Baboon (Papio anubis) as a Potential Model for Understanding Immun ological Mechanism of Placental Malaria

Abstract

The human -like structural of the Olive baboon (Papio anubis) placenta and the cyto-adherent property of Plasmodium knowlesi have in for med choice for baboon-P. knowlesi mode l of placental malaria (PM). The Olive baboon model of PM is thus useful in understanding pathophysiology of PM in humans. This study sought to develop and utilize the baboon model of placental malaria. Pregnant baboons were experimentally infected with Plasmodium knowlesi H strain parasites (I xI 06 . They were monitored for parasitaemia and clinical observations recorded from day 2 post infection. Peripheral blood was collected on a weekly basis for haematological and immunolog ical an•alysis while placental tissues were collected via caesarean section, processed and analyzed for patho logica l changes. Our find ings show that parasitaemia development was associated with clinical symptoms lead ing to aborti on and still birth. Pathological findings demonstrated sequestration of P.knowlesi parasites in baqoon placenta coupled with placental damage (massive congestion in placental layers and widespread aggregation of erythrocytes). I mmunologica l findings showed mixed Th l /Th2 responses as well as reduced acquired immune responses in pregnant baboons infected with P. knowlesi. In conclusion this study demonstrates that PM in baboons (experimentally infected with P. knowlesi) leads to clinical symptoms that are associated with poor pregnancy outcomes and high levels of parasitaemia . I mmunologica l and pathological findings in this study correlate well with those observed in humans. Consequent ly, the baboon - P. knowlesi model of malaria i s a promising model of choice in the study malaria during pregnancy.