Elucidating the dynamic interactions of Plasmodium falciparum parasites and the mosquito midgut epithelium during ookinete traversal

Abstract

Plasmodium falciparum is the causative agent of malaria, a tropical disease which is transmitted to humans via the bite of an infected female Anopheles gambiae mosquito. The Plasmodium parasite shuttles between humans, where it can cause serious illness and death in vulnerable populations, and Anopheles mosquitoes, who carry the parasite asymptomatically. Upon mosquito ingestion of a blood meal from a malaria-infected human, sexual reproduction and transformation from Plasmodium gamete to motile ookinete form occur within the mosquito midgut approximately 24 hours after feeding. At the same time, ingestion of a blood meal also triggers a cascade of hormonal signaling, largely orchestrated by the steroid hormone 20-hydroxyecdysone (20E), resulting in the initiation of egg development in the mosquito. These two processes are intertwined both temporally and physiologically, as disruption of 20E signaling has been found to also impact ookinete invasion and survival. We aimed to characterize not only how ookinetes are impacted by 20E signaling, but also fundamentally how and where ookinetes invade the mosquito midgut. In Chapter 1, I will give an overview of ookinete biology, the mosquito midgut, and what is known regarding the events of ookinete invasion. In Chapter 2, I investigate the role of oxidative stress in the blood fed midguts of mosquitoes in which 20E signaling has been disrupted. In Chapter 3, I will describe how single cell sequencing of infected mosquito midguts allows us to generate an Anopheles midgut cell atlas, as well as to help characterize ookinete cell tropism and invasion dynamics. In Chapter 5, I will explore how these findings, taken together, provide the field with a novel understanding of how ookinetes may invade the mosquito epithelium and factors which impact ookinete survival within the midgut. Our findings contribute substantially towards a better understanding of the mechanisms underlying ookinete invasion within the mosquito and have potential to be leveraged for strategies targeting ookinetes for suppression of malaria transmission in mosquitoes.