Distinct gastrointestinal microbial signatures predict parasite levels in controlled Plasmodium infections in both rhesus macaques and humans.

Functions of the gastrointestinal (GI) microbiome include maintenance of immune homeostasis and protection against infectious disease. Current assessments of the role of the GI microbiome in Plasmodium infection have been primarily conducted using mouse models and observational human cohorts. Here, we experimentally assessed associations between pre-infection GI microbiome composition and acute Plasmodium parasitemia using 16S rRNA sequencing and samples from rhesus macaques (RMs) and adult humans enrolled in a previously conducted controlled human malaria infection (CHMI) trial (NCT04072302) originally designed to test the efficacy of KAF156, a novel imidazolopiperazine class of antimalarial drugs. We identified distinct pre-infection 16S microbial signatures that were associated with increased risk for above median parasitemia in RMs infected with P. fragile and CHMI participants infected with P. falciparum. Further, we identified a Bifidobacterium feature set that accurately stratified parasitemia risk and could therefore serve as a foundation for a potential biomarker panel to aid prevention efforts in malaria endemic regions. Together, our findings demonstrate that pre-infection GI microbiome composition is indicative of risk for Plasmodium parasitemia, and our observation that the pre-infection microbiome-P. fragile dynamic in RMs mirrors the pre-infection microbiome-P. falciparum interaction in CHMI participants supports the future use of this model in pre-clinical investigations of novel microbiome-targeting approaches to reduce malaria burden.