Mucosal-associated invariant T (MAIT) cells are known for their rapid effector functions and antibacterial immune protection. Here, we define the plasticity of interferon-γ (IFN-γ)–producing MAIT1 and interleukin-17A (IL-17A)–producing MAIT17 cell subsets in vivo. Whereas T-bet ⁺ MAIT1 cells remained stable in all experimental settings, after adoptive transfer or acute Legionella or Francisella infection, RORγt ⁺ MAIT17 cells could undergo phenotypic and functional conversion into both RORγt ⁺ T-bet ⁺ MAIT1/17 and RORγt ⁻ T-bet ⁺ MAIT1 cells. This plasticity ensured that MAIT17 cells played a dominant role in generating antibacterial MAIT1 responses in mucosal tissues. Single-cell transcriptomics revealed that MAIT17-derived MAIT1 cells were distinct from canonical MAIT1 cells yet could migrate out of mucosal tissues to contribute to the global MAIT1 pool in subsequent systemic infections. Human IL-17A–secreting MAIT cells also showed similar functional plasticity. Our findings have broad implications for understanding the role of MAIT cells in combatting infections and their potential utility in MAIT cell–targeted vaccines.

Serological testing (immunoassay) for Helicobacter pylori (H. pylori) is widely available and inexpensive, and does not require medication modifications before testing. It can also determine the type of infection, which helps with clinical diagnosis and treatment, and guides the use of medication. However, the performance of immunoblotting for the detection of H. pylori infections in different populations has still not been fully evaluated. We performed a retrospective analysis of patients in the Health Examination Center and Outpatient Department, from November 2017 to September 2020, at Peking Union Medical College Hospital. All the subjects were tested with the ¹³C-urea breath test (¹³C-UBT) and for IgG antibodies. A total of 1678 participants, including 1377 individuals who had undergone physical examinations, were recruited. The results of the immunoassay were significantly different from those of the ¹³C-UBT for all the subjects and outpatients (p < 0.001). For the physical examinations of individuals, the agreement between the immunoassay and the ¹³C-UBT was 0.64 (95%CI: 0.59–0.68; p < 0.001), and the H. pylori immunoassay demonstrated a sensitivity and specificity of 74.24% and 90.45%, respectively, with a positive predictive value of 71.01% and negative predictive value of 91.76%. In addition, in patients with gastric mucosal atrophy or early gastric cancer, antibody typing tests can also detect infected patients with missed UBT. The prevalence of H. pylori in Beijing was 26.8%, and the serological positivity rate for H. pylori in the population of Beijing was about 31.7% (25.1% in the physical examination population). The rate of H. pylori antibody positivity among patients with allergic diseases was 73.5%, which is significantly higher than that of the non-allergic disease population (29.3%, p < 0.001). In conclusion, H. pylori antibody typing testing can be applied as a specific test in the healthy physical examination population, and the test can be performed with the remaining serum during the physical examination.

The antifungal susceptibility profile and epidemiological cut-off values (ECOFFs) of Yarrowia lipolytica , a rare opportunistic yeast, remain unclear. We conducted a comprehensive multi-method study on clinical isolates from various central hospitals, based on the China Hospital Invasive Fungal Surveillance Network (2009–2022). Our objective was to evaluate the antifungal susceptibility of Y. lipolytica , establish its local ECOFFs (L-ECOFFs), and compare the performance of the ATB FUNGUS 3 (ATB), Sensititre YeastOne (SYO), and minimum inhibitory concentration (MIC) test strip (MTS) with that of the broth microdilution (BMD) method. L-ECOFFs were established using ECOFFinder, and we examined ERG11 mutations to assess the reliability of the L-ECOFFs. The L-ECOFF for fluconazole was 8 µg/mL. Non-wild-type isolates of antifungal drugs, such as flucytosine and azoles, were exclusively isolated from patients. Additionally, we detected that four strains with the ERG11 A395T mutation (azole MIC >L-ECOFF) may be associated with the exposure to azole drugs. For azoles, ATB showed the highest essential agreement with the BMD (98.18%–100%), followed by SYO (85.45%–100%). However, ATB could not detect susceptibility to echinocandins, while SYO exhibited the highest agreement (98.18%–100%) in detecting echinocandin susceptibility. Our findings indicate that acquired azole cross-resistance has emerged despite Y. lipolytica infections being rare. This research provides crucial antifungal susceptibility data and establishes the initial L-ECOFFs for Y. lipolytica . The SYO is recommended as the optimal laboratory antifungal susceptibility testing method for Y. lipolytica , followed by ATB, whereas the use of MTS requires caution. We hope that this study will facilitate improved clinical management of Y. lipolytica infections. IMPORTANCE: Yarrowia lipolytica , also known as Candida lipolytica , is an emerging opportunistic “rare pathogenic yeast”. Due to the limited data on its antifungal susceptibility, the clinical treatments become challenging. Based on the China Hospital Invasive Fungal Surveillance Network (2009–2022), we conducted a comprehensive multi-method study on clinical isolates from various central hospitals. This study is currently the largest study carried out to assess the antifungal susceptibility of Y. lipolytica . It is also the first to establish local epidemiological cut-off values (L-ECOFFs), identify its ERG11 mutations, and assess the consistency between the three prevalent commercial antifungal susceptibility testing methods and the broth microdilution method. We recommend the Sensititre YeastOne as the best option for antifungal susceptibility testing for Y. lipolytica , followed by the ATB FUNGUS 3. Nevertheless, practitioners should use the MIC test strip with discretion.

Moraxella catarrhalis, a commensal in the human nasopharynx, plays a significant role in the acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Its pathogenicity involves adherence to respiratory epithelial cells, leading to infection through a macropinocytosis-like mechanism. Previous investigations highlighted the diverse abilities of M. catarrhalis isolates with different phenotypes to adhere to and invade respiratory epithelial cells. This study used a murine COPD model and in vitro experiments to explore the factors influencing the pathogenicity of distinct phenotypes of M. catarrhalis. Transcriptome sequencing suggested a potential association between actin cytoskeleton regulation and the infection of lung epithelial cells by M. catarrhalis with different phenotypes. Electron microscopy and Western blot analyses revealed a decrease in filamentous actin (F-actin) expression upon infection with various M. catarrhalis phenotypes. Inhibition of actin polymerization indicated the involvement of F-actin dynamics in M. catarrhalis internalization, distinguishing it from the adhesion process. Notably, hindering F-actin polymerization impaired the internalization of M. catarrhalis. These findings contribute vital theoretical insights for developing preventive strategies and individualized clinical treatments for AECOPD patients infected with M. catarrhalis. The study underscores the importance of understanding the nuanced interactions between M. catarrhalis phenotypes and host lung epithelial cells, offering valuable implications for the management of AECOPD infections.