Immune Response to Recombinant Mycobacterial Proteins in Patients with Tuberculosis Infection and Disease

Abstract

The capacity of four Mycobacterium tuberculosis recombinant antigens to elicit proliferation and cytokine production by human T cells was evaluated. Proliferative responses of peripheral blood mononuclear cells (PBMC) to all antigens were greater in healthy tuberculin reactors than in pulmonary tuberculosis patients, and proliferative responses of pleural fluid cells were greater than those of PBMC from patients with tuberculous pleuritis. The proliferative responses to the four recombinant antigens were similar in all patient groups, and there was no selective unresponsiveness to any antigen in pulmonary tuberculosis patients. The 38-kDa antigen induced less interferon-gamma than did the 10-, 30-, and 65-kDa antigens, and all four antigens induced similar amounts of interleukin-10. These results suggest that none of the four recombinant antigens are immunodominant, and that the 10-, 30-, and 65-kDa antigens are similar in their capacity to induce a potentially protective Th1-like response.

Naive Human T Cells Develop into Th1 Effectors after Stimulation withMycobacterium tuberculosis-Infected Macrophages or Recombinant Ag85 Proteins

“…Not surprisingly, IL-4 was produced by the one Th2 Mtb T-cell line in response to rAg85A. These results support the immunodominance of Ag85 proteins which has been shown by other investigators, primarily by using cells from PPD ϩ asymptomatic individuals (6,15,26). Of interest, a a Resting cells from rAg85B-specific T-cell lines were stimulated in vitro with MIM (20:1) or HKM (15 g/ml)-or rAg85B (10 g/ml)-pulsed normal macrophages for 3 days.…”

“…These data support observations demonstrating that inherent resistance to Mycobacterium in BCG-resistant mice does not depend on optimal IL-12 levels (35). Together, the results suggest that other cytokines (e.g., IL-18 and MIP-1␤) also contribute to the development of M. tuberculosis-specific Th1 responses (11,34 Human T-cell responses to secreted Ag85 proteins appear to be immunodominant in PPD ϩ latently infected individuals (6,15,26) and are downregulated in those with active tuberculosis (3,15,26). These findings suggest an association with protective responses.…”

“…These findings suggest an association with protective responses. Furthermore, strong Th1 responses have been elicited in vitro from PPD ϩ asymptomatic individuals using native, recombinant, or synthetic peptide forms of Ag85 proteins (15,23,26). In addition, Ag85 proteins have been shown to induce partial protection in murine models of infection (17,18).…”

In Situ Activation of Helper T Cells in the Lung

“…Therefore, it is perplexing that no discernible differences in the distribution of helper T-cell subsets or variations in the level of activation molecules that they expressed were found in the lung segments of our TB patients. There were numerous reports that the proliferative response of human PB lymphocytes to the whole bacilli and recombinant or secreted proteins of M. tuberculosis was diminished in TB patients relative to that in tuberculin-positive healthy controls (7,29,30), and while patients with minimal disease gave a response comparable to that of M. tuberculosis BCG-vaccinated donors, patients with active advanced disease did not (7). Thus, it will be intriguing to determine if there are discernible differences in CD4 ϩ lymphocytes of anergic and nonanergic TB patients.…”

Evidence for the expression of native Mycobacterium tuberculosis phospholipase C: recognition by immune sera and detection of promoter activity

“…Purification of native mycobacterial proteins is a technically difficult process because large amounts of bacilli are necessary and the complex wall requires complex and laborious lysis and purification steps. Recent advances in mycobacterial genetics and availability of antigens in recombinant form have provided the opportunity to evaluate, for example, specific immune responses directed against them (22). Expression of mycobacterial antigens in nonpathogenic organisms like E. coli and Saccharomyces cerevisiae can be enhanced by placing genes under the control of strong promoters, and has the additional advantage of permitting safer working conditions.…”