Inhibition of rhinovirus attachment by neutralizing monoclonal antibodies and their Fab fragments

Abstract

Previous molecular and immunological studies have mapped four neutralization sites on human rhinovirus type 14 (B. Sherry, A. G. Mosser, R. J. Colonno, and R. R. Rueckert, J. Virol. 57:246-257, 1986). Eight monoclonal antibodies, one pair for each of the four target sites and all belonging to a single isotype, immunoglobulin G2a, were studied under conditions which resulted in 95% neutralization of infectious viral particles. All eight antibodies shifted the isoelectric point of virions from 6.7 to much more acidic forms, ranging from pl 1.8 to 3.2. In addition, antibodies targeted against three of the four neutralization sites caused significant aggregation of virions under the neutralization conditions employed. Aggregation could be reversed by digesting virus-antibody complexes with papain. Following papain digestion, the acidic pls of three of the neutralized virus preparations returned to neutral and infectivity was restored. Membrane-binding assays with virus neutralized with a nonaggregating antibody showed a dose-related inhibition of virus attachment to cellular receptors. Purified Fab fragments at a 13to 61-fold-higher concentration than intact antibodies caused a comparable isoelectric shift, neutralized virions in the absence of aggregation, and interfered with attachment of virions to host cell receptors in a membrane-binding assay. These findings suggest that neutralizing antibodies interfere with the attachment of rhinoviruses to cellular receptors and that bivalent attachment of antibody is not a prerequisite for neutralization.on July 6, 2020 by guest

Antibody-Mediated Neutralization of Human Rhinovirus 14 Explored by Means of Cryoelectron Microscopy and X-Ray Crystallography of Virus-Fab Complexes

“…This limited range has raised questions about the role of aggregation in vivo. Alternative suggestions are that antibodies may neutralize virions by inducing extensive conformational changes in the capsid (15,29), abrogate virus attachment to the host cell (8,14), or prevent uncoating (57). There is no universal acceptance of a single neutralization mechanism, and the various MAbs may neutralize with different combinations of these mechanisms.…”

Efficient neutralization of foot-and-mouth disease virus by monovalent antibody binding

“…However, a very weakly neutralizing MAb against rhinovirus type 2 displayed also bivalent binding to the virus capsid (10,32). A strongly neutralizing MAb against rhinovirus 14 bound bivalently, and its purified Fab fragment required concentrations 13-to 61fold higher than those for the intact antibody to achieve a comparable neutralization (4). Colonno et al concluded that bivalent binding is not a prerequisite for neutralization (4).…”

Structural studies on the mechanisms of antibody-mediated neutralization of human rhinovirus

“…13 The popular model based upon these observations was that the binding of a single antibody molecule caused a concerted conformational change in the virus capsid that abolished infectivity and changed the surface charge. The two phenomena have been repeatedly confirmed for picornaviruses, 14,15 although the causal relationship between the pI shift and neutralization has been questioned. 16,17 Studies have shown that Fab fragments and intact antibodies can block attachment, 14,15 prevent disappearance of virus from the cell surface, 14 and block the first stage in viral uncoating.…”

“…16,17 Studies have shown that Fab fragments and intact antibodies can block attachment, 14,15 prevent disappearance of virus from the cell surface, 14 and block the first stage in viral uncoating. 18 Antibodies might also trap the virus in a non-infectious form, 15 stabilize poliovirus capsids against the disrupting affects of hypotonic 19 and acidic buffers, 20 and prevent the appearance of intact viral RNA in cells. 21…”

“…23 mAb17-IA was chosen for structural studies because it also induced a pI shift in the capsid. 15 The aim of these studies was to examine the binding contacts between antibody and virus and to see if the antibody induces conformational changes in the capsid.…”