Enhancement of bacterial virulence by antibody neutralization of immune-activating toxins. 2010

Pauline Yoong
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA. pyoong@rics.bwh.harvard.edu

Bacterial pathogens release a number of toxins that are able to form pores in target host cells, which can result in their destruction. Due to this property of this subgroup of toxins, they are considered virulence factors. A lesser known ability of these toxins when present at lower concentrations that are insufficient for host cell lysis to occur, is their activation of host immune cells. The Panton-Valentine Leukocidin (PVL) secreted by an alarming percentage of Staphylococcus aureus causing community-acquired infections, is one such: toxin. Due to the low inoculum of S. aureus we used to establish skin abscesses in a murine model of infection, lower amounts of PVL are likely to be present early in infection, hence, the proinflammatory properties of PVL may be more evident. Our data not only suggested that this was indeed the case, but we also showed that antibodies directed to PVL neutralized immune activation by this toxin resulting in a less robust host innate immune response. Thus, given the high levels of antibodies to PVL present in healthy individuals, these antibodies may directly enhance the virulence of PVL-producing S. aureus by dampening the innate immune response to infection. Since many pore-forming toxins share this dual property of concentration-dependent host cell lysis and immune activation, it is interesting to speculate that antibodies raised to some bacterial toxins may have the opposite intended outcome of directly enhancing bacterial virulence instead of controlling infection.

UI MeSH Term Description Entries
D007956 Leukocidins Pore forming proteins originally discovered for toxic activity to LEUKOCYTES. They are EXOTOXINS produced by some pathogenic STAPHYLOCOCCUS and STREPTOCOCCUS that destroy leukocytes by lysis of the cytoplasmic granules and are partially responsible for the pathogenicity of the organisms. Leucocidin,Leukocidin,Leukocidin Proteins,Proteins, Leukocidin
D004195 Disease Models, Animal Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases. Animal Disease Model,Animal Disease Models,Disease Model, Animal
D005098 Exotoxins Toxins produced, especially by bacterial or fungal cells, and released into the culture medium or environment. Exotoxin
D000038 Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Abscesses
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000907 Antibodies, Bacterial Immunoglobulins produced in a response to BACTERIAL ANTIGENS. Bacterial Antibodies
D000992 Antitoxins Antisera from immunized animals that is purified and used as a passive immunizing agent against specific BACTERIAL TOXINS. Antitoxin
D001427 Bacterial Toxins Toxic substances formed in or elaborated by bacteria; they are usually proteins with high molecular weight and antigenicity; some are used as antibiotics and some to skin test for the presence of or susceptibility to certain diseases. Bacterial Toxin,Toxins, Bacterial,Toxin, Bacterial
D013207 Staphylococcal Skin Infections Infections to the skin caused by bacteria of the genus STAPHYLOCOCCUS. Skin Diseases, Staphylococcal,Infections, Staphylococcal Skin,Skin Infections, Staphylococcal,Staphylococcal Diseases, Skin,Staphylococcal Infections, Skin,Staphylococcal Skin Diseases
D014774 Virulence The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS. Pathogenicity

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