Vibrio vulnificus infection induces the maturation and activation of dendritic cells with inflammatory Th17-polarizing ability

Early diagnosis and application of hemopurification combined with antibiotic therapy and surgical debridement for successful treatment of a child with Vibrio vulnificus necrotizing fasciitis and septic shock: a case report

BACKGROUND

Vibrio vulnificus (V. vulnificus) is a halophilic marine Gram-negative bacterium. Necrotizing fasciitis caused by V. vulnificus is a rapidly progressing clinical emergency often accompanied by septic shock. Despite advances in antibiotics and infection control measures, it remains a highly fatal and disabling infection. The incidence of V. vulnificus infection has increased due to climate warming and expanded global seafood trade in recent years. However, pediatric cases of V. vulnificus infection remain rare, leading to limited clinical experience in their management.

METHODS

This report analyzes the clinical data of a pediatric case of V. vulnificus necrotizing fasciitis with septic shock, treated at Zhuhai Center for Maternal and Child Health Care in April 2024. The report also reviews the literature on pediatric V. vulnificus infection.

RESULTS

A 26-month-old boy developed a V. vulnificus infection after being scratched by a sea bass. The patient experienced an acute onset of illness that quickly worsened, presenting with a fever, mental fatigue, soft tissue edema, and pain, necrosis of the fascia and foot, coagulation dysfunction, and even shock. Laboratory results revealed white blood cell count(5.0 × 109/L), neutrophilia %(65%), thrombocytopenia (56 × 109/L), elevated CRP (200 mg/L), PCT (67.4 ng/mL), and IL-6 (> 4000 pg/mL), hypoalbuminemia (17.4 g/L), prolonged PT (17.5 s), reduced total T and NK cell counts, and a significantly reduced proportion of Treg cells. Initial treatment included surgical debridement and drainage, empirical antibiotic therapy, and rapid diagnosis of V. vulnificus via bacterial wound culture. Next-generation sequencing (NGS) of the blood microbial macrogenome and high-throughput sequencing of wound microbial pathogens (MetCap) were performed. Antibiotics were selected based on drug sensitivity testing, accompanied by hemopurification and measures to prevent disseminated intravascular coagulation. The patient's condition stabilized gradually post-treatment, and he was discharged.

CONCLUSION

Prompt diagnosis is important for children with seafood exposure. Early hemopurification, surgical intervention, effective antibiotic therapy, and DIC prevention significantly improve prognosis and survival rates. These findings provide a practical reference for managing pediatric V. vulnificus infections.

miR-106b-5p induces immune imbalance of Treg/Th17 in immune thrombocytopenic purpura through NR4A3/Foxp3 pathway

BACKGROUND

Immune imbalance of regulatory T cells (Treg)/T helper 17 cells (Th17) contributes to the development of immune thrombocytopenic purpura (ITP). The dysregulation of miRNAs is important in the development of ITP. However, the role of miR-106b-5p in Treg/Th17 imbalance remains unknown in ITP.

MATERIALS AND METHODS

Peripheral blood was collected from patients with ITP and healthy controls, and CD4 + T cells were further isolated. miR-106b-5p, nuclear receptor subfamily 4 group A member 3 (NR4A3), forkhead box protein 3 (Foxp3), IL-17A, and TGF-β expressions were detected by qRT-PCR, western blot, or ELISA. The effect of miR-106b-5p on NR4A3 was detected by dual-luciferase reporter gene assay.

RESULTS

Compared with healthy controls, miR-106b-5p was elevated in peripheral blood of patients with ITP, and NR4A3 expression was decreased. sh-NR4A3 significantly decreased Foxp3 and TGF-β expressions, indicating that NR4A3 may regulate Treg differentiation via Foxp3. Additionally, NR4A3 was identified to be a target of miR-106b-5p, and miR-106b-5p was able to negatively modulate NR4A3 expression. Moreover, we found miR-106b-5p induced immune imbalance of Treg/Th17 through NR4A3. In vivo experiments revealed that silencing miR-106b-5p promoted Treg differentiation and increased the number of platelets, suggesting the relief of ITP.

CONCLUSION

miR-106b-5p regulated immune imbalance of Treg/Th17 in ITP through the NR4A3/Foxp3 pathway.

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

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.