TABLE 1.

Trypomastigote-induced parasitemia and mortality in mice immunized with either ASP-2 DNA or recombinant protein administered individually or sequentially (DNA priming/protein boosting)

Mouse group no.	Immunogena	Peak parasitemia (log ± SD)b	No. of mice alive/total no. challengedc	% Protection
I	pcDNA3	6.35 ± 0.08	0/16	0
II	Alum	6.53 ± 0.05	0/8	0
III	ASP-2 DNA	5.42 ± 0.09	12/16	75.00
IV	Alum/His-65kDa	5.62 ± 0.32	8/15	53.31
V	ASP-2 DNA plus alum/His-65kDa	5.55 ± 0.23	11/15	73.74

^aGroups of seven or eight mice were immunized at 0, 3, and 5 weeks with pcDNA3, ASP-2 DNA, alum, or the formulation alum/His-65kDa. A fifth group of mice was injected with two doses of ASP-2 DNA at 0 and 3 weeks. A third immunizing dose was administered after 5 weeks and consisted of the formulation alum/His-65kDa.

^bTwo weeks after the last dose, mice were challenged i.p. with 250 bloodstream trypomastigotes. The values of peak parasitemia of mouse groups III, IV, and V were lower than those for mouse groups I and II (P < 0.05 in all cases). The peak parasitemias of groups III, IV, and V were not statistically different (P > 0.05).

^cThe number of mice alive was recorded 60 days after challenge. Animals from groups III, IV, and V survived longer than mice from groups I and II (P < 0.0001 in all cases by the log rank test). There was no significant statistical difference among groups III, IV, and V (P > 0.05).