Susceptibility of Panamanian Aotus lemurinus lemurinus to sporozoite-induced Plasmodium falciparum (Santa Lucia) infection.

Aotus monkeys are good models for erythrocyte-induced Plasmodium falciparum and P. vivax infections and have been extensively used in malarial drug and vaccine development. Recently, it has been shown that certain species of Aotus can be infected with sporozoites, and that the degree of susceptibility varies among species. We demonstrate here that Panamanian Aotus lemurinus lemurinus are susceptible to a sporozoite-induced infection, opening the possibility that this species of Aotus could be used as models for testing the efficacy of pre-erythrocytic P. falciparum vaccines and drug candidates directed at the pre-erythrocytic stages of P. falciparum and P. vivax malaria. In this species, we compared sporozoite infection rates. Two of four animals splenectomized prior to infection with sporozoites developed patent parasitemias. Seven of eight animals splenectomized either 7 or 35 days after infection became parasitemic. Additionally, we used a P. falciparum-specific polymerase chain reaction (PCR) method to detect the early appearance of parasitized erythrocytes in the blood prior to detection by conventional microscopy, and found that the parasitemia was detected first in five animals by the PCR method, first in three animals by blood film, with one parasitemia detected simultaneously. We also demonstrated the feasibility of infecting monkeys located in Panama with sporozoites isolated at an insectary in Atlanta, thus documenting the feasibility of similar studies where the insectary and monkey colony are not in the same location. A subsequent attempt to infect these monkeys using sporozoites was not successful, suggesting that this model of human malaria is not yet ready for routine use in vaccine or drug efficacy screening. This model merits further study because of the importance of testing pre-erythrocytic P. falciparum malaria vaccines and drugs in animals.