Tài liệu Báo cáo khoa học: Exposure of IgG to an acidic environment results in molecular

Exposure of IgG to an acidic environment results in

molecular modifications and in enhanced protective

activity in sepsis

Iglika K. Djoumerska-Alexieva1,*, Jordan D. Dimitrov1,2,3,4,*, Elisaveta N. Voynova1

,

Sebastien Lacroix-Desmazes2,3,4, Srinivas V. Kaveri2,3,4 and Tchavdar L. Vassilev1

1 Department of Immunology, Stefan Angelov Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria

2 Centre de Recherche des Cordeliers, Universite´ Pierre et Marie Curie Paris 6, France

3 Universite´ Paris Descartes, France

4 INSERM U 872, Eq. 16, Paris, France

Introduction

The ability of antibodies to interact with one single or

with multiple structurally unrelated antigens (monore￾activity versus polyreactivity) is believed to be an

inherent property of each individual immunoglobulin

molecule. However, it has been previously shown by

us, as well as by others, that the in vitro exposure of

monoclonal and of polyclonal IgG to various protein￾destabilizing factors may result in dramatic enhance￾ment of their binding polyreactivity. These treatments

include high-salt solutions, low-pH or high-pH buffers,

chaotropic agents, ferrous ions, reactive oxygen

species, and heme [1–7].

Keywords

antibodies; antibody polyreactivity; antigen–

antibody interaction; IgG; immunoglobulins

Correspondence

T. Vassilev, Stefan Angelov Institute of

Microbiology, Bulgarian Academy of

Sciences, Acad. G. Bonchev St., Block 26,

1113 Sofia, Bulgaria

Fax: +359 2 870 0109

Tel: +359 2 979 6348

E-mail: [email protected]

*These authors contributed equally to this

work

(Received 22 February 2010, revised 22

April 2010, accepted 18 May 2010)

doi:10.1111/j.1742-4658.2010.07714.x

IgG molecules are exposed on a regular basis to acidic conditions during

immunoaffinity purification procedures, as well as during the production of

some therapeutic immunoglobulin preparations. This exposure is known to

induce in them an antigen-binding polyreactivity. The molecular mecha￾nisms and the possible biological significance of this phenomenon remain,

however, poorly understood. In addition to the previously reported ability

of these modified IgG antibodies to interact with a large panel of self-anti￾gens, enhanced binding to non-self-antigens (bacterial), an increased ability

to engage in F(ab¢)2 ⁄F(ab¢)2 (idiotype ⁄ anti-idiotype) interactions and an

increased functional antigen-binding affinity are reported here. The newly

acquired ‘induced polyreactivity’ of low-pH buffer-exposed IgG is related

to structural changes in the immunoglobulin molecules, and is at least

partly attributable to the enhanced role of the hydrophobic effect in their

interactions with antigen. Our results suggest that data from many previous

studies on monoclonal and polyclonal IgG antibodies purified by low-pH

buffer elution from protein A or protein G immunoaffinity columns should

be reconsidered, as the procedure itself may have dramatically affected

their antigen-binding behavior and biological activity. Low-pH buffer-trea￾ted pooled therapeutic immunoglobulins acquire novel beneficial properties,

as passive immunotherapy with the pH 4.0 buffer-exposed, but not with

the native therapeutic intravenous immunoglobulin preparation, improves

the survival of mice with bacterial lipopolysaccharide-induced septic shock.

Abbreviations

ANS, 8-anilinonaphthalene-1-sulfonate; CRP, C-reactive protein; IFN-c, interferon-c; IVIg, intravenous immunoglobulin;

LPS, lipopolysaccharide; RU, relative units.

FEBS Journal 277 (2010) 3039–3050 ª 2010 The Authors Journal compilation ª 2010 FEBS 3039