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Global panel of HIV-1 Env reference strains for standardized assessments of vaccine-elicited neutralizing antibodies.

ABSTRACT: Standardized assessments of HIV-1 vaccine-elicited neutralizing antibody responses are complicated by the genetic and antigenic variability of the viral envelope glycoproteins (Envs). To address these issues, suitable reference strains are needed that are representative of the global epidemic. Several panels have been recommended previously, but no clear answers have been available on how many and which strains are best suited for this purpose. We used a statistical model selection method to identify a global panel of reference Env clones from among 219 Env-pseudotyped viruses assayed in TZM-bl cells with sera from 205 HIV-1-infected individuals. The Envs and sera were sampled globally from diverse geographic locations and represented all major genetic subtypes and circulating recombinant forms of the virus. Assays with a panel size of only nine viruses adequately represented the spectrum of HIV-1 serum neutralizing activity seen with the larger panel of 219 viruses. An optimal panel of nine viruses was selected and augmented with three additional viruses for greater genetic and antigenic coverage. The spectrum of HIV-1 serum neutralizing activity seen with the final 12-virus panel closely approximated the activity seen with subtype-matched viruses. Moreover, the final panel was highly sensitive for detection of many of the known broadly neutralizing antibodies. For broader assay applications, all 12 Env clones were converted to infectious molecular clones using a proviral backbone carrying a Renilla luciferase reporter gene (Env.IMC.LucR viruses). This global panel should facilitate highly standardized assessments of vaccine-elicited neutralizing antibodies across multiple HIV-1 vaccine platforms in different parts of the world.An effective HIV-1 vaccine will need to overcome the extraordinary genetic variability of the virus, where most variation occurs in the viral envelope glycoproteins that are the sole targets for neutralizing antibodies. Efforts to elicit broadly cross-reactive neutralizing antibodies that will protect against infection by most circulating strains of the virus are guided in part by in vitro assays that determine the ability of vaccine-elicited antibodies to neutralize genetically diverse HIV-1 variants. Until now, little information was available on how many and which strains of the virus are best suited for this purpose. We applied robust statistical methods to evaluate a large neutralization data set and identified a small panel of viruses that are a good representation of the global epidemic. The neutralization properties of this new panel of reference strains should facilitate the development of an effective HIV-1 vaccine.

SUBMITTER: deCamp A

PROVIDER: S-EPMC3958090 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Global panel of HIV-1 Env reference strains for standardized assessments of vaccine-elicited neutralizing antibodies.

deCamp Allan A Hraber Peter P Bailer Robert T RT Seaman Michael S MS Ochsenbauer Christina C Kappes John J Gottardo Raphael R Edlefsen Paul P Self Steve S Tang Haili H Greene Kelli K Gao Hongmei H Daniell Xiaoju X Sarzotti-Kelsoe Marcella M Gorny Miroslaw K MK Zolla-Pazner Susan S LaBranche Celia C CC Mascola John R JR Korber Bette T BT Montefiori David C DC

Journal of virology 20131218 5

<h4>Unlabelled</h4>Standardized assessments of HIV-1 vaccine-elicited neutralizing antibody responses are complicated by the genetic and antigenic variability of the viral envelope glycoproteins (Envs). To address these issues, suitable reference strains are needed that are representative of the global epidemic. Several panels have been recommended previously, but no clear answers have been available on how many and which strains are best suited for this purpose. We used a statistical model sele ...[more]

PMID: 24352443

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Project description:In the search for effective immunologic interventions to prevent and treat HIV-1 infection, standardized reference reagents are a cost-effective way to maintain robustness and reproducibility among immunological assays. To support planned and ongoing studies where clade C predominates, here we describe three virus panels, chosen from 200 well-characterized clade C envelope (Env)-pseudotyped viruses from early infection. All 200 Envs were expressed as a single round of replication pseudoviruses and were tested to quantify neutralization titers by 16 broadly neutralizing antibodies (bnAbs) and sera from 30 subjects with chronic clade C infections. We selected large panels of 50 and 100 Envs either to characterize cross-reactive breadth for sera identified as having potent neutralization activity based on initial screening or to evaluate neutralization magnitude-breadth distributions of newly isolated antibodies. We identified these panels by downselection after hierarchical clustering of bnAb neutralization titers. The resulting panels represent the diversity of neutralization profiles throughout the range of virus sensitivities identified in the original panel of 200 viruses. A small 12-Env panel was chosen to screen sera from vaccine trials or natural-infection studies for neutralization responses. We considered panels selected by previously described methods but favored a computationally informed method that enabled selection of viruses representing diverse neutralization sensitivity patterns, given that we do not a priori know what the neutralization-response profile of vaccine sera will be relative to that of sera from infected individuals. The resulting 12-Env panel complements existing panels. Use of standardized panels enables direct comparisons of data from different trials and study sites testing HIV-1 clade C-specific products.IMPORTANCE HIV-1 group M includes nine clades and many recombinants. Clade C is the most common lineage, responsible for roughly half of current HIV-1 infections, and is a focus for vaccine design and testing. Standard reference reagents, particularly virus panels to study neutralization by antibodies, are crucial for developing cost-effective and yet rigorous and reproducible assays against diverse examples of this variable virus. We developed clade C-specific panels for use as standardized reagents to monitor complex polyclonal sera for neutralization activity and to characterize the potency and breadth of cross-reactive neutralization by monoclonal antibodies, whether engineered or isolated from infected individuals. We chose from 200 southern African, clade C envelope-pseudotyped viruses with neutralization titers against 16 broadly neutralizing antibodies and 30 sera from chronic clade C infections. We selected panels to represent the diversity of bnAb neutralization profiles and Env neutralization sensitivities. Use of standard virus panels can facilitate comparison of results across studies and sites.

Project description:Antibody-dependent cellular cytotoxicity (ADCC) has been correlated with reduced risk of human immunodeficiency virus type 1 (HIV-1) infection in several preclinical vaccine trials and in the RV144 clinical trial, indicating that this is a relevant antibody function to study. Given the diversity of HIV-1, the breadth of vaccine-induced antibody responses is a critical parameter to understand if a universal vaccine is to be realized. Moreover, the breadth of ADCC responses can be influenced by different vaccine strategies and regimens, including adjuvants. Therefore, to accurately evaluate ADCC and to compare vaccine regimens, it is important to understand the range of HIV Envelope (Env) susceptibility to these responses. These evaluations have been limited because of the complexity of the assay and the lack of a comprehensive panel of viruses for the assessment of these humoral responses. Here, we used 29 HIV-1 infectious molecular clones (IMCs) representing different Envelope subtypes and circulating recombinant forms to characterize susceptibility to ADCC from antibodies in plasma from infected individuals, including 13 viremic individuals, 10 controllers, and six with broadly neutralizing antibody responses. We found in our panel that ADCC susceptibility of the IMCs in our panel did not cluster by subtype, infectivity, level of CD4 downregulation, level of shedding, or neutralization sensitivity. Using partitioning around medoids (PAM) clustering to distinguish smaller groups of IMCs with similar ADCC susceptibility, we identified nested panels of four to eight IMCs that broadly represent the ADCC susceptibility of the entire 29-IMC panel. These panels, together with reagents developed to specifically accommodate circulating viruses at the geographical sites of vaccine trials, will provide a powerful tool to harmonize ADCC data generated across different studies and to detect common themes of ADCC responses elicited by various vaccines. IMPORTANCE Antibody-dependent cellular cytotoxicity (ADCC) responses were found to correlate with reduced risk of infection in the RV144 trial of the only human HIV-1 vaccine to show any efficacy to date. However, reagents to understand the breadth and magnitude of these responses across preclinical and clinical vaccine trials remain underdeveloped. In this study, we characterize HIV-1 infectious molecular clones encoding 29 distinct Envelope strains (Env-IMCs) to understand factors that impact virus susceptibility to ADCC and use statistical methods to identify smaller nested panels of four to eight Env-IMCs that accurately represent the full set. These reagents can be used as standardized reagents across studies to fully understand how ADCC may affect efficacy of future vaccine studies and how studies differ in the breadth of responses developed.

Project description:The increasing prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with spike protein mutations raises concerns that antibodies elicited by natural infection or vaccination and therapeutic monoclonal antibodies will become less effective. We show that convalescent-phase sera neutralize pseudotyped viruses with the B.1.1.7, B.1.351, B.1.1.248, COH.20G/677H, 20A.EU2, and mink cluster 5 spike proteins with only a minor loss in titer. Similarly, antibodies elicited by Pfizer BNT162b2 vaccination neutralized B.1.351 and B.1.1.248 with only a 3-fold decrease in titer, an effect attributable to E484K. Analysis of the Regeneron monoclonal antibodies REGN10933 and REGN10987 showed that REGN10933 has lost neutralizing activity against the B.1.351 and B.1.1.248 pseudotyped viruses, and the cocktail is 9- to 15-fold decreased in titer. These findings suggest that antibodies elicited by natural infection and by the Pfizer vaccine will maintain protection against the B.1.1.7, B.1.351, and B.1.1.248 variants but that monoclonal antibody therapy may be less effective for patients infected with B.1.351 or B.1.1.248 SARS-CoV-2. IMPORTANCE The rapid evolution of SARS-CoV-2 variants has raised concerns with regard to their potential to escape from vaccine-elicited antibodies and anti-spike protein monoclonal antibodies. We report here on an analysis of sera from recovered patients and vaccinated individuals and on neutralization by Regeneron therapeutic monoclonal antibodies. Overall, the variants were neutralized nearly as well as the wild-type pseudotyped virus. The B.1.351 variant was somewhat resistant to vaccine-elicited antibodies but was still readily neutralized. One of the two Regeneron therapeutic monoclonal antibodies seems to have lost most of its activity against the B.1.351 variant, raising concerns that the combination therapy might be less effective for some patients. The findings should alleviate concerns that vaccines will become ineffective but suggest the importance of continued surveillance for potential new variants.

Project description:The trimeric envelope glycoproteins (Env) on the surface of HIV-1 virions are the targets for neutralizing antibodies (NAbs). No candidate HIV-1 immunogen has yet induced potent, broadly active NAbs (bNAbs). Part of the explanation may be that previously tested Env proteins inadequately mimic the functional, native Env complex. Trimerization and the proteolytic processing of Env precursors into gp120 and gp41 profoundly alter antigenicity, but soluble cleaved trimers are too unstable to serve as immunogens. By introducing stabilizing mutations (SOSIP), we constructed soluble, cleaved Env trimers derived from the HIV-1 subtype A isolate BG505 that resemble native Env spikes on virions both structurally and antigenically.We used surface plasmon resonance (SPR) to quantify antibody binding to different forms of BG505 Env: the proteolytically cleaved SOSIP.664 trimers, cleaved gp120-gp41ECTO protomers, and gp120 monomers. Non-NAbs to the CD4-binding site bound only marginally to the trimers but equally well to gp120-gp41ECTO protomers and gp120 monomers, whereas the bNAb VRC01, directed to the CD4bs, bound to all three forms. In contrast, bNAbs to V1V2 glycan-dependent epitopes bound preferentially (PG9 and PG16) or exclusively (PGT145) to trimers. We also explored the antigenic consequences of three different features of SOSIP.664 gp140 trimers: the engineered inter-subunit disulfide bond, the trimer-stabilizing I559P change in gp41ECTO, and proteolytic cleavage at the gp120-gp41ECTO junction. Each of these three features incrementally promoted native-like trimer antigenicity. We compared Fab and IgG versions of bNAbs and validated a bivalent model of IgG binding. The NAbs showed widely divergent binding kinetics and degrees of binding to native-like BG505 SOSIP.664. High off-rate constants and low stoichiometric estimates of NAb binding were associated with large amounts of residual infectivity after NAb neutralization of the corresponding BG505.T332N pseudovirus.The antigenicity and structural integrity of cleaved BG505 SOSIP.664 trimers render these proteins good mimics of functional Env spikes on virions. In contrast, uncleaved gp140s antigenically resemble individual gp120-gp41ECTO protomers and gp120 monomers, but not native trimers. Although NAb binding to functional trimers may thus be both necessary and sufficient for neutralization, the kinetics and stoichiometry of the interaction influence the neutralizing efficacy of individual NAbs.

Dataset Information

Global panel of HIV-1 Env reference strains for standardized assessments of vaccine-elicited neutralizing antibodies.

Publications

Global panel of HIV-1 Env reference strains for standardized assessments of vaccine-elicited neutralizing antibodies.

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