scholarly journals Peptidoglycan Contribution to the B Cell Superantigen Activity of Staphylococcal Protein A

mBio ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Miaomiao Shi ◽  
Stephanie E. Willing ◽  
Hwan Keun Kim ◽  
Olaf Schneewind ◽  
Dominique Missiakas
Keyword(s):  
B Cell ◽  
Protein A ◽  
B Cell Receptors ◽  
Staphylococcal Protein A ◽  
Content Type ◽  
Cell Receptors ◽  
Staphylococcal Protein ◽  
Lpxtg Motif ◽  
Sorting Signal ◽  
Lysm Domain

ABSTRACT Staphylococcus aureus causes reiterative and chronic persistent infections. This can be explained by the formidable ability of this pathogen to escape immune surveillance mechanisms. Cells of S. aureus display the abundant staphylococcal protein A (SpA). SpA binds to immunoglobulin (Ig) molecules and coats the bacterial surface to prevent phagocytic uptake. SpA also binds and cross-links variable heavy 3 (VH3) idiotype (IgM) B cell receptors, promoting B cell expansion and the secretion of nonspecific VH3-IgM via a mechanism requiring CD4+ T cell help. SpA binding to antibodies is mediated by the N-terminal Ig-binding domains (IgBDs). The so-called region X, uncharacterized LysM domain, and C-terminal LPXTG sorting signal for peptidoglycan attachment complete the linear structure of the protein. Here, we report that both the LysM domain and the LPXTG motif sorting signal are required for the B cell superantigen activity of SpA in a mouse model of infection. SpA molecules purified from staphylococcal cultures are sufficient to exert B cell superantigen activity and promote immunoglobulin secretion as long as they carry intact LysM and LPXTG motif domains with bound peptidoglycan fragments. The LysM domain binds the glycan chains of peptidoglycan fragments, whereas the LPXTG motif is covalently linked to wall peptides lacking glycan. These findings emphasize the complexity of SpA interactions with B cell receptors. IMPORTANCE The LysM domain is found in all kingdoms of life. While their function in mammals is not known, LysM domains of bacteria and their phage parasites are associated with enzymes that cleave or remodel peptidoglycan. Plants recognize microbe-associated molecular patterns such as chitin via receptors endowed with LysM-containing ectodomains. In plants, such receptors play equally important roles in defense and symbiosis signaling. SpA of S. aureus carries a LysM domain that binds glycan strands of peptidoglycan to influence defined B cell responses that divert pathogen-specific adaptive immune responses.

scholarly journals Staphylococcal Protein A Contributes to Persistent Colonization of Mice withStaphylococcus aureus

2018 ◽  
Vol 200 (9) ◽  
Author(s):  
Yan Sun ◽  
Carla Emolo ◽  
Silva Holtfreter ◽  
Siouxsie Wiles ◽  
Barry Kreiswirth ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
B Cell ◽  
Neutralizing Antibodies ◽  
Protein A ◽  
Staphylococcal Protein A ◽  
Content Type ◽  
Staphylococcal Protein ◽  
Host Immune Responses ◽  
Increased Risk ◽  
Drug Resistant Strains

ABSTRACTStaphylococcus aureuspersistently colonizes the nasopharynx in humans, which increases the risk for invasive diseases, such as skin infection and bacteremia. Nasal colonization triggers IgG responses against staphylococcal surface antigens; however, these antibodies cannot prevent subsequent colonization or disease. Here, we describeS. aureusWU1, a multilocus sequence type 88 (ST88) isolate that persistently colonizes the nasopharynx in mice. We report that staphylococcal protein A (SpA) is required for persistence ofS. aureusWU1 in the nasopharynx. Compared to animals colonized by wild-typeS. aureus, mice colonized with the Δspavariant mount increased IgG responses against staphylococcal colonization determinants. Immunization of mice with a nontoxigenic SpA variant, which cannot cross-link B cell receptors and divert antibody responses, elicits protein A-neutralizing antibodies that promote IgG responses against colonizingS. aureusand diminish pathogen persistence.IMPORTANCEStaphylococcus aureuspersistently colonizes the nasopharynx in about one-third of the human population, thereby promoting community- and hospital-acquired infections. Antibiotics are currently used for decolonization of individuals at increased risk of infection. However, the efficacy of antibiotics is limited by recolonization and selection for drug-resistant strains. Here, we propose a model of how staphylococcal protein A (SpA), a B cell superantigen, modifies host immune responses during colonization to support continued persistence ofS. aureusin the nasopharynx. We show that this mechanism can be thwarted by vaccine-induced anti-SpA antibodies that promote IgG responses against staphylococcal antigens and diminish colonization.

scholarly journals Diversity of Functionally Distinct Clonal Sets of Human Conventional Memory B Cells That Bind Staphylococcal Protein A

2021 ◽  
Vol 12 ◽  
Author(s):  
Emily E. Radke ◽  
Zhi Li ◽  
David N. Hernandez ◽  
Hanane El Bannoudi ◽  
Sergei L. Kosakovsky Pond ◽  
...  
Keyword(s):  
Immune System ◽  
B Cells ◽  
B Cell ◽  
Binding Site ◽  
Protein A ◽  
Memory B Cells ◽  
Host Immune System ◽  
Staphylococcal Protein A ◽  
Staphylococcal Protein ◽  
Circulating Antibodies

Staphylococcus aureus, a common cause of serious and often fatal infections, is well-armed with secreted factors that disarm host immune defenses. Highly expressed in vivo during infection, Staphylococcal protein A (SpA) is reported to also contribute to nasal colonization that can be a prelude to invasive infection. Co-evolution with the host immune system has provided SpA with an Fc-antibody binding site, and a Fab-binding site responsible for non-immune superantigen interactions via germline-encoded surfaces expressed on many human BCRs. We wondered whether the recurrent exposures to S. aureus commonly experienced by adults, result in the accumulation of memory B-cell responses to other determinants on SpA. We therefore isolated SpA-specific class-switched memory B cells, and characterized their encoding VH : VL antibody genes. In SpA-reactive memory B cells, we confirmed a striking bias in usage for VH genes, which retain the surface that mediates the SpA-superantigen interaction. We postulate these interactions reflect co-evolution of the host immune system and SpA, which during infection results in immune recruitment of an extraordinarily high prevalence of B cells in the repertoire that subverts the augmentation of protective defenses. Herein, we provide the first evidence that human memory responses are supplemented by B-cell clones, and circulating-antibodies, that bind to SpA determinants independent of the non-immune Fc- and Fab-binding sites. In parallel, we demonstrate that healthy individuals, and patients recovering from S. aureus infection, both have circulating antibodies with these conventional binding specificities. These findings rationalize the potential utility of incorporating specially engineered SpA proteins into a protective vaccine.

scholarly journals Protein A-Specific Monoclonal Antibodies and Prevention of Staphylococcus aureus Disease in Mice

2012 ◽  
Vol 80 (10) ◽  
pp. 3460-3470 ◽  
Author(s):  
Hwan Keun Kim ◽  
Carla Emolo ◽  
Andrea C. DeDent ◽  
Fabiana Falugi ◽  
Dominique M. Missiakas ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Monoclonal Antibodies ◽  
Immune Responses ◽  
B Cell ◽  
Protein A ◽  
Abscess Formation ◽  
Staphylococcal Protein A ◽  
Content Type ◽  
Humoral Immune ◽  
Binding Domains

ABSTRACTStaphylococcus aureusis a leading cause of human soft tissue infections and bacterial sepsis. The emergence of antibiotic-resistant strains (methicillin-resistantS. aureus[MRSA]) has prompted research into staphylococcal vaccines and preventive measures. The envelope ofS. aureusis decorated with staphylococcal protein A (SpA), which captures the Fcγ portion of immunoglobulins to prevent opsonophagocytosis and associates with the Fab portion of VH3-type B cell receptors to trigger B cell superantigen activity. Nontoxigenic protein A (SpAKKAA), when used as an immunogen in mice, stimulates humoral immune responses that neutralize the Fcγ and the VH3+Fab binding activities of SpA and provide protection from staphylococcal abscess formation in mice. Here, we isolated monoclonal antibodies (MAbs) against SpAKKAAthat, by binding to the triple-helical bundle fold of its immunoglobulin binding domains (IgBDs), neutralize the Fcγ and Fab binding activities of SpA. SpAKKAAMAbs promoted opsonophagocytic killing of MRSA in mouse and human blood, provided protection from abscess formation, and stimulated pathogen-specific immune responses in a mouse model of staphylococcal disease. Thus, SpAKKAAMAbs may be useful for the prevention and therapy of staphylococcal disease in humans.

scholarly journals Staphylococcal Protein A (spa) Locus Is a Hot Spot for Recombination and Horizontal Gene Transfer in Staphylococcus pseudintermedius

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Alem Zukancic ◽  
Mubin A. Khan ◽  
Sumayya J. Gurmen ◽  
Quinn M. Gliniecki ◽  
Dayna L. Moritz-Kinkade ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Genetic Factors ◽  
Hot Spot ◽  
Protein A ◽  
Multidrug Resistant ◽  
Staphylococcal Protein A ◽  
Staphylococcus Pseudintermedius ◽  
Content Type ◽  
Staphylococcal Protein

ABSTRACT Staphylococcus pseudintermedius is a major canine pathogen but also occasionally colonizes and infects humans. Multidrug-resistant methicillin-resistant S. pseudintermedius (MDR MRSP) strains have emerged globally, making treatment and control of this pathogen challenging. Sequence type 71 (ST71), ST68, and ST45 are the most widespread and successful MDR MRSP clones. The potential genetic factors underlying the clonal success of these and other predominant clones remain unknown. Characterization of the pangenome, lineage-associated accessory genes, and genes acquired through horizontal gene transfer from other bacteria is important for identifying such factors. Here, we analyzed genome sequence data from 622 S. pseudintermedius isolates to investigate the evolution of pathogenicity across lineages. We show that the predominant clones carry one or more lineage-associated virulence genes. The gene encoding staphylococcal protein A (SpA), a key virulence factor involved in immune evasion and a potential vaccine antigen, is deleted in 62% of isolates. Most importantly, we have discovered that the spa locus is a hot spot for recombination and horizontal gene transfer in S. pseudintermedius, where genes related to restriction modification, prophage immunity, mercury resistance, and nucleotide and carbohydrate metabolism have been acquired in different lineages. Our study also establishes that ST45 is composed of two distinct sublineages that differ in their accessory gene content and virulence potential. Collectively, this study reports several previously undetected lineage-associated genetic factors that may have a role in the clonal success of the major MDR MRSP clones. These data provide a framework for future experimental studies on S. pseudintermedius pathogenesis and for developing novel therapeutics against this pathogen. IMPORTANCE Staphylococcus pseudintermedius is a major canine pathogen but can also occasionally infect humans. Identification of genetic factors contributing to the virulence and clonal success of multidrug-resistant S. pseudintermedius clones is critical for the development of therapeutics against this pathogen. Here, we characterized the genome sequences of a global collection of 622 S. pseudintermedius isolates. We show that all major clones, besides carrying core virulence genes, which are present in all strains, carry one or more lineage-specific genes. Many of these genes have been acquired from other bacterial species through a horizontal gene transfer mechanism. Importantly, we have discovered that the staphylococcal protein A gene (spa), a widely used marker for molecular typing of S. pseudintermedius strains and a potential vaccine candidate antigen, is deleted in 62% of strains. Furthermore, the spa locus in S. pseudintermedius acts as a reservoir to accumulate lineage-associated genes with adaptive functions.

scholarly journals Staphylococcal Protein A Induces Leukocyte Necrosis by Complexing with Human Immunoglobulins

mBio ◽  
2021 ◽  
Author(s):  
Proinnsias G. Fox ◽  
Francesca Schiavetti ◽  
Rino Rappuoli ◽  
Rachel M. McLoughlin ◽  
Fabio Bagnoli
Keyword(s):  
Staphylococcus Aureus ◽  
Protein A ◽  
The United States ◽  
Staphylococcal Protein A ◽  
Human Pathogen ◽  
Content Type ◽  
Staphylococcal Protein ◽  
Human Immunoglobulins ◽  
Human Immune Response ◽  
Human Immune

Staphylococcus aureus is one of the largest health care threats faced by humankind, with a reported mortality rate within the United States greater than that of HIV/AIDS, tuberculosis, and viral hepatitis combined. One of the defining features of S. aureus as a human pathogen is its ability to evade and impair the human immune response through expression of staphylococcal protein A.

scholarly journals Role of Protein A in the Evasion of Host Adaptive Immune Responses by Staphylococcus aureus

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
Fabiana Falugi ◽  
Hwan Keun Kim ◽  
Dominique M. Missiakas ◽  
Olaf Schneewind
Keyword(s):  
Staphylococcus Aureus ◽  
B Cells ◽  
B Cell ◽  
Cell Function ◽  
Protein A ◽  
Immune Surveillance ◽  
Staphylococcal Protein A ◽  
Wild Type ◽  
Content Type ◽  
Host Immune Surveillance

ABSTRACTHeritable defects in human B cell/antibody development are not associated with increased susceptibility toStaphylococcus aureusinfection. Protein A (SpA), a surface molecule ofS. aureus, binds the Fcγ domain of immunoglobulin (Ig) and cross-links the Fab domain of VH3-type B cell receptors (IgM). Here we generatedS. aureus spavariants harboring amino acid substitutions at four key residues in each of the five Ig-binding domains of SpA. Wild-typeS. aureusrequired SpA binding to Ig to resist phagocytosis and SpA-mediated B cell receptor cross-linking to block antibody development in mice. ThespaKKAAmutant, which cannot bind Ig or IgM, was phagocytosed and elicited B cell responses to key virulence antigens that protected animals against lethalS. aureuschallenge. The immune evasive attributes ofS. aureusSpA were abolished in µMT mice lacking mature B cells and antibodies. Thus, while wild-typeS. aureusescapes host immune surveillance, thespaKKAAvariant elicits adaptive responses that protect against recurrent infection.IMPORTANCEStaphylococcus aureuscauses recurrent skin and bloodstream infections without eliciting immunity. Heritable defects in neutrophil and T cell function, but not B cell or antibody development, are associated with increased incidence ofS. aureusinfection, and efforts to develop antibody-basedS. aureusvaccines have thus far been unsuccessful. We show here that the Fcγ and VH3-type Fab binding activities of staphylococcal protein A (SpA) are essential forS. aureusescape from host immune surveillance in mice. The virulence attributes of SpA in mice required mature B cells and immunoglobulin. These results suggest that antibodies and B cells play a key role in the pathogenesis of staphylococcal infections and provide insights into the development of a vaccine againstS. aureus.

scholarly journals The YSIRK-G/S Motif of Staphylococcal Protein A and Its Role in Efficiency of Signal Peptide Processing

2003 ◽  
Vol 185 (9) ◽  
pp. 2910-2919 ◽  
Author(s):  
Taeok Bae ◽  
Olaf Schneewind
Keyword(s):  
Cell Wall ◽  
Signal Peptide ◽  
Protein A ◽  
Surface Proteins ◽  
Signal Peptides ◽  
Staphylococcal Protein A ◽  
Gram Positive ◽  
Peptide Processing ◽  
Staphylococcal Protein ◽  
Sorting Signal

ABSTRACT Many surface proteins of pathogenic gram-positive bacteria are linked to the cell wall envelope by a mechanism requiring a C-terminal sorting signal with an LPXTG motif. Surface proteins of Streptococcus pneumoniae harbor another motif, YSIRK-G/S, which is positioned within signal peptides. The signal peptides of some, but not all, of the 20 surface proteins of Staphylococcus aureus carry a YSIRK-G/S motif, whereas those of surface proteins of Listeria monocytogenes and Bacillus anthracis do not. To determine whether the YSIRK-G/S motif is required for the secretion or cell wall anchoring of surface proteins, we analyzed variants of staphylococcal protein A, an immunoglobulin binding protein with an LPXTG sorting signal. Deletion of the YSIR sequence or replacement of G or S significantly reduced the rate of signal peptide processing of protein A precursors. In contrast, cell wall anchoring or the functional display of protein A was not affected. The fusion of cell wall sorting signals to reporter proteins bearing N-terminal signal peptides with or without the YSIRK-G/S motif resulted in hybrid proteins that were anchored in a manner similar to that of wild-type protein A. The requirement of the YSIRK-G/S motif for efficient secretion implies the existence of a specialized mode of substrate recognition by the secretion pathway of gram-positive cocci. It seems, however, that this mechanism is not essential for surface protein anchoring to the cell wall envelope.

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