Combined analysis of host IFN-γ, IL-2 and IP-10 as potential LTBI biomarkers in ESAT-6/CFP-10 stimulated blood.

Background: Accurate diagnosis of latent tuberculosis infected (LTBI) individuals is important in identifying individuals at risk of developing active tuberculosis. Current diagnosis of LTBI routinely relies on the detection and measurement of immune responses using the Tuberculin Skin Test (TST) and interferon gamma release assays (IGRAs). However, IGRA, which detects Mycobacterium tuberculosis specific IFN-γ, is associated with frequent indeterminate results, particularly in immunosuppressed patients. There is a need to identify more sensitive LTBI point of care diagnostic biomarkers. The aim of this study was to assess the validity of early secreted antigen target 6 kDa (ESAT-6) and culture filtrate protein 10 (CFP-10) stimulated plasma to identify additional cytokines and chemokines as potential biomarkers of LTBI. Method: The levels of 27 cytokines and chemokines were measured by Bio-Plex Pro cytokine, chemokine and growth factor assay in ESAT-6 and CFP-10 co-stimulated plasma from 20 LTBI participants with positive IGRA (Quantiferon TB Gold plus) and 20 healthy controls with negative IGRA. Traditional ELISA was used to validate the abundance of the best performing markers in 70 LTBI and 72 healthy participants. All participants were HIV negative. Results: We found that Interleukin 1 receptor antagonist (IL1ra) (p = 0.0056), Interleukin 2 (IL-2) (p < 0.0001), Interleukin 13 (IL-13) (p < 0.0001), Interferon gamma-induced protein 10 (IP-10) (p < 0.0001), and Macrophage inflammatory protein-1 beta (MIP1b) (p = 0.0010) were significantly higher in stimulated plasma of LTBI compared to healthy individuals. Stimulated plasma IL-2 (cutoff 100 pg/mL), IP-10 (cutoff 300 pg/mL) and IL-13 (5 pg/mL) showed potential in diagnosing LTBI with PPV = 100%, 0.89.4%, and 80.9% and NPV = 86.9%, 0.85.7%, and 84.2%, respectively. Conclusion: Our data shows that co-stimulating whole blood with ESAT-6 and CFP-10 may help distinguish LTBI from healthy individuals. We also identified IL-2 and IP-10 as potential biomarkers that could be added to the currently used IFN-γ release assays in detection of LTBI.

Generation of Multicellular 3D Liver Organoids From Induced Pluripotent Stem Cells as a Tool for Modelling Liver Diseases.

The liver is an essential organ that is involved in the metabolism, synthesis, and secretion of serum proteins and detoxification of xenobiotic compounds and alcohol. Studies on liver diseases have largely relied on cancer-derived cell lines that have proven to be inferior due to the lack of drug-metabolising enzymes. Primary human hepatocytes are considered the gold-standard for evaluating drug metabolism. However, several factors such as lack of donors, high cost of cells, and loss of polarity of the cells have limited their widescale adoption and utility. Stem cells have emerged as an alternative source for liver cells that could be utilised for studying liver diseases, developmental biology, toxicology testing, and regenerative medicine. In this article, we describe in detail an optimised protocol for the generation of multicellular 3D liver organoids composed of hepatocytes, stellate cells, and Kupffer cells as a tractable robust model of the liver. Key features • Optimising a protocol for generating multicellular 3D liver organoids from induced pluripotent stem cells. Graphical overview.

Cysteinyl leukotriene receptor-1 as a potential target for host-directed therapy during chronic schistosomiasis in murine model.

Schistosomiasis remains the most devastating neglected tropical disease, affecting over 240 million people world-wide. The disease is caused by the eggs laid by mature female worms that are trapped in host's tissues, resulting in chronic Th2 driven fibrogranulmatous pathology. Although the disease can be treated with a relatively inexpensive drug, praziquantel (PZQ), re-infections remain a major problem in endemic areas. There is a need for new therapeutic drugs and alternative drug treatments for schistosomiasis. The current study hypothesized that cysteinyl leukotrienes (cysLTs) could mediate fibroproliferative pathology during schistosomiasis. Cysteinyl leukotrienes (cysLTs) are potent lipid mediators that are known to be key players in inflammatory diseases, such as asthma and allergic rhinitis. The present study aimed to investigate the role of cysLTR1 during experimental acute and chronic schistosomiasis using cysLTR1-/- mice, as well as the use of cysLTR1 inhibitor (Montelukast) to assess immune responses during chronic Schistosoma mansoni infection. Mice deficient of cysLTR1 and littermate control mice were infected with either high or low dose of Schistosoma mansoni to achieve chronic or acute schistosomiasis, respectively. Hepatic granulomatous inflammation, hepatic fibrosis and IL-4 production in the liver was significantly reduced in mice lacking cysLTR1 during chronic schistosomiasis, while reduced liver pathology was observed during acute schistosomiasis. Pharmacological blockade of cysLTR1 using montelukast in combination with PZQ reduced hepatic inflammation and parasite egg burden in chronically infected mice. Combination therapy led to the expansion of Tregs in chronically infected mice. We show that the disruption of cysLTR1 is dispensable for host survival during schistosomiasis, suggesting an important role cysLTR1 may play during early immunity against schistosomiasis. Our findings revealed that the combination of montelukast and PZQ could be a potential prophylactic treatment for chronic schistosomiasis by reducing fibrogranulomatous pathology in mice. In conclusion, the present study demonstrated that cysLTR1 is a potential target for host-directed therapy to ameliorate fibrogranulomatous pathology in the liver during chronic and acute schistosomiasis in mice.

Mycobacterial FtsEX-RipC interaction is required for normal growth and cell morphology in rifampicin and low ionic strength conditions.

Tuberculosis, a lung disease caused by Mycobacterium tuberculosis (Mtb), remains a major global health problem ranking as the second leading cause of death from a single infectious agent. One of the major factors contributing toward Mtb's success as a pathogen is its unique cell wall and its ability to counteract various arms of the host's immune response. A recent genome-scale study profiled a list of candidate genes that are predicted to be essential for Mtb survival of host-mediated responses. One candidate was FtsEX, a protein complex composed of an ATP-binding domain, FtsE, and a transmembrane domain, FtsX. FtsEX functions through interaction with a periplasmic hydrolase, RipC. Homologs of FtsEX exist in other bacteria and have been linked with playing a key role in regulating peptidoglycan hydrolysis during cell elongation and division. Here, we report on Mycobacterium smegmatis, FtsE, FtsX, and RipC and their protective roles in stressful conditions. We demonstrate that the individual genes of FtsEX complex and RipC are not essential for survival in normal growth conditions but conditionally essential in low-salt media and antibiotic-treated media. Growth defects in these conditions were characterized by short and bulgy cells as well as elongated filamentous cells. Our results suggest that FtsE, FtsX, and RipC are required for both normal cell elongation and division and ultimately for survival in stressful conditions. IMPORTANCE: Mycobacterial cell growth and division are coordinated with regulated peptidoglycan hydrolysis. Understanding cell wall gene complexes that govern normal cell division and elongation will aid in the development of tools to disarm the ability of mycobacteria to survive immune-like and antibiotic stresses. We combined genetic analyses and scanning electron microscopy to analyze morphological changes of mycobacterial FtsEX and RipC mutants in stressful conditions. We demonstrate that FtsE, FtsX, FtsEX, and RipC are conditionally required for the survival of Mycobacterium smegmatis during rifampicin treatment and in low-salt conditions. Growth defects in these conditions were characterized by short and bulgy cells as well as elongated filamentous cells. We also show that the FtsEX-RipC interaction is essential for the survival of M. smegmatis in rifampicin. Our results suggest that FtsE, FtsX, and RipC are required for normal cell wall regulation and ultimately for survival in stressful conditions.

Immune cells and associated molecular markers in dermal fibrosis with focus on raised cutaneous scars.

Raised dermal scars including hypertrophic, and keloid scars as well as scalp-associated fibrosing Folliculitis Keloidalis Nuchae (FKN) are a group of fibrotic raised dermal lesions that mostly occur following cutaneous injury. They are characterized by increased extracellular matrix (ECM) deposition, primarily excessive collagen type 1 production by hyperproliferative fibroblasts. The extent of ECM deposition is thought to be proportional to the severity of local skin inflammation leading to excessive fibrosis of the dermis. Due to a lack of suitable study models, therapy for raised dermal scars remains ill-defined. Immune cells and their associated markers have been strongly associated with dermal fibrosis. Therefore, modulation of the immune system and use of anti-inflammatory cytokines are of potential interest in the management of dermal fibrosis. In this review, we will discuss the importance of immune factors in the pathogenesis of raised dermal scarring. The aim here is to provide an up-to-date comprehensive review of the literature, from PubMed, Scopus, and other relevant search engines in order to describe the known immunological factors associated with raised dermal scarring. The importance of immune cells including mast cells, macrophages, lymphocytes, and relevant molecules such as cytokines, chemokines, and growth factors, antibodies, transcription factors, and other immune-associated molecules as well as tissue lymphoid aggregates identified within raised dermal scars will be presented. A growing body of evidence points to a shift from proinflammatory Th1 response to regulatory/anti-inflammatory Th2 response being associated with the development of fibrogenesis in raised dermal scarring. In summary, a better understanding of immune cells and associated molecular markers in dermal fibrosis will likely enable future development of potential immune-modulated therapeutic, diagnostic, and theranostic targets in raised dermal scarring.

Elevated IP-10 at the Protein and Gene Level Associates With Pulmonary TB.

There is an urgent need for accurate and sensitive diagnostic tools that can overcome the current challenge to distinguish individuals with latent tuberculosis infection (LTBI) from individuals with active tuberculosis (TB). Recent literature has suggested that a group of cytokines may serve as biomarkers of TB disease progression. Using a multiplex ELISA, we quantified 27 circulatory markers present within the unstimulated plasma of individuals in Durban, South Africa who were healthy (n=20), LTBI (n=13), or had active TB (n=30). RT-qPCR was performed to measure gene expression of the cytokines of interest, using RNA isolated from healthy (n=20), LTBI (n=20), or active TB (n=30). We found that at the protein level, IL-1RA, IL-6, and IP-10 were significantly more abundant in participants with active TB (p< 0.05) compared to those with LTBI individuals. IP-10 also showed the strongest association with active TB compared to healthy and LTBI at mRNA level. Our data shows that these proteins may serve as biomarkers of TB at both the protein and gene level.

Deletion of IL-4Rα signaling on B cells limits hyperresponsiveness depending on antigen load.

BACKGROUND: B cells play an important role in allergies through secretion of IgE. IL-4 receptor α (IL-4Rα) is key in allergic asthma and regulates type 2 cytokine production, IgE secretion, and airway hyperresponsiveness. IL-4 activation of B cells is essential for class switching and contributes to the induction of B effector 2 (Be2) cells. The role of Be2 cells and signaling via IL-4Rα in B cells is not clearly defined. OBJECTIVE: We sought to find out whether IL-4Rα-responsive B cells or Be2 function was essential in experimental allergic asthma. METHODS: Mice lacking IL-4Rα on B cells (mb1creIL-4Rα-/lox) or littermate controls (IL-4Rα-/lox) and mice lacking IL-4 or IL-4/IL-13 on B cells were sensitized and challenged with high-dose house dust mite (>10 µg) or with low-dose house dust mite (<3 µg). We also adoptively transferred naive IL-4Rα-/lox or IL-4Rα-/- B cells into µMT-/- mice a day before sensitization or a day before challenge. We analyzed lung inflammation, cellular infiltrate, and airway hyperresponsiveness. RESULTS: We found that IL-4Rα signaling on B cells was important for optimal TH2 allergic immune responses mainly when the load of antigen is limited. IL-4Rα signaling on B cells was essential for germinal centers and in the effector phase of allergic responses. Be2 cells were essential in airway hyperresponsiveness, but not in other parameters. CONCLUSIONS: IL-4Rα signaling on B cells is deleterious in allergic asthma because it is required for optimal TH2 responses, Be2 function, germinal center formation, and T follicular helper cells, especially when the load of the antigen is limiting.

Mechanistic insights into antiretroviral drug-induced liver injury.

All classes of antiretroviral therapy (ART) have been implicated to induce adverse drug reactions such drug-induced liver injury (DILI) and immune-mediated adverse reactions in Human Immunodeficiency Virus (HIV) infected individuals. Patients that develop adverse drug reactions tend to have prolonged stays in hospital and may require to change to alternative regimens if reactions persist upon rechallenge or if rechallenge is contraindicated due to severity of the adverse reaction. Diagnosis of DILI remains a huge obstacle that delays timely interventions, since it is still based largely on exclusion of other causes. There is an urgent need to develop robust diagnostic and predictive biomarkers that could be used alongside the available tools (biopsy, imaging, and serological tests for liver enzymes) to give a specific diagnosis of DILI. Crucial to this is also achieving consensus in the definition of DILI so that robust studies can be undertaken. Importantly, it is crucial that we gain deeper insights into the mechanism of DILI so that patients can receive appropriate management. In general, it has been demonstrated that the mechanism of ART-induced liver injury is driven by four main mechanisms: mitochondrial toxicity, metabolic host-mediated injury, immune reconstitution, and hypersensitivity reactions. The focus of this review is to discuss the type and phenotypes of DILI that are caused by the first line ART regimens. Furthermore, we will summarize recent studies that have elucidated the cellular and molecular mechanisms of DILI both in vivo and in vitro.

Advances in generating liver cells from pluripotent stem cells as a tool for modeling liver diseases.

Developing robust in vitro models of the liver is essential for studying the pathogenesis of liver diseases, hepatotoxicity testing, and regenerative medicine. Earlier studies were conducted using cell lines derived from hepatomas. Due to the inherent limitations of cell lines, researchers used primary human hepatocytes (PHHs), which are considered a gold standard for in vitro modeling of the liver. However, due to the high cost of PHHs and lack of donors, researchers have sought an alternative source for functional liver cells. Pluripotent stem cells (PSCs) emerged as a viable alternative due to their plasticity and high proliferative capacity. This review gives an overview of the major advances that have been achieved to develop protocols to generate liver cells such as hepatocytes, cholangiocytes, and Küpffer cells from PSCs. We also discuss their application in modeling the pathogenesis of liver diseases such as drug-induced liver injury, acute liver failure, and hepatic steatosis.

IL-4Rα-expressing CD11c+ cells contribute to driving optimal cellular responses during Schistosoma mansoni infection in mice.

Development of IL-4 receptor alpha (IL-4Rα)-dependent cellular immunity regulates host protection against acute schistosomiasis. In this study, we investigated the importance of IL-4Rα-expressing CD11c+ cells in driving the development of optimal cellular responses to Schistosoma mansoni infection by using CD11ccre IL-4Rα-/lox BALB/c mice, which lacked IL-4Rα expression on dendritic cells and alveolar macrophages. Abrogation of IL-4Rα expression on CD11c+ cells affected activation of CD4+ T cells, resulting in reduced numbers of effector CD4+ T cells and impaired production of Th1 and Th2 cytokines by CD4+ T cells ex vivo. However, secretion of both type 1 and type 2 Ab isotypes was unchanged in infected CD11c-specific IL-4Rα-deficient mice compared to littermate controls. Together, these data demonstrate that IL-4Rα-expressing CD11c+ cells play an important role in maintaining cellular immunity during schistosomiasis in mice.

Intervening along the spectrum of tuberculosis: meeting report from the World TB Day nanosymposium in the Institute of Infectious Disease and Molecular Medicine at the University of Cape Town.

Tuberculosis (TB), caused by the highly infectious  Mycobacterium tuberculosis, remains a leading cause of death worldwide, with an estimated 1.6 million associated deaths reported in 2017. In South Africa, an estimated 322,000 (range 230,000-428,000) people were infected with TB in 2017, and a quarter of them lost their lives due to the disease. Bacille Calmette-Guérin (BCG) remains the only effective vaccine against disseminated TB, but its inability to confer complete protection against pulmonary TB in adolescents and adults calls for an urgent need to develop new and better vaccines. There is also a need to identify markers of disease protection and develop novel drugs. It is within this backdrop that we convened a nanosymposium at the Institute of Infectious Disease and Molecular Medicine at the University of Cape Town to commemorate World TB Day and showcase recent findings generated by early career scientists in the institute. The speakers spoke on four broad topics: identification of novel drug targets, development of host-directed drug therapies, transmission of TB and immunology of TB/HIV co-infections.

Chronic schistosomiasis suppresses HIV-specific responses to DNA-MVA and MVA-gp140 Env vaccine regimens despite antihelminthic treatment and increases helminth-associated pathology in a mouse model.

Future HIV vaccines are expected to induce effective Th1 cell-mediated and Env-specific antibody responses that are necessary to offer protective immunity to HIV infection. However, HIV infections are highly prevalent in helminth endemic areas. Helminth infections induce polarised Th2 responses that may impair HIV vaccine-generated Th1 responses. In this study, we tested if Schistosoma mansoni (Sm) infection altered immune responses to SAAVI candidate HIV vaccines (DNA and MVA) and an HIV-1 gp140 Env protein vaccine (gp140) and whether parasite elimination by chemotherapy or the presence of Sm eggs (SmE) in the absence of active infection influenced the immunogenicity of these vaccines. In addition, we evaluated helminth-associated pathology in DNA and MVA vaccination groups. Mice were chronically infected with Sm and vaccinated with DNA+MVA in a prime+boost combination or MVA+gp140 in concurrent combination regimens. Some Sm-infected mice were treated with praziquantel (PZQ) prior to vaccinations. Other mice were inoculated with SmE before receiving vaccinations. Unvaccinated mice without Sm infection or SmE inoculation served as controls. HIV responses were evaluated in the blood and spleen while Sm-associated pathology was evaluated in the livers. Sm-infected mice had significantly lower magnitudes of HIV-specific cellular responses after vaccination with DNA+MVA or MVA+gp140 compared to uninfected control mice. Similarly, gp140 Env-specific antibody responses were significantly lower in vaccinated Sm-infected mice compared to controls. Treatment with PZQ partially restored cellular but not humoral immune responses in vaccinated Sm-infected mice. Gp140 Env-specific antibody responses were attenuated in mice that were inoculated with SmE compared to controls. Lastly, Sm-infected mice that were vaccinated with DNA+MVA displayed exacerbated liver pathology as indicated by larger granulomas and increased hepatosplenomegaly when compared with unvaccinated Sm-infected mice. This study shows that chronic schistosomiasis attenuates both HIV-specific T-cell and antibody responses and parasite elimination by chemotherapy may partially restore cellular but not antibody immunity, with additional data suggesting that the presence of SmE retained in the tissues after antihelminthic therapy contributes to lack of full immune restoration. Our data further suggest that helminthiasis may compromise HIV vaccine safety. Overall, these findings suggested a potential negative impact on future HIV vaccinations by helminthiasis in endemic areas.

Dectin-1-Syk-CARD9 Signaling Pathway in TB Immunity.

One of the first steps toward mounting an effective immune response to Mycobacterium tuberculosis (Mtb) is recognition of the pathogen through pattern-recognition receptors (PRRs) expressed by innate immune cells. Activation of the PRR Dectin-1 by an unknown mycobacterial ligand triggers an intracellular signaling cascade involving numerous proteins, including spleen tyrosine kinase, protein kinase C-delta, and caspase recruitment domain family member 9, some of which have been shown to influence host immune response to TB infection. Here, we review the role of Dectin-1 signaling pathway in anti-mycobacterial immunity and discuss its contribution in the control of Mtb infection, and potential applications in TB vaccine adjuvanticity.

Interleukin-4 Receptor Alpha Expressing B Cells Are Essential to Down-Modulate Host Granulomatous Inflammation During Schistosomasis.

Schistosomiasis (bilharzia) is a parasitic helminth disease that can cause severe inflammatory pathology leading to organ damage in humans. Failure of the host to regulate egg-driven granulomatous inflammation causes host morbidity during chronic infection with Schistosoma mansoni. Although the importance of B cells in regulating pathology during chronic infection has been well defined, the specific contribution of IL-4Rα-expressing B cells is still unknown. To address this, we examined B cell-specific IL-4Rα-deficient (mb1creIL-4Rα-/lox) mice in three experimental models of schistosomiasis: high-dose (100 cercariae), low dose (30 cercariae), and a synchronous egg challenge. In the high dose model, we found that mice deficient in IL-4Rα-expressing B cells were more susceptible to acute schistosomiasis than B cell-deficient (µMT) mice, succumbing to infection at the acute stage whereas µMT mice survived until the chronic stage. An S. mansoni egg challenge model demonstrated that deleting IL-4Rα expression specifically on B cells resulted in increased lung granulomatous pathology, suggesting a role for this B cell subset in controlling granulomatous pathology. In agreement with this, a low dose model of schistosomiasis-which mimics the course of clinical chronic disease-demonstrated that depleting IL-4Rα-expressing B cells in mb1creIL-4Rα-/lox mice considerably impaired the host ability to down-modulate granulomatous inflammation in the liver and gut during chronic schistosomiasis. Taken together, our findings indicate that within the B cell compartment, IL-4Rα-expressing B cells in particular down-modulate the deleterious egg-driven tissue granulomatous inflammation to enable host survival during schistosomiasis in mice.

IL-4-producing B cells regulate T helper cell dichotomy in type 1- and type 2-controlled diseases.

Interleukin-4 (IL-4)-induced T helper (Th) 2 cells promote susceptibility to the protozoan parasite Leishmania major, while conferring immunity to the intestinal trematode Schistosoma mansoni Here, we report that abrogation of IL-4 receptor alpha (IL-4Rα) signaling on B cells in BALB/c mice (mb1creIL-4Rα-/lox) transformed nonhealer BALB/c to a healer phenotype with an early type 1 and dramatically reduced type 2 immune response and an absence of ulceration and necrosis during cutaneous leishmaniasis. From adoptive reconstitution and mixed bone-marrow chimera studies in B cell-deficient (µMT) mice, we reveal a central role for B cell-derived IL-4 and IL-4Rα in the optimal induction of the susceptible type 2 phenotype to L. major infection. We further demonstrate that the absence of IL-4Rα signaling on B cells exacerbated S. mansoni-induced mortality and pathology in BALB/c mice, due to a diminished type 2 immune response. In both disease models, IL-4Rα-responsive B cells displayed increased IL-4 production as early as day 1 after infection. Together, these results demonstrate that IL-4-producing and IL-4Rα-responsive B cells are critical in regulating and assisting early T helper dichotomy toward Th2 responses, which are detrimental in cutaneous leishmaniasis but beneficial in acute schistosomiasis.

Host regulation of liver fibroproliferative pathology during experimental schistosomiasis via interleukin-4 receptor alpha.

Interleukin-4 receptor (IL-4Rα) is critical for the initiation of type-2 immune responses and implicated in the pathogenesis of experimental schistosomiasis. IL-4Rα mediated type-2 responses are critical for the control of pathology during acute schistosomiasis. However, type-2 responses tightly associate with fibrogranulomatous inflammation that drives host pathology during chronic schistosomiasis. To address such controversy on the role of IL-4Rα, we generated a novel inducible IL-4Rα-deficient mouse model that allows for temporal knockdown of il-4rα gene after oral administration of Tamoxifen. Interrupting IL-4Rα mediated signaling during the acute phase impaired the development of protective type-2 immune responses, leading to rapid weight loss and premature death, confirming a protective role of IL-4Rα during acute schistosomiasis. Conversely, IL-4Rα removal at the chronic phase of schistosomiasis ameliorated the pathological fibro-granulomatous pathology and reversed liver scarification without affecting the host fitness. This amelioration of the morbidity was accompanied by a reduced Th2 response and increased frequencies of FoxP3+ Tregs and CD1dhiCD5+ Bregs. Collectively, these data demonstrate that IL-4Rα mediated signaling has two opposing functions during experimental schistosomiasis depending on the stage of advancement of the disease and indicate that interrupting IL-4Rα mediated signaling is a viable therapeutic strategy to ameliorate liver fibroproliferative pathology in diseases like chronic schistosomiasis.

Interleukin-4 receptor alpha is still required after Th2 polarization for the maintenance and the recall of protective immunity to Nematode infection.

There is currently no vaccine against parasitic nematodes and the knowledge on the mechanisms by which protective immunity against this class of parasites is achieved is continuously expanding. Nematode parasites trigger a host protective type 2 immune response via interleukin-4 receptor alpha (IL-4Rα). Despite this central role, it is not known whether IL-4Rα has a role in maintaining host type 2 immune responses following polarization. To determine the role of IL-4Rα after polarization, we used a recently established strain of rosaCreERT2-/+IL-4Rα-/Lox mice where il4rα gene deletion can be temporally controlled. We show that sustained expression of IL-4Rα is required for the maintenance of type 2 immune responses and protective immunity following interruption after polarization with Nippostrongylus brasiliensis primary infection. Moreover, we show by temporal deletion of IL-4Rα prior to secondary infection with N. brasiliensis that signaling via this receptor drives more efficient recall of type 2 immune responses and clearance of the parasites. Together, this study demonstrates that sustained IL-4Rα mediated signaling is required for the maintenance of anti-nematode type 2 immune responses, describing a novel function for IL-4Rα that is distinct from its role in immune polarization.

Granulomas and Inflammation: Host-Directed Therapies for Tuberculosis.

Tuberculosis (TB) remains a leading global health problem that is aggravated by emergence of drug-resistant strains, which account for increasing number of treatment-refractory cases. Thus, eradication of this disease will strongly require better therapeutic strategies. Identification of host factors promoting disease progression may accelerate discovery of adjunct host-directed therapies (HDTs) that will boost current treatment protocols. HDTs focus on potentiating key components of host anti-mycobacterial effector mechanisms, and limiting inflammation and pathological damage in the lung. Granulomas represent a pathological hallmark of TB. They are comprised of impressive arrangement of immune cells that serve to contain the invading pathogen. However, granulomas can also undergo changes, developing caseums and cavities that facilitate bacterial spread and disease progression. Here, we review current concepts on the role of granulomas in pathogenesis and protective immunity against TB, drawing from recent clinical studies in humans and animal models. We also discuss therapeutic potential of inflammatory pathways that drive granuloma progression, with a focus on new and existing drugs that will likely improve TB treatment outcomes.

Inducible deletion of CD28 prior to secondary nippostrongylus brasiliensis infection impairs worm expulsion and recall of protective memory CD4⁺ T cell responses.

IL-13 driven Th2 immunity is indispensable for host protection against infection with the gastrointestinal nematode Nippostronglus brasiliensis. Disruption of CD28 mediated costimulation impairs development of adequate Th2 immunity, showing an importance for CD28 during the initiation of an immune response against this pathogen. In this study, we used global CD28⁻/⁻ mice and a recently established mouse model that allows for inducible deletion of the cd28 gene by oral administration of tamoxifen (CD28(-/lox)Cre⁺/⁻+TM) to resolve the controversy surrounding the requirement of CD28 costimulation for recall of protective memory responses against pathogenic infections. Following primary infection with N. brasiliensis, CD28⁻/⁻ mice had delayed expulsion of adult worms in the small intestine compared to wild-type C57BL/6 mice that cleared the infection by day 9 post-infection. Delayed expulsion was associated with reduced production of IL-13 and reduced serum levels of antigen specific IgG1 and total IgE. Interestingly, abrogation of CD28 costimulation in CD28(-/lox)Cre⁺/⁻ mice by oral administration of tamoxifen prior to secondary infection with N. brasiliensis resulted in impaired worm expulsion, similarly to infected CD28⁻/⁻ mice. This was associated with reduced production of the Th2 cytokines IL-13 and IL-4, diminished serum titres of antigen specific IgG1 and total IgE and a reduced CXCR5⁺ T(FH) cell population. Furthermore, total number of CD4⁺ T cells and B220⁺ B cells secreting Th1 and Th2 cytokines were significantly reduced in CD28⁻/⁻ mice and tamoxifen treated CD28(-/lox)Cre⁺/⁻ mice compared to C57BL/6 mice. Importantly, interfering with CD28 costimulatory signalling before re-infection impaired the recruitment and/or expansion of central and effector memory CD4⁺ T cells and follicular B cells to the draining lymph node of tamoxifen treated CD28(-/lox)Cre⁺/⁻ mice. Therefore, it can be concluded that CD28 costimulation is essential for conferring host protection during secondary N. brasiliensis infection.