Cognate T and B cell interaction and association of follicular helper T cells with B cell responses in Vibrio cholerae O1 infected Bangladeshi adults

T follicular helper cell responses to SARS-CoV-2 vaccination among healthy and immunocompromised adults

The worldwide rollout of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations in the last 2 years has produced a multitude of studies investigating T-cell responses in the peripheral blood and a limited number in secondary lymphoid tissues. As a key component to an effective immune response, vaccine-specific T follicular helper (Tfh) cells are localized in the draining lymph node (LN) and assist in the selection of highly specific B-cell clones for the production of neutralizing antibodies. While these cells have been noted in the blood as circulating Tfh (cTfh) cells, they are not often taken into consideration when examining effective CD4+ T-cell responses, particularly in immunocompromised groups. Furthermore, site-specific analyses in locations such as the LN have recently become an attractive area of investigation. This is mainly a result of improved sampling methods via ultrasound-guided fine-needle biopsy (FNB)/fine-needle aspiration (FNA), which are less invasive than LN excision and able to be performed longitudinally. While these studies have been undertaken in healthy individuals, data from immunocompromised groups are lacking. This review will focus on both Tfh and cTfh responses after SARS-CoV-2 vaccination in healthy and immunocompromised individuals. This area of investigation could identify key characteristics of a successful LN response required for the prevention of infection and viral clearance. This furthermore may highlight responses that could be fine-tuned to improve vaccine efficacy within immunocompromised groups that are at a risk of more severe disease.

Vibrio cholerae, classification, pathogenesis, immune response, and trends in vaccine development

Vibrio cholerae is the causative agent of cholera, a highly contagious diarrheal disease affecting millions worldwide each year. Cholera is a major public health problem, primarily in countries with poor sanitary conditions and regions affected by natural disasters, where access to safe drinking water is limited. In this narrative review, we aim to summarize the current understanding of the evolution of virulence and pathogenesis of V. cholerae as well as provide an overview of the immune response against this pathogen. We highlight that V. cholerae has a remarkable ability to adapt and evolve, which is a global concern because it increases the risk of cholera outbreaks and the spread of the disease to new regions, making its control even more challenging. Furthermore, we show that this pathogen expresses several virulence factors enabling it to efficiently colonize the human intestine and cause cholera. A cumulative body of work also shows that V. cholerae infection triggers an inflammatory response that influences the development of immune memory against cholera. Lastly, we reviewed the status of licensed cholera vaccines, those undergoing clinical evaluation, and recent progress in developing next-generation vaccines. This review offers a comprehensive view of V. cholerae and identifies knowledge gaps that must be addressed to develop more effective cholera vaccines.

Mucosal and systemic immune responses to Vibrio cholerae infection and oral cholera vaccines (OCVs) in humans: a systematic review

INTRODUCTION

Cholera is an enteric disease caused by Vibrio cholerae, a water-borne pathogen, and characterized by severe diarrhea. Vaccines have been recommended for use by the WHO in resource-limited settings. Efficacies of the currently licensed cholera vaccines are not optimal in endemic settings and low in children below the age of five, a section of the population most susceptible to the disease. Development of next generation of cholera vaccines would require a detailed understanding of the required protective immune responses.

AREA COVERED

In this review, we revisit clinical trials which are focused on the early transcriptional mucosal responses elicited during Vibrio cholerae infection and upon vaccination along with summarizing various components of the effector immune response against Vibrio cholerae.

EXPERT OPINION

The inability of currently licensed killed/inactivated vaccines to elicit key inflammatory pathways locally may explain their restricted efficacy in endemic settings. More studies are required to understand the immunogenicity of the live attenuated cholera vaccine in these regions. Various extrinsic and intrinsic factors influence anti-cholera immunity and need to be considered to develop region-specific next generation vaccines.

Cholera

Cholera was first described in the areas around the Bay of Bengal and spread globally, resulting in seven pandemics during the past two centuries. It is caused by toxigenic Vibrio cholerae O1 or O139 bacteria. Cholera is characterised by mild to potentially fatal acute watery diarrhoeal disease. Prompt rehydration therapy is the cornerstone of management. We present an overview of cholera and its pathogenesis, natural history, bacteriology, and epidemiology, while highlighting advances over the past 10 years in molecular epidemiology, immunology, and vaccine development and deployment. Since 2014, the Global Task Force on Cholera Control, a WHO coordinated network of partners, has been working with several countries to develop national cholera control strategies. The global roadmap for cholera control focuses on stopping transmission in cholera hotspots through vaccination and improved water, sanitation, and hygiene, with the aim to reduce cholera deaths by 90% and eliminate local transmission in at least 20 countries by 2030.

The Role of Different Circulating T Follicular Helper Cell Markers in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic incurable inflammatory autoimmune disease. T follicular helper (Tfh) cells expressing different markers play critical roles in the development of RA. However, their specific mechanisms of action and association with RA clinical parameters are not clear. We therefore performed a cohort study to investigate the effects of different Tfh cell markers on RA pathogenesis. We retrospectively reviewed clinical data from 30 patients diagnosed with RA and 30 healthy controls (HCs) who visited our hospital. Based on X-ray findings, the patients were divided into a joint bone erosion group (n = 17) and a non-erosive joint bone group (n = 13). Using flow cytometry, we determined the frequencies of five peripheral blood CD4⁺ Tfh cell types characterized by different markers, and examined these cell types for correlations with clinical parameters. RA patients exhibited higher frequencies of CD4⁺CXCR5⁺, CD4⁺CXCR5⁺ICOS⁺, CD4⁺CXCR5⁺OX40⁺, and CD4⁺CXCR5⁺CD40L⁺ Tfh cells than HCs. CD4⁺CXCR5⁺, CD4⁺CXCR5⁺CD40L⁺, and CD4⁺CXCR5⁺OX40⁺ Tfh cell frequencies positively correlated with disease activity score-28 with erythrocyte sedimentation rate (DAS28-ESR), while those of CD4⁺CXCR5⁺ and CD4⁺CXCR5⁺CD40L⁺ Tfh cells were related to rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibodies. In RA patients without joint bone erosion, CD4⁺CXCR5⁺CD40L⁺ Tfh cell frequencies were positively correlated with both RF and DAS28-ESR. Serum anti-CCP antibody levels and CD4⁺CXCR5⁺ICOS⁺ Tfh cell frequencies were also positively correlated. Circulating CD4⁺CXCR5⁺CD40L⁺ Tfh cells appear to play critical roles in RA pathogenesis, and restricting CD4⁺CXCR5⁺CD40L⁺ Tfh cells may be a therapeutic strategy for controlling RA.

Update on Environmental and Host Factors Impacting the Risk of Vibrio cholerae Infection

Vibrio cholerae is the causative agent of cholera, a diarrheal disease that kills tens of thousands of people each year. Cholera is transmitted primarily by the ingestion of drinking water contaminated with fecal matter, and a safe water supply remains out of reach in many areas of the world. In this Review, we discuss host and environmental factors that impact the susceptibility to V. cholerae infection and the severity of disease.

Interleukin-29 regulates T follicular helper cells by repressing BCL6 in rheumatoid arthritis patients

INTRODUCTION

We aimed to investigate whether Interleukin-29 (IL-29) directly affects T follicular helper (Tfh) cell frequency in rheumatoid arthritis (RA), which are both related to RA-specific antibody responses.

METHODS

Here, we explored the effect of IL-29 on Tfh cell production in RA patients using a combination of enzyme-linked immunosorbent assay (ELISA), flow cytometry (FCM), CD4+ T cell culture, western blotting, and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

We reported that serum IL-29 levels, peripheral blood CD4+CXCR5+ Tfh cell frequency, CD4+CXCR5+CD40L+ Tfh cell frequency, and IL-28 receptor (IL-28Rα) and IL-10 receptor (IL-10R2) levels in peripheral blood Tfh cells were higher in RA patients than in healthy controls (HCs). Serum IL-29 levels were positively correlated with peripheral blood CD4+CXCR5+CD40L+ Tfh cell frequency in RA patients, and both parameters also correlated with anti-cyclic citrullinated peptide (anti-CCP) antibodies. Furthermore, we showed that IL-29 may suppress Tfh cell differentiation in RA patients partly via decreased BCL6 level through reduced STAT3 activity.

CONCLUSIONS

Taken together, our findings reveal the regulatory effect of IL-29 on Tfh cells, which participate in the pathogenesis of RA and provide new targets for its clinical treatment. Key Points • There is an increase in circulating Tfh cells and IL-29 levels in RA patients, which are correlated to anti-CCP antibodies levels and may be associated with RA pathogenesis. • We show for the first time that IL-29 may contribute to RA by inhibiting Tfh cell production, through decreasing the activity of STAT3 and downregulating the expression of BCL6. • The use of IL-29 biologics in patients with RA inhibits the production of Tfh cells, may prevent progression in patients with RA, and provides new targets for clinical treatment.

Bacteria That Cause Enteric Diseases Stimulate Distinct Humoral Immune Responses

Bacterial enteric pathogens individually and collectively represent a serious global health burden. Humoral immune responses following natural or experimentally-induced infections are broadly appreciated to contribute to pathogen clearance and prevention of disease recurrence. Herein, we have compared observations on humoral immune mechanisms following infection with Citrobacter rodentium, the model for enteropathogenic Escherichia coli, Vibrio cholerae, Shigella species, Salmonella enterica species, and Clostridioides difficile. A comparison of what is known about the humoral immune responses to these pathogens reveals considerable variance in specific features of humoral immunity including establishment of high affinity, IgG class-switched memory B cell and long-lived plasma cell compartments. This article suggests that such variance could be contributory to persistent and recurrent disease.

Posttranslational Regulation of IL-23 Production Distinguishes the Innate Immune Responses to Live Toxigenic versus Heat-Inactivated Vibrio cholerae

Vibrio cholerae infection provides long-lasting protective immunity, while oral, inactivated cholera vaccines (OCV) result in more-limited protection. To identify characteristics of the innate immune response that may distinguish natural V. cholerae infection from OCV, we stimulated differentiated, macrophage-like THP-1 cells with live versus heat-inactivated V. cholerae with and without endogenous or exogenous cholera holotoxin (CT). Interleukin 23A gene (IL23A) expression was higher in cells exposed to live V. cholerae than in cells exposed to inactivated organisms (mean change, 38-fold; 95% confidence interval [95% CI], 4.0 to 42; P < 0.01). IL-23 secretion was also higher in cells exposed to live V. cholerae than in cells exposed to inactivated V. cholerae (mean change, 5.6-fold; 95% CI, 4.4 to 11; P < 0.001). This increase in IL-23 secretion was more marked than for other key innate immune cytokines (e.g., IL-1β and IL-6) and dependent on exposure to the combination of both live V. cholerae and CT. While IL-23 secretion was reduced following stimulation with either heat-inactivated wild-type V. cholerae or a live isogenic ctxAB mutant of V. cholerae, the addition of exogenous CT restored IL-23 secretion in combination with the live isogenic ctxAB mutant V. cholerae, but not when it was paired with stimulation by heat-inactivated V. cholerae The posttranslational regulation of IL-23 under these conditions was dependent on the activity of the cysteine protease cathepsin B. In humans, IL-23 promotes the differentiation of Th17 cells to T follicular helper cells, which maintain and support long-term memory B cell generation after infection. Based on these findings, the stimulation of IL-23 production may be a determinant of protective immunity following V. cholerae infection.IMPORTANCE An episode of cholera provides better protection against reinfection than oral cholera vaccines, and the reasons for this are still under study. To better understand this, we compared the immune responses of human cells exposed to live Vibrio cholerae with those of cells exposed to heat-killed V. cholerae (similar to the contents of oral cholera vaccines). We also compared the effects of active cholera toxin and the inactive cholera toxin B subunit (which is included in some cholera vaccines). One key immune signaling molecule, IL-23, was uniquely produced in response to the combination of live bacteria and active cholera holotoxin. Stimulation with V. cholerae that did not produce the active toxin or was killed did not produce an IL-23 response. The stimulation of IL-23 production by cholera toxin-producing V. cholerae may be important in conferring long-term immunity after cholera.