Frequency and phenotype of B cell subpopulations in young and aged HIV-1 infected patients receiving ART

Impact of HIV-Related Immune Impairment of Yellow Fever Vaccine Immunogenicity in People Living with HIV-ANRS 12403

The yellow fever (YF) vaccine is one of the safest and most effective vaccines currently available. Still, its administration in people living with HIV (PLWH) is limited due to safety concerns and a lack of consensus regarding decreased immunogenicity and long-lasting protection for this population. The mechanisms associated with impaired YF vaccine immunogenicity in PLWH are not fully understood, but the general immune deregulation during HIV infection may play an important role. To assess if HIV infection impacts YF vaccine immunogenicity and if markers of immune deregulation could predict lower immunogenicity, we evaluated the association of YF neutralization antibody (NAb) titers with the pre-vaccination frequency of activated and exhausted T cells, levels of pro-inflammatory cytokines, and frequency of T cells, B cells, and monocyte subsets in PLWH and HIV-negative controls. We observed impaired YF vaccine immunogenicity in PLWH with lower titers of YF-NAbs 30 days after vaccination, mainly in individuals with CD4 count <350 cells/mm3. At the baseline, those individuals were characterized by having a higher frequency of activated and exhausted T cells and tissue-like memory B cells. Elevated levels of those markers were also observed in individuals with CD4 count between 500 and 350 cells/mm3. We observed a negative correlation between the pre-vaccination level of CD8+ T cell exhaustion and CD4+ T cell activation with YF-NAb titers at D365 and the pre-vaccination level of IP-10 with YF-NAb titers at D30 and D365. Our results emphasize the impact of immune activation, exhaustion, and inflammation in YF vaccine immunogenicity in PLWH.

Frequency of B-Cell Subpopulations in Low Responders in Comparison with High Responders to Hepatitis B Vaccine Among Health Care Workers

Vaccination is the most effective way to prevent Hepatitis B (HB) infection. The goal of vaccination is to induce immunological memory. Hence, determining the frequency of memory B-cell (MBC) subsets is an important indicator of vaccine efficacy. This study aimed to evaluate the frequency of different B-cell subpopulations and the expression of PD-1 on B-cell subsets in low responders (LR) and high responders (HR) to HB vaccine. According to our findings, the expression level of PD-1 was significantly higher on atypical MBC (atMBC) than that of naive B cell and classical MBC (cMBC) in LR and HR groups. Moreover, cMBCs had a significant higher PD-1 expression than naive B cells in LR group. No significant differences were found in the frequency of various B-cell subpopulations and the expression level of PD-1 on B-cell subsets between LR and HR groups. We observed a negative correlation between age and HBsAb titer and a positive correlation between age and PD-1 expression level on cMBC in LR group. It can be concluded that inadequate specific memory B-cell response, rather than total memory B-cell deficiency, may be implicated in low responsive rate to HB vaccine in healthy individuals.

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.

Strategies for Immunomonitoring after Vaccination and during Infection

Immunomonitoring is the study of an individual's immune responses over the course of vaccination or infection. In the infectious context, exploring the innate and adaptive immune responses will help to investigate their contribution to viral control or toxicity. After vaccination, immunomonitoring of the correlate(s) and surrogate(s) of protection is a major asset for measuring vaccine immune efficacy. Conventional immunomonitoring methods include antibody-based technologies that are easy to use. However, promising sensitive high-throughput technologies allowed the emergence of holistic approaches. This raises the question of data integration methods and tools. These approaches allow us to increase our knowledge on immune mechanisms as well as the identification of key effectors of the immune response. However, the depiction of relevant findings requires a well-rounded consideration beforehand about the hypotheses, conception, organization and objectives of the immunomonitoring. Therefore, well-standardized and comprehensive studies fuel insight to design more efficient, rationale-based vaccines and therapeutics to fight against infectious diseases. Hence, we will illustrate this review with examples of the immunomonitoring approaches used during vaccination and the COVID-19 pandemic.

A Longitudinal Analysis Reveals Early Activation and Late Alterations in B Cells During Primary HIV Infection in Mozambican Adults

Primary HIV infection (PHI) and subsequent chronic infection alter B-cell compartment. However, longitudinal analysis defining the dynamics of B-cell alterations are still limited. We longitudinally studied B-cell subsets in individuals followed for 1 year after PHI (n = 40). Treated and untreated chronic HIV infected (n = 56) and HIV-uninfected individuals (n = 58) were recruited as reference groups at the Manhiça District in Mozambique. B cells were analyzed by multicolor flow-cytometry. Anti-HIV humoral response and plasma cytokines were assessed by ELISA or Luminex-based technology. A generalized activation of B cells induced by HIV occurs early after infection and is characterized by increases in Activated and Tissue-like memory cells, decreases in IgM-IgD- (switched) and IgM-only B cells. These alterations remain mostly stable until chronic infection and are reverted in part by ART. In contrast, other parameters followed particular dynamics: PD-1 expression in memory cells decreases progressively during the first year of infection, Transitional B cells expand at month 3-4 after infection, and Marginal zone-like B cells show a late depletion. Plasmablasts expand 2 months after infection linked to plasma viral load and anti-p24 IgG3 responses. Most of well-defined changes induced by HIV in B-cell activation and memory subsets are readily observed after PHI, lasting until ART initiation. However, subsequent changes occur after sustained viral infection. These data indicate that HIV infection impacts B cells in several waves over time, and highlight that early treatment would result in beneficial effects on the B-cell compartment.

Human antiviral B cell responses: Emerging lessons from hepatitis B and COVID-19

Humoral immunity is a critical component of the coordinated response required to resolve viral infections and mediate protection following pathogen clearance or vaccination. A better understanding of factors shaping the memory B cell response will allow tailored development of efficient preventative vaccines against emerging acute viral infections, therapeutic vaccines, and immunotherapies for chronic viral infections. Here, we use recent data obtained by profiling antigen-specific B cell responses in hepatitis B as a framework to explore lessons that can be learnt from different viral infections about the diverse influences on humoral immunity. Hepatitis B provides a paradigm where successful B cell responses in resolved or vaccinated individuals can be contrasted to the failed response in chronic infection, while also exemplifying the degree to which B cell responses within infected individuals can differ to two antigens from the same virus. Drawing on studies in other human and murine infections, including emerging data from COVID-19, we consider the influence of antigen quantity and structure on the quality of the B cell response, the role of differential CD4 help, the importance of germinal center vs extrafollicular responses and the emerging concept that responses residing in non-lymphoid organs can participate in B cell memory.

Modulation of Memory B Cell Phenotypes and Toll-Like Receptor-7 in Chronic Hepatitis C Virus Infection During Direct-Acting Antiviral Interferon-Free Therapy: Correlation with Interleukin-7

Hepatitis C virus (HCV) infection is a major worldwide problem with the highest incidence rates in Egypt. It affects B cells that serve as reservoirs for persistent HCV, resulting in phenotypic B cell alterations. Interleukin-7 (IL-7) is a cytokine with antiviral activity, important for B cell physiology. In addition, B cell-intrinsic toll-like receptor-7 (TLR7) signaling is required for optimal B cell responses during chronic viral infection, and the deficiency of TLR7 in B cells is sufficient to significantly impact antibody responses. Based on their known immunomodulatory effects, we hypothesized that direct-acting antiviral interferon-free therapy may affect TLR7 expression and the exhausted peripheral B cell compartment with the possibility of their restoration in patients who achieved a sustained virological response and their correlation to IL-7 level. This prospective study was accomplished on 80 Egyptian HCV patients and 75 controls. Frequencies of peripheral B cell subsets, TLR7 gene expression, TLR7 protein, and serum IL-7 levels were investigated by flow cytometry, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay, respectively. B cell subpopulations were exhausted and partially restored among HCV patients after receiving treatment, but not recovered with regard to activated mature or resting memory B cells. Almost all responders to direct antiviral drugs showed upregulation of TLR7 gene expression and correlated with the frequency of memory B cell, but not with IL-7. Moreover, IL-7 was not significantly different between groups although correlated with immature transitional B cells. Results may indicate the interplay between TLR7 and B cells during remission or progression of HCV. Thus, TLR7 could be used as a promising biomarker for assessment of antiviral treatment efficacy among chronically infected HCV patients, and that targeting TLR7 may be used as a potential prophylactic and/or therapeutic agent during chronic HCV as well as immune-potentiation of memory B cells.

Dysregulation of humoral immunity in chronic infection

Chronic viral infections disrupt the ability of the humoral immune response to produce neutralizing antibody or form effective immune memory, preventing viral clearance and making vaccine design difficult. Multiple components of the B-cell response are affected by pathogens that are not cleared from the host. Changes in the microenvironment shift production of B cells to short-lived plasma cells early in the response. Polyclonal B cells are recruited into both the plasma cell and germinal center compartments, inhibiting the formation of a targeted, high-affinity response. Finally, memory B cells shift toward an "atypical" phenotype, which may in turn result in changes to the functional properties of this population. While similar properties of B-cell dysregulation have been described across different types of persistent infections, key questions about the underlying mechanisms remain. This review will discuss the recent advances in this field, as well as highlight the critical questions about the interplay between viral load, microenvironment, the polyclonal response and atypical memory B cells that are yet to be answered. Design of new preventative treatments will rely on identifying the extrinsic and intrinsic modulators that push B cells toward an ineffective response, and thus identify new ways to guide them back onto the best path for clearance of virus and formation of effective immune memory.

Semen exosomes inhibit HIV infection and HIV-induced proinflammatory cytokine production independent of the activation state of primary lymphocytes

Semen exosomes (SE) inhibit HIV infection. However, the effect of SE on cell activation and inflammation remains unknown. We characterized the response of peripheral blood mononuclear cells (PBMCs) from HIV-uninfected and antiretroviral therapy-suppressed HIV-infected (HIV+) subjects to SE. Quiescent PBMCs or T-cell receptor (TCR)-activated PBMCs from HIV- and HIV+ donors were stimulated with SE in the presence/absence of ex vivo HIV infection. In HIV-infected PBMCs, SE did not reactivate HIV, did not induce lymphoblast development, nor increase CD69+/CD25+ numbers. Furthermore, SE inhibited de novo HIV infection without altering cell activation. SE also asynchronously downregulated HIV-inducible IL1β, IL8, and TNFα and upregulated CXCL10. These data suggest that SE inhibits HIV infection and production of HIV-induced proinflammatory cytokines while preserving lymphocyte activation.

Lymphocyte homeostasis is maintained in perinatally HIV-infected patients after three decades of life

Background

While immunosenescence, defined as reduced production of new lymphocytes, restriction of T-cell receptor repertoire and telomeres shortening, has been extensively evaluated in HIV-infected children and adults, no data about these parameters are available in perinatally-infected patients with very long-lasting HIV infection.

Methods

We compared thymic and bone marrow output, telomere length (measured by Real-Time PCR) and T-cell receptor repertoire (determined by spectratyping) of 21 perinatally HIV-infected subjects (with a median of 27 years of infection) with those of 19 age-matched non-perinatally HIV-infected patients and 40 healthy controls. All patients received a combined antiretroviral therapy.

Results

While thymic and bone marrow output were not different among the analyzed groups, telomere length in peripheral blood cells and T-cell receptor diversity were significantly lower in HIV-perinatally and non-perinatally infected individuals compared to healthy controls.

Conclusions

In HIV-infected subjects, a normal thymic output together with a reduced telomere length and a restricted T-cell receptor repertoire could be explained by the shift of newly produced cells into memory subsets. This phenomenon may allow to control viral infection and maintain peripheral homeostasis.

IgG abnormalities in HIV-positive Malawian women initiating antiretroviral therapy during pregnancy persist after 24 months of treatment

OBJECTIVES

Hypergammaglobulinemia and anomalies in the IgG subclass distribution are common in HIV-infected individuals and persist even after many years of antiretroviral therapy (ART). The aim of this study was to investigate the IgG profile and dynamics in pregnant HIV-infected Malawian women in the Option B era.

METHODS

Thirty-seven treatment-naive women received ART from the third trimester of pregnancy to 6 months post delivery (end of the breastfeeding period). ART continuation (group C) or interruption (group I) was then decided on the basis of the CD4+ cell count at enrolment (>350 or ≤350/μl). Total IgG and IgG subclasses were determined in maternal serum using a nephelometric assay at baseline and at 6 and 24 months postpartum.

RESULTS

At enrolment, 36/37 women had IgG levels >15g/l and there was a predominance of the IgG1 isotype (more than 90%) in parallel with underrepresentation of IgG2 (5.0%). After 6 months of ART, both groups showed a significant median decrease in total IgG (-3.1g/l in group I, -3.5g/l in group C) and in IgG1 (-4.0g/l and -3.6g/l, respectively), but only a modest recovery in IgG2 levels (+0.16 in group I, +0.14g/l in group C). At month 24, hypergammaglobulinemia was still present in 73.7% of women in group C, although a significant reduction was observed in total IgG level and in IgG1 and IgG3 subclasses (p<0.0001 in all cases). IgG2 levels did not show any significant change. In group I at 24 months, total IgG and IgG subclasses had returned to levels comparable to those at baseline.

CONCLUSIONS

The beneficial effects of 24 months of ART appear to be limited in the B-cell compartment, with an incomplete reduction of total IgG levels and no recovery of IgG2 depletion. A short ART period did not have significant effects on IgG abnormalities in women who interrupted treatment.

Single Cell Profiling Reveals PTEN Overexpression in Influenza-Specific B cells in Aging HIV-infected individuals on Anti-retroviral Therapy

Memory B cells (MBC) respond to secondary antigen challenge to protect against infection and to boost immunity following vaccinations. Despite effective treatment, chronic HIV infection disturbs MBCs by reducing numbers and altering functionality due to hyper-activation and increased apoptosis leading to suboptimal antibody responses against common infectious agents. We used single cell gene expression analysis to evaluate antigen-specific memory B cells in peripheral blood of virally-suppressed HIV-infected individuals and healthy controls stratified by serum H1N1 antibody response 3 weeks post-administration of the seasonal trivalent inactivated influenza vaccine. We used a fluorescent probe to isolate influenza H1N1-specific B cells and a multiplexed and targeted RT-PCR approach to measure expression levels of 96 genes involved in B cell activation and function. Gene profiling revealed a 4-gene predictive signature containing the phosphoinositide-3 kinase (PI3K) inhibitor, PTEN, for identifying antigen-specific MBC from HIV-infected individuals compared to healthy controls. Gene co-expression analysis showed that in addition to overexpression of PTEN, there was increased co-expression of type I interferon-associated genes with PTEN on single cell level in HIV compared to controls. This study highlights the persistent defects in MBC from HIV-infected individuals and points to the PI3K signaling pathway as a target for potential immune intervention.

Effective B cell activation in vitro during viremic HIV-1 infection with surrogate T cell stimulation

Identifying HIV-1-associated B cell defects and responses to activation may direct interventions to circumvent their impaired antibody responses to infection and vaccines. Among 34 viremic HIV-1-infected and 20 seronegative control adults, we measured baseline frequencies and activation of B and T cell subsets, expression of activation-induced cytidine deaminase (AID), potential determinants of B cell activation in vivo and B and T cell responses in vitro. At baseline, HIV-1 infection was associated with increased IgM memory and decreased anergic cell frequencies, as well as increased activation in all 10 B cell subsets compared with controls. HIV-1 status, TFH activation, and BAFF were significant potential drivers of B cell activation. Despite high baseline activation among HIV-1-infected subjects, stimulation in vitro with combined surrogates for antigen (anti-IgM), cognate (CD40 ligand) and soluble T cell factors (IL-4) elicited comparable B cell activation, transitions from naïve to class-switched memory cells and AID expression in both groups. In summary, viremic HIV-1 infection perturbs circulating B cell subsets and activation at each stage of B cell maturation. However, that appropriate stimulation of B cells elicits effective activation and maturation provides impetus for advancing vaccine development to prevent secondary infections by circumventing early B cell defects.

Low Peripheral T Follicular Helper Cells in Perinatally HIV-Infected Children Correlate With Advancing HIV Disease

Background

T follicular helper (Tfh) cells are crucial for B cell differentiation and antigen-specific antibody production. Dysregulation of Tfh-mediated B cell help weakens B cell responses in HIV infection. Moreover, Tfh cells in the lymph node and peripheral blood comprise a significant portion of the latent HIV reservoir. There is limited data on the effects of perinatal HIV infection on Tfh cells in children. We examined peripheral Tfh (pTfh) cell frequencies and phenotype in HIV-infected children and their associations with disease progression, immune activation, and B cell differentiation.

Methods

In a Kenyan cohort of 76 perinatally HIV-infected children, comprised of 43 treatment-naïve (ART−) and 33 on antiretroviral therapy (ART+), and 42 healthy controls (HIV−), we identified memory pTfh cells, T cell activation markers, and B cell differentiation states using multi-parameter flow cytometry. Soluble CD163 and intestinal fatty acid-binding protein plasma levels were quantified by ELISA.

Results

ART− children had reduced levels of pTfh cells compared with HIV− children that increased with antiretroviral therapy. HIV+ children had higher programmed cell death protein 1 (PD-1) expression on pTfh cells, regardless of treatment status. Low memory pTfh cells with elevated PD-1 levels correlated with advancing HIV disease status, indicated by increasing HIV viral loads and T cell and monocyte activation, and decreasing %CD4 and CD4:CD8 ratios. Antiretroviral treatment, particularly when started at younger ages, restored pTfh cell frequency and eliminated correlations with disease progression, but failed to lower PD-1 levels on pTfh cells and their associations with CD4 T cell percentages and activation. Altered B cell subsets, with decreased naïve and resting memory B cells and increased activated and tissue-like memory B cells in HIV+ children, correlated with low memory pTfh cell frequencies. Last, HIV+ children had decreased proportions of CXCR5+ CD8 T cells that associated with low %CD4 and CD4:CD8 ratios.

Conclusion

Low memory pTfh cell frequencies with high PD-1 expression in HIV+ children correlate with worsening disease status and an activated and differentiated B cell profile. This perturbed memory pTfh cell population may contribute to weak vaccine and HIV-specific antibody responses in HIV+ children. Restoring Tfh cell capacity may be important for novel pediatric HIV cure and vaccine strategies.

Impact of HIV infection and highly active antiretroviral therapy (HAART) on B cell subpopulations in children

B-cells play an important role in defending children against various infections. In view of scare data, we undertook this prospective cohort study to describe B cell compartment in HIV infected children (<5 years of age) and the effect of HAART on B cell subpopulations. HIV infected children (<5 years) from Pediatric HIV services of the Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, were recruited (April 2012-December 2015). The enrolled HIV-1 infected children (n = 59) were followed up regularly for 12 months; healthy controls (n = 51) included HIV uninfected children with no major illness. Flow cytometry was performed on fresh EDTA-treated blood samples to characterize B cell subpopulations. In HIV-infected children, marked depletion of naive (P = 0.003), non-switched memory (P = 0.02), mature (P = 0.0005), resting memory (P < 0.0001) B cells, and expansion of double negative memory (P < 0.0001), activated memory (P < 0.0001) and tissue like memory (P < 0.0001) B cells were observed as compared to healthy controls. In children started on HAART, at the end of 12 months of therapy, frequencies of non-switched memory (P = 0.04), switched memory (P = 0.01), and resting memory (P = 0.003) B cells were lower; activated memory (P = 0.04), and tissue-like memory (P = 0.0001) B cells were still higher than healthy controls. HIV infection resulted in reduced memory B cells in HIV infected children. Following HAART, there was normalization of some B cell subpopulations. The study emphasizes the need of re-vaccination in HIV infected children to maintain the memory B cell pool and adequate humoral immune response against infections.

Memory B cell dysregulation in HIV-1-infected individuals

OBJECTIVE

To characterize the effect of the HIV-1 infection and antiretroviral treatment (ART) in the human memory B (MEB)-cell compartment.

DESIGN

A cross-sectional study was designed to analyze MEB cells of HIV-1 ART treated and ART-naive study participants, and uninfected individuals.

METHODS

Frequency and absolute counts of MEB cell subsets in blood were determined by multicolor flow cytometry. Spontaneous cell death and B-cell proliferative capacity was evaluated in vitro by cell culture and flow cytometry. Splenic function was determined by pitted erythrocytes quantification in HIV-1 ART-treated study participants.

RESULTS

HIV-1 ART-treated individuals did not show functional hyposplenism despite the lack of recovery IgMIgDCD27 marginal zone-like B cells. Moreover, two germinal center-dependent MEB cells subsets were also dysregulated in HIV-1 individuals: IgMIgDCD27 (IgM only) cells were increased, whereas the switched subset (IgMIgD) was reduced in viremic individuals. Althought ART restored the numbers of these populations; the switched MEB cells were enriched in CD27 cells, which showed the highest susceptibility to spontaneous cell death ex vivo. In addition, B cells from viremic individuals showed a poor response to B-cell receptor and toll-like receptor 9 stimulation that was circumvented when both stimuli were used simultaneously.

CONCLUSION

B cells from HIV-1 study participants show a poor stimulation capacity, that may be bypassed by the proper combination of stimuli, and a dysregulated MEB cell pool that suggest an affectation of the germinal center reaction, only partially normalized by ART. Interestingly, hyposplenism does not explain the lack of recovery of the marginal zone-like B cells in ART-treated HIV-1 individuals.

Increased activated memory B-cells in the peripheral blood of patients with erythema nodosum leprosum reactions

B-cells, in addition to antibody secretion, have emerged increasingly as effector and immunoregulatory cells in several chronic inflammatory diseases. Although Erythema Nodosum Leprosum (ENL) is an inflammatory complication of leprosy, the role of B- cell subsets has never been studied in this patient group. Therefore, it would be interesting to examine the contribution of B-cells in the pathogenesis of ENL. A case-control study design was used to recruit 30 untreated patients with ENL and 30 non-reactional lepromatous leprosy (LL) patient controls at ALERT Hospital, Ethiopia. Peripheral blood samples were obtained before, during and after treatment from each patient. Peripheral blood mononuclear cells (PBMCs) were isolated and used for immunophenotyping of B- cell subsets by flow cytometry. The kinetics of B-cells in patients with ENL before, during and after Prednisolone treatment of ENL was compared with LL patient controls as well as within ENL group. Total B-cells, mature B-cells and resting memory B-cells were not significantly different between patients with ENL reactions and LL controls before treatment. Interestingly, while the percentage of naive B-cells was significantly lower in untreated ENL patients than in LL patient controls, the percentage of activated memory B-cells was significantly higher in these untreated ENL patients than in LL controls. On the other hand, the percentage of tissue-like memory B-cells was considerably low in untreated ENL patients compared to LL controls. It appears that the lower frequency of tissue-like memory B-cells in untreated ENL could promote the B-cell/T-cell interaction in these patients through downregulation of inhibitory molecules unlike in LL patients. Conversely, the increased production of activated memory B-cells in ENL patients could imply the scale up of immune activation through antigen presentation to T-cells. However, the generation and differential function of these memory B-cells need further investigation. The finding of increased percentage of activated memory B-cells in untreated patients with ENL reactions suggests the association of these cells with the ENL pathology. The mechanism by which inflammatory reactions like ENL affecting these memory cells and contributing to the disease pathology is an interesting area to be explored for and could lead to the development of novel and highly efficacious drug for ENL treatment.

Alterations in B Cell Compartment Correlate with Poor Neutralization Response and Disease Progression in HIV-1 Infected Children

Several B cell defects are reported in HIV-1 infected individuals including variation in B cell subsets, polyclonal B cell activation and exhaustion, with broadly neutralizing antibodies elicited in less than 10–20% of the infected population. HIV-1 disease progression is faster in children than adults. B Lymphocyte Stimulator (BLyS), expressed on dendritic cells (DCs), is a key regulator of B cell homeostasis. Understanding how DCs influence B cell phenotype and functionality (viral neutralization), thereby HIV-1 disease outcome in infected children, is important to develop interventional strategies for restoration of B cell function. In this study, a total of 38 vertically transmitted HIV-1 infected antiretroviral therapy (ART) naïve children and 25 seronegative controls were recruited. Based on the CD4 counts and years post-infection, infected children were categorized as long-term non-progressors (LTNPs) (n = 20) and progressors (n = 18). Eight of these progressors were followed up at 6–12 months post-ART. Percentages (%) of DCs, B cell subsets, and expression of BLyS on DCs were analyzed by flow-cytometry. Plasma levels of B cell growth factors were measured by ELISA and viral neutralization activity was determined using TZM-bl assay. Lower (%) of myeloid DCs (mDCs), plasmacytoid DCs, and high expression of BLyS on mDCs were observed in HIV-1 infected progressors than seronegative controls. Progressors showed lower % of naive B cells, resting memory B cells and higher % of mature activated, tissue-like memory B cells as compared to seronegative controls. Higher plasma levels of IL-4, IL-6, IL-10, and IgA were observed in progressors vs. seronegative controls. Plasma levels of IgG were high in progressors and in LTNPs than seronegative controls, suggesting persistence of hypergammaglobulinemia at all stages of disease. High plasma levels of BLyS in progressors positively correlated with poor viral neutralizing activity. Interestingly on follow up, treatment naïve progressors, post-ART showed increase in resting memory B cells along with reduction in plasma BLyS levels that correlated with improvement in viral neutralization. This is the first study to demonstrate that reduction in plasma BLyS levels correlates with restoration of B cell function, in terms of viral neutralization in HIV-1-infected children.

T Follicular Helper Cells and B Cell Dysfunction in Aging and HIV-1 Infection

T follicular helper (Tfh) cells are a subset of CD4 T cells that provide critical signals to antigen-primed B cells in germinal centers to undergo proliferation, isotype switching, and somatic hypermutation to generate long-lived plasma cells and memory B cells during an immune response. The quantity and quality of Tfh cells therefore must be tightly controlled to prevent immune dysfunction in the form of autoimmunity and, on the other hand, immune deficiency. Both Tfh and B cell perturbations appear during HIV infection resulting in impaired antibody responses to vaccines such as seasonal trivalent influenza vaccine, also seen in biologic aging. Although many of the HIV-associated defects improve with antiretroviral therapy (ART), excess immune activation and antigen-specific B and T cell responses including Tfh function are still impaired in virologically controlled HIV-infected persons on ART. Interestingly, HIV infected individuals experience increased risk of age-associated pathologies. This review will discuss Tfh and B cell dysfunction in HIV infection and highlight the impact of chronic HIV infection and aging on Tfh-B cell interactions.

FcRL4 Expression Identifies a Pro-inflammatory B Cell Subset in Viremic HIV-Infected Subjects

In autoimmune diseases, toll-like receptor (TLR)-stimulated pro-inflammatory IL-6-secreting B cells exert pathogenic roles. Similarly, B cell Fc receptor-like 4 (FcRL4) expression amplifies TLR stimulation, and in rheumatoid arthritis patients, FcRL4 expression identifies a pro-inflammatory B cell subset. B cells from HIV-infected subjects also express heightened levels of FcRL4 and secrete high levels of IL-6: a critical mediator of HIV disease progression. In this study, we sought to determine if FcRL4 identifies a pro-inflammatory B cell subset in HIV-infected subjects and further elucidate the mechanisms underlying FcRL4 amplification of TLR stimulation. We determine that tissue-like memory B cells express the highest endogenous levels of FcRL4 positively correlating with IL-6 expression (p = 0.0022, r = 0.8667), but activated memory B cells exhibit the highest frequency of FcRL4^hiIL-6^hi cells. FcRL4^hi B cells exhibit an activated TLR-signaling pathway identified by elevated phosphorylation levels of: pERK (p = 0.0373), p38 (p = 0.0337), p65 (p = 0.1097), and cJUN (p = 0.0239), concomitant with significantly elevated expression of the TLR-signaling modulator hematopoietic cell kinase (HcK, p = 0.0414). Compared to FcRL4^neg B cells from healthy controls, TLR9-stimulated FcRL4^pos B cells express significantly higher levels of lL-6 (p = 0.0179). Further, TLR9-stimulated B cells also upregulate the expression of FcRL4 (p = 0.0415) and HcK (p = 0.0386). In B-cell lines, siRNA-mediated HcK knockdown downmodulates TLR9-induced FcRL4-mediated activation quantified by CD23 upregulation (p = 0.0553). We present data suggesting that, in viremic HIV-infected individuals, FcRL4 expression identifies unique IL-6 producing pro-inflammatory B-cell subsets. Further, TLR stimulation likely modulates FcRL4 expression and FcRL4 expression is associated with Hck, potentially enhancing the activation of TLR-signaling associated transcription factors. Pathogenic B-cells have been identified in other disease settings, and this study represents a novel report describing a pro-inflammatory B cell subset in HIV-infected patients.

Atypical memory B cells in human chronic infectious diseases: An interim report

Immunological memory is a remarkable phenomenon in which survival of an initial infection by a pathogen leads to life-long protection from disease upon subsequent exposure to that same pathogen. For many infectious diseases, long-lived protective humoral immunity is induced after only a single infection in a process that depends on the generation of memory B cells (MBCs) and long-lived plasma cells. However, over the past decade it has become increasingly evident that many chronic human infectious diseases to which immunity is not readily established, including HIV-AIDS, malaria and TB, are associated with fundamental alterations in the composition and functionality of MBC compartments. A common feature of these diseases appears to be a large expansion of what have been termed exhausted B cells, tissue-like memory B cells or atypical memory B cells (aMBCs) that, for simplicity's sake, we refer to here as aMBCs. It has been suggested that chronic immune activation and inflammation drive the expansion of aMBCs and that in some way aMBCs contribute to deficiencies in the acquisition of immunity in chronic infectious diseases. Although aMBCs are heterogeneous both within individuals and between diseases, they have several features in common including low expression of the cell surface markers that define classical MBCs in humans including CD21 and CD27 and high expression of genes not usually expressed by classical MBCs including T-bet, CD11c and a variety of inhibitory receptors, notably members of the FcRL family. Another distinguishing feature is their greatly diminished ability to be stimulated through their B cell receptors to proliferate, secrete cytokines or produce antibodies. In this review, we describe our current understanding of the phenotypic markers of aMBCs, their specificity in relation to the disease-causing pathogen, their functionality, the drivers of their expansion in chronic infections and their life span. We briefly summarize the features of aMBCs in healthy individuals and in autoimmune disease. We also comment on the possible relationship of human aMBCs and T-bet⁺, CD11c⁺ age/autoimmune-associated B cells, also a topic of this review volume.

Paradoxical aging in HIV: immune senescence of B Cells is most prominent in young age

Combination antiretroviral therapies (cART)can lead to normal life expectancy in HIV-infected persons, and people aged >50 yrs represent the fastest growing HIV group. Although HIV and aging are independently associated with impaired humoral immunity, immune status in people aging with HIV is relatively unexplored. In this study influenza vaccination was used to probe age associated perturbations in the B cell compartment of HIV-negative "healthy controls" (HC) and virologically controlled HIV-infected participants on cART (HIV) (n=124), grouped by age as young (<40 yrs), middle-aged (40-59yrs) or old (>60 yrs). H1N1 antibody response at d21 post-vaccination correlated inversely with age in both HC and HIV. Immunophenotyping of cryopreserved PBMC demonstrated increased frequencies of double negative B cells and decreased plasmablasts in old compared to young HC. Remarkably, young HIV were different from young HC but similar to old HC in B cell phenotype, influenza specific spontaneous (d7) or memory (d21) antibody secreting cells. We conclude that B cell immune senescence is a prominent phenomenon in young HIV in comparison to young HC, but distinctions between old HIV and old HC are less evident though both groups manifest age-associated B cell dysfunction.

Effect of Antiretroviral Therapy on the Memory and Activation Profiles of B Cells in HIV-Infected African Women

Human immunodeficiency virus infection induces a wide range of effects in B cells, including skewed memory cell differentiation, compromised B cell function, and hypergammaglobulinemia. However, data on the extent to which these B cell abnormalities can be reversed by antiretroviral therapy (ART) are limited. To investigate the effect of ART on B cells, the activation (CD86) and differentiation (IgD, CD27, and CD38) profiles of B cells were measured longitudinally in 19 HIV-infected individuals before (median, 2 mo) and after ART initiation (median, 12 mo) and compared with 19 age-matched HIV-uninfected individuals using flow cytometry. Twelve months of ART restored the typical distribution of B cell subsets, increasing the proportion of naive B cells (CD27^-IgD⁺CD38^-) and concomitantly decreasing the immature transitional (CD27^-IgD⁺CD38⁺), unswitched memory (CD27⁺IgD⁺CD38^-), switched memory (CD27⁺IgD^-CD38^- or CD27^-IgD^-CD38^-), and plasmablast (CD27⁺IgD^-CD38^high) subsets. However, B cell activation was only partially normalized post-ART, with the frequency of activated B cells (CD86⁺CD40⁺) reduced compared with pre-ART levels (p = 0.0001), but remaining significantly higher compared with HIV-uninfected individuals (p = 0.0001). Interestingly, unlike for T cell activation profiles, the extent of B cell activation prior to ART did not correlate with HIV plasma viral load, but positively associated with plasma sCD14 levels (p = 0.01, r = 0.58). Overall, ART partially normalizes the skewed B cell profiles induced by HIV, with some activation persisting. Understanding the effects of HIV on B cell dysfunction and restoration following ART may provide important insights into the mechanisms of HIV pathogenesis.

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

B-cells not only produce immunoglobulins and present antigens to T-cells, but also additional key roles in the immune system. Current knowledge on the role of B-cells in infections caused by intracellular bacteria is fragmentary and contradictory. We therefore analysed the phenotypical and functional properties of B-cells during infection and disease caused by Mycobacterium tuberculosis (Mtb), the bacillus causing tuberculosis (TB), and included individuals with latent TB infection (LTBI), active TB, individuals treated successfully for TB, and healthy controls. Patients with active or treated TB disease had an increased proportion of antibodies reactive with mycobacteria. Patients with active TB had reduced circulating B-cell frequencies, whereas only minor increases in B-cells were detected in the lungs of individuals deceased from TB. Both active TB patients and individuals with LTBI had increased relative fractions of B-cells with an atypical phenotype. Importantly, these B-cells displayed impaired proliferation, immunoglobulin- and cytokine- production. These defects disappeared upon successful treatment. Moreover, T-cell activity was strongest in individuals successfully treated for TB, compared to active TB patients and LTBI subjects, and was dependent on the presence of functionally competent B-cells as shown by cellular depletion experiments. Thus, our results reveal that general B-cell function is impaired during active TB and LTBI, and that this B-cell dysfunction compromises cellular host immunity during Mtb infection. These new insights may provide novel strategies for correcting Mtb infection-induced immune dysfunction towards restored protective immunity.

In infections with intracellular pathogens like Mycobacterium tuberculosis (Mtb), B-cells have long been ignored as their primary product, immunoglobulins, are unlikely to recognize intracellular bacteria. However, we have analysed here the frequency, phenotype and function of B-cells in tuberculosis (TB) infection and disease. Our data revealed that during active TB disease B-cell numbers are decreased and remaining B-cells are functionally impaired. Surprisingly, also individuals recently infected with Mtb suffered from poorly functional B-cells, but patients cured from the disease recovered with normal B-cell numbers and function. Thus, B-cell dysfunction contributes to impaired immune activation during Mtb infection.

Beneficial Effects of cART Initiated during Primary and Chronic HIV-1 Infection on Immunoglobulin-Expression of Memory B-Cell Subsets

Introduction

During HIV-1 infection the B-cell compartment undergoes profound changes towards terminal differentiation, which are only partially restored by antiretroviral therapy (cART).

Materials and Methods

To investigate the impact of infection as early as during primary HIV-1 infection (PHI) we assessed distribution of B-cell subsets in 19 PHI and 25 chronic HIV-1-infected (CHI) individuals before and during 48 weeks of cART as compared to healthy controls (n = 23). We also analysed Immunoglobulin-expression of memory B-cell subsets to identify alterations in Immunoglobulin-maturation.

Results

Determination of B-cell subsets at baseline showed that total and Naive B-cells were decreased whereas Activated Memory (AM), Tissue-like Memory (TLM) B-cells and Plasma cells were increased in both PHI and CHI patients. After 4 weeks of cART total B-cells increased, while AM, TLM B-cells and Plasma cells decreased, although without reaching normal levels in either group of individuals. This trend was maintained until week 48, though only total B-cells normalized in both PHI and CHI. Resting Memory (RM) B-cells were preserved since baseline. This subset remained stable in CHI, while was expanded by an early initiation of cART during PHI. Untreated CHI patients showed IgM-overexpression at the expenses of switched (IgM-IgD-) phenotypes of the memory subsets. Interestingly, in PHI patients a significant alteration of Immunoglobulin-expression was evident at BL in TLM cells, and after 4 weeks, despite treatment, in AM and RM subsets. After 48 weeks of therapy, Immunoglobulin-expression of AM and RM almost normalized, but remained perturbed in TLM cells in both groups.

Conclusions

In conclusion, aberrant activated and exhausted B-cell phenotypes rose already during PHI, while most of the alterations in Ig-expression seen in CHI appeared later, despite 4 weeks of effective cART. After 48 weeks of cART B-cell subsets distribution improved although without full normalization, while Immunoglobulin-expression normalized among AM and RM, remaining perturbed in TLM B-cells of PHI and CHI.

Impaired Phenotype and Function of T Follicular Helper Cells in HIV-1-Infected Children Receiving ART

T follicular helper (Tfh) cells are important components in development of specific humoral immune responses; whether the number and biology of Tfh cells is impaired in HIV-1-infected children is not yet studied.The frequency, phenotype, and function of Tfh cells and B cells were determined in blood of HIV-1-infected children receiving antiretroviral therapy (ART) and age-matched controls. Flow cytometry was used to characterize the frequency of Tfh cells and B cell subsets. Cytokine expression was measured after in vitro activation of Tfh cells.A reduced frequency of memory Tfh cells (P < 0.001) was identified in HIV-1-infected children and, on these cells, a reduced expression of programmed death-1 (PD-1) and inducible T cell costimulator (ICOS) (P < 0.001 and P < 0.01). Upon activation, the capacity of Tfh cells to express IL-4, an important cytokine for B cell function, was impaired in HIV-1-infected children.B cell subpopulations in HIV-1-infected children displayed significant differences from the control group: the frequency of resting memory (RM) B cells was reduced (P < 0.01) whereas the frequency of exhausted memory B cells increased (P < 0.001). Interestingly, the decline of RM cells correlated with the reduction of memory Tfh cells (P = 0.02).Our study shows that function and phenotype of Tfh cells, pivotal cells for establishment of adaptive B cell responses, are impaired during HIV-1 infection in children. A consistent reduction of memory Tfh cells is associated with declined frequencies of RM B cells, creating a novel link between dysfunctional features of these cell types, major players in establishment of humoral immunity.

HIV-associated memory B cell perturbations

Memory B-cell depletion, hyperimmunoglobulinemia, and impaired vaccine responses are the hallmark of B cell perturbations inhuman immunodeficiency virus (HIV) disease. Although B cells are not the targets for HIV infection, there is evidence for B cell, especially memory B cell dysfunction in HIV disease mediated by other cells or HIV itself. This review will focus on HIV-associated phenotypic and functional alterations in memory B cells. Additionally, we will discuss the mechanism underlying these perturbations and the effect of anti-retroviral therapy (ART) on these perturbations.