Inhibition of HIV Env binding to cellular receptors by monoclonal antibody 2G12 as probed by Fc-tagged gp120.

Torrey Pines Institute for Molecular Studies, 3550 General Atomics Court, San Diego CA 92121, USA.
Retrovirology (Impact Factor: 4.77). 02/2006; 3:39. DOI: 10.1186/1742-4690-3-39
Source: PubMed

ABSTRACT During natural HIV infection, an array of host receptors are thought to influence virus attachment and the kinetics of infection. In this study, to probe the interactions of HIV envelope (Env) with various receptors, we assessed the inhibitory properties of various anti-Env monoclonal antibodies (mAbs) in binding assays. To assist in detecting Env in attachment assays, we generated Fc fusions of full-length wild-type gp120 and several variable loop-deleted gp120s. Through investigation of the inhibition of Env binding to cell lines expressing CD4, CCR5, DC-SIGN, syndecans or combinations thereof, we found that the broadly neutralizing mAb, 2G12, directed to a unique carbohydrate epitope of gp120, inhibited Env-CCR5 binding, partially inhibited Env-DC-SIGN binding, but had no effect on Env-syndecan association. Furthermore, 2G12 inhibited Env attachment to primary monocyte-derived dendritic cells, that expressed CD4 and CCR5 primary HIV receptors, as well as DC-SIGN, and suggested that the dual activities of 2G12 could be valuable in vivo for inhibiting initial virus dissemination and propagation.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The application of Fc (fragment crystallizable)-based cytokines (the fusion of the constant region of IgG to a cytokine of interest) as biotherapeutic agents to modulate inflammatory and immune responses has become increasingly popular in recent years. This is because in their monomeric form, cytokines are relatively small molecules with short serum half-lives, which necessitates frequent administration and thus limits their clinical utility. To rectify the problem, attempts have been made to improve the stability of these agents in vivo. This has been achieved through diverse strategies such as modification with polyethylene glycol (PEGylation) or by ligating the cytokine to protein moieties such as the constant heavy chain of IgG, known as the Fc fragment. The construction of Fc chimeric proteins has been shown to improve pharmacokinetics. However, since there is an inverse relationship between the size of molecules and the rate at which they diffuse through mucus, Fc fusion constructs potentially have a lower rate of diffusion. Consequently, a compromise is reached whereby Fc constructs are engineered to incorporate ligated cytokines in a monomeric form (one molecule of cytokine fused to a single Fc dimer) rather than in a dimeric form (two molecules of cytokine fused to a single Fc dimer). A recent and novel approach to improve stability in serum is a procedure that involves sheathing cytokines in protective protein covers called latency peptides. The enclosed cytokine is protected from degradation and allowed to act where needed when the outer peptide cover is removed. For some applications, a reduced serum half-life is desirable; for example, where there is a need to reduce IgG levels in antibody-mediated diseases. To achieve this goal, a strategy called AbDeg, which involves enhanced Ig degradation, has been devised. This article provides an overview of the design and construction of Fc-based cytokines, in both dimeric and monomeric forms. Several examples of recent applications of such constructs, which include cytokine antagonism, cytokine traps, gene therapy and drug delivery, are also discussed. Other antibody-engineered constructs such as Fab (fragment, antigen binding) and single chain Fv (fragment, variable) fusions are also briefly covered.
    BioDrugs 01/2008; 22(1). DOI:10.2165/00063030-200822010-00002 · 2.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Breastfeeding is a leading cause of infant HIV-1 infection in the developing world, yet only a minority of infants exposed to HIV-1 via breastfeeding become infected. As a genetic bottleneck severely restricts the number of postnatally-transmitted variants, genetic or phenotypic properties of the virus Envelope (Env) could be important for the establishment of infant infection. We examined the efficiency of virologic functions required for initiation of infection in the gastrointestinal tract and the neutralization sensitivity of HIV-1 Env variants isolated from milk of three postnatally-transmitting mothers (n=13 viruses), five clinically-matched nontransmitting mothers (n=16 viruses), and seven postnatally-infected infants (n = 7 postnatally-transmitted/founder (T/F) viruses). RESULTS: There was no difference in the efficiency of epithelial cell interactions between Env virus variants from the breast milk of transmitting and nontransmitting mothers. Moreover, there was similar efficiency of DC-mediated trans-infection, CCR5-usage, target cell fusion, and infectivity between HIV-1 Env-pseudoviruses from nontransmitting mothers and postnatal T/F viruses. Milk Env-pseudoviruses were generally sensitive to neutralization by autologous maternal plasma and resistant to breast milk neutralization. Infant T/F Env-pseudoviruses were equally sensitive to neutralization by broadly-neutralizing monoclonal and polyclonal antibodies as compared to nontransmitted breast milk Env variants. CONCLUSION: Postnatally-T/F Env variants do not appear to possess a superior ability to interact with and cross a mucosal barrier or an exceptional resistance to neutralization that define their capability to initiate infection across the infant gastrointestinal tract in the setting of preexisting maternal antibodies.
    Retrovirology 01/2013; 10(1):3. DOI:10.1186/1742-4690-10-3 · 4.77 Impact Factor
  • Source

Full-text (3 Sources)

Available from
May 20, 2014