A replication-competent late liver stage–attenuated human malaria parasite
Debashree Goswami, … , Ashley M. Vaughan, Stefan H.I. Kappe
Debashree Goswami, … , Ashley M. Vaughan, Stefan H.I. Kappe
Published June 2, 2020
Citation Information: JCI Insight. 2020;5(13):e135589. https://doi.org/10.1172/jci.insight.135589.
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Research Article Infectious disease Vaccines

A replication-competent late liver stage–attenuated human malaria parasite

Abstract

Whole-sporozoite vaccines engender sterilizing immunity against malaria in animal models and importantly, in humans. Gene editing allows for the removal of specific parasite genes, enabling generation of genetically attenuated parasite (GAP) strains for vaccination. Using rodent malaria parasites, we have previously shown that late liver stage–arresting replication-competent (LARC) GAPs confer superior protection when compared with early liver stage–arresting replication-deficient GAPs and radiation-attenuated sporozoites. However, generating a LARC GAP in the human malaria parasite Plasmodium falciparum (P. falciparum) has been challenging. Here, we report the generation and characterization of a likely unprecedented P. falciparum LARC GAP generated by targeted gene deletion of the Mei2 gene: P. falciparum mei2–. Robust exoerythrocytic schizogony with extensive cell growth and DNA replication was observed for P. falciparum mei2– liver stages in human liver-chimeric mice. However, P. falciparum mei2– liver stages failed to complete development and did not form infectious exoerythrocytic merozoites, thereby preventing their transition to asexual blood stage infection. Therefore, P. falciparum mei2– is a replication-competent, attenuated human malaria parasite strain with potentially increased potency, useful for vaccination to protect against P. falciparum malaria infection.

Authors

Debashree Goswami, William Betz, Navin K. Locham, Chaitra Parthiban, Carolyn Brager, Carola Schäfer, Nelly Camargo, Thao Nguyen, Spencer Y. Kennedy, Sean C. Murphy, Ashley M. Vaughan, Stefan H.I. Kappe

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Figure 6

P.falciparum mei2– day 7 liver stages display severe differentiation defects and cannot form exoerythrocytic merozoites.

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P.falciparum mei2– day 7 liver stages display severe differentiation de...
Liver tissue sections from FRG NOD huHep mice infected with P. falciparum NF54 or P. falciparum mei2– sporozoites were prepared on day 7 of liver stage development and used for IFA. (A) IFAs for CSP (green), BiP (red), and DNA (blue) in P. falciparum NF54 day 7 liver stages show further maturation and formation of distinct PPM invaginations preceding the development of exoerythrocytic merozoites (upper panel) while CSP localization for P. falciparum mei2– is aberrant (lower panel). In P. falciparum NF54 there is pronounced segregation of the ER in preparation for exoerythrocytic merozoite formation, but this does not occur in P. falciparum mei2–. (B) IFAs comparing development of the organelles mitochondria (mHSP70, green) and apicoplast (ACP, red) between NF54 (upper panel) and P. falciparum mei2– (lower panel) on day 7. The mitochondria and apicoplast have undergone segregation inside exoerythrocytic merozoites in P. falciparum NF54, while in P. falciparum mei2– they remain branched and do not segregate. Scale bar: 7 μm.