Topical resiquimod 0.01% gel decreases herpes simplex virus type 2 genital shedding: a randomized, controlled trial

Endogenous Retroviruses Provide Protection Against Vaginal HSV-2 Disease

Endogenous retroviruses (ERVs) are genomic sequences that originated from retroviruses and are present in most eukaryotic genomes. Both beneficial and detrimental functions are attributed to ERVs, but whether ERVs contribute to antiviral immunity is not well understood. Here, we used herpes simplex virus type 2 (HSV-2) infection as a model and found that Toll-like receptor 7 (Tlr7 ^-/-) deficient mice that have high systemic levels of infectious ERVs are protected from intravaginal HSV-2 infection and disease, compared to wildtype C57BL/6 mice. We deleted the endogenous ecotropic murine leukemia virus (Emv2) locus on the Tlr7 ^-/- background (Emv2 ^-/- Tlr7 ^-/-) and found that Emv2 ^-/- Tlr7 ^-/- mice lose protection against HSV-2 infection. Intravaginal application of purified ERVs from Tlr7^-/- mice prior to HSV-2 infection delays disease in both wildtype and highly susceptible interferon-alpha receptor-deficient (Ifnar1^{- /-}) mice. However, intravaginal ERV treatment did not protect Emv2^-/-Tlr7^-/- mice from HSV-2 disease, suggesting that the protective mechanism mediated by exogenous ERV treatment may differ from that of constitutively and systemically expressed ERVs in Tlr7^-/- mice. We did not observe enhanced type I interferon (IFN-I) signaling in the vaginal tissues from Tlr7-/- mice, and instead found enrichment in genes associated with extracellular matrix organization. Together, our results revealed that constitutive and/or systemic expression of ERVs protect mice against vaginal HSV-2 infection and delay disease.

Crosstalk between R848 and abortive HIV-1 RNA-induced signaling enhances antiviral immunity

Pathogens trigger multiple pattern recognition receptors (PRRs) that together dictate innate and adaptive immune responses. Understanding the crosstalk between PRRs is important to enhance vaccine efficacy. Abortive HIV-1 RNA transcripts are produced during acute and chronic HIV-1 infection and are known ligands for different PRRs, leading to antiviral and proinflammatory responses. Here, we have investigated the crosstalk between responses induced by these 58 nucleotide-long HIV-1 RNA transcripts and different TLR ligands. Costimulation of dendritic cells (DCs) with abortive HIV-1 RNA and TLR7/8 agonist R848, but not other TLR agonists, resulted in enhanced antiviral type I IFN responses as well as adaptive immune responses via the induction of DC-mediated T helper 1 (T_H 1) responses and IFNγ⁺ CD8⁺ T cells. Our data underscore the importance of crosstalk between abortive HIV-1 RNA and R848-induced signaling for the induction of effective antiviral immunity.

Anti-Viral Pattern Recognition Receptors as Therapeutic Targets

Pattern recognition receptors (PRRs) play a central role in the inflammation that ensues following microbial infection by their recognition of molecular patterns present in invading microorganisms but also following tissue damage by recognising molecules released during disease states. Such receptors are expressed in a variety of cells and in various compartments of these cells. PRR binding of molecular patterns results in an intracellular signalling cascade and the eventual activation of transcription factors and the release of cytokines, chemokines, and vasoactive molecules. PRRs and their accessory molecules are subject to tight regulation in these cells so as to not overreact or react in unnecessary circumstances. They are also key to reacting to infection and in stimulating the immune system when needed. Therefore, targeting PRRs offers a potential therapeutic approach for chronic inflammatory disease, infections and as vaccine adjuvants. In this review, the current knowledge on anti-viral PRRs and their signalling pathways is reviewed. Finally, compounds that target PRRs and that have been tested in clinical trials for chronic infections and as adjuvants in vaccine trials are discussed.

Structural evolution of toll-like receptor 7/8 agonists from imidazoquinolines to imidazoles

Several synthetic heterocyclic small molecules like imiquimod, resiquimod, CL097, CL075, bromopirone, tilorone, loxoribine and isatoribine demonstrated TLR7/8 agonistic activity and relatively modest structural changes in such molecules result in major variation in the TLR7 and/or TLR8 activity. A strict dependency of the electronic configuration of the heterocyclic system was also observed to influence the agonistic activity. In the present review, an evolution of imidazole based TLR7/8 agonist from imidazoquinoline based scaffold is delineated along with the elaboration of detailed structure activity relationship (SAR) in each chemotype. The structural and activity details of not only the active compounds but also the related inactive compounds are included to better understand the SAR. TLR7/8 agonists are emerging as promising vaccine adjuvant candidates and the present SAR and structural information will provide a road map towards the identification of more potent and appropriate candidates for further drug discovery.

Trial Watch: Experimental Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) are prototypic pattern recognition receptors (PRRs) best known for their ability to activate the innate immune system in response to conserved microbial components such as lipopolysaccharide and double-stranded RNA. Accumulating evidence indicates that the function of TLRs is not restricted to the elicitation of innate immune responses against invading pathogens. TLRs have indeed been shown to participate in tissue repair and injury-induced regeneration as well as in adaptive immune responses against cancer. In particular, TLR4 signaling appears to be required for the efficient processing and cross-presentation of cell-associated tumor antigens by dendritic cells, which de facto underlie optimal therapeutic responses to some anticancer drugs. Thus, TLRs constitute prominent therapeutic targets for the activation/intensification of anticancer immune responses. In line with this notion, long-used preparations such as the Coley toxin (a mixture of killed Streptococcus pyogenes and Serratia marcescens bacteria) and the bacillus Calmette-Guérin (BCG, an attenuated strain of Mycobacterium bovis originally developed as a vaccine against tuberculosis), both of which have been associated with consistent anticancer responses, potently activate TLR2 and TLR4 signaling. Today, besides BCG, only one TLR agonist is FDA-approved for therapeutic use in cancer patients: imiquimod. In this Trial Watch, we will briefly present the role of TLRs in innate and cognate immunity and discuss the progress of clinical studies evaluating the safety and efficacy of experimental TLR agonists as immunostimulatory agents for oncological indications.

The Restrictome of Flaviviruses

Flaviviruses are a genus of mostly arthropod-borne RNA viruses that cause a range of pathologies in humans. Basic knowledge on flaviviruses is rapidly expanding, partly due to their status as frequent emerging or re-emerging pathogens. Flaviviruses include the dengue, Zika, West Nile, tick-borne encephalitis and yellow fever viruses (DENV, ZIKV, WNV, TBEV and YFV, respectively). As is the case with other families of viruses, the success of productive infection of human cells by flaviviruses depends in part on the antiviral activity of a heterogeneous group of cellular antiviral proteins called restriction factors. Restriction factors are the effector proteins of the cell-autonomous innate response against viruses, an immune pathway that also includes virus sensors as well as intracellular and extracellular signal mediators such as type I interferons (IFN-I). In this review, I summarize recent progress toward the identification and characterization of flavivirus restriction factors. In particular, I focus on IFI6, Schlafen 11, FMRP, OAS-RNase L, RyDEN, members of the TRIM family of proteins (TRIM5α, TRIM19, TRIM56, TRIM69 and TRIM79α) and a new mechanism of action proposed for viperin. Recent and future studies on this topic will lead to a more complete picture of the flavivirus restrictome, defined as the ensemble of cellular factors with demonstrated anti-flaviviral activity.

The global and regional burden of genital ulcer disease due to herpes simplex virus: a natural history modelling study

Introduction

Herpes simplex virus (HSV) infection can cause painful, recurrent genital ulcer disease (GUD), which can have a substantial impact on sexual and reproductive health. HSV-related GUD is most often due to HSV type 2 (HSV-2), but may also be due to genital HSV type 1 (HSV-1), which has less frequent recurrent episodes than HSV-2. The global burden of GUD has never been quantified. Here we present the first global and regional estimates of GUD due to HSV-1 and HSV-2 among women and men aged 15-49 years old.

Methods

We developed a natural history model reflecting the clinical course of GUD following HSV-2 and genital HSV-1 infection, informed by a literature search for data on model parameters. We considered both diagnosed and undiagnosed symptomatic infection. This model was then applied to existing infection estimates and population sizes for 2016. A sensitivity analysis was carried out varying the assumptions made.

Results

We estimated that 187 million people aged 15-49 years had at least one episode of HSV-related GUD globally in 2016: 5.0% of the world's population. Of these, 178 million (95% of those with HSV-related GUD) had HSV-2 compared with 9 million (5%) with HSV-1. GUD burden was highest in Africa, and approximately double in women compared with men. Altogether there were an estimated 8 billion person-days spent with HSV-related GUD globally in 2016, with 99% of days due to HSV-2. Taking into account parameter uncertainty, the percentage with at least one episode of HSV-related GUD ranged from 3.2% to 7.9% (120-296 million). However, the estimates were sensitive to the model assumptions.

Conclusion

Our study represents a first attempt to quantify the global burden of HSV-related GUD, which is large. New interventions such as HSV vaccines, antivirals or microbicides have the potential to improve the quality of life of millions of people worldwide.

Pharmacological modulation of nucleic acid sensors - therapeutic potential and persisting obstacles

Nucleic acid sensors, primarily TLR and RLR family members, as well as cGAS-STING signalling, play a critical role in the preservation of cellular and organismal homeostasis. Accordingly, deregulated nucleic acid sensing contributes to the origin of a diverse range of disorders, including infectious diseases, as well as cardiovascular, autoimmune and neoplastic conditions. Accumulating evidence indicates that normalizing aberrant nucleic acid sensing can mediate robust therapeutic effects. However, targeting nucleic acid sensors with pharmacological agents, such as STING agonists, presents multiple obstacles, including drug-, target-, disease- and host-related issues. Here, we discuss preclinical and clinical data supporting the potential of this therapeutic paradigm and highlight key limitations and possible strategies to overcome them.

Toll-like receptor agonist R848 blocks Zika virus replication by inducing the antiviral protein viperin

Zika virus (ZIKV) is an emerging pathogen linked to neurological disorders for which there is currently no targeted therapy. To identify host innate immune response proteins that restrict ZIKV replication, we treated monocytes and macrophages with toll-like receptor (TLR) agonists. Of those tested, the TLR7/8 agonist R848 (resiquimod) was the most potent inhibitor of ZIKV replication. RNA-seq analysis identified several genes strongly induced by R848 in monocytes. Testing of several of these for their ability to restrict ZIKV replication identified viperin, an interferon-induced gene active against several viruses. Transduction of microglial CHME3 cells with a viperin lentiviral expression vector rendered them resistant to ZIKV infection, preventing the synthesis of viral RNA and protein. CRISPR/Cas9 knock-out of viperin in macrophages relieved the block to infection, demonstrating that viperin is a major innate immune response protein able to block ZIKV replication. TLR agonists may be useful for the prophylactic or therapeutic treatment for ZIKV.

TLR7/8 agonist induces a post-entry SAMHD1-independent block to HIV-1 infection of monocytes

Background

Monocytes, the primary myeloid cell-type in peripheral blood, are resistant to HIV-1 infection as a result of the lentiviral restriction factor SAMHD1. Toll-like receptors recognize microbial pathogen components, inducing the expression of antiviral host proteins and proinflammatory cytokines. TLR agonists that mimic microbial ligands have been found to have activity against HIV-1 in macrophages. The induction of restriction factors in monocytes by TLR agonist activation has not been well studied. To analyze restriction factor induction by TLR activation in monocytes, we used the imidazoquinoline TLR7/8 agonist R848 and infected with HIV-1 reporter virus that contained packaged viral accessory protein Vpx, which allows the virus to escape SAMHD1-mediated restriction. 

Results

R848 prevented the replication of Vpx-containing HIV-1 and HIV-2 in peripheral blood mononuclear cells and monocytes. The block was post-entry but prior to reverse transcription of the viral genomic RNA. The restriction was associated with destabilization of the genomic RNA molecules of the in-coming virus particle. R848 treatment of activated T cells did not protect them from infection but treated monocytes produced high levels of proinflammatory cytokines, including type-I IFN that protected bystander activated T cells from infection.

Conclusion

The activation of TLR7/8 induces two independent restrictions to HIV-1 replication in monocytes: a cell-intrinsic block that acts post-entry to prevent reverse transcription; and a cell-extrinsic block, in which monocytes produce high levels of proinflammatory cytokines (primarily type-I IFN) that protects bystander monocytes and T lymphocytes. The cell-intrinsic block may result from the induction of a novel restriction factor, which can be termed Lv5 and acts by destabilizing the in-coming viral genomic RNA, either by the induction of a host ribonuclease or by disrupting the viral capsid. TLR agonists are being developed for therapeutic use to diminish the size of the latent provirus reservoir in HIV-1 infected individuals. Such drugs may both induce latent provirus expression and restrict virus replication during treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0316-3) contains supplementary material, which is available to authorized users.

Interventions for men and women with their first episode of genital herpes

BACKGROUND

Genital herpes is incurable, and is caused by the herpes simplex virus (HSV). First-episode genital herpes is the first clinical presentation of herpes that a person experiences. Current treatment is based around viral suppression in order to decrease the length and severity of the episode.

OBJECTIVES

To determine the effectiveness and safety of the different existing treatments for first-episode genital herpes on the duration of symptoms and time to recurrence.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (from inception to April 2016), MEDLINE (from inception to April 2016), the Specialised Register of the Cochrane Sexually Transmitted Infections Review Group (from inception to April 2016), EMBASE (from inception to April 2016), PsycINFO (from inception to April 2016), CINAHL (from inception to April 2016), LILACS (from inception to April 2016), AMED (from inception to April 2016), and the Alternative Medicines Specialised Register (from inception to April 2016). We handsearched a number of relevant journals, searched reference lists of all included studies, databases of ongoing trials, and other Internet databases.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) on participants with first-episode genital herpes. We excluded vaccination trials, and trials in which the primary objective assessed a complication of HSV infection.

DATA COLLECTION AND ANALYSIS

All studies written in English were independently assessed by at least two review authors for inclusion, risk of bias for each trial, and to extract data. Studies requiring translation were assessed for inclusion, trial quality, and data extraction by external translators.

MAIN RESULTS

We included 26 trials with 2084 participants analysed. Most of the studies were conducted in the United Kingdom (UK) and United States (US), and involved men and women experiencing their first episode of genital herpes, with the exception of three studies which included only women. We rated the majority of these studies as having an unclear risk of bias; largely due to lack of information supplied in the publications, and due to the age of the trials. This review found low quality evidence from two studies of oral acyclovir, when compared to placebo, reduced the duration of symptoms in individuals undergoing their first episode of genital herpes (mean difference (MD) -3.22, 95% confidence interval (CI) -5.91 to -0.54; I(2) = 52%). In two studies (112 participants), intravenous acyclovir decreased the median number of days that patients with first-episode herpes suffered symptoms. Oral valaciclovir (converted to acyclovir) also showed a similar length of symptom duration when compared to acyclovir in two studies.There is currently no evidence that topical acyclovir reduces symptoms (MD -0.61 days, 95% CI -2.16 to 0.95; 3 RCTs, 195 participants, I(2) statistic = 56%). There is also no current evidence that the topical treatments of cicloxolone cream, carbenoxolone sodium cream, adenosine arabinoside, idoxuridine in dimethyl sulfoxide, when compared to placebo reduced the duration of symptoms in people undergoing their first episode of herpes.Two studies reported no evidence of a reduction in the number of median days to recurrence following treatment with oral acyclovir versus placebo. Adverse events were generally poorly reported by all of the included studies and we were unable to quantitatively analyse this outcome. For those taking acyclovir, there were no serious adverse events; the most common adverse events reported for oral acyclovir were coryza, dizziness, tiredness, diarrhoea and renal colic. For intravenous acyclovir these were phlebitis, nausea and abnormal liver function tests and for topical acyclovir there was pain with the topical application.Those undergoing interferon treatment had significantly more adverse events compared to those taking placebo.

AUTHORS' CONCLUSIONS

There is low quality evidence from this review that oral acyclovir reduced the duration of symptoms for genital herpes. However, there is low quality evidence which did not show that topical antivirals reduced symptom duration for patients undergoing their first episode of genital herpes. This review was limited by the inclusion of skewed data, resulting in few trials that we were able to meta-analyse.

Degradation of acetalated dextran can be broadly tuned based on cyclic acetal coverage and molecular weight

Microparticles (MPs) derived from acid-sensitive biopolymers enable rapid degradation and cargo release under acidic conditions, such as at tumor microenvironments, within lysosomal/phagosomal compartments inside phagocytic cells, or at sites of inflammation. One such acid-sensitive biopolymer, acetalated dextran (Ace-DEX), has tunable degradation rates and pH-neutral degradation byproducts consisting of dextran, acetone, and ethanol. By studying the degradation profiles of Ace-DEX MPs with varying cyclic acetal coverage (CAC) and dextran molecular weight (MW), we concluded that MPs composed of low CAC or high MW polymer degraded the fastest at both pH 7.4 and 5.0. To further understand the properties of this unique polymer, we encapsulated a model drug resiquimod, which is a toll-like receptor (TLR) 7/8 agonist, into Ace-DEX MPs of different polymer CAC and dextran MW. It was observed that resiquimod was released faster from MPs of lower CAC or higher MW. By evaluating the activation of RAW macrophages cultured with different types of resiquimod-loaded Ace-DEX MPs, we found that MPs of lower CAC or higher MW promoted greater nitrite production and resulted in more robust cell activation. Our results indicate we can precisely control the degradation profile, release kinetics, and bioactivity of encapsulated cargos by altering CAC and MW, furthering Ace-DEX MPs' novelty as a drug carrier.

Evaluation of novel synthetic TLR7/8 agonists as vaccine adjuvants

Small-molecule adjuvants that boost and direct adaptive immunity provide a powerful means to increase the effectiveness of vaccines. Through rational design several novel imidazoquinoline and oxoadenine TLR7/8 agonists, each with unique molecular modifications, were synthesized and assessed for their ability to augment adaptive immunity. All agonists bound human TLR7 and TLR8 and induced maturation of both human mDCs and pDCs. All agonists prompted production of type I interferon and/or proinflammatory cytokines, albeit with varying potencies. In most in vitro assays, the oxoadenine class of agonists proved more potent than the imidazoquinolines. Therefore, an optimized oxoadenine TLR7/8 agonist that demonstrated maximal activity in the in vitro assays was further assessed in a vaccine study with the CRM197 antigen in a porcine model. Antigen-specific antibody production was greatly enhanced in a dose dependent manner, with antibody titers increased 800-fold compared to titers from pigs vaccinated with the non-adjuvanted vaccine. Moreover, pigs vaccinated with antigen containing the highest dose of adjuvant promoted a 13-fold increase in the percentage of antigen-specific CD3(+)/CD8(+) T cells over pigs vaccinated with antigen alone. Together this work demonstrates the promise of these novel TLR7/8 agonists as effective human vaccine adjuvants.

Adjuvants: Classification, Modus Operandi, and Licensing

Vaccination is one of the most efficient strategies for the prevention of infectious diseases. Although safer, subunit vaccines are poorly immunogenic and for this reason the use of adjuvants is strongly recommended. Since their discovery in the beginning of the 20th century, adjuvants have been used to improve immune responses that ultimately lead to protection against disease. The choice of the adjuvant is of utmost importance as it can stimulate protective immunity. Their mechanisms of action have now been revealed. Our increasing understanding of the immune system, and of correlates of protection, is helping in the development of new vaccine formulations for global infections. Nevertheless, few adjuvants are licensed for human vaccines and several formulations are now being evaluated in clinical trials. In this review, we briefly describe the most well known adjuvants used in experimental and clinical settings based on their main mechanisms of action and also highlight the requirements for licensing new vaccine formulations.

Nonsteroidal Topical Immunomodulators in Allergology and Dermatology

The purpose of this study was to review currently available literature data concerning pathomechanisms of action, indications, treatment efficacy, as well as side effects of nonsteroidal immunomodulators used in dermatology, primarily for the treatment of allergic dermatoses. MEDLINE search was undertaken using the key words “Topical Immunomodulators, Dermatology and Allergy”. Full articles, and nothing but full articles, were used.

Genital Herpes Simplex Virus Type 2 Shedding Among Adults With and Without HIV Infection in Uganda

BACKGROUND

Despite the high prevalence of herpes simplex virus type 2 (HSV-2) in sub-Saharan Africa, the natural history of infection among Africans is not well characterized. We evaluated the frequency of genital HSV shedding in HIV-seropositive and HIV-seronegative men and women in Uganda.

METHODS

Ninety-three HSV-2-seropositive Ugandan adults collected anogenital swab specimens for HSV DNA quantification by polymerase chain reaction 3 times daily for 6 weeks.

RESULTS

HSV-2 was detected from 2484 of 11 283 swab specimens collected (22%), with a median quantity of 4.3 log10 HSV copies/mL (range, 2.2-8.9 log10 HSV copies/mL). Genital lesions were reported on 749 of 3875 days (19%), and subclinical HSV shedding was detected from 1480 of 9113 swab specimens (16%) collected on days without lesions. Men had higher rates of total HSV shedding (relative risk [RR], 2.0 [95% confidence interval {CI}, 1.3-2.9]; P < .001); subclinical shedding (RR, 1.7 [95% CI, 1.1-2.7]; P = .01), and genital lesions (RR, 2.1 [95% CI, 1.2-3.4]; P = .005), compared with women. No differences in shedding rates or lesion frequency were observed based on HIV serostatus.

CONCLUSIONS

HSV-2 shedding frequency and quantity are high among HSV-2-seropositive adults in sub-Saharan Africa, including persons with and those without HIV infection. Shedding rates were particularly high among men, which may contribute to the high prevalence of HSV-2 and early acquisition among African women.

Trial Watch: Peptide-based anticancer vaccines

Malignant cells express antigens that can be harnessed to elicit anticancer immune responses. One approach to achieve such goal consists in the administration of tumor-associated antigens (TAAs) or peptides thereof as recombinant proteins in the presence of adequate adjuvants. Throughout the past decade, peptide vaccines have been shown to mediate antineoplastic effects in various murine tumor models, especially when administered in the context of potent immunostimulatory regimens. In spite of multiple limitations, first of all the fact that anticancer vaccines are often employed as therapeutic (rather than prophylactic) agents, this immunotherapeutic paradigm has been intensively investigated in clinical scenarios, with promising results. Currently, both experimentalists and clinicians are focusing their efforts on the identification of so-called tumor rejection antigens, i.e., TAAs that can elicit an immune response leading to disease eradication, as well as to combinatorial immunostimulatory interventions with superior adjuvant activity in patients. Here, we summarize the latest advances in the development of peptide vaccines for cancer therapy.

Trial Watch: Toll-like receptor agonists in oncological indications

Toll-like receptors (TLRs) are an evolutionarily conserved group of enzymatically inactive, single membrane-spanning proteins that recognize a wide panel of exogenous and endogenous danger signals. Besides constituting a crucial component of the innate immune response to bacterial and viral pathogens, TLRs appear to play a major role in anticancer immunosurveillance. In line with this notion, several natural and synthetic TLR ligands have been intensively investigated for their ability to boost tumor-targeting immune responses elicited by a variety of immunotherapeutic and chemotherapeutic interventions. Three of these agents are currently approved by the US Food and Drug Administration (FDA) or equivalent regulatory agencies for use in cancer patients: the so-called bacillus Calmette-Guérin, monophosphoryl lipid A, and imiquimod. However, the number of clinical trials testing the therapeutic potential of both FDA-approved and experimental TLR agonists in cancer patients is stably decreasing, suggesting that drug developers and oncologists are refocusing their interest on alternative immunostimulatory agents. Here, we summarize recent findings on the use of TLR agonists in cancer patients and discuss how the clinical evaluation of FDA-approved and experimental TLR ligands has evolved since the publication of our first Trial Watch dealing with this topic.

Immunogenicity of intradermal trivalent influenza vaccine with topical imiquimod: a double blind randomized controlled trial

BACKGROUND

Imiquimod, a synthetic Toll-like receptor 7 agonist enhanced immunogenicity of influenza vaccine in a mouse model. We hypothesized that topical imiquimod before intradermal influenza vaccination (TIV) would produce similar effect in human.

METHODS

We performed a prospective 1-year follow-up, double-blind, randomized, controlled trial with adults with comorbidities. Participants were randomized to 1 of the following 3 vaccinations: topical 5% 250 mg imiquimod ointment followed by intradermal TIV, topical aqueous-cream followed by intradermal TIV, or topical aqueous-cream followed by intramuscular TIV. Patients and investigators were blinded to the type of topical treatment applied. Hemagglutination inhibition (HI) and microneutralization antibody titers were measured. The primary outcome was the day 7 seroconversion rate.

RESULTS

Ninety-one recruited participants completed the study. The median age was 73 years. On day 7, 27/30 (90%) patients who received imiquimod and intradermal TIV achieved seroconversion against the H1N1 strain by HI, compared with 4/30 (13.3%) who received aqueous-cream and intramuscular TIV (P < .001), and 12/31 (38.7%) who received aqueous-cream and intradermal TIV (P < .001). The seroconversion, seroprotection, and geometric mean titer-fold increase were met in all 3 strains in the imiquimod and intradermal TIV group 2 weeks earlier, and the better seroconversion rate was sustained from day 7 to year 1 (P ≤ .001). The better immunogenicity was associated with fewer hospitalizations for influenza or pneumonia (P < .05). All adverse reactions were self-limited.

CONCLUSIONS

Pretreatment with topical imiquimod significantly expedited, augmented, and prolonged the immunogenicity of influenza vaccination. This strategy for influenza immunization should be considered for the elderly population.

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(®).

Three phase III randomized controlled trials of topical resiquimod 0.01-percent gel to reduce anogenital herpes recurrences

Resiquimod, a Toll-like receptor 7 and 8 agonist, stimulates production of cytokines that promote an antigen-specific T helper type 1 acquired immune response. Animal and phase II human trials showed posttreatment efficacy in reducing recurrent herpes lesion days and/or time to first recurrence. Three phase III randomized, double-blind, vehicle-controlled trials of topical resiquimod to reduce anogenital herpes recurrences were conducted in healthy adults with ≥4 recurrences within the prior year. Participants applied resiquimod 0.01% gel or vehicle gel 2 times per week for 3 weeks to each recurrence for 12 months. Trials 1 and 2 had 2:1 resiquimod-vehicle randomization. Trial 3 had 1:1:1 randomization for resiquimod and 500 mg valacyclovir orally twice daily for 5 days (RESI-VAL), resiquimod and oral placebo (RESI-PLA), and vehicle and oral placebo (VEH-PLA). The median time to first recurrence was similar for resiquimod and vehicle (trial 1, 60 and 56 days, P=0.7; trial 2, 54 and 48 days, P=0.47; trial 3, 51 [RESI-VAL], 55 [RESI-PLA], and 44 [VEH-PLA] days, P=not significant [NS]). The median time to healing of initial treated recurrence was longer for resiquimod (trial 1, 18 compared to 10 days, P<0.001; trial 2, 19 compared to 13 days, P=0.16; trial 3, 14 [RESI-VAL], 16 [RESI-PLA], and 8 [VEH-PLA] days, P<0.001). In trials 1 and 2, moderate to severe erythema and erosion/ulceration at the application site were more common in resiquimod recipients. In conclusion, no posttreatment efficacy of resiquimod 0.01% gel was observed. Increased application site reactions and initial recurrence healing time are consistent with resiquimod-induced cytokine effects.

Adjuvant-carrying synthetic vaccine particles augment the immune response to encapsulated antigen and exhibit strong local immune activation without inducing systemic cytokine release

Augmentation of immunogenicity can be achieved by particulate delivery of an antigen and by its co-administration with an adjuvant. However, many adjuvants initiate strong systemic inflammatory reactions in vivo, leading to potential adverse events and safety concerns. We have developed a synthetic vaccine particle (SVP) technology that enables co-encapsulation of antigen with potent adjuvants. We demonstrate that co-delivery of an antigen with a TLR7/8 or TLR9 agonist in synthetic polymer nanoparticles results in a strong augmentation of humoral and cellular immune responses with minimal systemic production of inflammatory cytokines. In contrast, antigen encapsulated into nanoparticles and admixed with free TLR7/8 agonist leads to lower immunogenicity and rapid induction of high levels of inflammatory cytokines in the serum (e.g., TNF-α and IL-6 levels are 50- to 200-fold higher upon injection of free resiquimod (R848) than of nanoparticle-encapsulated R848). Conversely, local immune stimulation as evidenced by cellular infiltration of draining lymph nodes and by intranodal cytokine production was more pronounced and persisted longer when SVP-encapsulated TLR agonists were used. The strong local immune activation achieved using a modular self-assembling nanoparticle platform markedly enhanced immunogenicity and was equally effective whether antigen and adjuvant were co-encapsulated in a single nanoparticle formulation or co-delivered in two separate nanoparticles. Moreover, particle encapsulation enabled the utilization of CpG oligonucleotides with the natural phosphodiester backbone, which are otherwise rapidly hydrolyzed by nucleases in vivo. The use of SVP may enable clinical use of potent TLR agonists as vaccine adjuvants for indications where cellular immunity or robust humoral responses are required.

Structure and function of toll-like receptor 8

Toll-like receptors (TLRs) sense pathogen-associated molecular patterns originating from invading microorganisms and initiate innate immune responses. Recent structural studies of TLR-ligand complexes have revealed the detailed molecular mechanisms by which each TLR specifically recognizes its own ligands. This review focuses on the structure of TLR8 and discusses the similarities and diversities of TLR-ligand interactions and signaling mechanisms.

Targeting toll-like receptors: promising therapeutic strategies for the management of sepsis-associated pathology and infectious diseases

Toll-like receptors (TLRs) are pattern recognition receptors playing a fundamental role in sensing microbial invasion and initiating innate and adaptive immune responses. TLRs are also triggered by danger signals released by injured or stressed cells during sepsis. Here we focus on studies developing TLR agonists and antagonists for the treatment of infectious diseases and sepsis. Positioned at the cell surface, TLR4 is essential for sensing lipopolysaccharide of Gram-negative bacteria, TLR2 is involved in the recognition of a large panel of microbial ligands, while TLR5 recognizes flagellin. Endosomal TLR3, TLR7, TLR8, TLR9 are specialized in the sensing of nucleic acids produced notably during viral infections. TLR4 and TLR2 are favorite targets for developing anti-sepsis drugs, and antagonistic compounds have shown efficient protection from septic shock in pre-clinical models. Results from clinical trials evaluating anti-TLR4 and anti-TLR2 approaches are presented, discussing the challenges of study design in sepsis and future exploitation of these agents in infectious diseases. We also report results from studies suggesting that the TLR5 agonist flagellin may protect from infections of the gastrointestinal tract and that agonists of endosomal TLRs are very promising for treating chronic viral infections. Altogether, TLR-targeted therapies have a strong potential for prevention and intervention in infectious diseases, notably sepsis.

Electrospun acetalated dextran scaffolds for temporal release of therapeutics

Electrospun acetalated dextran (Ac-DEX) scaffolds were fabricated to encapsulate resiquimod, an immunomodulatory toll-like-receptor (TLR) agonist. Ac-DEX has been used to fabricate scaffolds for sustained and temporal delivery of therapeutics because it has tunable degradation rates that are dependent on its synthesis reaction time or the molecular weight of dextran. Additionally, as opposed to commonly electrospun polyesters that shift the local pH upon degradation, the degradation products of Ac-DEX are pH-neutral: dextran, an alcohol, and the metabolic byproduct acetone. Formulations of Ac-DEX with two different degradation rates were used in this study. The effects of electrospinning conditions on the scaffold size and morphology were examined as well as fibroblast adhesion as imaged with fluorescence microcopy and scanning electron microscopy. Macrophage (MΦ) viability further indicates that the scaffolds are cytocompatible. Also, the controlled release profiles of resiquimod from loaded scaffolds and nitric oxide (NO) production by MΦ incubated with these scaffolds show the potential for Ac-DEX scaffolds to be used to temporally and efficiently deliver therapeutics. Overall, we present a novel scaffold that can have tunable and unique drug release rates for tissue engineering, drug delivery, immunomodulation, and wound healing applications.

Rapid host immune response and viral dynamics in herpes simplex virus-2 infection

Herpes simplex virus-2 (HSV-2) is periodically shed throughout the human genital tract. Although a high viral load correlates with the development of genital ulcers, shedding also commonly occurs even when ulcers are absent, allowing for silent transmission during coitus and contributing to high seroprevalence of HSV-2 worldwide. Frequent viral reactivation occurs within ganglia despite diverse and complementary host and viral mechanisms that predispose toward latency, suggesting that viral replication may be constantly occurring in a small minority of neurons at these sites. Within genital mucosa, the in vivo expansion and clearance rates of HSV-2 are extremely rapid. Resident dendritic cells and memory HSV-2 specific T cells persist at prior sites of genital tract reactivation and, in conjunction with prompt innate recognition of infected cells, lead to rapid containment of infected cells. The fact that immune responses usually control viral replication in genital skin before lesions develop provides hope that enhancing such responses could lead to effective vaccines and immunotherapies.

Learning from the messengers: innate sensing of viruses and cytokine regulation of immunity - clues for treatments and vaccines

Virus infections are a major global public health concern, and only via substantial knowledge of virus pathogenesis and antiviral immune responses can we develop and improve medical treatments, and preventive and therapeutic vaccines. Innate immunity and the shaping of efficient early immune responses are essential for control of viral infections. In order to trigger an efficient antiviral defense, the host senses the invading microbe via pattern recognition receptors (PRRs), recognizing distinct conserved pathogen-associated molecular patterns (PAMPs). The innate sensing of the invading virus results in intracellular signal transduction and subsequent production of interferons (IFNs) and proinflammatory cytokines. Cytokines, including IFNs and chemokines, are vital molecules of antiviral defense regulating cell activation, differentiation of cells, and, not least, exerting direct antiviral effects. Cytokines shape and modulate the immune response and IFNs are principle antiviral mediators initiating antiviral response through induction of antiviral proteins. In the present review, I describe and discuss the current knowledge on early virus–host interactions, focusing on early recognition of virus infection and the resulting expression of type I and type III IFNs, proinflammatory cytokines, and intracellular antiviral mediators. In addition, the review elucidates how targeted stimulation of innate sensors, such as toll-like receptors (TLRs) and intracellular RNA and DNA sensors, may be used therapeutically. Moreover, I present and discuss data showing how current antimicrobial therapies, including antibiotics and antiviral medication, may interfere with, or improve, immune response.

Potent induction of antibody-secreting B cells by human dermal-derived CD14+ dendritic cells triggered by dual TLR ligation

Targeting CD14(+) dermal-derived dendritic cells (DDCs) is a rational approach for vaccination strategies aimed at improving humoral immune responses, because of their natural ability to stimulate naive B cells. In this study, we show that CD14(+) DDCs express mRNA for TLRs 1-9, but respond differentially to single or paired TLR ligands. Compared to single ligands, some combinations were particularly effective at activating CD14(+) DDCs, as shown by enhanced expression of B cell stimulatory cytokines (IL-6, IL-10, and TNF-α) and more pronounced phenotypic maturation. These combinations were resiquimod (R-848) plus polyinosinic-polycytidylic acid [Poly(I:C)], R-848 plus LPS, Pam3CSK4 plus Poly(I:C), and LPS plus Poly(I:C). We also found that selected TLR ligand pairs [R-848 plus either LPS or Poly(I:C)] were superior to individual agents at boosting the inherent capacity of CD14(+) DDCs to induce naive B cells to proliferate and differentiate into CD27(+) CD38(+) B cells that secrete high levels of IgG and IgA. When treated with the same TLR ligand combinations, CD14(+) DDCs also promoted the differentiation of Th1 (IFN-γ-secreting) CD4(+) T cells, but not of Th2 or Th17 CD4(+) T cells. These observations may help to identify adjuvant strategies aimed at inducing protective immune responses to various pathogens, including but not limited to HIV-1.

The pharmacokinetics of Toll-like receptor agonists and the impact on the immune system

Toll-like receptor (TLR) ligation activates both the innate and adaptive immune systems, and plays an important role in antiviral and anti-tumor immunity. Therefore, a significant amount of effort has been devoted to exploit the therapeutic potential of TLR agonists. Depending on the therapeutic purpose, either as adjuvants to vaccine, chemotherapy or standalone therapy, TLR agonists have been administered via different routes. Both preclinical and clinical studies have suggested that the route of administration has significant effects on pharmacokinetics, and that understanding these effects is critical to the success of TLR agonist drug development. This article will summarize the pharmacokinetics of TLR agonists with different administration routes, with an emphasis on clinical studies of TLR ligands in oncologic applications.

Peripheral blood CD4 T-cell and plasmacytoid dendritic cell (pDC) reactivity to herpes simplex virus 2 and pDC number do not correlate with the clinical or virologic severity of recurrent genital herpes

Leukocytes participate in the immune control of herpes simplex virus (HSV). Data from HIV coinfections, germ line mutations, and case reports suggest involvement of CD4 T cells and plasmacytoid dendritic cells (pDC). We investigated the relationships between these cells and recurrent genital herpes disease severity in the general population. Circulating CD4 T-cell responses to HSV-2 were measured in specimens from 67 immunocompetent individuals with measured genital lesion and HSV shedding rates. Similarly, pDC number and functional responses to HSV-2 were analyzed in 40 persons. CD4 responses and pDC concentrations and responses ranged as much as 100-fold between persons while displaying moderate within-person consistency over time. No correlations were observed between these immune response parameters and genital HSV-2 severity. Cytomegalovirus (CMV) coinfection was not correlated with differences in HSV-2-specific CD4 T-cell responses. The CD4 T-cell response to HSV-2 was much more polyfunctional than was the response to CMV. These data suggest that other immune cell subsets with alternate phenotypes or anatomical locations may be responsible for genital herpes control in chronically infected individuals.

New developments in Toll-like receptor targeted therapeutics

Toll-like receptors (TLRs) play a crucial role in host defence and inflammation. Given that a significant amount of evidence implicates TLRs in the pathogenesis of immune diseases and cancer, and their activation occurs early in the inflammatory cascade, they are attractive targets for novel therapeutic agents. Potential therapeutics include TLR-targeted antibodies, small molecules and nucleic acid based drugs. Agonists are being tested in vaccines against hepatitis C and influenza as well as in allergic rhinitis and certain cancers. Antagonists are being tested in ischemia/reperfusion injury, systemic lupus erythematosus and psoriasis. The prospect of targeting TLRs in multiple pathologies continues to hold much promise.

Pattern recognition receptors in immune disorders affecting the skin

Pattern recognition receptors (PRRs) evolved to protect organisms against pathogens, but excessive signaling can induce immune responses that are harmful to the host. Putative PRR dysfunction is associated with numerous immune disorders that affect the skin, such as systemic lupus erythematosus, cryopyrin-associated periodic syndrome, and primary inflammatory skin diseases including psoriasis and atopic dermatitis. As yet, the evidence is often confined to genetic association studies without additional proof of a causal relationship. However, insight into the role of PRRs in the pathophysiology of some disorders has already resulted in new therapeutic approaches based on immunomodulation of PRRs.

HSV-2: in pursuit of a vaccine

Herpes simplex virus type 2 (HSV-2) is one of the most prevalent sexually transmitted infections worldwide. In addition to recurrent genital ulcers, HSV-2 causes neonatal herpes, and it is associated with a 3-fold increased risk for HIV acquisition. Although many HSV-2 vaccines have been studied in animal models, few have reached clinical trials, and those that have been tested in humans were not consistently effective. Here, we review HSV-2 pathogenesis, with a focus on novel understanding of mucosal immunobiology of HSV-2, and vaccine efforts to date, in an attempt to stimulate thinking about future directions for development of effective prophylactic and therapeutic HSV-2 vaccines.

Vaccine adjuvant activity of 3M-052: an imidazoquinoline designed for local activity without systemic cytokine induction

The human Toll-like receptors (TLRs) are a family of receptors, which sense the presence of various structural elements of pathogens and damaged or effete components in the host. As they do so, they activate two critical arms of host defense, the rapid innate immune response and an adaptive immune response. The innate immune response is typified by the generation of Th1 cytokines, chemokines and type 1 interferons. As such, agonists for the TLRs have potential as antiviral and anticancer therapeutics. They are also well suited to function as vaccine adjuvants. 3M imidazoquinoline (IRM) molecules were the first synthetic small molecules identified as TLR agonists and can affect their biological activities through TLR7, TLR8, or both. The breadth of therapeutic opportunities for this family of molecules can require formulations tailored to the specific application. One consideration is specific formulations to avoid a systemic distribution of these TLR agonists and resulting cytokine storm-like effects on the host. 3M-052 is an IRM bearing a C18 lipid moiety and designed for slow dissemination from the site of application. In the present study 3M-052 has been evaluated for its in vitro TLR activity and for its efficacy as a vaccine adjuvant using a recombinant hemagglutinin from H1N1 A/Puerto Rico/8/34. Given subcutaneously, 3M-052 drives a strong Th1 response to hemagglutinin and serum neutralization of viable H1N1 A/Puerto Rico/8/34 virus in the absence of circulating TNFα or the induction of Th1 cytokines.

Sensing herpes: more than toll

To launch an effective antiviral immune response, cells must recognize the virus, activate a cytokine response, and initiate inflammatory processes. Herpes simplex virus 1 (HSV-1) and HSV-2 are nuclear-replicating viruses composed of a double-stranded DNA genome plus glycoproteins that are incorporated into a lipid bilayer envelope that surrounds an icosahedral capsid. Several novel receptors that mediate innate recognition of HSV and that activate the innate immune response have been identified in recent years. The host-virus interactions that lead to type I interferon (IFN), type III IFN, and cytokine production include cellular recognition of viral envelope and structural proteins, recognition of viral genomic DNA and recognition of virus-derived double-stranded RNAs. Such RNAs can interact with cellular pattern-recognition receptors, including Toll-like receptors and a number of cytoplasmic and nuclear receptors for virus DNA and virus-derived RNAs. In this review, I present a systematic overview of innate cellular recognition of HSV infection that leads to immune activation, and I discuss the implications of the known cell-host interactions. In addition, I discuss the use of innate stimulation to improve anti-HSV treatment and vaccine response and I discuss future research aims.

Targeting of Toll-like receptors: a decade of progress in combating infectious diseases

Toll-like receptors (TLRs) recognise highly conserved molecular structures, collectively known as pathogen-associated molecular patterns. In the past two decades, development and clinical implementation of TLR ligands-ie, chemically modified synthetic derivatives of naturally occurring ligands and fully synthetic small molecules-have been topics of intense research. Targeted manipulation of TLR signalling has been applied clinically to boost vaccine effectiveness, promote a robust T helper 1-predominant immune response against viral infection, or dampen the exaggerated inflammatory response to bacterial infection. Use of these new therapeutic molecules as adjuncts to conventional pharmacotherapy or stand-alone treatments might offer solutions to unmet clinical needs or could replace existing partly effective therapeutic strategies.

Persistent genital herpes simplex virus-2 shedding years following the first clinical episode

BACKGROUND

Patients with newly acquired genital herpes simplex virus 2 (HSV-2) infection have virus frequently detected at the genital mucosa. Rates of genital shedding initially decrease over time after infection, but data on long-term viral shedding are lacking.

METHODS

For this study, 377 healthy adults with history of symptomatic genital HSV-2 infection collected anogenital swabs for HSV-2 DNA polymerase chain reaction for at least 30 consecutive days.

RESULTS

Time since first genital herpes episode was significantly associated with reduced genital shedding. Total HSV shedding occurred on 33.6% of days in participants <1 year, 20.6% in those 1-9 years, and 16.7% in those ≥10 years from first episode. Subclinical HSV shedding occurred on 26.2% of days among participants <1 year, 13.1% in those 1-9 years, and 9.3% in those ≥10 years from first episode. On days with HSV detection, mean quantity was 4.9 log₁₀ copies/mL for those <1 year, 4.7 log₁₀ copies/mL among those 1-9 years, and 4.6 log₁₀ copies/mL among those ≥10 years since first episode.

CONCLUSIONS

Rates of total and subclinical HSV-2 shedding decrease after the first year following the initial clinical episode. However, viral shedding persists at high rates and copy numbers years after infection, and therefore may pose continued risk of HSV-2 transmission to sexual partners.

Resistance of herpes simplex viruses to nucleoside analogues: mechanisms, prevalence, and management

Herpes simplex viruses (HSV) type 1 and type 2 are responsible for recurrent orolabial and genital infections. The standard therapy for the management of HSV infections includes acyclovir (ACV) and penciclovir (PCV) with their respective prodrugs valacyclovir and famciclovir. These compounds are phosphorylated by the viral thymidine kinase (TK) and then by cellular kinases. The triphosphate forms selectively inhibit the viral DNA polymerase (DNA pol) activity. Drug-resistant HSV isolates are frequently recovered from immunocompromised patients but rarely found in immunocompetent subjects. The gold standard phenotypic method for evaluating the susceptibility of HSV isolates to antiviral drugs is the plaque reduction assay. Plaque autoradiography allows the associated phenotype to be distinguished (TK-wild-type, TK-negative, TK-low-producer, or TK-altered viruses or mixtures of wild-type and mutant viruses). Genotypic characterization of drug-resistant isolates can reveal mutations located in the viral TK and/or in the DNA pol genes. Recombinant HSV mutants can be generated to analyze the contribution of each specific mutation with regard to the drug resistance phenotype. Most ACV-resistant mutants exhibit some reduction in their capacity to establish latency and to reactivate, as well as in their degree of neurovirulence in animal models of HSV infection. For instance, TK-negative HSV mutants establish latency with a lower efficiency than wild-type strains and reactivate poorly. DNA pol HSV mutants exhibit different degrees of attenuation of neurovirulence. The management of ACV- or PCV-resistant HSV infections includes the use of the pyrophosphate analogue foscarnet and the nucleotide analogue cidofovir. There is a need to develop new antiherpetic compounds with different mechanisms of action.