Identification of the immunoproteome of the meningococcus by cell surface immunoprecipitation and MS

Abstract

Most healthy adults are protected from meningococcal disease by the presence of naturally acquired anti-meningococcal antibodies; however, the identity of the target antigens of this protective immunity remains unclear, particularly for protection against serogroup B disease. To identify the protein targets of natural protective immunity we developed an immunoprecipitation and proteomics approach to define the immunoproteome of the meningococcus. Sera from 10 healthy individuals showing serum bactericidal activity against both a meningococcal C strain (L91543) and the B strain MC58, together with commercially available pooled human sera, were used as probe antisera. Immunoprecipitation was performed with each serum sample and live cells from both meningococcal strains. Immunoprecipitated proteins were identified by MS. Analysis of the immunoproteome from each serum demonstrated both pan-reactive antigens that were recognized by most sera as well as subject-specific antigens. Most antigens were found in both meningococcal strains, but a few were strain-specific. Many of the immunoprecipitated proteins have been characterized previously as surface antigens, including adhesins and proteases, several of which have been recognized as vaccine candidate antigens, e.g. factor H-binding protein, NadA and neisserial heparin-binding antigen. The data demonstrate clearly the presence of meningococcal antibodies in healthy individuals with no history of meningococcal infection and a wide diversity of immune responses. The identification of the immunoreactive proteins of the meningococcus provides a basis for understanding the role of each antigen in the natural immunity associated with carriage and may help to design vaccination strategies.

Proteome signatures—how are they obtained and what do they teach us?

“…Combining proteomics with the detection of antigens that show immunoreactivity allows for the identification of immunogenic proteins/ peptides expressed during infection (Dennehy and McClean 2012). Most studies have been focused on either cell surface or outer membrane proteins (Montero et al 2014;Newcombe et al 2014;Wu et al 2008b;Zhou et al 2009), as these are the de facto interface for host-pathogen interactions. Additionally, secreted proteins could also be of special interest (Barh et al 2013;Campbell et al 2015;Enany et al 2012;Wang et al 2014b;Wu et al 2008a), as these are also primary antigen targets of the host immune response and include many virulence factors (Dennehy and McClean 2012).…”

Mass spectrometry for the detection of bioterrorism agents: from environmental to clinical applications

“…This immunoproteomics approach used to identify potential candidate biomarkers has also been described for various viral or bacterial infections including Rickettsia parkeri , Neisseria meningitidis , Plasmodium knowlesi , and Klebsiella pneumoniae .…”

“…Interestingly, some of these proteins were identified using 2D electrophoresis, immunoblotting, and MS in immune sera of contaminated guinea pigs, suggesting that animal models can be used to predict biomarkers in human. [148] This immunoproteomics approach used to identify potential candidate biomarkers has also been described for various viral or bacterial infections including Rickettsia parkeri, [149] Neisseria meningitidis, [150] Plasmodium knowlesi, [151] and Klebsiella pneumoniae.…”

Vaccine antigen, Factor H binding protein, is typically a non-lipidated precursor that localises to the meningococcal surface by Slam

“…One of the studies correlating surface exposure of FHbp and susceptibility to killing by anti-FHbp antibodies was conducted by Newcombe and co-workers [27]. While strain L91543 displayed very little FHbp at the surface and demonstrated lack of killing by anti-FHbp sera, the well characterised MC58 strain demonstrated strong surface expression of FHbp and efficient killing by anti-FHbp sera [27]. We further observed a difference in size in FHbp between these 2 strains, despite their high amino acid (AA) sequence identity across the same length open reading frame (Fig 2a) [28].…”