Background: Approximately 40% of human pregnancies are unintended, indicating a need for more acceptable effective contraception methods. New antibody production systems make it possible to manufacture reagent-grade human monoclonal antibodies (mAbs) for clinical use. We used the Nicotiana platform to produce a human antisperm mAb and tested its efficacy for on-demand topical contraception. Methods: Heavy and light chain variable region DNA sequences of a human IgM antisperm antibody derived from an infertile woman were inserted with human IgG 1 constant region sequences into an agrobacterium and transfected into Nicotiana benthamiana. The product, an IgG 1 mAb ["Human Contraception Antibody" (HCA)], was purified on Protein A columns, and QC was performed using the LabChip GXII Touch protein characterization system and SEC-HPLC. HCA was tested for antigen specificity by immunofluorescence and western blot assays, antisperm activity by sperm agglutination and complement dependent sperm immobilization assays, and safety in a human vaginal tissue (EpiVaginal TM ) model. Findings: HCA was obtained at concentrations ranging from 0.4 to 4 mg/ml and consisted of > 90% IgG monomers. The mAb specifically reacted with a glycan epitope on CD52g, a glycoprotein produced in the male reproductive tract and found in abundance on sperm. HCA potently agglutinated sperm under a variety of relevant physiological conditions at concentrations 6.25 mg/ml, and mediated complement-dependent sperm immobilization at concentrations 1 mg/ml. HCA and its immune complexes did not induce inflammation in EpiVaginal TM tissue. Interpretation: HCA, an IgG1 mAb with potent sperm agglutination and immobilization activity and a good safety profile, is a promising candidate for female contraception.
High rates of unintended pregnancies worldwide indicate a need for more accessible and acceptable methods of contraception. We have developed a monoclonal antibody, the Human Contraception Antibody (HCA), for use by women in vaginal films and rings for contraception. The divalent F(ab’)2 region of HCA binds to an abundant male reproductive tract-specific antigen, CD52g, and potently agglutinates sperm. Certain other antibody activities mediated by the Fc region such as mucus trapping, complement-dependent cytotoxicity (CDC) and antibody-dependent cellular phagocytosis (ADCP) could have beneficial or negative effects. The purpose of this study was to document HCA Fc effector functions and determine whether an engineered variant of HCA with a modified Fc region, HCA-LALAPG, retains desirable contraceptive activity while minimizing Fc-mediated effects. Fab and Fc functions were compared between HCA and HCA-LALAPG. Fab activity was assessed using sperm agglutination and modified swim-up ("sperm escape”) assays. Fc functions were assessed by CDC (sperm immobilization), ADCP, and cervical mucus penetration assays. HCA and HCA-LALAPG showed equivalent activity in assays of Fab function. In the assays of Fc function, HCA supported strong CDC, ADCP, and sperm trapping in cervical mucus whereas HCA-LALAPG demonstrated little to no activity. HCA and the HCA-LALAPG variant were both highly effective in the sperm agglutination assays but differed in Fc mediated functions. Use of the HCA-LALAPG variant for contraception in women could reduce antibody-mediated inflammation and antigen presentation but may have reduced contraceptive efficacy due to much weaker sperm trapping in mucus and complement-dependent sperm immobilization activity.
BackgroundWomen with diverse genital anaerobic bacterial communities, are at over 4-fold higher risk of HIV acquisition than women with a Lactobacillus-rich vaginal microbiome. The mechanisms underlying this are poorly understood. We set out to examine how vaginal microbiota diversity affects epithelial integrity in HIV sero-negative pregnant women. We also investigated how HIV infection alters mucosal integrity within the prevalent genital microbiome diversity.MethodsWe assessed epithelial permeability by measuring the concentrations of tight junction proteins, claudin-1 and zonula occludens- (ZO)-1, in cervico-vaginal lavages (CVL) by enzyme-linked immunosorbent assay (ELISA). Cytokines in the vaginal fluids were measured by multiplex magnetic bead assay to establish the inflammatory state. Bacterial cell-free supernatants were used to treat vaginal epithelial cells and tissues, mimicking the in-vivo vaginal milieu. Gene and protein expression levels of tight junctions of vaginal epithelial cells and tissues in response to treatment were quantified by QuantiGene™ Plex Gene Expression Assay and by western blot respectively. The cytokine response of vaginal epithelial cells, VK2 (E6/E7, ATCC® CRL-2616™), to bacterial cell-free supernatants was measured by ELISA method.Results Among women with CT3 cervicotype, HIV sero-negative pregnant women had significantly higher claudin-1 in their CVL than the HIV-infected pregnant women (p=0.0011). IL-8 (p=0.0028), IL-1beta (p<0.0001) and TNF-alpha (p=0.0283) were significantly higher among HIV-negative pregnant women with a non-Lactobacillus dominant vaginal microbiota than those with a Lactobacillus-dominant vaginal microbiota. Bacterial cell-free supernatants from Lactobacillus elicited low levels of pro-inflammatory cytokines IL-1alpha, IL8, IL-6 and IL-1 beta in comparison to media and G. vaginalis. Treatment with G. vaginalis supernatant lowers claudin-1 and claudin-4 expression yet presence of either L. crispatus or L. iners mitigates this effect of G. vaginalis as observed by immuno-staining of treated vaginal cells.Conclusions Pregnant women with a non-Lactobacillus dominant microbiome had a disrupted epithelial barrier and elevated pro-inflammatory cytokines, making them at a higher risk of HIV acquisition than women with a Lactobacillus-dominant microbiome. Targeting vaginal microbiota and/or its effects on the vaginal epithelium and cervico-vaginal milieu can potentially lower rates of HIV acquisition and transmission.
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