Identification of Mycobacterial RplJ/L10 and RpsA/S1 Proteins as Novel Targets for CD4⁺ T Cells

Area of Science:

• Immunology
• Vaccinology
• Microbiology

Background:

• Tuberculosis (TB) remains a significant global health challenge, necessitating improved vaccines.
• A genetically modified Mycobacterium smegmatis strain, IKEPLUS, has shown promise as a TB vaccine candidate.
• Protective immunity elicited by IKEPLUS relies on antigen-specific CD4+ T cell memory.

Purpose of the Study:

• To investigate the specificity of CD4+ T cell responses induced by the IKEPLUS vaccine candidate.
• To identify specific antigenic targets recognized by CD4+ T cells in IKEPLUS-immunized mice.
• To explore the role of these T cells in protective immunity against Mycobacterium tuberculosis challenge.

Main Methods:

• In vitro enzyme-linked immunosorbent spot (ELISPOT) assays to measure interferon gamma production from splenocytes of IKEPLUS-immunized mice.
• Generation and screening of major histocompatibility complex (MHC) class II-restricted T cell hybridomas.
• Analysis of T cell responses to IKEPLUS and purified mycobacterial ribosomes.
• Assessment of CD4+ T cell accumulation in the lungs post-M. tuberculosis aerosol challenge.

Main Results:

• An immunogenic peptide from the ribosomal protein RplJ (Rv0651) was identified.
• CD4+ T cell responses in IKEPLUS-immunized mice were predominantly directed against multiple components of the mycobacterial ribosome.
• Significant accumulation of mycobacterial ribosome-specific CD4+ T cells was observed in the lungs after M. tuberculosis challenge.

Conclusions:

• The study identifies mycobacterial ribosomes as critical targets for CD4+ T cell-mediated immunity against TB.
• Defined ribosomal protein epitopes represent novel antigenic targets for developing more effective TB vaccines.
• These findings contribute to understanding protective immune responses and designing next-generation tuberculosis vaccines.