Oral Presentation 8th International Conference on Plasmodium vivax Research 2022

In vivo assessment of Plasmodium vivax Chesson strain liver stage infection: novel studies to assess hypnozoite formation, persistence, activation and relapse. (80276)

Gigliola Zanghi 1 , Sumana Chakravarty 2 , Hardik Patel 1 , Stephen L Hoffman 2 , B KL Sim 2 , Stefan HI Kappe 1 3 4 , Ashley M Vaughan 1 4
  1. Center for Global Infectious Disease Research Seattle Children's Research Institute, Seattle, WA, United States
  2. Sanaria , Rockville, Maryland , USA
  3. Department of Pediatrics, University of Washington, Seattle, WA, USA
  4. Department of Global Health, University of Washington, Seattle, WA, USA

Gigliola Zanghi & Sumana Chakravarty contributed equally to this abstract as co-first author

 

The main goal of Plasmodium vivax liver stage research is aimed at understanding the formation, persistence and activation of hypnozoite stages, which are the source of recurrent relapses. This research, however, is hampered by several challenges to studying P. vivax (Pv) liver stages in the laboratory, including the limited access to sporozoites (SPZ). Sporozoites are primarily obtained from mosquitoes fed on infected patient blood, causing significant variability in experimental outcomes.

Here, we revisited the use of Chesson strain PvSPZ for analysis of hypnozoite biology. Pv Chesson blood stages were propagated in Saimiri monkeys and used for mosquito feeds to generate PvSPZ (Chesson) that then underwent cryopreservation. We used these to infect human liver-chimeric FRG huHep mice. Furthermore, single cell RNA-seq analysis of PvSPZ (Chesson) was undertaken. 

We observed robust liver infection of FRG huHep mice.  Exo-erythrocytic schizonts matured normally over nine days, when primary exo-erythrocytic merozoites egressed from the liver into the blood. Strikingly, hypnozoites formed frequently and persisted. The hypnozoite:schizont ratio in the infected livers was consistently approximately 40%:60%, constituting the first quantitative determination of Chesson strain hypnozoite frequency. Hypnozoites were viable, activated and caused first relapses after approximately three weeks. This model will allow for consistent profiling of both hypnozoites and schizonts as well as the infected host hepatocytes. To understand if the hypnozoite fate is predetermined in PvSPZ (Chesson), we performed single cell RNA-seq analysis of PvSPZ (Chesson). Preliminary analysis showed enrichment of genes associated with chromatin remodeling in a subset of sporozoites, possibly highlighting a role for epigenetic regulation in hypnozoite formation. Our Chesson strain liver stage model will allow us to gain a better understanding of hypnozoite biology and can aid in the discovery of novel interventions to prevent relapse.