Aggregatibacter actinomycetemcomitans Leukotoxin (LtxA)

Aggregatibacter actinomycetemcomitans leukotoxin (LtxA) is a 114 kDa pore-forming exotoxin and a major virulence factor of the oral pathogen A. actinomycetemcomitans. It belongs to the repeats-in-toxin (RTX) family and is characterized by its unique specificity for human white blood cells, which it targets by binding to the active conformation of the beta-2 integrin Lymphocyte Function-associated Antigen-1 (LFA-1). This interaction triggers rapid cell death via lysosomal disruption and the activation of apoptotic and necrotic pathways, allowing the bacterium to evade the host immune response. Beyond its role in aggressive periodontitis and endocarditis, LtxA is being developed as a therapeutic biologic (trade name Leukothera) for treating hematological malignancies and autoimmune disorders due to its ability to selectively deplete activated or malignant leukocytes. Additionally, the term 'leukotoxin' frequently refers to 9,10-epoxyoctadecenoic acid (9,10-EpOME), a toxic lipid metabolite of linoleic acid that serves as a biomarker and target in the study of acute respiratory distress syndrome (ARDS) and burn injuries. Drugs interacting with these molecules include experimental neutralizing antibodies and soluble epoxide hydrolase inhibitors that modulate lipid-mediated toxicity.

Other names

LtxA9,10-EpOMECoronaric acidLeukotheraRTX toxinLeukotoxin ALinoleic acid epoxideAggregatibacter leukotoxin

Binds specifically to the active conformation of the LFA-1 (CD11a/CD18) receptor on leukocytes, inducing rapid cell death; alternatively refers to the neutralization of linoleic acid metabolites that cause organ injury.