Pn. Brusasca et al., Immunological characterization of antigens encoded by the RD1 region of the Mycobacterium tuberculosis genome, SC J IMMUN, 54(5), 2001, pp. 448-452
Development of immunoassays specific for the diagnosis of tuberculosis requ
ires antigens unique to Mycobacterium tuberculosis. In a search for such an
tigens we tested six proteins encoded by RD1, a region present in M. tuberc
ulosis and virulent M. bovis genomes but missing from the DNA of all substr
ains of M. bovis Bacillus Calmette-Guerin (BCG). The six proteins (Rv3871,
Rv3872, Rv3873, MTSA-10, ESAT-6 and Rv3878) were purified to near-homogenei
ty from recombinant Escherichia coli. When tested for the ability to elicit
antibody responses and delayed type hypersensitivity in tuberculous guinea
pigs, only two of six antigens, ESAT-6 and MTSA-10, elicited strong skin r
eactions, while vigorous antibody responses were observed to all six protei
ns. When antibody responses to RD1 antigens were evaluated in sera from pat
ients having pulmonary tuberculosis and from control subjects (patients hav
ing mycobacterioses other than tuberculosis, and healthy persons), a sizeab
le proportion (25%) of tuberculosis patients but none of the control subjec
ts, had antibodies against MTSA-10 and/or ESAT-6. We conclude that MTSA-10
and ESAT-6 are promising candidates for immunodiagnostic assays specific fo
r tuberculosis.