Characterization of novel Omp31 antigenic epitopes of Brucella melitensis by monoclonal antibodies

Jinfeng Li,Shouyi Chen,Zuoping He,Chengyao Li,Peifang Luo,Jean-Pierre Allain,Feihuan Hu,Wenjing Wang

doi:10.1186/s12866-017-1025-3

Abstract

BackgroundBrucellosis is a severe zoonotic disease worldwide. Detection and identification of Brucella species are essential to prevent or treat brucellosis in humans and animals. The outer membrane protein-31 (Omp31) is a major protein of Brucellae except for B. abortus, while the Omp31 antigenic epitopes have not been extensively characterized yet.ResultsA total of 22 monoclonal antibodies (mAbs) were produced against Omp31 of Brucella (B.) melitensis, of which 13 recognized five linear epitopes, 7 reacted with semi-conformational epitopes and 2 reacted with conformational epitopes, respectively. The mAb isotypes were 11 (50%) IgG2a, 5 (23%) IgG1 and 6 (27%) IgM. On the basis of epitope recognition and reactivity levels, 8 mAbs including 3 IgM and 5 IgG clones were considered as highly reactive and potentially diagnostic antibodies. Among these mAbs, 7A3 (IgG1), 5B1 (IgG2a), 2C1 (IgG2a) and 5B3 (IgG2a) reacted with differently conserved linear epitopes of B. melitensis, B. ovis, B. suis and B. canis strains, while 5H3 (IgG2a) highly reacted with a conformational epitope of Omp31 when tested with several immunoassays.ConclusionsThese potent monoclonal antibodies can be used for identifying Omp31 antigens or detecting B. melitensis and other Brucella species beyond B. abortus in vitro or in vivo.

Highlights

Brucellosis is a severe zoonotic disease worldwide
Classification of outer membrane protein-31 (Omp31) epitopes by Monoclonal antibody (mAb)’s recognition In order to classify the Omp31 antigenic epitopes, all mAbs were tested for reactivity with 27 16mer overlapping peptides derived from full-length amino acid sequence, denatured or non-denatured protein forms of B. melitensis Omp31 in various immunoassays
Twenty mAbs were reactive to the denatured recombinant Omp31 (rOmp31) and 14 mAbs to the denatured native membrane protein extract (NMP) by Western blot (Fig. 1b), respectively

Summary

Introduction

Brucellosis is a severe zoonotic disease worldwide. Detection and identification of Brucella species are essential to prevent or treat brucellosis in humans and animals. The outer membrane protein-31 (Omp31) is a major protein of Brucellae except for B. abortus, while the Omp antigenic epitopes have not been extensively characterized yet. Brucellosis is one of the most serious zoonoses worldwide It causes severe diseases in humans and substantial animal losses. We generated and characterized 22 novel murine monoclonal antibodies (mAbs) binding native Omp of B. melitensis. Some of these antibodies presented high reactivity with different epitopes of Omp, suggesting potential capacity to identify Omp antigens of Brucellae or to detect B. melitensis or other Brucella species beyond B. abortus

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