Frequencies of Region of Difference 1 Antigen-Specific but Not Purified Protein Derivative-Specific Gamma Interferon-Secreting T Cells Correlate with the Presence of Tuberculosis Disease but Do Not Distinguish Recent from Remote Latent Infections

Abstract

The majority of individuals infected with Mycobacterium tuberculosis achieve lifelong immune containment of the bacillus. What constitutes this effective host immune response is poorly understood. We compared the frequencies of gamma interferon (IFN-␥)-secreting T cells specific for five region of difference 1 (RD1)-encoded antigens and one DosR-encoded antigen in 205 individuals either with active disease (n ‫؍‬ 167), whose immune responses had failed to contain the bacillus, or with remotely acquired latent infection (n ‫؍‬ 38), who had successfully achieved immune control, and a further 149 individuals with recently acquired asymptomatic infection. When subjects with an IFN-␥ enzyme-linked immunospot (ELISpot) assay response to one or more RD1-encoded antigens were analyzed, T cells from subjects with active disease recognized more pools of peptides from these antigens than T cells from subjects with nonrecent latent infection (P ‫؍‬ 0.002). The T-cell frequencies for peptide pools were greater for subjects with active infection than for subjects with nonrecent latent infection for summed RD1 peptide pools (P < 0.006) and culture filtrate protein 10 (CFP-10) antigen (P ‫؍‬ 0.029). Individuals with recently acquired (<6 months) versus remotely acquired (>6 months) latent infection did not differ in numbers of peptide pools recognized, proportions recognizing any individual antigen or peptide pool, or antigen-specific T-cell frequencies (P > 0.11). The hierarchy of immunodominance for different antigens was purified protein derivative (PPD) > CFP-10 > early secretory antigenic target 6 > Rv3879c > Rv3878 > Rv3873 > Acr1, and the hierarchies were very similar for active and remotely acquired latent infections. Responses to the DosR antigen ␣-crystallin were not associated with latency (P ‫؍‬ 0.373). In contrast to the RD1-specific responses, the responses to PPD were not associated with clinical status (P > 0.17) but were strongly associated with positive tuberculin skin test results (>15-mm induration; P < 0.01). Our results suggest that RD1-specific IFN-␥-secreting T-cell frequencies correlate with the presence of disease rather than with protective immunity in M. tuberculosis-infected individuals and do not distinguish recently acquired asymptomatic infection from remotely acquired latent infection.

Immunodiagnosis of Tuberculosis: a Dynamic View of Biomarker Discovery

“…Collectively, these results strongly indicate that antigen recognition by T cells tracks antigen profiles expressed by tubercle bacilli in association with growth phase. It is worth mentioning, however, that one study found no difference in the response to ␣-crystallin between active TB and LTBI (64). One possible explanation is that strong differences in absolute bacillary load between latent infection and multibacillary forms of active TB overcome the effect of growth-phase-associated antigen expression.…”

“…It has been suggested that the use of particular ESAT-6-derived peptides in lieu of full-length protein may enhance discrimination between active disease and latent infection (53,56). Together with the observation that responses to ex vivo stimulation with purified protein derivative (PPD) do not differ between active TB and LTBI (64), the results obtained with ESAT-6 peptides suggest that the choice of epitope is a critical factor in the evaluation of biomarker levels in response-to-antigen assays.…”

Pyrexia of unknown origin 90 years on: a paradigm of modern clinical medicine

“…More concerning is the indiscriminate use of immunological assays, previously the tuberculin skin test but recently the interferon-γ release assay (IGRA), in the diagnosis of TB as a cause of PUO. The literature has been heterogeneous but in general highlights the limited sensitivity, and specificity, of IGRA for the diagnosis of active TB 20 21. All infectious diseases specialists have experience of the patient with active TB and a negative IGRA, and yet many still find themselves using the test in some patients—albeit with open eyes—its role perhaps most useful in tilting the differential in the patient without risk factors for exposure, but with granulomatous pathology or inaccessible (eg, brain) pathology on imaging.…”

Long-Incubation-Time Gamma Interferon Release Assays in Response to Purified Protein Derivative, ESAT-6, and/or CFP-10 for the Diagnosis of Mycobacterium tuberculosis Infection in Children

“…In addition, despite a sensitivity of 80% in adults with aTB, the negative predictive value is not high enough to recommend its use to reject a diagnosis of aTB (8). The utility of these tests in adults is therefore restricted to the diagnosis of LTBI, but their sensitivities for the diagnosis of remote LTBI were recently challenged (9)(10)(11)(12)(13). As the antigens used in the commercialized gamma interferon release assays (IGRA) are poorly expressed by M. tuberculosis during its latency, corresponding antigen-specific T cells in the blood are mainly memory T lymphocytes that are not optimally detected by short-term assays (10,14).…”