Associate Physician
Brigham and Women's Hospital

lmadoff@channing.harvard.edu

Dr. Madoff's research interests are in the field of bacterial pathogenesis and vaccine design. His current projects include the study of immunologically important surface proteins (C proteins) of the group B Streptococcus (Streptococcus agalactiae). This organism is the leading cause of neonatal sepsis and meningitis, a cause of peripartum infections in women, and a cause of serious infections in immunocompromised adults. The surface proteins of these bacteria have been characterized using biochemical methods and further analyzed through the development of protective monoclonal antibodies. We are investigating the alpha and beta C proteins, distinct antigens expressed on many group B streptococcal isolates, which show both similarities to and differences from other gram positive surface proteins. They appear to have important roles in the virulence of these organisms and elicit protective immunity.

The beta C protein is a 130-kd protein which binds specifically to human IgA. We cloned the protective region of this protein in E. coli and demonstrated protection against infection in experimental animals by immunizing with the cloned gene product. We subsequently isolated and purified the protein and demonstrated that active maternal immunization with the protein would protect newborn mouse pups against lethal infection. We subsequently produced a conjugate vaccine using a type-specific polysaccharide covalently linked to the beta C protein. This vaccine elicited high levels of protective antibodies both to the polysaccharide component and to the protein component in experimental animals, demonstrating for the first time that a protein could serve both as carrier and protective immunogen and protect simultaneously against multiple serotypes of group B streptococci. We currently plan to produce a human vaccine based on this prototype.

The alpha C protein is characterized by an unusual laddered appearance on gel electrophoresis. We cloned and sequenced the gene encoding the protein from the prototype group B streptococcal strain. It contains a series of nine tandem repeating units which are identical at the nucleotide level. We demonstrated that different strains of the bacterium contained different sizes of alpha C proteins which all reacted with a protective monoclonal antibody. The strains differ in the number of tandem repeating subunits contained within the alpha gene. We have expressed and purified the alpha C protein from E. coli and shown the cloned gene product to be protective in experimental infection. However, we have also demonstrated the emergence of mutations which have undergone deletion of tandem repeating units and thus escape immunity. We are investigating the mechanism of these deletions.

Synthetic gene constructs containing variable numbers of tandem repeats of the alpha C protein were produced and their gene products purified. Using these proteins we have shown that binding to alpha specific antibody is reduced as the number of repeats is reduced. Moreover, as the repeat number decreases, the affinity of antibody binding decreases in such a way as to suggest that a conformational change in the antigen has occurred. This suggests a mechanism whereby the organism may "adjust" the repeat number so as to alter immune binding, a mechanism of antigenic variation which may be of general importance to the many pathogenic microorganisms (fungal, bacterial, and parasitic) that express repeat-containing antigens. Strategies for overcoming this mechanism of escape mutation are under investigation.

We have discovered proteins related by sequence homology to the alpha C protein which occur among group B streptococcal strains of serotypes which have recently emerged as clinically important. We are studying the role of these proteins in virulence and immunity.

Madoff LC, Hori S, Michel JL, Baker CJ, Kasper DL. Phenotypic diversity in the alpha C protein of group B streptococci. Infect Immun 1991;59:2638-2644. [abstract]

Michel JL, Madoff LC, Olson K, Kling DE, Kasper DL, Ausubel FM. Large, identical, tandem repeating units in the C protein alpha antigen gene, bca, of group B streptococci. Proc Natl Acad Sci U S A 1992;89:10060-10064. [abstract]

Madoff LC, Michel JL, Gong EW, Rodewald AK, Kasper DL. Protection of neonatal mice from group B streptococcal infection by maternal immunization with beta C protein. Infect Immun 1992;60:4989-4994. [abstract]

Madoff LC, Paoletti LC, Tai JY, Kasper DL. Maternal immunization of mice with group B streptococcal type III polysaccharide-beta C protein conjugate elicits protective antibody to multiple serotypes. J Clin Invest. 1994 Jul;94(1):286-92. [abstract]

Lachenauer CS, Madoff LC. A protective surface protein from type V group B streptococci shares N-terminal sequence homology with the alpha C protein. Infect. Immun. 1996;64:4255-4260. [abstract]

Gravekamp CD, Horensky S, Michel JL, Madoff LC. Variation in repeat number within the alpha C protein of group B Streptococcus alters antigenicity and protective epitopes. Infect. Immun. 1996;64:3576-3583. [abstract]

Madoff LC, Michel JL, Kling D, Gong EW, Kasper DL. Group B streptococci escape host immunity by deletion of tandem repeat elements of the alpha C protein. Proc. Natl. Acad. Sci. USA 1996;93:4131-4136. [abstract]

Gravekamp C, Kasper DL, Michel JL, Kling DE, Carey V, Madoff LC. Immunogenecity and protective efficacy of the alpha C protein of group B Streptococcus are inversely related to repeat number. Infect Immun 1997;65:5216-5221. [abstract]

Gravekamp C, Rosner B, Madoff LC. Deletion of repeats in the alpha C protein enhances pathogenecity of group B streptococci in immune mice. Infect Immun 1998;66:4347-4354. [abstract]

Lachenauer CS, Kasper DL, Simada J, Ichiman Y, Ohtsuka H, Kaku M, Paoletti LC, Ferrieri P, Madoff LC. Serotypes VI and VIII predominate among group B streptococci isolated from pregnant Japanese women. J Infect Dis 1999;179:1030-1033. [abstract]

Huebner J, Wang Y, Krueger WA, Madoff LC, Martirosian G, Golmann DA, Kasper DL, Tzianabos AO, Pier GB. Isolation and chemical characterization of a capsular polysaccharide antigen shared by clinical isolates of Enterococcus faecalis and vancomycin-resistant Enterococcus faecium. Infect Immun 1999;67:1213-1219. [abstract]

Gravekamp C, Kasper DL, Paoletti LC, Madoff LC. Alpha C protein as a carrier protein for type III capsular polysaccharide and as a protective protein in group B streptococcal vaccines. Infect Immun 1999;67:2491-2496. [abstract]