DIFFERENTIAL MUCOSAL INFECTIVITY OF DIFFERENT LIFE STAGES OF TRYPANOSOMA-CRUZI

Mucosal invasion is an important method of vector-borne transmission o f Trypanosoma cruzi to human hosts. We previously have shown that low numbers of virulent insect-derived metacyclic trypomastigotes (IMT) co llected from the excreta of reduviid bugs were highly efficient in inf ecting mice through gastrointestinal and conjunctival mucosa. However, we have recently found that blood-form trypomastigotes (BFT) of T. cr uzi cannot efficiently initiate mucosal infection after an oral challe nge of the gastrointestinal tract. Evidence for systemic infection aft er oral challenge with BFT was sought by microscopic parasitemia exami nations of fresh blood, polymerase chain reaction analyses with DNA ex tracted from mouse blood using primers specific for it nuclear repeat present in thr T. cruzi genome, and by Western blots of parasite lysat es probed with individual mouse serum. Oral challenge doses of 1,000-1 0,000 BFT were found to rarely initiate mucosal infection, In contrast , 1,000 Ih IT delivered orally was a sufficient challenge for the cons istent infection of 100% of control BALB/c mice. The exceptions infect ed mucosally by BFT involved animals with mucosal defects due to traum a or ulcerative/periodontal diseases. These data suggest that IMT have uniquely specialized functions for mucosal invasion that are not norm ally present in BFT.