Lifetime sexual violence exposure in women compromises systemic innate immune mediators associated with HIV pathogenesis: A cross-sectional analysis.

OBJECTIVES: Violence and HIV/AIDS syndemic highly prevalent among women impairs HIV prevention efforts. Prolonged exposure to violence results in physical trauma and psychological distress. Building on previous findings regarding genital immune dysregulation following sexual abuse exposure, we investigate here whether systemic changes occur as well. METHODS: Using the Women's Interagency HIV Study repository, 77 women were stratified by HIV serostatus and categorized into four subgroups: (1) no sexual abuse history and lower depression score (Control); (2) no sexual abuse history but higher depression score (Depression); (3) high sexual abuse exposure and lower depression score (Abuse); (4) high sexual abuse exposure and higher depression score (Abuse + Depression). Inflammation-associated immune biomarkers (TNF-α, IL-6, IL-1α, IL-1ß, TGF-ß, MIP-3α, IP-10, MCP-1, and Cathepsin-B) and anti-inflammatory/anti-HIV biomarkers (Secretory leukocyte protease inhibitor, Elafin, human beta-defensin-2 (HBD-2), alpha-defensins 1-3, Thrombospondin, Serpin-A1, and Cystatin-C) were measured in plasma using enzyme-linked immunosorbent assay. Within each HIV serostatus, differences in biomarker levels between subgroups were evaluated with Kruskal-Wallis and Dunn's test with Bonferroni correction. Spearman correlations between biomarkers were assessed for each subgroup. RESULTS: Compared to the Control and Depression groups, Abuse + Depression was associated with significantly higher levels of chemokines MIP-3α and IP-10 (p < 0.01) and lower levels of inflammatory cytokine IL-1ß (p < 0.01) in the HIV-uninfected population. Human beta-defensin-2 was lowest in the Abuse + Depression group (p < 0.05 versus Depression). By contrast, among HIV-infected, Abuse and Abuse + Depression were associated with lower levels of MIP-3α (p < 0.05 versus Control) and IP-10 (p < 0.05, Abuse versus Control). Inflammatory cytokine IL-6 was higher in both Abuse groups (p < 0.05 versus Control), while Elafin was lowest in the Abuse + Depression group (p < 0.01 versus Depression). CONCLUSION: We report compromised plasma immune responses that parallel previous findings in the genital mucosa, based on sexual abuse and HIV status. Systemic biomarkers may indicate trauma exposure and impact risk of HIV acquisition/transmission.

Evaluation of Elafin Immunohistochemical Expression as Marker of Cervical Cancer Severity.

INTRODUCTION: The main risk factor for the development of cervical cancer (CC) is persistent infection by human papillomavirus (HPV) oncogenic types. In order to persist, HPV exhibits a plethora of immune evasion mechanisms. PI3/Elafin (Peptidase Inhibitor 3) is an endogenous serine protease inhibitor involved in epithelial protection against pathogens. PI3/Elafin's role in CC is still poorly understood. MATERIALS AND METHODS: In the present study, we addressed PI3/Elafin protein detection in 123 CC samples by immunohistochemistry and mRNA expression in several datasets available at Gene Expression Omnibus and The Cancer Genome Atlas platforms. RESULTS: We observed that PI3/Elafin is consistently downregulated in CC samples when compared to normal tissue. Most of PI3/Elafin-positive samples exhibited this protein at the plasma membrane. Besides, high PI3/Elafin expression at the cellular membrane was more frequent in in situ stages I + II than in invasive cervical tumor stages III + IV. This indicates that PI3/Elafin expression is gradually lost during the CC progression. Of note, advanced stages of CC were more frequently associated with a more intense PI3/Elafin reaction in the nuclei and cytoplasm. CONCLUSION: Our results suggest that PI3/Elafin levels and subcellular localization may be used as a biomarker for CC severity.

Cervicovaginal natural antimicrobial expression in pregnancy and association with spontaneous preterm birth.

There is much interest in the role of innate immune system proteins (antimicrobial peptides) in the inflammatory process associated with spontaneous preterm birth (sPTB). After promising pilot work, we aimed to validate the association between the antimicrobial peptides/proteins elafin and cathelicidin and sPTB. An observational cohort study of 405 women at high-risk, and 214 women at low-risk of sPTB. Protein concentrations of elafin and cathelicidin, and the enzyme human neutrophil elastase (HNE) were measured in over 1,000 cervicovaginal fluid (CVF) samples (10 to 24 weeks' gestation). Adjusted CVF cathelicidin and HNE concentrations (but not elafin) were raised in high-risk women who developed cervical shortening and who delivered prematurely and were predictive of sPTB < 37 weeks, with an area under the curve (AUC) of 0.75 (95% CI 0.68 to 0.81) for cathelicidin concentration at 14 to 15+6 weeks. Elafin concentrations were affected by gestation, body mass index and smoking. CVF elafin in early pregnancy was modestly predictive of sPTB < 34 weeks (AUC 0.63, 0.56-0.70). Alterations in innate immune response proteins in early pregnancy are predictive of sPTB. Further investigation is warranted to understand the drivers for this, and their potential to contribute towards clinically useful prediction techniques.

Upregulation of elafin expression in the fallopian tube of ectopic tubal pregnancies compared to the normal tubes.

BACKGROUND: Ectopic pregnancy is one of the most important causes of maternal deaths and fallopian tubes are the location of 95% of ectopic pregnancies. Elafin is a natural antimicrobial molecule that plays an important role as an anti-inflammatory agent in mucosal surfaces and has been found in the female reproductive tract. OBJECTIVES: The aim of this study was to investigate elafin expression, in the fallopian tube mucosa of ectopic pregnancies compared to the normal tubes using immunohistochemistry (IHC) techniques and quantitative reverse transcription (qRT)-PCR. METHODS: In this case-control study, uterine tube samples were obtained from patients with an indication for surgical removal of the tubes. The case group (n = 20) consisted of patients who were undergoing salpingectomy due to an ectopic pregnancy, the control group (n = 20) included patients who had a salpingectomy and hysterectomy. Using qRT-PCR and IHC, the expression of elafin was investigated in both study groups. RESULTS: Immunohistochemical expression of elafin in the epithelium and connective tissue was significantly increased in the implantation site of the patients in comparison with the control group (P < 0.001). The level of elafin mRNA increased in the mucous membrane of the fallopian tube from patients with the ectopic pregnancy compared to the normal mucosa (P < 0.001). CONCLUSION: Increasing expression of elafin during an ectopic pregnancy may be a mechanism for enhancing innate immune response and be involved in related pathological conditions such as infection and ectopic implantation.

Dysregulation in Genital Tract Soluble Immune Mediators in Postmenopausal Women Is Distinct by HIV Status.

A rise in new HIV diagnoses among older adults is characterized by poor prognosis and reduced survival times. Although heterosexual transmission remains the main route of infection in women, little is known regarding immune functions in the genital tract of postmenopausal women, especially those who are HIV positive. Furthermore, effects of hormone replacement therapy (HRT) on the genital tract immune system are unclear. Using the Women's Interagency HIV Study repository, we obtained cervical-vaginal lavage (CVL) samples from premenopausal and postmenopausal HIV-positive and HIV-negative women, some of whom were on HRT. Samples were assayed for interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, secretory leukocyte protease inhibitor (SLPI), Elafin, human beta defensin-2 (HBD2), and macrophage inflammatory protein (MIP)-3α using ELISA. Anti-HIV activity in CVL was measured using TZM-bl indicator cells. Among HIV-positive women, the plasma viral load was significantly higher and CD4 count was significantly lower in postmenopausal compared with premenopausal women. Postmenopausal women, irrespective of HIV status, had significantly lower levels of HBD2 compared with premenopausal women. Among the HIV-negative individuals, postmenopausal women had significantly lower levels of MIP-3α, IL-6, and SLPI compared with premenopausal women. In contrast, HIV-positive postmenopausal women had significantly higher levels of TNF-α compared with HIV-positive premenopausal women. In most cases, HRT groups resembled the postmenopausal groups. No significant differences in anti-HIV activity by menopausal or by HIV status were noted. Our findings indicate that the female genital tract immune microenvironment is distinct by menopausal status and HIV status. Further studies are needed to assess the risk of HIV acquisition/transmission in this population.

Utility of tissue elafin as an immunohistochemical marker for diagnosis of acute skin graft-versus-host disease: a pilot study.

BACKGROUND: The skin is the most common organ involved in acute graft-versus-host disease (GvHD). Because histopathology has limited utility in ruling out clinical mimics of acute skin GvHD, more accurate diagnostic techniques are required. AIM: To evaluate the utility of elafin expression in skin by immunohistochemistry (IHC) for accurate diagnosis of acute skin GvHD. METHODS: Consecutive allogeneic haematopoietic stem cell transplant (HSCT) recipients during a 6-month period who developed rash within the first 100 days post-transplant were recruited. Skin biopsies were taken on the day the rash developed. IHC for epidermal elafin was performed and interpreted by a pathologist blinded to the histopathological diagnosis. Staining of ≥ 50% of epidermis was considered positive. Final diagnosis of the rash was assigned using clinical features supported by histopathology. The accuracy of elafin IHC in predicting the final diagnosis of acute GvHD was evaluated. RESULTS: In total, 23 patients (20 male, 3 female; median age 16 years, range 3-53 years) with 27 episodes of skin rash were recruited. Skin rash post-HSCT occurred at a median of 20 days (range 5-45 days). A diagnosis of GvHD was made in 16 episodes (59.26%) while the remaining 11 episodes (40.74%) were judged to be non-GvHD rash. Elafin IHC was positive in all patients with GvHD. Of the 11 episodes of non-GvHD rash, elafin was negative in 8. Thus, the sensitivity and specificity of elafin IHC for predicting acute skin GvHD was 100% and 75%, respectively. CONCLUSION: Tissue elafin is a useful immunohistochemical marker for acute skin GvHD. However, larger studies are needed to validate these results.

Reduced levels of genital tract immune biomarkers in postmenopausal women: implications for HIV acquisition.

BACKGROUND: Rates of HIV infections are increasing in older adults. Although it is known that the HIV/AIDS epidemics affects women disproportionately, little is known regarding immune functions in the genital tract of postmenopausal women, as relevant to HIV susceptibility. OBJECTIVE: The objective of the study was to compare levels of female reproductive tract immune mediators that are important for HIV-associated immune responses as well as intrinsic anti-HIV activity in the cervical vaginal lavages collected from HIV-negative pre- and postmenopausal women. STUDY DESIGN: Cervical vaginal lavage from 20 premenopausal and 20 postmenopausal women were assayed for interleukin-6, interleukin-8, tumor necrosis factor-α, secretory leukocyte protease inhibitor, elafin, human ß-defensin-2, and macrophage inflammatory protein-3α using standard enzyme-linked immunosorbent assays. Anti-HIV activity of cervical-vaginal lavage was measured using TZM-bl indicator cells against HIV-1 IIIB and BaL. Whereas each postmenopausal woman provided only 1 sample, each premenopausal woman provided 3 samples, during proliferative, ovulatory, and secretory stages, based on menstrual dates. RESULTS: We observed significantly lower levels of tumor necrosis factor-α, MIP-3α, secretory leukocyte protease inhibitor, elafin, and human ß-defensin-2 in cervical vaginal lavage from postmenopausal women compared with premenopausal women. Inhibition of HIV-1 infection was observed for both pre- and postmenopausal women, but cervical vaginal lavage from postmenopausal women showed significantly higher inhibition against HIV-1 BaL after adjusting for total protein concentration, genital pH, and reproductive tract infections. No change in mediators or HIV inhibition was observed through the stages of menstrual cycle. In addition, we observed that postmenopausal women with reproductive tract infections had significantly higher levels of tumor necrosis factor-α and significantly lower levels of interleukin-8, which were not observed in premenopausal women. CONCLUSION: Our findings suggest that female reproductive tract immune microenvironment is distinct in HIV-negative postmenopausal women. Further studies are needed to assess the risk of HIV acquisition/transmission in this population.

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.

Targeted silencing of DEFB4 in a bioengineered skin-humanized mouse model for psoriasis: development of siRNA SECosome-based novel therapies.

Psoriasis is a complex inflammatory skin disease that presents a wide variety of clinical manifestations. Human ß defensin-2 (hBD-2) is highly up-regulated in psoriatic lesions and has been defined as a biomarker for disease activity. We explored the potential benefits of targeting hBD-2 by topical application of DEFB4-siRNA-containing SECosomes in a bioengineered skin-humanized mouse model for psoriasis. A significant improvement in the psoriatic phenotype was observed by histological examination, with a normalization of the skin architecture and a reduction in the number and size of blood vessels in the dermal compartment. Treatment leads to the recovery of transglutaminase activity, filaggrin expression and stratum corneum appearance to the levels similar to those found in normal regenerated human skin. The availability of a reliable skin-humanized mouse model for psoriasis in conjunction with the use of the SECosome technology may provide a valuable preclinical tool for identifying potential therapeutic targets for this disease.

Innate immunity in the vagina (part I): estradiol inhibits HBD2 and elafin secretion by human vaginal epithelial cells.

PROBLEM: Vaginal epithelial cells (VEC) are the first line of defense against incoming pathogens in the female reproductive tract. Their ability to produce the anti-HIV molecules elafin and HBD2 under hormonal stimulation is unknown. METHOD OF STUDY: Vaginal epithelial cells were recovered using a menstrual cup and cultured overnight prior to treatment with estradiol (E2), progesterone (P4) or a panel of selective estrogen response modulators (SERMs). Conditioned media were recovered and analyzed for protein concentration and anti-HIV activity. RESULTS: E2 significantly decreased the secretion of HBD2 and elafin by VEC over 48 hrs, while P4 and the SERMs (tamoxifen, PHTTP, ICI or Y134) had no effect. VEC conditioned media from E2 -treated cells had no anti-HIV activity, while that from E2 /P4 -treated cells significantly inhibited HIV-BaL infection. CONCLUSION: The menstrual cup allows for effective recovery of primary VEC. Their production of HBD2 and elafin is sensitive to E2, suggesting that innate immune protection varies in the vagina across the menstrual cycle.

Proteolytic cleavage of elafin by 20S proteasome may contribute to inflammation in acute lung injury.

RATIONALE: We hypothesise that elafin levels in acute lung injury (ALI) decrease over time due, in part, to proteolytic degradation as observed in other lung diseases. OBJECTIVES: The aim of this study was to characterise temporal changes in elafin concentration in patients with ALI and to evaluate whether a decrease in elafin levels is due to elevated protease activity. METHODS: Bronchoalveolar lavage fluid (BALF) was obtained from patients with ALI within 48 h of onset of ALI (day 0), at day 3 and at day 7. Elafin levels were quantified by ELISA. Elafin susceptibility to proteolytic cleavage by ALI BALF was assessed by Western blot and by high-performance liquid chromatography-mass spectrometry. MEASUREMENTS AND MAIN RESULTS: Elafin levels were found to be significantly increased at the onset of ALI compared with healthy volunteers and fell significantly by day 7 compared with day 0. In contrast, levels of secretory leukocyte protease inhibitor did not decrease over time. This decrease in elafin was due to cleavage by the 20S proteasome which was significantly increased in ALI BALF. Incubation of ALI BALF with the proteasome inhibitor epoxomicin confirmed that 20S proteasome protease activity was responsible for proteolytic cleavage of elafin, resulting in diminished anti-elastase activity. In addition, free neutrophil elastase activity significantly increased in ALI BALF from day 0 to day 7. CONCLUSIONS: Elafin concentrations fall within the pulmonary compartment over the course of ALI as a result of proteolytic degradation. This loss of elafin may predispose people, in part, to excessive inflammation in ALI.

Rhinovirus infection induces degradation of antimicrobial peptides and secondary bacterial infection in chronic obstructive pulmonary disease.

RATIONALE: Chronic obstructive pulmonary disease (COPD) exacerbations are associated with virus (mostly rhinovirus) and bacterial infections, but it is not known whether rhinovirus infections precipitate secondary bacterial infections. OBJECTIVES: To investigate relationships between rhinovirus infection and bacterial infection and the role of antimicrobial peptides in COPD exacerbations. METHODS: We infected subjects with moderate COPD and smokers and nonsmokers with normal lung function with rhinovirus. Induced sputum was collected before and repeatedly after rhinovirus infection and virus and bacterial loads measured with quantitative polymerase chain reaction and culture. The antimicrobial peptides secretory leukoprotease inhibitor (SLPI), elafin, pentraxin, LL-37, α-defensins and ß-defensin-2, and the protease neutrophil elastase were measured in sputum supernatants. MEASUREMENTS AND MAIN RESULTS: After rhinovirus infection, secondary bacterial infection was detected in 60% of subjects with COPD, 9.5% of smokers, and 10% of nonsmokers (P < 0.001). Sputum virus load peaked on Days 5-9 and bacterial load on Day 15. Sputum neutrophil elastase was significantly increased and SLPI and elafin significantly reduced after rhinovirus infection exclusively in subjects with COPD with secondary bacterial infections, and SLPI and elafin levels correlated inversely with bacterial load. CONCLUSIONS: Rhinovirus infections are frequently followed by secondary bacterial infections in COPD and cleavage of the antimicrobial peptides SLPI and elafin by virus-induced neutrophil elastase may precipitate these secondary bacterial infections. Therapy targeting neutrophil elastase or enhancing innate immunity may be useful novel therapies for prevention of secondary bacterial infections in virus-induced COPD exacerbations.

Periodontal pathogens affect the level of protease inhibitors in gingival crevicular fluid.

In periodontitis, an effective host-response is primarily related to neutrophils loaded with serine proteases, including elastase (NE) and protease 3 (PR3), the extracellular activity of which is tightly controlled by endogenous inhibitors. In vitro these inhibitors are degraded by gingipains, cysteine proteases produced by Porphyromonas gingivalis. The purpose of this study was to determine the level of selected protease inhibitors in gingival crevicular fluid (GCF) in relation to periodontal infection. The GCF collected from 31 subjects (nine healthy controls, seven with gingivitis, five with aggressive periodontitis and 10 with chronic periodontitis) was analyzed for the levels of elafin and secretory leukocyte protease inhibitor (SLPI), two main tissue-derived inhibitors of neutrophil serine proteases. In parallel, activity of NE, PR3 and arginine-specific gingipains (Rgps) in GCF was measured. Finally loads of P. gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola were determined. The highest values of elafin were found in aggressive periodontitis and the lowest in controls. The quantity of elafin correlated positively with the load of P. gingivalis, Ta. forsythia and Tr. denticola, as well as with Rgps activity. In addition, NE activity was positively associated with the counts of those bacterial species, but not with the amount of elafin. In contrast, the highest concentrations of SLPI were found in periodontally healthy subjects whereas amounts of this inhibitor were significantly decreased in patients infected with P. gingivalis. Periodontopathogenic bacteria stimulate the release of NE and PR3, which activities escape the control through degradation of locally produced inhibitors (SLPI and elafin) by host-derived and bacteria-derived proteases.

Protease inhibitor levels in periodontal health and disease.

BACKGROUND AND OBJECTIVE: Our previous study showed that protease inhibitors were attenuated by the periodontal pathogen Porphyromonas gingivalis in cultured gingival epithelial cells. We hypothesize that fewer protease inhibitors would be present in more advanced periodontal disease sites, where the level of P. gingivalis may be high. The goal of this study was to investigate the relationship between the protease inhibitor [secretory leukocyte protease inhibitor (SLPI), elastase-specific inhibitor (ELAFIN) and squamous cell carcinoma antigen (SCCA)] levels in gingival crevicular fluid and the number of P. gingivalis micro-organisms in subgingival plaque. MATERIAL AND METHODS: Plaque samples from subjects without (n = 18) and with moderate to advanced periodontitis (n = 41) were used to quantify P. gingivalis using real-time PCR. Protease inhibitor levels in the gingival crevicular fluid of all the subjects were determined by ELISA. RESULTS: P. gingivalis was detected in 68.3% of patients with periodontitis, while 16.7% of subjects without periodontitis had a detectable level of P. gingivalis. Patients with periodontitis and P. gingivalis in their plaque exhibited lower SLPI and ELAFIN levels (p < 0.001) compared with control subjects without periodontitis. Secretory leukocyte protease inhibitor was also reduced (p < 0.05) in gingival crevicular fluid of periodontitis patients without a detectable level of P. gingivalis. Periodontitis patients with high vs. low levels of P. gingivalis exhibited reciprocal mean levels of SLPI and ELAFIN concentrations. CONCLUSION: The reduced concentrations of SLPI and ELAFIN may contribute to the loss of host protective capacity and increase susceptibility to breakdown from chronic infection. The work of this investigation may aid in finding diagnostic and prognostic markers in periodontal health and disease and may also help in finding pharmacological targets directed against periodontal inflammation.

The influence of hydrosalpinx on endometrial elafin expression.

The endometrium of women with hydrosalpinx has an increased number of neutrophils and lower expression of elafin, an elastase inhibitor and natural antimicrobial molecule. These findings suggest that women with hydrosalpinx have a reduced antimicrobial and antielastase activity.

Innate immunity proteins in chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis.

Chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) may be caused by epithelial cell injury. Epithelial cells respond to injury by secreting innate immunity proteins. To investigate whether altered levels of innate immunity proteins are observed in COPD and IPF, the authors assessed secretory leukocyte protease inhibitor (SLPI), elafin, CC16, and beta-defensin-2 levels by enzyme-linked immunosorbent assay (ELISA) in sputum supernatants from COPD patients (n = 19), smokers without COPD (n = 21), and never-smokers (n = 10) and in BALF supernatants from patients with IPF (n = 11) and subjects without IPF (n = 11). CC16 levels were decreased, whereas SLPI and elafin levels were increased in COPD patients (0.8 [0-4.2] microg/mL, 2.5 [0.3-10.5] microg/mL, 213 [152-318] pg/mL, respectively) compared to smokers without COPD (1.8 [0.1-21.2] microg/mL, 0.8 [0.2-2.6] microg/mL, 172 [71-473] pg/mL, respectively) and never-smokers (0.5 [0-4.8] microg/mL, 0.1 [0.05-0.6] microg/mL, 188 [129-218] pg/mL, respectively) (CC16: P = .001; SLPI: P <.001; elafin: P = .041). beta-Defensin-2 was detected in smokers without COPD (98 [10-729] pg/mL) and never-smokers (74 [35-410] pg/mL), but not in COPD. SLPI and elafin levels did not differ between IPF patients and controls, but CC16 levels were increased in IPF (0.5 [0-2.3] versus 0.2 [0-0.3] microg/mL; P = .019). beta-Defensin-2 was not detected in BALF. In conclusion, in COPD, secretion of CC16 and beta-defensin-2 might be suppressed, whereas SLPI and elafin secretion is up-regulated. In IPF, only CC16 secretion is up-regulated.

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

OBJECTIVES: Globally, heterosexual intercourse is the primary route of HIV-1 (HIV) transmission. It follows that mechanisms that protect against HIV infection are likely operative at the genital mucosa. In HIV-resistant Kenyan sex workers who are highly exposed to HIV infection yet remain uninfected, protection correlates with HIV-specific immune responses and genetic factors. However, these factors do not entirely explain this model of natural immunity to HIV. We hypothesized that protection may be mediated by innate immune proteins in the genital tract of HIV-resistant sex workers. DESIGN AND METHODS: The genital proteome of mucosal secretions from HIV-resistant women was examined using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Cervical lavage samples were collected from 315 HIV-resistant, HIV-uninfected and HIV-infected commercial sex workers. RESULTS: Univariate analysis identified a 6 kDa biomarker of HIV resistance in genital secretions from these women. This protein was identified by tandem mass spectrometry as elafin and was found to be overexpressed in HIV-resistant women compared with HIV-uninfected (P = 0.001) and infected (P = 0.002) women. The elevated levels of elafin/trappin-2 in HIV-resistant women were confirmed using ELISA. The prospective association of elevated cervicovaginal elafin/trappin-2 levels with protection from HIV acquisition was then confirmed in an independent cohort of high-risk female sex workers. CONCLUSION: Using a unique proteomics approach in a large scale, cross-sectional cohort study, we identified elafin/trappin-2 as a novel innate immune factor, which is highly associated with resistance. This association was confirmed within an independent, prospective cohort study. Genital tract elafin/trappin-2 levels constitute a natural correlate of HIV protection in humans.