Godwin A. Ananaba

Suppression of Endogenous IL-10 Gene Expression in Dendritic Cells Enhances Antigen Presentation for Specific Th1 Induction: Potential for Cellular Vaccine Development

A new paradigm for designing vaccines against certain microbial pathogens, including Chlamydia trachomatis, is based on the induction of local mucosal Th1 response. IL-10 is an anti-inflammatory cytokine that exerts negative immunoregulatory influence on Th1 response. This study investigated whether biochemical modulation of endogenous IL-10 expression at the level of APCs is a practical strategy for enhancing the specific Th1 response against pathogens controlled by Th1 immunity. The results revealed that the high resistance of genetically engineered IL-10−/− (IL-10KO) mice to genital chlamydial infection is a function of the predilection of their APCs to rapidly and preferentially activate a high Th1 response. Thus, in microbiological analysis, IL-10KO mice suffered a shorter duration of infection, less microbial burden, and limited ascending infection than immunocompetent wild-type mice. Also, IL-10KO were resistant to reinfection after 8 wk of the primary infection. Cellular and molecular immunologic evaluation indicated that IL-10KO mice induced greater frequency of chlamydial-specific Th1 response following C. trachomatis infection. Moreover, IL-10KO APCs or antisense IL-10 oligonucleotide-treated wild-type APCs were potent activators of Th1 response from naive or immune T cells. Furthermore, both Ag-pulsed dendritic cells from IL-10KO mice and IL-10 antisense-treated dendritic cells from wild-type mice were efficient cellular vaccines in adoptive immunotherapeutic vaccination against genital chlamydial infection. These findings may furnish a novel immunotherapeutic strategy for boosting the Th1 response against T cell-controlled pathogens and tumors, using IL-10-deficient APCs as vaccine delivery agents.

Fc receptor regulation of protective immunity against Chlamydia trachomatis

The prevailing paradigm for designing potentially efficacious vaccines against the obligate intracellular bacterium, Chlamydia trachomatis, advocates regimens capable of inducing a mucosal antigen‐specific T helper type 1 (Th1) response. However, recent reports indicate that rapid and efficient clearance of a secondary infection also requires certain B‐cell functions. We investigated the hypothesis that Fc receptor (FcR)‐mediated antibody effector mechanisms are important B‐cell‐related functions involved in controlling a chlamydial genital reinfection. Microbiological analysis of genital chlamydial infection in FcR knockout (FcRKO) mice lacking the activatory FcγRI (CD64) and FcRγIII (CD16), as well as the inhibitory FcγRIIB1 (CD32), revealed a greater intensity of secondary infection (i.e. bacterial shedding) in FcR−/− as compared to FcR+/+ mice; however, the course of the primary infection was indistinguishable in both animals. Pathologically, FcRKO mice suffered greater ascending infection than immunocompetent wild‐type (WT) mice after a secondary infection. Immunological evaluation indicated that the presence of specific anti‐chlamydial antibodies enhanced chlamydial antigen presentation for induction of a Th1 response by FcR+/+, but not FcR−/−, antigen‐presenting cells. In addition, specific anti‐chlamydial antibodies augmented both macrophage killing of infected epithelial cells by antibody‐dependent cellular cytotoxicity (ADCC) and macrophage inhibition of productive growth of chlamydiae in co‐cultures. These results indicate that B cells participate in anti‐chlamydial immunity via FcR‐mediated effector functions of antibodies, which are operative during reinfections. Such effector functions include ADCC, and possibly enhanced uptake, processing and presentation of chlamydial antigens for rapid induction of a Th1 response, all facilitating the early clearance of an infection. These findings suggest that a future anti‐chlamydial vaccine should elicit both humoral and T‐cell‐mediated immune responses for optimal memory response and vaccine efficacy.

A Novel Recombinant Multisubunit Vaccine against Chlamydia

The administration of an efficacious vaccine is the most effective long-term measure to control the oculogenital infections caused by Chlamydia trachomatis in humans. Chlamydia genome sequencing has identified a number of potential vaccine candidates, and the current challenge is to develop an effective delivery vehicle for induction of a high level of mucosal T and complementary B cell responses. Vibrio cholerae ghosts (VCG) are nontoxic, effective delivery vehicles with potent adjuvant properties, and are capable of inducing both T cell and Ab responses in mucosal tissues. We investigated the hypothesis that rVCG could serve as effective delivery vehicles for single or multiple subunit chlamydial vaccines to induce a high level of protective immunity. rVCG-expressing chlamydial outer membrane proteins were produced by a two-step genetic process, involving cloning of Omp genes in V. cholerae, followed by gene E-mediated lysis of the cells. The immunogenicity and vaccine efficacy of rVCG-expressing single and multiple subunits were compared. Immunologic analysis indicated that i.m. immunization of mice with either vaccine construct induced a strong mucosal and systemic specific Th1 response against the whole chlamydial organism. However, there was an immunogenic advantage associated with the multiple subunit vaccine that induced a higher frequency of Th1 cells and a relatively greater ability to confer protective immunity, compared with the single subunit construct. These results support the operational theory that the ability of a vaccine to confer protective immunity against Chlamydia is a function of the level of Th1 response elicited.

Recombinant Vibrio cholerae ghosts as a delivery vehicle for vaccinating against Chlamydia trachomatis.

An efficacious vaccine is needed to control the morbidity and burden of rising healthcare costs associated with genital Chlamydia trachomatis infection. Despite considerable efforts, the development of reliable chlamydial vaccines using conventional strategies has proven to be elusive. The 40kDa major outer membrane protein (MOMP) of C. trachomatis is so far the most promising candidate for a subunit vaccine. The lack of satisfactory protective immunity with MOMP-based vaccine regimens to date would suggest that either MOMP alone is inadequate as a vaccine candidate or better delivery systems are needed to optimize the effect of MOMP. Recombinant Vibrio cholerae ghosts (rVCG) are attractive for use as non-living vaccines because they possess strong adjuvant properties and are excellent vehicles for delivery of antigens of vaccine relevance to mucosal sites. The suitability of the ghost technology for designing an anti-chlamydial vaccine was evaluated by constructing a rVCG vector-based candidate vaccine expressing MOMP (rVCG-MOMP) and assessing vaccine efficacy in a murine model of C. trachomatis genital infection. Intramuscular delivery of the rVCG-MOMP vaccine induced elevated local genital mucosal as well as systemic Th1 responses. In addition, immune T cells from immunized mice could transfer partial protection against a C. trachomatis genital challenge to nai;ve mice. These results suggest that rVCG expressing chlamydial proteins may constitute a suitable subunit vaccine for inducing an efficient mucosal T cell response that protects against C. trachomatis infection. Altogether, the potency and relatively low production cost of rVCG offer a significant technical advantage as a chlamydial vaccine.

Chemokine and Chemokine Receptor Dynamics during Genital Chlamydial Infection

ABSTRACT Current design strategies for vaccines against certain microbial pathogens, including Chlamydia trachomatis, require the induction and targeting of specific immune effectors to the local sites of infection known as the mucosal effector sites. Chemokines and their receptors are important mediators of leukocyte trafficking and of the controlled recruitment of specific leukocyte clonotypes during host defense against infections and during inflammation. We analyzed the dynamics of chemokine and chemokine receptor expression in genital mucosae during genital chlamydial infection in a murine model to determine how these molecular entities influence the development of immunity and the clearance of infection. A time course study revealed an increase of up to threefold in the levels of expression of RANTES, monocyte chemotactic protein 1 (MCP-1), gamma-interferon-inducible protein 10 (IP-10), macrophage inflammatory protein 1α (MIP-1α), and intercellular adhesion molecule type 1 (ICAM-1) after genital infection with the C. trachomatis agent of mouse pneumonitis. Peak levels of expression of RANTES, MCP-1, and MIP-1α occurred by day 7 after primary infection, while those of IP-10 and ICAM-1 peaked by day 21. Expression levels of these molecules decreased by day 42 after primary infection, by which time all animals had resolved the infection, suggesting an infection-driven regulation of expression. A rapid upregulation of expression of these molecules was observed after secondary infection. The presence of cells bearing the chemokine receptors CCR5 and CXCR3, known to be preferentially expressed on Th1 and dendritic cells, was also synchronous with the kinetics of immune induction in the genital tract and clearance of infection. Results demonstrated that genital chlamydial infection is associated with a significant induction of chemokines and chemokine receptors that are involved in the recruitment of Th1 cells into the site of infection. Future studies will focus on how selective modulation of chemokines and their receptors can be used to optimize long-term immunity against Chlamydia.

Role of T Lymphocytes in the Pathogenesis of Chlamydia Disease

Vaccines are needed to prevent the oculogenital diseases of Chlamydia trachomatis. Infected hosts develop immunity, although temporary, and experimental vaccines have yielded significant protective immunity in animal models, fueling the impetus for a vaccine. Because infections cause sequelae, the functional relationship between infection- and vaccine-induced immunity is unclear. We hypothesized that infection- and vaccine-induced immunity are functionally distinct, particularly in the ability to prevent sequelae. Chlamydia-immune mice, with immunity generated by either a previous infection or vaccination, exhibited a significant degree of protective immunity, marked by a lower-intensity, abbreviated course of infection. However, vaccinated mice were protected from infertility, whereas preinfected mice were not. Thus, infection-induced immunity does not prevent the pathologic process leading to infertility. Furthermore, T cell subsets, especially CD8 T cells, play a major role in Chlamydia-induced infertility. The results have important implications for the immunopathogenesis of chlamydial disease and new vaccine strategies.

Live-attenuated influenza viruses as delivery vectors for Chlamydia vaccines.

Effective delivery systems are needed to design efficacious vaccines against the obligate intracellular bacterial pathogen, Chlamydia trachomatis. Potentially effective delivery vehicles should promote the induction of adequate levels of mucosal T‐cell and antibody responses that mediate long‐term protective immunity. Antigen targeting to the nasal‐associated lymphoid tissue (NALT) is effective for inducing high levels of specific immune effectors in the genital mucosa, and therefore suitable for vaccine delivery against genital chlamydial infection. We tested the hypothesis that live attenuated influenza A viruses are effective viral vectors for intranasal delivery of subunit vaccines against genital chlamydial infection. Recombinant influenza A/PR8/34 (H1N1) viruses were generated by insertion of immunodominant T‐cell epitopes from chlamydial major outer membrane protein into the stalk region of the neuraminidase gene. Intranasal immunization of mice with viral recombinants resulted in a strong T helper 1 (Th1) response against intact chlamydial elementary bodies. Also, immunized mice enjoyed a significant state of protective immunity (P > 0·002) by shedding less chlamydiae and rapidly clearing the infection. Furthermore, a high frequency of Chlamydia‐specific Th1 was measured in the genital mucosal and systemic draining lymphoid tissues within 24 hr after challenge of vaccinated mice. Moreover, multiple epitope delivery provided a vaccine advantage over single recombinants. Besides, long‐term protective immunity correlated with the preservation of a robustly high frequency of specific Th1 cells and elevated immunoglobulin G2a in genital secretions. Because live attenuated influenza virus vaccines are safe and acceptable for human use, they may provide a new and reliable approach to deliver efficacious vaccines against sexually transmitted diseases.

Differential effects of cholesterol and phytosterols on cell proliferation, apoptosis and expression of a prostate specific gene in prostate cancer cell lines

BACKGROUND The purpose of our study was to show the apoptotic and anti-proliferative effects of phytosterols as distinct from cholesterol effects on prostate cancer cell lines, and also their differential expression of caveolin-1, and a prostate specific gene, PCGEM1. METHODS PC-3 and DU145 cells were treated with sterols (cholesterol and phytosterols) for 48h, followed by trypan blue dye exclusion measurement of cytotoxicity and MTT cell proliferation assays, respectively. Cell cycle analysis was carried out microscopically, and by propidium iodide uptake using flow cytometry. Sterol induction of oncogenic gene expression was evaluated by RT-PCR. Apoptotic cells were identified by immunocytochemistry using DNA fragmentation method, and by annexin V adhesion using flow cytometry. RESULTS Physiological doses (16microM) of these sterols were not cytotoxic in these cells. Cholesterol-enrichment promoted mitosis (54 and 61% by microscopy; 40.8 and 34.08% by FACS analysis in PC-3 and DU145, respectively) and cell growth (P<0.05), while phytosterols suppressed mitosis (29 and 35% by microscopy; 27.71 and 17.37% by FACS analysis in PC-3 and DU145, respectively), and significantly induced tumor-suppression (P<0.05) and apoptosis. We demonstrated for the first time that cholesterols upregulated the expression of PCGEM1 even in androgen-insensitive prostate cancer cell lines. Phytosterols reversed this effect, while upregulating the expression of caveolin-1, a known mediator of androgen-dependent proto-oncogene signals that presumably control growth and anti-apoptosis. CONCLUSIONS Phytosterol inhibition of PCGEM1 and cell growth and the overexpression of caveolin-1, suggests that poor disease prognosis anchors on the ability of caveolin-1 to regulate downstream oncogene(s) and apoptosis genes. Sterol intake may contribute to the disparity in incidence of prostate cancer, and elucidation of the mechanism for modulation of growth and apoptosis signaling may reveal potential targets for cancer prevention and/or chemotherapeutic intervention. Sterol regulation of PCGEM1 expression suggests its potential as biomarker for prediction of neoplasms that would be responsive to chemoprevention by phytosterols.

Molecular Basis for the Potency of IL-10-Deficient Dendritic Cells as a Highly Efficient APC System for Activating Th1 Response

Identification and targeting of novel immunobiological factors that regulate the induction of Th1 cells are crucial for designing effective vaccines against certain intracellular pathogens, including Chlamydia. IL-10-deficient dendritic cells (DC) are potent APCs and effective cellular vaccines that activate a high frequency of specific Th1 cells. To elucidate the molecular basis for the potency of the IL-10-deficient APC system, we tested the hypothesis that Chlamydia Ag-primed IL-10 knockout (IL-10KO) DC are quantitatively and qualitatively distinct in their metabolic characteristics relating to T cell activation. Using a combination of RT-PCR, two-dimensional gel electrophoresis, and MALDI-TOF-based proteomics analyses, the transcriptional and translational activities of Chlamydia-pulsed DC from wild-type and IL-10KO mice were assessed. IL-10 deficiency caused early maturation and activation of pulsed DC (i.e., high CD11c, CD40, CD80, CD83, CD86, IL-1, IL-12, and the T cell-attracting chemokine CCL27/CTACK) and consequently an enhanced ability to process and present Ags for a rapid and robust T cell activation. Supporting comparative proteomics revealed further that IL-10 deficient DC possess specific immunobiological properties, e.g., the T cell-attracting chemokine CCL27/CTACK, calcium-dependent protein kinase, and the IL-1/IL-12 inducer, NKR-P1A (CD161), which differentiated them immunologically from wild-type DC that express molecules relating to anti-inflammatory, differentiative, and metabolic processes, e.g., the anti-IL-12 molecule peroxisome proliferator-activated receptor-α and thymidine kinase. Collectively, these results provide a molecular basis for the high Th1-activating capacity of IL-10KO APC and may provide unique immunomodulation targets when designing vaccines against pathogens controlled by T cell immunity.

Immune Control of Chlamydial Growth in the Human Epithelial Cell Line RT4 Involves Multiple Mechanisms That Include Nitric Oxide Induction, Tryptophan Catabolism and Iron Deprivation

The antimicrobial activity of T cell‐derived cytokines, especially interferon (IFN)‐γ, against intracellular pathogens, such as Chlamydia trachomatis, involves the induction of 3 major biochemical processes: tryptophan catabolism, nitric oxide (NO) induction and intracellular iron (Fe) deprivation. Since the epithelial cell is the natural target of chlamydial infection, the presence of these antimicrobial systems in the cell would suggest that they may be involved in T cell control of intracellular multiplication of Chlamydia. However, the controversy over whether these 3 antimicrobial processes are present in both mice and humans has precluded the assessment of the relative contribution of each of the 3 mechanisms to chlamydial inhibition in the same epithelial cell from either mice or humans. In the present study, we identified a Chlamydia‐susceptible human epithelial cell line, RT4, that possesses the 3 antimicrobial systems, and we examined the role of nitric oxide (NO) induction, and deprivation of tryptophan or Fe in cytokine‐induced inhibition of chlamydiae. It was found that the 3 antimicrobial systems contributed to cytokine‐mediated inhibition of the intracellular growth of Chlamydia. NO induction accounted for ~20% of the growth inhibition; tryptophan catabolism contributed approximately 30%; iron deprivation was least effective; but the combination of the 3 systems accounted for greater than 60% of the inhibition observed. These results indicate that immune control of chlamydial growth in human epithelial cells may involve multiple mechanisms that include NO induction, tryptophan catabolism and Fe deprivation.