COBRE Investigator:
  Sarah Hobdey, PhD

Scientific Discipline:
Biomolecular Protein Chemistry

COBRE Project:
 Generation of fully-human recombinant anti-toxin antibodies for treatment of necrotizing infections

:  Necrotizing soft tissue infections remain a significant cause of morbidity and mortality worldwide.  A small, well-defined group of organisms accounts for nearly 95% of all such rapidly progressive life-threatening toxin-mediated infections.  These include group A streptococcus (GAS), several histotoxic clostridial species and hypervirulent methicillin-resistant Staphylococcus aureus (MRSA).  Irrespective of the etiologic agent, treatment must be initiated early.  However, obtaining definitive clinical laboratory identification of the causative agent and its antimicrobial sensitivities costs valuable time.  Empiric antibiotic treatment can prove disastrous given the rise of emerging resistance, and because some antimicrobials can increase bacterial toxin production.

:  We hypothesize that 1) administration of a fully human recombinant immunoglobulin (Ig) cocktail containing high-tier neutralizing antibodies against the principal exotoxins of all the primary pathogens associated with devastating Gram positive infections will provide a vital, early therapeutic edge to current treatment strategies; 2) B-cells elicited by the immune response to natural infection will provide key, toxin-specific, neutralizing antibody genes for the in vitro generation of fully-human monoclonal antibodies (hmAbs).

Specific Aims
:  We will exploit the natural immunity of humans having had prior GAS infection, combined with cutting-edge human B-cell isolation and enrichment technologies for the production of recombinant hmAbs targeting the model cholesterol-dependent cytolysin streptolysin O (SLO).  Specifically, IgG genes will be cloned from highly abundant, short-lived, SLO-specific plasmablasts (Aim 1) or from low frequency, long lasting, memory B-cells (Aim 2) isolated from the peripheral blood of donors with naturally-acquired immunity following GAS infection.  In both Aims 1 and 2, IgG genes from isolated cells will be sequenced, cloned and recombinantly expressed in a human cell line to generate fully human, toxin-specific monoclonal antibodies.  In Aim 3, we will confirm the ability of the hmAbs to neutralize SLO activity in vitro and to provide protection in relevant animal models.

Impact on Human Health
:  A fully human multi-pathogen/multi-toxin recombinant neutralizing antibody cocktail, used empirically at the earliest stages of developing necrotizing infection, will lessen the severity, reduce the need for amputation, and significantly improve patient outcomes.

Harry Hill, MD and Amy Bryant, PhD