<i>P. berghei slarp</i>(-) sporozoites elicit limited protective responses in C57BL/6 mice against wild type sporozoite challenge.

aC57BL/6 were immunized three times at two weeks intervals, with indicated numbers of P. berghei slarp(-) sporozoites injected intravenously, or by exposure to the bites of ten slarp(-) infected mosquitoes. bImmunized mice were challenged by intravenous injection of 10,000 P. berghei WT sporozoites or by exposure to the bites of five WT infected mosquitoes, as indicated. cNumber of days after sporozoite inoculation until detection of infected erythrocytes by microscopic blood smear examination. NA, not applicable.