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Infection and Immunity, July 2001, p. 4407-4416, Vol. 69, No. 7
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.7.4407-4416.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Deletion of wboA Enhances Activation of the Lectin Pathway of Complement in Brucella abortus and Brucella melitensis

Carmen M. Fernandez-Prada,1,* Mikeljon Nikolich,1 Ramesh Vemulapalli,2 Nammalwar Sriranganathan,2 Stephen M. Boyle,2 Gerhardt G. Schurig,2 Ted L. Hadfield,3 and David L. Hoover1

Department of Bacterial Diseases, Walter Reed Army Institute of Research,1 and Department of Microbiology, Armed Forces Institute of Pathology,3 Washington, D.C. 20307, and Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia 240612

Received 7 November 2000/Returned for modification 18 January 2001/Accepted 12 April 2001

Brucella spp. are gram-negative intracellular pathogens that survive and multiply within phagocytic cells of their hosts. Smooth organisms present O polysaccharides (OPS) on their surface. These OPS help the bacteria avoid the bactericidal action of serum. The wboA gene, coding for the enzyme glycosyltransferase, is essential for the synthesis of O chain in Brucella. In this study, the sensitivity to serum of smooth, virulent Brucella melitensis 16M and B. abortus 2308, rough wboA mutants VTRM1, RA1, and WRR51 derived from these two Brucella species, and the B. abortus vaccine strain RB51 was assayed using normal nonimmune human serum (NHS). The deposition of complement components and mannose-binding lectin (MBL) on the bacterial surface was detected by flow cytometry. Rough B. abortus mutants were more sensitive to the bactericidal action of NHS than were rough B. melitensis mutants. Complement components were deposited on smooth strains at a slower rate compared to rough strains. Deposition of iC3b and C5b-9 and bacterial killing occurred when bacteria were treated with C1q-depleted, but not with C2-depleted serum or NHS in the presence of Mg-EGTA. These results indicate that (i) OPS-deficient strains derived from B. melitensis 16M are more resistant to the bactericidal action of NHS than OPS-deficient strains derived from B. abortus 2308, (ii) both the classical and the MBL-mediated pathways are involved in complement deposition and complement-mediated killing of Brucella, and (iii) the alternative pathway is not activated by smooth or rough brucellae.

* Corresponding author. Mailing address: Department of Bacterial Diseases, Division of Communicable Diseases and Immunology, Walter Reed Army Institute of Research, Bldg. 503, Rm. 2N57, Washington, DC 20307-5100. Phone: (301) 319-9658. Fax: (301) 319-9123. E-mail: Carmen.Fernandez-Prada{at}NA.AMEDD.ARMY.MIL.

Infection and Immunity, July 2001, p. 4407-4416, Vol. 69, No. 7
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.7.4407-4416.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.