A new Plasmodium falciparum field isolate from Benin in continuous culture: Infectivity of fresh-produced and cryopreserved gametocytes to Anopheles gambiae

Abstract

Transmission-blocking vaccines and drugs are likely to be key interventions in efforts to achieve malaria elimination. However, transmission-blocking studies are reliant upon a limited number of culture-adapted strains of Plasmodium falciparum with limited genetic variability, or on field isolates which are only maintained transiently in the laboratory and therefore not amenable to replication studies. Herein, we investigated the gametocytogenesis capacity and infectivity to Anopheles gambiae mosquitoes of a P. falciparum field isolate collected from a malaria patient from Benin compared to those of NF54 strain. The intraerythrocytic developmental cycle (IDC) was similar in both P. falciparum strains (ranges of parasitaemias were respectively 0.02–11.53% and 0.035–10.5% throughout twelve days of culture). The culture-adapted parasites displayed a significant higher infectivity to An. gambiae compared to that of NF54 (mean oocyst prevalence and intensity: 16.94%, CI95%= [15.15–18.73] vs. 3.13%, CI95%= [2.30–3.96], p < 0.0001 and 3 vs. 1 oocysts/infected mosquito, p = 0.002 respectively). Even after cryopreservation for up to 14 days, gametocytes from the field isolates were capable of infecting An. gambiae mosquitoes at a prevalence of up to 30% with an average of 12 oocysts/ midgut. This new P. falciparum strain will enhance malaria transmission-blocking studies in endemic countries.