Intravenous Malaria Challenge of Vaccinated Aotus Monkeys

Four weeks after the final vaccination (study day 70), animals were challenged intravenously with 10⁴ FVO-strain P. falciparum-infected RBC collected freshly from a donor monkey. Parasitemia was measured by daily thin-film blood smears and hematocrit measurements were conducted on alternate days. Animals were treated with mefloquine (Roche Laboratories) when (i) parasite density reached ≥200,000 µL⁻¹, (ii) when Hct fell to ≤25%, (iii) if SP upon reaching 40 days after challenge (study day 110). Animals that self-cured were monitored for 3 days for continued absence of parasite and were treated with mefloquine. Based on this criteria all 6 animals in Group 1 were mefloquine-treated for high parasitema. In Group 2, animal T3169 was treated for high parasitemia while T3042 and T3121 were treated due to anemia. T3095, T3118, T3171 and T3173 were treated 3 days after self-curing parasitemia. In Group 3, T3123 was treated due to anemia while T3160 died during self-curing parasitemia possibly due to anemia. Such occasional deaths have been recorded in this Aotus model of human malaria.[22 (link), 35 (link), 36 (link)] T3174 developed anemia 2 days after self-curing and was also treated with mefloquine.