Pathobiont-responsive Th17 cells in gut-mouth axis provoke inflammatory oral disease and are modulated by intestinal microbiome.

Host immune response via Th17 cells against oral pathobionts is a key mediator in periodontitis development. However, where and how the Th17-type immune response is induced during the development of periodontitis is not well understood. Here, we demonstrate that gut translocation of the oral pathobiont Porphyromonas gingivalis (Pg) exacerbates oral pathobiont-induced periodontitis with enhanced Th17 cell differentiation. The oral pathobiont-responsive Th17 cells are differentiated in Peyer's patches and translocated systemically in the peripheral immune tissues. They are also capable of migrating to and accumulating in the mouth upon oral infection. Development of periodontitis via the oral pathobiont-responsive Th17 cells is regulated by the intestinal microbiome, and altering the intestinal microbiome composition with antibiotics affects the development of periodontitis. Our study highlights that pathobiont-responsive Th17 cells in the gut-mouth axis and the intestinal microbiome work together to provoke inflammatory oral diseases, including periodontitis.

Bacterial-induced maternal interleukin-17A pathway promotes autistic-like behaviors in mouse offspring.

Maternal immune activation (MIA) by an infection is considered to be an important environmental factor of fetal brain development. Recent animal model on MIA induced by polyinosinic:polycytidylic acid, a mimic of viral infection, demonstrates that maternal IL-17A signaling is required for the development of autism spectrum disorder (ASD)-like behaviors of offspring. However, there is little information on bacterial infection. In this study, we aim to elucidate the influence of MIA induced by lipopolysaccharide (LPS) to mimic a bacterial infection on fetal brain development. We demonstrated that LPS-induced MIA promoted ASD-like behaviors in mouse offspring. We further found that LPS exposure induced acute phase immune response: elevation of serum IL-17A levels in MIA mothers, upregulation of Il17a mRNA expression and increase of IL-17A-producing γδ T cells in the uterus, and upregulation of Il17ra mRNA expression in the fetal brain. Blocking of IL-17A in LPS-induced MIA ameliorated ASD-like behaviors in offspring. Our data suggest that bacterial-induced maternal IL-17A pathway promotes ASD-like behaviors in offspring.

Mild Heat Stress Affects on the Cell Wall Structure in Candida albicans Biofilm.

We previously reported that Candida albicans responded to mild heat stress in a range of temperature elevations simulating fever, and concluded that mild heat stress increases susceptibility to antifungal drugs. In this study, we show that mild heat stress causes a morphological change in hyphae during the process of biofilm formation. We found that mild heat stress extended the period of hyphal stage maintenance in C. albicans biofilm. Although the rate of hyphal change from yeast form to hyphal form reached the maximum within 3 hr, later, almost every cell quickly reverted to the yeast growth phase within 6 hr at 37°C but not at 39°C, or under mild heat stress. Electron microscopy using a smart specimen preparation technique revealed that mild heat stress significantly increased the thickness of the inner cell wall accompanied by a decrease in density of the outer cell wall in the hyphae of C. albicans biofilm. To identify the gene responsible for the morphological changes associated with mild heat stress, we performed microarray gene expression analysis. Eleven genes were upregulated and 17 genes were downregulated under mild heat stress in biofilm cells. The increased PHR1 gene expression in response to mild heat stress was confirmed in quantitative RT-PCR analysis. The mutant upregulated PHR1 expression showed the same sensitivity against antifungal drug micafungin as dependent on mild heat stress. Our findings point to possible therapeutic effects of hyperthermia as well as to the effect of fever during infections.

Th17 cells differentiated with mycelial membranes of Candida albicans prevent oral candidiasis.

Candida albicans is a human commensal that causes opportunistic infections. Th17 cells provide resistance against mucosal infection with C. albicans; however, the T cell antigens remain little known. Our final goal is to find effective T cell antigens of C. albicans that are responsible for immunotherapy against candidiasis. Here, we prepared fractions including cytosol, membrane and cell wall from yeast and mycelial cells. Proteins derived from a membrane fraction of mycelial cells effectively induced differentiation of CD4+ T cells into IL-17A-producing Th17 cells. To confirm the immunological response in vivo of proteins from mycelial membrane, we performed adoptive transfer experiments using ex vivo stimulated CD4+ T cells from IL-17A-GFP reporter mice. Mycelial membrane-differentiated CD4+ Th17 cells adoptively transferred intravenously prevented oral candidiasis by oral infection of C. albicans, compared with control anti-CD3-stimulated CD4+ T cells. This was confirmed by the clinical score and the number of neutrophils on the infected tissues. These data suggest that effective T cell antigens against candidiasis could be present in the membrane protein fraction of mycelial cells. The design of novel vaccination strategies against candidiasis will be our next step.

Identification of a Novel Alternatively Spliced Form of Inflammatory Regulator SWAP-70-Like Adapter of T Cells.

Activation of naive CD4+ T cells results in the development of several distinct subsets of effector Th cells, including Th2 cells that play a pivotal role in allergic inflammation and helminthic infections. SWAP-70-like adapter of T cells (SLAT), also known as Def6 or IBP, is a guanine nucleotide exchange factor for small GTPases, which regulates CD4+ T cell inflammatory responses by controlling Ca2+/NFAT signaling. In this study, we have identified a novel alternatively spliced isoform of SLAT, named SLAT2, which lacks the region encoded by exons 2-7 of the Def6 gene. SLAT2 was selectively expressed in differentiated Th2 cells after the second round of in vitro stimulation, but not in differentiated Th1, Th17, or regulatory T (Treg) cells. Functional assays revealed that SLAT2 shared with SLAT the ability to enhance T cell receptor- (TCR-) mediated activation of NFAT and production of IL-4 but was unable to enhance TCR-induced adhesion to ICAM-1. Ectopic expression of SLAT2 or SLAT in Jurkat T cells resulted in the expression of distinct forms of filopodia, namely, short versus long ones, respectively. These results demonstrate that modulating either SLAT2 or SLAT protein expression could play critical roles in cytokine production and actin reorganization during inflammatory immune responses.