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The Neutralization Properties of a HIV-Specific Antibody Are Markedly Altered by Glycosylation Events Outside the Antigen-Binding Domain¹

Luis R. Miranda^*, Mark Duval^*, Heather Doherty^*, Michael S. Seaman, Marshall R. Posner^* and Lisa A. Cavacini^2,*

^* Division of Hematology/Oncology and Division of Viral Pathogenesis, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215

Neutralizing Abs constitute a pivotal mechanism of the adaptive immune response against HIV-1 infection. Yet, most of the Abs that appear in the circulation during HIV infection are nonneutralizing. In this study, we report a dramatic change of the neutralizing properties of a human Ab reactive with the nonneutralizing epitope termed cluster I on the HIV-1 transmembrane protein gp41 when the Ab was produced in Chinese hamster ovary (CHO)-K1 cells. Our laboratory has previously reported that the Ab F240, when produced in a hybridoma, is nonneutralizing as assessed by standard neutralization assays. The F240 IgG1 Ab expressed in CHO cells acquired a strong neutralization activity against a broad range of HIV isolates without a change in immunoreactivity. Sequencing of the F240 mRNAs produced in the parental hybridoma and CHO cells revealed identical sequences, suggesting that acquired neutralization resulted from cell-specific posttranslational modifications. We found that the Ab produced by CHO cells is glycosylated to a greater extent than the parental Ab produced by the hybridoma. Moreover, treatment with peptide N-glycosidase F abrogated F240 neutralization, in an isolate-specific manner, but not Ab b12 neutralization. Interestingly, the F240 isotype-switched variants IgG3 and IgG4, also expressed in CHO cells, exhibited identical immunoreactivity to IgG1 isotypes but had clear differences in viral neutralization. These results suggest that structural features of the Ig molecule other than the primary sequence of the variable regions play a more prominent role in HIV neutralization than anticipated.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ This research was supported by National Institute of Allergy and Infectious Diseases, National Institutes of Health Grant AI-063986 (to M.R.P.) and Harvard University CFAR Scholar Award P30 AI-060354 (to L.R.M.).

² Address correspondence and reprint requests to Dr. Lisa Cavacini, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215. E-mail address: lcavacin{at}bidmc.harvard.edu

³ Abbreviations used in this paper: CHO, Chinese hamster ovary; AAL, Aleuria aurantia lectin; IRES, internal ribosome entry site; N-linked, asparagine-linked; OPD, orthophenylenediamine; PNGase F, peptide N-glycosidase F; RCAI, Ricinus communis agglutinin I; SNA, Sambucus nigra agglutinin.

This article has been cited by other articles:

				M. Duval, M. R. Posner, and L. A. Cavacini A Bispecific Antibody Composed of a Nonneutralizing Antibody to the gp41 Immunodominant Region and an Anti-CD89 Antibody Directs Broad Human Immunodeficiency Virus Destruction by Neutrophils J. Virol., May 1, 2008; 82(9): 4671 - 4674. [Abstract] [Full Text] [PDF]