Open AccessCharacterization of Auxotrophic Mutants of Mycobacterium tuberculosis and Their Potential as Vaccine Candidates
Author(s) -
Debbie A. Smith,
Tanya Parish,
Neil G. Stoker,
Gregory J. Bancroft
Publication year - 2001
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.69.2.1442-1150.2001
Subject(s) - mutant , auxotrophy , virulence , mycobacterium tuberculosis , biology , methionine , microbiology and biotechnology , mutation , gene , virology , tuberculosis , genetics , amino acid , medicine , pathology
Auxotrophic mutants ofMycobacterium tuberculosis have been proposed as new vaccine candidates. We have analyzed the virulence and vaccine potential ofM. tuberculosis strains containing defined mutations in genes involved in methionine (metB ), proline (proC ), or tryptophan (trpD ) amino acid biosynthesis. ThemetB mutant was a prototrophic strain, whereas theproC andtrpD mutants were auxotrophic for proline and tryptophan, respectively. Following infection of murine bone marrow-derived macrophages, H37Rv and themetB mutant strain survived intracellularly for over 10 days, whereas over 90% ofproC andtrpD mutants were killed during this time. In SCID mice, both H37Rv and themetB mutant were highly virulent, with mouse median survival times (MST) of 28.5 and 42 days, respectively. TheproC mutant was significantly attenuated (MST, 130 days), whereas thetrpD mutant was essentially avirulent in an immunocompromised host. Following infection of immunocompetent DBA mice with H37Rv, mice survived for a median of 83.5 days and themetB mutant now showed a clear reduction in virulence, with two of five infected mice surviving for 360 days. BothproC andtrpD mutants were avirulent (MST of >360 days). In vaccination studies, prior infection with either theproC ortrpD mutant gave protection equivalent (proC mutant) to or better (trpD mutant) than BCG against challenge withM. tuberculosis H37Rv. In summary,proC andtrpD genes are essential for the virulence ofM. tuberculosis , and mutants with disruptions in either of these genes show strong potential as vaccine candidates.