatment, and prevention

External genital warts (EGWs) are visible warts that occur in the perigenital and perianal regions. They are due primarily to non-oncogenic human papillomavirus (HPV) types, usually types 6 and 11. Physical examination assisted by bright light and magnification is the recommended approach for primary diagnosis. Biopsy is indicated when EGWs are fixed to underlying structures or discolored or when standard therapies are not effective. Recurrences are common, and there is no single treatment that is superior to others. Among women with atypical squamous cells, molecular HPV testing may be useful in determining who should be referred for colposcopy. Condoms may provide some protection against HPV-related diseases and thus are recommended in new sexual relationships and when partnerships are not mutually monogamous. Because the efficacy of cesarean section in preventing vertical transmission of HPV infection from women with EGWs to their progeny has not been proved, it is not recommended.

Imiquimod 5-percent cream does not alter the natural history of recurrent herpes genitalis: a phase II, randomized, double-blind, placebo-controlled study

Present strategies for control of herpes genitalis recurrences require multiple daily doses of antiviral medication. Imiquimod, an immune response modifier, induces alpha interferon and interleukin-12; application in the presence of local herpes antigens during a recurrence may augment herpes simplex virus (HSV)-specific cell-mediated immunity. To test this theory, we performed a randomized, double-blind, placebo-controlled study of imiquimod 5% cream to assess safety and efficacy for decreasing recurrences. Patients with six or more recurrences of herpes genitalis per year applied study cream (imiquimod or placebo) to lesions one, two, or three times per week for 3 weeks for each recurrence during a 16-week treatment period. This was followed by a 16-week observation period. Of 124 patients randomized to the study, 103 completed the treatment period and 93 completed the observation period. The median times to first genital herpes recurrence were 53 days for those receiving placebo (n = 30) and 54, 60, and 64 days for those receiving imiquimod one time per week (n = 34), two times per week (n = 32), and three times per week (n = 28), respectively. The median annualized recurrence rates during the treatment period were 3.8, 4.9, 3.2, and 3.1, respectively. There were no statistically significant differences in the time to first recurrence or in the annualized recurrence rate between the imiquimod and placebo groups in either the treatment or the observation period. A trend in increased rates of local adverse events at the application site and a delay in lesion healing with more frequent dosing suggested a pharmacologic effect. Although clinical efficacy has been observed for imiquimod in other conditions in which a TH1-type immune response may be beneficial, including other viral infections such as those caused by human papillomavirus, no apparent effect on the short-term natural history of herpes genitalis recurrences was observed.

Plasmacytoid dendritic cells produce cytokines and mature in response to the TLR7 agonists, imiquimod and resiquimod

The immune response modifiers, imiquimod and resiquimod, are TLR7 agonists that induce type I interferon in numerous species, including humans. Recently, it was shown that plasmacytoid dendritic cells (pDC) are the primary interferon-producing cells in the blood in response to viral infections. Here, we characterize the activation of human pDC with the TLR7 agonists imiquimod and resiquimod. Results indicate that imiquimod and resiquimod induce IFN-alpha and IFN-omega from purified pDC, and pDC are the principle IFN-producing cells in the blood. Resiquimod-stimulated pDC also produce a number of other cytokines including TNF-alpha and IP-10. Resiquimod enhances co-stimulatory marker expression, CCR7 expression, and pDC viability. Resiquimod was compared throughout the study to the pDC survival factors, IL-3 and IFN-alpha; resiquimod more effectively matures pDC than either IL-3 or IFN-alpha alone. These results demonstrate that imidazoquinoline molecules directly induce pDC maturation as determined by cytokine induction, CCR7 and co-stimulatory marker expression and prolonging viability.

Reduction of recurrent HSV disease using imiquimod alone or combined with a glycoprotein vaccine

The aim of this study is to evaluate the effects of an immune modulator, imiquimod, given alone or in combination with an HSV vaccine on HSV immune responses and as immunotherapy of a genital recurrence model. After recovery from primary genital HSV infection, animals were randomized to placebo, 21 days of imiquimod plus a placebo vaccine, or 21 days of imiquimod plus an HSV-2 glycoprotein vaccine. Placebo or HSV vaccine was given in the footpad on days 16 and 37 after HSV-2 genital inoculation. Daily imiquimod or placebo was given subcutaneously in the shoulder on days 16 through 37. Genital recurrences were monitored and HSV specific NK activity, IL-2 response and ELISA antibody were assayed. For the entire 15 week observation period, imiquimod alone reduced recurrences 62.6%, while addition of HSV vaccine to imiquimod reduced recurrences 80.6% compared to placebo/placebo. The duration of significant recurrence reduction was more notable with the addition of vaccine. Imiquimod alone significantly reduced the weekly HSV recurrent disease in the first 10 weeks (53-94% reduction, mean 75.9%), as did imiquimod plus HSV-vaccine (71-98% reduction, mean 89.5%). In weeks 10-15, imiquimod alone reduced recurrences significantly only in week 10 (20-53% reduction, mean 33%), whereas the addition of vaccine extended the significant recurrence reduction to 14 weeks (44-71% reduction, mean 56.8%). The recurrence reduction is correlated to an increased HSV-induced in vitro IL-2 response and NK activity against HSV targets in treated groups. Both imiquimod and the imiquimod/vaccine combination significantly reduced genital HSV recurrences, but the combination extended the duration and extent of protection for recurrences compared to imiquimod alone. Enhanced HSV specific immune responses correlated to the protection.

The inhibitory effect of the imidazoquinolinamine S-28828 on the pathogenesis of a type II adenovirus in turkeys

In this study we show that a type I-IFN inducing compound, S-28828, modulated the pathogenesis of an avian type II adenovirus in turkeys. By itself, S-28828 induced a strong reaction in the spleen characterized by hyperplasia of the red and white pulps as well as an increase in lymphoid cell aggregations. Oral administration of S-28828 before the time of virus inoculation suppressed significantly (P<0.05) the replication of hemorrhagic enteritis virus (HEV) in turkeys. Two doses of 5 or 50 mg of S-28828 administered at 2 days before and at the day of virus inoculation inhibited HEV-induced pathological and histopathological lesions. Virus-induced apoptosis and reduced IgM-surface expression of B cells were suppressed by low dose S-28828 treatment. These results are of interest because mammalian adenoviruses were shown to be resistant to antiviral effects of type I IFN, the major effector cytokine induced by S-28828.

Immunopathogenesis of haemorrhagic enteritis virus (HEV) in turkeys

Infection of turkeys with the haemorrhagic enteritis virus (HEV), a type II avian adenovirus, results in varying rates of morbidity and mortality. The disease is characterised by splenomegaly, intestinal haemorrhage, sudden death and immunosuppression. The mechanisms of HEV immunopathogenesis and immunosuppression are not fully understood. Recent studies indicate that immune responses play a central role in disease pathogenesis. HEV infects B cells and macrophages and induces necrosis as well as apoptosis in infected and possibly in by-stander cells. The ability of the infected birds to mount an optimum humoral immune response as well as normal macrophage functions such as phagocytosis may be impaired. Elevated numbers of splenic CD4(+) cells during the acute phase of infection may be associated with viral clearance. Types I and II interferons (IFN) and pro-inflammatory cytokines such as interleukin-6 and tumour necrosis-like factors (TNF) are released at the peak of the infection. Cytokines may play a protective as well as a destructive role. While a massive release of proinflammatory cytokines may lead to systemic shock associated with haemorrhagic enteritis and death, release of IFNs may protect turkeys from the disease. Treatment with thalidomide, which is a potent TNF down-regulatory drug, prevented HEV-induced intestinal haemorrhage and treatment with an IFN-inducing chemical prevented HEV-replication and inhibited HEV-induced pathological and histopathological lesions.

Treatment of primary herpes simplex virus infection in guinea pigs by imiquimod

Imiquimod (also known as R-837 and S-26308) is an imidazoquinoline immune response modifier and is available in the US and several other countries for the treatment of external genital warts. Imiquimod has no direct antiviral activity but demonstrates efficacy in several animal models of virus infection. The drug is recognized by antigen presenting cells including monocytes, macrophages, B-cells and dendritic cells and induces these cells to produce cytokines including interferon-alpha (IFN-alpha) and others. Imiquimod's ability to inhibit primary lesion development in the guinea pig model of Herpes simplex virus (HSV) intravaginal infection was studied. Imiquimod given intravaginally reduced primary lesions, reduced virus shedding and reduced virus content of spinal cords from HSV infected guinea pigs. A single drug application of 0.5 mg/kg reduced lesion frequency when given between 24 h before inoculation to 16 h after inoculation. A single drug application of 5 mg/kg reduced lesion frequency and severity when administered between 72 h before inoculation to 24 h after inoculation. The antiviral effect resulting from interferon induction in the animal lasts much longer than the drug itself, thus imiquimod is different than drugs having direct antiviral activity. Twice daily drug application for 4 days was effective when initiated up to 72 h after inoculation, however, once lesions began to appear, imiquimod treatment was not able to stop lesion development. Imiquimod treatment inhibited lesion development and/or virus shedding in guinea pigs inoculated with HSV-1, HSV-2 or virus isolates resistant to acyclovir. Imiquimod is currently in clinical trials for treating human HSV infections.

Imiquimod applied topically: a novel immune response modifier and new class of drug

Imiquimod (S-26308, R-837) (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4 amine), an immune response modifier, demonstrates potent antiviral and antitumor activity in animal models (see structure in Fig. 1). The drug exhibits no direct antiviral or antiproliferative activity when tested in a number of cell culture systems. Imiquimod's activity was discovered while screening for anti-herpes virus activity. One of the first analogs in the series, S-25059 was tested in the early 1980's and due to slight toxicity, caused slightly reduced herpes cytopathology in Vero cell cultures. Follow-up testing in herpes infected guinea pigs showed complete protection toward lesion development. Activity of these drugs results primarily from interferon alpha (IFN-alpha) induction and other cytokine induction. At least part of the cytokine induction is mediated through NF-kappaB activation. These cytokines stimulate several other aspects of the innate immune response. In addition, imiquimod stimulates acquired immunity, in particular the cellular arm which is important for control of viral infections and various tumors. This effect is mediated by drug induced IFN-alpha and Interleukin-12 (IL-12) and IFN-gamma induced by these cytokines. Imiquimod is expected to be effective where exogenous IFN-alpha has shown utility and where enhancement of cell-mediated immunity is needed. The following is a brief review of the preclinical pharmacology of imiquimod and the clinical results of genital wart trials. The mechanism of action of topically applied imiquimod will likely lead to benefits in several other chronic virus infections and tumors of the skin. Two other reviews on imiquimod that focus mainly on the clinical results have been published (Beutner & Geisse, 1997; Slade, Owens, Tomai & Miller, 1998).

Interferon induction in turkeys by oral administration of the imidazoquinolinamine S-28828 and modulation of the pathogenesis of Escherichia coli

A synthetic imidazoquinolinamine, S-28828, has been shown to be an effective antiviral and antitumor agent in mammals. This immune modifier induces a number of cytokines such as interferons, tumor necrosis factor-alpha, interleukins and granulocyte-macrophage colony-stimulating factors in mammals. We showed that when turkeys were given S-28828 orally, high serum titers of IFN were induced in a dose-dependent manner. Turkeys, once stimulated by S-28828, became refractory to IFN production by repeated stimulation. S-28828 induced spleen, bone marrow and peripheral leukocytes to produce IFN in vitro. Splenic adherent cells were the main producers of IFN after in vitro stimulation. S-28828-induced IFN was identified as type I IFN that was pH-resistant but heat-labile. We examined the effect of a high dose (100 mg kg(-1) body weight) of S-28828 on the pathogenesis of E. coli in turkeys. Treatment with S-28828 increased mortality in infected birds and impaired E. coli clearance from the liver. The enhancement of the pathogenicity of E. coli by S-28828 may have been due to the massive release of cytokines inducing a shock-like syndrome in infected turkeys.

Topical microbicides. Current status and research considerations for adolescent girls

BACKGROUND AND OBJECTIVES

For sexually active adolescent girls, sexually transmitted diseases (STDs) represent a significant health problem. Although condom use may be an effective intervention against STDs in this high-risk population, actual use depends on the cooperation of the male partner. Therefore, the development of female-controlled methods such as topical microbicides have been endorsed as an important option for STD prevention.

GOALS

This article reviews the current status of intravaginal microbicide development and discusses aspects of adolescent development that should be considered in topical microbicide research.

RESULTS

Biological development, cognitive capacities, psychosexual maturation, and the sociocultural context are key features that affect the likelihood that adolescents will adopt microbicides as a specific methods of STD protection.

CONCLUSION

Adoption of topical microbicides by adolescents will require an "adolescent friendly" perspective for topical microbicides to have a significant impact on the STD epidemic.

In vivo and In vitro interferon induction in chickens by S -28828, an imidazoquinolinamine immunoenhancer

Imiquimod and its analogs belonging to a class of imidazoquinolinamines, activate immune system via cytokine induction, and have antitumor and antiviral effects in mammals. In this study, we showed that a related analog, designated S-28828, induced interferon (IFN) and macrophage activating cytokine(s) (macrophage activating factor, MAF) in chickens in vivo, ex vivo, and in vitro. IFN and MAF were detectable in the serum of chickens following oral administration. Serum IFN levels were the highest at 2 h after treatment. Although there was no detectable IFN in sera of chickens at 8, 24, and 48 h after treatment, high levels of interferon inducible enzyme, 2'-5' oligoadenylate synthase (2'5'OAS) were present at these time points. In vitro and ex vivo studies showed that spleen cells, bone marrow (BM) cells, and peripheral blood leukocytes (PBL) were capable of producing IFN and MAF, although spleen cells produced the highest levels. Our results suggest that S-28828 administered orally may be a useful immunoenhancing and antiviral agent for chickens.

Role of animal models in selecting antiviral combinations for clinical studies

Although experimental viral infections in animals have been used extensively in the development of antiviral drugs used as monotherapy, they have not been utilized widely for evaluation of combination chemotherapy. One of the major reasons for the lack of use of animal models is that for the diseases that are the main target for combination therapy, AIDS and hepatitis B and C infections, there is a lack of suitable models for these diseases. In contrast, most combination studies in animal models have been directed against herpes simplex virus infections but there are relatively few patients available who would benefit from combination therapy over single agent therapy. In between those two extremes are the cytomegalovirus infections. While there are animal models available that have been predictive of efficacy in humans and there are sufficient patients available, the use of antiviral combinations in animal models and in humans have begun only recently. At the present time there is not enough information available to establish the predictability for any of the animal models for efficacy of combinations of antiviral agents.

Antiviral agents in dermatology: current status and future prospects

The majority of current antiviral agents have become available only during the past decade. The above mentioned antiviral drugs, especially the viral-TK-specific agents have attempted to bring antiviral therapy on par with antimicrobial therapy. The fact, that cells infected with viruses can be selected against the relatively low toxicity to the patient, highlights the present state of antiviral therapy. Since viral infection can be viewed as an integral component of the self (i.e., a condition that cannot simply be surgically eliminated), the science of medicine is turning to the components of the self to overcome such conditions. By administering immune-system-derived agents (e.g., interferons) or compounds that stimulate the immune system (e.g., adjuvants like imiquimod), previously unmanageable conditions become manageable. The future of antiviral therapy will undoubtedly be at the molecular level. With greater understanding of the virus and the immune system with which it interacts, more specific and efficacious antiviral agents will be added to the arsenal of the clinician.

Cellular requirements for cytokine production in response to the immunomodulators imiquimod and S-27609

Imiquimod (R-837) and its analog, S-27609, belong to a class of imidazoquinolinamines that have potent antitumor and antiviral effects in animals. Much of their biologic activity is a result of the induction of cytokines, including interferon-alpha (IFN-alpha), tumor necrosis factor alpha (TNF), and others. In this study, the cells responsible for S-27609- and imiquimod-induced cytokine production were characterized. E rosette+ T cells were not the major cell population responsible for IFN-alpha and TNF in response to S-27609 or imiquimod. In contrast, E rosette- cells and unseparated PBMC produced similar concentrations of IFN-alpha and TNF in response to S-27609 and imiquimod. Elimination of monocytes by treatment with the lysosomotropic agent L-leucine methyl ester (LME) or depletion using antibody to CD14 and immunomagnetic beads abrogated IFN-alpha and TNF production induced by S-27609, imiquimod, or LPS but not poly(I)/(C). LME treatment also abolished interleukin (IL)-1 alpha, IL-beta, IL-6, and IL-8 production stimulated by S-27609 and imiquimod. Removal of HLA-DR+ or CD36+ monocytes also caused a significant reduction in S-27609- and imiquimod-induced IFN-alpha and TNF. Elimination of B cells, NK cells, and dendritic cells did not significantly reduce cytokine induction in response to S-27609. Thus, the cell population responsible for the majority of cytokine release in human PBMC in response to S-27609 and imiquimod is a E rosette-, CD14+, CD36+, HLA-DR+ monocyte.

Effect of imiquimod as an adjuvant for immunotherapy of genital HSV in guinea-pigs

Imiquimod, an immunomodulator which upregulates cell-mediated immune responses, was evaluated as an adjuvant for immunotherapy of recurrent genital herpes simplex virus (HSV) infection in guinea-pigs. In two experiments at separate research centres, animals were immunized with HSV glycoprotein and either placebo, 1 or 5 days of imiquimod, or complete Freund's adjuvant, 14 and 35 days after genital HSV-2 infection. Recurrent lesion days were then evaluated from days 15-91. In both experiments, immunization with glycoprotein and imiquimod most effectively reduced recurrence compared with unimmunized controls (53-69%, p < 0.001-0.05). A peak reduction of 70-80% was observed following the second immunization. This reduction was greater than that provided by immunization with glycoprotein and complete Freund's adjuvant in these experiments or those previously reported.