CD4+ T cells mediate mucosal and systemic immune responses to experimental hookworm infection

Hookworm infection is associated with anaemia and malnutrition in many resource‐limited countries. Ancylostoma hookworms have previously been shown to modulate host cellular immune responses through multiple mechanisms, including reduced mitogen‐mediated lymphocyte proliferation, impaired antigen presentation/processing, and relative reductions in CD4⁺ T cells in the spleen and mesenteric lymph nodes. Syrian hamsters were depleted of CD4⁺ for up to 9 days following intraperitoneal injection (200 μg) of a murine anti‐mouse CD4 monoclonal IgG (clone GK1·5). CD4⁺ T‐cell‐depleted hamsters infected with the hookworm Ancylostoma ceylanicum exhibited a threefold higher mean intestinal worm burden and more severe anaemia than animals that received isotype control IgG. In addition, depletion of CD4⁺ T cells was associated with impaired cellular and humoral (serum and mucosal) immune responses to hookworm antigens. These data demonstrate an effector role for CD4⁺ T cells in hookworm immunity and disease pathogenesis. Ultimately, these studies may yield important insights into the relationship between intestinal nematode infections and diseases that are associated with CD4⁺ T‐cell depletion, including HIV.     

Ethanol consumption modifies dendritic cell antigen presentation in mice

Background:  Alcohol consumption impairs type 1 cell‐mediated adaptive immune responses both in vivo and in vitro. The present study investigated the effect of alcohol consumption on antigen‐presenting cell (APC) populations and cytokine production. Methods:  BALB/c were fed ethanol‐containing, pair‐fed isocaloric liquid control, or solid diets for 11 days. Macrophage and dendritic cell (DC) populations were isolated by paramagenetic bead separation and used to present ovalbumin (OVA) to highly purified syngeneic CD4⁺ T cells derived from DO11.10 T cell receptor transgenic mice in coculture. DC isolated from diet‐fed mice were also used to present OVA to highly purified CD4⁺ T cells derived from antigen‐naïve DO11.10Rag2^?/? mice that are devoid of memory T cells. In vitro cytokine responses, interleukin (IL) ‐2, IL‐6, IL‐12, IL‐13, IL‐17A, and interferon‐γ (IFN‐γ) were measured by enzyme‐linked immunosorbent assay. Flow cytometry measured cell surface molecule expression. Results:  Alcohol consumption impairs delayed hypersensitivity responses (type 1) and enhances serum IgE levels (type 2). CD11c⁺ DC, but not F4/80⁺ macrophages, support cytokine responses by purified CD4⁺ T cells. CD11c⁺ DC derived from ethanol consuming BALB/c mice show diminished ability to support IFN‐γ responses by purified CD4⁺ T cells derived from DO11.10 or DO11.10Rag2^?/? mice. Subset analysis indicates that of the 3 “conventional” DC subsets found in mouse spleens, CD11c⁺CD8⁺ DCs are both responsible for OVA presentation and susceptible to the effects of ethanol. Ethanol consumption does not overtly alter the percent of splenic DC, but does increase the surface density of CD11c on these cells. Data show that cocultures containing purified CD4⁺ T DO11.10 cells and APC derived from alcohol‐consuming mice show decreased IL‐6, IL‐12, IL‐17A, and IFN‐γ and increased IL‐13 cytokine production in response to OVA stimulation. Conclusions:  Ethanol alters CD11c⁺CD8⁺ DC function, affecting cytokines responsible for adaptive immune responses. A unifying hypothesis for the underlying mechanism(s) of ethanol’s effect upon adaptive immune function is proposed.     

Heligmosomoides bakeri antigen rescues CD4-positive T cells from glucocorticoid-induced apoptosis by Bcl-2 protein expression

Heligmosomoides bakeri infection in mice is associated with a dominant CD4⁺ T‐cell response and with the activity of natural Treg cells with CD4⁺CD25⁺ phenotype. The polarization of Th2 T‐cell phenotype and the increase in the CD4⁺CD25⁺ T cell population are regulated by glucocorticoids that induce apoptosis in CD4⁺CD25^? T cells and inhibit apoptosis in CD4⁺CD25⁺ T cells. However, exposure of mice to H. bakeri antigen induces a high glucocorticoid concentration in serum and a reduction in the number of CD4‐positive; CD4⁺CD25^? and CD4⁺CD25⁺ apoptotic T cells in mesenteric lymph node cells. In this study to evaluate the in vitro effect of the anti‐apoptotic property of H. bakeri antigen on T cells, apoptosis of these cells was induced by glucocorticoids‐dexamethasone (Dex). Excretory–secretory (ES) antigen of the nematode prevented Dex‐induced apoptosis in CD4‐positive T cells with CD4⁺CD25^? and CD4⁺CD25^High phenotype by Bcl‐2 protein expression. Contrary to the effect on CD4‐positive T cells, survival of CD8⁺ T cells was not connected with expression of Bcl‐2 protein. This suggest that H. bakeri antigen modulates CD4‐positive T cell sensitivity to glucocorticoid‐induced apoptosis by induction of Bcl‐2 protein.     

Distinct DC subsets regulate adaptive Th1 and 2 responses during Trichuris muris infection

Low‐ and high‐dose infections with the murine large intestinal nematode Trichuris muris are associated with induction of adaptive Th1 and Th2 responses, respectively, in mesenteric lymph nodes (MLN). Classical dendritic cells (cDC) accumulate in the large intestinal mucosa and MLN upon T. muris infection, yet their role in driving adaptive responses to infection remains largely unknown. We performed low‐ and high‐dose T. muris infections of mice deficient in defined cDC subsets to investigate their role in induction of adaptive immune responses. Mice lacking IRF4‐dependent cDC failed to clear a high‐dose infection and displayed impaired Th2 responses. Conversely, mice lacking IRF8‐dependent cDC cleared a low‐dose infection and displayed an impaired Th1 response while increased production of Th2 cytokines. Finally, mice lacking both IRF4‐ and IRF8‐dependent cDC were able to generate a Th2 response and clear a low‐dose infection. Collectively, these results suggest that IRF4‐ and IRF8‐dependent cDC act antagonistically during T. muris infection, and demonstrate that intestinal Th2 responses can be generated towards T. muris in the absence of IRF4‐dependent cDC.     

Host Th1/Th2 immune response to Taenia solium cyst antigens in relation to cyst burden of neurocysticercosis

Neurocysticercosis (NCC), Taenia solium larval infection of the brain, is an important cause of acquired seizures in endemic countries, which relate to number, location and degenerating cysts in the brain. Multicyst infections are common in endemic countries although single‐cyst infection prevails in India. Single‐cyst infections in an endemic country suggest a role for host immunity limiting the infection. This study examined ex vivo CD4⁺ T cells and in vitro Th1 and Th2 cytokine responses to T. solium cyst antigens of peripheral blood mononuclear cells of healthy subjects from endemic and nonendemic regions and of single‐ and multicyst‐infected patients for association with cyst burden of NCC. T. solium cyst antigens elicited a Th1 cytokine response in healthy subjects of T. solium‐endemic and T. solium‐non‐endemic regions and those with single‐cyst infections and a Th2 cytokine response from subjects with multicyst neurocysticercosis. Multicyst neurocysticercosis subjects also exhibited low levels of effector memory CD4⁺ T cells. Th1 cytokine response of T. solium exposure and low infectious loads may aid in limiting cyst number. Th2 cytokines and low effector T cells may enable multiple‐cyst infections to establish and persist.     

CD8α− DC is the major DC subset which mediates inhibition of allergic responses by Schistosoma infection

Our and others' previous studies have shown that Schistosoma japonicum (SJ) infection can inhibit allergic reactions. We recently reported that DCs played an important role in SJ infection‐mediated inhibition of allergy, which was associated with enhanced IL‐10 and T regulatory cell responses. Here, we further compared the role of CD8α⁺ DC and CD8α^? DC subsets for the inhibitory effect. We sorted CD8α⁺ DC (SJCD8α⁺ DC) and CD8α^? DC (SJCD8α^? DC) from SJ‐infected mice and tested their ability to modulate allergic responses in vivo. The data showed that the adoptive transfer of SJCD8α^? DC was much more efficient than SJCD8α⁺ DC for the suppression of allergic airway eosinophilia, mucus overproduction, antigen‐specific IgE responses, and Th2 cytokines (IL‐4 and IL‐5). More importantly, we found that the transfer of SJCD8α^? DC, but not SJCD8α⁺ DC, significantly increased IL‐10 and TGF‐β production following OVA exposure. As control, the transfer of DC subsets from naïve mice had no significant effect on allergic inflammation. In addition, SJCD8α‐DC expressed significantly higher IL‐10 but lower IL‐12, CD80 and CD86 than SJCD8α⁺ DC, fitting a tolerogenic phenotype. The results suggest that CD8α^? DC is the predominant DC subset which is involved in the parasitic infection‐mediated inhibition of allergic inflammation and possibly through enhancing immunomodulatory cytokine (IL‐10 and TGF‐β) production.     

Antigenic fractions of Leishmania (Viannia) braziliensis: the immune response characterization of patients at the initial phase of disease

American cutaneous leishmaniasis (ACL) has different clinical manifestations and these manifestations are dependent on the immunological status of the host. As CD4⁺ and CD8⁺ T cells and their mediators play a fundamental role in the host response to Leishmania and there is also a search for antigenic molecules to be used as future vaccines and tools for prognostic tests, this study characterized ACL patients’ immune response after stimulation with soluble and insoluble fractions of L. (V.) braziliensis. We demonstrated a prevailing production of the Th2 cytokines, IL‐4 and IL‐10 and a specific production of IFN‐γ and TNF‐α in patients before treatment. There was also a predominance of CD4⁺ T cells and a small percentage CD8⁺ T cells. The insoluble antigenic fraction primarily stimulated CD4⁺ T cells, while the soluble antigenic fraction showed a mixed profile, with CD4⁺ T cells being the main responsible for Th2 cytokines and CD8⁺ T cells for Th1 cytokines. Therefore, our results showed that a down‐modulation of the Th1 type of response occurs in the initial phase of L. braziliensis disease, being the antigenic fractions capable of stimulating a specific immune response.     

IL‐6 promotes CD4+ T‐cell and B‐cell activation during Plasmodium infection

Humoral immunity develops in the spleen during blood‐stage Plasmodium infection. This elicits parasite‐specific IgM and IgG, which control parasites and protect against malaria. Studies in mice have elucidated cells and molecules driving humoral immunity to Plasmodium, including CD4⁺ T cells, B cells, interleukin (IL)‐21 and ICOS. IL‐6, a cytokine readily detected in Plasmodium‐infected mice and humans, is recognized in other systems as a driver of humoral immunity. Here, we examined the effect of infection‐induced IL‐6 on humoral immunity to Plasmodium. Using P. chabaudi chabaudi AS (PcAS) infection of wild‐type and IL‐6^?/? mice, we found that IL‐6 helped to control parasites during primary infection. IL‐6 promoted early production of parasite‐specific IgM but not IgG. Notably, splenic CD138⁺ plasmablast development was more dependent on IL‐6 than germinal centre (GC) B‐cell differentiation. IL‐6 also promoted ICOS expression by CD4⁺ T cells, as well as their localization close to splenic B cells, but was not required for early Tfh‐cell development. Finally, IL‐6 promoted parasite control, IgM and IgG production, GC B‐cell development and ICOS expression by Tfh cells in a second model, Py17XNL infection. IL‐6 promotes CD4⁺ T‐cell activation and B‐cell responses during blood‐stage Plasmodium infection, which encourages parasite‐specific antibody production.     

Ascaris suum infection modulates inflammation: Implication of CD4+ CD25high Foxp3+ T cells and IL‐10

Helminth infections have the ability to modulate host's immune response through mechanisms that allow the chronic persistence of the worms in the host. Here, we investigated the mechanisms involved on the suppressive effect of Ascaris suum infection using a murine experimental model of LPS‐induced inflammation. We found that infection with A. suum markedly inhibited leucocyte influx induced by LPS into air pouches, suppressed secretion of pro‐inflammatory cytokines (IL‐1β, TNF‐α and IL‐6) and induced high levels of IL‐10 and TGF‐β. Augmented frequency of CD4⁺ CD25^high Foxp3⁺ T cells was observed in the mesenteric lymph nodes of infected mice. Adoptive transfer of purified CD4⁺ CD25⁺ T cells to recipient uninfected mice demonstrated that these cells were able to induce a suppressive effect in the LPS‐induced inflammation in air pouch model. In addition, adoptive transfer of CD4⁺ CD25⁺ T cells derived from IL‐10 knockout mice suggests that this suppressive effect of A. suum infection involves IL‐10 cytokine. In conclusion, our results demonstrated that A. suum experimental infection was capable of suppressing LPS‐induced inflammation by mechanisms, which seem to be dependent on responses of CD4⁺ CD25⁺ T cells and secretion of IL‐10 cytokine.     

Type I IFNs promote the early IFN‐γ response and the IL‐10 response in Leishmania mexicana infection

The protozoan parasite Leishmania mexicana causes chronic cutaneous disease in humans and most mouse strains. We previously showed that STAT4‐deficient mice, but not IL‐12p40‐deficient mice, have more parasites and progressively growing lesions unlike those of wild‐type mice, the lesions and parasite burdens of which plateau by 10–12 weeks post‐infection. This demonstrates a STAT4‐dependent, IL‐12/IL‐23‐independent pathway of parasite control. Type I IFNs are important in viral and other infections and can activate STAT4. We found that IFN‐α/βR‐deficient mice have a nonpersistent, early IFN‐γ defect, and a persistent, early IL‐10 defect, without changes in serum IL‐12 or LN‐derived nitric oxide. We found less IL‐10 per cell in CD25⁺CD4⁺ T cells and possibly fewer IL‐10‐producing cells in the draining LN of IFN‐α/βR‐deficient vs. wild‐type mice. IFN‐α/βR‐deficient mice have chronic, nonprogressive disease, like wild‐type mice, suggesting that IL‐10 and IFN‐γ defects may balance each other. Our data indicate that although type I IFNs help promote early Th1 responses, they are not the missing activators of STAT4 responsible for partial control of L. mexicana. Also, the lack of lesion resolution in IFN‐α/βR‐deficient mice despite lower IL‐10 levels indicates that other pathways independent of T cell IL‐10 help prevent an IL‐12‐driven clearance of parasites.     

Increased susceptibility to oral Trichuris muris infection in the specific absence of CXCR5+ CD11c+ cells

Trichuris muris is a natural mouse helminth pathogen which establishes infection specifically in the caecum and proximal colon. The rapid expulsion of T. muris in resistant mouse strains is associated with the induction of a protective T helper cell type 2 (Th2)‐polarized immune response. Susceptible mouse strains, in contrast, mount an inappropriate Th1 response to T. muris infection. Expression of the chemokine CXCL13 by stromal follicular dendritic cells attracts CXCR5‐expressing cells towards the B‐cell follicles. Previous studies using a complex in vivo depletion model have suggested that CXCR5‐expressing conventional dendritic cells (cDC) help regulate the induction of Th2‐polarized responses. Here, transgenic mice with CXCR5 deficiency specifically restricted to CD11c⁺ cells were used to determine whether the specific absence CXCR5 on CD11c⁺ cells such as cDC would influence susceptibility to oral T. muris infection by affecting the Th1/Th2 balance. We show that in contrast to control mice, those which lacked CXCR5 expression on CD11c⁺ cells failed to clear T. muris infection and developed cytokine and antibody responses that suggested a disturbed Th1/Th2 balance with enhanced IFN‐γ expression. These data suggest an important role of CXCR5‐expressing CD11c⁺ cells such as cDC in immunity to oral T. muris infection.     

The mucosal and systemic immune responses elicited by a chitosan-adjuvanted intranasal influenza H5N1 vaccine

Please cite this paper as: Svindland et al. The mucosal and systemic immune responses elicited by a chitosan‐adjuvanted intranasal influenza H5N1 vaccine. Influenza and Other Respiratory Viruses DOI:10.1111/j.1750‐2659.2011.00271.x. Background Development of influenza vaccines that induce mucosal immunity has been highlighted by the World Health Organisation as a priority (Vaccine 2005;23:1529). Dose‐sparing strategies and an efficient mass‐vaccination regime will be paramount to reduce the morbidity and mortality of a future H5N1 pandemic. Objectives This study has investigated the immune response and the dose‐sparing potential of a chitosan‐adjuvanted intranasal H5N1 (RG‐14) subunit (SU) vaccine in a mouse model. Methods Groups of mice were intranasally immunised once or twice with a chitosan (5 mg/ml)‐adjuvanted SU vaccine [7·5, 15 or 30 μg haemagglutinin (HA)] or with a non‐adjuvanted SU vaccine (30 μg HA). For comparison, another group of mice were intranasally immunised with a whole H5N1 (RG‐14) virus (WV) vaccine (15 μg HA), and the control group consisted of unimmunised mice. Results The chitosan‐adjuvanted SU vaccine induced an immune response superior to that of the non‐adjuvanted SU vaccine. Compared with the non‐adjuvanted SU group, the chitosan‐adjuvanted SU vaccine elicited higher numbers of influenza‐specific antibody‐secreting cells (ASCs), higher concentrations of local and systemic antibodies and correspondingly an improved haemagglutination inhibition (HI) and single radial haemolysis (SRH) response against both the homologous vaccine strain and drifted H5 strains. We measured a mixed T‐helper 1/T‐helper 2 cytokine response in the chitosan‐adjuvanted SU groups, and these groups had an increased percentage of virus‐specific CD4⁺ T cells producing two Thelper 1 (Th1) cytokines simultaneously compared with the non‐adjuvanted SU group. Overall, the WV vaccine induced higher antibody concentrations in sera and an HI and SRH response similar to that of the chitosan‐adjuvanted SU vaccine. Furthermore, the WV vaccine formulation showed a stronger bias towards a T‐helper 1 profile than the SU vaccine and elicited the highest frequencies of CD4⁺ Th1 cells simultaneously secreting three different cytokines (INFγ⁺, IL2⁺ and INFα⁺). As expected, two immunisations gave a better immune response than one in all groups. The control group had very low or not detectable results in the performed immunoassays. Conclusion The cross‐clade serum reactivity, improved B‐ and T‐cell responses and dose‐sparing potential of chitosan show that a chitosan‐adjuvanted intranasal influenza vaccine is a promising candidate vaccine for further preclinical development.     

Ribavirin downmodulates inducible costimulator on CD4+ T cells and their interleukin-10 secretion to assist in hepatitis C virus clearance

Background and Aim: The immunological mechanism by which ribavirin (RBV) polarizes the T‐helper (Th) 1/2 balance toward Th1 predominancy is not fully understood. We therefore examined whether RBV affects costimulatory signaling, which is known to be essential for regulating the Th1/2 balance. Methods: The expression of costimulatory molecules and their ligands, and levels of various cytokines, released from CD4⁺ T cells obtained from healthy individuals or patients with chronic hepatitis C virus (HCV) infection were analyzed. Results: In CD4⁺ T cells, RBV selectively downmodulates the expression of inducible costimulator (ICOS), a ligand for B7–H2 on dendritic cells, which mainly differentiates Th0 into Th2 cells. Moreover, the levels of interleukin‐10 (IL‐10) released from RBV‐stimulated CD4⁺ T cells also decreased, indicating that the downmodulation of ICOS induced by RBV might be correlated with the decrease in IL‐10 released from Th cells, leading to the inhibition of Th2 activity. An analysis of the association between ICOS kinetics and hepatitis C virus (HCV) elimination in hepatitis C patients receiving combined pegylated interferon and RBV indicated that HCV elimination tended to occur more frequently in patients showing ICOS downmodulation with RBV treatment. A decrease in IL‐10 production by CD4⁺ T cells was also observed in association with ICOS downregulation in patients who succeeded in HCV elimination. Conclusions: The downmodulation of ICOS in correlation with a reduction in IL‐10 produced by CD4⁺ T cells is possibly the immunological mechanism of action of RBV, which polarizes the Th1/2 balance toward a Th1 cytokine profile, thus contributing to the elimination of cells chronically infected with HCV.     

Accumulation of eosinophils in intestine-draining mesenteric lymph nodes occurs after Trichuris muris infection

Eosinophils have recently been demonstrated capable of localizing to lymph nodes that drain mucosal surfaces, in particular during T helper 2 (Th2) responses. Resistance of mice to infection with the gastrointestinal nematode Trichuris muris depends critically on mounting of a Th2 response and represents a useful model system to investigate Th2 responses. Following infection of resistant BALB/c mice with T. muris, we observed accumulation of eosinophils in intestine-draining mesenteric lymph nodes (MLNs). The accumulation of MLN eosinophils was initiated during the second week of infection and peaked during worm expulsion. In contrast, we detected a comparably late and modest increase in eosinophil numbers in the MLNs of infected susceptible AKR mice. MLN eosinophils localized preferentially to the medullary region of the lymph node, displayed an activated phenotype and contributed to the interleukin-4 (IL-4) response in the MLN. Despite this, mice genetically deficient in eosinophils efficiently generated IL-4-expressing CD4(+) T cells, produced Th2 cytokines and mediated worm expulsion during primary T. muris infection. Thus, IL-4-expressing eosinophils accumulate in MLNs of T. muris-infected BALB/c mice but are dispensable for worm expulsion and generation of Th2 responses, suggesting a distinct or subtle role of MLN eosinophils in the immune response to T. muris infection.     

Allergic bronchopulmonary aspergillosis in a 2‐year‐old asthmatic boy with immune dysregulation,polyendocrinopathy, enteropathy,X‐linked

Immune dysregulation, polyendocrinopathy, enteropathy, X‐linked (IPEX) is caused by impaired function of CD4⁺CD25⁺ regulatory T cells that play an important role in controlling exaggerated Th2 responses. The pathogenesis of allergic bronchopulmonary aspergillosis (ABPA) appears to be closely associated with the Th2 response. We report the first case of ABPA in a 2‐year‐old asthmatic boy with IPEX, this being an unusually young age for the development of ABPA. Pediatr Pulmonol. 2009; 44:297–299. © 2009 Wiley‐Liss, Inc.