HIV-1 antigen-specific and -nonspecific B cell responses are sensitive to combination antiretroviral therapy

Strategies for HIV-1 vaccines that induce broadly neutralizing antibodies

After nearly four decades of research, a safe and effective HIV-1 vaccine remains elusive. There are many reasons why the development of a potent and durable HIV-1 vaccine is challenging, including the extraordinary genetic diversity of HIV-1 and its complex mechanisms of immune evasion. HIV-1 envelope glycoproteins are poorly recognized by the immune system, which means that potent broadly neutralizing antibodies (bnAbs) are only infrequently induced in the setting of HIV-1 infection or through vaccination. Thus, the biology of HIV-1-host interactions necessitates novel strategies for vaccine development to be designed to activate and expand rare bnAb-producing B cell lineages and to select for the acquisition of critical improbable bnAb mutations. Here we discuss strategies for the induction of potent and broad HIV-1 bnAbs and outline the steps that may be necessary for ultimate success.

Anti-CD4 autoantibodies in immunological non-responder people living with HIV: Cause of CD4+ T-cell depletion?

OBJECTIVE

We aimed to evaluate the anti-CD4 IgG role in the poor immune recovery of immunological nonresponder people with HIV (INR).

DESIGN

INR display low CD4+ T-cell increase despite long-term undetectable viremia. Among other factors, autologous anti-CD4 IgG-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells has been proposed to cause CD4+ T-cell depletion.

METHODS

Plasma anti-CD4 IgG levels were quantified and purified by chromatography columns for the subsequent use in a coculture of CD4+ T and NK cells. We analyzed NK cell degranulation markers (CD107a, perforin and granzyme B) and IFN-γ release, and CD4+ T-cell death. Binding affinity of anti-CD4 IgG for CD4+ T cells was also assessed.

RESULTS

A total of 168 individuals were enrolled (INR, 56; immunological responders, 40; treatment-naive, 39; and healthy controls, 33). The highest anti-CD4 IgG levels were found in treatment-naive PWH, followed by participants on treatment. There were no correlations between anti-CD4 IgG levels and CD4+ T-cell counts. In a 15-participant subgroup (naive, immunological responders, and INR), anti-CD4 IgG induced a slight NK-cell expression of degranulation markers and IFN-γ; however, the percentage of CD4+ T-cell death was negligible. Consistently, no significant changes in NK cell polyfunctionality were observed. In addition, purified anti-CD4 IgG showed scarce binding affinity for CD4+ T cells. These results were similar in all analyzed participant groups.

CONCLUSION

Our results suggest that autologous anti-CD4 IgG neither trigger CD4+ T-cell death by ADCC nor are responsible for CD4+ lymphocyte depletion in INR.

VIDEO ABSTRACT

http://links.lww.com/QAD/C518.

Impact of Chronic HIV Infection on SARS-CoV-2 Infection, COVID-19 Disease and Vaccines

Purpose of Review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has developed into a global pandemic that affect the health of hundreds of millions worldwide. In particular, SARS-CoV-2 infection in people with chronic human immune deficiency virus (HIV) infection is of concern, due to their already immunocompromised status. Yet, whether and how the immunological changes brought about by HIV will affect the immune responses against SARS-CoV-2 acute infection and impact the effectiveness of vaccines remain unclear. We discuss the intersection of COVID-19 in HIV-infected individuals.

Recent Findings

People living with HIV (PLWH) may be at increased risk of severe SARS-CoV-2 mediated disease complication due to functional impairment of the immune system and persistent inflammation, which can be ameliorated by antiretroviral therapy. Importantly, limited data suggest that current approved vaccines may be safe and efficacious in PLWH.

Summary

To address remaining questions and supplement limited experimental evidence, more studies examining the interplay between HIV and SARS-CoV-2 through their impact on the host immune system are required.

Clinical and Molecular Properties of Human Immunodeficiency Virus-Related Diffuse Large B-Cell Lymphoma

Non-Hodgkin lymphoma is the most common malignancy affecting people living with HIV (PLWH). Among its several subtypes, diffuse large B-cell lymphoma (DLBCL) is an important manifestation within the HIV-infected compartment of the population. Since HIV is able to modulate B cells and promote lymphomagenesis through direct and indirect mechanisms, HIV-related DLBCL has specific characteristics. In this review, we address the clinical and molecular properties of DLBCL disease in the context of HIV infection, as well as the mechanisms by which HIV is able to modulate B lymphocytes and induce their transformation into lymphoma.

Mouse APOBEC3 Restriction of Retroviruses

Apolipoprotein B mRNA editing enzyme, catalytic peptide 3 (APOBEC3) proteins are critical host proteins that counteract and prevent the replication of retroviruses. Unlike the genome of humans and other species, the mouse genome encodes a single Apobec3 gene, which has undergone positive selection, as reflected by the allelic variants found in different inbred mouse strains. This positive selection was likely due to infection by various mouse retroviruses, which have persisted in their hosts for millions of years. While mouse retroviruses are inhibited by APOBEC3, they nonetheless still remain infectious, likely due to the actions of different viral proteins that counteract this host factor. The study of viruses in their natural hosts provides important insight into their co-evolution.

Mining for humoral correlates of HIV control and latent reservoir size

While antiretroviral therapy (ART) has effectively revolutionized HIV care, the virus is never fully eliminated. Instead, immune dysfunction, driven by persistent non-specific immune activation, ensues and progressively leads to premature immunologic aging. Current biomarkers monitoring immunologic changes encompass generic inflammatory biomarkers, that may also change with other infections or disease states, precluding the antigen-specific monitoring of HIV-infection associated changes in disease. Given our growing appreciation of the significant changes in qualitative and quantitative properties of disease-specific antibodies in HIV infection, we used a systems approach to explore humoral profiles associated with HIV control. We found that HIV-specific antibody profiles diverge by spontaneous control of HIV, treatment status, viral load and reservoir size. Specifically, HIV-specific antibody profiles representative of changes in viral load were largely quantitative, reflected by differential HIV-specific antibody levels and Fc-receptor binding. Conversely, HIV-specific antibody features that tracked with reservoir size exhibited a combination of quantitative and qualitative changes marked by more distinct subclass selection profiles and unique HIV-specific Fc-glycans. Our analyses suggest that HIV-specific antibody Fc-profiles provide antigen-specific resolution on both cell free and cell-associated viral loads, pointing to potentially novel biomarkers to monitor reservoir activity.

Current combination antiretroviral therapy (ART) regimens have reversed the death sentence once associated with an HIV diagnosis. However, the virus is never fully eliminated. Rather, latently infected cells with integrated virus (latent reservoir) persist and the virus rebounds rapidly upon discontinuation of therapy. Further, even for those on ART, immune dysfunction, driven by persistent non-specific immune activation, ensues and progressively leads to premature immunologic aging. Current biomarkers monitoring these changes are non-specific–they focus on generic inflammatory changes that may also track with other infections or disease states. In this manuscript, we used an unbiased analytical systems approach to identify antigen-specific biomarkers of HIV disease state/treatment status, active viremia and the latent reservoir. By virtue of them being antigen-specific, these are robust context-specific biomarkers of HIV disease progression, viremia and reservoir size. Our framework highlights the strength of using systems approaches in identifying humoral biomarkers, and can be used in other contexts to identify antigen-specific correlates of infectious disease outcome.

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.

Nodular pulmonary deposition disease in a patient with the acquired immunodeficiency syndrome: a case report

Background

Pulmonary nodules are a common cause for concern in patients with human immunodeficiency virus and acquired immunodeficiency syndrome. Most commonly, they are the result of an infection, given the patients’ immunocompromised state; however, in some cases, pulmonary nodules in patients with human immunodeficiency virus and patients with acquired immunodeficiency syndrome can result from cellular or protein deposits. We report a rare case of nodular pulmonary light chain deposition disease in a patient with acquired immunodeficiency syndrome and monoclonal gammopathy of undetermined significance.

Case presentation

A 53-year-old African American woman with acquired immunodeficiency syndrome had pulmonary nodules detected incidentally by imaging of her lungs. Pulmonary tuberculosis was high on the differential diagnosis, but she had a negative test result for pulmonary tuberculosis. Imaging also revealed multiple lucent bone lesions, and earlier in the year, serum protein electrophoresis had shown an immunoglobulin G-kappa monoclonal protein (M spike). She was mildly anemic, so there was concern for progression to myeloma; however, the result of her bone marrow biopsy was unremarkable. Lung biopsy revealed finely granular eosinophilic material with negative Congo red staining, consistent with light chain deposition disease.

Conclusions

The extent of this patient’s light chain deposition disease was thought to be caused by a combination of acquired immunodeficiency syndrome and monoclonal gammopathy of undetermined significance, and the interval decrease in lung nodule size after restarting antiretroviral therapy confirms this hypothesis and also highlights a potentially unique contribution of the hypergammaglobulinemia to this disease process in patients with human immunodeficiency virus and patients with acquired immunodeficiency syndrome .

Reduction of anti-HIV antibody responses in subjects receiving antiretroviral therapy during chronic HIV-1 infection

OBJECTIVE

Antiretroviral therapy (ART) can lead to a decline or absence of anti-HIV antibodies in HIV-infected children or acutely HIV-infected (AHI) subjects. However, the characteristics of anti-HIV antibody response in the subjects who are treated during chronic HIV-1 infection (CHI) have not yet been fully investigated.

METHODS

Different anti-HIV antibodies were longitudinally quantified and analyzed in 81 CHI adults under ART. The factors associated with antibody decline were evaluated by binary logistic regression analysis.

RESULTS

ART led to 36.0% (27/75) and 52.1% (38/73) of the patients whose anti-HIV levels reduced by more than 75% of the baseline levels at 12 and 24 months post-ART, respectively. The reduction of anti-HIV antibodies correlated with the decline of HIV-1 viral load with correlation coefficients in the range 0.556-0.848 or R2 value of 0.576-0.873 (P < 0.001). However, no negative detection of anti-HIV antibody was observed at 24 months post-ART. The time from HIV-1 diagnosis to ART initiation and the baseline anti-HIV levels were the key factors associated with quick decline of anti-HIV antibodies during ART.

CONCLUSIONS

ART-induced kinetics of anti-HIV antibody response was different among the subjects with AHI and CHI. Misdiagnosis of HIV-1 infection may not be a serious issue in HIV-1 chronically infected subjects under ART, and could ideally be avoided by using multiple HIV-1 antigens for screening purposes.

Acquired hypogammaglobulinemia and pathogen-specific antibody depletion after solid organ transplantation in human immunodeficiency virus infection: A brief report

Hypogammaglobulinemia (HGG) frequently occurs in recipients after types of (SOT). The incidence and significance of HGG in HIV+ recipients of SOT are just being explored. We reported that 12% of the recipients in the SOT in multi-center HIV-TR (HIV-TR) Study developed moderate or severe HGG at 1 year. In LT recipients, this was associated with serious infections and death. We have now further characterized the decreased antibodies in HIV+ SOT recipients who developed HGG. We measured the levels of pathogen-specific antibodies and poly-specific self-reactive antibodies (PSA) in relation to total IgG levels from serial serum samples for 20 HIV+ SOT recipients who developed moderate to severe HGG following SOT. Serum antibody levels to measles, tetanus toxoid, and HIV-1 were determined by EIA. Levels of PSAs were determined by incubating control lymphocytes with patient serum, staining with anti-human IgG Fab-FITC, and analysis by flow cytometry. Levels of PSA were higher compared to healthy, HIV-uninfected controls at pre-transplant baseline and increased by weeks 12 and 26, but the changes were not significant. Likewise, anti-HIV antibody levels remained unchanged over time. In contrast, antibody levels against measles and tetanus were significantly reduced from baseline by week 12, and did not return to baseline, even after 2 years. For HIV patients who develop moderate to severe HGG after transplant, the reduction in IgG levels is associated with a significant decrease in pathogen-specific antibody titers, while PSA levels and anti-HIV antibodies are unchanged. This may contribute to infectious complications and other clinical endpoints.

Boosting of Markers of Fcγ Receptor Function in Anti-HIV Antibodies During Structured Treatment Interruption

Anti-HIV envelope (Env) antibodies elicit important Fc receptor functions, including FcγRIIIa-mediated natural killer cell killing of opsonized infected targets. How these antibodies evolve during HIV infection and treatment remains poorly understood. We describe changes in anti-HIV Env IgG using longitudinal samples from seroconverter subjects treated soon after infection and later during periods of structured treatment interruption (STI). Our well-validated dimeric rsFcγR binding assays combine effects of opsonizing antibody subclasses, epitopes, and geometries to provide a measure of FcγR (Fcγ receptor)-mediated functionality. IgG1 anti-Env titers diminished rapidly during antiretroviral therapy (ART; t_1/2 3.0 ± 0.8 months), while the dimeric rsFcγRIIIa activity persisted longer (t_1/2 33 ± 11 months), suggesting that there is maintenance of functional antibody specificities within the diminished pool of anti-HIV Env Abs. The initial antibody response to infection in two subjects was characterized by approximately fivefold higher FcγRIIIa compared with FcγRIIa binding activity. Uncoupling of FcγRIIa and FcγRIIIa activities may be a distinct feature of the early antibody response that preferentially engages FcγRIIIa-mediated effector functions. Two to three STI cycles, even with low viremia, were sufficient to boost dimeric FcγR activity in these seroconverter subjects. We hypothesize that increased humoral immunity induced by STI is a desirable functional outcome potentially achievable by therapeutic immunization during ART. We conclude that controlled viral antigen exposure under the protection of suppressive ART may be effective in eliciting FcγR-dependent function in support of viral reactivation and kill strategies.

Mucosal T follicular helper cells in SIV-infected rhesus macaques: contributing role of IL-27

Mesenteric lymph nodes (MLNs), that drain the large and small intestine, are critical sites for the induction of oral tolerance. Although depletion of CD4 T cells in the intestinal lamina propria is a hallmark of HIV infection, CD4 T cell dynamics in MLNs is less known due to the lack of accessibility to these LNs. We demonstrate the early loss of memory CD4 T cells, including T follicular helper cells (Tfh) and a remodeling of MLN architecture in SIV-infected rhesus macaques (RMs). Along with the loss of Tfh cells, we observe the loss of memory B cells and of germinal center B cells. Tfh cells display a Th1 profile with increased levels of the transcription factors that negatively impact on Tfh differentiation and of Stat5 phosphorylation. MLNs of SIV-infected RMs display lower mRNA transcripts encoding for IL-12, IL-23, and IL-35, whereas those coding for IL-27 are not impaired in MLNs. In vitro, IL-27 negatively impacts on Tfh cells and recapitulates the profile observed in SIV-infected RMs. Therefore, early defects of memory CD4 T cells, as well of Tfh cells in MLNs, which play a central role in regulating the mucosal immune response, may have major implications for Aids.

Delayed Seroreversion in HIV-exposed Uninfected Infants

BACKGROUND

Recent studies report delayed anti-HIV antibody clearance (seroreversion) among HIV-exposed uninfected infants that may affect diagnostic practices. We evaluated the age-specific seroreversion rates in Thailand.

METHODS

The medical records of HIV-exposed uninfected infants born in January 2000-December 2014 were reviewed. Anti-HIV seroreversion rates at 12, 18 and 24 months were analyzed in 3 periods according to the Thai National Guidelines of prevention of mother-to-child transmission of HIV: zidovudine with or without single dose nevirapine to all women (2000-2006), adding lamivudine plus nevirapine to zidovudine in women with CD4 count <200 cells/mm (2007-2009) and zidovudine plus lamivudine plus boosted lopinavir to all women (2010-2014). In 2013, the serologic test kit was changed from third- to fourth-generation (4G) assay. All the infants were formula fed.

RESULTS

Among 736 infants, the overall seroreversion rates at 12, 18 and 24 months of age were 59.38%, 94.57% and 100%, respectively. The seroreversion rates at 12 months of age declined from 68% in 2000-2006 and 65.9% in 2007-2009, to 42.9% in 2010-2014 (P = 0.001). Seroreversion rates at 18 months of age were more than 96.5% before 2013 and decreased to 79.1% in 2013-2014 (P = 0.001) with use of 4G. Multivariate analysis identified antepartum protease inhibitors treatment and the use of 4G testing as independent factors associated with delayed seroreversion.

CONCLUSIONS

Anti-HIV seroreversion delay in HIV-exposed uninfected infants was associated with use of protease inhibitors and 4G HIV testing, complicating the interpretation to exclude perinatal HIV infection.

The contribution of immune activation and accelerated aging in multiple myeloma occurring in HIV-infected population

: The widespread use of antiretroviral treatment results in a significant improvement in immunological condition of people living with HIV (PLWH) who nevertheless experience a significantly increased risk to develop non-Hodgkin lymphoma compared with the general population. Despite many literature observations regarding multiple myeloma in PLWH, a consensus on its relevance in HIV infection does not exist. A number of large population studies on multiple myeloma in PLWH gave contrasting results, fluctuating from increased standardized incidence ratios to the lack of observed cases of multiple myeloma. Use of antiretroviral treatment, in this context, seems to induce a slight reduction of standardized incidence ratio, although with a partial effect, especially in young patients. However, a high variability in clinical onset has been described in different reports: the only common feature of multiple myeloma in PLWH is an atypical presentation as compared with general population, with a worse prognosis in case of uncontrolled HIV infection. We identified three pathogenetic steps in the complex scenario of multiple myeloma in PLWH: first, antigenic trigger; second, persistent T cell deficiency/dysfunction; third, altered regulation of B cells. All these pathogenetic steps play a role in immunological dysregulation, leading to B cell abnormalities and hyperactivation and, finally, resulting in the development of lymphoid malignancies. HIV has a role in each one of these three steps, due to its ability to trigger and dysregulate immune system. We hypothesize that HIV could be closely implicated in the multiple myeloma development in PLWH by accelerating the carcinogenesis events in a complex and only partially understood early aging process.

The Immune Response to Mycobacterium tuberculosis in HIV-1-Coinfected Persons

Globally, about 36.7 million people were living with HIV infection at the end of 2015. The most frequent infection co-occurring with HIV-1 is Mycobacterium tuberculosis-374,000 deaths per annum are attributable to HIV-tuberculosis, 75% of those occurring in Africa. HIV-1 infection increases the risk of tuberculosis by a factor of up to 26 and alters its clinical presentation, complicates diagnosis and treatment, and worsens outcome. Although HIV-1-induced depletion of CD4⁺ T cells underlies all these effects, more widespread immune deficits also contribute to susceptibility and pathogenesis. These defects present a challenge to understand and ameliorate, but also an opportunity to learn and optimize mechanisms that normally protect people against tuberculosis. The most effective means to prevent and ameliorate tuberculosis in HIV-1-infected people is antiretroviral therapy, but this may be complicated by pathological immune deterioration that in turn requires more effective host-directed anti-inflammatory therapies to be derived.

Immunization with Clinical HIV-1 Env Proteins Induces Broad Antibody Dependent Cellular Cytotoxicity-Mediating Antibodies in a Rabbit Vaccination Model

The induction of both neutralizing antibodies and non-neutralizing antibodies with effector functions, for example, antibody-dependent cellular cytotoxicity (ADCC), is desired in the search for effective vaccines against HIV-1. In the pursuit of novel immunogens capable of inducing an efficient antibody response, rabbits were immunized with selected antigens using different prime-boost strategies. We immunized 35 different groups of rabbits with Env antigens from clinical HIV-1 subtypes A and B, including immunization with DNA alone, protein alone, and DNA prime with protein boost. The rabbit sera were screened for ADCC activity using a GranToxiLux-based assay with human peripheral blood mononuclear cells as effector cells and CEM.NKR_CCR5 cells coated with HIV-1 envelope as target cells. The groups with the highest ADCC activity were further characterized for cross-reactivity between HIV-1 subtypes. The immunogen inducing the most potent and broadest ADCC response was a trimeric gp140. The ADCC activity was highest against the HIV-1 subtype corresponding to the immunogen. The ADCC activity did not necessarily reflect neutralizing activity in the pseudovirus-TZMbl assay, but there was an overall correlation between the two antiviral activities. We present a rabbit vaccination model and an assay suitable for screening HIV-1 vaccine candidates for the induction of ADCC-mediating antibodies in addition to neutralizing antibodies. The antigens and/or immunization strategies capable of inducing antibodies with ADCC activity did not necessarily induce neutralizing activity and vice versa. Nevertheless, we identified vaccine candidates that were able to concurrently induce both types of responses and that had ADCC activity that was cross-reactive between different subtypes. When searching for an effective vaccine candidate, it is important to evaluate the antibody response using a model and an assay measuring the desired function.

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.

Pathogenic Correlates of Simian Immunodeficiency Virus-Associated B Cell Dysfunction

We compared and contrasted pathogenic (in pig-tailed macaques [PTMs]) and nonpathogenic (in African green monkeys [AGMs]) SIVsab infections to assess the significance of the B cell dysfunction observed in simian (SIV) and human immunodeficiency virus (HIV) infections. We report that the loss of B cells is specifically associated with the pathogenic SIV infection, while in the natural hosts, in which SIV is nonpathogenic, B cells rapidly increase in both lymph nodes (LNs) and intestine. SIV-associated B cell dysfunction associated with the pathogenic SIV infection is characterized by loss of naive B cells, loss of resting memory B cells due to their redistribution to the gut, increases of the activated B cells and circulating tissue-like memory B cells, and expansion of the B regulatory cells (Bregs). While circulating B cells are virtually restored to preinfection levels during the chronic pathogenic SIV infection, restoration is mainly due to an expansion of the "exhausted," virus-specific B cells, i.e., activated memory cells and tissue-like memory B cells. Despite of the B cell dysfunction, SIV-specific antibody (Ab) production was higher in the PTMs than in AGMs, with the caveat that rapid disease progression in PTMs was strongly associated with lack of anti-SIV Ab. Neutralization titers and the avidity and maturation of immune responses did not differ between pathogenic and nonpathogenic infections, with the exception of the conformational epitope recognition, which evolved from low to high conformations in the natural host. The patterns of humoral immune responses in the natural host are therefore more similar to those observed in HIV-infected subjects, suggesting that natural hosts may be more appropriate for modeling the immunization strategies aimed at preventing HIV disease progression. The numerous differences between the pathogenic and nonpathogenic infections with regard to dynamics of the memory B cell subsets point to their role in the pathogenesis of HIV/SIV infections and suggest that monitoring B cells may be a reliable approach for assessing disease progression.IMPORTANCE We report here that the HIV/SIV-associated B cell dysfunction (defined by loss of total and memory B cells, increased B regulatory cell [Breg] counts, and B cell activation and apoptosis) is specifically associated with pathogenic SIV infection and absent during the course of nonpathogenic SIV infection in natural nonhuman primate hosts. Alterations of the B cell population are not correlated with production of neutralizing antibodies, the levels of which are similar in the two species. Rapid progressive infections are associated with a severe impairment in SIV-specific antibody production. While we did not find major differences in avidity and maturation between the pathogenic and nonpathogenic SIV infections, we identified a major difference in conformational epitope recognition, with the nonpathogenic infection being characterized by an evolution from low to high conformations. B cell dysfunction should be considered in designing immunization strategies aimed at preventing HIV disease progression.

Serum glycan-binding IgG antibodies in HIV-1 infection and during the development of broadly neutralizing responses

BACKGROUND

The HIV-1 envelope is covered with glycans that provide structural integrity and protect conserved regions from host antibody responses. However, these glycans are often the target of broadly neutralizing antibodies (bNAbs) that emerge in some HIV-infected individuals. We aimed to determine whether antiglycan IgG antibodies are a general response to HIV-1 infection or specific to individuals who develop bNAbs.

METHODS

IgG binding to glycans was assessed using arrays that contained 245 unique components including N-linked carbohydrates, glycolipids, and Tn-peptides. Sera from 20 HIV-negative and 27 HIV-positive women (including 12 individuals who developed bNAbs) were profiled longitudinally. HIV-1 gp120 proteins were used to compete for binding to the array.

RESULTS

Antiglycan IgG antibodies fluctuated over a 3-year period, irrespective of HIV infection. However, HIV-positive individuals had elevated binding to 40 components on the array that included Man8, Man9, Tn-peptides, heat shock protein, and glycolipids. Competition experiments confirmed that a proportion of these glycan-binding IgG antibodies were HIV-1-specific, some of which were higher in individuals who developed bNAbs.

CONCLUSIONS

HIV-1 infection is associated with elevated levels of IgG antibodies to specific glycans. Furthermore, some antiglycan IgG antibodies were more abundant in individuals with bNAbs, suggesting a unique phenotype that may be informative for HIV vaccine design.

Effect of Combination Antiretroviral Therapy on HIV-1-specific Antibody-Dependent Cellular Cytotoxicity Responses in Subtype B- and Subtype C-Infected Cohorts

BACKGROUND

There is growing interest in immune therapies to clear the latent HIV-1 after combination antiretroviral therapy (cART). There is limited information on the effect of cART on antibody-dependent cellular cytotoxicity (ADCC), and no studies have directly compared ADCC in HIV-1 subtype B- and subtype C-infected subjects. The effect of improving immunocompetence on ADCC to influenza also remains unexplored.

METHODS

The effect of cART on HIV-1- and influenza-specific ADCC was analyzed in 2 cohorts (39 subtype B- and 47 subtype C-infected subjects) before and after 2 years of cART. ADCC analyses included an enzyme-linked immunosorbent assay-based dimeric recombinant soluble (rs) FcγRIIIa-binding assay, antibody-dependent natural killer cell activation assay, and ADCC-mediated killing assays.

RESULTS

HIV-1 subtype B and C Env-specific antibody binding to dimeric rsFcγRIIIa were reduced in subtypes B- and C-infected cohorts after 2 years of cART (both P < 0.05). Reduced ADCC-mediated killing of target cells expressing subtype B Env in the subtype B-infected cohort (P = 0.003) was observed after 96 weeks of cART, but not of subtype C Env in the subtype C-infected cohort. A greater reduction in ADCC was detected in subjects with baseline CD4 counts >300 cells/μL (P < 0.05). The resolving immunodeficiency after 96 weeks of cART resulted in improved HA-specific ADCC to 6 strains of influenza (all P < 0.01).

CONCLUSIONS

cART results in HIV-1 antigen loss and reductions in HIV-1 Env-specific antibodies with Fc functionality in both subtype B- and C-infected subjects, particularly in immunocompetent subjects. Simultaneously, cART improves ADCC to diverse strains of influenza, suggesting reduction in influenza disease after cART.

Cellular Architecture of Spinal Granulomas and the Immunological Response in Tuberculosis Patients Coinfected with HIV

Mycobacterium tuberculosis (M.tb) and HIV are individually responsible for the most deaths worldwide among all infectious agents, and coinfection with M.tb and HIV is a significant public health challenge in the developing world. Although the lung is the primary target organ for tuberculosis (TB), M.tb can also cause extrapulmonary tuberculosis (EPTB) such as in the bones and joints. Treatment of EPTB is much more challenging than treatment of pulmonary TB. The hallmark of the host immune response against TB is the formation of organized structures called granulomas that are infiltrated with immune cells and are rich in cytokines and chemokines. Inside granulomas, the host confines the M.tb bacteria to a particular region of the organ and avoids dispersion. In this study, we analyzed immune cells in bone granulomas of patients with EPTB that are also coinfected with HIV. We found that HIV-infected TB patients have dispersed bone granulomas, with reduced T cell numbers and a concomitant increase in plasma cells. Additionally, HIV-infected patients exhibited dramatically increased serum levels of IgM and IgG1 antibodies, which is indicative of T-cell-independent B-cell activation and mucosal T-cell activation, respectively. Interestingly, we also observed that CD29⁺ stem cells are increased in HIV-TB coinfection, suggesting a link with HIV infection. Therefore, our work provides new insights into the architecture of spinal TB granulomas and the role of B-cells and humoral immunity against a highly infectious intracellular pathogen. We propose that our findings will inform biomarker identification for EPTB and possibly the development of related therapeutics and/or vaccines to protect HIV-infected patients against disseminated TB.

Plasma CXCL13 but Not B Cell Frequencies in Acute HIV Infection Predicts Emergence of Cross-Neutralizing Antibodies

Immunological events in acute HIV-1 infection before peak viremia (hyperacute phase) may contribute to the development of broadly cross-neutralizing antibodies. Here, we used pre-infection and acute-infection peripheral blood mononuclear cells and plasma samples from 22 women, including 10 who initiated antiretroviral treatment in Fiebig stages I-V of acute infection to study B cell subsets and B-cell associated cytokines (BAFF and CXCL13) kinetics for up to ~90 days post detection of plasma viremia. Frequencies of B cell subsets were defined by flow cytometry while plasma cytokine levels were measured by ELISA. We observed a rapid but transient increase in exhausted tissue-like memory, activated memory, and plasmablast B cells accompanied by decline in resting memory cells in untreated, but not treated women. B cell subset frequencies in untreated women positively correlated with viral loads but did not predict emergence of cross-neutralizing antibodies measured 12 months post detection of plasma viremia. Plasma BAFF and CXCL13 levels increased only in untreated women, but their levels did not correlate with viral loads. Importantly, early CXCL13 but not BAFF levels predicted the later emergence of detectable cross-neutralizing antibodies at 12 months post detection of plasma viremia. Thus, hyperacute HIV-1 infection is associated with B cell subset changes, which do not predict emergence of cross-neutralizing antibodies. However, plasma CXCL13 levels during hyperacute infection predicted the subsequent emergence of cross-neutralizing antibodies, providing a potential biomarker for the evaluation of vaccines designed to elicit cross-neutralizing activity or for natural infection studies to explore mechanisms underlying development of neutralizing antibodies.

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.

Longitudinal dynamics of the HIV-specific B cell response during intermittent treatment of primary HIV infection

BACKGROUND

Neutralizing antibodies develop in natural HIV-1 infection. Their development often takes several years and may rely on chronic virus exposure. At the same time recent studies show that treatment early in infection may provide opportunities for immune preservation. However, it is unknown how intermittent treatment in early infection affects development of the humoral immune response over time. We investigate the effect of cART in early HIV infection on the properties of the memory B cell compartment following 6 months of cART or in the absence of treatment. The patients included participated in the Primo-SHM trial where patients with an early HIV-1 infection were randomized to no treatment or treatment for 24 or 60 weeks.

METHODS

Primo-SHM trial patients selected for the present study were untreated (n = 23) or treated for 24 weeks (n = 24). Here we investigate memory B cell properties at viral set-point and at a late time point (respectively median 54 and 73 weeks) before (re)-initiation of treatment.

RESULTS

At viral set-point, the memory B cell compartment in treated patients demonstrated significantly lower fractions of antigen-primed, activated, memory B cells (p = 0.006). In contrast to untreated patients, in treated patients the humoral HIV-specific response reached a set point over time. At a transcriptional level, sets of genes that showed enhanced expression in memory B cells at viral setpoint in untreated patients, conversely showed rapid increase of expression of the same genes in treated patients at the late time point.

CONCLUSION

These data suggest that, although the memory B cell compartment is phenotypically preserved until viral setpoint after treatment interruption, the development of the HIV-specific antibody response may benefit from exposure to HIV. The effect of viral exposure on B cell properties is also reflected by longitudinal changes in transcriptional profile in memory B cells over time in early treated patients.

Enhanced FCGR2A and FCGR3A signaling by HIV viremic controller IgG

HIV-1 viremic controllers (VC) spontaneously control infection without antiretroviral treatment. Several studies indicate that IgG Abs from VCs induce enhanced responses from immune effector cells. Since signaling through Fc-γ receptors (FCGRs) modulate these Ab-driven responses, here we examine if enhanced FCGR activation is a common feature of IgG from VCs. Using an infected cell-based system, we observed that VC IgG stimulated greater FCGR2A and FCGR3A activation as compared with noncontrollers, independent of the magnitude of HIV-specific Ab binding or virus neutralization activities. Multivariate regression analysis showed that enhanced FCGR signaling was a significant predictor of VC status as compared with chronically infected patients (CIP) on highly active antiretroviral therapy (HAART). Unsupervised hierarchical clustering of patient IgG functions primarily grouped VC IgG profiles by enhanced FCGR2A, FCGR3A, or dual signaling activity. Our findings demonstrate that enhanced FCGR signaling is a common and significant predictive feature of VC IgG, with VCs displaying a distinct spectrum of FCGR activation profiles. Thus, profiling FCGR activation may provide a useful method for screening and distinguishing protective anti-HIV IgG responses in HIV-infected patients and in monitoring HIV vaccination regimens.

Partial HIV C2V3 envelope sequence analysis reveals association of coreceptor tropism, envelope glycosylation and viral genotypic variability among Kenyan patients on HAART

Background

HIV-1 is highly variable genetically and at protein level, a property it uses to subvert antiviral immunity and treatment. The aim of this study was to assess if HIV subtype differences were associated with variations in glycosylation patterns and co-receptor tropism among HAART patients experiencing different virologic treatment outcomes.

Methods

A total of 118 HIV env C2V3 sequence isolates generated previously from 59 Kenyan patients receiving highly active antiretroviral therapy (HAART) were examined for tropism and glycosylation patterns. For analysis of Potential N-linked glycosylation sites (PNGs), amino acid sequences generated by the NCBI’s Translate tool were applied to the HIVAlign and the N-glycosite tool within the Los Alamos Database. Viral tropism was assessed using Geno2Pheno (G2P), WebPSSM and Phenoseq platforms as well as using Raymond’s and Esbjörnsson’s rules. Chi square test was used to determine independent variables association and ANOVA applied on scale variables.

Results

At respective False Positive Rate (FPR) cut-offs of 5% (p = 0.045), 10% (p = 0.016) and 20% (p = 0.005) for CXCR4 usage within the Geno2Pheno platform, HIV-1 subtype and viral tropism were significantly associated in a chi square test. Raymond’s rule (p = 0.024) and WebPSSM (p = 0.05), but not Phenoseq or Esbjörnsson showed significant associations between subtype and tropism. Relative to other platforms used, Raymond’s and Esbjörnsson’s rules showed higher proportions of X4 variants, while WebPSSM resulted in lower proportions of X4 variants across subtypes. The mean glycosylation density differed significantly between subtypes at positions, N277 (p = 0.034), N296 (p = 0.036), N302 (p = 0.034) and N366 (p = 0.004), with HIV-1D most heavily glycosylated of the subtypes. R5 isolates had fewer PNGs than X4 isolates, but these differences were not significant except at position N262 (p = 0.040). Cell-associated isolates from virologic treatment success subjects were more glycosylated than cell-free isolates from virologic treatment failures both for the NXT (p = 0.016), and for all the patterns (p = 0.011).

Conclusion

These data reveal significant associations of HIV-1 subtype diversity, viral co-receptor tropism, viral suppression and envelope glycosylation. These associations have important implications for designing therapy and vaccines against HIV. Heavy glycosylation and preference for CXCR4 usage of HIV-1D may explain rapid disease progression in patients infected with these strains.

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.

Enhanced binding of antibodies generated during chronic HIV infection to mucus component MUC16

Transmission of HIV across mucosal barriers accounts for the majority of HIV infections worldwide. Thus, efforts aimed at enhancing protective immunity at these sites are a top priority, including increasing virus-specific antibodies (Abs) and antiviral activity at mucosal sites. Mucin proteins, including the largest cell-associated mucin, mucin 16 (MUC16), help form mucus to provide a physical barrier to incoming pathogens. Here, we describe a natural interaction between Abs and MUC16 that is enhanced in specific disease settings such as chronic HIV infection. Binding to MUC16 was independent of IgG subclass, but strongly associated with shorter Ab glycan profiles, with agalactosylated (G0) Abs demonstrating the highest binding to MUC16. Binding of Abs to epithelial cells was diminished following MUC16 knockdown, and the MUC16 N-linked glycans were critical for binding. Further, agalactosylated VRC01 captured HIV more efficiently in MUC16. These data point to a novel opportunity to enrich Abs at mucosal sites by targeting Abs to MUC16 through changes in Fc glycosylation, potentially blocking viral movement and sequestering the virus far from the epithelial border. Thus, next-generation vaccines or monoclonal therapeutics may enhance protective immunity by tuning Ab glycosylation to promote the enrichment of Abs at mucosal barriers.

B cells in HIV pathogenesis

PURPOSE OF REVIEW

The induction of a virus-clearing humoral immune response in natural HIV infection is impaired. Insights into early events in HIV infection that affect B-cell responses and antibody development are addressed and related to strategies for the design of an HIV vaccine.

RECENT FINDINGS

Broadly neutralizing antibody responses do not develop early in HIV-1 infection, and recent reports highlight the role of preexisting suboptimal B-cell populations that can dominate the early antibody response. Furthermore, from the earliest phases of infection, virus replication is a driving force behind alterations in the B cell and T-follicular helper cell (TFH) compartments. Paradoxically, the factors that drive these abnormalities, such as high virus load, duration of infection, and increased viral diversity, are likely necessary for the development of both TFH and broadly neutralizing antibodies.

SUMMARY

These data provide new insights into prerequisites for an effective HIV vaccine. First, a vaccine should induce specific B-cell lineages so that preexisting cross-reactivity is avoided and, additionally, it must mimic high levels of diverse antigen in the absence of chronic virus replication within immune cells to activate high levels of quality of TFH and stimulate antibody maturation.

B-cell development and pneumococcal immunity in vertically acquired HIV infection

OBJECTIVES

Many children with HIV infection now survive into adulthood. This study explored the impact of vertically acquired HIV in the era of antiretroviral therapy on the development of humoral immunity.

DESIGN

Natural and vaccine-related immunity to pneumococcus and B-cell phenotype was characterized and compared in three groups of young adults: those with vertically-acquired infection, those with horizontally acquired infection and healthy controls.

METHODS

Serotype-specific pneumococcal (Pnc) immunoglobulin M and G concentrations before and up to 1 year post-Pnc polysaccharide (Pneumovax) immunization were determined, and opsonophagocytic activity was analysed. B-cell subpopulations and dynamic markers of B-cell signalling, turnover and susceptibility to apoptosis were evaluated by flow cytometry.

RESULTS

HIV-infected patients showed impaired natural Pnc immunity and reduced humoral responses to immunization with Pneumovax; this was greatest in those viraemic at time of the study. Early-life viral control before the age of 10 years diminished these changes. Expanded populations of abnormally activated and immature B-cells were seen in both HIV-infected cohorts. Vertically infected patients were particularly vulnerable to reductions in marginal zone and switched memory populations. These aberrations were reduced in patients with early-life viral control.

CONCLUSION

In children with HIV, damage to B-cell memory populations and impaired natural and vaccine immunity to pneumococcus is evident in early adult life. Sustained viral control from early childhood may help to limit this effect and optimize humoral immunity in adult life.

Assessing immune aging in HIV-infected patients

Many of the alterations that affect innate and adaptive immune cell compartments in HIV-infected patients are reminiscent of the process of immune aging, characteristic of old age. These alterations define the immunological age of individuals and are likely to participate to the decline of immune competence with HIV disease progression. It is therefore important to characterize these changes, which point toward the accumulation of highly differentiated immunocompetent cells, associated with overall telomere length shortening, as well as understanding their etiology, especially related to the impact of chronic immune activation. Particular attention should be given to the exhaustion of primary immune resources, including haematopoietic progenitors and naïve cells, which holds the key for effective hematopoiesis and immune response induction, respectively. The alteration of these compartments during HIV infection certainly represents the foundation of the immune parallel with aging.

Antibody Responses After Analytic Treatment Interruption in Human Immunodeficiency Virus-1-Infected Individuals on Early Initiated Antiretroviral Therapy

The examination of antibody responses in human immunodeficiency virus (HIV)-1-infected individuals in the setting of antiretroviral treatment (ART) interruption can provide insight into the evolution of antibody responses during viral rebound. In this study, we assessed antibody responses in 20 subjects in AIDS Clinical Trials Group A5187, wherein subjects were treated with antiretroviral therapy during acute/early HIV-1 infection, underwent analytic treatment interruption, and subsequently demonstrated viral rebound. Our data suggest that early initiation of ART arrests the maturation of HIV-1-specific antibody responses, preventing epitope diversification of antibody binding and the development of functional neutralizing capacity. Antibody responses do not appear permanently blunted, however, because viral rebound triggered the resumption of antibody maturation in our study. We also found that antibody responses measured by these assays did not predict imminent viral rebound. These data have important implications for the HIV-1 vaccine and eradication fields.

Broadly neutralizing antibody specificities detected in the genital tract of HIV-1 infected women

BACKGROUND

Broadly neutralizing antibodies (bNAbs) targeting conserved epitopes on the HIV envelope glycoprotein have been identified in blood from HIV-1 infected women. We investigated whether antibodies in the genital tract from these women share similar epitope specificities and functional profiles as those in blood.

METHODS

Immunoglobulin (Ig)G and IgA antibodies were isolated from cervicovaginal lavages or Softcups from 13 HIV-infected women in the CAPRISA cohort using Protein G and Peptide M, respectively. Binding antibodies to envelope antigens were quantified by ELISA and binding antibody multiplex assay. Neutralizing antibody titers and epitope targets were measured using the TZM-bl assay with Env-pseudotyped wild-type and mutated viruses.

RESULTS

HIV-specific IgG, but not IgA, was detected in genital secretions and the ratio of total IgG to HIV-specific IgG was similar to plasma. HIV-specific IgG reacted with multiple envelope antigens, including V1V2, gp120, gp140 and gp41. Two women had high plasma titers of HIV-specific IgG3 which was also detected in their genital tract samples. IgG from the genital tract had neutralizing activity against both Tier 1 and Tier 2 primary HIV-isolates. Antibodies targeting well known glycan epitopes and the membrane proximal region of gp41 were detected in genital secretions, and matched specificities in plasma.

CONCLUSIONS

Women with plasma bNAbs have overlapping specificities in their genital secretions, indicating that these predominantly IgG isotype antibodies may transudate from blood to the genital tract. These data provide evidence that induction of systemic HIV-specific bNAbs can lead to antiviral immunity at the portal of entry.

Monoclonal Gammopathy in HIV-1-Infected Patients: Factors Associated With Disappearance Under Long-Term Antiretroviral Therapy

OBJECTIVE

Monoclonal gammopathies (MGs) associated with HIV infection are frequent but their evolution and significance are uncertain in this population at high risk of lymphoproliferative disorder. Our aim was to describe the long-term evolution of MG in HIV-infected subjects under antiretroviral therapy.

METHODS

Retrospective study of HIV-1-infected adults, with a monoclonal (M) protein detected by serum protein electrophoresis and confirmed by immunofixation. Logistic regression was used to analyze factors associated with peak disappearance.

RESULTS

Between September 1997 and November 2012, 1219 serum protein electrophoreses were performed on our HIV cohort, and 137 (11.3%) MGs were detected. Seventy-seven subjects met the inclusion criteria: 68% male, median age 41 years, 47% AIDS stage, median CD4 count 237 per cubic millimeter, 81% uncontrolled HIV infection with HIV viral load over 400 copies per milliliter, 32% chronic hepatitis C, and 9% chronic hepatitis B. Eighteen subjects were not included because of previous or concomitant hemopathy. With a median follow-up of 6.8 years (interquartile range, 3.9-9.1), 66.2% of subjects showed a peak disappearance. In multivariate analysis, MG disappearance was associated with HIV virologic control (odds ratio, 5.98; 95% confidence interval: 1.63 to 21.87; P = 0.007) and the absence of hepatitis C virus replication at the end of follow-up (odds ratio, 10.16; 95% confidence interval: 2.36 to 43.69; P = 0.002). One subject developed a myeloma 3 years after the diagnosis of an IgA kappa MG.

CONCLUSIONS

MG associated with HIV infection concerned a young population and had favorable evolution on antiretroviral therapy in most cases. M protein disappearance was associated with HIV virologic control and the absence of chronic hepatitis C virus.

Early Loss of Splenic Tfh Cells in SIV-Infected Rhesus Macaques

Follicular T helper cells (Tfh), a subset of CD4 T lymphocytes, provide crucial help to B cells in the production of antigen-specific antibodies. Although several studies have analyzed the dynamics of Tfh cells in peripheral blood and lymph nodes (LNs) during Aids, none has yet addressed the impact of SIV infection on the dynamics of Tfh cells in the spleen, the primary organ of B cell activation. We show here a significant decrease in splenic Tfh cells in SIVmac251-infected rhesus macaques (RMs) during the acute phase of infection, which persists thereafter. This profound loss is associated with lack of sustained expression of the Tfh-defining transcription factors, Bcl-6 and c-Maf but with higher expression of the repressors KLF2 and Foxo1. In this context of Tfh abortive differentiation and loss, we found decreased percentages of memory B cell subsets and lower titers of SIV-specific IgG. We further demonstrate a drastic remodeling of the lymphoid architecture of the spleen and LNs, which disrupts the crucial cell-cell interactions necessary to maintain memory B cells and Tfh cells. Finally, our data demonstrated the early infection of Tfh cells. Paradoxically, the frequencies of SIV DNA were higher in splenic Tfh cells of RMs progressing more slowly suggesting sanctuaries for SIV in the spleen. Our findings provide important information regarding the impact of HIV/SIV infection on Tfh cells, and provide new clues for future vaccine strategies.

Among CD4 T lymphocytes, follicular T helper cells (Tfh) are essential for B cell responses. Understanding the impact of viral infections on Tfh function, in particular in deep tissues such as the spleen, which is the main organ for B cell response, may be important for vaccine development. We used a non-human primate model of AIDS to study the effect of the viral infection on T and B cell subsets. In SIV-infected rhesus macaques, we demonstrated a depletion of splenic Tfh cells in the acute phase, together with a diminution of memory B cell frequencies. Moreover, we also showed that splenic Tfh cells harbor SIV DNA early after infection, which persists throughout SIV infection. Thus, splenic Tfh may represent a potential reservoir for HIV/SIV. Collectively, our data suggests that the loss of splenic Tfh cells, which sustain memory B cells, contributes to the lack of immune control against HIV/SIV infection.

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.

Phylogenetics of HIV-1 subtype G env: Greater complexity and older origins than previously reported

HIV-1 subtype G has played an early and central role in the emergent complexity of the HIV-1 group M (HIV-1M) epidemic in central/west Africa. Here, we analysed new subtype G env sequences sampled from 8 individuals in Yaoundé, Cameroon during 2007-2010, together with all publically available subtype G-attributed full-length env sequences with known sampling dates and locations. We inferred that the most recent common ancestor (MRCA) of the analysed subtype G env sequences most likely occurred in ∼1953 (95% Highest Posterior Density interval [HPD] 1939-1963): about 15 years earlier than previous estimates. We found that the subtype G env phylogeny has a complex structure including seven distinct lineages, each likely dating back to the late 1960s or early 1970s. Sequences from Angola, Gabon and the Democratic Republic of Congo failed to group consistently in these lineages, possibly because they are related to more ancient sequences that are poorly sampled. The circulating recombinant form (CRF), CRF06_cpx env sequences but not CRF25_cpx env sequences are phylogenetically nested within the subtype G clade. This confirms that the CRF06_cpx env plausibly was derived through recombination from a subtype G parent, and suggests that the CRF25_cpx env was likely derived from an HIV-1M lineage related to the MRCA of subtype G that has remained undiscovered and may be extinct. Overall, this fills important gaps in our knowledge of the early events in the spread of HIV-1M.

The controversial impact of B cells subsets on immune response to pneumococcal vaccine in HIV-1 patients

BACKGROUND

Chronic HIV infection leads to severe perturbations of the B cell populations and hypo-responsiveness to vaccines. The associations between circulating B cell subpopulations and the antibody response to pneumococcal polysaccharide vaccine in antiretroviral-naïve and treated patients were studied.

METHODS

Sixty-six HIV-infected adults were grouped according to antiretroviral therapy (ART) and CD4+ cell count; 31 were ART-naïve and 35 were ART-treated, and they were matched for age, CD4 cell count, and duration of HIV infection. All subjects were immunized with the 23-valent polysaccharide vaccine against Streptococcus pneumoniae. Pre- and post-vaccination B cell subpopulations were assessed by flow cytometry. Serum IgG concentrations for vaccine serotypes were quantified by ELISA at baseline and at 4 and 48 weeks post-vaccination.

RESULTS

Patients under highly active antiretroviral therapy (HAART) had significantly higher antibody levels against pneumococcal vaccine antigens, while an adequate number of patients responded to vaccination. Memory B cells were diminished over time, although treated patients maintained higher levels of all subsets studied, with the exception of activated memory and isotype-switched memory B cells.

CONCLUSIONS

Low concentrations of total B cells and exhausted memory B cells was the strongest independent predictor of poor pneumococcal vaccine responsiveness, emphasizing that B cell subset disturbances are associated with a poor vaccine response among HIV-infected patients.

The dysfunction of T follicular helper cells

PURPOSE OF REVIEW

T follicular helper (Tfh) cells play a critical role as providers of B-cell help and dysfunction in Tfh/B-cell interactions can lead to autoimmunity or immunodeficiency. These observations have generated a great deal of interest in understanding how these cells are affected during HIV infection and how their functional changes might affect antibody responses.

RECENT FINDINGS

Recent studies have shown that HIV/simian immunodeficiency virus (SIV) infection affects both Tfh-cell frequency and function and suggest that Tfh-cell perturbations might contribute to the relative inefficiency of HIV-infected individuals to generate broadly neutralizing antibodies (bNAbs).

SUMMARY

The present review will highlight these recent findings addressing the role of Tfh cells in HIV infection as well as the impact HIV infection has on Tfh and circulating memory Tfh (cTfh) cell frequency and function.

Bone marrow plasma cells are a primary source of serum HIV-1-specific antibodies in chronically infected individuals

Several potent and broadly neutralizing Abs to HIV-1 have been isolated recently from peripheral blood B cells of infected individuals, based on prescreening of Ab activity in the serum. However, little is known regarding the cells that make the Abs that circulate in the blood. Accordingly, we investigated the most likely source, the bone marrow, of chronically HIV-1-infected individuals who were not receiving antiretroviral therapy. Increased frequencies of plasma cells, as well as B cell precursors, namely preB-I and preB-II, and decreased frequencies of mature B cells were observed in bone marrow aspirates of these individuals compared with HIV-negative counterparts. Increased frequencies of bone marrow plasma cells are consistent with known hallmarks of HIV-1 infection, namely hypergammaglobulinemia and increased frequencies of peripheral blood plasmablasts. Levels of HIV-1 envelope (Env)-binding and HIV-1-neutralizing Abs were measured in serum, and corresponding frequencies of Ab-secreting or Env-binding cells were measured in the blood (plasmablasts and memory B cells) and in the bone marrow (plasma cells). A strong correlation was observed between serum HIV-1-specific Abs and Env-specific bone marrow-derived plasma cells, but not circulating plasmablasts or memory B cells. These findings demonstrate that, despite HIV-1-induced phenotypic and functional B cell dysregulation in the peripheral blood and secondary lymphoid tissues, bone marrow plasma cells remain a primary source for circulating HIV-1-specific Abs in HIV-1-infected individuals.

Influence of HCV and HIV on development of cryoglobulinemia

Cryoglobulinemic syndrome refers to a systemic inflammatory process that involves small and medium-sized vessels accompanied by multi-organ damage. The aim of the present study was to determine the incidence of cryoglobulinemia among patients infected with human immunodeficiency virus (HIV), hepatitis C virus (HCV) and HCV/HIV co-infection, as well as evaluation of cryoglobulinemia type. The association was evaluated between cryoglobulinemia and clinical symptoms, selected biochemical measures of liver and kidney function, virologic measures, as well as histopathological changes in the liver. One hundred and forty-one patients were enrolled (59 HCV mono-infected, 48 HIV mono-infected, and 34 HCV/HIV co-infected). Cryoglobulinemia was nearly five times less frequent among HIV mono-infected patients (10%) than HCV mono-infected (53%) and HCV/HIV co-infected patients (59%). Cryoglobulinemia was more frequent in patients infected with genotype 1 HCV than genotype 3 (63% vs. 46%, p=0.12). There was a lower incidence of cryoglobulinemia in HIV mono-infected patients treated with antiretroviral drugs (p=0.04). Cryoglobulinemia correlated with ALT activity (p=0.01) and HIV viral load (p<0.001). Symptoms were significantly more frequent among cryoglobulinemic patients than those without cryoglobulinemia (38% vs. 9%, p<0.001). The most common symptoms related to cryoglobulinemia, regardless of cryoglobulinemia type, were fatigue (38%), arthralgia (20%), polineuropathy (18%), and skin lesions (14%). In conclusion, HCV mono-infection and HCV/HIV co-infection, regardless of HCV genotype, are potent stimulators of cryoglobulinemia, with its symptomatic form occurring in about 40% of cases. Effective antiretroviral therapy seems to be protective against cryoglobulinemia development in HIV mono-infected patients.

Antibody-dependent effector functions against HIV decline in subjects receiving antiretroviral therapy

BACKGROUND

Combination antiretroviral therapy (cART) effectively controls human immunodeficiency virus (HIV) infection but does not eliminate HIV, and lifelong treatment is therefore required. HIV-specific cytotoxic T lymphocyte (CTL) responses decline following cART initiation. Alterations in other HIV-specific immune responses that may assist in eliminating latent HIV infection, specifically antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent phagocytosis (ADP), are unclear.

METHODS

A cohort of 49 cART-naive HIV-infected subjects from Thailand (mean baseline CD4 count, 188 cells/µL; mean viral load, 5.4 log10 copies/mL) was followed for 96 weeks after initiating cART. ADCC and ADP assays were performed using serum samples obtained at baseline and after 96 weeks of cART.

RESULTS

A 35% reduction in HIV type 1 envelope (Env)-specific ADCC-mediated killing of target cells (P<.001) was observed after 96 weeks of cART. This was corroborated by a significant reduction in the ability of Env-specific ADCC antibodies to activate natural killer cells (P<.001). Significantly reduced ADP was also observed after 96 weeks of cART (P=.018).

CONCLUSIONS

This longitudinal study showed that cART resulted in significant reductions of HIV-specific effector antibody responses, including ADCC and ADP. Therapeutic vaccines or other immunomodulatory approaches may be required to improve antibody-mediated control of HIV during cART.

Insights into B cells and HIV-specific B-cell responses in HIV-infected individuals

Human immunodeficiency virus (HIV) disease is associated with dysregulation and dysfunction involving all major lymphocyte populations, including B cells. Such perturbations occur early in the course of infection and are driven in large part by immune activation resulting from ongoing HIV replication leading to bystander effects on B cells. While most of the knowledge regarding immune cell abnormalities in HIV-infected individuals has been gained from studies conducted on the peripheral blood, it is clear that the virus is most active and most damaging in lymphoid tissues. Here, we discuss B-cell perturbations in HIV-infected individuals, focusing on the skewing of B-cell subsets that circulate in the peripheral blood and their counterparts that reside in lymphoid tissues. This review also highlights recent advances in evaluating HIV-specific B-cell responses both in the memory B-cell compartment, as well as in circulating antibody-secreting plasmablasts and the more differentiated plasma cells residing in tissues. Finally, we consider how knowledge gained by investigating B cells in HIV-infected individuals may help inform the development of an effective antibody-based HIV vaccine.

HIV-1 specific antibody titers and neutralization among chronically infected patients on long-term suppressive antiretroviral therapy (ART): a cross-sectional study

The majority of potent and broadly neutralizing antibodies against HIV-1 have been isolated from untreated patients with acute or chronic infection. To assess the extent of HIV-1 specific antibody response and neutralization after many years of virologic suppression from potent combination ART, we examined antibody binding titers and neutralization of 51 patients with chronic HIV-1 infection on suppressive ART for at least three years. In this cross-sectional analysis, we found high antibody titers against gp120, gp41, and the membrane proximal external region (MPER) in 59%, 43%, and 27% of patients, respectively. We observed significantly higher endpoint binding titers for gp120 and gp41 for patients with >10 compared to ≤10 years of detectable HIV RNA. Additionally, we observed higher median gp120 and gp41 antibody titers in patients with HIV RNA <50 copies/mL for ≤5 years. 22% of patients neutralized a HIV-1 primary isolate (HIV-1_JR-FL) and 8% neutralized a HIV-2/HIV-1 MPER chimera. Significantly greater HIV-1_JR-FL neutralization was found among patients with >10 years of detectable HIV RNA (8/20 [40.0%] versus 3/31 [9.7%] for ≤10 years, p = 0.02) and a trend toward greater neutralization in patients with ≤5 years of HIV RNA <50 copies/mL (7/20 [35.0%] versus 4/31 [12.9%] for >5 years, p = 0.08). All patients with neutralizing activity mediated successful phagocytosis of VLPs by THP-1 cells after antibody opsonization. Our findings of highly specific antibodies to several structural epitopes of HIV-1 with antibody effector functions and neutralizing activity after long-term suppressive ART, suggest continuous antigenic stimulation and evolution of HIV-specific antibody response occurs before and after suppression with ART. These patients, particularly those with slower HIV progression and more time with detectable viremia prior to initiation of suppressive ART, are a promising population to identify and further study functional antibodies against HIV-1.

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.