Cynthia N. Cornelissen , Ph.D.
Professor

Phone: (804) 827-1754
Dept. Fax: (804) 828-9946
e-mail: cncornel@vcu.edu

Address:
Department of Microbiology & Immunology
Virginia Commonwealth University
PO Box 980678
1101 East Marshall Street, Sanger Hall 6-052
Richmond, VA 23298-0678

Lab Web Page

Professional Experience

• B.S., 1984, University of Illinois, Urbana-Champaign 
• M.S., 1986, University of Illinois, Urbana-Champaign 
• Ph.D., 1989, University of Illinois, Urbana-Champaign
• Postdoctoral, 1989-1991, University of North Carolina at Chapel Hill
• Research Associate, 1991-1994, University of North Carolina at Chapel Hill
• Research Assistant Professor, 1994-1997, University of North Carolina at Chapel Hill

Research Interests:

Neisseria gonorrhoeae is a human pathogen of significant public health concern since it causes not only a localized infection but also potentially serious sequelae including pelvic inflammatory disease and ectopic pregnancy in women. Recently it has been recognized that bacterial STDs such as gonorrhea and chlamydial infection are co-factors for HIV transmission, which has hastened the search for vaccine strategies against bacterial pathogens. Potential gonococcal vaccine candidates include surface-exposed receptors necessary for nutrient uptake in vivo. One such candidate is the transferrin receptor. The components of this receptor are not subject to high-frequency variation, are expressed by all gonococci, and are required to initiate the signs and symptoms of urethritis in human male volunteers. In my laboratory, we are interested in the structure, function and regulation of the gonococcal transferrin receptor since understanding how the receptor works is essential if we are to prevent its function in vivo. We are also evaluating the immunogenicity of these proteins and the functional relevance of an immune response generated against them.

The gonococcal transferrin receptor is made up of two proteins: transferrin-binding proteins A and B (TbpA and TbpB). Both of these proteins bind transferrin and contribute to transferrin-iron uptake. In its requirement for two different proteins, the gonococcal transferrin receptor is to be contrasted to other bacterial iron transporters, which require a single protein. One of the transferrin-binding proteins (TbpA) shares homology with a family of integral outer membrane proteins that depend upon energization by a set of proteins including TonB, ExbB and ExbD. The other transferrin-binding protein (TbpB) is acetylated, substantially surface-exposed, and antigenically more variable. TbpB preferentially binds iron-loaded transferrin; thus this protein is postulated to play roles in recognition of holo-transferrin and in release of deferrated transferrin. We are interested in the topologies of TbpA and TbpB in the outer membrane, what domains are critical for transferrin binding and what domains are surface exposed. This aspect of our studies has obvious vaccine implications since surface-exposed domains of a receptor are potential targets for immunoprophylaxis. We are interested in the stoichiometry of the transferrin-binding proteins in the functional receptor and what effect ligand and TonB-derived energy have on the resulting stoichiometric relationships.

We have proposed a hypothetical, two-dimensional topology model of TbpA, based on its homology with other TonB-dependent, outer membrane transporters, several of which have now been crystallized. Using this hypothetical model, we designed deletion and insertion strategies, with which we demonstrated the surface accessibility and functional importance of several putative loops of TbpA. We determined that transferrin release from TbpA requires TonB-derived energy. We have also demonstrated that TbpA physically interacts with TonB forming a stable complex, the formation of which does not require the presence of chemical cross-linkers. We would like to further characterize the TonB-TbpA interaction, identifying domains of both TbpA and TonB required for association and function. Using similar approaches, we have probed structure-function relationships in TbpB, by which we identified an amino-terminal transferrin-binding domain which is required for the wild-type function of TbpB.

Expression of TbpA and TbpB is increased under low-iron growth conditions, a phenomenon that is mediated by the Fur protein, a transcriptional repressor of iron-regulated genes that has been well characterized in other systems. A consensus Fur-binding site precedes the genes encoding TbpA and TbpB, mutagenesis of which results in constitutive expression. We have demonstrated that TbpA and TbpB are co-transcribed from a single transcript, and furthermore that there are segmental differences in steady-state transcript levels, resulting in a 2:1 ratio of tbpB : tbpA transcripts. We are currently evaluating the physiological relevance of an inverted repeat located between tbpA and tbpB using RT-PCR and fusion technologies. In other systems, the stoichiometry of multi-subunit complexes is achieved in part by regulation of expression by intervening stem-loop structures in mRNA transcripts. Thus, we hypothesize that a similar regulatory mechanism could influence the stoichiometry of the proteins that comprise the gonococcal transferrin receptor.

Because TbpA and TbpB are considered viable vaccine candidates, we evaluated the immune response generated against these proteins during natural infections in men and women. We determined that there was only a modest level of Tbp-specific antibodies in the sera from gonorrhea patients, and Tbp-specific antibodies in mucosal secretions were below the limits of detection. This suggests that natural infection does not elicit a vigorous immune response. Thus, we are attempting to construct immunogenic vaccines, to be delivered intranasally, that will elicit a protective immune response, even if natural infections do not. To date, we have been able to generate antigenic, intranasal vaccines comprised of TbpA, TbpB and the non-toxic B subunit of cholera toxin. These antigens elicited antibodies that were capable of bactericidal activity against heterologous gonococci in the presence of human complement. We plan to test the efficacy of these vaccine antigens in an animal model of gonococcal colonization.

Selected Publications:

Cornelissen C.N., and P.F. Sparling. Iron piracy: acquisition of transferrin-bound iron by bacterial pathogens.  Mol. Microbiol. 14:843-850 (1994).

Cornelissen C.N., and P.F. Sparling. Binding and surface-characteristics of the gonococcal transferrin receptor are dependent on both transferrin-binding proteins.  J. Bacteriol.  178:1437-1444 (1996).

Cornelissen C.N., J.E. Anderson, and P.F. Sparling.  Characterization of the diversity and transferrin-binding domain of gonococcal Tbp2.  Infect. Immun. 65:822-828 (1997).

Cornelissen C.N., Anderson JE, Sparling PF. Energy-dependent changes in the gonococcal transferrin receptor. Mol Microbiol. 1997 Oct;26(1):25-35.

Cornelissen C.N., Kelley M, Hobbs MM, Anderson JE, Cannon JG, Cohen MS, Sparling PF. The transferrin receptor expressed by gonococcal strain FA1090 is required for the experimental infection of human male volunteers. Mol Microbiol. 1998 Feb;27(3):611-6.

Cornelissen C.N., J.E. Anderson, I.C. Boulton, and P.F. Sparling: Antigenic and sequence diversity in gonococcal transferrin-binding protein A (TbpA), Infec. Immun. 68 : 4725-4735, 2000.

Boulton I.C., M.K. Yost, J.E. Anderson, and C.N. Cornelissen: Idenfication of discrete domains within gonococcal transferrin-binding protein A (TbpA) that are necessary for ligand binding and iron uptake functions, Infect. Immun. 68 : 6988-6996, 2000.

Ronpirin C., A. Jerse, and C.N. Cornelissen: The gonococcal genes encoding transferrin-binding proteins (Tbp) A and B are arranged in a bicistronic operon but are subject to diffential expression, Infect. Immun. 69 : 6336-6347, 2001.

Jerse A.E., E.T. Crow, A.N. Bordner, I. Rahman, C.N. Cornelissen, T. Moench, and K. Mehrazar: Growth of Neisseria gonorhoeae in female mouse genital tract does not require the gonococcal transferrin or hemoglobin receptors and may be enhanced by commensal lactobacilli, Infect. Immuno. 70 : 2549-2558, 2002.

Masri H.P., and C.N. Cornelissen: Specific ligand binding attributable to individual epitopes of gonococcal transferrin-binding protein A (TbpA), Infect. Immun. 70 : 732-740, 2002.

Kenney C., and C.N. Cornelissen: Demostration and characterization of a specific interaction between gonococcal transferrin-binding protein A and TonB, J. Bacteriol. 184 : 6138-6145, 2002.

Paik, S., A. Brown, C.L. Munro, C.N. Cornelissen, and T. Kitten: The sloABCR operon of Streptococcus mutans encodes a Mn and Fe transport system required for endocarditis virulence and its Mn-dependent repressor, J. Bacteriol. 185 : 5967-5975, 2003.

Price, G.A., M.M. Hobbs, and C.N. Cornelissen: Immunogenicity of gonococcal transferrin binding proteins during natural infection, Infect. Immun. 72 : 277-283, 2004.

Yost-Daljev, M.K. and C.N. Cornelissen: Determination of surface-exposed, functional domains of gonococcal transferrin binding protein A (TbpA), Infect. Immun., 72 : 1775-1785, 2004.

Price, G.A., M.W. Russell, and C.N. Cornelissen: Intranasal administration of recombinant Neisseria gonorrhoeae transferrin binding proteins A and B conjugated to the cholera toxin B subunit induces systemic and vaginal antibodies in mice, Infect. Immun., 73 : 3945-3953, 2005.

Hagen, T.A. and C.N. Cornelissen: Neisseria gonorrhoeae requires expression of TonB and the putative transporter TdfF to replicate within cervical epithelial cells, Mol. Microbiol., 62 : 1144-1157, 2006.

DeRocco, A.J. and C.N. Cornelissen: Identification of transferrin binding domains in TbpB expressed by Neisseria gonorrhoeae, Infect. Immun. 75(7): 3220-3232, 2007.

Price, G.A., H.P. Masri, A.M. Hollander, M.W. Russell, and C.N. Cornelissen: Goncoccal transferrin binding protein-cholera toxin B chimeras induce serum bactericidal and vaginal transferrin-utilization blocking antibodies in mice, Vaccine, 25(41): 7247-7260, 2007.

Virginia Commonwealth University | School of Medicine
Date Last Modified: 05/05/2009
Contact Department Webmaster