Innate immune defects correlate with failure of antibody responses to H1N1/09 vaccine in HIV-infected patients

Chronic inflammation degrades CD4 T cell immunity to prior vaccines in treated HIV infection

To date, our understanding of how HIV infection impacts vaccine-induced cellular immunity is limited. Here, we investigate inflammation, immune activation and antigen-specific T cell responses in HIV-uninfected and antiretroviral-treated HIV-infected people. Our findings highlight lower recall responses of antigen-specific CD4 T cells that correlate with high plasma cytokines levels, T cell hyperactivation and an altered composition of the T subsets enriched with more differentiated cells in the HIV-infected group. Transcriptomic analysis reveals that antigen-specific CD4 T cells of the HIV-infected group have a reduced expression of gene sets previously reported to correlate with vaccine-induced pathogen-specific protective immunity and further identifies a consistent impairment of the IFNα and IFNγ response pathways as mechanism for the functional loss of recall CD4 T cell responses in antiretroviral-treated people. Lastly, in vitro treatment with drugs that reduce inflammation results in higher memory CD4 T cell IFNγ responses. Together, our findings suggest that vaccine-induced cellular immunity may benefit from strategies to counteract inflammation in HIV infection.

Immunological and Clinical Responses to Vaccinations among Adults Living with HIV

People living with human immunodeficiency virus (HIV) are at higher risk of morbidity and mortality due to vaccine-preventable diseases. At the same time, they are less likely to respond to vaccinations, and might have a higher rate of vaccine adverse event and faster waning of protective effect. International and national guidelines emphasize the importance of vaccinating people living with HIV against respiratory system disease pathogens including seasonal influenza, Streptococcus pneumoniae, and COVID-19, as well as against sexually transmitted infections, i.e., Hepatitis A and B (HAV, HBV) and human papillomavirus (HPV). This narrative review aims to provide a comprehensive examination of the current knowledge regarding the immune and clinical responses elicited by vaccinations in the older adult population living with HIV.

Immunogenicity and Efficacy of Vaccination in People Living with Human Immunodeficiency Virus

People living with HIV (PLWH) remain at high risk of mortality and morbidity from vaccine-preventable diseases, even though antiretroviral therapy (ART) has restored life expectancy and general well-being. When, which, and how many doses of vaccine should be administered over the lifetime of PLWH are questions that have become clinically relevant. Immune responses to most vaccines are known to be impaired in PLWH. Effective control of viremia with ART and restored CD4+ T-cell count are correlated with an improvement in responsiveness to routine vaccines. However, the presence of immune alterations, comorbidities and co-infections may alter it. In this article, we provide a comprehensive review of the literature on immune responses to different vaccines in the setting of HIV infection, emphasizing the potential effect of HIV-related factors and presence of comorbidities in modulating such responses. A better understanding of these issues will help guide vaccination and prevention strategies for PLWH.

In Vitro Exposure of Primary Human T Cells and Monocytes to Polyclonal Stimuli Reveals a Basal Susceptibility to Display an Impaired Cellular Immune Response and Develop Severe COVID-19

The contribution of the cellular immune response to the severity of coronavirus disease 2019 (COVID-19) is still uncertain because most evidence comes from patients receiving multiple drugs able to change immune function. Herein, we conducted a prospective cohort study and obtained blood samples from 128 unvaccinated healthy volunteers to examine the in vitro response pattern of CD4+ and CD8+ T cells and monocyte subsets to polyclonal stimuli, including anti-CD3, anti-CD28, poly I:C, severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) recombinant spike S1 protein, and lipopolysaccharide. Then, we started a six-month follow-up and registered 12 participants who got SARS-CoV-2 infection, from whom we retrospectively analyzed the basal immune response pattern of T cells and monocytes. Of the 12 participants infected, six participants developed mild COVID-19 with self-limiting symptoms such as fever, headache, and anosmia. Conversely, six other participants developed severe COVID-19 with pneumonia, respiratory distress, and hypoxia. Two severe COVID-19 cases required invasive mechanical ventilation. There were no differences between mild and severe cases for demographic, clinical, and biochemical baseline characteristics. In response to polyclonal stimuli, basal production of interleukin-2 (IL-2) and interferon (IFN-) gamma significantly decreased, and the programmed cell death protein 1 (PD-1) increased in CD4+ and CD8+ T cells from participants who posteriorly developed severe COVID-19 compared to mild cases. Likewise, CD14++CD16- classical and CD14+CD16+ non-classical monocytes lost their ability to produce IFN-alpha in response to polyclonal stimuli in participants who developed severe COVID-19 compared to mild cases. Of note, neither the total immunoglobulin G serum titers against the virus nor their neutralizing ability differed between mild and severe cases after a month of clinical recovery. In conclusion, using in vitro polyclonal stimuli, we found a basal immune response pattern associated with a predisposition to developing severe COVID-19, where high PD-1 expression and low IL-2 and IFN-gamma production in CD4+ and CD8+ T cells, and poor IFN-alpha expression in classical and non-classical monocytes are linked to disease worsening. Since antibody titers did not differ between mild and severe cases, these findings suggest cellular immunity may play a more crucial role than humoral immunity in preventing COVID-19 progression.

B-Cell Immunophenotyping to Predict Vaccination Outcome in the Immunocompromised - A Systematic Review

Vaccination is the most effective measure to prevent infections in the general population. Its efficiency strongly depends on the function and composition of the immune system. If the immune system lacks critical components, patients will not be fully protected despite a completed vaccination schedule. Antigen-specific serum immunoglobulin levels are broadly used correlates of protection. These are the products of terminally differentiated B cells - plasma cells. Here we reviewed the literature on how aberrancies in B-cell composition and function influence immune responses to vaccinations. In a search through five major literature databases, 6,537 unique articles published from 2000 and onwards were identified. 75 articles were included along three major research lines: extremities of life, immunodeficiency and immunosuppression. Details of the protocol can be found in the International Prospective Register of Systematic Reviews [PROSPERO (registration number CRD42021226683)]. The majority of articles investigated immune responses in adults, in which vaccinations against pneumococci and influenza were strongly represented. Lack of baseline information was the most common reason of exclusion. Irrespective of study group, three parameters measured at baseline seemed to have a predictive value in assessing vaccine efficacy: (1) distribution of B-cell subsets (mostly a reduction in memory B cells), (2) presence of exhausted/activated B cells, or B cells with an aberrant phenotype, and (3) pre-existing immunological memory. In this review we showed how pre-immunization (baseline) knowledge of circulating B cells can be used to predict vaccination efficacy. We hope that this overview will contribute to optimizing vaccination strategies, especially in immunocompromised patients.

A delayed fractionated dose RTS,S AS01 vaccine regimen mediates protection via improved T follicular helper and B cell responses

Malaria-071, a controlled human malaria infection trial, demonstrated that administration of three doses of RTS,S/AS01 malaria vaccine given at one-month intervals was inferior to a delayed fractional dose (DFD) schedule (62.5% vs 86.7% protection, respectively). To investigate the underlying immunologic mechanism, we analyzed the B and T peripheral follicular helper cell (pTfh) responses. Here, we show that protection in both study arms was associated with early induction of functional IL-21-secreting circumsporozoite (CSP)-specific pTfh cells, together with induction of CSP-specific memory B cell responses after the second dose that persisted after the third dose. Data integration of key immunologic measures identified a subset of non-protected individuals in the standard (STD) vaccine arm who lost prior protective B cell responses after receiving the third vaccine dose. We conclude that the DFD regimen favors persistence of functional B cells after the third dose.

Decreased ratio of influenza-specific IgG versus IgM in response to influenza vaccination in antiretroviral-treated HIV-infected African Americans compared to Caucasians, and its direct correlation with the percentages of peripheral Tfh cells

BACKGROUND

Racial differences have been observed in the rate of bacterial infection and disease progression in HIV. Here, we evaluate racial differences in seasonal influenza vaccine responses.

METHODS

16 healthy controls (9 Caucasians (CC) and 7 African Americans (AA)) and 26 antiretroviral therapy (ART)-treated aviremic HIV+ subjects (11 CC and 15 AA) were enrolled in the current study. Blood was collected at pre-vaccination (D0) and day 14 (D14) following seasonal influenza vaccination. Serologic responses were characterized in plasma by ELISA. B and T cells were assessed by flow cytometry ex vivo.

RESULTS

The absolute counts of CD4+ CD3+ T cells and CD19+ B cells were similar in healthy controls and HIV-infected individuals, and similar in CC and AA in the two study groups. However, the percentage of peripheral T follicular helper (pTfh) cells was decreased in HIV+ AA compared to HIV+ CC. There were no racial differences in IgG antibody responses against vaccination in the two study groups. However, the ratio of anti-influenza-specific IgG versus IgM induction following vaccination was decreased in HIV+ AA compared to HIV+ CC, which was directly correlated with the percentages of pTfh cells. This racial difference and correlation were not demonstrable in healthy controls.

CONCLUSION

Here we report that HIV + AA has decreased fold induction of IgG versus IgM after influenza vaccination, which may suggest impaired class-switching from IgM to IgG in AA HIV-infected individuals.

Adjuvanted-influenza vaccination in patients infected with HIV: a systematic review and meta-analysis of immunogenicity and safety

Adjuvanted-influenza vaccination is an efficient method for enhancing the immunogenicity of influenza split-virus vaccines for preventing influenza. However, the medical community's understanding of its performance in patients infected with HIV remains limited. To identify the advantages, we conducted a systematic review and meta-analysis with randomized controlled trials (RCTs) and cohort and case-control studies that have the immunogenicity and safety of influenza vaccines in patients infected with HIV as outcomes. We searched six different databases, and 1698 patients infected with HIV in 11 studies were included. Statistical analysis was performed to calculate the pooled standardized mean differences (SMD) or relative risk (RR) and 95% confidence interval (CI). Regarding immunogenicity, the pooled SMD of GMT (Geometric mean titer) for A/H1N1 was 0.61 (95%CI (0.40,0.82)), the pooled RR of seroconversion was 1.34 (95%CI (0.91,1.98)) for the H1N1 vaccine, 1.27(95%CI (0.64,2.52)) for the H3N2 vaccine, 1.19(95%CI (0.97,1.46)) for the B-type influenza vaccine. The pooled RR of seroprotection was 1.61 (95%CI (1.00,2.58)) for the H1N1 vaccine, 1.06 (95%CI(0.83,1.35)) for the H3N2 vaccine, and 1.13(95%CI(0.91,1.41)) for the B-type vaccine. Adjuvanted-influenza vaccination showed good general tolerability in patients infected with HIV, with the only significant increase being the rate of local pain at the injection site (RR = 2.03, 95%CI (1.06,3.86)). In conclusion, all studies evaluating injected adjuvanted influenza vaccination among patients infected with HIV showed acceptable levels of safety and immunogenicity.

Circulating inflammatory monocytes contribute to impaired influenza vaccine responses in HIV-infected participants

OBJECTIVE

Antibody responses are often impaired in old age and in HIV-positive (HIV+) infection despite virologic control with antiretroviral therapy but innate immunologic determinants are not well understood.

DESIGN

Monocytes and natural killer cells were examined for relationships to age, HIV infection and influenza vaccine responses.

METHODS

Virologically suppressed HIV+ (n = 139) and HIV-negative (HIV-) (n = 137) participants classified by age as young (18-39 years), middle-aged (40-59 years) and old (≥60 years) were evaluated preinfluenza and postinfluenza vaccination.

RESULTS

Prevaccination frequencies of inflammatory monocytes were highest in old HIV+ and HIV-, with old HIV+ exhibiting higher frequency of integrin CD11b on inflammatory monocytes that was correlated with age, expression of C-C chemokine receptor-2 (CCR2) and plasma soluble tumor necrosis factor receptor-1 (sTNFR1), with inverse correlation with postvaccination influenza H1N1 antibody titers. Higher frequencies of CD11b+ inflammatory monocytes (CD11b(hi), >48.4%) compared with low frequencies of CD11b+ inflammatory monocytes (<15.8%) was associated with higher prevaccination frequencies of total and inflammatory monocytes and higher CCR2 MFI, higher plasma sTNFR1 and CXCL-10 with higher lipopolysaccharide stimulated expression of TNFα and IL-6, concomitant with lower postvaccination influenza antibody titers. In HIV+ CD11b(hi) expressers, the depletion of inflammatory monocytes from peripheral blood mononuclear cells resulted in enhanced antigen-specific CD4+ T-cell proliferation. Immature CD56(hi) natural killer cells were lower in young HIV+ compared with young HIV- participants.

CONCLUSION

Perturbations of innate immunity and inflammation signified by high CD11b on inflammatory monocytes are exacerbated with aging in HIV+ and negatively impact immune function involved in Ab response to influenza vaccination.

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.

The Role of BAFF System Molecules in Host Response to Pathogens

The two ligands B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) and the three receptors BAFF receptor (BAFF-R), transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI), and B cell maturation antigen (BCMA) are members of the "BAFF system molecules." BAFF system molecules are primarily involved in B cell homeostasis. The relevance of BAFF system molecules in host responses to microbial assaults has been investigated in clinical studies and in mice deficient for each of these molecules. Many microbial products modulate the expression of these molecules. Data from clinical studies suggest a correlation between increased expression levels of BAFF system molecules and elevated B cell responses. Depending on the pathogen, heightened B cell responses may strengthen the host response or promote susceptibility. Whereas pathogen-mediated increases in the expression levels of the ligands and/or the receptors appear to promote microbial clearance, certain pathogens have evolved to ablate B cell responses by suppressing the expression of TACI and/or BAFF-R on B cells. Other than its well-established role in B cell responses, the TACI-mediated activation of macrophages is also implicated in resistance to intracellular pathogens. An improved understanding of the role that BAFF system molecules play in infection may assist in devising novel strategies for vaccine development.

Perturbation of B Cell Gene Expression Persists in HIV-Infected Children Despite Effective Antiretroviral Therapy and Predicts H1N1 Response

Despite effective antiretroviral therapy (ART), HIV-infected individuals with apparently similar clinical and immunological characteristics can vary in responsiveness to vaccinations. However, molecular mechanisms responsible for such impairment, as well as biomarkers able to predict vaccine responsiveness in HIV-infected children, remain unknown. Following the hypothesis that a B cell qualitative impairment persists in HIV-infected children (HIV) despite effective ART and phenotypic B cell immune reconstitution, the aim of the current study was to investigate B cell gene expression of HIV compared to age-matched healthy controls (HCs) and to determine whether distinct gene expression patterns could predict the ability to respond to influenza vaccine. To do so, we analyzed prevaccination transcriptional levels of a 96-gene panel in equal numbers of sort-purified B cell subsets (SPBS) isolated from peripheral blood mononuclear cells using multiplexed RT-PCR. Immune responses to H1N1 antigen were determined by hemaglutination inhibition and memory B cell ELISpot assays following trivalent-inactivated influenza vaccination (TIV) for all study participants. Although there were no differences in terms of cell frequencies of SPBS between HIV and HC, the groups were distinguishable based upon gene expression analyses. Indeed, a 28-gene signature, characterized by higher expression of genes involved in the inflammatory response and immune activation was observed in activated memory B cells (CD27⁺CD21⁻) from HIV when compared to HC despite long-term viral control (>24 months). Further analysis, taking into account H1N1 responses after TIV in HIV participants, revealed that a 25-gene signature in resting memory (RM) B cells (CD27⁺CD21⁺) was able to distinguish vaccine responders from non-responders (NR). In fact, prevaccination RM B cells of responders showed a higher expression of gene sets involved in B cell adaptive immune responses (APRIL, BTK, BLIMP1) and BCR signaling (MTOR, FYN, CD86) when compared to NR. Overall, these data suggest that a perturbation at a transcriptional level in the B cell compartment persists despite stable virus control achieved through ART in HIV-infected children. Additionally, the present study demonstrates the potential utility of transcriptional evaluation of RM B cells before vaccination for identifying predictive correlates of vaccine responses in this population.

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.

Induction of IL21 in Peripheral T Follicular Helper Cells Is an Indicator of Influenza Vaccine Response in a Previously Vaccinated HIV-Infected Pediatric Cohort

HIV-infected patients of all ages frequently underperform in response to seasonal influenza vaccination, despite virologic control of HIV. The molecular mechanisms governing this impairment, as well as predictive biomarkers for responsiveness, remain unknown. This study was performed in samples obtained prevaccination (T0) from HIV-infected children who received the 2012-2013 seasonal influenza vaccine. Response status was determined based on established criterion for hemagglutination inhibition titer; participants with a hemagglutination titer ≥1:40 plus a ≥4-fold increase over T0 at 3 wk postvaccination were designated as responders. All children had a history of prior influenza vaccinations. At T0, the frequencies of CD4 T cell subsets, including peripheral T follicular helper (pTfh) cells, which provide help to B cells for developing into Ab-secreting cells, were similar between responders and nonresponders. However, in response to in vitro stimulation with influenza A/California/7/2009 (H1N1) Ag, differential gene expression related to pTfh cell function was observed by Fluidigm high-density RT-PCR between responders and nonresponders. In responders, H1N1 stimulation at T0 also resulted in CXCR5 induction (mRNA and protein) in CD4 T cells and IL21 gene induction in pTfh cells that were strongly associated with H1N1-specific B cell responses postvaccination. In contrast, CD4 T cells of nonresponders exhibited increased expression of IL2 and STAT5 genes, which are known to antagonize peripheral Tfh cell function. These results suggest that the quality of pTfh cells at the time of immunization is important for influenza vaccine responses and provide a rationale for targeted, ex vivo Ag-driven molecular profiling of purified immune cells to detect predictive biomarkers of the vaccine response.

Inflammatory Markers and Immune Response to Pneumococcal Vaccination in HIV-Positive and -Negative Adults

Background

Members of the Tumor Necrosis Factor (TNF)-superfamily have speculated roles in the response against T-independent type II antigens (TI-II) including pneumococcal polysaccharides (PPS). Dysregulation in their expression is associated with an enhanced risk for pneumococcal disease in neonates but their expression in other high-risk populations including HIV-positive individuals remains to be elucidated.

Objective

To investigate signals that contribute towards PPS-response and identify potential anomalies that may account for diminished serological response in HIV-positive individuals post Pneumovax (PPV23) immunization.

Methods

Markers of inflammation, C-reactive protein (CRP), IL-6, sCD27 and sCD30, were assessed in HIV-positive and -negative individuals as potential predictors of PPV23 response. Serum levels of B cell activating factor (BAFF), transmembrane activator and calcium-modulator and cytophilin ligand interactor (TACI), B cell maturation antigen (BCMA) and B cell expression of BAFF-R, TACI, BCMA, CD40 and CD21 were assessed in total (unselected) and PPS23F (antigen)-specific B cells of PPV23 immunized HIV-positive and -negative individuals.

Results

CRP, sCD27, sCD30 and BAFF were significantly elevated in the serum of HIV-positive individuals but did not adversely affect PPV23 response. Assessment of PPS-specific B cells revealed enhanced TACI and reduced BAFF-R expression compared to unselected B cells in HIV-positive and -negative individuals. Surface TACI was similar but soluble TACI was significantly lower in HIV-positive compared to HIV-negative individuals.

Conclusion

Current studies highlight a potential role for TACI in PPV23 response based on its enhanced expression on PPS-specific B cells. Although surface levels of TACI were similar, diminished soluble TACI (sTACI) in HIV-positive compared to HIV-negative individuals could potentially decrease BAFF responsiveness and Ig response. A better understanding of the role of TNF receptors could contribute to the design of improved pneumococcal vaccines.

Trial Registration

ClinicalTrials.gov NCT02515240

Key differences in B cell activation patterns and immune correlates among treated HIV-infected patients versus healthy controls following influenza vaccination

BACKGROUND

There is increasing recognition of the role of B cell dysfunction in HIV pathogenesis, but little is known about how these perturbations may influence responses to vaccinations.

METHODS

Healthy controls (n=16) and antiretroviral therapy (ART)-treated aviremic HIV-infected subjects (n=26) receiving standard-of-care annual influenza vaccinations were enrolled in the present study. Total bacterial 16S rDNA levels were assessed by quantitative polymerase chain reactions in plasma. Serologic responses were characterized by ELISA, hemagglutination inhibition assay (HI), and microneutralization, and cell-mediated responses were assessed by ELISPOT (antigen-specific IgG+ antibody-secreting cells (ASCs)) and flow cytometry at pre-vaccination (D0), day 7-10 (D7) and day 14-21 (D14) post-vaccination.

RESULTS

Decreased peripheral CD4+ T cell absolute counts and increased frequencies of cycling and apoptotic B cells were found at baseline in HIV-infected subjects relative to healthy controls. In healthy controls, post-vaccination neutralizing activities were related to the frequencies of vaccine-mediated apoptosis and cycling of B cells, but not to CD4+ T cell counts. In patients, both baseline and post-vaccination neutralizing activities were directly correlated with plasma level of bacterial 16S rDNA. However, overall vaccine responses including antibody titers and fold changes were comparable or greater in HIV-infected subjects relative to healthy controls.

CONCLUSION

B cell function correlates with measures of recall humoral immunity in response to seasonal influenza vaccination in healthy controls but not in ART-treated patients.

Interleukin-21 and T follicular helper cells in HIV infection: research focus and future perspectives

Interleukin (IL)-21 is a member of the γ chain-receptor cytokine family along with IL-2, IL-4, IL-7, IL-9, and IL-15. The effects of IL-21 are pleiotropic, owing to the broad cellular distribution of the IL-21 receptor. IL-21 is secreted by activated CD4 T cells and natural killer T cells. Within CD4 T cells, its secretion is restricted mainly to T follicular helper (Tfh) cells and Th17 cells to a lesser extent. Our research focus has been on the role of IL-21 and more recently of Tfh in immunopathogenesis of HIV infection. This review focuses on first the influence of IL-21 in regulation of T cell, B cell, and NK cell responses and its immunotherapeutic potential in viral infections and as a vaccine adjuvant. Second, we discuss the pivotal role of Tfh in generation of antibody responses in HIV-infected persons in studies using influenza vaccines as a probe. Lastly, we review data supporting ability of HIV to infect Tfh and the role of these cells as reservoirs for HIV and their contribution to viral persistence.

The role of B lymphocyte stimulator in B cell biology: implications for the treatment of lupus

B lymphocyte stimulator (BLyS; also known as B cell activating factor (BAFF)) plays a key role in peripheral B cell tolerance. Mounting evidence indicates that B cell tolerance can be either broken or modulated by deliberately manipulating BLyS levels, and belimumab, a BLyS-neutralizing antibody, was recently approved for the treatment of systemic lupus erythematosus (SLE). Thus, intense investigation has focused on understanding how therapeutics targeting BLyS may work, and accumulating evidence suggests multiple points of action. BLyS signaling, in conjunction with B cell receptor (BCR) signaling, determines the size and quality of the mature primary B cell compartment. Moreover, BLyS family members play roles in antigen-experienced B cell selection and differentiation. Together, these findings have implications for the continued development of novel therapeutics that target BLyS.

Relation of activation-induced deaminase (AID) expression with antibody response to A(H1N1)pdm09 vaccination in HIV-1 infected patients

The relevance of CD4+T-cells, viral load and age in the immunological response to influenza infection and vaccination in HIV-1 infected individuals has previously been pointed out. Our study aimed at assessing, in the setting of 2009 A(H1N1)pdm09 influenza vaccination, whether quantification of activation-induced deaminase (AID) expression in blood B-cells may provide additional indications for predicting antibody response to vaccination in HIV-1 infected patients with similar CD4+T-cell counts and age. Forty-seven healthy controls, 37 ART-treated and 17 treatment-naïve HIV-1 infected patients were enrolled in the study. Blood was collected prior to A(H1N1)pdm09 vaccination and at 1, 3 and 6 months after vaccination. Antibody titers to A(H1N1)pdm09 vaccine were measured by hemagglutination inhibition (HI) assay while the mRNA expression levels of AID were measured by quantitative real time PCR. Upon B-cell activation in vitro, AID increase correlated to antibody response to the A(H1N1)pdm09 vaccine at 1 month after vaccination in all individuals. In addition, the maximum expression levels of AID were significantly higher in those individuals who still carried protective levels of A(H1N1)pdm09 antibodies after 6 months from vaccination. No correlation was found between CD4+T-cell counts or age at vaccination or HIV-1 viral load and levels of A(H1N1)pdm09 antibodies. Assessing AID expression before vaccination may be an additional useful tool for defining a vaccination strategy in immune-compromised individuals at risk of immunization failure.

Efficacy and immunogenicity of influenza vaccine in HIV-infected children: a randomized, double-blind, placebo controlled trial

BACKGROUND

HIV-infected children are at heightened risk for severe influenza illness; however, there is no study on the efficacy or effectiveness of influenza vaccine in these children. We evaluated the safety, immunogenicity, and efficacy of nonadjuvanted, trivalent inactivated influenza vaccine (TIV) against confirmed seasonal influenza virus illness in HIV-infected children.

METHODS

A double-blind, placebo-controlled trial was undertaken in Johannesburg in 2009. Four hundred and ten children were randomized to two doses of TIV or placebo 1 month apart. Nasopharyngeal aspirates obtained at respiratory illness visits were tested by influenza-specific reverse transcriptase-PCR (RT-PCR). Vaccine immunogenicity was evaluated by hemagglutinin inhibition (HAI) assay. Influenza isolates were sequenced and evaluated in maximum likelihood phylogenetic analysis.

RESULTS

Overall, the median age of participants was 23.8 months and their median CD4% was 33.5. Ninety-two percent of enrolees were on antiretroviral therapy. Among children receiving both doses of vaccine/placebo, confirmed seasonal influenza illness occurred in 13 (all H3N2) of 205 TIV recipients and 17 (15 H3N2 and two influenza B) of 200 placebo recipients with vaccine efficacy of 17.7% (95% confidence interval <0-62.4%). The proportion of TIV recipients who seroconverted after second dose against vaccine strains of H1N1, H3N2, and influenza B were 47.5, 50.0, and 40.0%, compared to 4.7, 11.6, and 0%, respectively among placebo recipients. There were no TIV-related serious adverse events. Sequence analysis of wild-type H3N2 strains indicated drift from the H3N2 vaccine strain.

CONCLUSION

Poor immunogenicity of TIV, coupled with drift of circulating H3N2 wild-type compared to vaccine strain, may explain the lack of efficacy of TIV in young HIV-infected children. Alternate TIV vaccine schedules or formulations warrant evaluation for efficacy in HIV-infected children.

Immune reconstitution and vaccination outcome in HIV-1 infected children: present knowledge and future directions

Current evidence on routine immunization of HIV-1 infected children point out the need for a special vaccine schedule in this population. However, optimal strategies for identifying individuals susceptible to infections, and then offering them sustained protection through appropriate immunization schedule, both in terms of timing and number of vaccine doses, still remain to be elucidated. Understanding the degree of immune recovery after HAART initiation is important in guiding administration of routine vaccination in HIV-1 infected children. Although quantitative measures (e.g., CD4+ T-cell counts and immunoglobulin levels) are frequently performed to evaluate immune parameters, these measures do not fully mirror functional immune recovery. Here, we will review the status of single mandatory and recommended vaccines for HIV-1 infected children in relation to immune recovery after HAART initiation with the aim of identifying new means to help design personalized vaccine schedules for this population.

The role of interleukin-21 in HIV infection

Interleukin (IL)-21 is one of a group of cytokines including IL-2, IL-4, IL-7, IL-9 and IL-15 whose receptor complexes share the common γ chain (γ(c)). Secretion of IL-21 is restricted mainly to T follicular helper (TFH) CD4 T cell subset with contributions from Th17, natural killer (NK) T cells, but the effects of IL-21 are pleiotropic, owing to the broad cellular distribution of the IL-21 receptor. The role of IL-21 in sustaining and regulating T cell, B cell and NK cell responses during chronic viral infections has recently come into focus. This chapter reviews current knowledge about the biology of IL-21 in the context of HIV infection.

Impaired peripheral blood T-follicular helper cell function in HIV-infected nonresponders to the 2009 H1N1/09 vaccine

The generation of Ab-secreting plasma cells depends critically on CD4 T-follicular helper (TFH) cells during the germinal center reaction. Germinal center TFH cells share functional properties with circulating CXCR5(+) CD4 T cells, referred to herein as peripheral TFH (pTFH) cells. Because deficient Ab production and CD4 T-cell loss are recognized features of HIV infection, in the present study, we investigated pTFH cells in 25 HIV-infected patients on antiretroviral therapy. pTFH frequency was equivalent in patients and healthy controls (HCs), and these cells displayed a central memory phenotype. Sixteen patients and 8 HCs in this group were given a single dose of H1N1/09 influenza vaccine during the 2009 H1N1 influenza outbreak. In the vaccine responders (n = 8) and HCs, pTFH cells underwent expansion with increased IL-21 and CXCL13 secretion in H1N1-stimulated PBMC culture supernatants at week 4 (T2). These changes were not seen in vaccine nonresponders (n = 8). In coculture experiments, sorted pTFH cells supported HIN1-stimulated IgG production by autologous B cells only in vaccine responders. At T2, frequencies of pTFH were correlated with memory B cells, serum H1N1 Ab titers, and Ag-induced IL-21 secretion. Characterization of pTFH cells may provide additional insight into cellular determinants of vaccine-induced Ab response, which may have relevance for vaccine design.

Suboptimal immune reconstitution in vertically HIV infected children: a view on how HIV replication and timing of HAART initiation can impact on T and B-cell compartment

Today, HIV-infected children who have access to treatment face a chronic rather than a progressive and fatal disease. As a result, new challenges are emerging in the field. Recent lines of evidence outline several factors that can differently affect the ability of the immune system to fully reconstitute and to mount specific immune responses in children receiving HAART. In this paper, we review the underlying mechanisms of immune reconstitution after HAART initiation among vertically HIV-infected children analyzing the possible causes of suboptimal responses.

Role of IL-21 and IL-21 receptor on B cells in HIV infection

Interleukin (IL)-21 is a member of a family of cytokines that includes IL-2, IL-4, IL-7, IL-9, and IL-15, all of which utilize a common γ chain in their individual receptor complexes for delivering intracellular signals in their target cells. IL-21 is produced by CD4+ T-cells, in particular follicular T-helper cells, and is critically important in the regulation and maintenance of T cells and B cells in innate and adaptive immunity. The effects of IL-21 are pleiotropic because of the broad cellular distribution of the IL-21 receptor, and it plays a critical role in T cell-dependent and -independent human B cell differentiation for generating humoral immune responses. This article reviews the current knowledge about the importance of IL-21 and IL-21 receptor interaction in human B cell responses, immune defects of B cells and IL-21 in HIV infection, and the potential applicability of IL-21 in vaccines/immunotherapeutic approaches to augment relevant immune responses.

Advances in basic and clinical immunology in 2011

Investigations of basic immunologic mechanisms and clinical studies of primary immunodeficiencies were most prevalent in 2011. Significant progress was achieved in the characterization of T(H)17 cell differentiation and associated cytokines in the setting of inflammatory disorders, HIV infection, and immunodysregulation disorders. The role of transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) mutations in the pathogenesis of CVID was further described and reported to be likely mediated by impaired TACI expression affecting B-cell function. The frequency of autoimmunity in patients with partial DiGeorge syndrome was estimated at 8.5%, predominantly resulting in blood cytopenias and hypothyroidism. Several reports emphasized the presentation of neoplasias, most often lymphomas, as the first manifestation of several primary immunodeficiencies. Novel strategies for newborn screening of B-cell lymphopenia by measuring immunoglobulin κ chain-deletion recombinant excision circles and for adenosine deaminase deficiency using tandem mass spectrometry were demonstrated to be feasible at a large scale. Progress in the treatment of primary immunodeficiencies included increased success with unrelated HLA-compatible donors for hematopoietic stem cell transplantation and the development of new gene therapy approaches with improved safety features. Induced pluripotent stem cells were developed from patients with primary immunodeficiencies, providing a virtually unlimited resource for pathophysiology and gene correction studies. New findings in several of the uncommon immunodeficiencies, such as the increased susceptibility to severe viral infections caused by defects in the activation of the Toll-like receptor 3 pathway, overall contributed to the understanding of their immunologic basis and provided for the design of effective diagnostic and therapeutic strategies.