Fig. 1.

Leukotoxin expression levels in A. actinomycetemcomitans strains. (A) The expression of ltxA was significantly higher in the RhAa-ltxP530 strain as compared with the RhAa3 strain and was analyzed by qRT-PCR to measure gene transcripts. (B) Functional leukotoxin production as determined by THP killing was significantly higher in the RhAa-ltxP530 strain as compared with the RhAa3 strain. All of the experiments were performed in biological triplicate and the data shown are the standard error of the mean (±SEM). The differences between the groups were calculated by the Student’s t test (*P < 0.05).