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.

IL-4Rα signaling in CD4+CD25+FoxP3+ T regulatory cells restrains airway inflammation via limiting local tissue IL-33.

Impaired tolerance to innocuous particles during allergic asthma has been linked to increased plasticity of FoxP3+ regulatory T cells (Tregs) reprogramming into pathogenic effector cells, thus exacerbating airway disease. However, failure of tolerance mechanisms is driven by Th2 inflammatory signals. Therefore, the in vivo role of canonical IL-4 receptor α (IL-4Rα) signaling, an essential driver of Th2-type airway responses to allergens, on the regulatory function of FoxP3+ Tregs in allergic asthma was explored. Here, we used transgenic Foxp3cre IL-4Rα-/lox and littermate control mice to investigate the role of IL-4 and IL-13 signaling via Tregs in house dust mite-induced (HDM-induced) allergic airway disease. We sensitized mice intratracheally on day 0, challenged them on days 6-10, and analyzed airway hyperresponsiveness (AHR), airway inflammation, mucus production, and cellular profile on day 14. In the absence of IL-4Rα responsiveness on FoxP3+ Tregs, exacerbated AHR and airway inflammation were shown in HDM-sensitized mice. Interestingly, reduced induction of FoxP3+ Tregs accompanied increased IL-33 alarmin production and type 2 innate lymphoid cell activation in the lung, exacerbating airway hyperreactivity and lung eosinophilia. Taken together, our findings indicate that IL-4Rα-unresponsive FoxP3+ Tregs result in exaggerated innate Th2-type, IL-33-dependent airway inflammation and a break in tolerance during allergic asthma.

Therapeutic and prophylactic deletion of IL-4Ra-signaling ameliorates established ovalbumin induced allergic asthma.

BACKGROUND: Allergic asthma is a chronic inflammatory airway disease driven predominantly by a TH 2 immune response to environmental allergens. IL-4Rα-signaling is essential for driving TH 2-type immunity to allergens. Anti-TH 2 therapies have the potential to effectively reduce airway obstruction and inflammation in allergic asthma. OBJECTIVE: We investigated potential therapeutic effects of selective inhibition of this pathway in mice with established allergic airway disease. We further investigated whether IL-4Rα disruption in systemically sensitized mice can prevent the onset of the disease. METHODS: We used RosacreERT2 IL-4Rα-/lox mice, a tamoxifen (TAM)-inducible IL-4Rα knockdown model to investigate the role of IL-4/IL-13 signaling prior to the onset of the disease and during the effector phase in the ovalbumin-induced allergic airway disease. RESULTS: Inducible deletion of IL-4Rα demonstrated therapeutic effects, on established allergic airway disease, and prevented the development of ovalbumin-induced airway hyperreactivity, eosinophilia, and goblet cell metaplasia in allergen-sensitized mice. Interestingly, IL-4Rα knockdown after allergic sensitization did not induce TH 17, a neutrophilic inflammatory response as observed in global IL-4Rα-deficient mice after intranasal allergen challenge. CONCLUSION: Abrogation of IL-4Rα signaling after allergic sensitization would have significant therapeutic benefit for TH 2-type allergic asthma.

Diagnostic accuracy of two multiplex real-time polymerase chain reaction assays for the diagnosis of meningitis in children in a resource-limited setting.

INTRODUCTION: Accurate etiological diagnosis of meningitis is important, but difficult in resource-limited settings due to prior administration of antibiotics and lack of viral diagnostics. We aimed to develop and validate 2 real-time multiplex PCR (RT-PCR) assays for the detection of common causes of community-acquired bacterial and viral meningitis in South African children. METHODS: We developed 2 multiplex RT- PCRs for detection of S. pneumoniae, N. meningitidis, H. influenzae, enteroviruses, mumps virus and herpes simplex virus. We tested residual CSF samples from children presenting to a local paediatric hospital over a one-year period, whose CSF showed an abnormal cell count. Results were compared with routine diagnostic tests and the final discharge diagnosis. We calculated accuracy of the bacterial RT-PCR assay compared to CSF culture and using World Health Organisation definitions of laboratory-confirmed bacterial meningitis. RESULTS: From 292 samples, bacterial DNA was detected in 12 (4.1%) and viral nucleic acids in 94 (32%). Compared to CSF culture, the sensitivity and specificity of the bacterial RT-PCR was 100% and 97.2% with complete agreement in organism identification. None of the cases positive by viral RT-PCR had a bacterial cause confirmed on CSF culture. Only 9/90 (10%) of patients diagnosed clinically as bacterial meningitis or partially treated bacterial meningitis tested positive with the bacterial RT-PCR. DISCUSSION: In this population the use of 2 multiplex RT-PCRs targeting 6 common pathogens gave promising results. If introduced into routine diagnostic testing, these multiplex RT-PCR assays would supplement other diagnostic tests, and have the potential to limit unnecessary antibiotic therapy and hospitalisation.

Evolution of antimicrobial resistance of Salmonella enteritidis (1972-2005).

With the extensive use of antibiotics in livestock production, surveillance revealed an increase in Salmonella resistance to the commonly used antimicrobials in veterinary and public health. This serious threat to health care is further exacerbated by the limited epidemiological information about the common zoonotic agent, Salmonella enteritidis, required to determine antibiotic therapy. The aim was to characterise the antimicrobial resistance patterns of S. enteritidis isolates across different timelines (1972-2005) with accompanying genetic changes being investigated. Thirty-seven stored S. enteritidis isolates were collected from the Central Veterinary Laboratory, Harare, with antimicrobial susceptibility determined against eight antibiotics. Plasmids were isolated to analyse any genetic variation. An overall significant increase in resistance (p < 0.05) to nalidixic acid (0% - 10%), ampicillin (14.3% - 50%), tetracycline (14.3% - 30%) and erythromycin (71.4% - 100%) was observed across the timeline. However, the highest rates of susceptibility were maintained for gentamicin, sulphamethoxazole-trimethoprim, kanamycin and chloramphenicol. We report an increase in multidrug resistance (MDR) of 14.2% - 50% with an increase in resistotypes and plasmid profiles across the timeline. Eleven plasmid profiles were obtained in the 37 isolates studied with a minority of isolates (21.6%, 8/37) harbouring a 54 kb plasmid, commonly serovar-specific. A concerning increase in antimicrobial resistance to commonly administered drugs was observed across the timeline. The surge in MDR is of great concern and implies the need for consistent antimicrobial stewardship. No correlation was observed between the plasmid and antibiotic profiles.