Phase 1 trial evaluating safety and pharmacokinetics of HIV-1 broadly neutralizing mAbs 10E8VLS and VRC07-523LS.

BACKGROUNDBroadly neutralizing monoclonal antibodies (bNAbs) represent a promising strategy for HIV-1 immunoprophylaxis and treatment. 10E8VLS and VRC07-523LS are bNAbs that target the highly conserved membrane-proximal external region (MPER) and the CD4-binding site of the HIV-1 viral envelope glycoprotein, respectively.METHODSIn this phase 1, open-label trial, we evaluated the safety and pharmacokinetics of 5 mg/kg 10E8VLS administered alone, or concurrently with 5 mg/kg VRC07-523LS, via s.c. injection to healthy non-HIV-infected individuals.RESULTSEight participants received either 10E8VLS alone (n = 6) or 10E8VLS and VRC07-523LS in combination (n = 2). Five (n = 5 of 8, 62.5%) participants who received 10E8VLS experienced moderate local reactogenicity, and 1 participant (n = 1/8, 12.5%) experienced severe local reactogenicity. Further trial enrollment was stopped, and no participant received repeat dosing. All local reactogenicity resolved without sequelae. 10E8VLS retained its neutralizing capacity, and no functional anti-drug antibodies were detected; however, a serum t1/2 of 8.1 days was shorter than expected. Therefore, the trial was voluntarily stopped per sponsor decision (Vaccine Research Center, National Institute of Allergy and Infectious Diseases [NIAID], NIH). Mechanistic studies performed to investigate the underlying reason for the reactogenicity suggest that multiple mechanisms may have contributed, including antibody aggregation and upregulation of local inflammatory markers.CONCLUSION10E8VLS resulted in unexpected reactogenicity and a shorter t1/2 in comparison with previously tested bNAbs. These studies may facilitate identification of nonreactogenic second-generation MPER-targeting bNAbs, which could be an effective strategy for HIV-1 immunoprophylaxis and treatment.TRIAL REGISTRATIONClinicaltrials.gov, accession no. NCT03565315.FUNDINGDivision of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH.

Subcutaneous Administration of a Monoclonal Antibody to Prevent Malaria.

BACKGROUND: Subcutaneous administration of the monoclonal antibody L9LS protected adults against controlled Plasmodium falciparum infection in a phase 1 trial. Whether a monoclonal antibody administered subcutaneously can protect children from P. falciparum infection in a region where this organism is endemic is unclear. METHODS: We conducted a phase 2 trial in Mali to assess the safety and efficacy of subcutaneous administration of L9LS in children 6 to 10 years of age over a 6-month malaria season. In part A of the trial, safety was assessed at three dose levels in adults, followed by assessment at two dose levels in children. In part B of the trial, children were randomly assigned, in a 1:1:1 ratio, to receive 150 mg of L9LS, 300 mg of L9LS, or placebo. The primary efficacy end point, assessed in a time-to-event analysis, was the first P. falciparum infection, as detected on blood smear performed at least every 2 weeks for 24 weeks. A secondary efficacy end point was the first episode of clinical malaria, as assessed in a time-to-event analysis. RESULTS: No safety concerns were identified in the dose-escalation part of the trial (part A). In part B, 225 children underwent randomization, with 75 children assigned to each group. No safety concerns were identified in part B. P. falciparum infection occurred in 36 participants (48%) in the 150-mg group, in 30 (40%) in the 300-mg group, and in 61 (81%) in the placebo group. The efficacy of L9LS against P. falciparum infection, as compared with placebo, was 66% (adjusted confidence interval [95% CI], 45 to 79) with the 150-mg dose and 70% (adjusted 95% CI, 50 to 82) with the 300-mg dose (P<0.001 for both comparisons). Efficacy against clinical malaria was 67% (adjusted 95% CI, 39 to 82) with the 150-mg dose and 77% (adjusted 95% CI, 55 to 89) with the 300-mg dose (P<0.001 for both comparisons). CONCLUSIONS: Subcutaneous administration of L9LS to children was protective against P. falciparum infection and clinical malaria over a period of 6 months. (Funded by the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT05304611.).

Long trimer-immunization interval and appropriate adjuvant reduce immune responses to the soluble HIV-1-envelope trimer base.

Soluble 'SOSIP'-stabilized HIV-1 envelope glycoprotein (Env) trimers elicit dominant antibody responses targeting their glycan-free base regions, potentially diminishing neutralizing responses. Previously, using a nonhuman primate model, we demonstrated that priming with fusion peptide (FP)-carrier conjugate immunogens followed by boosting with Env trimers reduced the anti-base response. Further, we demonstrated that longer immunization intervals further reduced anti-base responses and increased neutralization breadth. Here, we demonstrate that long trimer-boosting intervals, but not long FP immunization intervals, reduce the anti-base response. Additionally, we identify that FP priming before trimer immunization enhances antibody avidity to the Env trimer. We also establish that adjuvants Matrix M and Adjuplex further reduce anti-base responses and increase neutralizing titers. FP priming, long trimer-immunization interval, and an appropriate adjuvant can thus reduce anti-base antibody responses and improve Env-directed vaccine outcomes.

Immune responses to SARS-CoV-2 mRNA vaccination in people with idiopathic CD4 lymphopenia.

BACKGROUND: The immunogenicity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccines is variable in individuals with different inborn errors of immunity or acquired immune deficiencies and is yet unknown in people with idiopathic CD4 lymphopenia (ICL). OBJECTIVE: We sought to determine the immunogenicity of mRNA vaccines in patients with ICL with a broad range of CD4 T-cell counts. METHODS: Samples were collected from 25 patients with ICL and 23 age- and sex-matched healthy volunteers (HVs) after their second or third SARS-CoV-2 mRNA vaccine dose. Anti-spike and anti-receptor binding domain antibodies were measured. T-cell receptor sequencing and stimulation assays were performed to quantify SARS-CoV-2-specific T-cell responses. RESULTS: The median age of ICL participants was 51 years, and their median CD4 count was 150 cells/µL; 11 participants had CD4 counts ≤100 cells/µL. Anti-spike IgG antibody levels were greater in HVs than in patients with ICL after 2 and 3 doses of mRNA vaccine. There was no detectable significant difference, however, in anti-S IgG between HVs and participants with ICL and CD4 counts >100 cells/µL. The depth of spike-specific T-cell responses by T-cell receptor sequencing was lower in individuals with ICL. Activation-induced markers and cytokine production of spike-specific CD4 T cells in participants with ICL did not differ significantly compared with HVs after 2 or 3 vaccine doses. CONCLUSIONS: Patients with ICL and CD4 counts >100 cells/µL can mount vigorous humoral and cellular immune responses to SARS-CoV-2 vaccination; however, patients with more severe CD4 lymphopenia have blunted vaccine-induced immunity and may require additional vaccine doses and other risk mitigation strategies.

Adjuvanted SARS-CoV-2 spike protein vaccination elicits long-lived plasma cells in nonhuman primates.

Durable humoral immunity is mediated by long-lived plasma cells (LLPCs) that reside in the bone marrow. It remains unclear whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein vaccination is able to elicit and maintain LLPCs. Here, we describe a sensitive method to identify and isolate antigen-specific LLPCs by tethering antibodies secreted by these cells onto the cell surface. Using this method, we found that two doses of adjuvanted SARS-CoV-2 spike protein vaccination are able to induce spike protein-specific LLPC reservoirs enriched for receptor binding domain specificities in the bone marrow of nonhuman primates that are detectable for several months after vaccination. Immunoglobulin gene sequencing confirmed that several of these LLPCs were clones of memory B cells elicited 2 weeks after boost that had undergone further somatic hypermutation. Many of the antibodies secreted by these LLPCs also exhibited improved neutralization and cross-reactivity compared with earlier time points. These findings establish our method as a means to sensitively and reliably detect rare antigen-specific LLPCs and demonstrate that adjuvanted SARS-CoV-2 spike protein vaccination establishes spike protein-specific LLPC reservoirs.

Soluble prefusion-closed HIV-envelope trimers with glycan-covered bases.

Soluble HIV-1-envelope (Env) trimers elicit immune responses that target their solvent-exposed protein bases, the result of removing these trimers from their native membrane-bound context. To assess whether glycosylation could limit these base responses, we introduced sequons encoding potential N-linked glycosylation sites (PNGSs) into base-proximal regions. Expression and antigenic analyses indicated trimers bearing six-introduced PNGSs to have reduced base recognition. Cryo-EM analysis revealed trimers with introduced PNGSs to be prone to disassembly and introduced PNGS to be disordered. Protein-base and glycan-base trimers induced reciprocally symmetric ELISA responses, in which only a small fraction of the antibody response to glycan-base trimers recognized protein-base trimers and vice versa. EM polyclonal epitope mapping revealed glycan-base trimers -even those that were stable biochemically- to elicit antibodies that recognized disassembled trimers. Introduced glycans can thus mask the protein base but their introduction may yield neo-epitopes that dominate the immune response.

Extended safety and tolerability of subcutaneous CAP256V2LS and VRC07-523LS in HIV-negative women: study protocol for the randomised, placebo-controlled double-blinded, phase 2 CAPRISA 012C trial.

INTRODUCTION: Women-controlled HIV prevention technologies that overcome adherence challenges of available daily oral pre-exposure prophylaxis and give women a choice of options are urgently needed. Broadly neutralising monoclonal antibodies (bnAbs) administered passively may offer a valuable non-antiretroviral biological intervention for HIV prevention. Animal and human studies have demonstrated that bnAbs which neutralise HIV can prevent infection. The optimal plasma antibody concentrations to confer protection against HIV infection in humans is under intense study. The Centre for the AIDS Programme of Research in South Africa (CAPRISA) 012C trial will evaluate extended safety and pharmacokinetics of CAP256V2LS and VRC07-523LS among young HIV-negative South African and Zambian women. The study design also allows for an evaluation of a signal of HIV prevention efficacy. METHODS AND ANALYSIS: CAPRISA 012 is a series of trials with three distinct protocols. The completed CAPRISA 012A and 012B phase 1 trials provided critical data for the CAPRISA 012C trial, which is divided into parts A and B. In part A, 90 participants were randomised to receive both CAP256V2LS and VRC07-523LS at 20 mg/kg or placebo, subcutaneously every 16 or 24 weeks. Part B will enrol 900 participants in South Africa and Zambia who will be randomised in a 1:1 ratio and receive an initial loading dose of 1.2 g of CAP256V2LS and VRC07-523LS or placebo followed by 600 mg of CAP256V2LS and 1.2 g of VRC07-523LS or placebo subcutaneously every 6 months. Safety will be assessed by frequency and severity of reactogenicity and other related adverse events. Pharmacokinetics of both antibodies will be measured in systemic and mucosal compartments over time, while participants will be monitored for breakthrough HIV infections. ETHICS AND DISSEMINATION OF STUDY FINDINGS: The University of KwaZulu-Natal Biomedical Research Ethics Committee and South African Health Products Regulatory Authority have approved the trial (BREC/00002492/2021, SAHPRA20210317). Results will be disseminated through conference presentations, peer-reviewed publications and the clinical trial registry. TRIAL REGISTRATION NUMBER: PACTR202112683307570.

Deep Phenotyping of Neurologic Postacute Sequelae of SARS-CoV-2 Infection.

BACKGROUND AND OBJECTIVES: SARS-CoV-2 infection has been associated with a syndrome of long-term neurologic sequelae that is poorly characterized. We aimed to describe and characterize in-depth features of neurologic postacute sequelae of SARS-CoV-2 infection (neuro-PASC). METHODS: Between October 2020 and April 2021, 12 participants were seen at the NIH Clinical Center under an observational study to characterize ongoing neurologic abnormalities after SARS-CoV-2 infection. Autonomic function and CSF immunophenotypic analysis were compared with healthy volunteers (HVs) without prior SARS-CoV-2 infection tested using the same methodology. RESULTS: Participants were mostly female (83%), with a mean age of 45 ± 11 years. The median time of evaluation was 9 months after COVID-19 (range 3-12 months), and most (11/12, 92%) had a history of only a mild infection. The most common neuro-PASC symptoms were cognitive difficulties and fatigue, and there was evidence for mild cognitive impairment in half of the patients (MoCA score <26). The majority (83%) had a very disabling disease, with Karnofsky Performance Status ≤80. Smell testing demonstrated different degrees of microsmia in 8 participants (66%). Brain MRI scans were normal, except 1 patient with bilateral olfactory bulb hypoplasia that was likely congenital. CSF analysis showed evidence of unique intrathecal oligoclonal bands in 3 cases (25%). Immunophenotyping of CSF compared with HVs showed that patients with neuro-PASC had lower frequencies of effector memory phenotype both for CD4+ T cells (p < 0.0001) and for CD8+ T cells (p = 0.002), an increased frequency of antibody-secreting B cells (p = 0.009), and increased frequency of cells expressing immune checkpoint molecules. On autonomic testing, there was evidence for decreased baroreflex-cardiovagal gain (p = 0.009) and an increased peripheral resistance during tilt-table testing (p < 0.0001) compared with HVs, without excessive plasma catecholamine responses. DISCUSSION: CSF immune dysregulation and neurocirculatory abnormalities after SARS-CoV-2 infection in the setting of disabling neuro-PASC call for further evaluation to confirm these changes and explore immunomodulatory treatments in the context of clinical trials.

An influenza H1 hemagglutinin stem-only immunogen elicits a broadly cross-reactive B cell response in humans.

Current yearly seasonal influenza vaccines primarily induce an antibody response directed against the immunodominant but continually diversifying hemagglutinin (HA) head region. These antibody responses provide protection against the vaccinating strain but little cross-protection against other influenza strains or subtypes. To focus the immune response on subdominant but more conserved epitopes on the HA stem that might protect against a broad range of influenza strains, we developed a stabilized H1 stem immunogen lacking the immunodominant head displayed on a ferritin nanoparticle (H1ssF). Here, we evaluated the B cell response to H1ssF in healthy adults ages 18 to 70 in a phase 1 clinical trial (NCT03814720). We observed both a strong plasmablast response and sustained elicitation of cross-reactive HA stem-specific memory B cells after vaccination with H1ssF in individuals of all ages. The B cell response was focused on two conserved epitopes on the H1 stem, with a highly restricted immunoglobulin repertoire unique to each epitope. On average, two-thirds of the B cell and serological antibody response recognized a central epitope on the H1 stem and exhibited broad neutralization across group 1 influenza virus subtypes. The remaining third recognized an epitope near the viral membrane anchor and was largely limited to H1 strains. Together, we demonstrate that an H1 HA immunogen lacking the immunodominant HA head produces a robust and broadly neutralizing HA stem-directed B cell response.

An influenza hemagglutinin stem nanoparticle vaccine induces cross-group 1 neutralizing antibodies in healthy adults.

Influenza vaccines could be improved by platforms inducing cross-reactive immunity. Immunodominance of the influenza hemagglutinin (HA) head in currently licensed vaccines impedes induction of cross-reactive neutralizing stem-directed antibodies. A vaccine without the variable HA head domain has the potential to focus the immune response on the conserved HA stem. This first-in-human dose-escalation open-label phase 1 clinical trial (NCT03814720) tested an HA stabilized stem ferritin nanoparticle vaccine (H1ssF) based on the H1 HA stem of A/New Caledonia/20/1999. Fifty-two healthy adults aged 18 to 70 years old enrolled to receive either 20 µg of H1ssF once (n = 5) or 60 µg of H1ssF twice (n = 47) with a prime-boost interval of 16 weeks. Thirty-five (74%) 60-µg dose participants received the boost, whereas 11 (23%) boost vaccinations were missed because of public health restrictions in the early stages of the COVID-19 pandemic. The primary objective of this trial was to evaluate the safety and tolerability of H1ssF, and the secondary objective was to evaluate antibody responses after vaccination. H1ssF was safe and well tolerated, with mild solicited local and systemic reactogenicity. The most common symptoms included pain or tenderness at the injection site (n = 10, 19%), headache (n = 10, 19%), and malaise (n = 6, 12%). We found that H1ssF elicited cross-reactive neutralizing antibodies against the conserved HA stem of group 1 influenza viruses, despite previous H1 subtype head-specific immunity. These responses were durable, with neutralizing antibodies observed more than 1 year after vaccination. Our results support this platform as a step forward in the development of a universal influenza vaccine.

Kinetics of the Antibody Response to Symptomatic SARS-CoV-2 Infection in Vaccinated and Unvaccinated Individuals in the Blinded Phase of the mRNA-1273 COVID-19 Vaccine Efficacy Trial.

Background: Hybrid immunity is associated with more durable protection against coronavirus disease 2019 (COVID-19). We describe the antibody responses following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in vaccinated and unvaccinated individuals. Methods: The 55 vaccine arm COVID-19 cases diagnosed during the blinded phase of the Coronavirus Efficacy trial were matched with 55 placebo arm COVID-19 cases. Pseudovirus neutralizing antibody (nAb) activity to the ancestral strain and binding antibody (bAb) responses to nucleocapsid and spike antigens (ancestral and variants of concern [VOCs]) were assessed on disease day 1 (DD1) and 28 days later (DD29). Results: The primary analysis set was 46 vaccine cases and 49 placebo cases with COVID-19 at least 57 days post-first dose. For vaccine group cases, there was a 1.88-fold rise in ancestral antispike bAbs 1 month post-disease onset, although 47% had no increase. The vaccine-to-placebo geometric mean ratios for DD29 antispike and antinucleocapsid bAbs were 6.9 and 0.04, respectively. DD29 mean bAb levels were higher for vaccine vs placebo cases for all VOCs. DD1 nasal viral load positively correlated with bAb levels in the vaccine group. Conclusions: Following COVID-19, vaccinated participants had higher levels and greater breadth of antispike bAbs and higher nAb titers than unvaccinated participants. These were largely attributable to the primary immunization series.

Safety and pharmacokinetics of escalating doses of neutralising monoclonal antibody CAP256V2LS administered with and without VRC07-523LS in HIV-negative women in South Africa (CAPRISA 012B): a phase 1, dose-escalation, randomised controlled trial.

BACKGROUND: Young women in sub-Saharan Africa continue to bear a high burden of HIV infection. Combination anti-HIV monoclonal antibodies are a potential HIV prevention technology that could overcome adherence challenges of daily oral pre-exposure prophylaxis. In this phase 1 clinical trial we aimed to determine the safety and pharmacokinetic profile of the broadly neutralising monoclonal antibody CAP256V2LS. METHODS: CAPRISA 012B, a first-in-human dose-escalation phase 1 trial evaluated the safety, pharmacokinetics, and neutralisation activity of CAP256V2LS alone and in combination with VRC07-523LS in young HIV-negative women in Durban, South Africa. Groups 1 and 2 were open label with CAP256V2LS administered at 5 mg/kg and 10 mg/kg intravenously and 5 mg/kg, 10 mg/kg, and 20 mg/kg subcutaneously. In group 3, participants were randomly allocated to receive a combination of CAP256V2LS and VRC07-523LS at 10 mg/kg and 20 mg/kg subcutaneously comixed with ENHANZE, a recombinant human hyaluronidase. Once safety was established in the first three participants, dose escalation took place sequentially following review of safety data. Primary endpoints were the proportion of participants with mild, moderate, and severe reactogenicity or adverse events, graded as per the Division of AIDS toxicity grading. The trial is registered on the Pan African Clinical Trial Registry, PACTR202003767867253, and is recruiting. FINDINGS: From July 13, 2020, to Jan 13, 2021, 42 HIV-negative women, aged 18-45 years, were enrolled. All 42 participants, eight with intravenous and 34 with subcutaneous administration, completed the trial. There were no serious adverse events or dose-limiting toxicities. Most commonly reported symptoms following intravenous administration were headaches in seven (88%) and nausea in four (50%) participants. Commonly reported symptoms following subcutaneous administration were headache in 31 (91%), chills in 25 (74%), and malaise or fatigue in 19 (56%) participants. Adverse events included transient lymphocytopenia in eight (19%), proteinuria in nine (21%), elevated aspartate aminotransferase in ten (24%), and alanine aminotransferase in five (12%) participants. INTERPRETATION: CAP256V2LS administered alone and in combination with VRC07-523LS was safe with favourable pharmacokinetics and neutralisation activity, supporting further assessment in larger clinical studies. FUNDING: European and Developing Countries Clinical Trials Partnership, South African Medical Research Council, and South African Department of Science and Innovation.

Low-dose intravenous and subcutaneous CIS43LS monoclonal antibody for protection against malaria (VRC 612 Part C): a phase 1, adaptive trial.

BACKGROUND: Human monoclonal antibodies might offer an important new approach to reduce malaria morbidity and mortality. In the first two parts of a three-part clinical trial, the antimalarial monoclonal antibody CIS43LS conferred high protection against parasitaemia at doses of 20 mg/kg or 40 mg/kg administered intravenously followed by controlled human malaria infection. The ability of CIS43LS to confer protection at lower doses or by the subcutaneous route is unknown. We aimed to provide data on the safety and optimisation of dose and route for the human antimalaria monoclonal antibody CIS43LS. METHODS: VRC 612 Part C was the third part of a three-part, first-in-human, phase 1, adaptive trial, conducted at the University of Maryland, Baltimore Center for Vaccine Development and Global Health, Baltimore, MD, USA. We enrolled adults aged 18-50 years with no previous malaria vaccinations or infections, in a sequential, dose-escalating manner. Eligible participants received the monoclonal antibody CIS43LS in a single, open-label dose of 1 mg/kg, 5 mg/kg, or 10 mg/kg intravenously, or 5 mg/kg or 10 mg/kg subcutaneously. Participants underwent controlled human malaria infection by the bites of five mosquitoes infected with Plasmodium falciparum 3D7 strain approximately 8 weeks after their monoclonal antibody inoculation. Six additional control participants who did not receive CIS43LS underwent controlled human malaria infection simultaneously. Participants were followed-up daily on days 7-18 and day 21, with qualitative PCR used for P falciparum detection. Participants who tested positive for P falciparum were treated with atovaquone-proguanil and those who remained negative were treated at day 21. Participants were followed-up until 24 weeks after dosing. The primary outcome was safety and tolerability of CIS43LS at each dose level, assessed in the as-treated population. Secondary outcomes included protective efficacy of CIS43LS after controlled human malaria infection. This trial is now complete and is registered with ClinicalTrials.gov, NCT04206332. FINDINGS: Between Sept 1, 2021, and Oct 29, 2021, 47 people were assessed for eligibility and 31 were enrolled (one subsequently withdrew and was replaced) and assigned to receive doses of 1 mg/kg (n=7), 5 mg/kg (n=4), and 10 mg/kg (n=3) intravenously and 5 mg/kg (n=4) and 10 mg/kg (n=4) subcutaneously, or to the control group (n=8). CIS43LS administration was safe and well tolerated; no serious adverse events occurred. CIS43LS protected 18 (82%) of 22 participants who received a dose. No participants developed parasitaemia following dosing at 5 mg/kg intravenously or subcutaneously, or at 10 mg/kg intravenously or subcutaneously. All six control participants and four of seven participants dosed at 1 mg/kg intravenously developed parasitaemia after controlled human malaria infection. INTERPRETATION: CIS43LS was safe and well tolerated, and conferred protection against P falciparum at low doses and by the subcutaneous route, providing evidence that this approach might be useful to prevent malaria across several clinical use cases. FUNDING: National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Safety, tolerability, and immunogenicity of the chimpanzee adenovirus type 3-vectored Marburg virus (cAd3-Marburg) vaccine in healthy adults in the USA: a first-in-human, phase 1, open-label, dose-escalation trial.

BACKGROUND: WHO has identified Marburg virus as an emerging virus requiring urgent vaccine research and development, particularly due to its recent emergence in Ghana. We report results from a first-in-human clinical trial evaluating a replication-deficient recombinant chimpanzee adenovirus type 3 (cAd3)-vectored vaccine encoding a wild-type Marburg virus Angola glycoprotein (cAd3-Marburg) in healthy adults. METHODS: We did a first-in-human, phase 1, open-label, dose-escalation trial of the cAd3-Marburg vaccine at the Walter Reed Army Institute of Research Clinical Trials Center in the USA. Healthy adults aged 18-50 years were assigned to receive a single intramuscular dose of cAd3-Marburg vaccine at either 1 × 1010 or 1 × 1011 particle units (pu). Primary safety endpoints included reactogenicity assessed for the first 7 days and all adverse events assessed for 28 days after vaccination. Secondary immunogenicity endpoints were assessment of binding antibody responses and T-cell responses against the Marburg virus glycoprotein insert, and assessment of neutralising antibody responses against the cAd3 vector 4 weeks after vaccination. This study is registered with ClinicalTrials.gov, NCT03475056. FINDINGS: Between Oct 9, 2018, and Jan 31, 2019, 40 healthy adults were enrolled and assigned to receive a single intramuscular dose of cAd3-Marburg vaccine at either 1 × 1010 pu (n=20) or 1 × 1011 pu (n=20). The cAd3-Marburg vaccine was safe, well tolerated, and immunogenic. All enrolled participants received cAd3-Marburg vaccine, with 37 (93%) participants completing follow-up visits; two (5%) participants moved from the area and one (3%) was lost to follow-up. No serious adverse events related to vaccination occurred. Mild to moderate reactogenicity was observed after vaccination, with symptoms of injection site pain and tenderness (27 [68%] of 40 participants), malaise (18 [45%] of 40 participants), headache (17 [43%] of 40 participants), and myalgia (14 [35%] of 40 participants) most commonly reported. Glycoprotein-specific antibodies were induced in 38 (95%) of 40 participants 4 weeks after vaccination, with geometric mean titres of 421 [95% CI 209-846] in the 1 × 1010 pu group and 545 [276-1078] in the 1 × 1011 pu group, and remained significantly elevated at 48 weeks compared with baseline titres (39 [95% CI 13-119] in the 1 ×1010 pu group and 27 [95-156] in the 1 ×1011 pu group; both p<0·0001). T-cell responses to the glycoprotein insert and neutralising responses against the cAd3 vector were also increased at 4 weeks after vaccination. INTERPRETATION: This first-in-human trial of this cAd3-Marburg vaccine showed the agent is safe and immunogenic, with a safety profile similar to previously tested cAd3-vectored filovirus vaccines. 95% of participants produced a glycoprotein-specific antibody response at 4 weeks after a single vaccination, which remained in 70% of participants at 48 weeks. These findings represent a crucial step in the development of a vaccine for emergency deployment against a re-emerging pathogen that has recently expanded its reach to new regions. FUNDING: National Institutes of Health.

Application of B cell immortalization for the isolation of antibodies and B cell clones from vaccine and infection settings.

The isolation and characterization of neutralizing antibodies from infection and vaccine settings informs future vaccine design, and methodologies that streamline the isolation of antibodies and the generation of B cell clones are of great interest. Retroviral transduction to express Bcl-6 and Bcl-xL and transform primary B cells has been shown to promote long-term B cell survival and antibody secretion in vitro, and can be used to isolate antibodies from memory B cells. However, application of this methodology to B cell subsets from different tissues and B cells from chronically infected individuals has not been well characterized. Here, we characterize Bcl-6/Bcl-xL B cell immortalization across multiple tissue types and B cell subsets in healthy and HIV-1 infected individuals, as well as individuals recovering from malaria. In healthy individuals, naïve and memory B cell subsets from PBMCs and tonsil tissue transformed with similar efficiencies, and displayed similar characteristics with respect to their longevity and immunoglobulin secretion. In HIV-1-viremic individuals or in individuals with recent malaria infections, the exhausted CD27-CD21- memory B cells transformed with lower efficiency, but the transformed B cells expanded and secreted IgG with similar efficiency. Importantly, we show that this methodology can be used to isolate broadly neutralizing antibodies from HIV-infected individuals. Overall, we demonstrate that Bcl-6/Bcl-xL B cell immortalization can be used to isolate antibodies and generate B cell clones from different B cell populations, albeit with varying efficiencies.

Primary exposure to SARS-CoV-2 variants elicits convergent epitope specificities, immunoglobulin V gene usage and public B cell clones.

An important consequence of infection with a SARS-CoV-2 variant is protective humoral immunity against other variants. However, the basis for such cross-protection at the molecular level is incompletely understood. Here, we characterized the repertoire and epitope specificity of antibodies elicited by infection with the Beta, Gamma and WA1 ancestral variants and assessed their cross-reactivity to these and the more recent Delta and Omicron variants. We developed a method to obtain immunoglobulin sequences with concurrent rapid production and functional assessment of monoclonal antibodies from hundreds of single B cells sorted by flow cytometry. Infection with any variant elicited similar cross-binding antibody responses exhibiting a conserved hierarchy of epitope immunodominance. Furthermore, convergent V gene usage and similar public B cell clones were elicited regardless of infecting variant. These convergent responses despite antigenic variation may account for the continued efficacy of vaccines based on a single ancestral variant.

Safety and Efficacy of a Monoclonal Antibody against Malaria in Mali.

BACKGROUND: CIS43LS is a monoclonal antibody that was shown to protect against controlled Plasmodium falciparum infection in a phase 1 clinical trial. Whether a monoclonal antibody can prevent P. falciparum infection in a region in which the infection is endemic is unknown. METHODS: We conducted a phase 2 trial to assess the safety and efficacy of a single intravenous infusion of CIS43LS against P. falciparum infection in healthy adults in Mali over a 6-month malaria season. In Part A, safety was assessed at three escalating dose levels. In Part B, participants were randomly assigned (in a 1:1:1 ratio) to receive 10 mg of CIS43LS per kilogram of body weight, 40 mg of CIS43LS per kilogram, or placebo. The primary efficacy end point, assessed in a time-to-event analysis, was the first P. falciparum infection detected on blood-smear examination, which was performed at least every 2 weeks for 24 weeks. At enrollment, all the participants received artemether-lumefantrine to clear possible P. falciparum infection. RESULTS: In Part B, 330 adults underwent randomization; 110 were assigned to each trial group. The risk of moderate headache was 3.3 times as high with 40 mg of CIS43LS per kilogram as with placebo. P. falciparum infections were detected on blood-smear examination in 39 participants (35.5%) who received 10 mg of CIS43LS per kilogram, 20 (18.2%) who received 40 mg of CIS43LS per kilogram, and 86 (78.2%) who received placebo. At 6 months, the efficacy of 40 mg of CIS43LS per kilogram as compared with placebo was 88.2% (adjusted 95% confidence interval [CI], 79.3 to 93.3; P<0.001), and the efficacy of 10 mg of CIS43LS per kilogram as compared with placebo was 75.0% (adjusted 95% CI, 61.0 to 84.0; P<0.001). CONCLUSIONS: CIS43LS was protective against P. falciparum infection over a 6-month malaria season in Mali without evident safety concerns. (Funded by the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT04329104.).

Immune correlates analysis of the ENSEMBLE single Ad26.COV2.S dose vaccine efficacy clinical trial.

Measuring immune correlates of disease acquisition and protection in the context of a clinical trial is a prerequisite for improved vaccine design. We analysed binding and neutralizing antibody measurements 4 weeks post vaccination as correlates of risk of moderate to severe-critical COVID-19 through 83 d post vaccination in the phase 3, double-blind placebo-controlled phase of ENSEMBLE, an international randomized efficacy trial of a single dose of Ad26.COV2.S. We also evaluated correlates of protection in the trial cohort. Of the three antibody immune markers we measured, we found most support for 50% inhibitory dilution (ID50) neutralizing antibody titre as a correlate of risk and of protection. The outcome hazard ratio was 0.49 (95% confidence interval 0.29, 0.81; P = 0.006) per 10-fold increase in ID50; vaccine efficacy was 60% (43%, 72%) at non-quantifiable ID50 (<2.7 IU50 ml-1) and increased to 89% (78%, 96%) at ID50 = 96.3 IU50 ml-1. Comparison of the vaccine efficacy by ID50 titre curves for ENSEMBLE-US, the COVE trial of the mRNA-1273 vaccine and the COV002-UK trial of the AZD1222 vaccine supported the ID50 titre as a correlate of protection across trials and vaccine types.

Interval between prior SARS-CoV-2 infection and booster vaccination impacts magnitude and quality of antibody and B cell responses.

SARS-CoV-2 mRNA booster vaccines provide protection from severe disease, eliciting strong immunity that is further boosted by previous infection. However, it is unclear whether these immune responses are affected by the interval between infection and vaccination. Over a 2-month period, we evaluated antibody and B cell responses to a third-dose mRNA vaccine in 66 individuals with different infection histories. Uninfected and post-boost but not previously infected individuals mounted robust ancestral and variant spike-binding and neutralizing antibodies and memory B cells. Spike-specific B cell responses from recent infection (<180 days) were elevated at pre-boost but comparatively less so at 60 days post-boost compared with uninfected individuals, and these differences were linked to baseline frequencies of CD27lo B cells. Day 60 to baseline ratio of BCR signaling measured by phosphorylation of Syk was inversely correlated to days between infection and vaccination. Thus, B cell responses to booster vaccines are impeded by recent infection.

Clinical outcomes and immune responses to SARS-CoV-2 vaccination in severe aplastic anaemia.

Patients with severe aplastic anaemia (SAA) are often not vaccinated against viruses due to concerns of ineffective protective antibody response and potential for pathogenic global immune system activation, leading to relapse. We evaluated the impact of COVID-19 vaccination on haematological indices and disease status and characterized the humoural and cellular responses to vaccination in 50 SAA patients, who were previously treated with immunosuppressive therapy (IST). There was no significant difference in haemoglobin (p = 0.52), platelet count (p = 0.67), absolute lymphocyte (p = 0.42) and neutrophil (p = 0.98) counts prior to and after completion of vaccination series. Relapse after vaccination, defined as a progressive decline in counts requiring treatment, occurred in three patients (6%). Humoural response was detectable in 90% (28/31) of cases by reduction in an in-vitro Angiotensin II Converting Enzyme (ACE2) binding and neutralization assay, even in patients receiving ciclosporin (10/11, 90.1%). Comparison of spike-specific T-cell responses in 27 SAA patients and 10 control subjects revealed qualitatively similar CD4+ Th1-dominant responses to vaccination. There was no difference in CD4+ (p = 0.77) or CD8+ (p = 0.74) T-cell responses between patients on or off ciclosporin therapy at the time of vaccination. Our data highlight appropriate humoural and cellular responses in SAA previously treated with IST and true relapse after vaccination is rare.