Moon Nahm, MD
Professor of Pathology
Director, Bacterial Respiratory Pathogen Reference Laboratory
|Address:||845 19th Street South
Bevill Research Bldg, room 614
Birmingham, AL 35294
|Members of the Laboratory|
B.A., Washington University in St. Louis MO
M.D., Washington University in St. Louis MO
Residency Training in Laboratory Medicine, Washington University in St. Louis MO
Postdoctoral fellow, Department of Microbiology, Washington University in St. Louis MO
Pneumococci are Gram-positive bacteria that are responsible for several important diseases such as pneumonia, meningitis, sepsis and ear infections. The most important virulence factor of pneumococci is their polysaccharide (PS) capsule. The main host defense against pneumococci is the production of anti-capsule antibodies. To study host-bacterial pathogen interactions and to improve pneumococcal vaccines, my laboratory studies the pneumococci’s capsules and the hosts’ anti-capsule antibodies.
To avoid host antibodies, pneumococci produce many serologically distinct PS capsules (more than 90 serotypes). To investigate the diversity in the PS capsules, we have developed a new serotyping system and, with it, have discovered new, previously unrecognized serotypes. One new serotype is 6C, which had previously been misclassified as serotype 6A. We have shown that 6C is chemically and genetically distinct from 6A, that its infection is not prevented by the currently available vaccine, and that its prevalence has been increasing worldwide. We also have discovered another new serotype, 11E, which appears to have been created by inactivation of one gene. By showing that pneumococci have more capacity to produce diverse capsule types than previously recognized, our work has increased our understanding on host-pathogen interactions. We are currently investigating various genetic mechanisms used to create different pneumococcal capsule types and the molecular evolution of 6C serotype, which occurred as a result of the widespread use of vaccines ineffective against it.
There is a need for new pneumococcal vaccines effective against serotype 6C. Pneumococcal vaccines are designed to elicit antibodies cross-reactive with various serotypes to elicit antibodies to as many capsule types as possible. We have discovered human antibodies that bind to a very simple chemical structure and are protective against four serotypes (6A, 6B, 6C, and 19A), which are responsible for 25% of all pneumococcal infections. This simple structure, if useful as a vaccine, would greatly simplify the design of pneumococcal vaccines. We are now investigating this simple structure as a vaccine candidate.
Strong inflammatory responses are one of the hallmarks of pneumococcal infections. To study biological bases for inflammation, we are investigating the ability of pneumococcal lipoteichoic acid (LTA) to stimulate innate immunity. This work has led us to revise the model for the pneumococcal LTA molecule. We have also shown that LTA is essential in inflammatory responses to pneumococci as well as to other Gram-positive bacteria. However, our studies also suggested that the stimulation of the innate immune system by LTA is complex, perhaps requiring synergistic bacterial factors. We are currently studying how LTA stimulates innate immunity.
Our studies have also led us to develop various bio-technologies such as multiplexed assays for antibody function (MOPA) and automated serotyping of pneumococci (Multibead Assay). We are also investigating a new way to diagnose pneumococcal pneumonia based on the biochemical changes observed during pneumonia infections. These bio-technologies are of fundamental importance in developing pneumococcal vaccines. Because of our development of these technologies and our expertise with pneumococcal antibodies, our laboratory is serving as the Reference Laboratory for both the NIH and the World Health Organization.
- Last Updated on June 25, 2013