Towards a Humanized Mouse Model of Liver Stage Malaria Using Ectopic Artificial Livers

Shengyong Ng,Sangeeta N Bhatia,Kelly R Stevens,Nil Gural,Maria M Mota,Ani Galstian,Sandra March

doi:10.1038/srep45424

Abstract

The malaria liver stage is an attractive target for antimalarial development, and preclinical malaria models are essential for testing such candidates. Given ethical concerns and costs associated with non‐human primate models, humanized mouse models containing chimeric human livers offer a valuable alternative as small animal models of liver stage human malaria. The best available human liver chimeric mice rely on cellular transplantation into mice with genetically engineered liver injury, but these systems involve a long and variable humanization process, are expensive, and require the use of breeding-challenged mouse strains which are not widely accessible. We previously incorporated primary human hepatocytes into engineered polyethylene glycol (PEG)-based nanoporous human ectopic artificial livers (HEALs), implanted them in mice without liver injury, and rapidly generated human liver chimeric mice in a reproducible and scalable fashion. By re-designing the PEG scaffold to be macroporous, we demonstrate the facile fabrication of implantable porous HEALs that support liver stage human malaria (P. falciparum) infection in vitro, and also after implantation in mice with normal liver function, 60% of the time. This proof-of-concept study demonstrates the feasibility of applying a tissue engineering strategy towards the development of scalable preclinical models of liver stage malaria infection for future applications.

Highlights

Malaria affects 250 million people and causes more than half a million deaths each year[1]
Since rodent Plasmodium sporozoites infect primary human hepatocytes in vitro[31], and due to greater accessibility to rodent compared to human Plasmodium sporozoites, initial experiments were performed with a reporter strain of rodent Plasmodium berghei (Pb) that expresses both green fluorescent protein (GFP) and firefly luciferase (Pb-GFP-luc)[32], enabling a live infection read-out by IVIS bioluminescence imaging (BLI)
When human hepatoma Huh7.5 cells, which are highly infectible with Pb sporozoites[33], were encapsulated in PEGDA hydrogels and exposed to Pb-GFP-luc sporozoites[32], no BLI signal was observed at 48 h post-exposure (Fig. 1B)

Summary

Introduction

Malaria affects 250 million people and causes more than half a million deaths each year[1]. We sought to establish an implantable model of liver stage Plasmodium infection of primary human hepatocytes in PEG-based HEALs. We first redesigned the biomaterial scaffold to support sporozoite entry by synthesizing macroporous PEG cryogels. We implanted p-HEALs in the intraperitoneal (IP) space of nude mice and demonstrated p-HEAL infection with three Plasmodium species in vivo in the absence of host liver injury Together, these data demonstrate the feasibility of creating a humanized mouse model of liver stage human malaria using tissue engineering rather than genetic approaches. This strategy may offer an efficient and scalable method to establish preclinical models of liver stage human malaria

Methods

Results

Conclusion