Abstract
Mabs H36 (IgG2a) and H37 (IgG3) recognize epitopes in antigenic sites Sb and Ca2, respectively, in the HA1 subunit of influenza virus A/PR/8/34 (H1N1). Their neutralization was complex. Our aim here was to investigate the mechanism of neutralization by the IgGs and their Fabs. In MDCK and BHK cells, both IgGs neutralized primarily by inhibiting virus–cell fusion, although at higher IgG concentrations virus attachment to target cells was also inhibited. In contrast, the Fabs neutralized entirely by inhibiting virus attachment, although a higher concentration of Fab than IgG was required to bring this about. Both H36 and H37 exerted a concentration-dependent spectrum of neutralization activity, with virus–cell fusion inhibition and virus–cell attachment inhibition being the predominant mechanisms at low- and high-antibody concentration, respectively, and both mechanisms occurring simultaneously at intermediate concentrations. However, it may be that attachment inhibition was a secondary event, occurring to virus that had already been neutralized through inhibition of its fusion activity. Neutralization by H36 and H37 Fabs was a simple process. Both inhibited virus attachment but required much higher (>100-fold) molar concentrations for activity than did IgG. The functional affinities of the IgGs were high (0.4–0.6 nM) and differences between these and the affinity of their Fabs (H36, nil; H37, 23-fold) were not sufficient to explain the differences observed in neutralization. Similar neutralization data were obtained in two different cell lines. The dose–response curve for neutralization by H36 F(ab′)2 resembled that for IgG, although eightfold more F(ab′)2 was required for 50% neutralization. Overall, neutralization mechanisms of H36 and H37 antibodies were similar, and thus independent of antigenic site, antibody isotype, and target cell.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.