Aims: During pregnancy, Plasmodium falciparum malaria is frequent and associated with maternofetal complications. This could be the consequence of sequestration by several adhesion molecules of parasite-infected red blood cells in syncytiotrophoblast. To investigate the expression of ICAM-1 and CD36, two of the adhesion molecules for Plasmodium falciparum, an immunohistochemical study was carried out in malaria-infected placentas.
Methods and results: Thirty-five infected and 35 noninfected samples were chosen randomly. According to the histological classification of Bulmer, the infected placentas were separated in three groups: active, active chronic and past-chronic infection. CD36 was localized in the cytoplasm of stromal cells of terminal villi of infected or noninfected placentas, but not in syncytiotrophoblast. ICAM-1 was detected in the cytoplasm of stromal and endothelial villous cells in both infected and noninfected placentas and in syncytiotrophoblast of eight infected placentas showing more frequently active than active chronic or past-chronic infection (P < 0.001). The percentage of cells immunostained for CD36 or ICAM-1 was evaluated in the terminal villi. The proportion of villous cells, with ICAM-1 and CD36 immunostaining, was significantly higher in infected vs. noninfected placentas (P < 0.0001) and CD36 was detected more in acute inflammatory vs. past-chronic inflammatory placentas (P < 0.05).
Conclusions: The higher expression of ICAM-1 in infected placentas and its localization in syncytiotrophoblast particularly during acute infection, suggest ICAM-1 can act directly in the sequestration of parasite-infected red blood cells (IRBCs). On the other hand, the expression of CD36 is influenced by the presence of IRBCs without being directly implicated in sequestration of IRBCs. The hyperexpression of these two molecules could explain the high frequency of malaria during pregnancy.