Mycobacterium tuberculosis (Mtb) isocitrate dehydrogenases show strong B cell response and distinguish vaccinated controls from TB patients.

Abstract

Proteins released from Mycobacterium tuberculosis (Mtb) during late logarithmic growth phase are often considered candidate components of immunogenic or autolysis markers. One such protein is isocitrate dehydrogenase (ICD), a key regulatory enzyme in the citric acid cycle. We have evaluated the immunogenic properties of two isoforms of Mtb ICD and compared them with the control antigens heat-shock protein 60 and purified protein derivative (PPD). PPD lacks the sensitivity to distinguish between bacillus Calmette-Guérin (BCG)-vaccinated and tuberculosis (TB)-infected populations, and, therefore, epidemiological relevance of PPD in BCG-vaccinated regions is debatable. We show that Mtb ICDs elicit a strong B cell response in TB-infected populations and can differentiate between healthy BCG-vaccinated populations and those with TB. The study population (n = 215) was categorized into different groups, namely, patients with fresh infection (n = 42), relapsed TB cases (n = 32), patients with extrapulmonary TB (n = 35), clinically healthy donors (n = 44), nontuberculous mycobacteria patients (n = 30), and non-TB patients (culture negative for acid-fast bacteria but carrying other infections, n = 32). The Mtb ICDs showed statistically significant antigenic distinction between healthy BCG-vaccinated controls and TB patients (P < 0.0001) and those with other infections. Although extrapulmonary infections could not be discriminated from healthy controls by heat-shock protein 60 (P = 0.2177), interestingly, the Mtb ICDs could significantly (P < 0.0001) do so. Our results highlight the immunodominant, immunosensitive, and immunospecific nature of Mtb ICDs and point to an unusual property of this tricarboxylic acid energy cycle enzyme.

• Authors: Sharmistha Banerjee, Ashok Nandyala, Raviprasad Podili, V M Katoch, K J R Murthy, Seyed E Hasnain
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 101 Issue 34 Pg. 12652-7 (Aug 24 2004) ISSN: 0027-8424 [Print] United States
• PMID: 15314217 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• BCG Vaccine
• Bacterial Proteins
• Chaperonin 60
• Protein Isoforms
• Recombinant Proteins
• Isocitrate Dehydrogenase

Topics

• Antibody Formation
• B-Lymphocytes (immunology)
• BCG Vaccine (immunology)
• Bacterial Proteins (genetics, immunology)
• Chaperonin 60 (immunology)
• Humans
• Isocitrate Dehydrogenase (genetics, immunology)
• Mycobacterium tuberculosis (enzymology)
• Protein Isoforms (immunology)
• Recombinant Proteins (genetics, immunology)
• Tuberculosis (diagnosis, immunology)
• Vaccination