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

Elafin and its precursor trappin-2: What is their therapeutic potential for intestinal diseases?

Elafin and its precursor trappin-2 are known for their contribution to the physiological mucosal shield against luminal microbes. Such a contribution seems to be particularly relevant in the gut, where the exposure of host tissues to heavy loads of microbes is constant and contributes to mucosa-associated pathologies. The expression of trappin-2/elafin has been shown to be differentially regulated in diseases associated with gut inflammation. Accumulating evidence has demonstrated the protective effects of trappin-2/elafin in gut intestinal disorders associated with acute or chronic inflammation, or with gluten sensitization disorders. The protective effects of trappin-2/elafin in the gut are discussed in terms of their pleiotropic modes of action: acting as protease inhibitors, transglutaminase substrates, antimicrobial peptides or as a regulator of pro-inflammatory transcription factors. Further, the question of the therapeutic potential of trappin-2/elafin delivery at the intestinal mucosa surface is raised. Whether trappin-2/elafin mucosal delivery should be considered to ensure intestinal tissue repair is also discussed.

The Penis, the Vagina and HIV Risk: Key Differences (Aside from the Obvious)

Globally, most Human Immunodeficiency Virus type 1 (HIV) transmission occurs through vaginal–penile sex (heterosexual transmission). The local immune environment at the site of HIV exposure is an important determinant of whether exposure during sex will lead to productive infection, and the vaginal and penile immune milieus are each critically shaped by the local microbiome. However, there are key differences in the microbial drivers of inflammation and immune quiescence at these tissue sites. In both, a high abundance of anaerobic taxa (e.g., Prevotella) is associated with an increased local density of HIV target cells and an increased risk of acquiring HIV through sex. However, the taxa that have been associated to date with increased risk in the vagina and penis are not identical. Just as importantly, the microbiota associated with comparatively less inflammation and HIV risk—i.e., the optimal microbiota—are very different at the two sites. In the vagina, Lactobacillus spp. are immunoregulatory and may protect against HIV acquisition, whereas on the penis, “skin type” flora such as Corynebacterium are associated with reduced inflammation. Compared to its vaginal counterpart, much less is known about the dynamics of the penile microbiome, the ability of clinical interventions to alter the penile microbiome, or the impact of natural/induced microbiome alterations on penile immunology and HIV risk.

Transglutaminase 2 as a Marker for Inflammation and Therapeutic Target in Sepsis

Sepsis results in lethal organ malfunction due to dysregulated host response to infection, which is a condition with increasing prevalence worldwide. Transglutaminase 2 (TG2) is a crosslinking enzyme that forms a covalent bond between lysine and glutamine. TG2 plays important roles in diverse cellular processes, including extracellular matrix stabilization, cytoskeletal function, cell motility, adhesion, signal transduction, apoptosis, and cell survival. We have shown that the co-culture of Candida albicans and hepatocytes activates and induces the translocation of TG2 into the nucleus. In addition, the expression and activation of TG2 in liver macrophages was dramatically induced in the lipopolysaccharide-injected and cecal ligation puncture-operated mouse models of sepsis. Based on these findings and recently published research, we have reviewed the current understanding of the relationship between TG2 and sepsis. Following the genetic and pharmacological inhibition of TG2, we also assessed the evidence regarding the use of TG2 as a potential marker and therapeutic target in inflammation and sepsis.

A Caulobacter crescentus Microbicide Protects from Vaginal Infection with HIV-1JR-CSF in Humanized Bone Marrow-Liver-Thymus Mice

Human immunodeficiency virus (HIV) disproportionally infects young women in sub-Saharan Africa. Current HIV-1 prevention options have had limited success among women, suggesting that alternative, female-controlled prevention options need to be developed. Microbicides that can be applied to the vaginal tract are a promising prevention option. In this study, we describe the testing of 15 potential candidates for inhibition of HIV-1 infection in a humanized mouse model of HIV-1 infection. Four of these candidates were able to provide significant protection from vaginal infection with HIV-1, with the most successful candidate protecting 75% of the mice from infection. This study describes the preclinical testing of a new strategy that could be a safe and effective option for HIV-1 prevention in women.

Over 2 million people are infected with HIV-1 annually. Approximately half of these new infections occur in women residing in low-income countries, where their access to and control over HIV-1 preventative measures are often limited, indicating that female-controlled prevention options for HIV-1 are urgently needed. Microbicides that can be topically applied to the vaginal tract in advance of sexual activity represent a promising female-controlled prevention option for HIV-1. We have previously described the development of an HIV-1-specific microbicide using the surface or S-layer recombinant protein display capabilities of the nonpathogenic, freshwater bacterium Caulobacter crescentus. Recombinant C. crescentus bacteria were created that displayed proteins that interfere with the HIV-1 attachment and entry process and that were able to provide significant protection of TZM-bl cells from infection with HIV-1 pseudovirus. These studies have been expanded to investigate if these recombinant C. crescentus bacteria are able to maintain efficacy with replication-competent HIV-1 and both TZM-bl cells and human peripheral blood mononuclear cells (PBMCs). In addition, we utilized the humanized bone marrow-liver-thymus (BLT) mouse model to determine if vaginal application of recombinant C. crescentus at the time of HIV-1_JR-CSF infection could provide protection from HIV-1 infection. Recombinant C. crescentus bacteria expressing Griffithsin, GB virus C E2 protein, elafin, α-1-antitrypsin, indolicidin, and the fusion inhibitor T-1249 were able to protect 40 to 75% of the BLT mice from vaginal infection with HIV-1_JR-CSF, with C. crescentus bacteria expressing Griffithsin being the most effective. Taken together, these data suggest that a C. crescentus-based microbicide could be a safe and effective method for HIV-1 prevention.

IMPORTANCE Human immunodeficiency virus (HIV) disproportionally infects young women in sub-Saharan Africa. Current HIV-1 prevention options have had limited success among women, suggesting that alternative, female-controlled prevention options need to be developed. Microbicides that can be applied to the vaginal tract are a promising prevention option. In this study, we describe the testing of 15 potential candidates for inhibition of HIV-1 infection in a humanized mouse model of HIV-1 infection. Four of these candidates were able to provide significant protection from vaginal infection with HIV-1, with the most successful candidate protecting 75% of the mice from infection. This study describes the preclinical testing of a new strategy that could be a safe and effective option for HIV-1 prevention in women.

A High-throughput Bead-based Affinity Assay Enables Analysis of Genital Protein Signatures in Women At Risk of HIV Infection

Women at high risk of HIV infection, including sex workers and those with active genital inflammation, have molecular signatures of immune activation and epithelial barrier remodeling in samples of their genital mucosa. These alterations in the local immunological milieu are likely to impact HIV susceptibility. We here analyze host genital protein signatures in HIV uninfected women, with high frequency of condom use, living in HIV-serodiscordant relationships. Cervicovaginal secretions from women living in HIV-serodiscordant relationships (n = 62) were collected at three time points over 12 months. Women living in HIV-negative seroconcordant relationships (controls, n = 25) were sampled at one time point. All study subjects were examined for demographic parameters associated with susceptibility to HIV infection. The cervicovaginal samples were analyzed using a high-throughput bead-based affinity assay. Proteins involved in epithelial barrier function and inflammation were increased in HIV-serodiscordant women. By combining several methods of analysis, a total of five proteins (CAPG, KLK10, SPRR3, elafin/PI3, CSTB) were consistently associated with this study group. Proteins analyzed using the affinity set-up were further validated by label-free tandem mass spectrometry in a partially overlapping cohort with concordant results. Women living in HIV-serodiscordant relationships thus had elevated levels of proteins involved in epithelial barrier function and inflammation despite low prevalence of sexually transmitted infections and a high frequency of safe sex practices. The identified proteins are important markers to follow during assessment of mucosal HIV susceptibility factors and a high-throughput bead-based affinity set-up could be a suitable method for such evaluation.

Poly (I:C) and LPS induce distinct immune responses by ovarian stromal fibroblasts

Despite its anatomical location, the ovary is a site of pathogen exposure in the human female reproductive tract (FRT). However, the role of ovarian stromal fibroblasts in immune protection is unclear. We generated a population of ovarian stromal fibroblasts derived from normal human ovaries that expressed the pattern recognition receptors TLR3, TLR4, RIG-I, & MDA5. Poly (I:C) and LPS, respective mimics of viral and bacterial infections, selectively upregulated antiviral gene expression and secretion of chemokines and antimicrobials. Poly (I:C) exclusively stimulated the expression of interferon (IFN) β, IFNλ1, and the IFN-stimulated gene OAS2. Poly (I:C) also significantly increased secretion of elafin, CCL20, and RANTES, but had no effect on SDF-1α. In contrast, LPS had no effect on IFN or ISG expression but significantly increased secretion of RANTES and SDF-1α. Secretions from poly (I:C)-treated fibroblasts had both greater anti-HIV activity and induced higher levels of CD4 + T cell chemotaxis than those from LPS-treated cells. Our studies demonstrate a potential key role for ovarian fibroblasts in innate immune protection against incoming pathogens in the normal ovary.

Generation of a Dual-Target, Safe, Inexpensive Microbicide that Protects Against HIV-1 and HSV-2 Disease

HSV-2 infection is a significant health problem and a major co-morbidity factor for HIV-1 acquisition, increasing risk of infection 2-4 fold. Condom based prevention strategies for HSV-2 and HIV-1 have not been effective at stopping the HIV-1 pandemic, indicating that alternative prevention strategies need to be investigated. We have previously developed an inexpensive HIV-1 specific microbicide that utilizes the S-layer mediated display capabilities of Caulobacter crescentus, and have shown that recombinant C. crescentus displaying HIV entry blocking proteins are able to provide significant protection from HIV-1 infection in vitro. Here we demonstrate that recombinant C. crescentus are safe for topical application and describe 5 new recombinant C. crescentus that provide protection from HIV-1 infection in vitro. Further, we demonstrate protection from disease following intravaginal infection with HSV-2 in a murine model using C. crescentus expressing the anti-viral lectins Cyanovirin-N and Griffithsin, as well as α-1-antitrypsin and indolicidin. Interestingly, C. crescentus alone significantly reduced HSV-2 replication in vaginal lavage fluid. Protection from HSV-2 disease was strongly associated with early cytokine production in the vaginal tract. Our data support the potential for a dual-target microbicide that can protect against both HIV-1 and HSV-2, which could have an enormous impact on public health.

Breastfeeding Behaviors and the Innate Immune System of Human Milk: Working Together to Protect Infants against Inflammation, HIV-1, and Other Infections

The majority of infants’ breastfeeding from their HIV-infected mothers do not acquire HIV-1 infection despite exposure to cell-free virus and cell-associated virus in HIV-infected breast milk. Paradoxically, exclusive breastfeeding regardless of the HIV status of the mother has led to a significant decrease in mother-to-child transmission (MTCT) compared with non-exclusive breastfeeding. Although it remains unclear how these HIV-exposed infants remain uninfected despite repeated and prolonged exposure to HIV-1, the low rate of transmission is suggestive of a multitude of protective, short-lived bioactive innate immune factors in breast milk. Indeed, recent studies of soluble factors in breast milk shed new light on mechanisms of neonatal HIV-1 protection. This review highlights the role and significance of innate immune factors in HIV-1 susceptibility and infection. Prevention of MTCT of HIV-1 is likely due to multiple factors, including innate immune factors such as lactoferrin and elafin among many others. In pursuing this field, our lab was the first to show that soluble toll-like receptor 2 (sTLR2) directly inhibits HIV infection, integration, and inflammation. More recently, we demonstrated that sTLR2 directly binds to selective HIV-1 proteins, including p17, gp41, and p24, leading to significantly reduced NFκB activation, interleukin-8 production, CCR5 expression, and HIV infection in a dose-dependent manner. Thus, a clearer understanding of soluble milk-derived innate factors with known antiviral functions may provide new therapeutic insights to reduce vertical HIV-1 transmission and will have important implications for protection against HIV-1 infection at other mucosal sites. Furthermore, innate bioactive factors identified in human milk may serve not only in protecting infants against infections and inflammation but also the elderly; thus, opening the door for novel innate immune therapeutics to protect newborns, infants, adults, and the elderly.

Precursor Forms of Vitamin D Reduce HIV-1 Infection In Vitro

BACKGROUND

Although the anti-HIV-1 effects of vitamin D (VitD) have been reported, mechanisms behind such protection remain largely unexplored.

METHODS

The effects of two precursor forms (cholecalciferol/calciol at 0.01, 1 and 100 nM and calcidiol at 100 and 250 nM) on HIV-1 infection, immune activation, and gene expression were analyzed in vitro in cells of Colombian and Italian healthy donors. We quantified levels of released p24 by enzyme-linked immunosorbent assay, of intracellular p24 and cell-surface expression of CD38 and HLA-DR by flow cytometry, and mRNA expression of antiviral and immunoregulatory genes by real-time reverse transcription-polymerase chain reaction.

RESULTS

Cholecalciferol decreased the frequency of HIV-1-infected p24CD4 T cells and levels of p24 in supernatants in a dose-dependent manner. Moreover, the CD4CD38HLA-DR and CD4CD38HLA-DR subpopulations were more susceptible to infection but displayed the greatest cholecalciferol-induced decreases in infection rate by an X4-tropic strain. Likewise, cholecalciferol at its highest concentration decreased the frequency of CD38HLA-DR but not of CD38HLA-DR T-cell subsets. Analyzing the effects of calcidiol, the main VitD source for immune cells and an R5-tropic strain as the most frequently transmitted virus, a reduction in HIV-1 productive infection was also observed. In addition, an increase in mRNA expression of APOBEC3G and PI3 and a reduction of TRIM22 and CCR5 expression, this latter positively correlated with p24 levels, was noted.

CONCLUSIONS

VitD reduces HIV-1 infection in T cells possibly by inducing antiviral gene expression, reducing the viral co-receptor CCR5 and, at least at the highest cholecalciferol concentration, by promoting an HIV-1-restrictive CD38HLA-DR immunophenotype.

HIV-Enhancing Factors Are Secreted by Reproductive Epithelia upon Inoculation with Bacterial Vaginosis-Associated Bacteria

Bacterial vaginosis is a common reproductive infection in which commensal vaginal lactobacilli are displaced by a mixed population of pathogenic bacteria. Bacterial vaginosis increases susceptibility to HIV, and it has been suggested that host innate immune responses to pathogenic bacteria contribute to enhanced infection, yet the cellular mechanisms mediating the increased HIV susceptibility remain uncharacterized. We evaluated the HIV-enhancing effects of bacterial vaginosis by inoculating endocervical epithelia with Atopobium vaginae, a bacterial vaginosis-associated bacteria, and assaying secreted factors for HIV-enhancing activity. When epithelia and A. vaginae were cocultured, we observed increased HIV-enhancing activity mediated by secreted low molecular weight factors. From this complex mixture we identified several upregulated host proteins, which functioned in combination to enhance HIV infection. These studies suggest that the host immune response to bacterial vaginosis-associated bacteria results in the release of HIV-enhancing factors. The combined activity of bacterial vaginosis-induced proteins likely mediates HIV enhancement.

HIV-1 Structural Proteins Serve as PAMPs for TLR2 Heterodimers Significantly Increasing Infection and Innate Immune Activation

Immune activation is critical to HIV infection and pathogenesis; however, our understanding of HIV innate immune activation remains incomplete. Recently we demonstrated that soluble TLR2 (sTLR2) physically inhibited HIV-induced NFκB activation and inflammation, as well as HIV-1 infection. In light of these findings, we hypothesized that HIV-1 structural proteins may serve as pathogen-associated molecular patterns (PAMPs) for cellular TLR2 heterodimers. These studies made use of primary human T cells and TZMbl cells stably transformed to express TLR2 (TZMbl-2). Our results demonstrated that cells expressing TLR2 showed significantly increased proviral DNA compared to cells lacking TLR2, and mechanistically this may be due to a TLR2-mediated increased CCR5 expression. Importantly, we show that HIV-1 structural proteins, p17, p24, and gp41, act as viral PAMPs signaling through TLR2 and its heterodimers leading to significantly increased immune activation via the NFκB signaling pathway. Using co-immunoprecipitation and a dot blot method, we demonstrated direct protein interactions between these viral PAMPs and TLR2, while only p17 and gp41 bound to TLR1. Specifically, TLR2/1 heterodimer recognized p17 and gp41, while p24 lead to immune activation through TLR2/6. These results were confirmed using TLR2/1 siRNA knock down assays which ablated p17 and gp41-induced cellular activation and through studies of HEK293 cells expressing selected TLRs. Interestingly, our results show in the absence of TLR6, p24 bound to TLR2 and blocked p17 and gp41-induced activation, thus providing a novel mechanism by which HIV-1 can manipulate innate sensing. Taken together, our results identified, for the first time, novel HIV-1 PAMPs that play a role in TLR2-mediated cellular activation and increased proviral DNA. These findings have important implications for our fundamental understanding of HIV-1 immune activation and pathogenesis, as well as HIV-1 vaccine development.

High Expression of Antiviral Proteins in Mucosa from Individuals Exhibiting Resistance to Human Immunodeficiency Virus

BACKGROUND

Several soluble factors have been reported to have the capacity of inhibiting HIV replication at different steps of the virus life cycle, without eliminating infected cells and through enhancement of specific cellular mechanisms. Yet, it is unclear if these antiviral factors play a role in the protection from HIV infection or in the control of viral replication. Here we evaluated two cohorts: i) one of 58 HIV-exposed seronegative individuals (HESNs) who were compared with 59 healthy controls (HCs), and ii) another of 13 HIV-controllers who were compared with 20 HIV-progressors. Peripheral blood, oral and genital mucosa and gut-associated lymphoid tissue (GALT) samples were obtained to analyze the mRNA expression of ELAFIN, APOBEC3G, SAMHD1, TRIM5α, RNase 7 and SerpinA1 using real-time PCR.

RESULTS

HESNs exhibited higher expression of all antiviral factors in peripheral blood mononuclear cells (PBMCs), oral or genital mucosa when compared with HCs. Furthermore, HIV-controllers exhibited higher levels of SerpinA1 in GALT.

CONCLUSIONS

These findings suggest that the activity of these factors is compartmentalized and that these proteins have a predominant role depending on the tissue to avoid the infection, reduce the viral load and modulate the susceptibility to HIV infection.

Cross-Sectional Analysis of Selected Genital Tract Immunological Markers and Molecular Vaginal Microbiota in Sub-Saharan African Women, with Relevance to HIV Risk and Prevention

Data on immune mediators in the genital tract and the factors that modulate them in sub-Saharan women are limited. Cervicovaginal lavage (CVL) samples from 430 sexually active women from Kenya, South Africa, and Rwanda were analyzed for 12 soluble immune mediators using Bio-Plex and Meso Scale Discovery multiplex platforms, as well as single enzyme-linked immunosorbent assays. Ten bacterial species were quantified in vaginal swab samples. Bacterial vaginosis (BV) was defined by Nugent scoring. CVL samples from HIV-infected women showed a clear-cut proinflammatory profile. Pregnant women, adolescents, and women engaging in traditional vaginal practices differed in specific soluble markers compared to reference groups of adult HIV-negative women. Cervical mucus, cervical ectopy, abnormal vaginal discharge, and having multiple sex partners were each associated with an increase in inflammatory mediators. The levels of interleukin-1α (IL-1α), IL-1β, IL-6, IL-12(p70), and IL-8 were elevated, whereas the IL-1RA/IL-1(α+β) ratio decreased in women with BV. The level of gamma interferon-induced protein 10 was lower in BV-positive than in BV-negative women, suggesting its suppression as a potential immune evasion mechanism by BV-associated bacteria. Lactobacillus crispatus and Lactobacillus vaginalis were associated with decreased proinflammatory cytokines and each BV-associated species with increased proinflammatory cytokines. Remarkably, the in vitro anti-HIV activity of CVL samples from BV-positive women was stronger than that of BV-negative women. In conclusion, we found significant associations of factors, including vaginal microbiota, which can influence immune mediators in the vaginal environment in sexually active women. These factors need to be considered when establishing normative levels or pathogenic cutoffs of biomarkers of inflammation and associated risks in African women.

Innate immunity in the vagina (Part II): Anti-HIV activity and antiviral content of human vaginal secretions

PROBLEM

Whether the concentrations of antiviral proteins, and anti-HIV activity, within human vaginal secretions change across the menstrual cycle is unknown.

METHOD OF STUDY

Using a menstrual cup, vaginal secretions from pre-menopausal women were recovered at the proliferative (d6-8), mid-cycle (d13-15), and secretory (d21-23) stages of the menstrual cycle. Antiviral protein concentration was determined by ELISA, and anti-HIV activity assessed using the TZM-bl reporter cell line.

RESULTS

CCL20, RANTES, elafin, HBD2, SDF-1α, and IL-8 levels were detectable in the secretions. Vaginal secretions had anti-HIV activity against specific clade B strains of HIV, with significant inhibition of IIIB and increased infectivity of transmitted/founder CH077.t. No significant differences in either antiviral protein concentration or anti-HIV activity with respect to menstrual cycle stage were measured, but marked differences were observed in both parameters over the course of the cycle between different women and in consecutive cycles from the same woman.

CONCLUSION

The vagina contains a complement of antiviral proteins. The variation in anti-HIV activity demonstrates that immune protection in the vagina is not constant. Intra- and interindividual variations suggest that factors in addition to sex hormones influence antiviral protection. Lastly, the menstrual cup is a new model for recovering undiluted vaginal secretions from women throughout their reproductive life.

Increased Serpin A5 levels in the cervicovaginal fluid of HIV-1 exposed seronegatives suggest that a subtle balance between serine proteases and their inhibitors may determine susceptibility to HIV-1 infection

HIV-exposed seronegative individuals (HESNs) are persons who remain seronegative despite repeated exposure to HIV, suggesting an in vivo resistance mechanism to HIV. Elucidation of endogenous factors responsible for this phenomenon may aid in the development of new classes of microbicides and therapeutics. We compared cervicovaginal protein abundance profiles between high-risk HESN and two control groups: low-risk HESN and HIV-positives. Four iTRAQ-based quantitative experiments were performed using samples classified based on presence/absence of particular gynaecological conditions. After statistical analysis, two proteins were shown to be differentially abundant between high-risk HESNs and control groups. Serpin A5, a serine proteinase inhibitor and Myeloblastin, a serine protease, were up- and downregulated, respectively. Commercially available ELISA assays were used to confirm differential Serpin A5 levels. These results suggest that HIV resistance in CVF of HESNs is the result of a delicate balance between two complementary mechanisms: downregulation of serine proteinases and upregulation of their inhibitors.

Acting locally: innate mucosal immunity in resistance to HIV-1 infection in Kenyan commercial sex workers

Cohort studies of female commercial sex workers (CSWs) in Kenya were among the first to identify highly HIV-1-exposed seronegative (HESN) individuals. As natural resistance is usually mediated by innate immune mechanisms, we focused on determining whether expression and function of innate signaling pathways were altered locally in the genital mucosa of HESN CSWs. Our results demonstrated that selected pattern-recognition receptors (PRRs) were significantly reduced in expression in cervical mononuclear cells (CMCs) from HESN compared with the new HIV-negative (HIV-N) and HIV-positive (HIV-P) groups. Although baseline levels of secreted cytokines were reduced in CMCs of HESN, they were highly stimulated following exposure to ssRNA40 in vitro. Importantly, cervical epithelial cells from HESN also expressed reduced levels of PRRs, but Toll-like receptor 3 (TLR3) and TLR7 as well as nuclear factor-κB and activator protein 1 were highly expressed and activated. Lastly, inflammatory cytokines interleukin (IL)-1β, IL-8, and RANTES (regulated and normal T cell expressed and secreted) were detected at lower levels in cervicovaginal lavage of HESN compared with the HIV-N and HIV-P groups. Overall, our study reveals a local microenvironment of HIV resistance in the genital mucosa consisting of a finely controlled balance of basal immune quiescence with a focused and potent innate anti-viral response critical to resistance to sexual transmission of HIV-1.

Antiviral activity of trappin-2 and elafin in vitro and in vivo against genital herpes

Serine protease inhibitor elafin (E) and its precursor, trappin-2 (Tr), have been associated with mucosal resistance to HIV-1 infection. We recently showed that Tr/E are among principal anti-HIV-1 molecules in cervicovaginal lavage (CVL) fluid, that E is ∼130 times more potent than Tr against HIV-1, and that Tr/E inhibited HIV-1 attachment and transcytosis across human genital epithelial cells (ECs). Since herpes simplex virus 2 (HSV-2) is a major sexually transmitted infection and risk factor for HIV-1 infection and transmission, we assessed Tr/E contribution to defense against HSV-2. Our in vitro studies demonstrated that pretreatment of endometrial (HEC-1A) and endocervical (End1/E6E7) ECs with human Tr-expressing adenovirus (Ad/Tr) or recombinant Tr/E proteins before or after HSV-2 infection resulted in significantly reduced virus titers compared to those of controls. Interestingly, E was ∼7 times more potent against HSV-2 infection than Tr. Conversely, knockdown of endogenous Tr/E by small interfering RNA (siRNA) significantly increased HSV-2 replication in genital ECs. Recombinant Tr and E reduced viral attachment to genital ECs by acting indirectly on cells. Further, lower viral replication was associated with reduced secretion of proinflammatory interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-α) and decreased NF-κB nuclear translocation. Additionally, protected Ad/Tr-treated ECs demonstrated enhanced interferon regulatory factor 3 (IRF3) nuclear translocation and increased antiviral IFN-β in response to HSV-2. Lastly, in vivo studies of intravaginal HSV-2 infection in Tr-transgenic mice (Etg) showed that despite similar virus replication in the genital tract, Etg mice had reduced viral load and TNF-α in the central nervous system compared to controls. Collectively, this is the first experimental evidence highlighting anti-HSV-2 activity of Tr/E in female genital mucosa.

Human rElafin Inhibits HIV-1 Replication in Its Natural Target Cells

Trappin-2/elafin is a novel innate immune factor that belongs to the serine protease inhibitor family and has known antibacterial, antifungal, and antiviral properties. In this study, we further investigated the anti-HIV activity of elafin using different cellular models and both X4– and R5–HIV-1 laboratory strains. We compared the antiviral activity of human recombinant elafin (rElafin) with three well-known antiretroviral drugs, AZT, tenofovir, and enfuvirtide. We have found that when the virus is pre-incubated with rElafin prior to the infection of the cells, HIV-1 replication is significantly inhibited. In target T cells and human peripheral blood mononuclear cells, maximal inhibition was achieved using submicromolar concentrations, and rElafin was found to be as potent as enfuvirtide, showing its potential for therapeutic application. We also show data on the mechanism of the antiviral activity of rElafin. We have demonstrated that rElafin neither binds to CD4, CXCR4, or CCR5 host cell receptors, nor to the viral glycoproteins gp120 and gp41. Furthermore, in our cell-to-cell fusion assays, in contrast to enfuvirtide, rElafin failed to block cell fusion. Altogether our results indicate that rElafin interferes with HIV replication at the early steps of its cycle but with a different mechanism of action than enfuvirtide. This study provides the first experimental evidence that elafin inhibits HIV replication in its natural target cells; therefore, elafin might have potential for its development as a new anti-HIV drug or microbicide.

Anti-HIV-1 activity of elafin depends on its nuclear localization and altered innate immune activation in female genital epithelial cells

Elafin (E) and its precursor trappin-2 (Tr) are alarm antiproteases with antimicrobial and immunomodulatory activities. Tr and E (Tr/E) have been associated with HIV-1 resistance. We recently showed that Tr/E reduced IL-8 secretion and NF-κB activation in response to a mimic of viral dsRNA and contributed to anti-HIV activity of cervicovaginal lavage fluid (CVL) of HIV-resistant (HIV-R) commercial sex workers (CSWs). Additionally, Tr, and more so E, were found to inhibit attachment/entry and transcytosis of HIV-1 in human endometrial HEC-1A cells, acting through virus or cells. Given their immunomodulatory activity, we hypothesized that Tr/E could exert anti-HIV-1 activity at multiple levels. Here, using tagged and untagged Tr/E proteins, we comparatively evaluated their protease inhibitory, anti-HIV-1, and immunomodulatory activities, and cellular distribution. E appeared to function as an autocrine/paracrine factor in HEC-1A cells, and anti-HIV-1 activity of E depended on its unmodified N-terminus and altered cellular innate activation, but not its antiprotease activity. Specifically, exogenously added N-terminus-unmodified E was able to enter the nucleus and to reduce viral attachment/entry and transcytosis, preferentially affecting R5-HIV-1(ADA), but not X4-HIV-1(IIIB). Further, anti-HIV-1 activity of E was associated with significantly decreased HIV-1-triggered IL-8 release, attenuated NF-κB/p65 nuclear translocation, and significantly modulated mRNA expression of innate sensors TLR3 and RIG-I in HEC-1A cells. Most importantly, we found that elevated Tr/E in CVLs of HIV-R CSWs were associated with lower mRNA levels of TLRs 2, 3, 4 and RIG-I in the genital ECs from this cohort, suggesting a link between Tr/E, HIV-1 resistance and modulated innate viral recognition in the female genital mucosa. Collectively, our data indicate that unmodified N-terminus is critical for intranuclear localization and anti-HIV-1 activity of E. We also propose that E-mediated altered cellular innate activation most likely contributes to the HIV-R phenotype of these subjects.

Natural Immunity to HIV: a delicate balance between strength and control

Understanding how the mucosal immune system in the human female reproductive tract might prevent or facilitate HIV infection has important implications for the design of effective interventions. We and others have established cohorts of highly-exposed, HIV-seronegative individuals, such as HIV-uninfected commercial sex workers, who have remained HIV-negative after more than 5 years of active prostitution. Observations obtained in studies of such individuals, who represent a model of natural immunity to HIV, indicate that HIV resistance may be associated with the host's capacity to preserve systemic integrity by constraining immune activity and controlling inflammatory conditions at the mucosal point of entry. This likely necessitates the orchestration of balanced, first-line and adaptive immune responses.

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.