Patients with Tuberculosis Have a Dysfunctional Circulating B-Cell Compartment, Which Normalizes following Successful Treatment

Evolving Approach to Clinical Cytometry for Immunodeficiencies and Other Immune Disorders

Primary immunodeficiencies were initially identified on the basis of recurrent, severe or unusual infections. Subsequently, it was noted that these diseases can also manifest with autoimmunity, autoinflammation, allergy, lymphoproliferation and malignancy, hence a conceptual change and their renaming as inborn errors of immunity. Ongoing advances in flow cytometry provide the opportunity to expand or modify the utility and scope of existing laboratory tests in this field to mirror this conceptual change. Here we have used the B cell subset, variably known as CD21low B cells, age-associated B cells and T-bet+ B cells, as an example to demonstrate this possibility.

Immune dysregulation of diabetes in tuberculosis

The rising prevalence of diabetes mellitus (DM) is undermining global efforts to eliminate tuberculosis (TB). Most studies found that patients with pulmonary TB and DM have more cavitary lung lesions, higher mycobacterial burden on the lungs, longer periods of infectiousness, and worse outcomes. Both human and animal studies indicate that TB-DM is associated with impaired innate and adaptive immune responses, resulting in delayed bacterial clearance. Similar observations have been noted in other infections, such as those caused by Klebsiella pneumoniae, where DM contributes to increased susceptibility and worse outcomes due to compromised immune functions including defective phagocytosis and impaired early immune cell recruitment. This review delves into the mechanisms of immune dysfunction in TB-DM, exploring how DM increases TB susceptibility and severity. By elucidating these complex interactions, this review aims to offer insights into more effective strategies for managing and improving outcomes for patients with this challenging comorbidity.

Know Your ABCs: Discovery, Differentiation, and Targeting of T-Bet+ B Cells

Since their first description in 2008, T-bet+ B cells have emerged as a clinically important B cell subset. Now commonly known as ABCs (Age-associated B Cells), they are uniquely characterized by their expression of the transcription factor T-bet. Indeed, this singular factor defines this B cell subset. This review will describe the discovery of T-bet+ B cells, their role in bacterial infection as T cell-independent (TI) plasmablasts, as well as long-term follicular helper T cell-dependent (TD) IgM+ and switched memory cells (i.e., T-bet+ ABCs), and later discoveries of their role(s) in diverse immunological responses. These studies highlight a critical, although limited, role of T-bet in IgG2a class switching, a function central to the cells' role in immunity and autoimmunity. Given their association with autoimmunity, pharmacological targeting is an attractive strategy for reducing or eliminating the B cells. T-bet+ ABCs express a number of characteristic cell surface markers, including CD11c, CD11b, CD73, and the adenosine 2a receptor (A2aR). Accordingly, A2aR agonist administration effectively targeted T-bet+ ABCs in vivo. Moreover, agonist treatment of lupus-prone mice reduced autoantibodies and disease symptoms. This latter work highlights the potential therapeutic use of adenosine agonists for treating autoimmune diseases involving T-bet+ ABCs.

Management of tuberculosis risk, screening and preventive therapy in patients with chronic autoimmune arthritis undergoing biotechnological and targeted immunosuppressive agents

Tuberculosis (TB) is the leading cause of death in the world from an infectious disease. Its etiologic agent, the Mycobacterium tuberculosis (Mtb), is a slow-growing bacterium that has coexisted in humans for thousands of years. According to the World Health Organization, 10.6 million new cases of TB and over 1 million deaths were reported in 2022. It is widely recognized that patients affected by chronic autoimmune arthritis such as rheumatoid arthritis (RA), psoriatic arthritis (PsA), and ankylosing spondylitis (AS) have an increased incidence rate of TB disease compared to the general population. As conceivable, the risk is associated with age ≥65 years and is higher in endemic regions, but immunosuppressive therapy plays a pivotal role. Several systematic reviews have analysed the impact of anti-TNF-α agents on the risk of TB in patients with chronic autoimmune arthritis, as well as for other biologic disease-modifying immunosuppressive anti-rheumatic drugs (bDMARDs) such as rituximab, abatacept, tocilizumab, ustekinumab, and secukinumab. However, the data are less robust compared to those available with TNF-α inhibitors. Conversely, data on anti-IL23 agents and JAK inhibitors (JAK-i), which have been more recently introduced for the treatment of RA and PsA/AS, are limited. TB screening and preventive therapy are recommended in Mtb-infected patients undergoing bDMARDs and targeted synthetic (ts)DMARDs. In this review, we evaluate the current evidence from randomized clinical trials, long-term extension studies, and real-life studies regarding the risk of TB in patients with RA, PsA, and AS treated with bDMARDs and tsDMARDs. According to the current evidence, TNF-α inhibitors carry the greatest risk of TB progression among bDMARDs and tsDMARDs, such as JAK inhibitors and anti-IL-6R agents. The management of TB screening and the updated preventive therapy are reported.

Intradermal versus subcutaneous immunization: Effects of administration route using a lipid-PLGA hybrid nanoparticle tuberculosis vaccine

Tuberculosis (TB) remains a significant global health challenge, latently affecting around a quarter of the global population. The sole licensed TB vaccine, Mycobacterium bovis Bacillus Calmette-Guérin (BCG), shows variable efficacy, particularly among adolescents and adults, underscoring the pressing need for more effective vaccination strategies. The administration route is crucial for vaccine efficacy, and administration via the skin, being rich in immune cells, may offer advantages over conventional subcutaneous routes, which lack direct access to abundant antigen-presenting cells. This study compared the immunogenic effects of intradermal versus subcutaneous administration of a candidate TB vaccine delivering a Ag85B-ESAT6-Rv2034 (AER) multiphase fusion recombinant protein, in lipid-poly(D,L-lactic-co-glycolic acid) (lipid-PLGA) nanoparticles in mice. In-depth evaluation of immune responses in splenocytes was performed using 27-marker spectral flow cytometry. Both routes elicited significant T-cell responses. However, intradermal administration uniquely increased polyfunctional CD4+ and CD8+ T-cells producing IL-2, IFNγ, and TNFα, associated with protection against TB. Additionally, it significantly increased CD69+ B-cell counts and induced higher AER-specific antibody titers, particularly IgG2a. These results underscore the superior immunogenic potential of intradermal vaccine administration by effectively inducing immune cells associated with TB protection, highlighting its significance in the development of new vaccine strategies.

Multi-dimensional analysis of B cells reveals the expansion of memory and regulatory B-cell clusters in humans living in rural tropical areas

B-cells play a critical role in the formation of immune responses against pathogens by acting as antigen-presenting cells, by modulating immune responses, and by generating immune memory and antibody responses. Here, we studied B-cell subset distributions between regions with higher and lower microbial exposure, i.e. by comparing peripheral blood B-cells from people living in Indonesia or Ghana to those from healthy Dutch residents using a 36-marker mass cytometry panel. By applying an unbiased multidimensional approach, we observed differences in the balance between the naïve and memory compartments, with higher CD11c+ and double negative (DN-IgDnegCD27neg) memory (M)B-cells in individuals from rural tropical areas, and conversely lower naïve B-cells compared to residents from an area with less pathogen exposure. Furthermore, characterization of total B-cell populations, CD11c+, DN, and Breg cells showed the emergence of specific memory clusters in individuals living in rural tropical areas. Some of these differences were more pronounced in children compared to adults and suggest that a higher microbial exposure accelerates memory B-cell formation, which "normalizes" with age.

Evaluation of PLGA, lipid-PLGA hybrid nanoparticles, and cationic pH-sensitive liposomes as tuberculosis vaccine delivery systems in a Mycobacterium tuberculosis challenge mouse model - A comparison

Tuberculosis (TB) continues to pose a global threat for millennia, currently affecting over 2 billion people and causing 10.6 million new cases and 1.3 million deaths annually. The only existing vaccine, Mycobacterium Bovis Bacillus Calmette-Guérin (BCG), provides highly variable and inadequate protection in adults and adolescents. This study explores newly developed subunit tuberculosis vaccines that use a multistage protein fusion antigen Ag85b-ESAT6-Rv2034 (AER). The protection efficacy, as well as in vivo induced immune responses, were compared for five vaccines: BCG; AER-CpG/MPLA mix; poly(D,L-lactic-co-glycolic acid) (PLGA); lipid-PLGA hybrid nanoparticles (NPs); and cationic pH-sensitive liposomes (the latter three delivering AER together with CpG and MPLA). All vaccines, except the AER-adjuvant mix, induced protection in Mycobacterium tuberculosis (Mtb)-challenged C57/Bl6 mice as indicated by a significant reduction in bacterial burden in lungs and spleens of the animals. Four AER-based vaccines significantly increased the number of circulating multifunctional CD4+ and CD8+ T-cells producing IL-2, IFNγ, and TNFα, exhibiting a central memory phenotype. Furthermore, AER-based vaccines induced an increase in CD69+ B-cell counts as well as high antigen-specific antibody titers. Unexpectedly, none of the observed immune responses were associated with the bacterial burden outcome, such that the mechanism responsible for the observed vaccine-induced protection of these vaccines remains unclear. These findings suggest the existence of non-classical protective mechanisms for Mtb infection, which could, once identified, provide interesting targets for novel vaccines.

The problem that residual Mycobacterium bovis infection poses for the eradication of bovine tuberculosis

The dynamics of Mycobacterium bovis infection in cattle can influence the proportion of infected animals that are diagnosed by ante-mortem tests in routine bovine tuberculosis (bTB) surveillance and monitoring programmes. Although the current diagnostic tests based on cell-mediated or serological responses are imperfect, they are effective in diagnosing the majority of infected animals. However, the lack of perfect sensitivity and specificity also leads to failure to diagnose all infected animals leading to persistence of infection in herds. The terms residual, subclinical, latent and anergy have been used interchangeably to denote the presence of continued undiagnosed M. bovis infection within cattle herds, which ultimately hinders the eradication of bTB and imposes substantial financial burdens on farming communities and national economies. Epidemiological data suggests the existence of M. bovis-infected, but often undetected, cattle within herds that contribute to eradication failure. This has similarities with human tuberculosis, caused by Mycobacterium tuberculosis, where latent infection is defined as the persistence of viable but quiescent bacilli for extended periods in patients without clinical symptoms but with a detectable immune response to M. tuberculosis antigens. If a similar infection state exists in cattle infected with M. bovis, the persistence of such animals in disease-managed herds is unlikely to be common given that those found to have positive immune responses to M. bovis antigens are routinely culled to minimise future risk of transmission. Apart from contributing to the burden of herd infection, such residual infection without detection may also 'seed' recipient herds following animal movements, and potentially play an important role in the overall epidemiology of bTB as the prevalence of disease decreases and the attendant altered predictive value of the diagnostic tests result in a greater proportion of infected animals remaining undetected. This review examines how the different stages of M. bovis infection in cattle may contribute to the failure to diagnose infected animals using conventional testing methodologies and the attendant risk this poses in creating prolonged or recurrent herd breakdowns.

B Cell and Antibody Responses in Bovine Tuberculosis

The development of vaccines and effective diagnostic methods for bovine tuberculosis requires an understanding of the immune response against its causative agent, Mycobacterium bovis. Although this disease is primarily investigated and diagnosed through the assessment of cell-mediated immunity, the role of B cells and antibodies in bovine tuberculosis has been relatively undervalued and understudied. Current evidence indicates that circulating M. bovis-specific antibodies are not effective in controlling the disease. However, local humoral immune responses may contribute to either defence or pathology. Recent studies in animal models and cattle vaccine trials suggest a potential beneficial role of B cells in tuberculosis control. This review discusses the role of B cells and antibodies in bovine tuberculosis and explores antibody-based diagnostics for the disease, including traditional techniques, such as different ELISA, new platforms based on multiple antigens and point-of-care technologies. The high specificity and sensitivity values achieved by numerous antibody-based tests support their use as complementary tests for the diagnosis of bovine tuberculosis, especially for identifying infected animals that may be missed by the official tests.

Cationic pH-sensitive liposome-based subunit tuberculosis vaccine induces protection in mice challenged with Mycobacterium tuberculosis

Tuberculosis (TB) has been and still is a global emergency for centuries. Prevention of disease through vaccination would have a major impact on disease prevalence, but the only available current vaccine, BCG, has insufficient impact. In this article, a novel subunit vaccine against TB was developed, using the Ag85B-ESAT6-Rv2034 fusion antigen, two adjuvants - CpG and MPLA, and a cationic pH-sensitive liposome as a delivery system, representing a new TB vaccine delivery strategy not previously reported for TB. In vitro in human dendritic cells (DCs), the adjuvanted formulation induced a significant increase in the production of (innate) cytokines and chemokines compared to the liposome without additional adjuvants. In vivo, the new vaccine administrated subcutaneously significantly reduced Mycobacterium tuberculosis (Mtb) bacterial load in the lungs and spleens of mice, significantly outperforming results from mice vaccinated with the antigen mixed with adjuvants without liposomes. In-depth analysis underpinned the vaccine's effectiveness in terms of its capacity to induce polyfunctional CD4+ and CD8+ T-cell responses, both considered essential for controlling Mtb infection. Also noteworthy was the differential abundance of various CD69+ B-cell subpopulations, which included IL17-A-producing B-cells. The vaccine stimulated robust antigen-specific antibody titers, further extending its potential as a novel protective agent against TB.

Early B lymphocyte subsets in blood predict prognosis in sepsis

Background

B lymphocytes play a key role in immunosuppression. This study investigated the prognostic value of B cell subsets in sepsis.

Methods

Flow cytometry was used to assess peripheral B cell subsets from patients with sepsis on the first and seventh days following admission, as well as 111 healthy controls. The patients were divided into survivors and non-survivors, based on 28-day prognosis.

Results

The analysis showed abnormal distribution and selective depletion of B cells and its subsets in the early stages of sepsis. On day 1, compared with survivors, non-survivors showed significant decreases in the proportion and absolute count of transitional (Tr) B cells, reductions in the proportion of CD5+ B cells, and increases in the proportion of double-negative (DN) B cells. On day 7, the proportions and absolute counts of Tr and CD5+ B cells significantly decreased whereas the proportion of DN B cells significantly increased in non-survivors. Ninety-four survivors and 15 non-survivors were included in our paired-sample rank-sum test. Compared to day 1, only the survivors showed significant increases in absolute B, Tr B, and CD5+ B cell counts by day 7. Multivariate Cox regression analysis showed that the proportion of DN B cells on day 1 (hazard ratio = 1.092 [95% confidence interval: 1.035-1.152], P = 0.001) was a risk factor for mortality, and Kaplan-Meier survival curve analysis showed that patients with proportions of DN B cells > 11.81% on day 1 had poorer prognoses. Receiver operating characteristic curve analysis showed that B cell subset parameters could predict mortality (area under the receiver operating characteristic curve [AUC], 0.741) and enhanced the prognostic value of the Acute Physiology and Chronic Health Evaluation II score (AUC, 0.840).

Conclusion

Our study revealed that deficiencies of B, Tr B, and CD5+ B cells, as well as a persistent increase in the proportion of DN B cells, were associated with poor prognosis-and that B cell subsets showed predictive value to mortality. These results provide new insights into the roles of B cell subsets in sepsis, as well as ways to better manage its progression and predict its course.

A serum B-lymphocyte activation signature is a key distinguishing feature of the immune response in sarcoidosis compared to tuberculosis

Sarcoidosis and tuberculosis (TB) are two granulomatous diseases that often share overlapping clinical features, including uveitis. We measured 368 inflammation-related proteins in serum in both diseases, with and without uveitis from two distinct geographically separated cohorts: sarcoidosis from the Netherlands and TB from Indonesia. A total of 192 and 102 differentially expressed proteins were found in sarcoidosis and active pulmonary TB compared to their geographical healthy controls, respectively. While substantial overlap exists in the immune-related pathways involved in both diseases, activation of B cell activating factor (BAFF) signaling and proliferation-inducing ligand (APRIL) mediated signaling pathways was specifically associated with sarcoidosis. We identified a B-lymphocyte activation signature consisting of BAFF, TNFRSF13B/TACI, TRAF2, IKBKG, MAPK9, NFATC1, and DAPP1 that was associated with sarcoidosis, regardless of the presence of uveitis. In summary, a difference in B-lymphocyte activation is a key discriminative immunological feature between sarcoidosis/ocular sarcoidosis (OS) and TB/ocular TB (OTB).

Splenic marginal zone B cells restrict Mycobacterium tuberculosis infection by shaping the cytokine pattern and cell-mediated immunity

Understanding the role of B cells in tuberculosis (TB) is crucial for developing new TB vaccines. However, the changes in B cell immune landscapes during TB and their functional implications remain incompletely explored. Using high-dimensional flow cytometry to map the immune landscape in response to Mycobacterium tuberculosis (Mtb) infection, our results show an accumulation of marginal zone B (MZB) cells and other unconventional B cell subsets in the lungs and spleen, shaping an unconventional B cell landscape. These MZB cells exhibit activated and memory-like phenotypes, distinguishing their functional profiles from those of conventional B cells. Notably, functional studies show that MZB cells produce multiple cytokines and contribute to systemic protection against TB by shaping cytokine patterns and cell-mediated immunity. These changes in the immune landscape are reversible upon successful TB chemotherapy. Our study suggests that, beyond antibody production, targeting the regulatory function of B cells may be a valuable strategy for TB vaccine development.

Novel B-cell subsets as potential biomarkers in idiopathic inflammatory myopathies: insights into disease pathogenesis and disease activity

Idiopathic inflammatory myopathies are a heterogeneous group of rare autoimmune disorders characterized by progressive muscle weakness and the histopathologic findings of inflammatory infiltrates in muscle tissue. Although their pathogenesis remains indefinite, the association of autoantibodies with clinical manifestations and the evidence of high effectiveness of depleting therapies suggest that B cells could be implicated. Therefore, we explored the landscape of peripheral B cells in this disease by multiparametric flow cytometry, finding significant numerical decreases in memory and double-negative subsets, as well as an expansion of the naive compartment relative to healthy controls, that contribute to defining disease-associated B-cell subset signatures and correlating with different clinical features of patients. Additionally, we determined the potential value of these subsets as diagnostic biomarkers, thus positioning B cells as neglected key elements possibly participating in idiopathic inflammatory myopathy onset or development.

B cell heterogeneity in human tuberculosis highlights compartment-specific phenotype and functional roles

B cells are important in tuberculosis (TB) immunity, but their role in the human lung is understudied. Here, we characterize B cells from lung tissue and matched blood of patients with TB and found they are decreased in the blood and increased in the lungs, consistent with recruitment to infected tissue, where they are located in granuloma associated lymphoid tissue. Flow cytometry and transcriptomics identify multiple B cell populations in the lung, including those associated with tissue resident memory, germinal centers, antibody secretion, proinflammatory atypical B cells, and regulatory B cells, some of which are expanded in TB disease. Additionally, TB lungs contain high levels of Mtb-reactive antibodies, specifically IgM, which promotes Mtb phagocytosis. Overall, these data reveal the presence of functionally diverse B cell subsets in the lungs of patients with TB and suggest several potential localized roles that may represent a target for interventions to promote immunity or mitigate immunopathology.

Low-dose M.tb infection but not BCG or MTBVAC vaccination enhances heterologous antibody titres in non-human primates

Introduction

Mycobacteria are known to exert a range of heterologous effects on the immune system. The mycobacteria-based Freund's Complete Adjuvant is a potent non-specific stimulator of the immune response used in immunization protocols promoting antibody production, and Mycobacterium bovis Bacille Calmette Guérin (BCG) vaccination has been linked with decreased morbidity and mortality beyond the specific protection it provides against tuberculosis (TB) in some populations and age groups. The role of heterologous antibodies in this phenomenon, if any, remains unclear and under-studied.

Methods

We set out to evaluate antibody responses to a range of unrelated pathogens following infection with Mycobacterium tuberculosis (M.tb) and vaccination with BCG or a candidate TB vaccine, MTBVAC, in non-human primates.

Results

We demonstrate a significant increase in the titer of antibodies against SARS-CoV-2, cytomegalovirus, Epstein-Barr virus, tetanus toxoid, and respiratory syncytial virus antigens following low-dose aerosol infection with M.tb. The magnitude of some of these responses correlated with TB disease severity. However, vaccination with BCG administered by the intradermal, intravenous or aerosol routes, or intradermal delivery of MTBVAC, did not increase antibody responses against unrelated pathogens.

Discussion

Our findings suggest that it is unlikely that heterologous antibodies contribute to the non-specific effects of these vaccines. The apparent dysregulation of B cell responses associated with TB disease warrants further investigation, with potential implications for risk of B cell cancers and novel therapeutic strategies.

Single-Cell Sequencing Reveals Functional Alterations in Tuberculosis

Despite its importance, the functional heterogeneity surrounding the dynamics of interactions between mycobacterium tuberculosis and human immune cells in determining host immune strength and tuberculosis (TB) outcomes, remains far from understood. This work now describes the development of a new technological platform to elucidate the immune function differences in individuals with TB, integrating single-cell RNA sequencing and cell surface antibody sequencing to provide both genomic and phenotypic information from the same samples. Single-cell analysis of 23 990 peripheral blood mononuclear cells from a new cohort of primary TB patients and healthy controls enables to not only show four distinct immune phenotypes (TB, myeloid, and natural killer (NK) cells), but also determine the dynamic changes in cell population abundance, gene expression, developmental trajectory, transcriptomic regulation, and cell-cell signaling. In doing so, TB-related changes in immune cell functions demonstrate that the immune response is mediated through host T cells, myeloid cells, and NK cells, with TB patients showing decreased naive, cytotoxicity, and memory functions of T cells, rather than their immunoregulatory function. The platform also has the potential to identify new targets for immunotherapeutic treatment strategies to restore T cells from dysfunctional or exhausted states.

Atypical memory B cell frequency correlates with antibody breadth and function in malaria immune adults

Clinical immunity to malaria develops slowly after repeated episodes of infection and antibodies are essential in naturally acquired immunity against malaria. However, chronic exposure to malaria has been linked to perturbation in B-cell homeostasis with the accumulation of atypical memory B cells. It is unclear how perturbations in B cell subsets influence antibody breadth, avidity, and function in individuals naturally exposed to malaria. We show that individuals living in high malaria transmission regions in Ghana have higher Plasmodium falciparum merozoite antigen-specific antibodies and an increased antibody breadth score but lower antibody avidities relative to low transmission regions. The frequency of circulating atypical memory B cells is positively associated with an individual's antibody breadth. In vitro growth inhibition is independent of the ability to bind to free merozoites but associated with the breadth of antibody reactivity in an individual. Taken together, our data shows that repeated malaria episodes hamper the development of high avid antibodies which is compensated for by an increase in antibody breadth. Our results provide evidence to reinforce the idea that in regions with high malaria prevalence, repeated malaria infections lead to the broadening of antibody diversity and the continued presence of atypical memory B cell populations.

Comparison of the Single Cell Immune Landscape between Subjects with High Mycobacterium tuberculosis Bacillary Loads during Active Pulmonary Tuberculosis and Household Members with Latent Tuberculosis Infection

It is unclear how the immune system controls the transition from latent tuberculosis (TB) infection (LTBI) to active pulmonary infection (PTB). Here, we applied mass spectrometry cytometry time-of-flight (CyTOF) analysis of peripheral blood mononuclear cells to compare the immunological landscapes in patients with high tuberculous bacillary load PTB infections and LTBI. A total of 32 subjects (PTB [n = 12], LTBI [n = 17], healthy volunteers [n = 3]) were included. Participants with active PTBs were phlebotomized before administering antituberculosis treatment, whereas participants with LTBI progressed to PTB at the time of household screening. In the present study, CyTOF analysis identified significantly higher percentages of mucosal-associated invariant natural killer T (MAIT NKT) cells in subjects with LTBI than in those with active PTB and healthy controls. Moreover, 6 of 17 (35%) subjects with LTBI progressed to active PTB (LTBI progression) and had higher proportions of MAIT NKT cells and early NKT cells than those without progression (LTBI non-progression). Subjects with LTBI progression also showed a tendency toward low B cell levels relative to other subject groups. In conclusion, MAIT NKT cells were substantially more prevalent in subjects with LTBI, particularly those with progression to active PTB.

Recent advances in understanding the human host immune response in tuberculous meningitis

Tuberculous meningitis (TBM), the most severe form of tuberculosis, causes death in approximately 25% cases despite antibiotic therapy, and half of survivors are left with neurological disability. Mortality and morbidity are contributed to by a dysregulated immune response, and adjunctive host-directed therapies are required to modulate this response and improve outcomes. Developing such therapies relies on improved understanding of the host immune response to TBM. The historical challenges in TBM research of limited in vivo and in vitro models have been partially overcome by recent developments in proteomics, transcriptomics, and metabolomics, and the use of these technologies in nested substudies of large clinical trials. We review the current understanding of the human immune response in TBM. We begin with M. tuberculosis entry into the central nervous system (CNS), microglial infection and blood-brain and other CNS barrier dysfunction. We then outline the innate response, including the early cytokine response, role of canonical and non-canonical inflammasomes, eicosanoids and specialised pro-resolving mediators. Next, we review the adaptive response including T cells, microRNAs and B cells, followed by the role of the glutamate-GABA neurotransmitter cycle and the tryptophan pathway. We discuss host genetic immune factors, differences between adults and children, paradoxical reaction, and the impact of HIV-1 co-infection including immune reconstitution inflammatory syndrome. Promising immunomodulatory therapies, research gaps, ongoing challenges and future paths are discussed.

Emerging insights into atypical B cells in pediatric chronic infectious diseases and immune system disorders: T(o)-bet on control of B-cell immune activation

Repetitive or persistent cellular stimulation in vivo has been associated with the development of a heterogeneous B-cell population that exhibits a distinctive phenotype and, in addition to classical B-cell markers, often expresses the transcription factor T-bet and myeloid marker CD11c. Research suggests that this atypical population consists of B cells with distinct B-cell receptor specificities capable of binding the antigens responsible for their development. The expansion of this population occurs in the presence of chronic inflammatory conditions and autoimmune diseases where different nomenclatures have been used to describe them. However, as a result of the diverse contexts in which they have been investigated, these cells have remained largely enigmatic, with much ambiguity remaining regarding their phenotype and function in humoral immune response as well as their role in autoimmunity. Atypical B cells have garnered considerable interest because of their ability to produce specific antibodies and/or autoantibodies and because of their association with key disease manifestations. Although they have been widely described in the context of adults, little information is present for children. Therefore, the aim of this narrative review is to describe the characteristics of this population, suggest their function in pediatric immune-related diseases and chronic infections, and explore their potential therapeutic avenues.

Evolving Approach to Clinical Cytometry for Immunodeficiencies and Other Immune Disorders

Primary immunodeficiencies were initially identified on the basis of recurrent, severe or unusual infections. Subsequently, it was noted that these diseases can also manifest with autoimmunity, autoinflammation, allergy, lymphoproliferation and malignancy, hence a conceptual change and their renaming as inborn errors of immunity. Ongoing advances in flow cytometry provide the opportunity to expand or modify the utility and scope of existing laboratory tests in this field to mirror this conceptual change. Here we have used the B cell subset, variably known as CD21low B cells, age-associated B cells and T-bet+ B cells, as an example to demonstrate this possibility.

Molecular Markers of Early Immune Response in Tuberculosis: Prospects of Application in Predictive Medicine

Tuberculosis (TB) remains an important public health problem and one of the leading causes of death. Individuals with latent tuberculosis infection (LTBI) have an increased risk of developing active TB. The problem of the diagnosis of the various stages of TB and the identification of infected patients in the early stages has not yet been solved. The existing tests (the tuberculin skin test and the interferon-gamma release assay) are useful to distinguish between active and latent infections. But these tests cannot be used to predict the development of active TB in individuals with LTBI. The purpose of this review was to analyze the extant data of the interaction of M. tuberculosis with immune cells and identify molecular predictive markers and markers of the early stages of TB. An analysis of more than 90 sources from the literature allowed us to determine various subpopulations of immune cells involved in the pathogenesis of TB, namely, macrophages, dendritic cells, B lymphocytes, T helper cells, cytotoxic T lymphocytes, and NK cells. The key molecular markers of the immune response to M. tuberculosis are cytokines (IL-1β, IL-6, IL-8, IL-10, IL-12, IL-17, IL-22b, IFNɣ, TNFa, and TGFß), matrix metalloproteinases (MMP-1, MMP-3, and MMP-9), and their inhibitors (TIMP-1, TIMP-2, TIMP-3, and TIMP-4). It is supposed that these molecules could be used as biomarkers to characterize different stages of TB infection, to evaluate the effectiveness of its treatment, and as targets of pharmacotherapy.

Identification of circulating monocytes as producers of tuberculosis disease biomarker C1q

Tuberculosis (TB) is a prevalent disease causing an estimated 1.6 million deaths and 10.6 million new cases annually. Discriminating TB disease from differential diagnoses can be complex, particularly in the field. Increased levels of complement component C1q in serum have been identified as a specific and accessible biomarker for TB disease but the source of C1q in circulation has not been identified. Here, data and samples previously collected from human cohorts, a clinical trial and a non-human primate study were used to identify cells producing C1q in circulation. Cell subset frequencies were correlated with serum C1q levels and combined with single cell RNA sequencing and flow cytometry analyses. This identified monocytes as C1q producers in circulation, with a pronounced expression of C1q in classical and intermediate monocytes and variable expression in non-classical monocytes.

No impact of helminth coinfection in patients with smear positive tuberculosis on immunoglobulin levels using a novel method measuring Mycobacterium tuberculosis-specific antibodies

Helminth/tuberculosis (TB)-coinfection can reduce cell-mediated immunity against Mycobacterium tuberculosis (Mtb) and increase disease severity, although the effects are highly helminth species dependent. Mtb have long been ranked as the number one single infectious agent claiming the most lives. The only licensed vaccine for TB (BCG) offers highly variable protection against TB, and almost no protection against transmission of Mtb. In recent few years the identification of naturally occurring antibodies in humans that are protective during Mtb infection has reignited the interest in adaptive humoral immunity against TB and its possible implementation in novel TB vaccine design. The effects of helminth/TB coinfection on the humoral response against Mtb during active pulmonary TB are however still unclear, and specifically the effect by globally prevalent helminth species such as Ascaris lumbricoides, Strongyloides stercoralis, Ancylostoma duodenale, Trichuris trichiura. Plasma samples from smear positive TB patients were used to measure both total and Mtb-specific antibody responses in a Peruvian endemic setting where these helminths are dominating. Mtb-specific antibodies were detected by a novel approach coating ELISA-plates with a Mtb cell-membrane fraction (CDC1551) that contains a broad range of Mtb surface proteins. Compared to controls without helminths or TB, helminth/TB coinfected patients had high levels of Mtb-specific IgG (including an IgG1 and IgG2 subclass response) and IgM, which were similarly increased in TB patients without helminth infection. These data, indicate that helminth/TB coinfected have a sustained humoral response against Mtb at the level of active TB only. More studies on the species-specific impact of helminths on the adaptive humoral response against Mtb using a larger sample size, and in relation to TB disease severity, are needed.

Latent Tuberculosis Patients Have an Increased Frequency of IFN-γ-Producing CD5+ B Cells, Which Respond Efficiently to Mycobacterial Proteins

Tuberculosis (TB) remains a public health problem worldwide and is one of the deadliest infectious diseases, only after the current COVID-19 pandemic. Despite significant advances in the TB field, there needs to be more immune response comprehension; for instance, the role played by humoral immunity is still controversial. This study aimed to identify the frequency and function of B1 and immature/transitional B cells in patients with active and latent TB (ATB and LTB, respectively). Here we show that LTB patients have an increased frequency of CD5+ B cells and decreased CD10+ B cells. Furthermore, LTB patients stimulated with mycobacteria's antigens increase the frequency of IFN-γ-producing B cells, whereas cells from ATB do not respond. Moreover, under the mycobacterial protein stimulus, LTB promotes a pro-inflammatory environment characterized by a high level of IFN-γ but also can produce IL-10. Regarding the ATB group, they cannot produce IFN-γ, and mycobacterial lipids and proteins stimulate only the IL-10 production. Finally, our data showed that in ATB, but not in LTB, B cell subsets correlate with clinical and laboratory parameters, suggesting that these CD5+ and CD10+ B cell subpopulations have the potential to be biomarkers to differentiate between LTB and ATB. In conclusion, LTB has increased CD5+ B cells, and these cells can maintain a rich microenvironment of IFN-γ, IL-10, and IL-4. In contrast, ATB only maintains an anti-inflammatory environment when stimulated with mycobacterial proteins or lipids.

Role of B Cells in Mycobacterium Tuberculosis Infection

Historically, research on the immunologic response to Mycobacterium tuberculosis (M. tb) infection has focused on T cells and macrophages, as their role in granuloma formation has been robustly characterized. In contrast, the role of B cells in the pathophysiology of M. tb infection has been relatively overlooked. While T cells are well-known as an essential for granuloma formation and maintenance, B cells play a less understood role in the host response. Over the past decade, scarce research on the topic has attempted to elucidate the varying roles of B cells during mycobacterial infection, which appears to be primarily time dependent. From acute to chronic infection, the role of B cells changes with time as evidenced by cytokine release, immunological regulation, and histological morphology of tuberculous granulomas. The goal of this review is to carefully analyze the role of humoral immunity in M. tb infection to find the discriminatory nature of humoral immunity in tuberculosis (TB). We argue that there is a need for more research on the B-cell response against TB, as a better understanding of the role of B cells in defense against TB could lead to effective vaccines and therapies. By focusing on the B-cell response, we can develop new strategies to enhance immunity against TB and reduce the burden of disease.

Phenotypic characterization of Peripheral B cells in Mycobacterium tuberculosis infection and disease in Addis Ababa, Ethiopia

BACKGROUND

Mortality and morbidity from tuberculosis (TB) remain one of the most important public health issues. Although cell-mediated immunity is the main immune response against Mycobacterium tuberculosis (MTB), the role of B-cells during MTB infection and disease is unclear.

METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from treatment naïve Pulmonary TB patients (TB, n = 16), latent TB-infected participants (LTBI, n = 17), and healthy controls (HC, n = 19). PBMCs were stained with various fluorescently labeled antibodies to define B-cell subsets using multicolor flow cytometry.

RESULTS

Atypical memory B cells (CD19+CD27-CD21-) and circulating marginal zone B-cells (CD19+CD27+CD21+IgM+IgD+CD23-) were significantly higher in active TB when compared to LTBI and HC. CD5+ regulatory B cells (Breg, CD19+CD24hiCD38hiCD5+) and resting B-cells (CD19+CD27+CD21+) in Active TB patients were significantly lower compared to HC and LTBI. Overall, there were no differences in B cell percentages (CD19+), naïve B cells (CD19+CD27-CD21+), Breg (CD19+CD24hiCD38hi), and activated memory B cells (CD19+CD27+CD21-) among the three study groups.

CONCLUSIONS

These results indicated that multiple subsets of B cells were associated with TB infection and disease. It will be useful to examine these cell populations for their potential use as biomarkers for TB disease and LTBI.

The safety and immunogenicity of inactivated COVID-19 vaccine in old pulmonary tuberculosis patients

The immunogenicity and safety of vaccines against coronavirus disease 2019 (COVID-19) remain unknown in patients with a history of pulmonary tuberculosis (OPTB). Therefore, the safety and effectiveness of inactivated vaccines against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) were assessed in patients with a history of PTB. The study cohort included 106 healthy controls and 93 adult patients with OPTB who received a two-dose vaccination. The study period was 21 to 105 days. Concentrations of antibodies (Abs) against receptor-binding domain (RBD) IgG and SARS-CoV-2 neutralizing Abs (NAbs) were measured, in addition to the frequencies of SARS-CoV-2-specific B and a portion T cells. The incidence of adverse events was similar between the OPTB patients and healthy controls. No severe adverse events occurred. Concentrations of Abs against RBD-IgG and CoV-2 neutralizing Abs in addition to the frequencies of RBD-specific memory B cells proportions were lower in OPTB patients than the healthy controls (all, p < 0.05), while the frequencies of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4⁺) cells were higher (p = 0.023). There was no obvious correlation between age and blood concentrations of Abs against RBD-IgG and CoV-2 neutralizing Abs, while immune responses were similar in the fibrosis and calcification groups. The period of time following full-course vaccination and lymphocyte counts were associated to anti-RBD-IgG responses. Inactivated COVID-19 vaccinations were well tolerated in OPTB patients, although immunogenicity was limited in this population. This study has been registered at ClinicalTrials.gov (NCT05043246).

Multiparameter analysis of human B lymphocytes identifies heterogeneous CD19+ CD21lo subsets

Autoreactive B cell subsets have been described in a variety of settings, using multiple classification schemes and cell surface markers also found on healthy cells. CD19+ CD21lo B cells have been identified as an autoreactive-prone subset of B cells, although the downregulation of CD21 has been observed on a variety of B cell subsets in health and disease. This variation has led to confusion regarding the meaning and applicability of the loss or reduction of CD21 in peripheral B cells. To better understand the relationships between commonly used B cell markers and their associated characteristics, we analyzed human B cells from healthy participants using multiparameter flow cytometry and the visualization algorithm, tSNE. This approach revealed significant phenotypic overlap amongst five previously described autoimmune-prone B cell subsets, including CD19+ CD10- CD27- CD21lo B cells. Interestingly, 12 different subpopulations of CD19+ CD21lo B cells were identified, some of which mapped to previously described autoreactive populations, while others were consistent with healthy B cells. This suggests that CD21 is downregulated in a variety of circumstances involving B cell activation, all of which are present in low numbers even in healthy individuals. These findings describe the utility of unbiased multiparameter analysis using a relatively limited panel of flow cytometry markers to analyze autoreactive-prone and normal activated B cells.

T-bethighCD21low B cells: the need to unify our understanding of a distinct B cell population in health and disease

After many years of a niche research in a few laboratories of the world, T-bet^highCD21^low B cells have entered the limelight during the last years after the discovery of T-bet as common transcription factor of this unconventional B cell population and the increasing awareness of the expansion of these cells in autoimmune and infectious diseases. This population consists of different subsets which share large parts of their transcriptome, essential phenotypic markers, and reduced B cell receptor (BCR) signaling capacity. Inborn errors of immunity have helped to delineate essential signals for their differentiation. While our comprehension of their origin has improved, future research will hopefully profit from a common definition of the different T-bet^highCD21^low subpopulations in order to better define their specific roles during normal and aberrant immune responses.

Towards the development of subunit vaccines against tuberculosis: The key role of adjuvant

According to the World Health Organization (WHO), tuberculosis (TB) is the leading cause of death triggered by a single infectious agent, worldwide. Bacillus Calmette-Guerin (BCG) is the only currently licensed anti-TB vaccine. However, other strategies, including modification of recombinant BCG vaccine, attenuated Mycobacterium tuberculosis (Mtb) mutant constructs, DNA and protein subunit vaccines, are under extensive investigation. As whole pathogen vaccines can trigger serious adverse reactions, most current strategies are focused on the development of safe anti-TB subunit vaccines; this is especially important given the rising TB infection rate in immunocompromised HIV patients. The whole Mtb genome has been mapped and major antigens have been identified; however, optimal vaccine delivery mode is still to be established. Isolated protein antigens are typically poorly immunogenic so adjuvants are required to induce strong and long-lasting immune responses. This article aims to review the developmental status of anti-TB subunit vaccine adjuvants.

MMP9 and STAT1 are biomarkers of the change in immune infiltration after anti-tuberculosis therapy, and the immune status can identify patients with spinal tuberculosis

BACKGROUND

Due to a lack of studies on immune-related pathogenesis and a clinical diagnostic model, the diagnosis of Spinal Tuberculosis (STB) remains uncertain. Our study aimed to investigate the possible pathogenesis of STB and to develop a clinical diagnostic model for STB based on immune cell infiltration.

METHODS

Label-free quantification protein analysis of five pairs of specimens was used to determine the protein expression of the intervertebral disc in STB and non-STB. GO enrichment analysis, and KEGG pathway analysis were used to investigate the pathogenesis of STB. The Hub proteins were then eliminated. Four datasets were downloaded from the GEO database to analyze immune cell infiltration, and the results were validated using blood routine test data from 8535TB and 7337 non-TB patients. Following that, clinical data from 164 STB and 162 non-STB patients were collected. The Random-Forest algorithm was used to screen out clinical predictors of STB and build a diagnostic model. The differential expression of MMP9 and STAT1 in STB and controls was confirmed using immunohistochemistry.

RESULTS

MMP9 and STAT1 were STB Hub proteins that were linked to disc destruction in STB. MMP9 and STAT1 were found to be associated with Monocytes, Neutrophils, and Lymphocytes in immune cell infiltration studies. Data from 15,872 blood routine tests revealed that the Monocytes ratio and Neutrophils ratio was significantly higher in TB patients than in non-TB patients (p < 0.001), while the Lymphocytes ratio was significantly lower in TB patients than in non-TB patients (p < 0.001). MMP9 and STAT1 expression were downregulated following the anti-TB therapy. For STB, a clinical diagnostic model was built using six clinical predictors: MR, NR, LR, ESR, BMI, and PLT. The model was evaluated using a ROC curve, which yielded an AUC of 0.816.

CONCLUSIONS

MMP9 and STAT1, immune-related hub proteins, were correlated with immune cell infiltration in STB patients. MR, NR, LR ESR, BMI, and PLT were clinical predictors of STB. Thus, the immune cell Infiltration-related clinical diagnostic model can predict STB effectively.

COVID-19 pneumonia and the subsequent risk of getting active pulmonary tuberculosis: a population-based dynamic cohort study using national insurance claims databases

Background

A three-fold increase in the incidence of detecting pulmonary tuberculosis (PTB) in patients hospitalised with COVID-19 pneumonia compared with that in the general population was recently reported; however, this finding may be due to admission bias in the diagnostic investigation. The current cohort study aimed to estimate the risk of having detectable active PTB after SARS-CoV-2 infection.

Methods

Insurance claims data in lower Southern Thailand from the 12th regional National Health Security Office, Thailand, were used. Inpatient and outpatient electronic medical records were linked using encrypted identification numbers. Records of individuals aged ≥18 years from 1 April to 30 September 2021 were retrieved to form a dynamic cohort. Exposure status was based on SARS-CoV-2 investigation and pneumonia status: population control (general population who had never been tested), negative reverse transcription-polymerase chain reaction (RT-PCR) control, asymptomatic COVID-19, symptomatic COVID-19 without pneumonia, and COVID-19 pneumonia groups. They were tracked in the databases for subsequent bacteriologically confirmed PTB until 31 March 2022.

Findings

Overall, 4,241,201 individuals were recruited in the dynamic cohort and contributed 3,108,224, 227,918, 34,251, 10,325, and 14,160 person-years in the above exposure groups, respectively. Time-varying Cox's regression was conducted using population control as reference. Hazard ratios (95% CIs) of the negative control, asymptomatic, symptomatic COVID-19 without pneumonia, and pneumonia groups were 1.58 (1.08, 2.32), 1.00 (0.25, 4.01), 2.98 (0.74, 11.98), 9.87 (5.64, 17.30) in the first 30 days and 0.97 (0.81, 1.15), 1.41 (0.92, 2.17), 3.85 (2.42, 6.13), and 7.15 (5.54, 9.22) thereafter, respectively.

Interpretation

Having had COVID-19 pneumonia, as opposed to the general population status, was strongly associated with a higher hazard of detectable active PTB. In tuberculosis endemic areas, patients with COVID-19 pneumonia should be closely followed up to reduce PTB-related burden.

Funding

The Fogarty International Center and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health supported the article processing charges under Award Number D43TW009522.

HIV and COVID-19 Disease

Despite effective antiretroviral therapy (ART), HIV infected individuals throughout the world remain at significant risk of respiratory infections and non-communicable disease. Severe disease from SARS-CoV-2 is associated with a hyperinflammatory phenotype which manifests in the lungs as pneumonia and in some cases can lead to acute respiratory failure. Progression to severe COVID-19 is associated with comorbid disease such as obesity, diabetes mellitus and cardiovascular disease, however data concerning the associated risks of HIV coinfection are still conflicting, with large population studies demonstrating poorer outcomes, whilst smaller, case-controlled studies showing better outcomes. Furthermore, underlying immunopathological processes within the lungs and elsewhere, including interactions with other opportunistic infections (OI), remain largely undefined. Nonetheless, new and repurposed anti-viral therapies and vaccines which have been developed are safe to use in this population, and anti-inflammatory agents are recommended with the caveat that the coexistence of opportunistic infections is considered and excluded. Finally, HIV infected patients remain reliant on good ART adherence practices to maintain HIV viral suppression, and some of these practices were disrupted during the COVID-19 pandemic, putting these patients at further risk for acute and long-term adverse outcomes.

Identification of autoimmune markers in pulmonary tuberculosis

Introduction

Pathogenesis of many autoimmune diseases is mainly promoted by poorly regulated and/or wrong targeted immune response to pathogens including M. tuberculosis. Autoimmunity is one of the processes with are characteristics of tuberculosis (Tbc). The aim was to determine the autoimmune clinical and immunological features in patients with pulmonary Tbc.

Materials and methods

A prospective comparative study was performed in 2017 - 2019 with the inclusion of 46 patients with Tbc. The trigger factors and clinical manifestations, autoantibodies, peripheral blood B cell subsets were stained with fluorochrome-conjugated monoclonal antibodies. 40 healthy volunteers in the control group, were matched for age with no chronic diseases, contacts with TB patients and changes in their laboratory parameters. A statistical analysis was done with GraphPad Prism 6, Statistica 10 (Statsoft) and MedCalc - version 18.2.1 values.

Results

There were no significant ASIA triggers in Tbc patients and control group. 21.1% of Tbc patients had a high level of a rheumatoid factor and in 47.4% complement system factor C3 was high; anti-MCV was detected in 60.7% of Tbc patients. Relative and absolute frequencies of "naïve" Bm1 cells and eBm5 were significantly decreased and activated pre-germinal-center Bm2' cells were significantly increased in Tbc patients. The CD24++CD38++ B cells were increased in Tbc vs control group (10.25% vs 5.42%), p < 0.001, and 19 cell/1μL (10; 290 vs 11 cell/1μL (6; 20), p = 0.029, respectively). The frequency of CXCR3+CCR4- Tfh1 cells was significantly lower in Tbc vs control one (26.52% vs. 31.00%, p = 0.004), while CXCR3-CCR4+ Tfh2 cells were increased in Tbc (20.31% vs. controls (16.56%, p = 0.030). The absolute numbers of Tfh1 cells were decreased in the Tbc vs. control (24 cell/1μL vs. 37 cell/1μL p = 0.005).

Conclusion

The results of our study showed that the detection of a rheumatoid factor, the components of complement system and anti-MCV in complex with alterations in B cells and follicular Th cell subsets may indicate a presence of autoimmunity in the pathogenesis of tuberculosis, but they are not specific. The indicators of autoimmune-related provide new opportunities in the Tbc treatment.

Host biomarker-based quantitative rapid tests for detection and treatment monitoring of tuberculosis and COVID-19

Diagnostic services for tuberculosis (TB) are not sufficiently accessible in low-resource settings, where most cases occur, which was aggravated by the COVID-19 pandemic. Early diagnosis of pulmonary TB can reduce transmission. Current TB-diagnostics rely on detection of Mycobacterium tuberculosis (Mtb) in sputum requiring costly, time-consuming methods, and trained staff. In this study, quantitative lateral flow (LF) assays were used to measure levels of seven host proteins in sera from pre-COVID-19 TB patients diagnosed in Europe and latently Mtb-infected individuals (LTBI), and from COVID-19 patients and healthy controls. Analysis of host proteins showed significantly lower levels in LTBI versus TB (AUC:0 · 94) and discriminated healthy individuals from COVID-19 patients (0 · 99) and severe COVID-19 from TB. Importantly, these host proteins allowed treatment monitoring of both respiratory diseases. This study demonstrates the potential of non-sputum LF assays as adjunct diagnostics and treatment monitoring for COVID-19 and TB based on quantitative detection of multiple host biomarkers.

Immune cell interactions in tuberculosis

Despite having been identified as the organism that causes tuberculosis in 1882, Mycobacterium tuberculosis has managed to still evade our understanding of the protective immune response against it, defying the development of an effective vaccine. Technology and novel experimental models have revealed much new knowledge, particularly with respect to the heterogeneity of the bacillus and the host response. This review focuses on certain immunological elements that have recently yielded exciting data and highlights the importance of taking a holistic approach to understanding the interaction of M. tuberculosis with the many host cells that contribute to the development of protective immunity.

Distinct and shared B cell responses of tuberculosis patients and their household contacts

This study was aimed at identifying the B cell responses which could distinguish between 'latent tuberculosis infection (LTBI)' and active TB disease. Study subjects were smear-positive TB patients (n = 54) and their disease-free household contacts (HHCs, n = 120). The sera were used for determination of antibody levels (ΔOD values) against Mycobacterium tuberculosis membrane (MtM) antigens by ELISA and for visualisation of seroreactive MtM antigens by immunoblotting. B cell subsets in whole blood samples were determined by flow cytometry. In TB sera, levels of IgG antibodies were significantly higher than IgM and IgA whereas IgM and IgA antibody levels were comparable. Conversely, HHC sera had significantly higher IgM antibody levels than IgG and IgA. The ratio of IgM to IgG antibodies in HHCs were also significantly higher than in patients. Immunoblotting revealed that some of the MtM antigens (<10, ~12 and ~25 kDa) reacted with TB as well as HHC sera whereas some other antigens (~16, ~36, ~45 and ~60 kDa) reacted with most of TB and a subset of HHC sera. Frequencies of classical memory B cells (cMBCs, CD19+CD27+) were significantly higher, and of IgG+ cMBCs were significantly lower in HHCs than in patients. Frequencies of IgA+ cMBCs in HHCs and patients were comparable but both were significantly higher than the corresponding frequencies of IgG+ cMBCs. Frequencies of IgA+ atypical MBCs (aMBCs, CD19+CD27-) in HHCs and patients were also comparable and significantly higher than the IgG+ aMBCs. The plasmablast (CD19+CD27++CD38++) frequencies in HHCs and patients were comparable. These results suggest that the IgM/IgG antibody ratio, antibody binding to selected MtM antigens and relative frequencies of MBC subsets could indicate protective or pathogenic immune responses following the primary infection with Mtb. Responses that orchestrate protection leading to a 'quiescent' LTBI may provide clues to an effective vaccination strategy against TB.

Impact of Mycobacterium tuberculosis Infection on Human B Cell Compartment and Antibody Responses

Tuberculosis (TB) remains one of the most important health challenges worldwide. Control of the TB epidemic has not yet been achieved because of the lack of an effective vaccine and rapid and sensitive diagnostic approaches, as well as the emergence of drug-resistant forms of M. tuberculosis. Cellular immunity has a pivotal role against M. tuberculosis infection, but the role of humoral immunity is still controversial. We analyzed the frequency, absolute counts, and phenotypic and functional subsets of B lymphocytes in the peripheral blood of patients with active TB and subjects with latent infection compared to healthy donors. Moreover, we analyzed serum levels of total Ig and their IgA, IgM, and IgG isotypes and the titers of preexisting antibodies against a pool of common viral pathogens. FlowCT and unsupervised clusterization analysis show that patients with active TB and LTBI subjects have modest non-significant reduction in the numbers of circulating B lymphocytes as compared to healthy donors. Moreover, LTBI subjects had high percentages of atypical B cell population and lower percentages of naive and switched memory B cells. These findings were supported by gene expression and GSEA analysis. Moreover, there were no differences between active TB patients, LTBI subjects and HD, either in serum levels of total Ig isotypes or in preexisting IgG antibody titers, to ten different antigens from eight common pathogenic viruses, clearly demonstrating that either active or latent M. tuberculosis infection preserves the antibody production capacity of long-lived plasma cells. Thus, our results agree with previous studies reporting unaltered B cell frequencies in the blood of active TB patients and LTBI individuals as compared to healthy controls.

Similar Antibody Responses Against Severe Acute Respiratory Syndrome Coronavirus 2 in Individuals Living Without and With Human Immunodeficiency Virus on Antiretroviral Therapy During the First South African Infection Wave

BACKGROUND

There is limited understanding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogenesis in African populations with a high burden of infectious disease comorbidities such as human immunodeficiency virus (HIV). The kinetics, magnitude, and duration of virus-specific antibodies and B-cell responses in people living with HIV (PLWH) in sub-Saharan Africa have not been fully characterized.

METHODS

We longitudinally followed SARS-CoV-2-infected individuals in Durban, KwaZulu-Natal, South Africa, and characterized SARS-CoV-2 receptor-binding domain-specific immunoglobulin (Ig) M, IgG, and IgA weekly for 1 month and at 3 months post-diagnosis. Thirty of 72 (41.7%) were PLWH, 25/30 (83%) of whom were on antiretroviral therapy (ART) with full HIV suppression. Plasma neutralization was determined using a live virus neutralization assay, and antibody-secreting cell population frequencies were determined by flow cytometry.

RESULTS

Similar seroconversion rates, time to peak antibody titer, peak magnitude, and durability of anti-SARS-CoV-2 IgM, IgG, and IgA were observed in people not living with HIV and PLWH with complete HIV suppression on ART. In addition, similar potency in a live virus neutralization assay was observed in both groups. Loss of IgA was significantly associated with age (P = .023) and a previous diagnosis of tuberculosis (P = .018).

CONCLUSIONS

Similar antibody responses and neutralization potency in people not living with HIV and PLWH on stable ART in an African setting suggest that coronavirus disease 2019 (COVID-19) natural infections may confer comparable antibody immunity in these groups. This provides hope that COVID-19 vaccines will be effective in PLWH on stable ART.

Alternative B Cell Differentiation During Infection and Inflammation

Long-term protective immunity to infectious disease depends on cell-mediated and humoral immune responses. Induction of a strong humoral response relies on efficient B cell activation and differentiation to long-lived plasma cells and memory B cells. For many viral or bacterial infections, a single encounter is sufficient to induce such responses. In malaria, the induction of long-term immunity can take years of pathogen exposure to develop, if it occurs at all. This repeated pathogen exposure and suboptimal immune response coincide with the expansion of a subset of B cells, often termed atypical memory B cells. This subset is present at low levels in healthy individuals as well but it is observed to expand in an inflammatory context during acute and chronic infection, autoimmune diseases or certain immunodeficiencies. Therefore, it has been proposed that this subset is exhausted, dysfunctional, or potentially autoreactive, but its actual role has remained elusive. Recent reports have provided new information regarding both heterogeneity and expansion of these cells, in addition to indications on their potential role during normal immune responses to infection or vaccination. These new insights encourage us to rethink how and why they are generated and better understand their role in our complex immune system. In this review, we will focus on recent advances in our understanding of these enigmatic cells and highlight the remaining gaps that need to be filled.

Mechanism of COVID-19-Related Proteins in Spinal Tuberculosis: Immune Dysregulation

Purpose

The purpose of this article was to investigate the mechanism of immune dysregulation of COVID-19-related proteins in spinal tuberculosis (STB).

Methods

Clinical data were collected to construct a nomogram model. C-index, calibration curve, ROC curve, and DCA curve were used to assess the predictive ability and accuracy of the model. Additionally, 10 intervertebral disc samples were collected for protein identification. Bioinformatics was used to analyze differentially expressed proteins (DEPs), including immune cells analysis, Gene Ontology (GO) and KEGG pathway enrichment analysis, and protein-protein interaction networks (PPI).

Results

The nomogram predicted risk of STB ranging from 0.01 to 0.994. The C-index and AUC in the training set were 0.872 and 0.862, respectively. The results in the external validation set were consistent with the training set. Immune cells scores indicated that B cells naive in STB tissues were significantly lower than non-TB spinal tissues. Hub proteins were calculated by Degree, Closeness, and MCC methods. The main KEGG pathway included Coronavirus disease-COVID-19. There were 9 key proteins in the intersection of COVID-19-related proteins and hub proteins. There was a negative correlation between B cells naive and RPL19. COVID-19-related proteins were associated with immune genes.

Conclusion

Lymphocytes were predictive factors for the diagnosis of STB. Immune cells showed low expression in STB. Nine COVID-19-related proteins were involved in STB mechanisms. These nine key proteins may suppress the immune mechanism of STB by regulating the expression of immune genes.

Therapeutic Effect of Subunit Vaccine AEC/BC02 on Mycobacterium tuberculosis Post-Chemotherapy Relapse Using a Latent Infection Murine Model

Tuberculosis (TB), caused by the human pathogen Mycobacterium tuberculosis (Mtb), is an infectious disease that presents a major threat to human health. Bacillus Calmette-Guérin (BCG), the only licensed TB vaccine, is ineffective against latent TB infection, necessitating the development of further TB drugs or therapeutic vaccines. Herein, we evaluated the therapeutic effect of a novel subunit vaccine AEC/BC02 after chemotherapy in a spontaneous Mtb relapse model. Immunotherapy followed 4 weeks of treatment with isoniazid and rifapentine, and bacterial loads in organs, pathological changes, and adaptive immune characteristics were investigated. The results showed slowly increased bacterial loads in the spleen and lungs of mice inoculated with AEC/BC02 with significantly lower loads than those of the control groups. Pathological scores for the liver, spleen, and lungs decreased accordingly. Moreover, AEC/BC02 induced antigen-specific IFN-γ-secreting or IL-2-secreting cellular immune responses, which decreased with the number of immunizations and times. Obvious Ag85b- and EC-specific IgG were observed in mice following the treatment with AEC/BC02, indicating a significant Th1-biased response. Taken together, these data suggest that AEC/BC02 immunotherapy post-chemotherapy may shorten future TB treatment.

Atypical B cells up-regulate costimulatory molecules during malaria and secrete antibodies with T follicular helper cell support

Several infectious and autoimmune diseases are associated with an expansion of CD21-CD27- atypical B cells (atBCs) that up-regulate inhibitory receptors and exhibit altered B cell receptor (BCR) signaling. The function of atBCs remains unclear, and few studies have investigated the biology of pathogen-specific atBCs during acute infection. Here, we performed longitudinal flow cytometry analyses and RNA sequencing of Plasmodium falciparum (Pf)-specific B cells isolated from study participants before and shortly after febrile malaria, with simultaneous analysis of influenza hemagglutinin (HA)-specific B cells as a comparator. At the healthy baseline before the malaria season, individuals had similar frequencies of Pf- and HA-specific atBCs that did not differ proportionally from atBCs within the total B cell population. BCR sequencing identified clonal relationships between Pf-specific atBCs, activated B cells (actBCs), and classical memory B cells (MBCs) and revealed comparable degrees of somatic hypermutation. At the healthy baseline, Pf-specific atBCs were transcriptionally distinct from Pf-specific actBCs and classical MBCs. In response to acute febrile malaria, Pf-specific atBCs and actBCs up-regulated similar intracellular signaling cascades. Pf-specific atBCs showed activation of pathways involved in differentiation into antibody-secreting cells and up-regulation of molecules that mediate B-T cell interactions, suggesting that atBCs respond to T follicular helper (TFH) cells. In the presence of TFH cells and staphylococcal enterotoxin B, atBCs of malaria-exposed individuals differentiated into CD38+ antibody-secreting cells in vitro, suggesting that atBCs may actively contribute to humoral immunity to infectious pathogens.

Molecular mechanisms controlling age-associated B cells in autoimmunity

Age-associated B cells (ABCs) have emerged as critical components of immune responses. Their inappropriate expansion and differentiation have increasingly been linked to the pathogenesis of autoimmune disorders, aging-associated diseases, and infections. ABCs exhibit a distinctive phenotype and, in addition to classical B cell markers, often express the transcription factor T-bet and myeloid markers like CD11c; hence, these cells are also commonly known as CD11c+ T-bet+ B cells. Formation of ABCs is promoted by distinctive combinations of innate and adaptive signals. In addition to producing antibodies, these cells display antigen-presenting and proinflammatory capabilities. It is becoming increasingly appreciated that the ABC compartment exhibits a high degree of heterogeneity, plasticity, and sex-specific regulation and that ABCs can differentiate into effector progeny via several routes particularly in autoimmune settings. In this review, we will discuss the initial insights that have been obtained on the molecular machinery that controls ABCs and we will highlight some of the unique aspects of this control system that may enable ABCs to fulfill their distinctive role in immune responses. Given the expanding array of autoimmune disorders and pathophysiological settings in which ABCs are being implicated, a deeper understanding of this machinery could have important and broad therapeutic implications for the successful, albeit daunting, task of targeting these cells.

Leveraging Antibody, B Cell and Fc Receptor Interactions to Understand Heterogeneous Immune Responses in Tuberculosis

Despite over a century of research, Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), continues to kill 1.5 million people annually. Though less than 10% of infected individuals develop active disease, the specific host immune responses that lead to Mtb transmission and death, as well as those that are protective, are not yet fully defined. Recent immune correlative studies demonstrate that the spectrum of infection and disease is more heterogenous than has been classically defined. Moreover, emerging translational and animal model data attribute a diverse immune repertoire to TB outcomes. Thus, protective and detrimental immune responses to Mtb likely encompass a framework that is broader than T helper type 1 (Th1) immunity. Antibodies, Fc receptor interactions and B cells are underexplored host responses to Mtb. Poised at the interface of initial bacterial host interactions and in granulomatous lesions, antibodies and Fc receptors expressed on macrophages, neutrophils, dendritic cells, natural killer cells, T and B cells have the potential to influence local and systemic adaptive immune responses. Broadening the paradigm of protective immunity will offer new paths to improve diagnostics and vaccines to reduce the morbidity and mortality of TB.

Unbalanced serum immunoglobulins in clinical subtypes of pediatric tuberculosis disease

Immune response to tuberculosis (TB) has been extensively studied in the past decades and classically involves cellular immunity. However, evidence suggests that humoral immunity may play a relevant role. Past studies regarding serum immunoglobulin (Ig) levels in TB are dated and only involve adult subjects. In this study, we retrospectively studied a cohort of 256 children with TB disease and analyzed 111 patients screened for total serum Ig at diagnosis. According to the severity and extent of organ involvement, subjects were divided into four groups, namely, uncomplicated pulmonary TB (UCPTB, 56.3% of patients), complicated pulmonary TB (CPTB, 22.5%), lymph node extrapulmonary TB (LN-EPTB, 7.2%), and extra-nodal extrapulmonary TB (EN-EPTB, 13.5%). Serum IgG and IgA levels were significantly higher in more severe and extended TB disease. Median IgG levels progressively increased from uncomplicated to complicated pulmonary and nodal forms, reaching their highest values in diffuse extra-pulmonary TB. In parallel, UCPTB showed significantly lower frequencies of patients presenting a substantial increase in IgG levels when compared with the other three groups. No relevant differences in IgM levels were detected. Ig screening at follow-up showed a significant reduction in IgG and IgA levels. Finally, we unveiled three cases of selective IgA and one case of selective IgM deficiencies (SIgMD), the latter with a severe clinical course. Serum IgG and IgA may be a useful clinical tool to assess the severity and monitor the treatment response in pediatric TB disease. Moreover, immunological workup in children with TB disease may unmask primary defects of humoral immunity.

CD21- CD27- Atypical B Cells in a Pediatric Cohort Study: An Extensive Single Center Flow Cytometric Analysis

Atypical B cells (atBCs) are a distinct B-cell population and represent approximately 5% of B cells in peripheral blood (PB) of healthy adult individuals. However, in adults these cells are expanded in conditions of chronic infections, inflammation, primary immunodeficiencies, autoimmune diseases, and aging. Their immunophenotype is characterized by the lack of CD21 expression and the hallmark human memory B-cell marker CD27. In this study, we investigated the immunophenotype of atBCs in different pediatric pathological conditions and correlated their expansion with the children's clinical diagnosis. We were able to retrospectively evaluate 1,571 consecutive PB samples, corresponding to 1,180 pediatric patients, by using a 9-color flow-cytometric panel. The results, compared with a pediatric healthy cohort, confirmed an expansion of atBCs in patient samples with percentages greater than 5% of total B cells. Four subpopulations with different expressions of IgM and IgD were discriminated: IgM⁺IgD⁺, IgM⁺-only, IgD⁺-only, and IgM^-IgD^-. IgG⁺ atBCs were predominant in the IgM^- IgD^- subpopulation. Moreover, the study highlighted some features of atBCs, such as a low CD38 expression, a heterogeneity of CD24, a high expression of CD19 and a large cell size. We also demonstrated that an increase of atBCs in a pediatric cohort is correlated with immunodeficiencies, autoimmune, inflammatory, and hematological disorders, consistent with previous studies mainly performed in adults. Furthermore, our flow cytometric clustering analysis corroborated the recent hypothesis of an alternative B origin for atBCs.