A MyD88-dependent early IL-17 production protects mice against airway infection with the obligate intracellular pathogen Chlamydia muridarum

The role of T helper (TH)17 cells as a double-edged sword in the interplay of infection and autoimmunity with a focus on xenobiotic-induced immunomodulation

Extensive research in recent years suggests that exposure to xenobiotic stimuli plays a critical role in autoimmunity induction and severity and that the resulting response would be exacerbated in individuals with an infection-aroused immune system. In this context, heavy metals constitute a prominent category of xenobiotic substances, known to alter divergent immune cell responses in accidentally and occupationally exposed individuals, thereby increasing the susceptibility to autoimmunity and cancer, especially when accompanied by inflammation-triggered persistent sensitization. This perception is learned from experimental models of infection and epidemiologic studies and clearly underscores the interplay of exposure to such immunomodulatory elements with pre- or postexposure infectious events. Further, the T_H17 cell subset, known to be associated with a growing list of autoimmune manifestations, may be the “superstar” at the interface of xenobiotic exposure and autoimmunity. In this review, the most recently established links to this nomination are short-listed to create a framework to better understand new insights into T_H17's contributions to autoimmunity.

IL-17A and Th17 cells in lung inflammation: an update on the role of Th17 cell differentiation and IL-17R signaling in host defense against infection

The significance of Th17 cells and interleukin- (IL-)17A signaling in host defense and disease development has been demonstrated in various infection and autoimmune models. Numerous studies have indicated that Th17 cells and its signature cytokine IL-17A are critical to the airway's immune response against various bacteria and fungal infection. Cytokines such as IL-23, which are involved in Th17 differentiation, play a critical role in controlling Klebsiella pneumonia (K. pneumonia) infection. IL-17A acts on nonimmune cells in infected tissues to strengthen innate immunity by inducing the expression of antimicrobial proteins, cytokines, and chemokines. Mice deficient in IL-17 receptor (IL-17R) expression are susceptible to infection by various pathogens. In this review, we summarize the recent advances in unraveling the mechanism behind Th17 cell differentiation, IL-17A/IL-17R signaling, and also the importance of IL-17A in pulmonary infection.

Contribution of interleukin-12 p35 (IL-12p35) and IL-12p40 to protective immunity and pathology in mice infected with Chlamydia muridarum

The p35 molecule is unique to interleukin-12 (IL-12), while p40 is shared by both IL-12 and IL-23. IL-12 promotes Th1 T cell responses, while IL-23 promotes Th17 T cell responses. The roles of IL-12p35- and IL-12p40-mediated responses in chlamydial infection were compared in mice following an intravaginal infection with Chlamydia muridarum. Mice deficient in either IL-12p35 or p40 both developed similar but prolonged infection time courses, confirming the roles of IL-12-mediated immune responses in clearing primary infection. However, all mice, regardless of genotype, cleared reinfection within 2 weeks, suggesting that an IL-12- or IL-23-independent adaptive immunity is protective against chlamydial infection. All infected mice developed severe oviduct hydrosalpinx despite the increased Th2 responses in IL-12p35- or IL-12p40-deficient mice, suggesting that Th2-dominant responses can contribute to Chlamydia-induced inflammatory pathology. Compared to IL-12p35 knockout mice, the IL-12p40-deficient mice exhibited more extensive spreading of chlamydial organisms into kidney tissues, leading to significantly increased incidence of pyelonephritis, which both confirms the role of IL-12 or IL-23-independent host responses in Chlamydia-induced pathologies and suggests that in the absence of IL-12/IFN-γ-mediated Th1 immunity, an IL-23-mediated response may play an important role in restricting chlamydial organisms from spreading into distal organs. These observations together provide important information for both understanding chlamydial pathogenesis and developing anti-Chlamydia vaccines.

Experimental and natural infections in MyD88- and IRAK-4-deficient mice and humans

Most Toll-like-receptors (TLRs) and interleukin-1 receptors (IL-1Rs) signal via myeloid differentiation primary response 88 (MyD88) and interleukin-1 receptor-associated kinase 4 (IRAK-4). The combined roles of these two receptor families in the course of experimental infections have been assessed in MyD88- and IRAK-4-deficient mice for almost fifteen years. These animals have been shown to be susceptible to 46 pathogens: 27 bacteria, eight viruses, seven parasites, and four fungi. Humans with inborn MyD88 or IRAK-4 deficiency were first identified in 2003. They suffer from naturally occurring life-threatening infections caused by a small number of bacterial species, although the incidence and severity of these infections decrease with age. Mouse TLR- and IL-1R-dependent immunity mediated by MyD88 and IRAK-4 seems to be vital to combat a wide array of experimentally administered pathogens at most ages. By contrast, human TLR- and IL-1R-dependent immunity mediated by MyD88 and IRAK-4 seems to be effective in the natural setting against only a few bacteria and is most important in infancy and early childhood. The roles of TLRs and IL-1Rs in protective immunity deduced from studies in mutant mice subjected to experimental infections should therefore be reconsidered in the light of findings for natural infections in humans carrying mutations as discussed in this review.

Chlamydophila pneumoniae re-infection triggers the production of IL-17A and IL-17E, important regulators of airway inflammation

OBJECTIVE

Investigation of the effects of interleukin (IL)-17 cytokines in Chlamydophila pneumoniae-infected mice.

METHODS

Mice were infected with C. pneumoniae once or three times and the expression of IL-17 cytokines was followed by RT qPCR from day 1 to day 28 after infection and re-infection. After the treatment of mice with anti-IL-17A, ELISA was used to detect the differences in cytokine and chemokine production. The number and phenotype of the IL-17A-producing cells were determined by ELISPOT.

RESULTS

Chlamydophila pneumoniae induced IL-17A and IL-17F from day 2 after infection, and their levels remained elevated on day 28. The expression of IL-17C, IL-17D and IL-17E mRNA did not change significantly in response to a single infection. The in vivo neutralization of IL-17A resulted in a higher C. pneumoniae burden in the mouse lungs, a decreased cell influx, and diminished chemokine levels. The phenotype of IL-17A-producing cells was CD4(+). The re-infection of mice led to an increased expression of IL-17E mRNA.

CONCLUSION

These results facilitate an understanding of the early inflammatory response after C. pneumoniae infection and suggest that C. pneumoniae re-infection induces the production of a high amount of IL-17E, which has an important role in the pathogenesis of allergic pulmonary diseases.

Anti-chlamydial Th17 responses are controlled by the inducible costimulator partially through phosphoinositide 3-kinase signaling

We previously showed that mice deficient in the Inducible Costimulator ligand (ICOSL-KO) develop more severe disease and lung pathology with delayed bacterial clearance upon respiratory infection of Chlamydia muridarum. Importantly, the exacerbation of disease in ICOSL-KO mice was seen despite heightened IFN-γ/Th1 responses, the major defense mechanisms against Chlamydia. To gain insight into the mechanism of ICOS function in this model, we presently analyzed anti-Chlamydia immune responses in mice lacking the entire ICOS (ICOS-KO) versus knock-in mice expressing a mutant ICOS (ICOS-Y181F) that has selectively lost the ability to activate phosphoinositide 3-kinase (PI3K). Like ICOSL-KO mice, ICOS-KO mice showed worse disease with elevated IFN-γ/Th1 responses compared to wild-type (WT) mice. ICOS-Y181F mice developed much milder disease compared to ICOS-KO mice, yet they were still not fully protected to the WT level. This partial protection in ICOS-Y181F mice could not be explained by the magnitude of IFN-γ/Th1 responses since these mice developed a similar level of IFN-γ response compared to WT mice. It was rather IL-17/Th17 responses that reflected disease severity: IL-17/Th17 response was partially impaired in ICOS-Y181F mice compared to WT, but was substantially stronger than that of ICOS-KO mice. Consistently, we found that both polarization and expansion of Th17 cells were partially impaired in ICOS-Y181F CD4 T cells, and was further reduced in ICOS-KO CD4 T cells in vitro. Our results indicate that once the IFN-γ/Th1 response is above a threshold level, the IL-17/Th17 response becomes a limiting factor in controlling Chlamydia lung infection, and that ICOS plays an important role in promoting Th17 responses in part through the activation of PI3K.

Dendritic cells from oral cavity induce Foxp3(+) regulatory T cells upon antigen stimulation

Evidence is accumulating that dendritic cells (DCs) from the intestines have the capacity to induce Foxp3(+)CD4(+) regulatory T cells (T-regs) and regulate immunity versus tolerance in the intestines. However, the contribution of DCs to controlling immunity versus tolerance in the oral cavity has not been addressed. Here, we report that DCs from the oral cavity induce Foxp3(+) T-regs as well as DCs from intestine. We found that oral-cavity-draining cervical lymph nodes contained higher frequencies of Foxp3(+) T-regs and ROR-γt(+) CD4(+)T cells than other lymph nodes. The high frequency of Foxp3(+) T-regs in the oral-cavity-draining cervical lymph nodes was not dependent on the Toll like receptor (TLR) adaptor molecules, Myd88 and TICAM-1 (TRIF). In contrast, the high frequency of ROR-γt(+) CD4(+)T cells relies on Myd88 and TICAM-1. In vitro data showed that CD11c(+) DCs from oral-cavity-draining cervical lymph nodes have the capacity to induce Foxp3(+) T-regs in the presence of antigen. These data suggest that, as well as in the intestinal environment, antigen-presenting DCs may play a vital role in maintaining tolerance by inducing Foxp3(+) T-regs in the oral cavity.

Key molecules in the differentiation and commitment program of T helper 17 (Th17) cells up-to-date

The mechanisms underlying autoimmunity and cancer remain elusive. However, perpendicular evidence has been evolved in the past decade that T helper (Th)17 cells and their related molecules are implicated in initiation and induction of various disease settings including both diseases. Meanwhile, extensive research on Th17 cells elucidated various molecules including cytokines and transcription factors as well as signaling pathways involved in the differentiation, maturation, survival and ultimate commitment of Th17 cells. In the current review, we revise the mechanistic underpinnings delivered by recent research on these molecules in the Th17 differentiation/commitment concert. We emphasize on those molecules proposed as targets for attaining potential therapies of various autoimmune disorders and cancer, aiming both at dampening the dark-side of Th17 repertoire and simultaneously potentiating its benefits in the roster of the antimicrobial response.

Inflammatory monocyte recruitment is regulated by interleukin-23 during systemic bacterial infection

Listeria monocytogenes is a gram-positive intracellular pathogen that causes meningitis and septicemia in immunocompromised individuals and spontaneous abortion in pregnant women. The innate immune response against L. monocytogenes is primarily mediated by neutrophils and monocytes. Interleukin-23 (IL-23) is an important proinflammatory cytokine well known for its role in neutrophil recruitment in various infectious and autoimmune diseases. We have previously shown that IL-23 is required for host resistance against L. monocytogenes and for neutrophil recruitment to the liver, but not the spleen, during infection. Despite efficient neutrophil recruitment to the spleen, IL-23p19 knockout (KO) mice have an increased bacterial burden in this organ, suggesting that IL-23 may regulate the recruitment/function of another cell type to the spleen. In this study, we show that specific depletion of neutrophils abrogated the differences in bacterial burdens in the livers but not the spleens of C57BL/6 (B6) and IL-23p19 KO mice. Interestingly, L. monocytogenes-infected IL-23p19 KO mice had fewer monocytes in the spleen than B6 mice, as well as a reduction in the monocyte-recruiting chemokines CCL2 and CCL7. Additionally, the overall concentrations of tumor necrosis factor alpha (TNF-α) and nitric oxide (NO(•)), as well as the percentages and total numbers of monocytes producing TNF-α and NO(•), were reduced in IL-23p19 KO mice compared to levels in B6 mice, leading to increased bacterial burdens in the spleens of L. monocytogenes-infected IL-23p19 KO mice. Collectively, our data establish that IL-23 is required for the optimal recruitment of TNF-α- and NO(•)-producing inflammatory monocytes, thus revealing a novel mechanism by which this proinflammatory cytokine provides protection against bacterial infection.

Homeostatic regulation of Salmonella-induced mucosal inflammation and injury by IL-23

IL-12 and IL-23 regulate innate and adaptive immunity to microbial pathogens through influencing the expression of IFN-γ, IL-17, and IL-22. Herein we define the roles of IL-12 and IL-23 in regulating host resistance and intestinal inflammation during acute Salmonella infection. We find that IL-23 alone is dispensable for protection against systemic spread of bacteria, but synergizes with IL-12 for optimal protection. IL-12 promotes the production of IFN-γ by NK cells, which is required for resistance against Salmonella and also for induction of intestinal inflammation and epithelial injury. In contrast, IL-23 controls the severity of inflammation by inhibiting IL-12A expression, reducing IFN-γ and preventing excessive mucosal injury. Our studies demonstrate that IL-23 is a homeostatic regulator of IL-12-dependent, IFN-γ-mediated intestinal inflammation.

Innate IL-17 and IL-22 responses to enteric bacterial pathogens

With the identification of T helper (Th)17 cells, a specific subset of CD4 T cells expressing interleukin (IL)-17 and IL-22, research on the function of these cytokines initially largely focused on traditional adaptive immune responses. However, IL-17 and IL-22 enhance basic innate barrier defenses at mucosal surfaces, such as antimicrobial peptide production and neutrophil recruitment; both events that occur rapidly and precede adaptive phase immunity. At the intestinal mucosal surface, it is now clear that innate lymphoid cells are also important sources of IL-17 and IL-22 during early phases of infection. Here, we discuss the function of innate IL-17- and IL-22-producing lymphocytes during enteric bacterial infection and their regulation by the intestinal microbiota, Toll-like receptors (TLRs) and Nod-like receptors (NLRs).

Protective immunity against mouse upper genital tract pathology correlates with high IFNγ but low IL-17 T cell and anti-secretion protein antibody responses induced by replicating chlamydial organisms in the airway

To search for optimal immunization conditions for inducing protective immunity against upper genital tract pathologies caused by chlamydial intravaginal infection, we compared protection efficacy in mice immunized intranasally or intramuscularly with live or inactivated Chlamydia muridarum organisms. Mice immunized intranasally with live organisms developed strong protection against both vaginal shedding of infectious organisms and upper genital tract pathologies. The protection correlated with a robust antigen-specific T cell response with high IFNγ but low IL-17. Although a significant level of IL-5 was also detected, these mice maintained an overall Th1-dorminant immunity following immunization and challenge infection. On the contrary, mice immunized intranasally with inactivated organisms or intramuscularly with live or inactivated organisms produced high levels of IL-17 and still developed significant upper genital tract pathologies. High titers of antibodies against chlamydial secretion antigens were detected only in mice immunized intranasally with live organisms but not mice in other groups, suggesting that the intranasally inoculated live organisms were able to undergo replication and immune responses to the chlamydial secretion proteins may contribute to protective immunity. These observations have provided important information on how to develop subunit vaccines for inducing protective immunity against urogenital infection with Chlamydia trachomatis organisms.

Enhanced virulence of Chlamydia muridarum respiratory infections in the absence of TLR2 activation

Chlamydia trachomatis is a common sexually transmitted pathogen and is associated with infant pneumonia. Data from the female mouse model of genital tract chlamydia infection suggests a requirement for TLR2-dependent signaling in the induction of inflammation and oviduct pathology. We hypothesized that the role of TLR2 in moderating mucosal inflammation is site specific. In order to investigate this, we infected mice via the intranasal route with C. muridarum and observed that in the absence of TLR2 activation, mice had more severe disease, higher lung cytokine levels, and an exaggerated influx of neutrophils and T-cells into the lungs. This could not be explained by impaired bacterial clearance as TLR2-deficient mice cleared the infection similar to controls. These data suggest that TLR2 has an anti-inflammatory function in the lung during Chlamydia infection, and that the role of TLR2 in mucosal inflammation varies at different mucosal surfaces.

Early MyD88-dependent induction of interleukin-17A expression during Salmonella colitis

The development of T helper 17 (T(H)17) cells is a well-established adaptive mechanism for the production of interleukin-17A (IL-17A), a cytokine involved in neutrophil recruitment. However, pathways contributing to mucosal expression of IL-17A during the initial phase of a bacterial infection have received less attention. Here we used the mouse colitis model of Salmonella enterica serotype Typhimurium infection to investigate the contribution of myeloid differentiation primary response protein 88 (MyD88) to inflammation and mucosal IL-17A expression. Expression of IL-23 in the cecal mucosa during S. Typhimurium colitis was dependent on the presence of MyD88. Furthermore, initial expression of IL-17A at 24 h after S. Typhimurium infection was dependent on MyD88 and the receptor for IL-1β. IL-23 and IL-1β synergized in inducing expression of IL-17A in splenic T cells in vitro. In the intestinal mucosa, IL-17A was produced by three distinct T cell populations, including δγ T cells, T(H)17 cells, and CD4(-)CD8(-) T cells. The absence of IL-1β signaling or IL-17 signaling reduced CXC chemokine expression but did not alter the overall severity of pathological lesions in the cecal mucosa. In contrast, cecal pathology and neutrophil recruitment were markedly reduced in Myd88-deficient mice during the initial phases of S. Typhimurium infection. Collectively, these data demonstrate that MyD88-dependent mechanisms, including an initial expression of IL-17A, are important for orchestrating early inflammatory responses during S. Typhimurium colitis.

IL-17 in protective immunity to intracellular pathogens

The identification of a new T cell subset referred to as T helper 17 (Th17) cells and its role in protective immunity against extracellular bacterial infections is well established. In contrast, initial studies suggested that the IL-23-IL-17 pathway was not required for protection against intracellular pathogens such as mycobacterial infections. However, recent studies demonstrate that Th17-IL-23 pathway may play a crucial role in protective immunity against other intracellular pathogens by regulating the innate and adaptive immune responses. The current outlook on the role of IL-23-IL-17 pathway in protective immunity to intracellular pathogens is discussed here.

Evaluation of a broadly protective Chlamydia-cholera combination vaccine candidate

The need to simultaneously target infections with epidemiological overlap in the population with a single vaccine provides the basis for developing combination vaccines. Vibrio cholerae ghosts (rVCG) offer an attractive approach for developing vaccines against a number of human and animal pathogens. In this study, we constructed a multisubunit vaccine candidate co-expressing the serovar D-derived Porin B and polymorphic membrane protein-D proteins of Chlamydia trachomatis and evaluated its ability to simultaneously induce broad-based chlamydial immunity and elicit a vibriocidal antibody response to the Vibrio carrier envelope. Intramuscular (IM) immunization with the vaccine candidate elicited high levels of antigen-specific genital mucosal and systemic Th1 cell-mediated and humoral immune responses against heterologous serovars and strains, including serovars E-H and L. Also, in addition to the multisubunit vaccine, the single subunit constructs conferred significant cross protection against the heterologous mouse strain, Chlamydia muridarum. Furthermore, all mice immunized with rVCG vaccine constructs responded with a significant rise in vibriocidal antibody titer, the surrogate marker for protection in cholera. These findings demonstrate the ability of the multisubunit vaccine to induce cross protective chlamydial as well as vibriocidal immunity and establish the possibility of developing a broadly efficacious Chlamydia-cholera combination vaccine.

The TLR7 ligand 9-benzyl-2-butoxy-8-hydroxy adenine inhibits IL-17 response by eliciting IL-10 and IL-10-inducing cytokines

This study evaluates the ability of a novel TLR7 ligand (9-benzyl-2-butoxy-8-hydroxy adenine, called SA-2) to affect IL-17 response. The SA-2 activity on the expression of IL-17A and IL-17-related molecules was evaluated in acute and chronic models of asthma as well as in in vivo and in vitro α-galactosyl ceramide (α-GalCer)-driven systems. SA-2 prepriming reduced neutrophils in bronchoalveolar lavage fluid and decreased methacoline-induced airway hyperresponsiveness in murine asthma models. These results were associated with the reduction of IL-17A (and type 2 cytokines) as well as of molecules favoring Th17 (and Th2) development in lung tissue. The IL-17A production in response to α-GalCer by spleen mononuclear cells was inhibited in vitro by the presence of SA-2. Reduced IL-17A (as well as IFN-γ and IL-13) serum levels in mice treated with α-GalCer plus SA-2 were also observed. The in vitro results indicated that IL-10 produced by B cells and IL-10-promoting molecules such as IFN-α and IL-27 by dendritic cells are the major player for SA-2-driven IL-17A (and also IFN-γ and IL-13) inhibition. The in vivo experiments with anti-cytokine receptor Abs provided evidence of an early IL-17A inhibition essentially due to IL-10 produced by resident peritoneal cells and of a delayed IL-17A inhibition sustained by IFN-α and IL-27, which in turn drive effector T cells to IL-10 production. These findings suggest that such TLR7 agonist downregulating Th17 (as well as Th2) response has to be considered a valid candidate for novel vaccine formulations in allergy.

Spontaneous secretion of interleukin-17 and -22 by human cervical cells in Chlamydia trachomatis infection

To investigate whether IL-17A (IL-17) and IL-22 are produced in response to Chlamydia trachomatis infection, the cervical washes of 27 women with C. trachomatis infection and 17 C. trachomatis negative controls were collected. The levels of cytokines were determined in the cervical wash and in the supernatant of cervical and systemic cell cultures upon C. trachomatis antigen stimulation. C. trachomatis infection appeared to activate local IL-17 and IL-22 production more efficiently than IFN-γ production. In the cervical wash of infected women, median concentrations of IL-17 and -22 were 5- and 3-fold higher, respectively, than in negative controls. The spontaneous intracellular expression of these cytokines was analysed by flow cytometry in blood and cervical cells and 26% of cervical mononuclear cells from infected women were shown to produce IL-22 and 12% to coproduce IL-17 and IL-22. In addition, it was demonstrated that 20-25% of IL-22 producing and IL-17-IL-22 coproducing cervical CD4+ T cells expressed the mucosal homing receptor CCR6. These results suggest that CCR6 is involved in the migration of these cells to the cervix and that IL-17 and IL-22 might play a role in the immune response at the site of C. trachomatis infection.

Nonhematopoietic cells are key players in innate control of bacterial airway infection

Airborne pathogens encounter several hurdles during host invasion, including alveolar macrophages (AMs) and airway epithelial cells (AECs) and their products. Although growing evidence indicates pathogen-sensing capacities of epithelial cells, the relative contribution of hematopoietic versus nonhematopoietic cells in the induction of an inflammatory response and their possible interplay is still poorly defined in vivo in the context of infections with pathogenic microorganisms. In this study, we show that nonhematopoietic cells, including AECs, are critical players in the inflammatory process induced upon airway infection with Legionella pneumophila, and that they are essential for control of bacterial infections. Lung parenchymal cells, including AECs, are not infected themselves by L. pneumophila in vivo but rather act as sensors and amplifiers of inflammatory cues delivered by L. pneumophila-infected AM. We identified AM-derived IL-1β as the critical mediator to induce chemokine production in nonhematopoietic cells in the lung, resulting in swift and robust recruitment of infection-controlling neutrophils into the airways. These data add a new level of complexity to the coordination of the innate immune response to L. pneumophila and illustrate how the cross talk between leukocytes and nonhematopoietic cells contributes to efficient host protection.

Early activation of the interleukin-23-17 axis in a murine model of oropharyngeal candidiasis

Candida albicans is an oral commensal yeast that causes oropharyngeal candidiasis (OPC) in immunocompromised individuals. The immunological pathways involved in OPC have been revisited after the interleukin-17 (IL-17) pathway was implicated in fungal immunity. We studied immediate (<24 h) and adaptive (3-6 day) IL-12 and IL-23-17 pathway activation in naive p40(-/-) mice, which lack IL-12 and IL-23 and develop severe, chronic OPC upon oral inoculation with C. albicans. Macrophages from p40(-/-) mice were less efficient than C57BL/6J controls at killing C. albicans in vitro but very low numbers in the oral mucosae of infected C57BL/6J mice suggest that they are not critical in vivo, at least in this strain. Migration of macrophages to regional lymph nodes of infected p40(-/-) mice was impaired; however, dendritic cell migration was not affected. Recombinant IL-12 therapy provided only temporary relief from OPC, suggesting that IL-23 is required for full protection. In C57BL/6J mice, but not p40(-/-) mice, messenger RNAs encoding IL-23p19 and IL-17 were induced in the oral mucosa within 24 h of infection (6 ± 0.6 and 12 ± 2.7-fold). By day 6 of infection in C57BL/6J mice, IL-17A messenger RNA level had increased 5.1 ± 1.8 and 83 ± 21-fold in regional lymph nodes and oral tissues respectively. Ablation of p40 was associated with delayed or abrogated induction of IL-17A pathway targets (monocyte chemoattractant protein-1, IL-6 and macrophage inflammatory protein-2), and a lack of organized recruitment of neutrophils to the infected oral mucosa. Overall our data show that the IL-23-17A axis is activated early in the oral mucosae of immunologically naive mice with OPC.

Interleukin-17 contributes to generation of Th1 immunity and neutrophil recruitment during Chlamydia muridarum genital tract infection but is not required for macrophage influx or normal resolution of infection

Interleukin 17 (IL-17) contributes to development of Th1 immunity and neutrophil influx during Chlamydia muridarum pulmonary infection, but its role during C. muridarum genital tract infection has not been described. We detected similar numbers of Chlamydia-specific Th17 and Th1 cells in iliac nodes of wild-type mice early during genital C. muridarum infection, while Th1 cells predominated later. il17ra(-/-) mice exhibited a reduced chlamydia-specific Th1 response in draining iliac nodes and decreased local IFN-γ production. Neutrophil influx into the genital tract was also decreased. However, il17ra(-/-) mice resolved infection normally, and no difference in pathology was observed compared to the wild type. Macrophage influx and tumor necrosis factor alpha (TNF-α) production were increased in il17ra(-/-) mice, providing a compensatory mechanism to effectively control chlamydial genital tract infection despite a reduced Th1 response. In ifnγ(-/-) mice, a marked increase in cellular infiltrates and chronic pathology was associated with an increased Th17 response. Although neutralization of IL-17 in ifnγ(-/-) mice decreased neutrophil influx, macrophage infiltration remained intact and the bacterial burden was not increased. Collectively, these results indicate that IL-17 contributes to the generation of Th1 immunity and neutrophil recruitment but is not required for macrophage influx or normal resolution of C. muridarum genital infection. These data highlight the redundant immune mechanisms operative at this mucosal site and the importance of examining site-specific responses to mucosal pathogens.

Towards a Chlamydia trachomatis vaccine: how close are we?

Chlamydia trachomatis is the leading cause of bacterial sexually transmitted infections and preventable blindness worldwide. The incidence of chlamydial sexually transmitted infections has increased rapidly and current antibiotic therapy has failed as an intervention strategy. The most accepted strategy for protection and/or control of chlamydial infections is a vaccine that induces both local neutralizing antibodies to prevent infections by the extracellular elementary bodies and a cell-mediated immune response to target the intracellular infection. This article will discuss the challenges in vaccine design for the prevention of chlamydial urogenital infection and/or disease, including selection of target antigens, discussion of effective delivery systems, immunization routes and adjuvants for induction of protective immunity at the targeted mucosal surface whilst minimizing severe inflammatory disease sequelae.

CD4+ and CD8+ T cell- and IL-17-mediated protection against Entamoeba histolytica induced by a recombinant vaccine

Amebiasis in the murine model can be prevented by vaccination with the Gal/GalNAc lectin through a T cell-dependent mechanism. In this work we further decipher the mechanism of this protection. Mice vaccinated with the recombinant "LecA" fragment of the Gal/GalNAc lectin with alum were capable of transferring protection to naïve recipients by both CD4+ T cells and surprisingly CD8+ T cells. We then examined the cytokine profile of these cells. CD4+ T cells from PBMC of LecA-alum vaccinated mice were observed to be a major source of IFN-γ, known to be a protective cytokine with this vaccine. In contrast, CD8+ T cells produced relatively little IFN-γ but more IL-17 than the CD4 compartment. We thus examined the role of IL-17 in vaccine mediated protection and found through neutralization experiments that this cytokine contributed to LecA-alum vaccine protection. In addition we examined whether these cells exhibited direct amebicidal activity in vitro and found that both populations had amebicidal activity at high concentrations (1000:1) but CD8+ T cells appeared more potent, capable of cytotoxicity at a 100:1 ratio. In conclusion, both CD4 and CD8 T cells exert protection with this amebiasis vaccine. The mechanism of CD8 T cell-mediated protection may include direct amebicidal activity and/or IL-17 production. Both IL-17 and IFN-γ are useful surrogates for immune protection.

MyD88 deficiency leads to decreased NK cell gamma interferon production and T cell recruitment during Chlamydia muridarum genital tract infection, but a predominant Th1 response and enhanced monocytic inflammation are associated with infection resolution

We have previously shown that MyD88 knockout (KO) mice exhibit delayed clearance of Chlamydia muridarum genital infection compared to wild-type (WT) mice. A blunted Th1 response and ineffective suppression of the Th2 response were also observed in MyD88 KO mice. The goal of the present study was to investigate specific mechanisms whereby absence of MyD88 leads to these effects and address the compensatory mechanisms in the genital tract that ultimately clear infection in the absence of MyD88. It was observed that NK cells recruited to the genital tract in MyD88 KO mice failed to produce gamma interferon (IFN-γ) mRNA and protein. This defect was associated with decreased local production of interleukin-17 (IL-17), IL-18, and tumor necrosis factor alpha (TNF-α) but normal levels of IL-12p70. Additionally, recruitment of CD4 T cells to the genital tract was reduced in MyD88 KO mice compared to that in WT mice. Although chronic infection in MyD88 KO mice resulted in oviduct pathology comparable to that of WT mice, increased histiocytic inflammation was observed in the uterine horns. This was associated with increased CCL2 levels and recruitment of macrophages as a potential compensatory mechanism. Further deletion of TLR4-TRIF signaling in MyD88 KO mice, using TLR4/MyD88 double-KO mice, did not further compromise host defense against chlamydiae, suggesting that compensatory mechanisms are Toll-like receptor (TLR) independent. Despite some polarization toward a Th2 response, a Th1 response remained predominant in the absence of MyD88, and it provided equivalent protection against a secondary infection as observed in WT mice.

The female lower genital tract is a privileged compartment with IL-10 producing dendritic cells and poor Th1 immunity following Chlamydia trachomatis infection

While a primary genital tract infection with C. trachomatis stimulates partial-protection against re-infection, it may also result in severe inflammation and tissue destruction. Here we have dissected whether functional compartments exist in the genital tract that restrict Th1-mediated protective immunity. Apart from the Th1-subset, little is known about the role of other CD4⁺ T cell subsets in response to a genital tract chlamydial infection. Therefore, we investigated CD4⁺ T cell subset differentiation in the genital tract using RT-PCR for expression of critical transcription factors and cytokines in the upper (UGT) and lower genital tract (LGT) of female C57BL/6 mice in response to C. trachomatis serovar D infection. We found that the Th1 subset dominated the UGT, as IFN-γ and T-bet mRNA expression were high, while GATA-3 was low following genital infection with C. trachomatis serovar D. By contrast, IL-10 and GATA-3 mRNA dominated the LGT, suggesting the presence of Th2 cells. These functional compartments also attracted regulatory T cells (Tregs) differently as increased FoxP3 mRNA expression was seen primarily in the UGT. Although IL-17A mRNA was somewhat up-regulated in the LGT, no significant change in RORγ-t mRNA expression was observed, suggesting no involvement of Th17 cells. The dichotomy between the LGT and UGT was maintained during infection by IL-10 because in IL-10-deficient mice the distinction between the two compartments was completely lost and a dramatic shift to the predominance of Th1 cells in the LGT occurred. Unexpectedly, the major source of IL-10 was CD11c⁺ CD11b⁺ DC, probably creating an anti-inflammatory privileged site in the LGT.

The immune response to the genital tract pathogen C. trachomatis can result in a number of pathological outcomes including tubal scarring and consequently, infertility. CD4⁺ T helper 1 (Th1) cells are critical for host protection against infection, but may also contribute to immunopathology. Apart from the Th1 cells, little is known about the role of other CD4⁺ T cell subsets in response to a genital tract chlamydial infection. By tracking the development of T helper cells in the genital tract using RT-PCR for distinct transcription factors associated with these subsets, we found vastly different immune responses in the upper genital tract (UGT) compared to the lower genital tract (LGT) of female mice during infection. The LGT was dominated by anti-inflammatory IL-10 production from dendritic cells (DC) and the non-protective Th2 subset. In contrast, the upper genital tract was populated by protective-Th1 cells. In the absence of IL-10, though, the LGT and UGT were both dominated by Th1 cells, arguing that DC-derived IL-10 secures an anti-inflammatory privileged site in the LGT. These findings provide a break-through in our understanding of functional compartments in the genital tract immune system with potentially strong impact on vaccine development.

MyD88 signaling is indispensable for primary influenza A virus infection but dispensable for secondary infection

Recent studies have revealed that innate immunity is involved in the development of adaptive immune responses; however, its role in protection is not clear. In order to elucidate the exact role of Toll-like receptor (TLR) or RIG-I-like receptor (RLR) signaling on immunogenicity and protective efficacy against influenza A virus infection (A/PR/8/34 [PR8]; H1N1), we adapted several innate signal-deficient mice (e.g., TRIF(-/-), MyD88(-/-), MyD88(-/-) TRIF(-/-), TLR3(-/-) TLR7(-/-), and IPS-1(-/-)). In this study, we found that MyD88 signaling was required for recruitment of CD11b(+) granulocytes, production of early inflammatory cytokines, optimal proliferation of CD4 T cells, and production of Th1 cytokines by T cells. However, PR8 virus-specific IgG and IgA antibody levels in both systemic and mucosal compartments were normal in TLR- and RLR-deficient mice. To further assess the susceptibility of these mice to influenza virus infection, protective efficacy was determined after primary or secondary lethal challenge. We found that MyD88(-/-) and MyD88(-/-) TRIF(-/-) mice were more susceptible to primary influenza virus infection than the B6 mice but were fully protected against homologous (H1N1) and heterosubtypic (H5N2) secondary infection when primed with a nonlethal dose of PR8 virus. Taken together, these results show that MyD88 signaling plays an important role for resisting primary influenza virus infection but is dispensable for protection against a secondary lethal challenge.

Molecular immune responses to aerosol challenge with Francisella tularensis in mice inoculated with live vaccine candidates of varying efficacy

Background

Francisella tularensis is a facultative intracellular bacterial pathogen and the etiological agent of tularemia. The subspecies F. tularensis tularensis is especially virulent for humans when inhaled and respiratory tularemia is associated with high mortality if not promptly treated. A live vaccine strain (LVS) derived from the less virulent holarctica subspecies confers incomplete protection against aerosol challenge with subsp. tularensis. Moreover, correlates of protection have not been established for LVS.

Methodology/Principal Findings

In the present study we compare molecular immune responses elicited by LVS and two defined deletion mutants of clinical subsp. tularensis strain, SCHU S4, that confer enhanced protection in a mouse model. BALB/c mice were immunized intradermally then challenged with an aerosol of SCHU S4 six weeks later. Changes in the levels of a selected panel of cytokines and chemokines were examined in the lungs, spleens, and sera of vaccinated and challenged mice. Mostly, increased cytokine and chemokine levels correlated with increased bacterial burden. However, after adjusting for this variable, immunization with either of the two Schu S4 mutants resulted in higher levels of several pulmonary cytokines, versus those resulting after LVS immunization, including IL-17. Moreover, treatment of mice immunized with ΔclpB with anti-IL-17 antibodies post-challenge enhanced lung infection.

Conclusions/Significance

This is the first report characterizing local and systemic cytokine and chemokine responses in mice immunized with vaccines with different efficacies against aerosol challenge with virulent F. tularensis subsp. tularensis. It shows that increases in the levels of most of these immunomodulators, including those known to be critical for protective immunity, do not superficially correlate with protection unless adjusted for the effects of bacterial burden. Additionally, several cytokines were selectively suppressed in the lungs of naïve mice, suggesting that one mechanism of vaccine action is to overcome this pathogen-induced immunosuppression.

IL-17A is proatherogenic in high-fat diet-induced and Chlamydia pneumoniae infection-accelerated atherosclerosis in mice

The role of IL-17 in atherogenesis remains controversial. We previously reported that the TLR/MyD88 signaling pathway plays an important role in high-fat diet as well as Chlamydophila pneumoniae infection-mediated acceleration of atherosclerosis in apolipoprotein E-deficient mice. In this study, we investigated the role of the IL-17A in high-fat diet (HFD)- and C. pneumoniae-induced acceleration of atherosclerosis. The aortic sinus plaque and aortic lesion size and lipid composition as well as macrophage accumulation in the lesions were significantly diminished in IL-17A(-/-) mice fed an HFD compared with wild-type (WT) C57BL/6 control mice. As expected, C. pneumoniae infection led to a significant increase in size and lipid content of the atherosclerotic lesions in WT mice. However, IL-17A(-/-) mice developed significantly less acceleration of lesion size following C. pneumoniae infection compared with WT control despite similar levels of blood cholesterol levels. Furthermore, C. pneumoniae infection in WT but not in IL-17A(-/-) mice was associated with significant increases in serum concentrations of IL-12p40, CCL2, IFN-γ, and numbers of macrophages in their plaques. Additionally, in vitro studies suggest that IL-17A activates vascular endothelial cells, which secrete cytokines that in turn enhance foam cell formation in macrophages. Taken together, our data suggest that IL-17A is proatherogenic and that it plays an important role in both diet-induced atherosclerotic lesion development, and C. pneumoniae infection-mediated acceleration of atherosclerotic lesions in the presence of HFD.

Th17 cells, HIV and the gut mucosal barrier

PURPOSE OF REVIEW

We will present recent studies on a subset of CD4 T helper cells, Th17 cells, that appears to be critical for regulating gut mucosal immune responses against extracellular microbial pathogens and may serve as a link between innate and adaptive immune responses. Implications of the loss of Th17 CD4 T cells in HIV infection will be discussed in relation to the chronic immune activation and HIV pathogenesis.

RECENT FINDINGS

Severe depletion of CD4 T cells occurs in the gut mucosa during primary HIV and simian immunodeficiency virus infections. A pronounced loss of mucosal Th17 CD4 T cells in the simian immunodeficiency virus-infected rhesus macaque model of AIDS is linked to impaired immune responses in the gut mucosa to an enteric pathogen, Salmonella typhimurium, leading to the lack of local control of the pathogen and its translocation. Recovery of the gut mucosal immune system during highly active antiretroviral therapy is slow and incomplete compared with the peripheral blood compartment. Recent studies suggest that the replenishment of Th17 CD4 T cells in the gut mucosa during highly active antiretroviral therapy, or during nonpathogenic simian immunodeficiency virus infections in the nonhuman primate models, correlates with better restoration and function of the gut mucosal immune system.

SUMMARY

A better understanding of the role of Th17 CD4 cells in the generation of mucosal immune responses to enteric pathogens and maintenance of the intestinal epithelial integrity in HIV-infected patients will help in the development of novel strategies to modulate and enhance mucosal immune system and its function.

The role of TLR2, TRL3, TRL4, and TRL9 signaling in the pathogenesis of autoimmune disease in a retinal autoimmunity model

PURPOSE

Induction of tissue-specific experimental autoimmune diseases involves the use of complete Freund adjuvant containing Mycobacterium tuberculosis, whose recognition by the innate immune system depends on Toll-like receptors (TLRs) that signal through the adaptor molecule MyD88. The authors' previous study showed that MyD88(-/-) mice, but not TLR2(-/-), TLR4(-/-), or TLR9(-/-) mice, were resistant to experimental autoimmune uveitis (EAU).

METHODS

The EAU induction in mice deficient in TLR3 or mice double deficient in TLR2+4, TLR2+9, and TLR4+9 was examined and the role of the TLR agonists in the adjuvant effect involved in the induction of EAU was assessed.

RESULTS

TLR3-deficient and TLR2+4, TLR2+9, and TLR4+9 double-deficient mice were as susceptible to EAU as their control littermates. However, in mice immunized with a low-dose EAU regimen, TLR4 agonist lipopolysaccharide (LPS) enhanced EAU scores, delayed-type hypersensitivity responses, and antigen-specific T-cell proliferation. Antigen-specific IL-17 and IFN-gamma production by T lymphocytes was markedly increased in the LPS-treated group. The effects of LPS on EAU were abolished by treatment with an LPS deactivator polymyxin B. Inclusion of agonists for TLR2, TRL3, or TRL9 in immunization also enhanced EAU scores.

CONCLUSIONS

These results suggest that signaling of TLR2, TRL3, TRL4, and TRL9 is highly redundant in the adjuvant effect needed to induce EAU and that diverse microbial infections may contribute to the pathogenesis of diseases such as uveitis.

Interleukin-17 and its target genes: mechanisms of interleukin-17 function in disease

Interleukin-17 (IL-17) has emerged as a central player in the mammalian immune system. Although this cytokine exerts a host-defensive role in many infectious diseases, it promotes inflammatory pathology in autoimmunity and other settings. A myriad of studies have focused on how IL-17-producing cells are generated. However, the means by which IL-17 achieves its effects, either for the benefit or the detriment of the host, are due in large part to the induction of new gene expression. Whereas many IL-17 target genes are common to different disease states, in some cases the effects of IL-17 differ depending on the target cell, infectious site or pathogen. Gene products induced by IL-17 include cytokines (IL-6, granulocyte-colony-stimulating factor, tumour necrosis factor-alpha), chemokines (CXCL1, CXCL2, CCL20, among many others), inflammatory effectors (acute-phase protesins, complement) and antimicrobial proteins (defensins, mucins). Different cell types appear to respond differently to IL-17 in terms of target gene expression, with notable differences seen in mesenchymal and epithelial cells compared with cells of haematopoietic origin. Here, we summarize the major IL-17 target genes that mediate this cytokine's activities in both autoimmune and chronic diseases as well as during various types of infections.

Chlamydial infection of monocytes stimulates IL-1beta secretion through activation of the NLRP3 inflammasome

Chlamydia trachomatis infections represent the leading cause of bacterial sexually-transmitted disease in the United States and can cause serious tissue damage leading to infertility and ectopic pregnancies in women. Inflammation and hence the innate immune response to chlamydial infection contributes significantly to tissue damage, particularly by secreting proinflammatory cytokines such as interleukin (IL)-1beta from monocytes, macrophages and dendritic cells. Here we demonstrate that C. trachomatis or Chlamydia muridarum infection of a monocytic cell line leads to caspase-1 activation and IL-1beta secretion through a process requiring the NLRP3 inflammasome. Thus, secretion of IL-1beta decreased significantly when cells were depleted of NLRP3 or treated with the anti-inflammatory inhibitors parthenolide or Bay 11-7082, which inhibit inflammasomes and the transcription factor NF-kappaB. As for other infections causing NRLP3 inflammasome assembly, caspase-1 activation in monocytes is triggered by potassium efflux and reactive oxygen species production. However, anti-oxidants inhibited IL-1beta secretion only partially. Atypically for a bacterial infection, caspase-1 activation during chlamydial infection also involves partially the spleen tyrosine kinase (Syk), which is usually associated with a pathogen recognition receptor for fungal pathogens. Secretion of IL-1beta during infection by many bacteria requires both microbial products from the pathogen and an exogenous danger signal, but chlamydial infection provides both the pathogen-associated molecular patterns and danger signals necessary for IL-1beta synthesis and its secretion from human monocytes. Use of inhibitors that target the inflammasome in animals should therefore dampen inflammation during chlamydial infection.

Chlamydia muridarum T-cell antigens formulated with the adjuvant DDA/TDB induce immunity against infection that correlates with a high frequency of gamma interferon (IFN-gamma)/tumor necrosis factor alpha and IFN-gamma/interleukin-17 double-positive CD4+ T cells

Major impediments to developing a Chlamydia vaccine lie in identifying immunologically relevant T-cell antigens and delivery in a manner to stimulate protective immunity. Using an immunoproteomic approach, we previously identified three immunodominant Chlamydia T-cell antigens (PmpG-1, PmpE/F-2, and RplF). Because RplF has high homology to a human ortholog, it may not be suitable for human vaccine development. Therefore, in this study, we evaluated protection against Chlamydia infection in the genital tract in C57BL/6 mice immunized with Chlamydia-specific membrane proteins PmpG-1, PmpE/F-2, and major outer membrane protein (MOMP; as a reference) or a combination of them formulated with one of three adjuvants, CpG oligodeoxynucleotide (CpG-ODN), AbISCO-100 (AbISCO), or DDA/TDB (dimethyldioctadecylammonium bromide/D-(+)-trehalose 6,6'-dibehenate). The results show that immunization with the CpG-ODN formulation failed to provide protection against Chlamydia infection; the AbISCO formulation conferred moderate protection, and the DDA/TDB formulation showed the highest degree of protective efficacy. The combination of PmpG-1, PmpE/F-2, and MOMP proteins formulated with DDA/TDB exhibited the greatest degree of protection among all vaccine groups studied. Moreover, this vaccine combination also engendered significant protection in BALB/c mice, which have a different major histocompatibility complex (MHC) background. We measured cell-mediated immune cytokine responses in mice immunized with PmpG-1 mixed with each of the three adjuvants. The results demonstrate that mice immunized with the DDA/TDB formulation induced the strongest gamma interferon (IFN-gamma) and interleukin-17 (IL-17) responses, characterized by the highest frequency of IFN-gamma/tumor necrosis factor alpha (TNF-alpha) and IFN-gamma/IL-17 double-positive CD4(+) T cells. In conclusion, a Chlamydia vaccine based on the recombinant proteins PmpG-1, PmpE/F-2, and MOMP delivered in a DDA/TDB adjuvant conferred protection against infection that correlated with IFN-gamma/TNF-alpha and IFN-gamma/IL-17 double-positive CD4(+) T cells.

Th17 cytokines in mucosal immunity and inflammation

PURPOSE OF REVIEW

Compelling evidence suggests that the Th17 lineage and other IL-17-producing cells play critical roles in host defense against pathogens at mucosal sites. However, IL-17 can also contribute to inflammatory responses at mucosal sites. In this review, we will discuss the recent progress in our understanding of the role of Th17 and other IL-17-producing cells in defining the fine balance between immunity and inflammation at different mucosal sites. RECENT FNDINGS: Recent findings have highlighted that Th17 cytokines are important for the induction of innate and adaptive host responses and contribute to host defense against pathogens at mucosal sites. More recent developments have probed how the Th17 responses are generated in vivo in response to infections and their requirement in maintaining barrier function at mucosal sites. Most importantly, it is becoming apparent that there is a fine balance between protective and pathological manifestation of Th17 responses at mucosal sites that defines immunity or inflammation.

SUMMARY

In this review, we have summarized the recent advances in our understanding of Th17 cytokines and how they contribute to immunity versus inflammation at mucosal sites.

The innate immune response to uropathogenic Escherichia coli involves IL-17A in a murine model of urinary tract infection

Uropathogenic Escherichia coli is the causative agent for >80% of uncomplicated urinary tract infections (UTIs). Uropathogenic E. coli strains express a number of virulence and fitness factors that allow successful colonization of the mammalian bladder. To combat this, the host has distinct mechanisms to prevent adherence to the bladder wall and to detect and kill uropathogenic E. coli in the event of colonization. In this study, we investigated the role of IL-17A, an innate-adaptive immunomodulatory cytokine, during UTI using a murine model. Splenocytes isolated from mice infected by the transurethral route robustly expressed IL-17A in response to in vitro stimulation with uropathogenic E. coli Ags. Transcript expression of IL-17A in the bladders of infected mice correlated with a role in the innate immune response to UTI, and gammadelta cells seem to be a key source of IL-17A production. Although IL-17A seems to be dispensable for the generation of a protective response to uropathogenic E. coli, its importance in innate immunity is demonstrated by a defect in acute clearance of uropathogenic E. coli in IL-17A(-/-) mice. This clearance defect is likely a result of deficient cytokine and chemokine transcripts and impaired macrophage and neutrophil influx during infection. These results show that IL-17A is a key mediator for the innate immune response to UTIs.

Precarious balance: Th17 cells in host defense

Lineage-specific responses from the effector T-cell repertoire form a critical component of adaptive immunity. The recent identification of Th17 cells-a third, distinct lineage of helper T cells-collapses the long-accepted paradigm in which Th1 and Th2 cells distinctly mediate cellular and humoral immunity, respectively. In this minireview, we discuss the involvement of the Th17 lineage during infection by extracellular bacteria, intracellular bacteria, and fungi. Emerging trends suggest that the Th17 population bridges innate and adaptive immunity to produce a robust antimicrobial inflammatory response. However, because Th17 cells mediate both host defense and pathological inflammation, elucidation of mechanisms that attenuate but do not completely abolish the Th17 response may have powerful implications for therapy.

Modulation of cytokines and transcription factors (T-Bet and GATA3) in CD4 enriched cervical cells of Chlamydia trachomatis infected fertile and infertile women upon stimulation with chlamydial inclusion membrane proteins B and C

BACKGROUND

Chlamydial Inclusion membrane proteins (Incs), are involved in biochemical interactions with host cells and infecting Chlamydiae. We have previously reported the role of two Chlamydia trachomatis (CT) Incs, namely IncB and IncC in generating host immunity in CT infected women. Emerging data shows involvement of Inc stimulated CD4 positive T cells in aiding host immunity in infected fertile and infertile women through the secretion of interferon gamma. However the lack of data on the intra-cytokine interplay to these Incs in infected cell milieu prompted us to investigate further.

METHODS

A total of 14 CT-positive fertile, 18 CT-positive infertile women and 25 uninfected controls were enrolled in this study. CD8 depleted, CD4 enriched cervical cells were isolated and upon stimulation with IncB and IncC, modulation of cytokines (Interleukin (IL)-1 Beta, IL-4, IL-5, IL-6, IL-10, Interferon-gamma, IL-12, IL-23, Tumor Necrosis Factor-alpha and Granulocyte macrophage colony-stimulating factor (GM-CSF) and T cell lineage regulating transcription factors T-Bet and GATA3 was determined by real-time reverse-transcriptase (RT)-PCR and ELISA.

RESULTS

Significant higher expression (P < 0.05) of Interferon-gamma, IL-12, IL-23 and GM-CSF were found in Inc-stimulated CD4 enriched cervical cells of CT-positive fertile women and contrastingly high IL-1 Beta, IL-4, IL-5, IL-6 and IL-10 levels were found in CT-positive infertile women. Positive correlation (P < 0.05) was found between Interferon-gamma and T-Bet levels in CT-positive fertile women and IL-4 mRNA and GATA3 levels in CT-positive infertile patients upon IncB and IncC stimulation.

CONCLUSION

Overall our data shows that CT IncB and IncC are able to upregulate expression of cytokines, namely interferon-gamma, IL-12, IL-23 and GM-CSF in CT-positive fertile women while expression of IL-1 Beta, IL-4, IL-5, IL-6 and IL-10 were upregulated in CT-positive infertile women. Our study also suggests that Incs are able to modulate expression of T cell lineage determinants indicating their involvement in regulation of immune cells.