Parameters of CpG oligodeoxynucleotide-induced protection against intravaginal HSV-2 challenge

Curcumin Can Decrease Tissue Inflammation and the Severity of HSV-2 Infection in the Female Reproductive Mucosa

Herpes Simplex Virus Type 2 (HSV-2) is one of the most prevalent sexually transmitted viruses and is a known risk factor for HIV acquisition in the Female Genital Tract (FGT). Previously, we found that curcumin can block HSV-2 infection and abrogate the production of inflammatory cytokines and chemokines by genital epithelial cells in vitro. In this study, we investigated whether curcumin, encapsulated in nanoparticles and delivered by various in vivo routes, could minimize inflammation and prevent or reduce HSV-2 infection in the FGT. Female mice were pre-treated with curcumin nanoparticles through oral, intraperitoneal and intravaginal routes, and then exposed intravaginally to the tissue inflammation stimulant CpG-oligodeoxynucleotide (ODN). Local intravaginal delivery of curcumin nanoparticles, but not intraperitoneal or oral delivery, reduced CpG-mediated inflammatory histopathology and decreased production of pro-inflammatory cytokines Interleukin (IL)-6, Tumor Necrosis Factor Alpha (TNF-α) and Monocyte Chemoattractant Protein-1 (MCP-1) in the FGT. However, curcumin nanoparticles did not demonstrate anti-viral activity nor reduce tissue pathology when administered prior to intravaginal HSV-2 infection. In an alternative approach, intravaginal pre-treatment with crude curcumin or solid dispersion formulations of curcumin demonstrated increased survival and delayed pathology following HSV-2 infection. Our results suggest that curcumin nanoparticle delivery in the vaginal tract could reduce local tissue inflammation. The anti-inflammatory properties of curcumin delivered to the vaginal tract could potentially reduce the severity of HSV-2 infection and decrease the risk of HIV acquisition in the FGT of women.

Effect of Mucosal Cytokine Administration on Selective Expansion of Vaginal Dendritic Cells to Support Nanoparticle Transport

PROBLEM

The capacity of antigen-carrying vaccine nanoparticles (NPs) administered vaginally to stimulate local immune responses may be limited by the relatively low numbers of antigen-presenting cells (APCs) in the genital mucosa. Because inflammation is associated with increased susceptibility to sexually transmitted infections, we sought to increase APC numbers without causing inflammation.

METHOD OF STUDY

In this study, we evaluated intravaginal delivery of chemokines, growth factors, or synthetic adjuvants to expand APCs in reproductive tissues.

RESULTS

We found that granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulated expansion of CD11b+ dendritic cells (DCs) within 24 hr of intravaginal administration, with no effect on Langerhans cells or macrophages. Expansion of the CD11b+ DC population was not associated with increased inflammatory cytokine production, and these cells retained phagocytic function.

CONCLUSION

Our data suggest that non-inflammatory expansion of mucosal APCs by intravaginal GM-CSF could be used as an adjuvanting strategy to potentiate the genital immune response to nanoparticulate mucosal vaccines.

TLR9 and RIG-I signaling in human endocervical epithelial cells modulates inflammatory responses of macrophages and dendritic cells in vitro

The innate immune system has evolved to recognize invading pathogens through pattern recognition receptors (PRRs).Among PRRs, Toll like receptors (TLRs 3, 7/8,9) and RIG-I like receptors (RLRs) have been shown to recognize viral components. Mucosal immune responses to viral infections require coordinated actions from epithelial as well as immune cells. In this respect, endocervical epithelial cells (EEC's) play an important role in initiating innate immune responses via PRRs. It is unknown whether EEC's can alter immune responses of macrophages and dendritic cells (DC's) like its counterparts in intestinal and respiratory systems. In this study, we show that endocervical epithelial cells (End1/E6E7) express two key receptors, TLR9 and RIG-I involved in anti-viral immunity. Stimulation of End1/E6E7 cells lead to the activation of NF-κB and increased secretion of pro-inflammatory cytokines, IL-6 and IL-8. Polarized End1/E6E7 cells responded to apical stimulation with ligands of TLR9 and RIG-I, CpG-ODN and Poly(I:C)LL respectively, without compromising End1/E6E7 cell integrity. At steady state, spent medium from End1/E6E7 cells significantly reduced secretion of pro-inflammatory cytokines from LPS treated human primary monocyte derived macrophages (MDMs) and DC:T cell co-cultures. Spent medium from End1/E6E7 cells stimulated with ligands of TLR9/RIG-I restored secretion of pro-inflammatory cytokines as well as enhanced phagocytosis and chemotaxis of monocytic U937 cells. Spent medium from CpG-ODN and Poly(I:C)LL stimulated End1/E6E7 cells showed significant increased secretion of IL-12p70 from DC:T cell co-cultures. The anti-inflammatory effect of spent media of End1/E6E7 cell was observed to be TGF-β dependent. In summary, the results of our study indicate that EEC's play an indispensable role in modulating anti-viral immune responses at the female lower genital tract.

Immunotherapeutic potential of CpG oligodeoxynucleotides in veterinary species

Innate immunity plays a critical role in host defense against infectious diseases by discriminating between self and infectious non-self. The recognition of infectious non-self involves germ-line encoded pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs). The PAMPs are the components of pathogenic microbes which include not only the cell wall constituents but also the unmethylated 2'-deoxy-ribo-cytosine-phosphate-guanosine (CpG) motifs. These CpG motifs present within bacterial and viral DNA are recognized by toll-like receptor 9 (TLR9), and signaling by this receptor triggers a proinflammatory cytokine response which, in turn, influences both innate and adaptive immune responses. The activation of TLR9 with synthetic CpG oligodeoxynucleotides (ODNs) induces powerful Th1-like immune responses. It has been shown to provide protection against infectious diseases, allergy and cancer in laboratory animal models and some domestic animal species. With better understanding of the basic biology and immune mechanisms, it would be possible to exploit the potential of CpG motifs for animal welfare. The research developments in the area of CpG and TLR9 and the potential applications in animal health have been reviewed in this article.

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.

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.

Tweaking Innate Immunity: the Promise of Innate Immunologicals As Anti-infectives

New and exciting insights into the importance of the innate immune system are revolutionizing our understanding of immune defense against infections, pathogenesis, and the treatment and prevention of infectious diseases. The innate immune system uses multiple families of germline-encoded pattern recognition receptors (PRRs) to detect infection and trigger a variety of antimicrobial defense mechanisms. PRRs are evolutionarily highly conserved and serve to detect infection by recognizing pathogen-associated molecular patterns that are unique to microorganisms and essential for their survival. Toll-like receptors (TLRs) are transmembrane signalling receptors that activate gene expression programs that result in the production of proinflammatory cytokines and chemokines, type I interferons and antimicrobial factors. Furthermore, TLR activation facilitates and guides activation of adaptive immune responses through the activation of dendritic cells. TLRs are localized on the cell surface and in endosomal/lysosomal compartments, where they detect bacterial and viral infections. In contrast, nucleotide-binding oligomerization domain proteins and RNA helicases are located in the cell cytoplasm, where they serve as intracellular PRRs to detect cytoplasmic infections, particularly viruses. Due to their ability to enhance innate immune responses, novel strategies to use ligands, synthetic agonists or antagonists of PRRs (also known as 'innate immunologicals') can be used as stand-alone agents to provide immediate protection or treatment against bacterial, viral or parasitic infections. Furthermore, the newly appreciated importance of innate immunity in initiating and shaping adaptive immune responses is contributing to our understanding of vaccine adjuvants and promises to lead to improved next-generation vaccines.

Induction of innate immune responses in the female genital tract: friend or foe of HIV-1 infection?

Heterosexual transmission of HIV-1 and HSV-2 across the genital tract epithelial tissue is one of the primary routes for dissemination of these viral infections. Mucosal innate immunity is the first line of defense against invading pathogens. A vast majority of mucosal HIV-1 exposures do not result in productive infections which may indicate that the innate mucosal immune system is highly protective. It has been shown that Toll-like receptors (TLR)-induced innate antiviral immunity in the genital mucosa lead to induction of type I and III interferon and prevention of HSV-2 infection. The innate antiviral function of type I and III interferons and other innate factors at genital mucosa against HIV-1 is not well defined. In this review, we summarize our current understanding and advances of the innate mucosal response to genital viral infections, including HIV-1 and HSV-2, focusing on those factors that may prevent or accelerate initial infection. Understanding how each of these components contributes to mucosal innate antiviral immunity may lead to the development of novel and effective strategies to use microbicides or antiviral agents to control HIV-1 acquisition and/or transmission.

Herpes simplex virus and human papillomavirus genital infections: new and investigational therapeutic options

Human papillomavirus and Herpes simplex virus are the most common genital viral infections encountered in clinical practice worldwide. We reviewed the literature focusing on new and experimental treatment modalities for both conditions, based on to the evidence-based data available. The modalities evaluated include topical agents such as immune response modifiers (imiquimod, resiquimod, and interferon), antivirals (penciclovir, cidofovir, and foscarnet), sinecatechins, microbiocidals (SPL7013 gel, and PRO 2000 gel), along with experimental (oligodeoxynucleotides), immunoprophylactic, and immunotherapeutic vaccines.

Subcutaneous, but not intratracheal administration of the TLR9 agonist, CpG DNA transiently reduces parainfluenza-3 virus shedding in newborn lambs

Synthetic oligodeoxynucleotides (ODN) containing CpG motifs signal through TLR9 and activate innate immunity resulting in protection against a variety of parasitic, bacterial and viral pathogens in mouse models. However, few studies have demonstrated protection in humans and large animals. In the present investigations, we evaluated protection by CpG ODN in a parainfluenza-3 (PI-3) virus infection in neonatal lambs. Subcutaneous (SC) injection of CpG ODN induced high levels of 2'5'-A synthetase and significantly reduced PI-3 virus shedding in newborn lambs. Furthermore, pre-treatment of newborn lambs with SC CpG ODN 2 days, but not 6 days prior to the virus challenge was protective. In contrast, intratracheal (IT) administration of CpG ODN induced 2'5'-A synthetase but had no significant impact on PI-3 virus shedding in nasal secretions. We conclude that a systemic administration of CpG ODN and the timing of the treatment are critical for the protection of neonatal lambs against a respiratory viral infection.

Toll-like receptors and genital tract infection

Our knowledge of the immune response to genital tract infection has progressed appreciably in recent years. This review focuses on the innate immune system, in particular the role of Toll-like receptors (TLRs), in controlling genital tract infection. Research into the role of TLRs in recognizing 'pathogen-associated molecular patterns' (PAMPS) has provided an important insight into the host's early immune response. TLRs are activated following binding of microbial components leading to cytokine production, which, in turn, stimulate phagocytic and natural killer cells and mobilize T and B lymphocytes of the antigen-specific acquired immune system. The therapeutic use of TLR agonists as topical agents or for improving CD4+ and CD8+ T-cell responses to microbial vaccines is an important area of ongoing research, particularly with respect to genital mucosal infection.

Application of nanotechnologies for improved immune response against infectious diseases in the developing world

There is an urgent need for new strategies to combat infectious diseases in developing countries. Many pathogens have evolved to elude immunity and this has limited the utility of current therapies. Additionally, the emergence of co-infections and drug resistant pathogens has increased the need for advanced therapeutic and diagnostic strategies. These challenges can be addressed with therapies that boost the quality and magnitude of an immune response in a predictable, designable fashion that can be applied for wide-spread use. Here, we discuss how biomaterials and specifically nanoscale delivery vehicles can be used to modify and improve the immune system response against infectious diseases. Immunotherapy of infectious disease is the enhancement or modulation of the immune system response to more effectively prevent or clear pathogen infection. Nanoscale vehicles are particularly adept at facilitating immunotherapeutic approaches because they can be engineered to have different physical properties, encapsulated agents, and surface ligands. Additionally, nanoscaled point-of-care diagnostics offer new alternatives for portable and sensitive health monitoring that can guide the use of nanoscale immunotherapies. By exploiting the unique tunability of nanoscale biomaterials to activate, shape, and detect immune system effector function, it may be possible in the near future to generate practical strategies for the prevention and treatment of infectious diseases in the developing world.

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

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

Dysregulated macrophage-inflammatory protein-2 expression drives illness in bacterial superinfection of influenza

Influenza virus infection is a leading cause of death and disability throughout the world. Influenza-infected hosts are vulnerable to secondary bacterial infection, however, and an ensuing bacterial pneumonia is actually the predominant cause of influenza-attributed deaths during pandemics. A number of mechanisms have been proposed by which influenza may predispose to superinfection with an unrelated or heterologous pathogen, but the subsequent interaction between the host, virus, and bacteria remains an understudied area. In this study, we develop and examine a novel model of heterologous pulmonary infection in which an otherwise subclinical Bordetella parapertussis infection synergizes with an influenza virus infection to yield a life-threatening secondary pneumonia. Despite a profound pulmonary inflammatory response and unaltered viral clearance, bacterial clearance was significantly impaired in heterologously infected mice. No deficits were observed in pulmonary or systemic adaptive immune responses or the viability or function of infiltrating inflammatory cells to explain this phenomenon, and we provide evidence that the onset of severe pulmonary inflammation actually precedes the increased bacterial burden, suggesting that exacerbated inflammation is independent of bacterial burden. To that end, neutralization of the ELR(+) inflammatory chemokine MIP-2 (CXCL2/GRO-beta) attenuated the inflammation, weight loss, and clinical presentation of heterologously infected mice without impacting bacterial burden. These data suggest that pulmonary inflammation, rather than pathogen burden, is the key threat during bacterial superinfection of influenza and that selective chemokine antagonists may be a novel therapeutic intervention in cases of bacterial superinfection of influenza.

Innate and adaptive immune responses to herpes simplex virus

Immune responses against HSV-1 and HSV-2 are complex and involve a delicate interplay between innate signaling pathways and adaptive immune responses. The innate response to HSV involves the induction of type I IFN, whose role in protection against disease is well characterized in vitro and in vivo. Cell types such as NK cells and pDCs contribute to innate anti-HSV responses in vivo. Finally, the adaptive response includes both humoral and cellular components that play important roles in antiviral control and latency. This review summarizes the innate and adaptive effectors that contribute to susceptibility, immune control and pathogenesis of HSV, and highlights the delicate interplay between these two important arms of immunity.

Immunotherapeutic applications of CpG oligodeoxynucleotide TLR9 agonists

Toll-like receptor 9 (TLR9) agonists have demonstrated substantial potential as vaccine adjuvants, and as mono- or combination therapies for the treatment of cancer and infectious and allergic diseases. Commonly referred to as CpG oligodeoxynucleotides (ODN), TLR9 agonists directly induce the activation and maturation of plasmacytoid dendritic cells and enhance differentiation of B cells into antibody-secreting plasma cells. Preclinical and early clinical data support the use of TLR9 agonists as vaccine adjuvants, where they can enhance both the humoral and cellular responses to diverse antigens. In mouse tumor models TLR9 agonists have shown activity not only as monotherapy, but also in combination with multiple other therapies including vaccines, antibodies, cellular therapies, other immunotherapies, antiangiogenic agents, radiotherapy, cryotherapy, and some chemotherapies. Phase I and II clinical trials have indicated that these agents have antitumor activity as single agents and enhance the development of antitumor T-cell responses when used as therapeutic vaccine adjuvants. CpG ODN have shown benefit in multiple rodent and primate models of asthma and other allergic diseases, with encouraging results in some early human clinical trials. Although their potential clinical contributions are enormous, the safety and efficacy of these TLR9 agonists in humans remain to be determined.

A genital tract peptide epitope vaccine targeting TLR-2 efficiently induces local and systemic CD8+ T cells and protects against herpes simplex virus type 2 challenge

The next generation of needle-free mucosal vaccines is being rationally designed according to rules that govern the way in which the epitopes are recognized by and stimulate the genital mucosal immune system. We hypothesized that synthetic peptide epitopes extended with an agonist of Toll-like receptor 2 (TLR-2), that are abundantly expressed by dendritic and epithelial cells of the vaginal mucosa, would lead to induction of protective immunity against genital herpes. To test this hypothesis, we intravaginally (IVAG) immunized wild-type B6, TLR-2 (TLR2(-/-)) or myeloid differentiation factor 88 deficient (MyD88(-/-)) mice with a herpes simplex virus type 2 (HSV-2) CD8+ T-cell peptide epitope extended by a palmitic acid moiety (a TLR-2 agonist). IVAG delivery of the lipopeptide generated HSV-2-specific memory CD8+ cytotoxic T cells both locally in the genital tract draining lymph nodes and systemically in the spleen. Moreover, lipopeptide-immunized TLR2(-/-) and MyD88(-/-) mice developed significantly less HSV-specific CD8+ T-cell response, earlier death, faster disease progression, and higher vaginal HSV-2 titers compared to lipopeptide-immunized wild-type B6 mice. IVAG immunization with self-adjuvanting lipid-tailed peptides appears to be a novel mucosal vaccine approach, which has attractive practical and immunological features.

FimH adhesin of type 1 fimbriae is a potent inducer of innate antimicrobial responses which requires TLR4 and type 1 interferon signalling

Components of bacteria have been shown to induce innate antiviral immunity via Toll-like receptors (TLRs). We have recently shown that FimH, the adhesin portion of type 1 fimbria, can induce the innate immune system via TLR4. Here we report that FimH induces potent in vitro and in vivo innate antimicrobial responses. FimH induced an innate antiviral state in murine macrophage and primary MEFs which was correlated with IFN-beta production. Moreover, FimH induced the innate antiviral responses in cells from wild type, but not from MyD88(-/-), Trif(-/-), IFN-alpha/betaR(-/-) or IRF3(-/-) mice. Vaginal delivery of FimH, but not LPS, completely protected wild type, but not MyD88(-/-), IFN-alpha/betaR(-/-), IRF3(-/-) or TLR4(-/-) mice from subsequent genital HSV-2 challenge. The FimH-induced innate antiviral immunity correlated with the production of IFN-beta, but not IFN-alpha or IFN-gamma. To examine whether FimH plays a role in innate immune induction in the context of a natural infection, the innate immune responses to wild type uropathogenic E. coli (UPEC) and a FimH null mutant were examined in the urinary tract of C57Bl/6 (B6) mice and TLR4-deficient mice. While UPEC expressing FimH induced a robust polymorphonuclear response in B6, but not TLR4(-/-) mice, mutant bacteria lacking FimH did not. In addition, the presence of TLR4 was essential for innate control of and protection against UPEC. Our results demonstrate that FimH is a potent inducer of innate antimicrobial responses and signals differently, from that of LPS, via TLR4 at mucosal surfaces. Our studies suggest that FimH can potentially be used as an innate microbicide against mucosal pathogens.

Differential induction of innate anti-viral responses by TLR ligands against Herpes simplex virus, type 2, infection in primary genital epithelium of women

Genital epithelial cells (GECs) are the first line of mucosal defense against sexually transmitted infections. We exploited the ability of GECs to mount innate immune responses, by using TLR ligands to induce anti-viral activity against Herpes simplex virus, type 2 (HSV-2). Primary cultures of GECs were grown to confluent, polarized monolayers and found to express different levels of mRNA for TLR1-10. Innate anti-viral responses against HSV-2 infection were determined following treatment with eight different TLR ligands. HSV-2 replication was significantly inhibited following treatment with ligands for TLR3, 5 and 9, while lipo-polysaccharide (LPS), a TLR4 ligand, failed to provide any protection. Biologically active interferon-beta and nitric oxide production by GECs correlated with anti-viral activity. Following treatment with TLR3 ligand Poly I:C, inflammatory cytokines were upregulated. Poly I:C treatment led to activation of downstream transcription factors including interferon regulatory factor-3 (IRF-3) and NFkappaB. Anti-viral responses induced by TLR ligands in GECs may provide a unique alternative to topical microbicides by enhancing body's own mucosal innate defense mechanisms against sexually transmitted viruses.

An intranasal heat shock protein based vaccination strategy confers protection against mucosal challenge with herpes simplex virus

Herpes simplex virus-1 (HSV-1) represents a significant obstacle for vaccine designers, despite decades of investigation. The virus primarily infects the host at vulnerable mucosal surfaces that progresses to lesion development, latency in nervous tissue, and possible reactivation. Therefore, protection at the site of infection is crucial. Mucosal adjuvants are critical for the development of an effective vaccine approach and heat-shock protein 70 (Hsp70) represents an attractive candidate for this purpose. This study demonstrates that Hsp70 coupled to gB498-505 from HSV-1 induced mucosal and systemic priming of CD8(+) T cells capable of protecting C57BL/6 mice against a lethal vaginal challenge. Elevated gB-specific cytotoxicity was observed in the spleen of mice immunized with conjugated Hsp70 and gB498-505. In addition, both vaginal IFNgamma levels and viral clearance were enhanced in mice mucosally immunized with Hsp70 and gB peptide versus peptide only control mice or mice receiving Hsp70 and a control peptide. These studies demonstrate that Hsp70 can be used as an effective mucosal adjuvant capable of generating a protective cell-mediated immune response against HSV-1.

Chemokines and Chemokine Receptors Critical to Host Resistance following Genital Herpes Simplex Virus Type 2 (HSV-2) Infection

HSV-2 is a highly successful human pathogen with a remarkable ability to elude immune detection or counter the innate and adaptive immune response through the production of viral-encoded proteins. In response to infection, resident cells secrete soluble factors including chemokines that mobilize and guide leukocytes including T and NK cells, neutrophils, and monocytes to sites of infection. While there is built-in redundancy within the system, chemokines signal through specific membrane-bound receptors that act as antennae detailing a chemical pathway that will provide a means to locate and eliminate the viral insult. Within the central nervous system (CNS), the temporal and spatial expression of chemokines relative to leukocyte mobilization in response to HSV-2 infection has not been elucidated. This paper will review some of the chemokine/chemokine receptor candidates that appear critical to the host in viral resistance and clearance from the CNS and peripheral tissue using murine models of genital HSV-2 infection.

Amphipathic DNA polymers exhibit antiherpetic activity in vitro and in vivo

Phosphorothioated oligonucleotides have a sequence-independent antiviral activity as amphipathic polymers (APs). The activity of these agents against herpesvirus infections in vitro and in vivo was investigated. The previously established sequence-independent, phosphorothioation-dependent antiviral activity of APs was confirmed in vitro by showing that a variety of equivalently sized homo- and heteropolymeric AP sequences were similarly active against herpes simplex virus type 1 (HSV-1) infection in vitro compared to the 40mer degenerate parent compound (REP 9), while the absence of phosphorothioation resulted in the loss of antiviral activity. In addition, REP 9 demonstrated in vitro activity against a broad spectrum of other herpesviruses: HSV-2 (50% effective concentration [EC(50)], 0.02 to 0.06 microM), human cytomegalovirus (EC(50), 0.02 to 0.13 microM), varicella zoster virus (EC(50), <0.02 microM), Epstein-Barr virus (EC(50), 14.7 microM) and human herpesvirus types 6A/B (EC(50), 2.9 to 10.2 microM). The murine microbicide model of genital HSV-2 was then used to evaluate in vivo activity. REP 9 (275 mg/ml) protected 75% of animals from disease and infection when provided 5 or 30 min prior to vaginal challenge. When an acid-stable analog (REP 9C) was used, 75% of mice were protected when treated with 240 mg/ml 5 min prior to infection (P < 0.001), while a lower dose (100 mg/ml) protected 100% of the mice (P < 0.001). The acid stable REP 9C formulation also provided protection at 30 min (83%, P < 0.001) and 60 min (50%, P = 0.07) against disease. These observations suggest that APs may have microbicidal activity and potential as broad-spectrum antiherpetic agents and represent a novel class of agents that should be studied further.

The role of toll-like receptor ligands/agonists in protection against genital HSV-2 infection

Control of virus replication initially depends on rapid activation of the innate immune responses. Toll-like receptor (TLR) ligands are potent inducers of innate immunity against viral infections, including herpes simplex virus (HSV). HSV-2 is currently one of the most common sexually transmitted infections in developed nations and is becoming more prevalent in adolescents. HSV-2 infects the genital mucosa and is associated with an increased risk of obtaining other sexually transmitted infections such as HIV. There is currently no vaccine available against HSV-2. In the last several years, there has been an interest in utilizing Toll-like receptor (TLR) ligands to initiate innate immune responses in order to provide an early line of defence against viral replication. This review highlights recent studies investigating the effect of various TLR ligands on genital HSV-2 infection. A considerable body of information has been published on the effect of local delivery of TLR ligands on HSV-2 replication in genital mucosa. We have outlined ligands that have a potential to provide protection against HSV-2 infection. In addition, we have presented possible mechanisms by which the local delivery of TLR ligands provides innate protection against genital HSV-2.

Induction of innate immunity against herpes simplex virus type 2 infection via local delivery of Toll-like receptor ligands correlates with beta interferon production

Toll-like receptors (TLRs) constitute a family of innate receptors that recognize and respond to a wide spectrum of microorganisms, including fungi, bacteria, viruses, and protozoa. Previous studies have demonstrated that ligands for TLR3 and TLR9 induce potent innate antiviral responses against herpes simplex virus type 2 (HSV-2). However, the factor(s) involved in this innate protection is not well-defined. Here we report that production of beta interferon (IFN-beta) but not production of IFN-alpha, IFN-gamma, or tumor necrosis factor alpha (TNF-alpha) strongly correlates with innate protection against HSV-2. Local delivery of poly(I:C) and CpG oligodeoxynucleotides induced significant production of IFN-beta in the genital tract and provided complete protection against intravaginal (IVAG) HSV-2 challenge. There was no detectable IFN-beta in mice treated with ligands for TLR4 or TLR2, and these mice were not protected against subsequent IVAG HSV-2 challenge. There was no correlation between levels of TNF-alpha or IFN-gamma in the genital tract and protection against IVAG HSV-2 challenge following TLR ligand delivery. Both TNF-alpha(-/-) and IFN-gamma(-/-) mice were protected against IVAG HSV-2 challenge following local delivery of poly(I:C). To confirm that type I interferon, particularly IFN-beta, mediates innate protection, mice unresponsive to type I interferons (IFN-alpha/betaR(-/-) mice) and mice lacking IFN regulatory factor-3 (IRF-3(-/-) mice) were treated with poly(I:C) and then challenged with IVAG HSV-2. There was no protection against HSV-2 infection following poly(I:C) treatment of IFN-alpha/betaR(-/-) or IRF-3(-/-) mice. Local delivery of murine recombinant IFN-beta protected C57BL/6 and IRF-3(-/-) mice against IVAG HSV-2 challenge. Results from these in vivo studies clearly suggest a strong correlation between IFN-beta production and innate antiviral immunity against HSV-2.

A crucial role for plasmacytoid dendritic cells in antiviral protection by CpG ODN-based vaginal microbicide

Topical microbicides represent a promising new approach to preventing HIV and other sexually transmitted infections. TLR agonists are ideal candidates for microbicides, as they trigger a multitude of antiviral genes effective against a broad range of viruses. Although vaginal application of CpG oligodeoxynucleotides (ODNs) and poly I:C has been shown to protect mice from genital herpes infection, the mechanism by which these agents provide protection remains unclear. Here, we show that plasmacytoid DCs (pDCs) are required for CpG ODN-mediated protection against lethal vaginal challenge with herpes simplex virus type 2 (HSV-2). Moreover, we demonstrate that cells of both the hematopoietic and stromal compartments must respond to CpG ODN via TLR9 and to type I IFNs through IFN-alphabeta receptor (IFN-alphabetaR) for protection. Thus, crosstalk between pDCs and vaginal stromal cells provides for optimal microbicide efficacy. Our results imply that temporally and spatially controlled targeting of CpG ODN to pDCs and epithelial cells can potentially maximize their effectiveness as microbicides while minimizing the associated inflammatory responses.

Therapeutic potential of Toll-like receptor 9 activation

In the decade since the discovery that mouse B cells respond to certain unmethylated CpG dinucleotides in bacterial DNA, a specific receptor for these 'CpG motifs' has been identified, Toll-like receptor 9 (TLR9), and a new approach to immunotherapy has moved into the clinic based on the use of synthetic oligodeoxynucleotides (ODN) as TLR9 agonists. This review highlights the current understanding of the mechanism of action of these CpG ODN, and provides an overview of the preclinical data and early human clinical trial results using these drugs to improve vaccines and treat cancer, infectious disease and allergy/asthma.

Herpes simplex virus and toll-like receptors

The earliest interactions between viruses and host cells are critical to determining the outcome of infections. The interactions between a virus and its host cells that lead to the production of inflammatory cytokines are essential to the development of T cells and antibodies that provide long-term defense against the invaders. At the same time, however, these same cytokines (or sometimes other mediators or chemokines) stimulate inflammation, which may lead to localized tissue damage and/or systemic circulatory collapse and death. This review focuses on the interaction between Toll-like receptors, a critical component of the innate immune system of mammals, and their role in herpes simplex pathogenesis and immunity.

NK and NKT cell-independent contribution of interleukin-15 to innate protection against mucosal viral infection

Interleukin-15 (IL-15) is essential for the development, maturation, and function of NK and NKT cells, which are critical components of the innate immune defense against viral infections. We recently showed that mice lacking IL-15 and/or NK/NKT cells are significantly more susceptible to intravaginal (IVAG) herpes simplex virus type 2 (HSV-2) infection than control mice. For this study, we examined whether IL-15 has any direct antiviral activity, independent of NK/NKT cells, in innate protection against HSV-2 infection. A sensitive enzyme-linked immunosorbent assay for murine IL-15 was developed and used to show that IVAG HSV-2 infection induces IL-15 in vaginal washes. Using immunohistochemistry, we detected IL-15-positive cells in the submucosa and vaginal epithelium following IVAG HSV-2 infection. Local, but not systemic, delivery of murine recombinant IL-15 (mrIL-15) to the genital mucosae of IL-15(-/-) and RAG-2(-/-) gamma(c)(-/-) mice, which both lack NK and NKT cells, resulted in significant reductions in HSV-2 titers in genital washes and 60% survival following IVAG HSV-2 challenge. Furthermore, we showed that IL-15 is important for CpG oligodeoxynucleotide (ODN)-induced innate protection against genital HSV-2 infection. While 100% of CpG ODN-treated RAG2(-/-) gamma(c)(-/-) mice, which are capable of producing IL-15 but lack NK/NKT cells, survived an IVAG HSV-2 challenge, only 60% of CpG ODN-treated IL-15(-/-) mice survived, and all of these mice had similar vaginal viral titers to those in control mice by day 3 postchallenge. Lastly, a treatment of RAW264.7 cells with mrIL-15 induced the production of tumor necrosis factor alpha and beta interferon (IFN-beta), but not IFN-alpha, and significantly protected them against HSV-2 infection in vitro. The results of these studies indicate that IL-15 can act independently of NK/NKT cells in mediating the innate defense against viral infection.

Mucosal delivery of CpG oligodeoxynucleotides expands functional dendritic cells and macrophages in the vagina

Antigen-presenting cells (APC) are specialized sentinel cells that sense pathogens within tissues and then activate appropriate immune effector cells in lymphoid organs. Recent evidence, however, suggests that APC can also induce effector cells in non-lymphoid organs. The purpose of this study was to determine the effect of intravaginal (IVAG) delivery of CpG-oligodeoxynucleotide (ODN) on expansion of resident genital APC. Our results show that delivery of CpG-ODN to the murine genital tract induced a rapid and significant, but transient expansion of genital APC in situ. As early as 12 hr post CpG-ODN delivery, we observed an enhanced level of F4/80+ major histocompatibility complex (MHC) class II-negative macrophages in the genital tissue. This was followed by increased levels of F4/80/MHC class II double-positive cells, as well as MHC class II, CD11c and CD86 triple-positive dendritic cells (DC) at 48 hr. Expanded APC levels at 48 hr post CpG-ODN resulted in increased ability of genital cells to induce an allogenic mixed leucocyte reaction. By 72 hr after CpG-ODN treatment, APC levels were not distinguishable from naive levels. Therefore, these results clearly show that administration of CpG-ODN to the genital tract induced a marked but transient enhancement of APC within the genital tissue, and that these APC appear to possess functional capacity. Furthermore, these results indicate that IVAG-CpG-ODN may be an important factor for the enhancement of local antigen presentation in the genital tract through increased DC numbers.

Strategies for enhancing the immunostimulatory effects of CpG oligodeoxynucleotides

Synthetic oligodeoxynucleotides (ODN) containing CpG sequences are recognized as a "danger" signal by the immune system of mammals. As a consequence, CpG ODN stimulate innate and adaptive immune responses in humans and a variety of animal species. Indeed, the potential of CpG ODN as therapeutic agents and vaccine adjuvants has been demonstrated in animal models of infectious diseases, allergy and cancer and are currently undergoing clinical trials in humans. While CpG ODN are potent activators of the immune system, their biologic activity is often transient, subsequently limiting their therapeutic application. Modifications in the CpG ODN backbone chemistry, various delivery methods including mixing or cross-linking of ODN to other carrier compounds have been shown to significantly enhance the biologic activity of ODN. However, the exact mechanisms that mediate this enhancement of activity are not well understood and may include local cell recruitment and activation, cytokine production, upregulation of receptor expression and increasing the half-life of ODN through creation of a depot. We will review the various approaches that have been used in enhancing the immunostimulatory effects of CpG ODN in vivo and also discuss the possible mechanisms that may be involved in this enhancement.

Molecular adjuvants for mucosal immunity

Mucosal surfaces represent the entry route of a multitude of viral pathogens. For many of these viruses, such as the herpes simplex viruses and human immunodeficiency virus, no effective vaccine exists. Hence, it is important that prospective vaccines engender maximal immunity at these susceptible sites. Genetic vaccines encoding adjuvant molecules represent one approach to optimize mucosal as well as systemic immunity. Promising candidates include various inflammatory cytokines and chemokines that might be used to enhance the primary response to a level sufficient for protection. Encouraging studies involving cytokines such as granulocyte/macrophage colony-stimulating factor, interleukin-2 (IL-2), IL-12, IL-18, and many others are examined. Notable chemokines that may offer hope in such efforts include IL-8, RANTES, CCL19, CCL21, and a few others. Combinatorial approaches utilizing several cytokines and chemokines will most likely yield the greatest success. In addition, as more is discovered regarding the requirements for memory development of T cells, boosters involving key cytokines such as IL-15 and IL-23 may prove beneficial to long-term maintenance of the memory pool. This review summarizes the progress in the use of genetic vaccines to achieve mucosal immunity and discusses the needed strategies to maximize long-term prospective immunity at this vulnerable entry site.