Regulatory effects of IL-15 on allergen-induced airway obstruction

BACKGROUND

Airway obstruction is a physiologic feature of asthma, and IL-15 might have an important role in asthma pathogenesis.

OBJECTIVE

We tested the hypothesis that regulation of IL-15 is critical for preservation of allergen-induced airway hyperresponsiveness (AHR), airway resistance, and compliance in response to methacholine.

METHODS

Airway inflammation, AHR, resistance, and compliance were assessed in Il15 gene-deficient mice and IL-15-overexpressing mice in an allergen-induced murine model of asthma. We assessed eosinophil numbers by using anti-major basic protein immunostaining, goblet cell hyperplasia by using periodic acid-Schiff staining, and cytokine and chemokine levels by performing quantitative PCR and ELISA.

RESULTS

We made a novel observation that IL-15 deficiency promotes baseline airway resistance in naive mice. Moreover, rIL-15 delivery to the lung downregulates expression of proinflammatory cytokines and improves allergen-induced AHR, airway resistance, and compliance. These observations were further validated in doxycycline-inducible CC10-IL-15 bitransgenic mice. Doxycycline-exposed, Aspergillus species extract-challenged CC10-IL-15 bitransgenic mice exhibited significantly reduced levels of proinflammatory cytokines (IL-4, IL-5, and IL-13) and decreased goblet cell hyperplasia. Airway obstruction, including AHR and airway resistance, was diminished in allergen-challenged doxycycline-exposed compared with non-doxycycline-exposed CC10-IL-15 bitransgenic mice. Mechanistically, we observed that IL-15-mediated protection of airway obstruction is associated with induced IFN-γ- and IL-10-producing regulatory CD4+CD25+ forkhead box p3 (Foxp3)+ T cells. Additionally, we found that a human IL-15 agonist (ALT-803) improved airway resistance and compliance in an experimental asthma model.

CONCLUSION

We report our novel finding that IL-15 has a potent inhibitory effect on the airway obstruction that occurs in response to environmental allergens.

Airway Epithelial KIF3A Regulates Th2 Responses to Aeroallergens

KIF3A, the gene encoding kinesin family member 3A, is a susceptibility gene locus associated with asthma; however, mechanisms by which KIF3A might influence the pathogenesis of the disorder are unknown. In this study, we deleted the mouse Kif3a gene in airway epithelial cells. Both homozygous and heterozygous Kif3a gene-deleted mice were highly susceptible to aeroallergens from Aspergillus fumigatus and the house dust mite, resulting in an asthma-like pathology characterized by increased goblet cell metaplasia, airway hyperresponsiveness, and Th2-mediated inflammation. Deletion of the Kif3a gene increased the severity of pulmonary eosinophilic inflammation and expression of cytokines (Il-4, Il-13, and Il-17a) and chemokine (Ccl11) RNAs following pulmonary exposure to Aspergillus extract. Inhibition of Kif3a disrupted the structure of motile cilia and impaired mucociliary clearance, barrier function, and epithelial repair, demonstrating additional mechanisms by which deficiency of KIF3A in respiratory epithelial cells contributes to pulmonary pathology. Airway epithelial KIF3A suppresses Th2 pulmonary inflammation and airway hyperresponsiveness following aeroallergen exposure, implicating epithelial microtubular functions in the pathogenesis of Th2-mediated lung pathology.

Significance of IL-15 in IL-4 induced B cell activation, immunoglobulin isotype class switching and IgE production (IRM10P.613)

IgE-mediated immune responses contribute to the pathogenesis of allergic diseases. Despite their significant role in immune biology, the factors that produce and regulate IgE responses are yet to be established. Notably, IL-4 is a well-established cytokine involved in immunoglobulin (Ig) isotype class switching and IgE production. However we recently observed that IL-15 over expression in mice (pharmacologically or by transgene insertion) induces IgE levels. Therefore we hypothesized that IL-15 might have some role in B cells proliferation, activation, Ig isotype class switching and IgE production. Accordingly we examined the level of IgE, B cells and Ig isotype class switching in response to IL-15 using ELISA, real time qPCR and flowcytometric analysis. Our initial in vitro data show proliferation, activation and induced Ig class switching genes in purified B cells following rIL-15 treatments. Further, we show reduced IgE levels in IL-15 gene-deficient mice compared to Balbc mice following Aspergillus fumigatus exposure. Furthermore we examined the role of IL-15 in IL-4 mediated IgE production. We observed that IL-4 gene-deficient mice have increased IgE levels and B cell activation following intravenous administration of IL-15 compared to saline. However, significant IgE levels were observed following IL-15 treatment in Balbc mice compared to IL-4 gene-deficient mice.Together we conclude that IL-15 is required for the IL-4 induced B cell activation and allergen induced IgE.

Airway epithelial SPDEF integrates goblet cell differentiation and pulmonary Th2 inflammation

Epithelial cells that line the conducting airways provide the initial barrier and innate immune responses to the abundant particles, microbes, and allergens that are inhaled throughout life. The transcription factors SPDEF and FOXA3 are both selectively expressed in epithelial cells lining the conducting airways, where they regulate goblet cell differentiation and mucus production. Moreover, these transcription factors are upregulated in chronic lung disorders, including asthma. Here, we show that expression of SPDEF or FOXA3 in airway epithelial cells in neonatal mice caused goblet cell differentiation, spontaneous eosinophilic inflammation, and airway hyperresponsiveness to methacholine. SPDEF expression promoted DC recruitment and activation in association with induction of Il33, Csf2, thymic stromal lymphopoietin (Tslp), and Ccl20 transcripts. Increased Il4, Il13, Ccl17, and Il25 expression was accompanied by recruitment of Th2 lymphocytes, group 2 innate lymphoid cells, and eosinophils to the lung. SPDEF was required for goblet cell differentiation and pulmonary Th2 inflammation in response to house dust mite (HDM) extract, as both were decreased in neonatal and adult Spdef(-/-) mice compared with control animals. Together, our results indicate that SPDEF causes goblet cell differentiation and Th2 inflammation during postnatal development and is required for goblet cell metaplasia and normal Th2 inflammatory responses to HDM aeroallergen.

Involvement of interleukin-18 in the pathogenesis of human eosinophilic esophagitis

IL-18 is induced in food allergy and EoE is food allergen-induced disease. Therefore, we tested the hypothesis whether IL-18 is involved in food allergen-induced EoE pathogenesis. Accordingly, we examined normal SPT+ and SPT- EoE patient blood and biopsy samples for IL-18, IL-18Rα, ICAM and VCAM expression. Herein, we show increased IL-18 level is highly significant in food allergen SPT+ compared to SPT- EoE patients. We also report that IL-18Rα+ cells and mRNA levels are induced in the esophageal biopsies of EoE patients and blood IL-18 levels correlate with esophageal eosinophilia (P<0.01). Additionally, we report that the levels of esophageal eosinophil and mast cells correlate with ICAM expression in human EoE. Mechanistically, we show that IL-18 in vitro stimulates iNKT cells and endothelial cells and induce eosinophil active cytokines IL-5 and IL-13. We provide the evidence that IL-18 is critical cytokine involved in activation of iNKT cells and ICAM in promoting human EoE.

Invariant natural killer T-cell neutralization is a possible novel therapy for human eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a recently recognized inflammatory disorder that needs a potential therapeutic strategy. We earlier showed that iNKT cell-deficient mice are protected from allergen-induced EoE. Therefore, we now tested the hypothesis that iNKT cells are induced in the human EoE and is a novel possible target for the treatment of human EoE. Accordingly, we examine number of iNKT cells and eosinophils and expression of iNKT-associated cell surface receptors and chemokines by performing immunofluorescence, qPCR and ELISA in the esophageal biopsies and blood samples of normal subjects (comparison control) and EoE patients. Herein, we show that iNKT cell number, their receptor subcomponents Vα24 and Vβ11 expression, and associated chemokine CXCL16 levels (or expression) are induced significantly in EoE patients compared with normal individuals. In addition, we show that CXCL16 levels (or expression) correlate with the mRNA levels of Vα24 receptor but not well with esophageal eosinophilia in human EoE. Of note, we show that in vivo activation of iNKT cells is sufficient to induce EoE in mice. Furthermore, we show that anti-mCD1d- and anti-hVα24Jα18-neutralizing antibody treatment protects allergen-induced experimental EoE. Taken together, we have shown first time that iNKT cells have a critical pathogenic role in human and experimental EoE. iNKT cell neutralization by humanized anti-CD1d and anti-Vα24Jα18 antibodies might be a novel and potential therapy for human EoE.

A Correlation between Phagocytosis and Apoptosis in THP-1 Cells Infected with Prevalent Strains ofMycobacterium tuberculosis

The innate ability of infected macrophages to undergo programmed cell death (apoptosis) and curtail the infection is crucial for the host defense. Although phagocytosis and intracellular killing mechanisms leading to apoptosis in macrophages are highly effective in eliminating the infecting tuberculous bacilli, some Mycobacterium tuberculosis(Mtb) strains have evolved strategies to inhibit this microbicidal function and make use of macrophage for its successful and prolonged survival. Two clinical strains of Mtb (S7 and S10) found to be prevalent and primitive, based on molecular epidemiological studies, were used to study the magnitude in induction of apoptosis in THP-1 cells at various time points of infection and to correlate it with phagocytosis. The percentage of phagocytosis did not show any strain-specific association with differentiated THP-1 cells. But in the phagocytic index, the clinical strains showed a low dose of infection in the 1-10 bacilli category thereby exerting less burden on the cells. The induction of apoptosis was strain dependent. The THP-1 cells infected with H37Ra and S10 showed an increase in apoptosis at all time points while the S7 strain induced minimum apoptosis. A negative correlation between apoptosis and phagocytic index was observed in the 1-10 category and a positive correlation in the > 20 category of the phagocytic index. This novel observation indicates that the magnitude of THP-1 cell apoptosis is a function of the number of internalized mycobacteria. These results indicated a differential mode of infection by clinical strains and their adaptation to different survival strategies that may lead to immune suppression and pathogenesis of the disease.

Esophageal functional impairments in experimental eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is an emerging chronic esophageal disease. Despite the increasing diagnosis of EoE globally, the causes of EoE and other esophageal eosinophilic disorders are not clearly understood. EoE pathology includes accumulation of inflammatory cells (e.g., eosinophils, mast cells), characteristic endoscopic features (e.g., furrows, the formation of fine concentric mucosal rings, exudates), and functional impairments (e.g., esophageal stricture, dysmotility). We hypothesized that the esophageal structural pathology and functional impairments of EoE develop as a consequence of the effector functions of the accumulated inflammatory cells. We analyzed eosinophils (anti-major basic protein immunostaining), esophageal stricture (X-ray barium swallowing), and esophageal motility (isometric force) in two established transgenic murine models of EoE (CD2-IL-5 and rtTA-CC10-IL-13) and a novel eosinophil-deficient model (ΔdblGATA/CD2-IL-5). Herein, we show the following: 1) CD2-IL-5 and doxycycline (DOX)-induced rtTA-CC10-IL-13 mice have chronic eosinophilic and mast cell esophageal inflammation; 2) eosinophilic esophageal inflammation promotes esophageal stricture in both transgenic murine models; 3) the eosinophil-deficient ΔdblGATA/CD-2-IL-5 mice were protected from the induction of stricture, whereas the eosinophil-competent CD2-IL-5 mice develop esophageal stricture; 4) esophageal stricture is not reversible in DOX-induced rtTA-CC10-IL-13 mice (8 wk DOX followed by 8 wk no-DOX); and 5) IL-5 transgene-induced (CD2-IL-5) EoE evidences esophageal dysmotility (relaxation and contraction) that is independent of the eosinophilic esophageal inflammation: CD2-IL-5 and ΔdblGATA/CD2-IL-5 mice have comparable esophageal dysmotility. Collectively, our present study directly implicates chronic eosinophilic inflammation in the development of the esophageal structural impairments of experimental EoE.

An assessment of opinion of Indian physicians about emergency medicine in India

BACKGROUND

Emergency medicine (EM) has recently been recognized as a specialty in India and formal training programmes are yet to be developed.

METHODS

A survey was devised to elicit the opinion of recently graduated physicians in Chennai, India about EM as well as about the current state of EM in India. A convenience sample of 130 respondents filled out a 21-question survey.

RESULTS

Ninety-four per cent of respondents stated that EM was essential for providing quality healthcare; 94% of respondents felt there needs to be a change in emergency departments in India, with only 20% stating they were proud of the emergency departments in India. Seventy-six per cent of respondents were more likely to consider EM if the specialty was recognized by the Medical Council of India and 76% were inclined to pursue the specialty if there were more training programmes.

CONCLUSION

Recently graduated physicians found flaws in the current state of emergency care in India; however, overall they remain interested in the field of EM.

Significance of para-esophageal lymph nodes in food or aeroallergen-induced iNKT cell-mediated experimental eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a recently recognized inflammatory disorder driven by food hypersensitivity; however, the specific foods and mechanisms involved are unclear. In patients with EoE, we have found that hypersensitivities to corn and peanuts are the most common. Accordingly, we sensitized and exposed mice either intranasally or intragastrically with corn or peanut extract or saline. Esophageal eosinophilia, the genes of eosinophil-directed cytokines, and allergen-induced antibodies were examined in mice challenged with corn or peanut extract or saline. A high number of esophageal lamina propria eosinophils as well as eosinophilic microabscesses, intraepithelial eosinophils, extracellular eosinophilic granules, thickened and disrupted epithelial mucosa, and mast cell hyperplasia were observed in the esophagus of peanut or corn allergen-challenged mice. Mechanistic analysis indicated that para-esophageal lymph nodes might be critical in the trafficking of eosinophils to the esophagus and in EoE association to airway eosinophilia. Furthermore, experimentation with gene-targeted mice revealed that peanut allergen-induced EoE was dependent on eotaxin and invariant natural killer T (iNKT) cells, as CD1d and eotaxin-1/2 gene-deficient mice were protected from disease induction. Thus we provide evidence that para-esophageal lymph nodes are involved in food- or aeroallergen-induced eosinophilia and patchy EoE pathogenesis, likely a mechanism dependent on eotaxins and iNKT cells.

An essential role of invariant natural killer T cells in the pathogenesis of eosinophilic esophagitis (59.1)

Experimental eosinophilic esophagitis (EE) is a recently described chronic allergic inflammatory disorder whose basic pathogenesis is not well understood. Herein, we focus on the hypothesis that iNKT cell responses are essential for the initiation and progression of EE. We show that iNKT cells and their specific chemokine CXCL16 are induced in human and experimental EE. CXCL16 is primarily derived from esophageal epithelial cells and correlates with the levels of esophageal eosinophils. Notably, iNKT cell-deficient CD1d-null mice are protected from the induction of experimental EE; whereas, NK cell depleted mice exhibit full disease following allergen challenge. Interestingly, in vivo activation of human iNKT cells by the α-galactosylceramide analog PBS57 is sufficient to induce esophageal eosinophilia. Mechanistically, PBS57 exposed human iNKT cells produce IL-5 and IL-13 via STAT5 activation. Taken together, these findings provide evidence that iNKT cells have an essential pathogenic role in the initiation and progression of human and experimental EE, providing new opportunities for therapeutic strategies.

Gender-dependent expression of murine Irf5 gene: implications for sex bias in autoimmunity

Molecular mechanisms that contribute to sex bias in the development of systemic lupus erythematosus (SLE), an autoimmune disease, remain unknown. We found that the expression levels of interferon regulatory factor 5 (IRF5), a lupus susceptibility factor, depend on gender of mice. We found that steady-state levels of the Irf5 mRNA were relatively higher in splenic cells from certain autoimmune-prone mice (for example, NZB and NZB/W F(1)) than in non-autoimmune C57BL/6 mice. Additionally, levels of Irf5 mRNA and protein were higher in females than in strain and age-matched males. Accordingly, splenic cells from estrogen receptor-alpha (ERα) knockout, when compared with the wild-type (ERα(+/+)), female mice expressed relatively lower levels of Irf5 mRNA and the treatment of splenic cells with 17β-estradiol increased the levels. Furthermore, splenic B cells from the female mice had relatively more IRF5 protein in the nucleus than the male mice. Collectively, our observations demonstrate a gender bias in the expression and sub-cellular localization of the murine IRF5.

Comparative evaluation of cytokines, T-cell apoptosis, and costimulatory molecule expression in tuberculous and nontuberculous pleurisy

In this study, we compared several immune parameters in tuberculosis (TB) and nontuberculosis (NTB) pleurisy to gain an understanding of the mechanism behind enhanced Th1 apoptosis that occurs at sites of active Myobacterium tuberculosis (M. tuberculosis) infection. An initial evaluation of the accumulated cytokines in pleural fluid (PF) demonstrated that both TB and NTB pleurisy were associated with prointflammatory cytokines, while only TB pleurisy had augmented expression of interferon (IFN)-gamma and soluble Fas ligand (sFASL). Despite enhanced expression of the apoptosis-inducing molecule in TB pleurisy, T cells derived from both types of pleurisy exhibited significant apoptosis. In both groups, T-cell apoptosis correlated with low expression of CD80 on PF-derived macrophages and elevated accumulation of TGF-beta in the PF. A causative correlation between TGF-beta and low CD80 expression in the two groups was established by in vitro studies demonstrating TGF-beta inhibition of CD80 upregulation in a macrophage cell line. Together, the findings allude to the possibility that activation in the absence of appropriate CD80 costimulation is the mechanism that leads to T-cell apoptosis at sites of active M. tuberculosis infection. Furthermore, the findings also indicate that T-cell apoptosis is perhaps a host regulatory mechanism to limit inflammation, rather than a pathogen-induced immune deviation.

Kinetics of chemokine secretion in human macrophages infected with various strains of Mycobacterium tuberculosis

BACKGROUND AND PURPOSE

It has been shown that chemokine secretion upon infection with Mycobacterium tuberculosis is influenced by the virulence of the strain, and it is suggested that virulence-associated differences in chemokine secretion contribute to the failure in containing the infection due to poor granuloma formation.

MATERIALS AND METHODS

In this study, we used prevalent M tuberculosis clinical strains (S7 and S10) to study the chemokine secretion profile in infected THP-1 cells and monocyte-derived macrophages (MDM) and compared this with the chemokine secretion induced by laboratory strains.

RESULTS

This study showed that comparatively lower levels of IP-10 were induced by clinical strains than by laboratory strains in both differentiated THP-1 and MDMs. The secretion of MIP-1alpha was also depressed but only in the THP-1 cells infected with clinical strains. This depressed chemokine secretion may hinder the movement of Th-1 cells from the periphery into the infection foci to control the infection. Correlation between IP-10 and IL-12p40 showed a negative relationship in control MDMs, while there was a positive correlation in all the infected strains, indicating their cooperative role in attracting and activating Th1 cells for a protective immune response at the site. This relationship was strain dependent, with avirulent H37Ra showing higher correlation, followed by the clinical strains and the virulent H37Rv. A positive correlation of IP-10 with IFN-gamma (S7 and H37Ra) and with IL-10 (H37Ra and H37Rv) suggested a definitive interplay of these molecules in infection.

CONCLUSIONS

The chemokines secretion by infected THP-1 cells and MDMs was strain dependant and the lower induction by the clinical strains may indicate that the clinical strains maintain a quiescent nature to mislead the host immune system for their benefit.

Phenotypic modulation in Mycobacterium tuberculosis infected neutrophil during tuberculosis

BACKGROUND & OBJECTIVE

Polymorphonuclear leucocytes (PMN) or neutrophils infiltrate to the inflammatory sites and phagocytose mycobacteria thereby inhibiting the bacillary spread initially until the accumulated macrophages get activated. The present study was carried out to highlight the interaction of neutrophils with the two clinical isolates (S7 and S10) of Mycobacterium tuberculosis and the subsequent morphological changes.

METHODS

Dextran purified neutrophils from normal and TB patients infected with M. tuberculosis isolates were cultured for 3 and 18 h time points. At the end of termination, the cell surface expression of CD16, CD69, CXCR2 and induction of apoptosis were analyzed using flow cytometry. Cytokines and chemokines were estimated in supernatants by ELISA.

RESULTS

All infected PMN showed decrease in CD16 at both time points in normals while at 18 h in TB group. Interestingly, CD69 expression was significantly high at early time point in TB-PMN compared to normals. The high expression of CXCR2 was sustained in infected TB-PMN at both the time points. S7 and S10 infected neutrophils showed high phagocytic indices compared to H37Rv in both the groups. A significant increase in apoptosis was observed at both the time points in infected TB-PMN but only at 18 h in normals. Increased pro-inflammatory cytokine (TNF-alpha) and chemokine (IL-8) response was observed in infected neutrophils at 3 h in both the groups.

INTERPRETATION & CONCLUSION

This study demonstrates the varying degree of modulation of neutrophil functions in both the groups. TB-PMN was more competent in amplifying the innate immune response and conferring protection at the early phase of infection. However, the response was not strain specific in either of these groups.

Expression of co-stimulatory molecules B7.1 & B7.2 on macrophages infected with various strains of Mycobacterium tuberculosis & its influence on T-cell apoptosis

BACKGROUND & OBJECTIVE

Activation of T cells is mediated through two critical signals provided by activated macrophages. The first signal is triggered when T cell receptor (TCR) binds to the major histocompatibility antigen (MHC/Ag) complex. The second signal is the interaction of co-stimulatory molecules with their respective ligands on T cells for their activation and proliferation. We undertook this study to observe the modulation in B7.1 (CD80) and B7.2 (CD86) co-stimulatory molecules on Mycobacterium tuberculosis infected monocyte derived macrophages (MDM) and their role in T helper (Th1) cell apoptosis.

METHODS

M. tuberculosis clinical strains (S7 and S10) and laboratory strains (H37Ra and H37Rv) were used to infect the MDMs. The modulation of apoptosis was assessed by treating T cells with anti-CD3 and anti-CD28 antibodies. The infected MDMs were co-cultured with autologous PPD pulsed T cells to ascertain the role of co-stimulatory molecules during infection.

RESULTS

In infected MDMs, all strains on day 1 but only S7 on day 2 showed significant decrease (P<0.05) in B7.1 expression compared to uninfected. The expression levels of B7.2 were also low on day 1 in S7, S10 and H37Ra infected MDMs. The anit-CD3 induced apoptosis in PPD pulsed Tcells showed further reduction with anti-CD28 antibodies. However, the modulation observed in B7.1 expression in infected MDMs was not reflected in T cell apoptosis in co-culture experiments.

INTERPRETATION & CONCLUSION

Our results confirmed the role of B7.1 in rescuing the activated Tcells from undergoing apoptosis. During infection when the expression of B7.1 is downregulated, other co-stimulatory molecules may take over its crucial role to confer protective immune response against M. tuberculosis.

NK Cells Lyse T Regulatory Cells in Human Infection with An Intracellular Pathogen (B167)

Previously we found that regulatory T cells (CD4+CD25+Foxp3+ cells, Tregs) expand in response to M.tuberculosis (M. TB) through mechanism that depend on prostaglandin E2 production. In the current study, we determined the role of NK cells in regulating Tregs expansion in human M. TB infection. M. TB whole cell lysate (TB lysate) resulted in regulatory T cell expansion (15.33±1.02% vs 1.5±0.22%, P&lt;0.001). Addition of monokine-activated NK cells (IL-12, IL-15 and IL-18) markedly inhibited Treg expansion (6.2±1.2% vs 15±1.5%, P&lt;0.001) but freshly isolated NK cells had no effect. NK cells activated with TB lysate-stimulated monocytes also reduced Tregs expansion (13.2±0.3% to 3.4±1.4%, P&lt;0.001) confirming the physiological relevance of this effect. Reduced Tregs expansion was not due to inhibition of PGE2 production or because of IFN γ. Monokine activated NK cells lysed TB lysate-expanded Tregs, but not freashly isolated Tregs (% specific lysis of 21±3% vs 1±1% P&lt;0.001), nor T regs depleted T cells. Anti-NKG2D and anti-NKp46 reduced the % specific lysis of expanded Tregs from 22±3% to 7±3% and 8±3%, respectively (P&lt;0.001) but abs to CD16, DNAM-1, and 2B4 had no effect. NKG2D ligand, ULBP1 expression was markedly upregulated on expanded T regs, compared to T regs depleted cells ( 31±5% vs 2.1 ±0.4%, P=0.002) and freshly isolated Tregs (4.6±1.1%). Anti -ULBP1 significantly inhibited the NK mediated lysis of expanded Tregs (specific lysis of 27±4% vs 9±2%, P&lt;0.001) but abs to ULBP2, ULBP3 and MICA/B had no effect. These finding suggest that NK cells reduce the frequency of M.TB-expanded T regs by direct lysis.

Th2-type immune response observed in healthy individuals to sonicate antigen prepared from the most prevalentMycobacterium tuberculosisstrain with single copy of IS6110

Different Mycobacterium tuberculosis strains operate different immune evasion strategies for their survival in the host. This mainly depends on the virulence of the strain and the host immune responses. The most virulent strains are actively involved in the transmission, widely spread in the community and induce differential immune responses. We evaluated the immune response of a sonicate antigen prepared from one predominant strain (S7) from M. tuberculosis harbouring a single copy of IS6110. Significant lymphoproliferative response against purified protein derivative from tubercle bacillus (PPD) and H37Rv antigens was observed in PPD positive normal individuals and tuberculosis patients. Interferon-gamma (IFN-gamma) levels against these antigens were significantly increased in normal individuals but not in tuberculosis patients. The antigen S7 showed marginal T-cell proliferation but did not induce IFN-gamma secretion in both groups. Conversely, it induced significantly high levels of cytokine interleukin 4 (IL-4) in normal individuals. The macrophage cytokines, IL-12 and tumour necrosis factor alpha (TNF-alpha), did not show S7 antigen specific stimulation. The intracellular cytokine further confirmed an increase in IL-4(+)/CD4+ T-cells and a decrease in IFN-gamma(+)/CD4+ T-cells upon stimulation. The antibody response showed an increase in IgG and IgA levels against this antigen in normal individuals. These observations suggest that antigen S7 modulates the immune response towards T helper cell type 2 by suppressing T helper cell type 1 protective immune response in PPD positive normal individuals. We speculate that some components of this sonicate antigen are associated with immunosuppressive response.

Cell-mediated immune responses of healthy laboratory volunteers to sonicate antigens prepared from the most prevalent strains of Mycobacterium tuberculosis from South India harboring a single copy of IS6110

Our restriction fragment length polymorphism (RFLP) studies have shown that the most prevalent (40%) strains of Mycobacterium tuberculosis from South India contain a single copy of the IS6110 insertion sequence and are of importance in studying virulence and immunity. Sonicate antigens from seven such strains were used to study in vitro T-cell proliferation and gamma interferon (IFN-gamma) and interleukin-12 (IL-12) secretion as markers of protective immunity in 25 healthy subjects positive for purified protein derivative (PPD). The standard PPD and heat-killed H37Rv antigens induced the maximum levels of T-cell proliferation and IFN-gamma secretion but low levels of IL-12. All sonicate antigens induced T-cell proliferation and IFN-gamma secretion with strong positive correlation. Our results suggest that sonicate antigens from the most prevalent and recent strains of M. tuberculosis from clinical isolates have the potential to induce T-cell activation and may allow newer and specific antigens to be further characterized for diagnosis and vaccine development.