SARS-CoV-2 infection of endothelial cells, dependent on flow-induced ACE2 expression, drives hypercytokinemia in a vascularized microphysiological system.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for COVID-19, has caused nearly 7 million deaths worldwide. Severe cases are marked by an aggressive inflammatory response known as hypercytokinemia, contributing to endothelial damage. Although vaccination has reduced hospitalizations, hypercytokinemia persists in breakthrough infections, emphasizing the need for disease models mimicking this response. Using a 3D microphysiological system (MPS), we explored the vascular role in SARS-CoV-2-induced hypercytokinemia. Methods: The vascularized micro-organ (VMO) MPS, consisting of human-derived primary endothelial cells (ECs) and stromal cells within an extracellular matrix, was used to model SARS-CoV-2 infection. A non-replicative pseudotyped virus fused to GFP was employed, allowing visualization of viral entry into human ECs under physiologic flow conditions. Expression of ACE2, TMPRSS2, and AGTR1 was analyzed, and the impact of viral infection on ACE2 expression, vascular inflammation, and vascular morphology was assessed. Results: The VMO platform facilitated the study of COVID-19 vasculature infection, revealing that ACE2 expression increased significantly in direct response to shear stress, thereby enhancing susceptibility to infection by pseudotyped SARS-CoV-2. Infected ECs secreted pro-inflammatory cytokines, including IL-6 along with coagulation factors. Cytokines released by infected cells were able to activate downstream, non-infected EC, providing an amplification mechanism for inflammation and coagulopathy. Discussion: Our findings highlight the crucial role of vasculature in COVID-19 pathogenesis, emphasizing the significance of flow-induced ACE2 expression and subsequent inflammatory responses. The VMO provides a valuable tool for studying SARS-CoV-2 infection dynamics and evaluating potential therapeutics.

Outpatient COVID-19 convalescent plasma recipient antibody thresholds correlated to reduced hospitalizations within a randomized trial.

BACKGROUNDCOVID-19 convalescent plasma (CCP) virus-specific antibody levels that translate into recipient posttransfusion antibody levels sufficient to prevent disease progression are not defined.METHODSThis secondary analysis correlated donor and recipient antibody levels to hospitalization risk among unvaccinated, seronegative CCP recipients within the outpatient, double-blind, randomized clinical trial that compared CCP to control plasma. The majority of COVID-19 CCP arm hospitalizations (15/17, 88%) occurred in this unvaccinated, seronegative subgroup. A functional cutoff to delineate recipient high versus low posttransfusion antibody levels was established by 2 methods: (i) analyzing virus neutralization-equivalent anti-Spike receptor-binding domain immunoglobulin G (anti-S-RBD IgG) responses in donors or (ii) receiver operating characteristic (ROC) curve analysis.RESULTSSARS-CoV-2 anti-S-RBD IgG antibody was volume diluted 21.3-fold into posttransfusion seronegative recipients from matched donor units. Virus-specific antibody delivered was approximately 1.2 mg. The high-antibody recipients transfused early (symptom onset within 5 days) had no hospitalizations. A CCP-recipient analysis for antibody thresholds correlated to reduced hospitalizations found a statistical significant association between early transfusion and high antibodies versus all other CCP recipients (or control plasma), with antibody cutoffs established by both methods-donor-based virus neutralization cutoffs in posttransfusion recipients (0/85 [0%] versus 15/276 [5.6%]; P = 0.03) or ROC-based cutoff (0/94 [0%] versus 15/267 [5.4%]; P = 0.01).CONCLUSIONIn unvaccinated, seronegative CCP recipients, early transfusion of plasma units in the upper 30% of study donors' antibody levels reduced outpatient hospitalizations. High antibody level plasma units, given early, should be reserved for therapeutic use.TRIAL REGISTRATIONClinicalTrials.gov NCT04373460.FUNDINGDepartment of Defense (W911QY2090012); Defense Health Agency; Bloomberg Philanthropies; the State of Maryland; NIH (3R01AI152078-01S1, U24TR001609-S3, 1K23HL151826NIH); the Mental Wellness Foundation; the Moriah Fund; Octapharma; the Healthnetwork Foundation; the Shear Family Foundation; the NorthShore Research Institute; and the Rice Foundation.

A Broad-Spectrum Multi-Antigen mRNA/LNP-Based Pan-Coronavirus Vaccine Induced Potent Cross-Protective Immunity Against Infection and Disease Caused by Highly Pathogenic and Heavily Spike-Mutated SARS-CoV-2 Variants of Concern in the Syrian Hamster Model.

The first-generation Spike-alone-based COVID-19 vaccines have successfully contributed to reducing the risk of hospitalization, serious illness, and death caused by SARS-CoV-2 infections. However, waning immunity induced by these vaccines failed to prevent immune escape by many variants of concern (VOCs) that emerged from 2020 to 2024, resulting in a prolonged COVID-19 pandemic. We hypothesize that a next-generation Coronavirus (CoV) vaccine incorporating highly conserved non-Spike SARS-CoV-2 antigens would confer stronger and broader cross-protective immunity against multiple VOCs. In the present study, we identified ten non-Spike antigens that are highly conserved in 8.7 million SARS-CoV-2 strains, twenty-one VOCs, SARS-CoV, MERS-CoV, Common Cold CoVs, and animal CoVs. Seven of the 10 antigens were preferentially recognized by CD8+ and CD4+ T-cells from unvaccinated asymptomatic COVID-19 patients, irrespective of VOC infection. Three out of the seven conserved non-Spike T cell antigens belong to the early expressed Replication and Transcription Complex (RTC) region, when administered to the golden Syrian hamsters, in combination with Spike, as nucleoside-modified mRNA encapsulated in lipid nanoparticles (LNP) (i.e., combined mRNA/LNP-based pan-CoV vaccine): (i) Induced high frequencies of lung-resident antigen-specific CXCR5+CD4+ T follicular helper (TFH) cells, GzmB+CD4+ and GzmB+CD8+ cytotoxic T cells (TCYT), and CD69+IFN-γ+TNFα+CD4+ and CD69+IFN-γ+TNFα+CD8+ effector T cells (TEFF); and (ii) Reduced viral load and COVID-19-like symptoms caused by various VOCs, including the highly pathogenic B.1.617.2 Delta variant and the highly transmittable heavily Spike-mutated XBB1.5 Omicron sub-variant. The combined mRNA/LNP-based pan-CoV vaccine could be rapidly adapted for clinical use to confer broader cross-protective immunity against emerging highly mutated and pathogenic VOCs.

COVID-19 convalescent plasma therapy decreases inflammatory cytokines: a randomized controlled trial.

IMPORTANCE: This study examined the role that cytokines may have played in the beneficial outcomes found when outpatient individuals infected with SARS-CoV-2 were transfused with COVID-19 convalescent plasma (CCP) early in their infection. We found that the pro-inflammatory cytokine IL-6 decreased significantly faster in patients treated early with CCP. Participants with COVID-19 treated with CCP later in the infection did not have the same effect. This decrease in IL-6 levels after early CCP treatment suggests a possible role of inflammation in COVID-19 progression. The evidence of IL-6 involvement brings insight into the possible mechanisms involved in CCP treatment mitigating SARS-CoV-2 severity.

Aerosol delivery of SARS-CoV-2 human monoclonal antibodies in macaques limits viral replication and lung pathology.

Passively administered monoclonal antibodies (mAbs) given before or after viral infection can prevent or blunt disease. Here, we examine the efficacy of aerosol mAb delivery to prevent infection and disease in rhesus macaques inoculated with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant via intranasal and intratracheal routes. SARS-CoV-2 human mAbs or a human mAb directed to respiratory syncytial virus (RSV) are nebulized and delivered using positive airflow via facemask to sedated macaques pre- and post-infection. Nebulized human mAbs are detectable in nasal, oropharyngeal, and bronchoalveolar lavage (BAL) samples. SARS-CoV-2 mAb treatment significantly reduces levels of SARS-CoV-2 viral RNA and infectious virus in the upper and lower respiratory tracts relative to controls. Reductions in lung and BAL virus levels correspond to reduced BAL inflammatory cytokines and lung pathology. Aerosolized antibody therapy for SARS-CoV-2 could be effective for reducing viral burden and limiting disease severity.

Early antibody treatment, inflammation, and risk of post-COVID conditions.

IMPORTANCE: Approximately 20% of individuals infected with SARS-CoV-2 experienced long-term health effects, as defined PCC. However, it is unknown if there are any early biomarkers associated with PCC or whether early intervention treatments may decrease the risk of PCC. In a secondary analysis of a randomized clinical trial, this study demonstrates that among outpatients with SARS-CoV-2, increased IL-6 at time of infection is associated with increased odds of PCC. In addition, among individuals treated early, within 5 days of symptom onset, with COVID-19 convalescent plasma, there was a trend for decreased odds of PCC after adjusting for other demographic and clinical characteristics. Future treatment studies should be considered to evaluate the effect of early treatment and anti-IL-6 therapies on PCC development.

Dynamics of inflammatory responses after SARS-CoV-2 infection by vaccination status in the USA: a prospective cohort study.

BACKGROUND: Cytokines and chemokines play a critical role in the response to infection and vaccination. We aimed to assess the longitudinal association of COVID-19 vaccination with cytokine and chemokine concentrations and trajectories among people with SARS-CoV-2 infection. METHODS: In this longitudinal, prospective cohort study, blood samples were used from participants enrolled in a multi-centre randomised trial assessing the efficacy of convalescent plasma therapy for ambulatory COVID-19. The trial was conducted in 23 outpatient sites in the USA. In this study, participants (aged ≥18 years) were restricted to those with COVID-19 before vaccination or with breakthrough infections who had blood samples and symptom data collected at screening (pre-transfusion), day 14, and day 90 visits. Associations between COVID-19 vaccination status and concentrations of 21 cytokines and chemokines (measured using multiplexed sandwich immunoassays) were examined using multivariate linear mixed-effects regression models, adjusted for age, sex, BMI, hypertension, diabetes, trial group, and COVID-19 waves (pre-alpha or alpha and delta). FINDINGS: Between June 29, 2020, and Sept 30, 2021, 882 participants recently infected with SARS-CoV-2 were enrolled, of whom 506 (57%) were female and 376 (43%) were male. 688 (78%) of 882 participants were unvaccinated, 55 (6%) were partly vaccinated, and 139 (16%) were fully vaccinated at baseline. After adjusting for confounders, geometric mean concentrations of interleukin (IL)-2RA, IL-7, IL-8, IL-15, IL-29 (interferon-λ), inducible protein-10, monocyte chemoattractant protein-1, and tumour necrosis factor-α were significantly lower among the fully vaccinated group than in the unvaccinated group at screening. On day 90, fully vaccinated participants had approximately 20% lower geometric mean concentrations of IL-7, IL-8, and vascular endothelial growth factor-A than unvaccinated participants. Cytokine and chemokine concentrations decreased over time in the fully and partly vaccinated groups and unvaccinated group. Log10 cytokine and chemokine concentrations decreased faster among participants in the unvaccinated group than in other groups, but their geometric mean concentrations were generally higher than fully vaccinated participants at 90 days. Days since full vaccination and type of vaccine received were not correlated with cytokine and chemokine concentrations. INTERPRETATION: Initially and during recovery from symptomatic COVID-19, fully vaccinated participants had lower concentrations of inflammatory markers than unvaccinated participants suggesting vaccination is associated with short-term and long-term reduction in inflammation, which could in part explain the reduced disease severity and mortality in vaccinated individuals. FUNDING: US Department of Defense, National Institutes of Health, Bloomberg Philanthropies, State of Maryland, Mental Wellness Foundation, Moriah Fund, Octapharma, HealthNetwork Foundation, and the Shear Family Foundation.

Transfusion reactions associated with COVID-19 convalescent plasma in outpatient clinical trials.

BACKGROUND: COVID-19 convalescent plasma (CCP) is an important therapeutic option for outpatients at high risk of hospitalization from SARS-CoV-2 infection. We assessed the safety of outpatient CCP transfusions administered during clinical trials. STUDY DESIGN AND METHODS: We analyzed data pertaining to transfusion-related reactions from two randomized controlled trials in the U.S. that evaluated the efficacy of CCP versus control plasma in various ambulatory settings. Multivariable logistic regression was used to assess whether CCP was associated with transfusion reactions, after adjusting for potential confounders. RESULTS: The combined study reported 79/1351 (5.9%) adverse events during the transfusion visit, with the majority 62/1351 (4.6%) characterized by mild, allergic-type findings of urticaria, and/or pruritus consistent with minor allergic transfusion reactions; the other reported events were attributed to the patients' underlying disease, COVID-19, or vasovagal in nature. We found no difference in the likelihood of allergic transfusion reactions between those receiving CCP versus control plasma (adjusted odds ratio [AOR], 0.75; 95% CI, 0.43-1.31). Risk of urticaria and/or pruritus increased with a pre-existing diagnosis of asthma (AOR, 2.33; 95% CI, 1.16-4.67). We did not observe any CCP-attributed antibody disease enhancement in participants with COVID-19 or increased risk of infection. There were no life-threatening severe transfusion reactions and no patients required hospitalization related to transfusion-associated complications. DISCUSSION: Outpatient plasma administration was safely performed for nearly 1400 participants. CCP is a safe therapeutic option for outpatients at risk of hospitalization from COVID-19.

Outpatient COVID-19 convalescent plasma recipient antibody thresholds correlated to reduced hospitalizations within a randomized trial.

BACKGROUND: The COVID-19 convalescent plasma (CCP) viral specific antibody levels that translate into recipient post-transfusion antibody levels sufficient to prevent disease progression is not defined. METHODS: This secondary analysis correlated donor and recipient antibody levels to hospitalization risk among unvaccinated, seronegative CCP recipients within the outpatient, double blind, randomized clinical trial that compared CCP to control plasma. The majority of COVID-19 CCP arm hospitalizations (15/17, 88%) occurred in this unvaccinated, seronegative subgroup. A functional cutoff to delineate recipient high versus low post-transfusion antibody levels was established by two methods: 1) analyzing virus neutralization-equivalent anti-S-RBD IgG responses in donors or 2) receiver operating characteristic (ROC) analysis. RESULTS: SARS-CoV-2 anti-S-RBD IgG antibody was diluted by a factor of 21.3 into post-transfusion seronegative recipients from matched donor units. Viral specific antibody delivered approximated 1.2 mg. The high antibody recipients transfused early (symptom onset within 5 days) had no hospitalizations. A CCP recipient analysis for antibody thresholds correlated to reduced hospitalizations found a significant association with Fisher's exact test between early and high antibodies versus all other CCP recipients (or control plasma) with antibody cutoffs established by both methods-donor virus neutralization-based cutoff: (0/85; 0% versus 15/276; 5.6%) p=0.03 or ROC based cutoff: (0/94; 0% versus 15/267; 5.4%) p=0.01. CONCLUSION: In unvaccinated, seronegative CCP recipients, early transfusion of plasma units corresponding to the upper 30% of all study donors reduced outpatient hospitalizations. These high antibody level plasma units, given early, should be reserved for therapeutic use.Trial registration: NCT04373460. FUNDING: Defense Health Agency and others.

Early Treatment, Inflammation and Post-COVID Conditions.

Background: Post-COVID conditions (PCC) are common and have significant morbidity. Risk factors for PCC include advancing age, female sex, obesity, and diabetes mellitus. Little is known about early treatment, inflammation, and PCC. Methods: Among 883 individuals with confirmed SARS-CoV-2 infection participating in a randomized trial of CCP vs. control plasma with available biospecimens and symptom data, the association between early COVID treatment, cytokine levels and PCC was evaluated. Cytokine and chemokine levels were assessed at baseline, day 14 and day 90 using a multiplexed sandwich immuosassay (Mesoscale Discovery). Presence of any self-reported PCC symptoms was assessed at day 90. Associations between COVID treatment, cytokine levels and PCC were examined using multivariate logistic regression models. Results: One-third of the 882 participants had day 90 PCC symptoms, with fatigue (14.5%) and loss of smell (14.5%) being most common. Cytokine levels decreased from baseline to day 90. In a multivariable analysis including diabetes, body mass index, race, and vaccine status, female sex (adjusted odds ratio[AOR]=2.70[1.93-3.81]), older age (AOR=1.32[1.17-1.50]), and elevated baseline levels of IL-6 (AOR=1.59[1.02-2.47]) were associated with development of PCC.There was a trend for decreased PCC in those with early CCP treatment (≤5 days after symptom onset) compared to late CCP treatment. Conclusion: Increased IL-6 levels were associated with the development of PCC and there was a trend for decreased PCC with early CCP treatment in this predominately unvaccinated population. Future treatment studies should evaluate the effect of early treatment and anti-IL-6 therapies on PCC development.

Vaccination against SARS-CoV-2 using extracellular blebs derived from spike protein-expressing dendritic cells.

COVID-19 has caused significant morbidity and mortality worldwide but also accelerated the clinical use of emerging vaccine formulations. To address the current shortcomings in the prevention and treatment of SARS-CoV-2 infection, this study developed a novel vaccine platform that closely mimics dendritic cells (DCs) in antigen presentation and T-cell stimulation in a cell-free and tunable manner. Genetically engineered DCs that express the SARS-CoV-2 spike protein (S) were chemically converted into extracellular blebs (EBs). The resulting EBs elicited potentially protective humoral immunity in vivo, indicated by the production of antibodies that potently neutralized S-pseudotyped virus, presenting EBs as a promising and safe vaccine.

Prevention and Treatment of Monkeypox.

Human monkeypox is a zoonotic orthopoxvirus with presentation similar to smallpox. Monkeypox is transmitted incidentally to humans when they encounter infected animals. Reports have shown that the virus can also be transmitted through direct contact (sexual or skin-to-skin), respiratory droplets, and via fomites such as towels and bedding. Multiple medical countermeasures are stockpiled for orthopoxviruses such as monkeypox. Two vaccines are currently available, JYNNEOSTM (live, replication incompetent vaccinia virus) and ACAM2000® (live, replication competent vaccinia virus). While most cases of monkeypox will have mild and self-limited disease, with supportive care being typically sufficient, antivirals (e.g. tecovirimat, brincidofovir, cidofovir) and vaccinia immune globulin intravenous (VIGIV) are available as treatments. Antivirals can be considered in severe disease, immunocompromised patients, pediatrics, pregnant and breastfeeding women, complicated lesions, and when lesions appear near the mouth, eyes, and genitals. The purpose of this short review is to describe each of these countermeasures.

Association between vaccine preventable diseases in children and improved sanitation following a nationwide sanitation campaign in India: an ecological analysis.

OBJECTIVE: Persistent exposure to faecal pathogens due to open defecation may cause environmental enteropathy that, in turn, may lead to undernutrition and vaccine failure in under 5-year-old (u5) children. The Swachh Bharat Mission (SBM) programme in India, launched in 2014, aimed to construct toilets for every household nationwide and reduce open defecation. This programme, if successful, had the potential to reduce the burden of four vaccine preventable diseases (VPDs): diphtheria, pertussis, tetanus and measles. We examine whether increased household toilet availability in Indian districts following SBM corresponds with a reduction in diphtheria, pertussis, tetanus and measles in u5 children. DESIGN: Observational, ecological study. SETTING: 532 districts in 28 Indian states, from 2013 to 2016. PRIMARY OUTCOME AND EXPOSURE: We retrieved data on district-level change in the annual incidence (per 1000 u5 children) of four VPDs, from 2013 (pre-SBM) to 2016 (post-SBM). We obtained data on our exposure, the change in the percentage of households with toilets (per district), from three large national surveys conducted in 2013 and 2016. We used linear regression analysis, which controlled for change over time in socioeconomic factors, health system-related covariates and pre-SBM annual incidence of VPDs. RESULTS: A one percentage point increase in households with toilets corresponds with 0.33 fewer measle cases per 1000 u5 children in a district (coefficient: -0.33, 95% CI -0.0641 to -0.014; p<0.05). About 12% of this association is mediated by a reduction in u5 stunting. We observe no relation of the exposure with diphtheria, pertussis or tetanus. Findings remain robust to sensitivity analyses. CONCLUSION: Rapid improvements in ambient sanitation through increased toilet availability correspond with a reduction in the annual incidence of measles in u5 children. We encourage replication of findings and further research to identify potential pathways by which SBM may reduce measle burden in u5 children.

Early Outpatient Treatment for Covid-19 with Convalescent Plasma.

BACKGROUND: Polyclonal convalescent plasma may be obtained from donors who have recovered from coronavirus disease 2019 (Covid-19). The efficacy of this plasma in preventing serious complications in outpatients with recent-onset Covid-19 is uncertain. METHODS: In this multicenter, double-blind, randomized, controlled trial, we evaluated the efficacy and safety of Covid-19 convalescent plasma, as compared with control plasma, in symptomatic adults (≥18 years of age) who had tested positive for severe acute respiratory syndrome coronavirus 2, regardless of their risk factors for disease progression or vaccination status. Participants were enrolled within 8 days after symptom onset and received a transfusion within 1 day after randomization. The primary outcome was Covid-19-related hospitalization within 28 days after transfusion. RESULTS: Participants were enrolled from June 3, 2020, through October 1, 2021. A total of 1225 participants underwent randomization, and 1181 received a transfusion. In the prespecified modified intention-to-treat analysis that included only participants who received a transfusion, the primary outcome occurred in 17 of 592 participants (2.9%) who received convalescent plasma and 37 of 589 participants (6.3%) who received control plasma (absolute risk reduction, 3.4 percentage points; 95% confidence interval, 1.0 to 5.8; P = 0.005), which corresponded to a relative risk reduction of 54%. Evidence of efficacy in vaccinated participants cannot be inferred from these data because 53 of the 54 participants with Covid-19 who were hospitalized were unvaccinated and 1 participant was partially vaccinated. A total of 16 grade 3 or 4 adverse events (7 in the convalescent-plasma group and 9 in the control-plasma group) occurred in participants who were not hospitalized. CONCLUSIONS: In participants with Covid-19, most of whom were unvaccinated, the administration of convalescent plasma within 9 days after the onset of symptoms reduced the risk of disease progression leading to hospitalization. (Funded by the Department of Defense and others; CSSC-004 ClinicalTrials.gov number, NCT04373460.).

Internalization of HIV-1 by Phagocytes Is Increased When Virions Are Opsonized with Multimeric Antibody in the Presence of Complement.

The low abundance of envelope spikes and the inability of IgG to aggregate virions render HIV-1 an inadequate target for antibody-mediated clearance by phagocytes. In an attempt to improve the ability of antibody to mediate the internalization of HIV-1 virions, we generated multimers of the broadly neutralizing HIV-1-specific monoclonal antibody (MAb) VRC01 using site-directed mutagenesis of the Fc segment. We then measured virion internalization using primary human monocytes and neutrophils. We found that, in the absence of complement, immune complexes consisting of HIV-1 virions and VRC01 multimers were slightly more efficiently internalized than were complexes formed with monomeric VRC01. The presence of complement, however, greatly augmented internalization of immune complexes formed with the multimeric MAb but had little impact on monomeric MAb-mediated internalization. Multimerization and the presence of complement overcome the limited ability of monomeric antibody to mediate internalization of HIV-1 virions and may thus provide a therapeutic approach to clearing virus. IMPORTANCE Antibody-mediated internalization of HIV-1 by phagocytes, a potential mechanism for clearing virus, is very inefficient. In an effort to improve viral clearance, we produced a multimeric form of the broadly neutralizing monoclonal antibody VRC01. We found that VRC01 antibody multimers (primarily hexamers) were only slightly more efficient in mediating HIV-1 internalization than was monomeric VRC01. However, the addition of complement resulted in substantially greater internalization of multimer-opsonized virus. In contrast, complement had little if any impact on internalization of monomer-opsonized virus. Therefore, antibody multimerization in combination with complement may overcome the limited ability of monomeric antibody to mediate internalization of HIV-1 virions. Our findings may provide a therapeutic approach to clearing virus.

Diverse antiviral IgG effector activities are predicted by unique biophysical antibody features.

BACKGROUND: The critical role of antibody Fc-mediated effector functions in immune defense has been widely reported in various viral infections. These effector functions confer cellular responses through engagement with innate immune cells. The precise mechanism(s) by which immunoglobulin G (IgG) Fc domain and cognate receptors may afford protection are poorly understood, however, in the context of HIV/SHIV infections. Many different in vitro assays have been developed and utilized to measure effector functions, but the extent to which these assays capture distinct antibody activities has not been fully elucidated. RESULTS: In this study, six Fc-mediated effector function assays and two biophysical antibody profiling assays were performed on a common set of samples from HIV-1 infected and vaccinated subjects. Biophysical antibody profiles supported robust prediction of diverse IgG effector functions across distinct Fc-mediated effector function assays. While a number of assays showed correlated activities, supervised machine learning models indicated unique antibody features as primary contributing factors to the associated effector functions. Additional experiments established the mechanistic relevance of relationships discovered using this unbiased approach. CONCLUSIONS: In sum, this study provides better resolution on the diversity and complexity of effector function assays, offering a clearer perspective into this family of antibody mechanisms of action to inform future HIV-1 treatment and vaccination strategies.

Virus Control in Vaccinated Rhesus Macaques Is Associated with Neutralizing and Capturing Antibodies against the SHIV Challenge Virus but Not with V1V2 Vaccine-Induced Anti-V2 Antibodies Alone.

The role of vaccine-induced anti-V2 Abs was tested in three protection experiments in rhesus macaques. In an experiment using immunogens similar to those in the RV144 vaccine trial (Anti-envelope [Env]), nine rhesus macaques were coimmunized with gp16092TH023 DNA and SIV gag and gp120A244 and gp120MN proteins. In two V2-focused experiments (Anti-V2 and Anti-V2 Mucosal), nine macaques in each group were immunized with V1V292TH023 DNA, V1V2A244 and V1V2CasaeA2 proteins, and cyclic V2CaseA2 peptide. DNA and protein immunogens, formulated in Adjuplex, were given at 0, 4, 12, and 20 weeks, followed by intrarectal SHIVBaL.P4 challenges. Peak plasma viral loads (PVL) of 106-107 copies/ml developed in all nine sham controls. Overall, PVL was undetectable in one third of immunized macaques, and two animals tightly controlled the virus with the Anti-V2 Mucosal vaccine strategy. In the Anti-Env study, Abs that captured or neutralized SHIVBaL.P4 inversely correlated with PVL. Conversely, no correlation with PVL was found in the Anti-V2 experiments with nonneutralizing plasma Abs that only captured virus weakly. Titers of Abs against eight V1V2 scaffolds and cyclic V2 peptides were comparable between controllers and noncontrollers as were Ab-dependent cellular cytotoxicity and Ab-dependent cell-mediated virus inhibition activities against SHIV-infected target cells and phagocytosis of gp120-coated beads. The Anti-Env experiment supports the role of vaccine-elicited neutralizing and nonneutralizing Abs in control of PVL. However, the two V2-focused experiments did not support a role for nonneutralizing V2 Abs alone in controlling PVL, as neither Ab-dependent cellular cytotoxicity, Ab-dependent cell-mediated virus inhibition, nor phagocytosis correlated inversely with heterologous SHIVBaL.P4 infection.