Loss of HIV-specific memory B-cells as a potential mechanism for the dysfunction of the humoral immune response against HIV

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.

Mpox as AIDS-defining event with a severe and protracted course: clinical, immunological, and virological implications

A 59-year-old treatment-naive patient with advanced HIV infection presented with a severe and protracted course of mpox (formerly known as monkeypox) that did not respond to the current mpox treatment options. The patient worsened clinically, and developed new mucocutaneous lesions and necrotic evolution of pre-existing ones, along with multiple bilateral lung nodules and the appearance of a tracheal necrotic lesion. Although severe forms of mpox have been observed in people with severe immune system deficiency, including those with advanced HIV presentation, the immunological mechanisms underlying this observation have not yet been fully explained. To our knowledge, this is the first account of a necrotising mpox in a person living with HIV, with viral shedding for more than 11 months and a comprehensive immunological description. Moreover, we documented the virus' persistence by detecting mpox virus DNA from multiple sites and quantified anti-monkeypox virus IgA, IgM, IgG, and neutralising antibodies in serum samples. The severe HIV-driven immune depression and the presence of other co-infections might skew and impair immune responses, thus contributing to the persistence of monkeypox virus infection. Further investigations of immune responses to monkeypox virus infection in people with severe immunosuppression are required to improve management and prevention.

Association between SARS-CoV-2 RNAemia, skewed T cell responses, inflammation, and severity in hospitalized COVID-19 people living with HIV

Severe COVID-19 outcomes have been reported in people living with HIV (PLWH), yet the underlying pathogenetic factors are largely unknown. We therefore aimed to assess SARS-CoV-2 RNAemia and plasma cytokines in PLWH hospitalized for COVID-19 pneumonia, exploring associations with magnitude and functionality of SARS-CoV-2-specific immune responses. Eighteen unvaccinated PLWH (16/18 on cART; median CD4 T cell count 361.5/μL; HIV-RNA<50 cp/mL in 15/18) and 18 age/sex-matched people without HIV were consecutively recruited at a median time of 10 days from symptoms onset. PLWH showed greater SARS-CoV-2 RNAemia, a distinct plasma cytokine profile, and worse respiratory function (lower PaO2/FiO2nadir), all correlating with skewed T cell responses (higher perforin production by cytotoxic T cells as well as fewer and less polyfunctional SARS-CoV-2-specific T cells), despite preserved humoral immunity. In conclusion, these data suggest a link between HIV-related T cell dysfunction and poor control over SARS-CoV-2 replication/dissemination that may in turn influence COVID-19 severity in PLWH.

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.

Immunologic Interplay Between HIV/AIDS and COVID-19: Adding Fuel to the Flames?

PURPOSE OF REVIEW

HIV/AIDS and COVID-19 have been the major pandemics overwhelming our times. Given the enduring immune disfunction featuring people living with HIV (PLWH) despite combination antiretroviral therapy (cART), concerns for higher incidence and severity of SARS-CoV-2 infection as well as for suboptimal responses to the newly developed vaccines in this population arose early during the pandemics. Herein, we discuss the complex interplay between HIV and SARS-CoV-2, with a special focus on the immune responses to SARS-CoV-2 natural infection and vaccination in PLWH.

RECENT FINDINGS

Overall, current literature shows that COVID-19 severity and outcomes may be worse and immune responses to infection or vaccination lower in PLWH with poor CD4 + T-cell counts and/or uncontrolled HIV viremia. Data regarding the risk of post-acute sequelae of SARS-CoV-2 infection (PASC) among PLWH are extremely scarce, yet they seem to suggest a higher incidence of such condition. Scarce immunovirological control appears to be the major driver of weak immune responses to SARS-CoV-2 infection/vaccination and worse COVID-19 outcomes in PLWH. Therefore, such individuals should be prioritized for vaccination and should receive additional vaccine doses. Furthermore, given the potentially higher risk of developing long-term sequelae, PLWH who experienced COVID-19 should be ensured a more careful and prolonged follow-up.

Association of envelope-specific B-cell differentiation and viral selective pressure signatures in HIV-1 CRF01_AE infection

OBJECTIVE

In HIV type 1 (HIV-1) infection, virus-specific B-cell and neutralizing antibody (NAb) responses are impaired but exert selective pressure on target viral Envelope (Env) resulting in prominent sequence diversification among geographical areas. The basal induction patterns of HIV Env-specific B cells and their interaction with HIV Env awaits clarification.

DESIGN

We investigated the relationship of Env polymorphisms and Env-specific B-cell responses in treatment-naive HIV-1 CRF01_AE-infected Vietnamese.

METHODS

Samples of 43 HIV-1 CRF01_AE infection-identified individuals were divided into acute-phase ( n  = 12) and chronic-phase ( n  = 31) by combined criteria of serological recent-infection assay and clinical parameters. We quantified subcloning-based polymorphic residue site numbers in plasma-derived Env variable region 1-5 (V1-V5)-coding regions within each individual, designating their summation within each region as variant index. Peripheral blood Env gp 140-specific B-cell responses and plasma neutralizing activity of Env pseudoviruses were examined to analyze their relationship with variant index.

RESULTS

HIV-1 CRF01_AE Env gp140-specific total B-cell and plasma cell (CD19 + IgD - CD27 + CD38 + CD138 + ) responses were determined. In chronic-phase samples, significant correlation of variant index in all Env V1-V5 regions with Env-specific plasma cell responses was shown, and V1-V5 total variant index correlated stronger with Env-specific plasma cell as compared with total Env-specific B-cell responses. Env V5 variant index was significantly higher in chronic-phase cross-neutralizers of V5-polymorphic/VRC01-insensitive CRF01_AE Env.

CONCLUSION

Results revealed the association between circulating Env-specific plasma cell responses and Env polymorphisms, implicating selective pressure on Env by plasma cell-derived antibodies and conversely suggests that Env-specific B-cell induction alone is insufficient for exerting Env selective pressure in HIV infection.

SARS-CoV-2 immunity and vaccine strategies in people with HIV

Current severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines, based on the ancestral Wuhan strain, were developed rapidly to meet the needs of a devastating global pandemic. People living with Human Immunodeficiency Virus (PLWH) have been designated as a priority group for SARS-CoV-2 vaccination in most regions and varying primary courses (two- or three-dose schedule) and additional boosters are recommended depending on current CD4+ T cell count and/or detectable HIV viraemia. From the current published data, licensed vaccines are safe for PLWH, and stimulate robust responses to vaccination in those well controlled on antiretroviral therapy and with high CD4+ T cell counts. Data on vaccine efficacy and immunogenicity remain, however, scarce in PLWH, especially in people with advanced disease. A greater concern is a potentially diminished immune response to the primary course and subsequent boosters, as well as an attenuated magnitude and durability of protective immune responses. A detailed understanding of the breadth and durability of humoral and T cell responses to vaccination, and the boosting effects of natural immunity to SARS-CoV-2, in more diverse populations of PLWH with a spectrum of HIV-related immunosuppression is therefore critical. This article summarizes focused studies of humoral and cellular responses to SARS-CoV-2 infection in PLWH and provides a comprehensive review of the emerging literature on SARS-CoV-2 vaccine responses. Emphasis is placed on the potential effect of HIV-related factors and presence of co-morbidities modulating responses to SARS-CoV-2 vaccination, and the remaining challenges informing the optimal vaccination strategy to elicit enduring responses against existing and emerging variants in PLWH.

Natural Killer Cells in Antibody Independent and Antibody Dependent HIV Control

Infection with the human immunodeficiency virus (HIV), when left untreated, typically leads to disease progression towards acquired immunodeficiency syndrome. Some people living with HIV (PLWH) control their virus to levels below the limit of detection of standard viral load assays, without treatment. As such, they represent examples of a functional HIV cure. These individuals, called Elite Controllers (ECs), are rare, making up <1% of PLWH. Genome wide association studies mapped genes in the major histocompatibility complex (MHC) class I region as important in HIV control. ECs have potent virus specific CD8⁺ T cell responses often restricted by protective MHC class I antigens. Natural Killer (NK) cells are innate immune cells whose activation state depends on the integration of activating and inhibitory signals arising from cell surface receptors interacting with their ligands on neighboring cells. Inhibitory NK cell receptors also use a subset of MHC class I antigens as ligands. This interaction educates NK cells, priming them to respond to HIV infected cell with reduced MHC class I antigen expression levels. NK cells can also be activated through the crosslinking of the activating NK cell receptor, CD16, which binds the fragment crystallizable portion of immunoglobulin G. This mode of activation confers NK cells with specificity to HIV infected cells when the antigen binding portion of CD16 bound immunoglobulin G recognizes HIV Envelope on infected cells. Here, we review the role of NK cells in antibody independent and antibody dependent HIV control.

Transient viral exposure drives functionally-coordinated humoral immune responses in HIV-1 post-treatment controllers

HIV-1 post-treatment controllers are rare individuals controlling HIV-1 infection for years after antiretroviral therapy interruption. Identification of immune correlates of control in post-treatment controllers could aid in designing effective HIV-1 vaccine and remission strategies. Here, we perform comprehensive immunoprofiling of the humoral response to HIV-1 in long-term post-treatment controllers. Global multivariate analyses combining clinico-virological and humoral immune data reveal distinct profiles in post-treatment controllers experiencing transient viremic episodes off therapy compared to those stably aviremic. Virally-exposed post-treatment controllers display stronger HIV-1 humoral responses, and develop more frequently Env-specific memory B cells and cross-neutralizing antibodies. Both are linked to short viremic exposures, which are also accompanied by an increase in blood atypical memory B cells and activated subsets of circulating follicular helper T cells. Still, most humoral immune variables only correlate with Th2-like circulating follicular helper T cells. Thus, post-treatment controllers form a heterogeneous group with two distinct viral behaviours and associated immune signatures. Post-treatment controllers stably aviremic present “silent” humoral profiles, while those virally-exposed develop functionally robust HIV-specific B-cell and antibody responses, which may participate in controlling infection.

Helios expressing regulatory T cells are correlated with decreased IL-2 producing CD8 T cells and antibody diversity in Mozambican individuals living chronically with HIV-1

Background

Human immunodeficiency virus type 1 (HIV-1) causes impairment of T and B cell responses, which begins during the acute phase of infection and is not completely restored by antiretroviral treatment. Regulatory T cell (Tregs) can improve overall disease outcome by controlling chronic inflammation but may also suppress beneficial HIV-1 specific immune responses. We aimed to analyze the profile of Tregs and their correlation with the status of T cells activation, the expression of IL-2 and IFNγ and the profile of HIV-1 specific antibodies response in Mozambican people living chronically with HIV-1 (PLWH-C).

Results

In PLWH-C, the proportion of total Tregs was positively correlated with the proportion of IL-2⁺CD4 T cells (r = 0.647; p = 0.032) and IL-2⁺IFNγ⁺CD8 T cells (r = 0.551; p = 0.014), while the proportions of Helios⁺Tregs correlated inversely with levels of IL-2⁺CD8 T cells (r = − 0.541; p = 0.017). Overall, PLWH-C, with (82%) or without virologic suppression (64%), were seronegative for at least HIV-1 p31, gp160 or p24, and the breadth of antibody responses was positively correlated with proportions of CD38⁺HLA-DR⁺CD8 T cells (r = 0.620; p = 0.012), viral load (r = 0.452; p = 0.040) and inversely with absolute CD4 T cells count (r = − 0.481; p = 0.027). Analysis of all individuals living HIV-1 showed that the breadth of HIV-1 antibody responses was inversely correlated with the proportion of Helios⁺Tregs (r = − 0.45; p = 0.02).

Conclusion

Among Mozambican people living with HIV-1, seronegativity to some HIV-1 proteins is common, particularly in virologically suppressed individuals. Furthermore, lower diversity of HIV-specific antibodies is correlated to lower immune activation, lower viral replication and higher CD4 counts, in PLWH-C. Elevation in the proportion of Helios⁺Tregs is related to a reduction of CD8 T expressing intracellular IL-2, in PLWH-C, but may contribute to impairment of B cell function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00487-3.

OUP accepted manuscript

Background

Methods

Results

Conclusions

Qualitative assessment of anti-SARS-CoV-2 spike protein immunogenicity (QUASI) after COVID-19 vaccination in older people living with HIV

Objectives

Effective and safe COVID‐19 vaccines have been developed and have resulted in decreased incidence and severity of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and can decrease secondary transmission. However, there are concerns about dampened immune responses to COVID‐19 vaccination among immunocompromised patients, including people living with HIV (PLWH), which may blunt the vaccine's efficacy and durability of protection. This study aimed to assess the qualitative SARS‐CoV‐2 vaccine immunogenicity among PLWH after vaccination.

Methods

We conducted targeted COVID‐19 vaccination (all received BNT162b2 vaccine) of PLWH (aged ≥ 55 years per state guidelines) at Yale New Haven Health System and established a longitudinal survey to assess their qualitative antibody responses at 3 weeks after the first vaccination (and prior to receipt of the second dose of the COVID‐19 vaccine) (visit 1) and at 2–3 weeks after the second vaccination (visit 2) but excluded patients with prior COVID‐19 infection. Our goal was to assess vaccine‐induced immunity in the population we studied. Qualitative immunogenicity testing was performed using Healgen COVID‐19 anti‐Spike IgG/IgM rapid testing. Poisson regression with robust standard errors was used to determine factors associated with a positive IgG response.

Results

At visit 1, 45 of 78 subjects (57.7%) tested positive for SARS‐CoV‐2 anti‐Spike IgG after the first dose of COVID‐19 vaccine. Thirty‐nine subjects returned for visit 2. Of these, 38 had positive IgG (97.5%), including 20 of 21 subjects (95.2%) with an initial negative anti‐Spike IgG. Our bivariate analysis suggested that participants on an antiretroviral regimen containing integrase strand transfer inhibitors [relative risk (RR) = 1.81, 95% confidence interval (CI): 0.92–3.56, p = 0.085] were more likely to seroconvert after the first dose of the COVID‐19 vaccine, while those with a CD4 count < 500 cells/μL (RR = 0.59, 95% CI: 0.33–1.05, p = 0.071), and those diagnosed with cancer or another immunosuppressive condition (RR = 0.49, 95% CI: 0.18–1.28, p = 0.15) may have been less likely to seroconvert after the first dose of the COVID‐19 vaccine. The direction of these associations was similar in the multivariate model, although none of these findings reached statistical significance (RR_{integrase inhibitor} = 1.71, 95% CI: 0.90–3.25, p = 0.10; RR_{CD4 count} = 0.68, 95% CI: 0.39–1.19, p = 0.18; RR_{cancer or another immunosuppressive condition} = 0.50, 95% CI: 0.19–1.33, p = 0.16). With regard to immunogenicity, we were able to record very high rates of new seroconversion following the second dose of the COVID‐19 vaccine.

Conclusions

Our study suggests that completing a two‐dose series of BNT162b2 vaccine is critical for PLWH given suboptimal seroconversion rates after the first dose and subsequent improved seroconversion rates after the second dose.

Polyfunctional Fc Dependent Activity of Antibodies to Native Trimeric Envelope in HIV Elite Controllers

Antibody dependent (AD) functions such as AD cellular cytotoxicity (ADCC) were associated with lower viral load (VL) in untreated HIV progressors and protection from HIV infection in the modestly protective RV144 HIV vaccine trial. Target cells used to measure ADCC, AD complement deposition (ADCD), and AD cellular trogocytosis (ADCT) have been either HIV envelope (Env) gp120-coated CEM.NKr.CCR5 cells or HIV infected cell cultures. In HIV infected cell cultures, uninfected bystander cells take up gp120 shed from infected cells. Both gp120-coated and gp120+ bystander cells expose CD4 induced (CD4i) epitopes, which are normally hidden in native trimeric Env expressed by genuinely HIV infected cells since Nef and Vpu downmodulate cell surface CD4. Antibody dependent assays using either of these target cells probe for CD4i Abs that are abundant in HIV⁺ plasma but that do not recognize HIV-infected cells. Here, we examined ADCC, ADCD, and ADCT functions using a target cell line, sorted HIV-infected cell line cells, whose HIV infection frequency nears 100% and that expresses HIV Env in a native trimeric closed conformation. Using sorted HIV-infected cells (siCEM) as targets, we probed the binding and AD functions of anti-gp120/Env Abs in plasma from HIV-infected untreated progressor (UTP, n = 18) and treated (TP, n = 24) subjects, compared to that in Elite controllers (EC, n = 37) and Viral Controllers (VC, n = 16), which are rare subsets of HIV-infected individuals who maintain undetectable or low VL, respectively, without treatment. Gp120-coated beads were used to measure AD cellular phagocytosis. Equivalent concentrations of input IgG in plasma from UTPs, ECs, and VCs supported higher levels of all AD functions tested than plasma from TPs. When AD activities were normalized to the concentration of anti-gp120/Env-specific Abs, between-group differences largely disappeared. This finding suggests that the anti-gp120/Env Abs concentrations and not their potency determined AD functional levels in these assays. Elite controllers did differ from the other groups by having AD functions that were highly polyfunctional and highly correlated with each other. PCR measurement of HIV reservoir size showed that ADCC activity was higher in ECs and VCs with a reservoir size below the limit of detection compared to those having a measurable HIV reservoir size.

Immunological approaches to HIV cure

Combination antiretroviral therapy (ART) to treat human immunodeficiency virus (HIV) infection has proven remarkably successful - for those who can access and afford it - yet HIV infection persists indefinitely in a reservoir of cells, despite effective ART and despite host antiviral immune responses. An HIV cure is therefore the next aspirational goal and challenge, though approaches differ in their objectives - with 'functional cures' aiming for durable viral control in the absence of ART, and 'sterilizing cures' aiming for the more difficult to realize objective of complete viral eradication. Mechanisms of HIV persistence, including viral latency, anatomical sequestration, suboptimal immune functioning, reservoir replenishment, target cell-intrinsic immune resistance, and, potentially, target cell distraction of immune effectors, likely need to be overcome in order to achieve a cure. A small fraction of people living with HIV (PLWH) naturally control infection via immune-mediated mechanisms, however, providing both sound rationale and optimism that an immunological approach to cure is possible. Herein we review up to date knowledge and emerging evidence on: the mechanisms contributing to HIV persistence, as well as potential strategies to overcome these barriers; promising immunological approaches to achieve viral control and elimination of reservoir-harboring cells, including harnessing adaptive immune responses to HIV and engineered therapies, as well as enhancers of their functions and of complementary innate immune functioning; and combination strategies that are most likely to succeed. Ultimately, a cure must be safe, effective, durable, and, eventually, scalable in order to be widely acceptable and available.

Higher frequencies of functional HIV-envelope-specific memory B cells are associated with nonprogressive HIV infection in Indian population

OBJECTIVE

The HIV-1-specific antibodies are being considered for prevention and therapy in HIV infection. For effective antibody response, presence of functionally competent memory B cells (MEBs) is important; however, HIV-infection is known to alter the B-cell functionality. Very limited data are available on the HIV-specific memory B-cell population in HIV-infected Indian population.

METHODS

In this study, the frequencies of HIV-gp140-specific MEBs were measured in individuals with nonprogressive [long-term-nonprogressors (LTNPs), N = 20] and progressive (N = 19) HIV infection using multicolor flow cytometry. The activation and functional status of these MEBs were assessed as frequencies and mean fluorescence intensity (MFI) of the CD38 and CD40 expression, respectively.

RESULTS

The percentages of gp140 + MEBs were higher in LTNPs than seen in progressors (P = 0.0475) and associated with higher CD4 cell count (P = 0.0312, r = 0.2833). As compared with the progressors, LTNPs also showed higher functional (CD40+) gp140 + MEBs both frequencies (P < 0.0001) and CD40 MFI (P = 0.0222), whereas the frequencies (<0.0001) and the MFI (P = 0.0047) of CD38 expression was significantly lower. Higher CD4 cell counts and lower plasma viral load values were associated with higher frequencies of CD40+ gp140 + MEBs (P < 0.0001, r = 0.4962) (P = 0.0036, r = -0.4202) and lower frequencies (P = 0.0008, r = -0.4231) and CD38 expression (MFI) (P = 0.004, r = -0.3719) (P = 0.0066, r = 0.4033).

CONCLUSION

Our study suggests that LTNPs have functional HIV-specific memory B-cell compartment with reduced activation that may lead to effective HIV-specific humoral immune responses contributing to their nondisease progression status. These findings would help in better understanding of the characteristics of the HIV-specific memory B-cell population in nonprogressive HIV infection.

A role for antibodies in natural HIV control

PURPOSE OF REVIEW

Rare patients naturally control HIV replication without antiretroviral therapy. Understanding the mechanisms implicated in natural HIV control will inform the development of immunotherapies against HIV. Elite controllers are known for developing efficient antiviral T-cell responses, but recent findings suggest that antibody responses also play a significant role in HIV control. We review the key studies that uncovered a potent memory B-cell response and highly functional anti-HIV antibodies in elite controllers, and explore the mechanisms that may account for the distinct properties of their humoral response.

RECENT FINDINGS

Elite controllers maintain a large HIV-specific memory B-cell pool that is sustained by efficient T follicular helper function. Neutralizing antibody rarely show high titers in controllers, but seem capable, at least in certain cases, of neutralizing contemporaneous viral strains. In addition, elite controllers display a unique HIV-specific antibody profile in terms of isotype, antigen specificity, and glycosylation pattern, resulting in polyfunctional antibody effector functions that may promote infected cell lysis and prime effectors of the antiviral immune response.

SUMMARY

Lessons from elite controller studies argue for the importance of integrating the many parameters defining a polyfunctional antibody response when evaluating candidate vaccines and immunotherapeutic approaches directed at HIV.

A High Frequency of HIV-Specific Circulating Follicular Helper T Cells Is Associated with Preserved Memory B Cell Responses in HIV Controllers

Follicular helper T cells (Tfh) play an essential role in the affinity maturation of the antibody response by providing help to B cells. To determine whether this CD4⁺ T cell subset may contribute to the spontaneous control of HIV infection, we analyzed the phenotype and function of circulating Tfh (cTfh) in patients from the ANRS CO21 CODEX cohort who naturally controlled HIV-1 replication to undetectable levels and compared them to treated patients with similarly low viral loads. HIV-specific cTfh (Tet⁺), detected by Gag-major histocompatibility complex class II (MHC-II) tetramer labeling in the CD45RA⁻ CXCR5⁺ CD4⁺ T cell population, proved more frequent in the controller group (P = 0.002). The frequency of PD-1 expression in Tet⁺ cTfh was increased in both groups (median, >75%) compared to total cTfh (<30%), but the intensity of PD-1 expression per cell remained higher in the treated patient group (P = 0.02), pointing to the persistence of abnormal immune activation in treated patients. The function of cTfh, analyzed by the capacity to promote IgG secretion in cocultures with autologous memory B cells, did not show major differences between groups in terms of total IgG production but proved significantly more efficient in the controller group when measuring HIV-specific IgG production. The frequency of Tet⁺ cTfh correlated with HIV-specific IgG production (R = 0.71 for Gag-specific and R = 0.79 for Env-specific IgG, respectively). Taken together, our findings indicate that key cTfh-B cell interactions are preserved in controlled HIV infection, resulting in potent memory B cell responses that may play an underappreciated role in HIV control.

The rare patients who spontaneously control HIV replication in the absence of therapy provide a unique model to identify determinants of an effective anti-HIV immune response. HIV controllers show signs of particularly efficient antiviral T cell responses, while their humoral response was until recently considered to play only a minor role in viral control. However, emerging evidence suggests that HIV controllers maintain a significant but “silent” antiviral memory B cell population that can be reactivated upon antigenic stimulation. We report that cTfh help likely contributes to the persistence of controller memory B cell responses, as the frequency of HIV-specific cTfh correlated with the induction of HIV-specific antibodies in functional assays. These findings suggest that T follicular help may contribute to HIV control and highlight the need for inducing such help in HIV vaccine strategies that aim at eliciting persistent B cell responses.

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.

Irreversible phenotypic perturbation and functional impairment of B cells during HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) infection can damage humoral immunity. The knowledge of B cell perturbations during chronic HIV-1 infection and their recovery after combined antiretroviral therapy (cART) is not complete yet, and thus attempts to further improve humoral immunity are impeded. In this study, an HIV-1 chronically infected cohort with similar demographics, infection history, genetic background, and HIV-1 genotype was established to probe B cell perturbations. Results showed that the B cells from this cohort were highly activated and prone to cell death, and B cell compartments were altered significantly. Notably, although cART partially reversed the hyperactivation and reduced tissue-like memory B cells, other B cell perturbations, including impaired expression of survival factor Bcl-2, costimulatory molecules, and shrunken resting memory B cells, were irreversible. Further functional characterization revealed that the influenza HAspecific antibody-secreting cells were significantly lower during HIV-1 infection, whereas the recalled antibody response to HIV-1-specific antigens was decreased after cART. Finally, CpG plus R848 treatment increased the survival of B cells and memory B cells in vitro from HIV-1-infected patients. In conclusion, this study identified irreversible B cell immune perturbations in chronic HIV-1 infections regardless of cART and proposed the potential strategy to enhance B cell functions through the improvement of cell survival.

HIV-Specific B Cell Frequency Correlates with Neutralization Breadth in Patients Naturally Controlling HIV-Infection

HIV-specific broadly neutralizing antibodies (bnAbs) have been isolated from patients with high viremia but also from HIV controllers that repress HIV-1 replication. In these elite controllers (ECs), multiple parameters contribute to viral suppression, including genetic factors and immune responses. Defining the immune correlates associated with the generation of bnAbs may help in designing efficient immunotherapies. In this study, in ECs either positive or negative for the HLA-B*57 protective allele, in treated HIV-infected and HIV-negative individuals, we characterized memory B cell compartments and HIV-specific memory B cells responses using flow cytometry and ELISPOT. ECs preserved their memory B cell compartments and in contrast to treated patients, maintained detectable HIV-specific memory B cell responses. All ECs presented IgG1 + HIV-specific memory B cells but some individuals also preserved IgG2 + or IgG3 + responses. Importantly, we also analyzed the capacity of sera from ECs to neutralize a panel of HIV strains including transmitted/founder virus. 29% and 21% of HLA-B*57 + and HLA-B*57 − ECs, respectively, neutralized at least 40% of the viral strains tested. Remarkably, in HLA-B*57 + ECs the frequency of HIV-Env-specific memory B cells correlated positively with the neutralization breadth suggesting that preservation of HIV-specific memory B cells might contribute to the neutralizing responses in these patients.

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In contrast to treated HIV-infected patients, elite controllers (ECs) maintain HIV-specific memory B cell responses.

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In HLA-B*57 + ECs, HIV-specific B cell frequency correlates positively with the neutralization breadth of tier-2 HIV strains.

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In HLA-B*57 + and HLA-B*57 − ECs different antibody functions are probably involved in suppressing HIV replication.

A fraction of HIV-1-infected individuals (so-called elite controllers, ECs) naturally control HIV-1 replication maintaining undetectable viral loads. Understanding the mechanisms implicated in natural control of HIV-1 infection will help in developing efficient HIV vaccines. In ECs, we analyzed the influence of B cell antibody responses. We show that in contrast to successfully treated HIV-1-infected patients, ECs preserve memory B cell compartments and maintain HIV-specific B cell responses. In ECs positive for the protective HLA-B*57 allele, HIV-specific memory B cell responses are positively associated with the breadth of HIV neutralization. These findings will help develop novel immunotherapies to fight HIV.

Expression of programmed cell death1 in T follicular helper cells is regulated by prostaglandin E2 secreted by HBV-infected HepG2.2.1.5 cells

The present study aimed to investigate the distribution of T follicular helper (Tfh)-cell subsets in patients with hepatitis B virus (HBV) and determine the underlying mechanism of HBV regulation of Tfh cells. The frequency of peripheral blood Tfh subsets was analyzed using flow cytometry. The expression level of programmed cell death‑1 (PD‑1) and prostaglandin E2 (PGE2) was quantified using reverse transcription‑quantitative polymerase chain reaction and western blotting. The PGE2 level in culture supernatant was detected using enzyme‑linked immunosorbent assay. A Transwell chamber was used to co‑culture Tfh cells with HepG2 and HepG2.2.1.5. The percentage of inducible T‑cell costimulator (ICOS)+ and total Tfh cells was high at the immune activation (IA) group; however, it was reduced in the immune tolerance (IT), responders with HBsAg seroconversion (RP) and healthy control (HC) groups. The percentage of PD‑1+ Tfh cells was significantly higher in IA and IT compared with RP and HC. The ratio of PD‑1+/total Tfh cells was positively correlated with the load of HBV DNA; therefore, this ratio may act as an indicator for HBV replication. The expression level of PD‑1 in Tfh cells was higher in the HepG2.2.1.5 co‑cultured group compared with the HepG2 group, this may be due to the high PGE2 expression level in HBV‑infected HepG2.2.1.5 cells. The findings of the present study revealed an imbalanced distribution of PD‑1+ Tfh cells in patients with HBV at different immune phases. Additionally, HBV may upregulate the expression of PD‑1 in Tfh cells by promoting HepG2.2.1.5 to secret PGE2. Identifying the effect of HBV on Tfh‑cell subsets is crucial for improving immuno-based therapy for HBV.

B-cell responses to HIV infection

The induction of neutralizing antibodies directed against the human immunodeficiency virus (HIV) has received considerable attention in recent years, in part driven by renewed interest and opportunities for antibody-based strategies for prevention such as passive transfer of antibodies and the development of preventive vaccines, as well as immune-based therapeutic interventions. Advances in the ability to screen, isolate, and characterize HIV-specific antibodies have led to the identification of a new generation of potent broadly neutralizing antibodies (bNAbs). The majority of these antibodies have been isolated from B cells of chronically HIV-infected individuals with detectable viremia. In this review, we provide insight into the phenotypic and functional attributes of human B cells, with a focus on HIV-specific memory B cells and plasmablasts/cells that are responsible for sustaining humoral immune responses against HIV. We discuss the abnormalities in B cells that occur in HIV infection both in the peripheral blood and lymphoid tissues, especially in the setting of persisting viremia. Finally, we consider the opportunities and drawbacks of intensively interrogating antibodies isolated from HIV-infected individuals to guide strategies aimed at developing effective antibody-based vaccine and therapeutic interventions for HIV.

Maintenance of HIV-Specific Memory B-Cell Responses in Elite Controllers Despite Low Viral Burdens

Human immunodeficiency virus (HIV)-specific B-cell responses in infected individuals are maintained by active HIV replication. Suppression of viremia by antiretroviral therapy (ART) leads to quantitative and qualitative changes that remain unclear. Accordingly, B-cell responses were investigated in elite controllers (ECs), who maintain undetectable HIV levels without ART, and in individuals whose viremia was suppressed by ART. Despite a higher HIV burden in the ART group, compared with the EC group, frequencies of HIV-specific B cells were higher in the EC group, compared with those in the ART group. However, the initiation of ART in several ECs was associated with reduced frequencies of HIV-specific B cells, suggesting that responses are at least in part sustained by HIV replication. Furthermore, B-cell responses to tetanus toxin but not influenza hemagglutinin in the ART group were lower than those in the EC group. Thus, the superior HIV-specific humoral response in ECs versus ART-treated individuals is likely due to a more intact humoral immune response in ECs and/or distinct responses to residual HIV replication.

Reversible Reprogramming of Circulating Memory T Follicular Helper Cell Function during Chronic HIV Infection

Despite the overwhelming benefits of antiretroviral therapy (ART) in curtailing viral load in HIV-infected individuals, ART does not fully restore cellular and humoral immunity. HIV-infected individuals under ART show reduced responses to vaccination and infections and are unable to mount an effective antiviral immune response upon ART cessation. Many factors contribute to these defects, including persistent inflammation, especially in lymphoid tissues, where T follicular helper (Tfh) cells instruct and help B cells launch an effective humoral immune response. In this study we investigated the phenotype and function of circulating memory Tfh cells as a surrogate of Tfh cells in lymph nodes and found significant impairment of this cell population in chronically HIV-infected individuals, leading to reduced B cell responses. We further show that these aberrant memory Tfh cells exhibit an IL-2-responsive gene signature and are more polarized toward a Th1 phenotype. Treatment of functional memory Tfh cells with IL-2 was able to recapitulate the detrimental reprogramming. Importantly, this defect was reversible, as interfering with the IL-2 signaling pathway helped reverse the abnormal differentiation and improved Ab responses. Thus, reversible reprogramming of memory Tfh cells in HIV-infected individuals could be used to enhance Ab responses. Altered microenvironmental conditions in lymphoid tissues leading to altered Tfh cell differentiation could provide one explanation for the poor responsiveness of HIV-infected individuals to new Ags. This explanation has important implications for the development of therapeutic interventions to enhance HIV- and vaccine-mediated Ab responses in patients under ART.

Persistent subclinical immune defects in HIV-1-infected children treated with antiretroviral therapy

OBJECTIVES

With the introduction of combined antiretroviral therapy (cART), HIV-infected children can reach adulthood with minimal clinical complications. However, long-term HIV and cART in adults are associated with immunosenescence and end-organ damage. Long-term consequences of HIV and cART in children are currently unknown.

DESIGN AND METHOD

We studied 69 HIV-infected children and adolescents under cART (0-23 years) for the occurrence of subclinical immunological aberrations in blood B and T cells, using detailed flow cytometric immunophenotyping and molecular analyses.

RESULTS

Children with undetectable plasma HIV viral loads for more than 1 year showed near-normal to normal CD4 T-cell numbers and near-normal numbers of most class-switched memory B cells. Furthermore, expansions of aberrant CD21 B cells contracted in patients with virus suppression. In contrast, CD8 effector T cells were increased, and CD4 memory T cells, Vγ9Vδ2 T cells and CD27IgA memory B cells were decreased and did not normalize under ART. Moreover, Vγ9Vδ2 T cells showed defects in their T-cell receptor repertoire selection.

CONCLUSION

Our results show the effectiveness of current cART to enable the build-up of phenotypically diverse B-cell and T-cell memory in HIV-infected children. However, several subclinical immune abnormalities were detected, which were partially caused by defective immune maturation. These persistent abnormalities were most severe in adolescents and therefore warrant long-term follow-up of HIV-infected children. Early identification of such immune defects might provide targets for monitoring future treatment optimization.

High Inter-Individual Diversity of Point Mutations, Insertions, and Deletions in Human Influenza Virus Nucleoprotein-Specific Memory B Cells

The diversity of virus-specific antibodies and of B cells among different individuals is unknown. Using single-cell cloning of antibody genes, we generated recombinant human monoclonal antibodies from influenza nucleoprotein-specific memory B cells in four adult humans with and without preceding influenza vaccination. We examined the diversity of the antibody repertoires and found that NP-specific B cells used numerous immunoglobulin genes. The heavy chains (HCs) originated from 26 and the kappa light chains (LCs) from 19 different germ line genes. Matching HC and LC chains gave rise to 43 genetically distinct antibodies that bound influenza NP. The median lengths of the CDR3 of the HC, kappa and lambda LC were 14, 9 and 11 amino acids, respectively. We identified changes at 13.6% of the amino acid positions in the V gene of the antibody heavy chain, at 8.4% in the kappa and at 10.6 % in the lambda V gene. We identified somatic insertions or deletions in 8.1% of the variable genes. We also found several small groups of clonal relatives that were highly diversified. Our findings demonstrate broadly diverse memory B cell repertoires for the influenza nucleoprotein. We found extensive variation within individuals with a high number of point mutations, insertions, and deletions, and extensive clonal diversification. Thus, structurally conserved proteins can elicit broadly diverse and highly mutated B-cell responses.

Serum free light chains in patients with HIV infection: their association with markers of disease severity and antiretroviral use

AIM

Serum free light chain measurements are used to follow-up and manage patients with monoclonal gammopathies, and abnormal ratios are associated with risk of progression in certain diseases. B cell dysfunction is well described in HIV and patients are at risk of developing B cell lymphomas. This study investigated whether HIV is associated with abnormal free light chain levels and the impact of antiretroviral treatment (ART) on these.

METHODS

κ And λ free light chain concentrations and ratios, serum albumin and immunoglobulin G (IgG) were measured in 366 HIV positive subjects and correlated with CD4+ counts, viral loads, IgG, albumin and ART use.

RESULTS

66% were women and most were black Africans (66%), 26% were of mixed ethnicity and 8% were Caucasian or of unknown or other race. 89% were on ART. κ Free light chain values ranged from 5.59 to 357.0 mg/L (median 19.6 mg/L) and λ free light chain values ranged from 9.28 to 286 mg/L (median 22.3 mg/L). Both correlated positively with viral load and IgG and negatively with CD4+ counts and albumin concentrations. The ratio only correlated with IgG concentrations. Patients on ART had significantly lower free light chain concentrations, but the ratio was not significantly affected.

CONCLUSIONS

This study demonstrated that free light chain concentrations were significantly correlated with markers of HIV disease severity, suggesting ongoing B cell dysfunction despite ART use. Free light chain ratio was not significantly affected.

Patients co-infected with hepatitis C virus (HCV) and human immunodeficiency virus recover genotype cross-reactive neutralising antibodies to HCV during antiretroviral therapy

When severely immunodeficient HIV/HCV co-infected patients are treated with antiretroviral therapy, it is important to know whether HCV-specific antibody responses recover and whether antibody profiles predict the occurrence of HCV-associated immune restoration disease (IRD). In 50 HIV/HCV co-infected patients, we found that antibody reactivity and titres of neutralising antibodies (nAb) to JFH-1 (HCV genotype 2a virus) increased over 48 weeks of therapy. Development of HCV IRD was associated with elevated reactivity to JFH-1 before and during the first 12 weeks of therapy. Individual analyses of HCV IRD and non-HCV IRD patients revealed a lack of an association between nAb responses and HCV viral loads. These results showed that increased HCV-specific antibody levels during therapy were associated with CD4(+) T-cell recovery. Whilst genotype cross-reactive antibody responses may identify co-infected patients at risk of developing HCV IRD, neutralising antibodies to JFH-1 were not involved in suppression of HCV replication during therapy.

Hepatitis C virus (HCV)-specific memory B-cell responses in transiently and chronically infected HIV positive individuals

BACKGROUND

Antibody responses to hepatitis C virus (HCV) occur delayed and overly decline after viral clearance indicating that the B-cell response to HCV is abnormal. Virus-specific memory B-cells have recently been found in infected individuals, but the viral exposure requirements for the generation of these cells is unknown.

OBJECTIVES

The primary goal of this study was to quantify and compare the HCV-specific memory B-cell response between chronic and resolved HCV-infected individuals. A secondary goal was to examine if HIV-specific memory B-cell responses are maintained during HCV co-infection.

STUDY DESIGN

HCV core protein- and HIV-specific memory B-cell responses were examined in HIV/HCV-infected individuals treated 4-30 weeks after HCV diagnosis. Memory B-cell frequencies were compared between chronically and transiently infected individuals.

RESULTS

Chronically infected individuals had vigorous HCV-specific memory B-cell responses and antibodies, whereas subjects with transient viremia showed low or undetectable virus-specific B-cell responses. In addition, chronically HIV/HCV-infected subjects had robust HIV-specific memory B-cell responses.

CONCLUSIONS

Whereas chronic HCV infection induces virus-specific antibodies and memory B-cells, transient infection in individuals with sustained viral response to therapy does not stimulate a durable HCV-specific B-cell response indicating that the formation of long-lived virus-specific B-cells is suppressed in the early phase of infection. This may contribute to the inability to spontaneously clear HCV infection.

B cell responses to HIV antigen are a potent correlate of viremia in HIV-1 infection and improve with PD-1 blockade

Infection with Human Immunodeficiency Virus Type 1 (HIV-1) induces defects of both cellular and humoral immune responses. Impaired CD4+ T cell help and B cell dysfunction may partially explain the low frequency of broadly neutralizing antibodies in HIV-infected individuals. To understand the extent of B cell dysfunction during HIV infection, we assessed the level of B cell activation at baseline and after stimulation with a variety of antigens. Increased levels of viremia were associated with higher baseline expression of the activation marker CD86 on B cells and with decreased ability of B cells to increase expression of CD86 after in vitro stimulation with inactivated HIV-1. In a series of cell isolation experiments B cell responses to antigen were enhanced in the presence of autologous CD4+ T cells. HIV infected individuals had a higher frequency of PD-1 expression on B cells compared to HIV- subjects and PD-1 blockade improved B cell responsiveness to HIV antigen, suggesting that inhibitory molecule expression during HIV-1 infection may contribute to some of the observed B cell defects. Our findings demonstrate that during chronic HIV infection, B cells are activated and lose full capacity to respond to antigen, but suppression of inhibitory pressures as well as a robust CD4+ T cell response may help preserve B cell function.

Expansion of antibody secreting cells and modulation of neutralizing antibody activity in HIV infected individuals undergoing structured treatment interruptions

Background

HIV-1 infection generates numerous abnormalities in the B cell compartment which can be partly reversed by antiretroviral therapy. Our aim was to evaluate the effects that re-exposure to HIV antigens might have on the frequency and functionality of antibody secreting cells (ASC) in patients undergoing structured treatment interruptions (STI). As re-exposure to viral antigens may also boost the production of (neutralizing) antibodies, we also assessed the neutralizing activities during STI cycles.

Methods

Retrospective study of 10 patients undergoing 3 cycles of STI with 2 weeks on and 4 weeks off HAART. ASC frequencies were determined by flow cytometry in samples obtained at the beginning and the end of STI. Neutralization capacity, total IgG concentration and anti-gp120-IgG titres were evaluated.

Results

As expected, median viral loads were higher at the end of STI compared to on-HAART time points. The level of CD27 and CD38 expressing ACS followed the same pattern; with ASC being elevated up to 16 fold in some patients (median increase of 3.5% ± 4.13). Eight out of 10 patients maintained stable total IgG levels during the study. After purifying IgG fractions from plasma, HIV-neutralizing activity was observed in the two subjects with highest anti-gp120 titers. In one of these patients the neutralizing activity remained constant while the other showed elevated neutralizing Ab after first STI and once treatment was reinitiated after the 2^nd STI.

Conclusions

Our data suggest that STI and its associated transient increases in viral load drive the frequencies of ASC in an antigen-specific manner. In some subjects, this re-exposure to autologous virus boosts the presence of neutralizing antibodies, similar to what is seen after influenza vaccination. STI may not boost clinically beneficial nAb levels but offers opportunities to isolate nAb producing cells at considerably higher levels than in subjects with completely suppressed viral replication.

Hepatitis B specific T cell immunity induced by primary vaccination persists independently of the protective serum antibody level

In 2005, in accordance with recommendations made by the European Medicines Agency, the Italian Drug Agency ordered withdrawal of the hexavalent Hexavac(®) vaccine (Sanofi Pasteur MSD) from the market. Concerns had been raised about the low immunogenicity of the hepatitis B virus component of the vaccine, assessed by measurement of serum antibody levels, and its potential consequences on long-term protection against hepatitis B infection. We evaluated memory T cell response to establish whether there are differences in the protective mechanisms among children who had received either Hexavac(®) or Infanrix-hexa(®) (GlaxoSmithKline) as their primary vaccination. Immunological memory was determined by measuring the ability of T cells to proliferate and secrete IFNγ by ELISA and intracellular cytokines (IFNγ and IL-2) when cultured with hepatitis B surface antigen (HBsAg). The different memory subsets of T cells were also measured. The results indicate that, although they generate different serum antibody levels, both vaccines are efficient in generating T recall responses in vitro five years after the primary vaccination. The less immunogenic Hexavac(®) vaccine induces a strong T antigen response, as indicated by increased blast proliferation and the enhanced presence of memory subsets after HBsAg recall stimulation. These findings suggest that cellular immune response should be considered alongside serological markers as a surrogate of protection.

Expansion of HIV-specific T follicular helper cells in chronic HIV infection

HIV targets CD4 T cells, which are required for the induction of high-affinity antibody responses and the formation of long-lived B cell memory. The depletion of antigen-specific CD4 T cells during HIV infection is therefore believed to impede the development of protective B cell immunity. Although several different HIV-related B cell dysfunctions have been described, the role of CD4 T follicular helper (TFH) cells in HIV infection remains unknown. Here, we assessed HIV-specific TFH responses in the lymph nodes of treatment-naive and antiretroviral-treated HIV-infected individuals. Strikingly, both the bulk TFH and HIV-specific TFH cell populations were significantly expanded in chronic HIV infection and were highly associated with viremia. In particular, GAG-specific TFH cells were detected at significantly higher levels in the lymph nodes compared with those of GP120-specific TFH cells and showed preferential secretion of the helper cytokine IL-21. In addition, TFH cell expansion was associated with an increase of germinal center B cells and plasma cells as well as IgG1 hypersecretion. Thus, our study suggests that high levels of HIV viremia drive the expansion of TFH cells, which in turn leads to perturbations of B cell differentiation, resulting in dysregulated antibody production.

Epstein-Barr virus genome load is increased by therapeutic vaccination in HIV-l carriers, and further enhanced in patients with a history of symptomatic primary infection

OBJECTIVE

Epstein-Barr virus (EBV) infection is an established risk factor for B-cell lymphomas in Human Immunodeficiency virus (HIV)-1 infected patients. A disturbed EBV-host relationship is seen in patient groups with a high risk for EBV-associated lymphomas. We have analysed this relationship by measuring EBV-DNA in the blood of HIV-1 carriers.

METHOD

EBV-DNA load in B-cells was monitored by PCR in non- or insufficiently antiretroviral treated and rgp160-vaccinated HIV-patients.

RESULTS

Both asymptomatic HIV-infected and AIDS-patients showed a 25-40-fold increase in the number of B cell associated EBV-DNA copies compared to healthy controls. Patients included in a vaccine trial with recombinant HIV gp160 showed a 5-fold increase of EBV load compared to non-immunised patients and a 50-fold increase compared to healthy controls. There was no difference whether they received vaccine or "placebo". Vaccinated patients with a history of symptomatic primary HIV-1 infection (PHI) had a 280-fold increase in median EBV load compared to healthy controls, thus suggesting a synergistic effect between the vaccination and PHI, which hypothetically could affect lymphoma risk.

CONCLUSIONS

We recommend analysis of EBV-load and long term follow up of lymphoma risk in all therapeutic HIV-1 vaccination trials.

How can HIV-type-1-Env immunogenicity be improved to facilitate antibody-based vaccine development?

No vaccine candidate has induced antibodies (Abs) that efficiently neutralize multiple primary isolates of HIV-1. Preexisting high titers of neutralizing antibodies (NAbs) are essential, because the virus establishes infection before anamnestic responses could take effect. HIV-1 infection elicits Abs against Env, Gag, and other viral proteins, but of these only a subset of the anti-Env Abs can neutralize the virus. Whereas the corresponding proteins from other viruses form the basis of successful vaccines, multiple large doses of HIV-1 Env elicit low, transient titers of Abs that are not protective in humans. The inaccessibility of neutralization epitopes hinders NAb induction, but Env may also subvert the immune response by interacting with receptors on T cells, B cells, monocytes, macrophages, and dendritic cells. Here, we discuss evidence from immunizations of different species with various modified Env constructs. We also suggest how the divergent Ab responses to Gag and Env during infection may reflect differences in B cell regulation. Drawing on these analyses, we outline strategies for improving Env as a component of a vaccine aimed at inducing strong and sustained NAb responses.

Potent intratype neutralizing activity distinguishes human immunodeficiency virus type 2 (HIV-2) from HIV-1

HIV-2 has a lower pathogenicity and transmission rate than HIV-1. Neutralizing antibodies could be contributing to these observations. Here we explored side by side the potency and breadth of intratype and intertype neutralizing activity (NAc) in plasma of 20 HIV-1-, 20 HIV-2-, and 11 dually HIV-1/2 (HIV-D)-seropositive individuals from Guinea-Bissau, West Africa. Panels of primary isolates, five HIV-1 and five HIV-2 isolates, were tested in a plaque reduction assay using U87.CD4-CCR5 cells as targets. Intratype NAc in HIV-2 plasma was found to be considerably more potent and also broader than intratype NAc in HIV-1 plasma. This indicates that HIV-2-infected individuals display potent type-specific neutralizing antibodies, whereas such strong type-specific antibodies are absent in HIV-1 infection. Furthermore, the potency of intratype NAc was positively associated with the viral load of HIV-1 but not HIV-2, suggesting that NAc in HIV-1 infection is more antigen stimulation dependent than in HIV-2 infection, where plasma viral loads typically are at least 10-fold lower than in HIV-1 infection. Intertype NAc of both HIV-1 and HIV-2 infections was, instead, of low potency. HIV-D subjects had NAc to HIV-2 with similar high potency as singly HIV-2-infected individuals, whereas neutralization of HIV-1 remained poor, indicating that the difference in NAc between HIV-1 and HIV-2 infections depends on the virus itself. We suggest that immunogenicity and/or antigenicity, meaning the neutralization phenotype, of HIV-2 is distinct from that of HIV-1 and that HIV-2 may display structures that favor triggering of potent neutralizing antibody responses.

Alterations of the B-cell response by HIV-1 replication

While the hallmark of HIV-1 infection is the progressive depletion of CD4(+) T cells, extensive B-cell dysfunction ensues that impairs the quality of the humoral response. HIV-1 infection causes hypergammaglobulinemia, polyclonal activation, loss of memory B-cell subsets, B-cell exhaustion, aberrant B-cell surface markers, and impaired humoral responses against infections and vaccinations. The totality of the mechanisms that contribute to B-cell dysfunction in vivo is unknown, although roles for HIV proteins (Env, Tat, and Nef) and virions binding to CD21 on B cells have been identified. Recent studies suggest that early antiretroviral therapy, that minimizes virus replication, can profoundly preserve the early B-cell response to HIV-1. Thus, it is clear that there is an intricate interplay between HIV replication and stimulation of the host B-cell response to infection. A better understanding of how HIV-1 subverts a productive B-cell response is needed to inform vaccine strategies that aim to elicit long-lived plasma cells and memory B-cell responses that can act quickly upon antigen stimulation.

B cell responses to HIV-1 infection and vaccination: pathways to preventing infection

The B cell arm of the immune response becomes activated soon after HIV-1 transmission, yet the initial antibody response does not control HIV-1 replication, and it takes months for neutralizing antibodies to develop against the autologous virus. Antibodies that can be broadly protective are made only in a minority of subjects and take years to develop--too late to affect the course of disease. New studies of the earliest stages of HIV-1 infection, new techniques to probe the human B cell repertoire, the modest degree of efficacy in a vaccine trial and new studies of human monoclonal antibodies that represent the types of immune responses an HIV-1 vaccine should induce are collectively illuminating paths that a successful HIV-1 vaccine might take.

B cells in early and chronic HIV infection: evidence for preservation of immune function associated with early initiation of antiretroviral therapy

Characterization of lymphocytes including B cells during early versus chronic HIV infection is important for understanding the impact of chronic viremia on immune cell function. In this setting, we investigated B cells before and after reduction of HIV plasma viremia by antiretroviral therapy (ART). At baseline, peripheral blood B-cell counts were significantly lower in both early and chronic HIV-infected individuals compared with uninfected controls. Similar to CD4(+) but not CD8(+) T cells, B-cell numbers in both groups increased significantly after ART. At baseline, B cells of early HIV-infected individuals were composed of a higher percentage of plasmablasts and resting memory B cells compared with chronic HIV-infected individuals whose B cells were composed of a higher percentage of immature/transitional and exhausted B cells compared with their early infection counterparts. At 1 year after ART, the percentage of resting memory B cells remained higher in early compared with chronic HIV-infected individuals. This difference translated into a better functional profile in that memory B-cell responses to HIV and non-HIV antigens were superior in early- compared with chronic-treated HIV infected individuals. These findings provide new insights on B cells in HIV infection and how early initiation of ART may prevent irreversible immune system damage.