Potent and broad neutralizing activity of a single chain antibody fragment against cell-free and cell-associated HIV-1.
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2010-05
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Abstract
Several human monoclonal antibodies (hmAbs) exhibit relatively potent and broad neutralizing activity against HIV-1, but there has not been much success in using them as potential therapeutics. We have previously hypothesized and demonstrated that small engineered antibodies can target highly conserved epitopes that are not accessible by full-size antibodies. However, their potency has not been comparatively evaluated with known HIV-1-neutralizing hmAbs against large panels of primary isolates. We report here the inhibitory activity of an engineered single chain antibody fragment (scFv), m9, against several panels of primary HIV-1 isolates from group M (clades A-G) using cell-free and cell-associated virus in cell line-based assays. M9 was much more potent than scFv 17b, and more potent than or comparable to the best-characterized broadly neutralizing hmAbs IgG(1) b12, 2G12, 2F5 and 4E10. It also inhibited cell-to-cell transmission of HIV-1 with higher potency than enfuvirtide (T-20, Fuzeon). M9 competed with a sulfated CCR5 N-terminal peptide for binding to gp120-CD4 complex, suggesting an overlapping epitope with the coreceptor binding site. M9 did not react with phosphatidylserine (PS) and cardiolipin (CL), nor did it react with a panel of autoantigens in an antinuclear autoantibody (ANA) assay. We further found that escape mutants resistant to m9 did not emerge in an immune selection assay. These results suggest that m9 is a novel anti-HIV-1 candidate with potential therapeutic or prophylactic properties, and its epitope is a new target for drug or vaccine development.
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Scholars@Duke
S. Munir Alam
Research Interests.
The Alam laboratory’s primary research is focused on understanding the biophysical properties of antigen-antibody binding and the molecular events of early B cell activation using the HIV-1 broadly neutralizing antibody (bnAb) lineage models. We are studying how HIV-1 Envelope proteins of varying affinities are sensed by B cells expressing HIV-1 bnAbs or their germline antigen receptors and initiate early signaling events for their activation. In the long-term these studies will facilitate design and pre-selection of immunogens for testing in animal models and accelerate HIV-1 vaccine development.
Current research include the following NIAID-funded projects
Antigen recognition and activation of B cell antigen receptors with the specificity of HIV-1 broadly neutralizing antibodies. This project involves elucidating the early events on the B cell surface following antigen (Ag) engagement of the B cell antigen receptor (BCR) and to provide an assessment of the in vivo potential of an Ag to drive B cell activation. We are performing biophysical interactions analyses and using high-resolution microscopy to define the physico-chemical properties of BCR-Ag interactions that govern signaling and activation thresholds for BCR triggering and the BCR endocytic function in antigen internalization. The overall objective of these studies is to bridge the quantitative biophysical and membrane dynamics measurements of Ag-BCR interactions to ex-vivo and in-vivo B cell activation. This NIAID-funded research is a collaboration with co-investigators Professor Michael Reth (University of Freiburg, Germany) and Dr. Laurent Verkoczy (San Diego Biomedical Research Institute, CA).
Immunogen Design for Induction of HIV gp41 Broadly Neutralizing Antibodies. This research project addresses the critical problem of vaccine induction of disfavored HIV-1 antibody lineages, like those that target the membrane proximal external region (MPER) of HIV Env gp41. This program combines structure and lineage-based vaccine development strategies to design immunogens that will induce bnAb lineages that are not polyreactive and therefore easier to induce. The overall objective of this program grant is to develop and test sequential immunogens that will initiate and induce HIV-1 bnAb lineages like the potent MPER bnAb DH511. Using a germline-targeting (GT) epitope scaffold design and a prime/boost strategy, we are testing induction of DH511-like bnAbs in knock-in (KI) mice models expressing the DH511 germline receptors. This P01 research program is in collaboration with Dr. William Schief (The Scripps Research Institute, CA), who leads the team that are designing germline targeting (GT)-scaffold prime and boost immunogens and Dr. Ming Tian at Harvard University who developed relevant knock-mice models for the study.
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