Elevated elafin/trappin-2 in the female genital tract is associated with protection against HIV acquisition

Factors Important to the Prioritization and Development of Successful Topical Microbicides for HIV-1

Significant advancements in topical microbicide development have occurred since the prevention strategy was first described as a means to inhibit the sexual transmission of HIV-1. The lack of clinical efficacy of the first generation microbicide products has focused development attention on specific antiretroviral agents, and these agents have proven partially successful in human clinical trials. With greater understanding of vaginal and rectal virus infection, replication, and dissemination, better microbicide products and delivery strategies should result in products with enhanced potency. However, a variety of development gaps exist which relate to product dosing, formulation and delivery, and pharmacokinetics and pharmacodynamics which must be better understood in order to prioritize microbicide products for clinical development. In vitro, ex vivo, and in vivo models must be optimized with regard to these development gaps in order to put the right product at the right place, at the right time, and at the right concentration for effective inhibition of virus transmission. As the microbicide field continues to evolve, we must harness the knowledge gained from unsuccessful and successful clinical trials and development programs to continuously enhance our preclinical development algorithms.

Innate immunity in the control of HIV/AIDS: recent advances and open questions

From the publication of the first AIDS issue onwards, major advances have been made in the field of innate immunity during HIV infection. Innate immunity can be defined as the first and unspecific lines of defense constitutively present and ready to be mobilized upon infection. Although a large body of literature adamantly highlights that innate immunity is a critical weapon of defense against HIV and its simian parents (simian immunodeficiency virus, SIV), innate immunity is still underexplored. Focusing on innate immunity may open new paths for the development of innovative therapeutics and vaccine strategies against HIV. Understanding innate immunity may shed light on the natural protection occurring in rare HIV-1-infected individuals who control their infection. This review focuses on innate mechanisms sensing HIV-1 entry and controlling HIV-1 infection, as well as promoting inflammation and shaping adaptive immunity.

The WAP protein Trappin-2/Elafin: a handyman in the regulation of inflammatory and immune responses

Trappin-2/Elafin is a potent serine protease inhibitor which prevents excessive damage under inflammatory status. This "alarm-antiprotease" is locally expressed by epithelial cells and immune cells such as macrophages and γδ T cells. It has also been proven to modulate a wide range of parameters that are critical for the inflammation process like modulating the NFκB pathway, cytokine secretion and cell recruitment. In addition, Trappin-2/Elafin was shown to possess anti-microbial properties against different classes of pathogens including viruses, fungi and bacteria. Studies also linked Trappin-2/Elafin to either susceptibility or protection against inflammatory disease and infections, even though the mechanisms remains poorly understood. This review will discuss some of the pleiotropic effects displayed by Trappin-2/Elafin, and the properties that could be used to prevent infection or to protect against inflammation.

Lactoferrin: an alternative view of its role in human biological fluids

Lactoferrin is a major component of biologically important mucosal fluids and of the specific granules of neutrophils. Understanding its biological function is essential for understanding neutrophil- and mucosal-mediated immunity. In this review, we reevaluate the in vivo functions of human lactoferrin (hLF) emphasizing in vivo studies and in vitro studies performed in biologically relevant fluids. We discuss the evidence in the literature that supports (or does not support) proposed roles for hLF in mucosal immunity and in neutrophil function. We argue that the current literature supports a microbiostatic role, but not a microbicidal role, for hLF in vivo. The literature also supports a role for hLF in inhibiting colonization and infection of epithelial surfaces by microorganisms and in protecting tissues from neutrophil-mediated damage. Using this information, we briefly discuss hLF in the context of the complex biological fluids in which it is found.

Trappin-2/elafin modulate innate immune responses of human endometrial epithelial cells to PolyI:C

Background

Upon viral recognition, innate and adaptive antiviral immune responses are initiated by genital epithelial cells (ECs) to eradicate or contain viral infection. Such responses, however, are often accompanied by inflammation that contributes to acquisition and progression of sexually transmitted infections (STIs). Hence, interventions/factors enhancing antiviral protection while reducing inflammation may prove beneficial in controlling the spread of STIs. Serine antiprotease trappin-2 (Tr) and its cleaved form, elafin (E), are alarm antimicrobials secreted by multiple cells, including genital epithelia.

Methodology and Principal Findings

We investigated whether and how each Tr and E (Tr/E) contribute to antiviral defenses against a synthetic mimic of viral dsRNA, polyinosine-polycytidylic acid (polyI∶C) and vesicular stomatitis virus. We show that delivery of a replication-deficient adenovector expressing Tr gene (Ad/Tr) to human endometrial epithelial cells, HEC-1A, resulted in secretion of functional Tr, whereas both Tr/E were detected in response to polyI∶C. Moreover, Tr/E were found to significantly reduce viral replication by either acting directly on virus or through enhancing polyI∶C-driven antiviral protection. The latter was associated with reduced levels of pro-inflammatory factors IL-8, IL-6, TNFα, lowered expression of RIG-I, MDA5 and attenuated NF-κB activation. Interestingly, enhanced polyI∶C-driven antiviral protection of HEC-Ad/Tr cells was partially mediated through IRF3 activation, but not associated with higher induction of IFNβ, suggesting multiple antiviral mechanisms of Tr/E and the involvement of alternative factors or pathways.

Conclusions and Significance

This is the first evidence of both Tr/E altering viral binding/entry, innate recognition and mounting of antiviral and inflammatory responses in genital ECs that could have significant implications for homeostasis of the female genital tract.

Dissecting the HIV-specific immune response: a systems biology approach

PURPOSE OF REVIEW

Several unique HIV-infected or HIV-resistant cohorts have been studied over the years to try and delineate the correlates of protection. Although several mechanisms have been put forward, studies aiming to integrate the different mechanisms into a comprehensive model are still lacking. Current systems biology approaches emphasize the importance of unifying independent datasets, provide tools that facilitate hypothesis formulation and testing, and direct us toward uncovering novel therapeutic targets by defining molecular networks perturbed during disease. This review will focus on the current findings that utilized systems biology techniques in order to identify correlates of protection from HIV disease progression and resistance to infection in unique cohorts of individuals as well as in nonhuman primate models of SIV infection.

RECENT FINDINGS

Using systems biology technologies and data analysis tools, the studies described herein have found that pathways implicated in survival, cell cycling, inflammation, and oxidative stress work in unison to limit pathology caused by chronic immune activation. This situation favors the survival of effector lymphocytes and limits the dissemination of viral particles in HIV elite controllers, exposed-uninfected individuals, and natural hosts of SIV infection.

SUMMARY

Systems and computational biology tools have clearly expanded our understanding of HIV pathogenesis by unifying independent observations and by giving us novel molecular targets to pursue. These molecular signatures have the potential to uncover correlates of protection in HIV disease and, in the era of personalized medicine, to determine predictive signatures of treatment efficacy and/or failure.

The Microbiological Context of HIV Resistance: Vaginal Microbiota and Mucosal Inflammation at the Viral Point of Entry

Immune activation is increasingly recognized as a critical element of HIV infection and pathogenesis, causing expansion of virus founder populations at the mucosal port of entry and eventual exhaustion of cellular immune effectors. HIV susceptibility is well known to be influenced by concurrent sexually transmitted infections; however, the role of commensal vaginal microbiota is poorly characterized. Bacterial vaginosis (BV) is a risk factor for HIV acquisition in studies worldwide; however, the etiology of BV remains enigmatic, and the mechanisms by which BV increases HIV susceptibility are not fully defined. A model of how vaginal microbiota influences HIV transmission is considered in the context of a well-established cohort of HIV-exposed seronegative (HESN) commercial sex workers (CSW) in Nairobi, Kenya, many of whom have increased levels of anti-inflammatory factors in vaginal secretions and reduced peripheral immune activation (immune quiescence). Elucidation of the relationship between complex microbial communities and inflammatory mucosal responses underlying HIV infection should be a priority for future prevention-focussed research.

Advances in HIV microbicide development

There is an urgent need control the spread of the global HIV pandemic. A microbicide, or topical drug applied to the mucosal environment to block transmission, is a promising HIV prevention strategy. The development of a safe and efficacious microbicide requires a thorough understanding of the mucosal environment and its role in HIV transmission. Knowledge of the key events in viral infection identifies points at which the virus might be most effectively targeted by a microbicide. The cervicovaginal and rectal mucosa play an important role in the innate defense against HIV, and microbicides must not interfere with these functions. In this review, we discuss the current research on HIV microbicide development.

Profiling cervical lavage fluid by SELDI-TOF mass spectrometry

The mucosal surface of the female genital tract is the first site of contact for many sexually transmitted infections and serves as the first layer of defense. This layer has components of both the innate and adaptive immune systems to protect against infections. For these reasons, this fluid is a major focus of study to understand the pathogenesis of different infectious diseases. Novel tools are available to allow for the analysis of the components of this mucosal layer, including the area of proteomics. The emergence of proteomics has allowed for the development of many types of platforms for protein profiling, including gel-based technologies (2-dimensional differential in-gel electrophoresis) and mass spectrometry-based techniques. SELDI-TOF, a mass spectrometry-based platform coupled to on-chip chromatographic separation, has been developed as a high-throughput technique to profile complex protein samples. This chapter will outline detailed methods to profile cervical mucosal samples by SELDI-TOF and can serve as a guideline for other types of mucosal samples.

Anti-HIV-1 activity of elafin is more potent than its precursor's, trappin-2, in genital epithelial cells

Cervicovaginal lavage fluid (CVL) is a natural source of anti-HIV-1 factors; however, molecular characterization of the anti-HIV-1 activity of CVL remains elusive. In this study, we confirmed that CVLs from HIV-1-resistant (HIV-R) compared to HIV-1-susceptible (HIV-S) commercial sex workers (CSWs) contain significantly larger amounts of serine antiprotease trappin-2 (Tr) and its processed form, elafin (E). We assessed anti-HIV-1 activity of CVLs of CSWs and recombinant E and Tr on genital epithelial cells (ECs) that possess (TZM-bl) or lack (HEC-1A) canonical HIV-1 receptors. Our results showed that immunodepletion of 30% of Tr/E from CVL accounted for up to 60% of total anti-HIV-1 activity of CVL. Knockdown of endogenous Tr/E in HEC-1A cells resulted in significantly increased shedding of infectious R5 and X4 HIV-1. Pretreatment of R5, but not X4 HIV-1, with either Tr or E led to inhibition of HIV-1 infection of TZM-bl cells. Interestingly, when either HIV-1 or cells lacking canonical HIV-1 receptors were pretreated with Tr or E, HIV-1 attachment and transcytosis were significantly reduced, and decreased attachment was not associated with altered expression of syndecan-1 or CXCR4. Determination of 50% inhibitory concentrations (IC(50)) of Tr and E anti-HIV-1 activity indicated that E is ∼130 times more potent than its precursor, Tr, despite their equipotent antiprotease activities. This study provides the first experimental evidence that (i) Tr and E are among the principal anti-HIV-1 molecules of CVL; (ii) Tr and E affect cell attachment and transcytosis of HIV-1; (iii) E is more efficient than Tr regarding anti-HIV-1 activity; and (iv) the anti-HIV-1 effect of Tr and E is contextual.

Bacterial vaginosis, HIV serostatus and T-cell subset distribution in a cohort of East African commercial sex workers: retrospective analysis

OBJECTIVE

Although bacterial vaginosis is a known correlate of HIV infection, no previous studies have investigated whether women defined as HIV-exposed seronegative (HESN) are less likely to have bacterial vaginosis. Little is known about the effects of bacterial vaginosis on systemic immune activation associated with HIV+ serostatus.

DESIGN

Cohort-based retrospective analysis of bacterial vaginosis in relation to HESN status, HIV+ serostatus and peripheral T-helper cells, with cross-sectional analysis of bacterial vaginosis in relation to peripheral T-regulatory cells (Tregs).

METHODS

Bacterial vaginosis diagnosis by Gram stain and determination of systemic CD4(+) and CD8(+) T-helper cell frequency by flow cytometry for 3504 vaginal samples from 988 commercial sex workers over 4 years. Treg phenotyping by FoxP3 staining and multiparameter flow cytometry in peripheral blood of 97 women at a single time-point.

RESULTS

No differences in bacterial vaginosis diagnosis were observed between HESN and other HIV-negative (HIV-N) controls; however, HIV+ women were more likely to be diagnosed with bacterial vaginosis compared to all HIV-negative women (HESN/HIV-N combined). HIV+ women with bacterial vaginosis had significantly higher CD4(+)/CD8(+) T-helper cell counts and a lower CD4/CD8 ratio, as well as fewer Tregs as a proportion of total T-helper cells, compared to bacterial vaginosis-negative women. The number of bacterial vaginosis diagnoses in this cohort has decreased significantly over time.

CONCLUSION

Bacterial vaginosis is associated with HIV serostatus and shifts in distribution of T-cell subsets. A concomitant reduction in bacterial vaginosis and HIV infections over time suggests that the elucidation of bacterial vaginosis-HIV interactions will be critical to further understanding of HIV pathogenesis and prevention in this high-risk group.

War and peace between WAP and HIV: role of SLPI, trappin-2, elafin and ps20 in susceptibility to HIV infection

Despite tremendous advances in our understanding of HIV/AIDS since the first cases were reported 30 years ago, we are still a long way from understanding critical steps of HIV acquisition, pathogenesis and correlates of protection. Our new understanding of the importance of the mucosa as a target for HIV infection, as well as our recent observations showing that altered expression and responses of innate pattern recognition receptors are significantly associated with pathogenesis and resistance to HIV infection, indicate that correlates of immunity to HIV are more likely to be associated with mucosal and innate responses. Most of the heterosexual encounters do not result in productive HIV infection, suggesting that the female genital tract is protected against HIV by innate defence molecules, such as antiproteases, secreted mucosally. The present review highlights the role and significance of the serine protease inhibitors SLPI (secretory leucocyte protease inhibitor), trappin-2, elafin and ps20 (prostate stromal protein 20 kDa) in HIV susceptibility and infection. Interestingly, in contrast with SLPI, trappin-2 and elafin, ps20 has been shown to enhance HIV infectivity. Thus understanding the balance and interaction of these factors in mucosal fluids may significantly influence HIV infection.

SLPI and elafin: multifunctional antiproteases of the WFDC family

SLPI (secretory leucoprotease inhibitor) and elafin represent the archetypal members of the WFDC [WAP (whey acidic protein) four disulfide core] family of proteins, and were originally characterized as protease inhibitors but have since been shown to possess a wider repertoire of activities. These functions include antimicrobial and immunomodulatory properties, suggesting that these proteins may play key roles in the innate immune response, and indicate the potential to develop some of these proteins as novel therapeutics. Susceptibility to host and bacterial protease cleavage may, however, limit the efficacy of recombinant protein therapies in diseases with a high protease burden such as CF (cystic fibrosis) lung disease. To overcome this problem, further refinement of the native proteins will be required to provide effective treatment strategies.

Targeting HIV-1 innate immune responses therapeutically

PURPOSE OF REVIEW

The early stage of HIV-1 infection is when the virus is most vulnerable, and should therefore offer the best opportunity for therapeutic interventions. This review addresses the recent progress in the understanding of innate immune responses against HIV-1 with focus on the potential targets for prevention of viral acquisition, replication and dissemination.

RECENT FINDINGS

Research indicates that the host-derived factor trappin-2/elafin is protective against HIV, whereas semen-derived enhancer of viral infection and defensins 5 and 6 enhance viral transmission. Further, studies suggest that stimulation of TLR4 and inhibition of TLR7-9 pathways may be HIV suppressive. The regulation and function of viral restriction factors tetherin and APOBEC3G have been investigated and a molecule mimicking the premature uncoating achieved by TRIM5α, PF74, has been identified. Chloroquine has been shown to inhibit plasmacytoid dendritic cell activation and suppress negative modulators of T-cell responses. Blockade of HMBG1 has been found to restore natural-killer-cell-mediated killing of infected dendritic cells, normally suppressed by HIV-1. Interestingly, when used as adjuvants, EAT-2 and heat shock protein gp96 reportedly enhance innate immune responses.

SUMMARY

Several targets for innate immunity-mediated therapeutics have been identified. Nonetheless, more research is required to unveil their underlying mechanisms and interactions before testing these molecules in clinical trials.

Comprehensive proteomic study identifies serpin and cystatin antiproteases as novel correlates of HIV-1 resistance in the cervicovaginal mucosa of female sex workers

Not all individuals exposed to HIV-1 become infected, and evidence from HIV-1 highly exposed seronegative women (HIV-1-resistant) suggests that mucosal factors in the female genital tract, the first site of contact for the virus, are playing a role. To better understand factors mediating protection from HIV-1, we performed a large clinical study using the tools of systems biology to fully characterize the cervicovaginal mucosa proteome in HIV-1-resistant women. Cervicovaginal lavage fluid was collected from 293 HIV-1-resistant, uninfected, and infected sex workers and analyzed by 2D-LC LTQ-FT-MS. Of the more than 360 unique proteins identified, 41 were differentially abundant (>3-fold cutoff) in HIV-1-resistant women. The majority of over-abundant proteins were antiproteases (>40%), some with described anti-inflammatory and anti-HIV-1 activity. Quantification of specific anti-HIV-1 antiproteases Serpin A1, Serpin A3, and Cystatin B and an epithelial antiprotease A2ML1 found them to be significantly over-abundant in HIV-1-resistant women (p = 0.004; p = 0.046; p = 0.0003; and p = 0.04, respectively). Expression levels were not correlated to sexual practices or other epidemiological factors. Mucosal antiprotease levels correlated with pro-inflammatory cytokine concentration (p = <0.0001), but independently of pro-inflammatory cytokine levels in HIV-1-resistant women including TNF-alpha, IL-1 alpha, IL-1 beta, IL-6, and IL-8. This comprehensive systems biology approach identifies mucosal serpins and cystatins as novel correlates of HIV-1-resistance. This represents the first study characterizing these factors in the female genital tract.

Primary human epithelial cell culture system for studying interactions between female upper genital tract and sexually transmitted viruses, HSV-2 and HIV-1

Evidence from clinical and epidemiological studies indicates that women are disproportionately susceptible to sexually transmitted viral infections. To understand the underlying biological basis for this increased susceptibility, more studies are needed to examine the acute events in the female reproductive tract following exposure to viruses during sexual transmission. The epithelial lining of the female reproductive tract is the primary barrier that sexually transmitted viruses, such as HIV-1 and HSV-2 need to infect or traverse, in order to initiate and establish productive infection. We have established an ex-vivo primary culture system to grow genital epithelial cells from upper reproductive tract tissues of women. Using these cultures, we have extensively examined the interactions between epithelial cells of the female genital tract and HSV-2 and HIV-1. In this review, we describe in detail the experimental protocol to grow these cultures, monitor their differentiation and inoculate with HSV-2 and HIV-1. Prospective use of these cultures to re-create the microenvironment in the reproductive tract is discussed.

Therapeutic potential of human elafin

Elafin is an endogenous human protein composed of an N-terminal transglutaminase substrate motif and a C-terminal WAP (whey acidic protein)-domain with antiproteolytic properties. Elafin is expressed predominantly in epithelial tissue and potently inhibits the neutrophil-derived serine proteases elastase and proteinase-3 by a competitive tight-binding mechanism. Furthermore, it inhibits EVE (endogenous vascular elastase). Studies on several animal models show that antiprotease augmentation with human elafin is an effective strategy in the treatment of inflammatory vascular, systemic and pulmonary diseases and of inflammation triggered by reperfusion injury. This raises the possibility that elafin might be effective in the treatment of a variety of human inflammatory diseases. In a Phase I clinical trial, elafin was well tolerated. Phase II trials are underway to investigate the therapeutic effects of elafin on post-operative inflammation and the clinical consequences of major surgery. Of particular interest is the reduction of post-operative morbidity after oesophagus cancer surgery, coronary artery bypass surgery and kidney transplantation.

Innate immunity in the human female reproductive tract: endocrine regulation of endogenous antimicrobial protection against HIV and other sexually transmitted infections

Mucosal surfaces of the female reproductive tract (FRT) contain a spectrum of antimicrobials that provide the first line of defense against viruses, bacteria, and fungi that enter the lower FRT. Once thought to be a sterile compartment, the upper FRT is periodically exposed to pathogens throughout the menstrual cycle. More recently, secretions from the upper FRT have been shown to contribute to downstream protection in the lower FRT. In this review, we examine the antimicrobials in FRT secretions made by immune cells and epithelial cells in the upper and lower FRT that contribute to innate protection. Because each site is hormonally regulated to maintain fertility, this review focuses on the contributions of hormone balance during the menstrual cycle to innate immune protection. As presented in this review, studies from our laboratory and others demonstrate that sex hormones regulate antimicrobials produced by innate immune cells throughout the FRT. The goal of this review is to examine the spectrum of antimicrobials in the FRT and the ways in which they are regulated to provide protection against pathogens that compromise reproductive health and threaten the lives of women.

Decidual soluble factors participate in the control of HIV-1 infection at the maternofetal interface

Background

Maternofetal transmission (MFT) of HIV-1 is relatively rare during the first trimester of pregnancy despite the permissivity of placental cells for cell-to-cell HIV-1 infection. Invasive placental cells interact directly with decidual cells of the uterine mucosa during the first months of pregnancy, but the role of the decidua in the control of HIV-1 transmission is unknown.

Results

We found that decidual mononuclear cells naturally produce low levels of IL-10, IL-12, IL-15, TNF-α, IFN-α, IFN-γ and CXCL-12 (SDF-1), and large amounts of CCL-2 (MCP1), CCL-3 (MIP-1α), CCL-4 (MIP-1β), CCL-5 (Rantes), CXCL-10 (IP-10), IL-6 and IL-8. CCL-3 and CCL-4 levels were significantly upregulated by in vitro infection with R5 HIV-1 but not X4. Decidual CD14+ antigen presenting cells were the main CCL-3 and CCL-4 producers among decidual leukocytes. R5 and X4 HIV-1 infection was inhibited by decidual cell culture supernatants in vitro. Using HIV-1 pseudotypes, we found that inhibition of the HIV-1 entry step was inhibited by decidual soluble factors.

Conclusion

Our findings show that decidual innate immunity (soluble factors) is involved in the control of HIV-1 infection at the maternofetal interface. The decidua could thus serve as a mucosal model for identifying correlates of protection against HIV-1 infection.

Outcomes of a National Institute of Allergy and Infectious Diseases Workshop on understanding HIV-exposed but seronegative individuals

The fascinating conundrum that some individuals who are exposed to HIV in ways that would make viral transmission highly likely, yet are able to remain uninfected, has been appreciated for many years. As early as the late 1980s, reports of such individuals began appearing in the HIV/AIDS literature. Despite the critical importance of understanding possible mechanisms of natural HIV resistance for developing effective prevention strategies, numerous obstacles have prevented this essential area of scientific exploration from moving forward. The Workshop held on July 8-9, 2010 and supported by the Office of AIDS Research (OAR), the National Institute of Allergy and Infectious Diseases (NIAID), and the National Institute on Drug Abuse (NIDA) at the NIH hosted 200 participants and utilized the expertise of 42 AIDS researchers as invited speakers, session chairs, and discussion leaders for presentations and breakout sessions in an attempt to remove some of those obstacles. Accomplishments of the participants included developing a consensus for a new general term for the field, HIV-exposed seronegative (HESN), while recognizing the necessity to identify and utilize secondary descriptive criteria such as exposure level, risk group, duration of seronegativity, or natural resistance. Three key questions for future research were also identified by the group: (1) What is different in HESN versus those who get infected? (2) What is the immune response in HESN and is it just a marker of exposure or a correlate of protection? (3) What are the HESN host factors that help HESN resist infection? This report briefly summarizes the presentations, and describes future directions for addressing these questions and challenges.

Genetic and Immunological Factors Involved in Natural Resistance to HIV-1 Infection

Infection with Human immunodeficiency virus type-1 (HIV-1) induces severe alterations of the immune system leading to an increased susceptibility to opportunistic infections and malignancies. However, exposure to the virus does not always results in infection. Indeed, there exist individuals who have been repeatedly exposed to HIV-1 but do not exhibit clinical or serological evidence of infection, known as exposed seronegative individuals. Many studies have focused on the different mechanisms involved in natural resistance to HIV-1 infection, and have reported several factors associated with this phenomenon, including the presence of genetic polymorphisms in the viral coreceptors, innate and adaptive immune cells with particular phenotypic and functional features, and molecules such as antibodies and soluble factors that play an important role in defense against infection by HIV-1. The study of these factors could be the key for controlling this viral infection. This review summarizes the main mechanisms involved in resistance to HIV-1 infection.

Molecular definition of vaginal microbiota in East African commercial sex workers

Resistance to HIV infection in a cohort of commercial sex workers living in Nairobi, Kenya, is linked to mucosal and antiinflammatory factors that may be influenced by the vaginal microbiota. Since bacterial vaginosis (BV), a polymicrobial dysbiosis characterized by low levels of protective Lactobacillus organisms, is an established risk factor for HIV infection, we investigated whether vaginal microbiology was associated with HIV-exposed seronegative (HESN) or HIV-seropositive (HIV(+)) status in this cohort. A subset of 44 individuals was selected for deep-sequencing analysis based on the chaperonin 60 (cpn60) universal target (UT), including HESN individuals (n = 16), other HIV-seronegative controls (HIV-N, n = 16), and HIV(+) individuals (n = 12). Our findings indicate exceptionally high phylogenetic resolution of the cpn60 UT using reads as short as 200 bp, with 54 species in 29 genera detected in this group. Contrary to our initial hypothesis, few differences between HESN and HIV-N women were observed. Several HIV(+) women had distinct profiles dominated by Escherichia coli. The deep-sequencing phylogenetic profile of the vaginal microbiota corresponds closely to BV(+) and BV(-) diagnoses by microscopy, elucidating BV at the molecular level. A cluster of samples with intermediate abundance of Lactobacillus and dominant Gardnerella was identified, defining a distinct BV phenotype that may represent a transitional stage between BV(+) and BV(-). Several alpha- and betaproteobacteria, including the recently described species Variovorax paradoxus, were found to correlate positively with increased Lactobacillus levels that define the BV(-) ("normal") phenotype. We conclude that cpn60 UT is ideally suited to next-generation sequencing technologies for further investigation of microbial community dynamics and mucosal immunity underlying HIV resistance in this cohort.

Evidence for the innate immune response as a correlate of protection in human immunodeficiency virus (HIV)-1 highly exposed seronegative subjects (HESN)

The description of highly exposed individuals who remain seronegative (HESN) despite repeated exposure to human immunodeficiency virus (HIV)-1 has heightened interest in identifying potential mechanisms of HIV-1 resistance. HIV-specific humoral and T cell-mediated responses have been identified routinely in HESN subjects, although it remains unknown if these responses are a definitive cause of protection or merely a marker for exposure. Approximately half of HESN lack any detectible HIV-specific adaptive immune responses, suggesting that other mechanisms of protection from HIV-1 infection also probably exist. In support of the innate immune response as a mechanism of resistance, increased natural killer (NK) cell activity has been correlated with protection from infection in several high-risk cohorts of HESN subjects, including intravenous drug users, HIV-1 discordant couples and perinatally exposed infants. Inheritance of protective NK KIR3DL1(high) and KIR3DS1 receptor alleles have also been observed to be over-represented in a high-risk cohort of HESN intravenous drug users and HESN partners of HIV-1-infected subjects. Other intrinsic mechanisms of innate immune protection correlated with resistance in HESN subjects include heightened dendritic cell responses and increased secretion of anti-viral factors such as β-chemokines, small anti-viral factors and defensins. This review will highlight the most current evidence in HESN subjects supporting the role of epithelial microenvironment and the innate immune system in sustaining resistance against HIV-1 infection. We will argue that as a front-line defence the innate immune response determines the threshold of infectivity that HIV-1 must overcome to establish a productive infection.

Immune responses to HIV in the female reproductive tract, immunologic parallels with the gastrointestinal tract, and research implications

The female reproductive tract is a major site of mucosa-associated lymphoid tissue and susceptibility to HIV infection, yet the tissue site(s) of infection and the impact of HIV infection on this important mucosal tissue remain poorly understood. CD4(+) T cells and other cell types expressing the major coreceptors for HIV, CCR5, and CXCR4 are abundant in both the lower reproductive tract (endocervix and vagina) and the upper tract (endocervix and uterus) and are highly susceptible to infection. Antiviral defenses in the female reproductive tract are mediated by a variety of soluble factors and by mucosal effector cells that differ phenotypically from their counterparts in blood. The immunologic characteristics of the female reproductive tract parallel those of the gut, where major HIV-related immunologic injury occurs. The susceptibility of the female reproductive tract to HIV infection and immunopathogenesis suggests important new avenues for further research.

Female genital tract secretions and semen impact the development of microbicides for the prevention of HIV and other sexually transmitted infections

Pharmacologic strategies for the prevention of HIV include vaccines, post-exposure prophylaxis with antiretroviral therapy, and topical microbicides. Vaginal microbicides have the potential to augment innate defenses in the genital tract but may also disrupt endogenous protection and increase HIV acquisition risk, as observed in clinical trials of nonoxynol-9. The initially disappointing results of microbicide clinical trials stimulated the development of more sensitive and comprehensive pre-clinical safety studies, which include dual-chamber culture systems to model the epithelial barrier and post-coital studies to evaluate the effects of semen and sexual intercourse on microbicide efficacy. This review discusses the key factors that contribute to a healthy female genital tract environment, the impact of semen on mucosal defense, and how our understanding of these mediators informs the development of effective vaginal microbicides.

New approaches to making the microenvironment of the female reproductive tract hostile to HIV

The studies presented in this review explore three distinct areas with potential for inhibiting HIV infection in women. Based on emerging information from the physiology, endocrinology and immunology of the female reproductive tract (FRT), we propose unique 'works in progress' for protecting women from HIV. Various aspects of FRT immunity are suppressed by estradiol during the menstrual cycle, making women more susceptible to HIV infection. By engineering commensal Lactobacillus to secrete the anti-HIV molecule Elafin as estradiol levels increase, women could be protected from HIV infection. Selective estrogen response modifiers enhance barrier integrity and enhance secretion of protective anti-HIV molecules. Finally, understanding the interactions and regulation of FRT endogenous antimicrobials, proteases, antiproteases, etc., all of which are under hormonal control, will open new avenues to therapeutic manipulation of the FRT mucosal microenvironment. By seeking new alternatives to preventing HIV infection in women, we may finally disrupt the HIV pandemic.

Use of cervicovaginal fluid for the identification of biomarkers for pathologies of the female genital tract

Cervicovaginal fluid has an important function in the homeostasis and immunity of the lower female genital tract. Analysis of the cervicovaginal fluid proteome may therefore yield important information about the pathogenesis of numerous gynecological pathologies. Additionally, cervicovaginal fluid has great potential as a source of biomarkers for these conditions.

This review provides a detailed discussion about the human cervicovaginal proteome and the proteomics studies performed to characterize this biological fluid. Furthermore, infection-correlated pathological conditions of the female genital tract are discussed for which cervicovaginal fluid has been used in order to identify potential biomarkers. Recent years, numerous studies have analyzed cervicovaginal fluid samples utilizing antibody-based technologies, such as ELISA or Western blotting, to identify biomarkers for preterm birth, premature preterm rupture of membranes, bacterial vaginosis and cervical cancer. The present article will discuss the importance of proteomic technologies as alternative techniques to gain additional meaningful information about these conditions. In addition, the review focuses on recent proteomic studies on cervicovaginal fluid samples for the identification of potential biomarkers. We conclude that the use of proteomic technology for analysis of human cervicovaginal fluid samples is promising and may lead to the discovery of new biomarkers which can improve disease prevention and therapy development.

Microbiota restoration: natural and supplemented recovery of human microbial communities

In a healthy host, a balance exists between members of the microbiota, such that potential pathogenic and non-pathogenic organisms can be found in apparent harmony. During infection, this balance can become disturbed, leading to often dramatic changes in the composition of the microbiota. For most bacterial infections, nonspecific antibiotics are used, killing the non-pathogenic members of the microbiota as well as the pathogens and leading to a substantial delay in the restoration of a healthy microbiota. However, in some cases, infections can self-resolve without the intervention of antibiotics. In this Review, we explore the mechanisms underlying microbiota restoration following insult (antibiotic or otherwise) to the skin, oral cavity, and gastrointestinal and urogenital tracts, highlighting recovery by natural processes and after probiotic administration.

Innate immunity against HIV: a priority target for HIV prevention research

This review summarizes recent advances and current gaps in understanding of innate immunity to human immunodeficiency virus (HIV) infection, and identifies key scientific priorities to enable application of this knowledge to the development of novel prevention strategies (vaccines and microbicides). It builds on productive discussion and new data arising out of a workshop on innate immunity against HIV held at the European Commission in Brussels, together with recent observations from the literature.Increasing evidence suggests that innate responses are key determinants of the outcome of HIV infection, influencing critical events in the earliest stages of infection including the efficiency of mucosal HIV transmission, establishment of initial foci of infection and local virus replication/spread as well as virus dissemination, the ensuing acute burst of viral replication, and the persisting viral load established. They also impact on the subsequent level of ongoing viral replication and rate of disease progression. Modulation of innate immunity thus has the potential to constitute a powerful effector strategy to complement traditional approaches to HIV prophylaxis and therapy. Importantly, there is increasing evidence to suggest that many arms of the innate response play both protective and pathogenic roles in HIV infection. Consequently, understanding the contributions made by components of the host innate response to HIV acquisition/spread versus control is a critical pre-requisite for the employment of innate immunity in vaccine or microbicide design, so that appropriate responses can be targeted for up- or down-modulation. There is also an important need to understand the mechanisms via which innate responses are triggered and mediate their activity, and to define the structure-function relationships of individual innate factors, so that they can be selectively exploited or inhibited. Finally, strategies for achieving modulation of innate functions need to be developed and subjected to rigorous testing to ensure that they achieve the desired level of protection without stimulation of immunopathological effects. Priority areas are identified where there are opportunities to accelerate the translation of recent gains in understanding of innate immunity into the design of improved or novel vaccine and microbicide strategies against HIV infection.

Host proteome research in HIV infection

Proteomics has been widely used in the last few years to look for new biomarkers and decipher the mechanism of HIV–host interaction. Herein, we review the recent developments of HIV/AIDS proteomic research, including the samples used in HIV/AIDS related research, the technologies used for proteomic study, the diagnosis biomarkers of HIV-associated disease especially HIV-associated neurocognitive impairment, the mechanisms of HIV–host interaction, HIV-associated dementia, substance abuse, and so on. In the end of this review, we also give some prospects about the limitation and future improvement of HIV/AIDS proteomic research.

Systems biology-based approaches to understand HIV-exposed uninfected women

Worldwide HIV infects women more frequently than men, and it is clear that not all exposed to HIV become infected. Several populations of HIV-exposed uninfected (EU) women have been identified, including discordant couples and sex workers. Understanding what provides natural protection in EU women is critical in vaccine or microbicide development. However, correlates of protection in these women are still unclear. Most studies have used classical methods, examining single genes or cellular factors, a mainstay for traditional immunobiology. This reductionist approach may be limited in the information it can provide. Novel technologies are now available that allow us to take a "systems biology" approach, which allows the study of a complex biological system and identifies factors that may provide protection against HIV infection. Herein we report developments in discovery-based systems biology approaches in EU women and how this broadens our understanding of natural protection against HIV-1.

Anti-HIV activity in cervical-vaginal secretions from HIV-positive and -negative women correlate with innate antimicrobial levels and IgG antibodies

Background

We investigated the impact of antimicrobials in cervicovaginal lavage (CVL) from HIV(+) and HIV(−) women on target cell infection with HIV. Since female reproductive tract (FRT) secretions contain a spectrum of antimicrobials, we hypothesized that CVL from healthy HIV(+) and (−) women inhibit HIV infection.

Methodology/Principal Findings

CVL from 32 HIV(+) healthy women with high CD4 counts and 15 healthy HIV(−) women were collected by gently washing the cervicovaginal area with 10 ml of sterile normal saline. Following centrifugation, anti-HIV activity in CVL was determined by incubating CVL with HIV prior to addition to TZM-bl cells. Antimicrobials and anti-gp160 HIV IgG antibodies were measured by ELISA. When CXCR4 and CCR5 tropic HIV-1 were incubated with CVL from HIV(+) women prior to addition to TZM-bl cells, anti-HIV activity in CVL ranged from none to 100% inhibition depending on the viral strains used. CVL from HIV(−) controls showed comparable anti-HIV activity. Analysis of CH077.c (clone of an R5-tropic, mucosally-transmitted founder virus) viral inhibition by CVL was comparable to laboratory strains. Measurement of CVL for antimicrobials HBD2, trappin-2/elafin, SLPI and MIP3α indicated that each was present in CVL from HIV(+) and HIV(−) women. HBD2 and MIP3α correlated with anti-HIV activity as did anti-gp160 HIV IgG antibodies in CVL from HIV(+) women.

Conclusions/Significance

These findings indicate that CVL from healthy HIV(+) and HIV(−) women contain innate and adaptive defense mechanisms that inhibit HIV infection. Our data suggest that innate endogenous antimicrobials and HIV-specific IgG in the FRT can act in concert to contribute toward the anti-HIV activity of the CVL and may play a role in inhibition of HIV transmission to women.

Secretory leukocyte protease inhibitor and elafin/trappin-2: versatile mucosal antimicrobials and regulators of immunity

Elafin and secretory leukocyte protease inhibitor (SLPI) are pleiotropic molecules chiefly synthesized at the mucosal surface that have a fundamental role in the surveillance against microbial infections. Their initial discovery as anti-proteases present in the inflammatory milieu in chronic pathologies such as those of the lung suggested that they may play a role in keeping in check extracellular proteases released during the excessive activation of innate immune cells such as neutrophils. This soon proved to be a simplistic explanation, as other functions were also soon ascribed to these molecules (antimicrobial, modulation of innate and adaptive immunity, regulation of tissue repair). Data emanating from patients with chronic pathologies (in the lung and elsewhere) have shown that SLPI and elafin are often inactivated in inflammatory secretions, either through the action of host or microbial products, justifying attempts at antiprotease supplementation in clinical protocols. Although these have been sparse, proof of principle has been demonstrated, and future challenges will undoubtedly rest with improvements in methods of delivery in the context of tissue inflammation and in careful selection of patients more likely to benefit from SLPI/elafin augmentation.

HIV infection in the female genital tract: discrete influence of the local mucosal microenvironment

Women acquire HIV infections predominantly at the genital mucosa through heterosexual transmission. Therefore, the immune milieu at female genital surfaces is a critical determinant of HIV susceptibility. In this review, we recapitulate the evidence suggesting that several distinctive innate immune mechanisms in the female genital tract (FGT) serve to significantly deter or facilitate HIV-1 infection. Epithelial cells lining the FGT play a key role in forming a primary barrier to HIV entry. These cells express Toll-like receptors and other receptors that recognize and respond directly to pathogens, including HIV-1. In addition, innate biological factors produced by epithelial and other cells in the FGT have anti-HIV activity. Female sex hormones, co-infection with other pathogens and components in semen may also exacerbate or down-modulate HIV transmission. A combination of innate and adaptive immune factors and their interactions with the local microenvironment determine the outcome of HIV transmission. Improving our understanding of the female genital microenvironment will be useful in developing treatments that augment and sustain protective immune responses in the genital mucosa, such as microbicides and vaccines, and will provide greater insight into viral pathogenesis in the FGT.