Comparative analysis of specific IFN-γ production induced by Mycobacterium tuberculosis in two different nonhuman primates

Abstract

Objective To analyze the differences of immune responses against Mycobacterium tuberculosis antigens induced in two different nonhuman primates and to provide rationales for the selection of suitable animal models for vaccine efficacy evaluation. Methods Expression of functional surface markers including CD69 and HLA-DR, the activation markers on CD4+ and CD8+ T cells from in rhesus macaques and cynomolgus monkeys were measured by flow cytometry analysis. PBMCs were isolated from rhesus macaques and cynomolgus monkeys with Mycobacterium tuberculosis infection and stimulated with PPD and peptide pools (ESAT-6/CFP-10). Enzyme-linked imunospot (ELISPOT) assay was performed to detect IFN-γ producing lymphocytes. Results The CD4+ and CD8+ T cells isolated from rhesus macaques without Mycobacterium tuberculosis infection expressed higher levels of CD69 and HLA-DR than those from healthy cynomolgus monkeys (P<0.01). The numbers of IFN-γ spot forming cells/106 PBMCs in rhesus macaques with Mycobacterium tuberculosis infection for 10 and 11 months were respectively 3 and 3.5 times higher than that of cynomolgus monkeys upon after the stimulation of PBMCs with PPD. The levels of IFN-γ production by the cells from rhesus macaque group were also higher than those from cynomolgus monkey group upon after the stimulation of PBMCs with ESAT-6 or CFP-10 peptide pools. Conclusion More IFN-γ producing cells were induced in rhesus macaques than that in cynimolgus monkeys after stimulation with Mycobacterium tuberculosis antigens. Therefore, the rhesus macaques might be a better animal model for evaluating immune responses induced by Mycobacterium tuberculosis vaccines. Key words: Flow cytometry; Mycobacterium tuberculosis; IFN-γ; Enzyme-linked imunospot