No abstract

Intestinal colonization by bacteria of oral origin has been correlated with several negative health outcomes, including inflammatory bowel disease. However, a causal role of oral bacteria ectopically colonizing the intestine remains unclear. Using gnotobiotic techniques, we show that strains of Klebsiella spp. isolated from the salivary microbiota are strong inducers of T helper 1 (TH1) cells when they colonize in the gut. These Klebsiella strains are resistant to multiple antibiotics, tend to colonize when the intestinal microbiota is dysbiotic, and elicit a severe gut inflammation in the context of a genetically susceptible host. Our findings suggest that the oral cavity may serve as a reservoir for potential intestinal pathobionts that can exacerbate intestinal disease.

Human T-cell leukemia virus type 1 (HTLV-1) infects CD4+ T cells and induces proliferation of infected cells in vivo, which leads to the onset of adult T-cell leukemia (ATL) in some infected individuals. The HTLV-1 bZIP factor (HBZ) gene, which is encoded in the minus strand of HTLV-1, plays critical roles in pathogenesis. In this study, RNA-seq and ChIP-seq analyses using HBZ transduced T cells revealed that HBZ upregulates the expression and promoter acetylation levels of a co-inhibitory molecule, T cell immunoglobulin and ITIM domain (TIGIT), in addition to those of regulatory T cells related genes, Foxp3 and Ccr4. TIGIT was expressed on CD4+ T cells from HBZ-transgenic (HBZ-Tg) mice, and on ATL cells and HTLV-1 infected CD4+ T cells of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in vivo. Expression of Blimp1 and IL-10 was upregulated in TIGIT+CD4+ cells of HBZ-Tg mice compared with TIGIT-CD4+ T cells, suggesting the correlation between TIGIT expression and IL-10 production. When CD4+ T cells from HBZ-Tg mice were stimulated with TIGIT’s ligand, CD155, their production of the inhibitory cytokine IL-10 was enhanced. Furthermore, dendritic cells from HBZ-Tg mice produced high levels of IL-10 after stimulation. These data suggest that HBZ alters immune system to suppressive state via TIGIT and IL-10. Importantly, TIGIT suppressed T-cell responses to another HTLV-1 virus protein, Tax, in vitro. Blocking of TIGIT and PD-1 slightly increased anti-Tax T-cell activity in some HAM/TSP patients. These results suggest that HBZ-induced TIGIT on HTLV-1 infected cells impairs T-cell responses to viral antigens. This study shows that HBZ-induced TIGIT plays a pivotal role in attenuating host immune responses and shaping a microenvironment favorable to HTLV-1.

We evaluated whether quantitative PCR (qPCR) and (1 → 3)-β-d-glucan assays could be used to differentiate Pneumocystis pneumonia (PCP) from Pneumocystis jirovecii colonization in immunocompromised patients with pulmonary infiltrates. A total of 40 bronchoalveolar lavage samples and 107 induced sputum samples from 147 patients who were suspected of having PCP were obtained for PCR detection of P. jirovecii. Diagnoses of definite PCP, probable PCP, pneumonia with P. jirovecii colonization (colonization) and pneumonia without colonization (non-colonization) were made in 11, 42, 15 and 60 patients, respectively. A PCP diagnosis was undetermined in 19 patients. The copy numbers, determined using qPCR, were significantly higher in definite PCP and probable PCP patients than in colonized patients. The area under the receiver-operating characteristic curve (AUC), sensitivity and specificity for discriminating definite PCP from colonization were 0.96, 100.0% and 80.0%, respectively, at a cut-off value of 1300 copies/mL. The values for discriminating probable PCP from colonization were 0.71, 66.7% and 73.3%, respectively, at a cut-off value of 340 copies/mL. β-d-glucan levels were significantly higher in patients with both definite PCP and probable PCP than in colonized patients. The AUC, sensitivity and specificity for discriminating definite PCP were 0.91, 100.0% and 80.0%, respectively, at a cut-off value of 15.6 pg/mL. The values for discriminating probable PCP were 0.78, 76.2% and 73.3%, respectively, at a cut-off value of 6.0 pg/mL. Both qPCR and the β-d-glucan assay displayed high accuracy for discriminating colonization from definite PCP and displayed moderate accuracy for discriminating colonization from probable PCP.

Allogeneic hematopoietic cell transplantation (allo-HCT) induces profound shifts in the intestinal bacterial microbiota. The dynamics of intestinal fungi and their impact on clinical outcomes during allo-HCT are not fully understood. Here, we combined parallel high-throughput fungal ITS1 amplicon sequencing, bacterial 16S amplicon sequencing, and fungal cultures of 1279 fecal samples from a cohort of 156 allo-HCT patients to reveal potential trans-kingdom dynamics and their association with patient outcomes. We saw that the overall density and the biodiversity of intestinal fungi were stable during allo-HCT, but the species composition changed drastically from day to day. We identified a subset of patients with fungal dysbiosis defined by culture positivity (n=53) and stable expansion of Candida parapsilosis complex species (n=19). They presented with distinct trans-kingdom microbiota profiles, characterized by a decreased intestinal bacterial biomass. These patients had worse overall survival and higher transplant-related mortality independent of candidemia. This expands our understanding of the clinical significance of the mycobiota and suggests that targeting fungal dysbiosis may help to improve long-term patient survival.