Host biological sex directs immune control of the Plasmodium parasite liver stage in mice

Caroline Duncombe^1,2,3Alen S. Poehlman²Ethan N. Conrad^2,3Nilasha Sen^2,3Aaron Ayenew⁴Rebecca C. Blyn^1,2GW McElfresh⁵Elizabeth K.K Glennon²Kenneth Boey^2,3,6Anya C. Kalata^2,3Alexis Kaushansky^4,7Nana Minkah²Melanie J. Shears^2,3,8Sean C Murphy^1,2,3,8,9*

• ¹Graduate Program in Pathobiology, Department of Global Health, University of Washington, Seattle, United States
• ²Center for Emerging and Re-emerging Infectious Diseases (CERID), University of Washington, Seattle, United States
• ³Department of Laboratory Medicine and Pathology, Seattle, United States
• ⁴Seattle Children's Center for Global Infectious Disease Research, Seattle, United States
• ⁵Oregon Health & Science University Oregon National Primate Research Center, Beaverton, United States
• ⁶Department of Comparative Medicine, University of Washington, Seattle, United States
• ⁷University of Washington Department of Pediatrics, Seattle, United States
• ⁸University of Washington Washington National Primate Research Center, Seattle, United States
• ⁹Department of Microbiology, university of Washington, Seattle, United States

Plasmodium parasites, the causative agents of malaria, undergo a complex liver stage involving replication influenced by the spatial heterogeneity of the liver. The liver is known to be one of the most sexually dimorphic organs in the body, yet how biological sex and androgens alter host responses to malaria parasites in the liver remains unclear. Here, we investigated how biological sex and androgen levels influence host-parasite interactions during Plasmodium yoelii liver stage infection. Using spatial transcriptomics, we mapped sex-specific gene expression and cellular composition in the BALB/cJ mouse liver. Androgens significantly impacted parasite survival by reducing infected hepatocyte numbers, with females and orchiectomized (ORX) males showing greater immune activity – Type I interferon (IFN) response and antigen processing – compared to intact males. At homeostasis, males exhibited lower baseline densities of Kupffer cells, monocytes, and dendritic cells in the liver. During infection, these disparities persisted and increased. Intact males displayed reduced recruitment of immune cells and reduced antigen presentation activity, alongside a deficient Type I IFN response, which was robust in females and ORX males. Interestingly, the fold change in Kupffer cell number between infected and mock-infected was similar across groups, implicating the importance of androgen-mediated baseline innate immune cell densities in controlling parasite survival. Our findings highlight the role of biological sex in shaping hepatic immune responses during Plasmodium parasite infection and highlight the importance of considering sex as a biological variable in malaria infection studies.