Safety and immunogenicity of a delayed booster dose of the rVSVΔG-ZEBOV-GP vaccine for prevention of Ebola virus disease: a multicentre, open-label, phase 2 randomised controlled trial.

BACKGROUND: rVSVΔG-ZEBOV-GP is the first approved vaccine with clinical efficacy against Ebola virus disease. Although a seroprotective threshold has not been defined for those at occupational risk of exposure, the current vaccine strategy is to attain a sustained high level of antibody titres. The aim of this trial was to explore the effects of delayed boosting upon both the height and duration of antibody titres following primary immunisation. METHODS: In this open-label phase 2 randomised controlled trial, we compared antibody titres at month 36 in participants who had received a homologous booster dose at month 18 following primary immunisation with those who had received no booster. From Oct 25, 2016, to Jan 29, 2020, healthy adults aged 18 years or older deemed at occupational risk of exposure to Ebola virus due to laboratory work, clinical duties, or travel to an active endemic region were recruited from four hospital clinics in the USA and one hospital clinic in Canada and received primary vaccination with 2×107 plaque-forming unit per mL of VSVΔG-ZEBOV-GP. 18 months later, individuals who consented and were still eligible were randomly assigned 1:1 to receive either a homologous booster dose or no booster. Study visits for safety and serial blood collections for antibody titres were done on enrolled participants at months 0, 1, 3, 6, 12, 18, 19, 24, 30, and 36. Through July, 2021, a web-based application was used for randomisation, including assignments with schedules for each of the five sites using mixed permuted blocks. The trial was not masked to participants or site staff. The primary endpoint was a comparison of geometric mean titres (GMTs) of anti-Ebola virus glycoprotein IgG antibody at month 36 (ie, 18 months after randomisation) for all randomly assigned participants who completed the 36 months of follow-up (primary analysis cohort). Investigators were aware of antibody titres from baseline (enrolment) through month 18 but were masked to summary data by randomisation group after month 18. This study is registered with ClinicalTrials.gov (NCT02788227). FINDINGS: Of the 248 participants who enrolled and received their primary immunisation, 114 proceeded to the randomisation step at month 18. The two randomisation groups were balanced: 57 participants (24 [42%] of whom were female; median age was 42 years [IQR 35-50]) were randomly assigned to the booster group and 57 (24 [42%] of whom were female; median age was 42 years [IQR 36-51]) to the no-booster group. Of those randomly assigned, 92 participants (45 in the booster group and 47 in the no-booster group) completed 36 months of follow-up. At 18 months after primary immunisation, GMTs in the no-booster group increased from a baseline of 10 ELISA units (EU)/mL (95% CI 7-14) to 1451 EU/mL (1118-1882); GMTs in the booster group increased from 9 EU/mL (6-16) to 1769 EU/mL (1348-2321). At month 19, GMTs were 31 408 EU/mL (23 181-42 554) for the booster group and 1406 EU/mL (1078-1833) for the no-booster group; at month 36, GMTs were 10 146 EU/mL (7960-12 933) for the booster group and 1240 EU/mL (984-1563) for the no-booster group. Accordingly, the geometric mean ratio (GMR) of antibody titres had increased almost 21-fold more in the booster versus no-booster group at 1 month after booster administration (GMR 20·6; 95% CI 18·2-23·0; p<0·0001) and was still over 7-fold higher at month 36 (GMR 7·8; 95% CI 5·5-10·2; p<0·0001). Consistent with previous reports of this vaccine's side-effects, transient mono-articular or oligo-articular arthritis was diagnosed in 18 (9%) of 207 primary vaccination recipients; after randomisation, arthritis was diagnosed in one (2%) of 57 participants in the no-booster group. No new cases of arthritis developed after booster administration. Four serious adverse events occurred following randomisation: one (epistaxis) in the booster group and three (gastrointestinal haemorrhage, prostate cancer, and tachyarrhythmia) in the no-booster group. None of the serious adverse events was judged attributable to the booster vaccination assignment. INTERPRETATION: In addition to no new safety concerns and in marked contrast to earlier trials evaluating short-term boosting, delaying a rVSVΔG-ZEBOV-GP booster until month 18 resulted in an increase in GMT that remained several-fold above the no-booster group GMT for at least 18 months. These findings could have implications for defining the optimal timing of booster doses as pre-exposure prophylaxis in populations at ongoing risk for Ebola virus exposure. FUNDING: The Division of Intramural Research and the Division of Clinical Research of the National Institute of Allergy and Infectious Diseases at the US National Institutes of Health, Canadian Immunization Research Network through the Public Health Agency of Canada, Canadian Institutes of Health Research, and the US Defense Threat Reduction Agency.

Inhibition of HIV-1 release by ADAM metalloproteinase inhibitors.

HIV-1 gp120 glycan binding to C-type lectin adhesion receptor L-selectin/CD62L on CD4 T cells facilitates viral attachment and entry. Paradoxically, the adhesion receptor impedes HIV-1 budding from infected T cells and the viral release requires the shedding of CD62L. To systematically investigate CD62L-shedding mediated viral release and its potential inhibition, we screened compounds specific for serine-, cysteine-, aspartyl-, and Zn-dependent proteases for CD62L shedding inhibition and found that a subclass of Zn-metalloproteinase inhibitors, including BB-94, TAPI, prinomastat, GM6001, and GI25423X, suppressed CD62L shedding. Their inhibition of HIV-1 infections correlated with enzymatic suppression of both ADAM10 and 17 activities and expressions of these ADAMs were transiently induced during the viral infection. These metalloproteinase inhibitors are distinct from the current antiretroviral drug compounds. Using immunogold labeling of CD62L, we observed association between budding HIV-1 virions and CD62L by transmission electron microscope, and the extent of CD62L-tethering of budding virions increased when the receptor shedding is inhibited. Finally, these CD62L shedding inhibitors suppressed the release of HIV-1 virions by CD4 T cells of infected individuals and their virion release inhibitions correlated with their CD62L shedding inhibitions. Our finding reveals a new therapeutic approach targeted at HIV-1 viral release.

HIV vaccines induce CD8+ T cells with low antigen receptor sensitivity.

Current HIV vaccines designed to stimulate CD8+ T cells have failed to induce immunologic control upon infection. The functions of vaccine-induced HIV-specific CD8+ T cells were investigated here in detail. Cytotoxic capacity was significantly lower than in HIV controllers and was not a consequence of low frequency or unaccumulated functional cytotoxic proteins. Low cytotoxic capacity was attributable to impaired degranulation in response to the low antigen levels present on HIV-infected targets. The vaccine-induced T cell receptor (TCR) repertoire was polyclonal and transduction of these TCRs conferred the same reduced functions. These results define a mechanism accounting for poor antiviral activity induced by these vaccines and suggest that an effective CD8+ T cell response may require a vaccination strategy that drives further TCR clonal selection.

Adaptive immune responses to SARS-CoV-2 persist in the pharyngeal lymphoid tissue of children.

Most studies of adaptive immunity to SARS-CoV-2 infection focus on peripheral blood, which may not fully reflect immune responses at the site of infection. Using samples from 110 children undergoing tonsillectomy and adenoidectomy during the COVID-19 pandemic, we identified 24 samples with evidence of previous SARS-CoV-2 infection, including neutralizing antibodies in serum and SARS-CoV-2-specific germinal center and memory B cells in the tonsils and adenoids. Single-cell B cell receptor (BCR) sequencing indicated virus-specific BCRs were class-switched and somatically hypermutated, with overlapping clones in the two tissues. Expanded T cell clonotypes were found in tonsils, adenoids and blood post-COVID-19, some with CDR3 sequences identical to previously reported SARS-CoV-2-reactive T cell receptors (TCRs). Pharyngeal tissues from COVID-19-convalescent children showed persistent expansion of germinal center and antiviral lymphocyte populations associated with interferon (IFN)-γ-type responses, particularly in the adenoids, and viral RNA in both tissues. Our results provide evidence for persistent tissue-specific immunity to SARS-CoV-2 in the upper respiratory tract of children after infection.

Broadly neutralizing antibodies target the coronavirus fusion peptide.

The potential for future coronavirus outbreaks highlights the need to broadly target this group of pathogens. We used an epitope-agnostic approach to identify six monoclonal antibodies that bind to spike proteins from all seven human-infecting coronaviruses. All six antibodies target the conserved fusion peptide region adjacent to the S2' cleavage site. COV44-62 and COV44-79 broadly neutralize alpha- and betacoronaviruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariants BA.2 and BA.4/5, albeit with lower potency than receptor binding domain-specific antibodies. In crystal structures of COV44-62 and COV44-79 antigen-binding fragments with the SARS-CoV-2 fusion peptide, the fusion peptide epitope adopts a helical structure and includes the arginine residue at the S2' cleavage site. COV44-79 limited disease caused by SARS-CoV-2 in a Syrian hamster model. These findings highlight the fusion peptide as a candidate epitope for next-generation coronavirus vaccine development.

Robust, persistent adaptive immune responses to SARS-CoV-2 in the oropharyngeal lymphoid tissue of children.

SARS-CoV-2 infection triggers adaptive immune responses from both T and B cells. However, most studies focus on peripheral blood, which may not fully reflect immune responses in lymphoid tissues at the site of infection. To evaluate both local and systemic adaptive immune responses to SARS-CoV-2, we collected peripheral blood, tonsils, and adenoids from 110 children undergoing tonsillectomy/adenoidectomy during the COVID-19 pandemic and found 24 with evidence of prior SARS-CoV-2 infection, including detectable neutralizing antibodies against multiple viral variants. We identified SARS-CoV-2-specific germinal center (GC) and memory B cells; single cell BCR sequencing showed that these virus-specific B cells were class-switched and somatically hypermutated, with overlapping clones in the adenoids and tonsils. Oropharyngeal tissues from COVID-19-convalescent children showed persistent expansion of GC and anti-viral lymphocyte populations associated with an IFN-γ-type response, with particularly prominent changes in the adenoids, as well as evidence of persistent viral RNA in both tonsil and adenoid tissues of many participants. Our results show robust, tissue-specific adaptive immune responses to SARS-CoV-2 in the upper respiratory tract of children weeks to months after acute infection, providing evidence of persistent localized immunity to this respiratory virus.

Germinal Center T follicular helper (GC-Tfh) cell impairment in chronic HIV infection involves c-Maf signaling.

We have recently demonstrated that the function of T follicular helper (Tfh) cells from lymph nodes (LN) of HIV-infected individuals is impaired. We found that these cells were unable to provide proper help to germinal center (GC)-B cells, as observed by altered and inefficient anti-HIV antibody response and premature death of memory B cells. The underlying molecular mechanisms of this dysfunction remain poorly defined. Herein, we have used a unique transcriptional approach to identify these molecular defects. We consequently determined the transcriptional profiles of LN GC-Tfh cells following their interactions with LN GC-B cells from HIV-infected and HIV-uninfected individuals, rather than analyzing resting ex-vivo GC-Tfh cells. We observed that proliferating GC-Tfh cells from HIV-infected subjects were transcriptionally different than their HIV-uninfected counterparts, and displayed a significant downregulation of immune- and GC-Tfh-associated pathways and genes. Our results strongly demonstrated that MAF (coding for the transcription factor c-Maf) and its upstream signaling pathway mediators (IL6R and STAT3) were significantly downregulated in HIV-infected subjects, which could contribute to the impaired GC-Tfh and GC-B cell functions reported during infection. We further showed that c-Maf function was associated with the adenosine pathway and that the signaling upstream c-Maf could be partially restored by adenosine deaminase -1 (ADA-1) supplementation. Overall, we identified a novel mechanism that contributes to GC-Tfh cell impairment during HIV infection. Understanding how GC-Tfh cell function is altered in HIV is crucial and could provide critical information about the mechanisms leading to the development and maintenance of effective anti-HIV antibodies.

Lost in Translation: Lack of CD4 Expression due to a Novel Genetic Defect.

CD4 expression identifies a subset of mature T cells primarily assisting the germinal center reaction and contributing to CD8+ T-cell and B-cell activation, functions, and longevity. Herein, we present a family in which a novel variant disrupting the translation-initiation codon of the CD4 gene resulted in complete loss of membrane and plasma soluble CD4 in peripheral blood, lymph node, bone marrow, skin, and ileum of a homozygous proband. This inherited CD4 knockout disease illustrates the clinical and immunological features of a complete deficiency of any functional component of CD4 and its similarities and differences with other clinical models of primary or acquired loss of CD4+ T cells. The first inherited loss of any functional component of CD4, including soluble CD4, is clinically distinct from any other congenital or acquired CD4 T-cell defect and characterized by compensatory changes in T-cell subsets and functional impairment of B cells, monocytes, and natural killer cells.

T-bet+ Memory B Cells Stay in Place.

Memory B cells (MBCs) expressing the transcription factor T-bet have been described in normal and dysregulated immune responses. In this issue of Immunity, Johnson et al. report that T-bet+ MBCs, formed in response to a primary influenza infection, contribute to protective antibody titers and persist mainly in the spleen with restricted trafficking between tissues.

Broad immune activation underlies shared set point signatures for vaccine responsiveness in healthy individuals and disease activity in patients with lupus.

Responses to vaccination and to diseases vary widely across individuals, which may be partly due to baseline immune variations. Identifying such baseline predictors of immune responses and their biological basis is of broad interest, given their potential importance for cancer immunotherapy, disease outcomes, vaccination and infection responses. Here we uncover baseline blood transcriptional signatures predictive of antibody responses to both influenza and yellow fever vaccinations in healthy subjects. These same signatures evaluated at clinical quiescence are correlated with disease activity in patients with systemic lupus erythematosus with plasmablast-associated flares. CITE-seq profiling of 82 surface proteins and transcriptomes of 53,201 single cells from healthy high and low influenza vaccination responders revealed that our signatures reflect the extent of activation in a plasmacytoid dendritic cell-type I IFN-T/B lymphocyte network. Our findings raise the prospect that modulating such immune baseline states may improve vaccine responsiveness and mitigate undesirable autoimmune disease activity.

HIV-1 targets L-selectin for adhesion and induces its shedding for viral release.

CD4 and chemokine receptors mediate HIV-1 attachment and entry. They are, however, insufficient to explain the preferential viral infection of central memory T cells. Here, we identify L-selectin (CD62L) as a viral adhesion receptor on CD4+ T cells. The binding of viral envelope glycans to L-selectin facilitates HIV entry and infection, and L-selectin expression on central memory CD4+ T cells supports their preferential infection by HIV. Upon infection, the virus downregulates L-selectin expression through shedding, resulting in an apparent loss of central memory CD4+ T cells. Infected effector memory CD4+ T cells, however, remain competent in cytokine production. Surprisingly, inhibition of L-selectin shedding markedly reduces HIV-1 infection and suppresses viral release, suggesting that L-selectin shedding is required for HIV-1 release. These findings highlight a critical role for cell surface sheddase in HIV-1 pathogenesis and reveal new antiretroviral strategies based on small molecular inhibitors targeted at metalloproteinases for viral release.

Impaired B cell immunity in acute myeloid leukemia patients after chemotherapy.

BACKGROUND: Changes in adaptive immune cells after chemotherapy in adult acute myeloid leukemia (AML) may have implications for the success of immunotherapy. This study was designed to determine the functional capacity of the immune system in adult patients with AML who have completed chemotherapy and are potential candidates for immunotherapy. METHODS: We used the response to seasonal influenza vaccination as a surrogate for the robustness of the immune system in 10 AML patients in a complete remission post-chemotherapy and performed genetic, phenotypic, and functional characterization of adaptive immune cell subsets. RESULTS: Only 2 patients generated protective titers in response to vaccination, and a majority of patients had abnormal frequencies of transitional and memory B-cells. B-cell receptor sequencing showed a B-cell repertoire with little evidence of somatic hypermutation in most patients. Conversely, frequencies of T-cell populations were similar to those seen in healthy controls, and cytotoxic T-cells demonstrated antigen-specific activity after vaccination. Effector T-cells had increased PD-1 expression in AML patients least removed from chemotherapy. CONCLUSION: Our results suggest that while some aspects of cellular immunity recover quickly, humoral immunity is incompletely reconstituted in the year following intensive cytotoxic chemotherapy for AML. The observed B-cell abnormalities may explain the poor response to vaccination often seen in AML patients after chemotherapy. Furthermore, the uncoupled recovery of B-cell and T-cell immunity and increased PD-1 expression shortly after chemotherapy might have implications for the success of several modalities of immunotherapy.

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.

CRISPR-Cas9 gene repair of hematopoietic stem cells from patients with X-linked chronic granulomatous disease.

Gene repair of CD34+ hematopoietic stem and progenitor cells (HSPCs) may avoid problems associated with gene therapy, such as vector-related mutagenesis and dysregulated transgene expression. We used CRISPR (clustered regularly interspaced short palindromic repeat)/Cas9 (CRISPR-associated 9) to repair a mutation in the CYBB gene of CD34+ HSPCs from patients with the immunodeficiency disorder X-linked chronic granulomatous disease (X-CGD). Sequence-confirmed repair of >20% of HSPCs from X-CGD patients restored the function of NADPH (nicotinamide adenine dinucleotide phosphate) oxidase and superoxide radical production in myeloid cells differentiated from these progenitor cells in vitro. Transplant of gene-repaired X-CGD HSPCs into NOD (nonobese diabetic) SCID (severe combined immunodeficient) γc-/- mice resulted in efficient engraftment and production of functional mature human myeloid and lymphoid cells for up to 5 months. Whole-exome sequencing detected no indels outside of the CYBB gene after gene correction. CRISPR-mediated gene editing of HSPCs may be applicable to other CGD mutations and other monogenic disorders of the hematopoietic system.

Cardiovascular benefits of lycopene: fantasy or reality?

Epidemiological evidence indicates that high consumption of tomatoes and tomato-based products reduces the risk of chronic diseases such as CVD and cancer. Such potential benefits are often ascribed to high concentrations of lycopene present in tomato products. Mainly from the results of in vitro studies, potential biological mechanisms by which carotenoids could protect against heart disease and cancer have been suggested. These include cholesterol reduction, inhibition of oxidation processes, modulation of inflammatory markers, enhanced intercellular communication, inhibition of tumourigenesis and induction of apoptosis, metabolism to retinoids and antiangiogenic effects. However, with regard to CVD, results from intervention studies gave mixed results. Over fifty human intervention trials with lycopene supplements or tomato-based products have been conducted to date, the majority being underpowered. Many showed some beneficial effects but mostly on non-established cardiovascular risk markers such as lipid peroxidation, DNA oxidative damage, platelet activation and inflammatory markers. Only a few studies showed improvement in lipid profiles, C reactive protein and blood pressure. However, recent findings indicate that lycopene could exert cardiovascular protection by lowering HDL-associated inflammation, as well as by modulating HDL functionality towards an antiatherogenic phenotype. Furthermore, in vitro studies indicate that lycopene could modulate T lymphocyte activity, which would also inhibit atherogenic processes and confer cardiovascular protection. These findings also suggest that HDL functionality deserves further consideration as a potential early marker for CVD risk, modifiable by dietary factors such as lycopene.

Effect of HIV Antibody VRC01 on Viral Rebound after Treatment Interruption.

BACKGROUND: The discovery of potent and broadly neutralizing antibodies (bNAbs) against human immunodeficiency virus (HIV) has made passive immunization a potential strategy for the prevention and treatment of HIV infection. We sought to determine whether passive administration of VRC01, a bNAb targeting the HIV CD4-binding site, can safely prevent or delay plasma viral rebound after the discontinuation of antiretroviral therapy (ART). METHODS: We conducted two open-label trials (AIDS Clinical Trials Group [ACTG] A5340 and National Institutes of Health [NIH] 15-I-0140) of the safety, side-effect profile, pharmacokinetic properties, and antiviral activity of VRC01 in persons with HIV infection who were undergoing interruption of ART. RESULTS: A total of 24 participants were enrolled, and one serious alcohol-related adverse event occurred. Viral rebound occurred despite plasma VRC01 concentrations greater than 50 µg per milliliter. The median time to rebound was 4 weeks in the A5340 trial and 5.6 weeks in the NIH trial. Study participants were more likely than historical controls to have viral suppression at week 4 (38% vs. 13%, P=0.04 by a two-sided Fisher's exact test in the A5340 trial; and 80% vs. 13%, P<0.001 by a two-sided Fisher's exact test in the NIH trial) but the difference was not significant at week 8. Analyses of virus populations before ART as well as before and after ART interruption showed that VRC01 exerted pressure on rebounding virus, resulting in restriction of recrudescent viruses and selection for preexisting and emerging antibody neutralization-resistant virus. CONCLUSIONS: VRC01 slightly delayed plasma viral rebound in the trial participants, as compared with historical controls, but it did not maintain viral suppression by week 8. In the small number of participants enrolled in these trials, no safety concerns were identified with passive immunization with a single bNAb (VRC01). (Funded by the National Institute of Allergy and Infectious Diseases and others; ACTG A5340 and NIH 15-I-0140 ClinicalTrials.gov numbers, NCT02463227 and NCT02471326 .).

Lentiviral hematopoietic stem cell gene therapy for X-linked severe combined immunodeficiency.

X-linked severe combined immunodeficiency (SCID-X1) is a profound deficiency of T, B, and natural killer (NK) cell immunity caused by mutations inIL2RGencoding the common chain (γc) of several interleukin receptors. Gamma-retroviral (γRV) gene therapy of SCID-X1 infants without conditioning restores T cell immunity without B or NK cell correction, but similar treatment fails in older SCID-X1 children. We used a lentiviral gene therapy approach to treat five SCID-X1 patients with persistent immune dysfunction despite haploidentical hematopoietic stem cell (HSC) transplant in infancy. Follow-up data from two older patients demonstrate that lentiviral vector γc transduced autologous HSC gene therapy after nonmyeloablative busulfan conditioning achieves selective expansion of gene-marked T, NK, and B cells, which is associated with sustained restoration of humoral responses to immunization and clinical improvement at 2 to 3 years after treatment. Similar gene marking levels have been achieved in three younger patients, albeit with only 6 to 9 months of follow-up. Lentiviral gene therapy with reduced-intensity conditioning appears safe and can restore humoral immune function to posthaploidentical transplant older patients with SCID-X1.

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.

Additive loss-of-function proteasome subunit mutations in CANDLE/PRAAS patients promote type I IFN production.

Autosomal recessive mutations in proteasome subunit ß 8 (PSMB8), which encodes the inducible proteasome subunit ß5i, cause the immune-dysregulatory disease chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE), which is classified as a proteasome-associated autoinflammatory syndrome (PRAAS). Here, we identified 8 mutations in 4 proteasome genes, PSMA3 (encodes α7), PSMB4 (encodes ß7), PSMB9 (encodes ß1i), and proteasome maturation protein (POMP), that have not been previously associated with disease and 1 mutation in PSMB8 that has not been previously reported. One patient was compound heterozygous for PSMB4 mutations, 6 patients from 4 families were heterozygous for a missense mutation in 1 inducible proteasome subunit and a mutation in a constitutive proteasome subunit, and 1 patient was heterozygous for a POMP mutation, thus establishing a digenic and autosomal dominant inheritance pattern of PRAAS. Function evaluation revealed that these mutations variably affect transcription, protein expression, protein folding, proteasome assembly, and, ultimately, proteasome activity. Moreover, defects in proteasome formation and function were recapitulated by siRNA-mediated knockdown of the respective subunits in primary fibroblasts from healthy individuals. Patient-isolated hematopoietic and nonhematopoietic cells exhibited a strong IFN gene-expression signature, irrespective of genotype. Additionally, chemical proteasome inhibition or progressive depletion of proteasome subunit gene transcription with siRNA induced transcription of type I IFN genes in healthy control cells. Our results provide further insight into CANDLE genetics and link global proteasome dysfunction to increased type I IFN production.