Stage‐specific effects of host plasma factors on the early sporogony of autologous Plasmodium falciparum isolates within Anopheles gambiae

Abstract

SummaryQuantitatively assessing the impact of naturally occurring transmission-blocking (TB) immunity on malaria parasite sporogonic development may provide a useful interpretation of the underlying mechanisms. Here, we compare the effects of plasma derived from 23 naturally infected gametocyte carriers (OWN) with plasma from donors without previous malaria exposure (AB) on the early sporogonic development of Plasmodium falciparum in Anopheles gambiae. Reduced parasite development efficiency was associated with mosquitoes taking a blood meal mixed with the gametocyte carriers' own plasma, whereas replacing autologous plasma with non-immune resulted in the highest level of parasite survival. Seven days after an infective blood meal, 39.1% of the gametocyte carriers' plasma tested showed TB activity as only a few macrogametocytes ingested along with immune plasma ended up as ookinetes but subsequent development was blocked in the presence of immune plasma. In other experiments (60.9%), the effective number of parasites declined dramatically from one developmental stage to the next, and resulted in an infection rate that was two-fold lower in OWN than in AB infection group. These findings are in agreement with those in other reports and go further by quantitatively examining at which transition stages TB immunity exerts its action. The transitions from macrogametocytes to gamete/zygote and from gamete/zygote to ookinete were identified as main targets. However, the net contribution of host plasma factors to these interstage parasite reductions was low (5-20%), suggesting that irrespective of the host plasma factors, mosquito factors might also lower the survival level of parasites during the early sporogonic development.

Avian malaria: a new lease of life for an old experimental model to study the evolutionary ecology ofPlasmodium

“…It is unlikely that parasitaemia bears directly on mosquito infectivity. Parasitaemia, however, is correlated with several in-host factors, including host immunity and metabolic profiles which may affect the likelihood of mosquito infection [54]. Interestingly, we found a significant positive relationship between blood parasitaemia and the volume of blood ingested by mosquitoes ( figure 5).…”

Larval nutritional stress affects vector life history traits and human malaria transmission

“…The level of gametocytemia ranged from 56 to 152 gametocytes per μl (see Table S1 and the ESM for details on carrier selection). Venous blood was collected in heparinized tubes and centrifuged at 3,000 rpm at 37 °C for 3 minutes, and the plasma was replaced by the same volume of European AB serum in order to limit the potential effect of human transmission blocking immunity57. As a negative control (uninfected mosquitoes), females were fed on the same blood in which the gametocytes were heat-inactivated58 (see the ESM for details).…”

Plasmodium falciparum Produce Lower Infection Intensities in Local versus Foreign Anopheles gambiae Populations

“…A venous blood sample of up to 8 ml was taken from selected carriers with at least 20 gametocytes/µl of blood (considering an average of 8000 white blood cells/µl). In order to limit the potential effect of human transmission blocking immunity [72], the blood was first centrifuged at 2000 rpm at 37°C for 3 minutes and the serum changed to European naive AB serum with 0.225 UI heparin/ml. 500 µl of reconstituted blood was added to 3 membrane feeders/mosquito strain maintained by water jackets at 37°C.…”