The contribution of host genetics to tuberculosis pathogenesis.

Area of Science:

• Human Genetics
• Immunology
• Infectious Diseases

Background:

• Host genetics plays a complex role in human tuberculosis (TB) susceptibility, with evidence from twin studies and family risks.
• Previous genetic studies have faced challenges in detecting strong genetic effects due to limited consideration of host-pathogen strain combinations and gene-environment interactions.
• Most research has focused on progression from infection to disease, with fewer studies investigating resistance to infection or the control of antimycobacterial immunity.

Purpose of the Study:

• To investigate the contribution of host genetics to innate resistance against Mycobacterium tuberculosis infection.
• To identify genetic loci controlling T-cell independent and T-cell mediated immune responses to M. tuberculosis.
• To explore the implications of host genetic control on anti-mycobacterial immunity and tuberculosis vaccine efficacy.

Main Methods:

• Utilized the tuberculin skin test as a measure of resistance to M. tuberculosis infection to evaluate immune responses.
• Employed genetic mapping techniques to identify major loci associated with resistance and delayed-type hypersensitivity (DTH).
• Focused on studies involving international collaborations, including scientists from South Africa, France, and Canada.

Main Results:

• Identified a major genetic locus, TST1, on chromosomal region 11p14, which controls T-cell independent resistance to M. tuberculosis.
• Discovered a second major locus, TST2, on chromosomal region 5p15, that regulates the intensity of T-cell mediated DTH to tuberculin.
• These findings demonstrate strong host genetic control over anti-mycobacterial immunity.

Conclusions:

• The identified genetic loci provide a foundation for understanding the molecular mechanisms of resistance to M. tuberculosis infection in endemic regions.
• These discoveries are critical for identifying key regulators of T-cell dependent DTH responses to tuberculin.
• The significant role of host genetics in anti-mycobacterial immunity raises questions about its potential impact as a barrier to developing universally effective tuberculosis vaccines.