Susceptibility to anthrax lethal toxin is controlled by three linked quantitative trait loci

Area of Science:

• Immunology
• Genetics
• Toxicology

Background:

• Anthrax lethal toxin (LT) from Bacillus anthracis is a primary cause of mortality.
• Macrophages are key effector cells in LT-induced lethality, with genetic factors influencing their susceptibility.
• Kif1c was recently identified as Ltxs1, a gene affecting macrophage sensitivity to LT.

Purpose of the Study:

• To investigate the in vivo genetic control of mortality following LT challenge.
• To identify quantitative trait loci (QTL) influencing susceptibility to anthrax lethal toxin.

Main Methods:

• Utilized interval-specific recombinant congenic lines derived from LT-resistant DBA/2 and LT-susceptible BALB/c mice.
• Analyzed mortality data in relation to genetic markers on chromosome 11.
• Assessed Nos2 expression in macrophages via reverse transcription-polymerase chain reaction (RT-PCR).
• Investigated the effect of Nos2 inhibition on LT resistance.

Main Results:

• Identified three linked QTL controlling LT-induced mortality: Ltxs1/Kif1c, Ltxs2, and Ltxs3.
• The Ltxs3 interval contains Nos2, a strong candidate gene.
• Nos2 expression levels differ significantly between DBA/2 and BALB/c macrophages.
• Pharmacological inhibition of Nos2 partially reversed genetic resistance to LT.
• Dominant resistance in F1 hybrids requires DBA/2 alleles at all three QTL.

Conclusions:

• LT-induced mortality is a complex genetic trait regulated by at least three QTL on mouse chromosome 11.
• Nos2 plays a significant role in modulating macrophage susceptibility and overall resistance to anthrax lethal toxin.
• Understanding these genetic factors can inform strategies for managing anthrax infections.