Study of the effect of Anisakis simplex larval products on the early and late components in the classical complement pathway

In previous studies, we have reported that the larval products (crude extract [CE] and excretory-secretory [ES]) of Anisakis simplex showed a dose-dependent inhibition of the lysis mediated by classical (CP) and alternative pathways (AP) of the human complement system, with the major inhibition on the CP rather than on AP. This inhibition of hemolysis is due to the consumption of complement factors because the assays performed shortening the preincubation period result in a significant decrease of the inhibitory effect on the lysis of the larval products compared with the standard time. Likewise, we found that the larval products reduce the inhibitory percentages in the CP using C3-deficient sera, but not in the AP, which could indicate that other complement components are implicated in the inhibitory effect in the CP. Hence, we have studied the activity of the larval products of A. simplex on individual components in the CP, using different complement-deficient sera. The investigated complement molecules were C1q, C2, C4, C5, C6, C7, C8, and C9. The larval products showed activity at the C2 level but failed to have a significant effect on the other components. Therefore, CE and ES products from A. simplex interact with C3 and C2 complement proteins, which are early components of the complement system, but not with the late complement components.