Vibrio vulnificus RtxA Is a Major Factor Driving Inflammatory T Helper Type 17 Cell Responses in vitro and in vivo

Abstract

T helper type 17 (Th17) cells are a subset of pro-inflammatory T helper cells that mediate host defense and pathological inflammation. We have previously reported that host dendritic cells (DCs) infected with Vibrio vulnificus induce Th17 responses through the production of several pro-inflammatory cytokines, including interleukin (IL)-1β and IL-6. V. vulnificus produces RTX toxin (RtxA), an important virulence factor that determines successful pathophysiology. In this study, we investigated the involvement of RtxA from V. vulnificus in Th17 cell induction through the activation and maturation of DCs. The increased expression of the DC surface marker CD40 caused by V. vulnificus wild-type infection was reduced by rtxA gene mutation in V. vulnificus. The mRNA and protein levels of Th17 polarization-related cytokines also decreased in V. vulnificus rtxA mutant-infected DCs. In addition, the co-culture of Th cells and DCs infected with rtxA mutant V. vulnificus resulted in reduction in DC-mediated Th17 responses. Th17 cell responses in the small intestinal lamina propria decreased in mice inoculated with V. vulnificus rtxA mutant as compared to those inoculated with the wild-type strain. These decreases in DC maturation, Th17-polarizing cytokine secretion, and Th17 responses attributed to rtxA mutation were restored following infection with the rtxA revertant strain. Furthermore, the mutation in the hlyU gene encoding the activator of rtxA1 gene reproduced the results observed with rtxA mutation. Taken together, V. vulnificus, by means of RtxA, induces inflammatory Th17 responses, which may be associated with adaptive responses of the host against V. vulnificus infection.

MARTX toxin of Vibrio vulnificus induces RBC phosphatidylserine exposure that can contribute to thrombosis

“…The ΔrtxA mutant, which was constructed by deleting 89% of the rtxA structural gene and then inserting a nptI gene cassette conferring resistance to kanamycin into the deleted rtxA , produces no MARTX toxin 14 . The rtxA :: nptI mutant with the insertion of nptI at the 5′-end of rtxA also produces no MARTX toxin 47 . The revertant, in which the rtxA structural gene was restored from the rtxA :: nptI mutation, produces the WT-MARTX toxin 47 .…”

“…The rtxA :: nptI mutant with the insertion of nptI at the 5′-end of rtxA also produces no MARTX toxin 47 . The revertant, in which the rtxA structural gene was restored from the rtxA :: nptI mutation, produces the WT-MARTX toxin 47 . To construct the EF-rtxA mutant, the pDS_EF-MARTX 50 , carrying rtxA with the deletion of 34% structural gene encoding effector domains of the MARTX toxin, was conjugally transferred into the V. vulnificus WT and a resulting mutant by the double homologous recombination was screened out.…”

Staphylococcus succinus 14BME20 Prevents Allergic Airway Inflammation by Induction of Regulatory T Cells via Interleukin-10

“…Mice were orally administered with 200 μl PBS or bacterial suspension containing 5 × 10 7 CFU of 14BME20 for 10 days. Mice were sacrificed and mucosal dendritic cells (MDCs) were isolated from lamina propria of small intestines, as described previously (24). In brief, the small intestines from the PBS- or 14BME20-treated mice ( n = 3) were washed in cold PBS, and feces, fat tissues and Peyer's patches were removed.…”

Complex regulatory networks of virulence factors in Vibrio vulnificus

“…Based on its mode of action, the MARTX toxin is essential for V. vulnificus to improve antiphagocytosis, colonization, and dissemination to the bloodstream and other organs, and thereby lethality in mice [32,33]. Also, recent studies further revealed that the expression of the MARTX toxin moderates immune responses of gut epithelial cells but stimulates inflammatory signaling of immune cells [34][35][36].…”