Vaccination in a humanized mouse model elicits highly protective PfCSP-targeting anti-malarial antibodies

Sven Kratochvil,Usha Nair,Marie Pancera,Arne Schön,Peter D Kwong,Marlon Dillon,Prabhanshu Tripathi,Reda Rawi,Kai Xu,Lawrence T Wang,Johan Arnold,Gwo-Yu Chuang,Brian Bonilla,Neville K Kisalu,Facundo D Batista,Patience K Kiyuka,Li Ou,Baoshan Zhang,Kathrin H Kirsch,Michael T Waring,Joseph R Francica,Azza H Idris,Eleonora Melzi,Robert A Seder,Mateo Reveiz,Barbara J Flynn,Tracy Liu,Kareen Seignon,Yongping Yang,Ying‐Cing Lin ,Lais Pereira ,Chen‐Hsiang Shen ,John E Warner

doi:10.1016/j.immuni.2021.10.017

Abstract

Repeat antigens, such as the Plasmodium falciparum circumsporozoite protein (PfCSP), use both sequence degeneracy and structural diversity to evade the immune response. A few PfCSP-directed antibodies have been identified that are effective at preventing malaria infection, including CIS43, but how these repeat-targeting antibodies might be improved has been unclear. Here, we engineered a humanized mouse model in which B cells expressed inferred human germline CIS43 (iGL-CIS43) B cell receptors and used both vaccination and bioinformatic analysis to obtain variant CIS43 antibodies with improved protective capacity. One such antibody, iGL-CIS43.D3, was significantly more potent than the current best-in-class PfCSP-directed antibody. We found that vaccination with a junctional epitope peptide was more effective than full-length PfCSP at recruiting iGL-CIS43 B cells to germinal centers. Structure-function analysis revealed multiple somatic hypermutations that combinatorically improved protection. This mouse model can thus be used to understand vaccine immunogens and to develop highly potent anti-malarial antibodies.

Highlights

Plasmodium falciparum is the etiological agent of malaria, a vector-borne infectious disease with an estimated disease burden of 229 million cases and 409,000 deaths in 2019 alone (World Health Organization, 2020)
We developed a one-step CRISPR-Cas9-induced homology-directed repair (HDR) approach (Lin et al, 2018; Wang et al, 2021) and applied this technique to insert inferred human germline CIS43 immunoglobulin (Ig)H and IgK chains at their respective native mouse loci (Lin et al, 2018; Wang et al, 2021). Using this KI model, we demonstrated the utility of immunofocusing: iGL-CIS43 B cell recruitment to germinal centers (GCs) was greater in animals immunized with the junctional peptide rather than full-length P. falciparum circumsporozoite protein (PfCSP)
CIS43 uses heavy chain (HC) variable genes VH13*03, DH4-23*01, and JH3*02 and the cognate light chain (LC) variable genes Vk4-1*01 and Jk4*01; it was originally isolated from a malaria-naive participant exposed to radiation-attenuated live SPZs (Seder et al, 2013)

Summary

Introduction

Plasmodium falciparum is the etiological agent of malaria, a vector-borne infectious disease with an estimated disease burden of 229 million cases and 409,000 deaths in 2019 alone (World Health Organization, 2020). While both medical and non-medical interventions, such as artemisinin-based combination therapies and insecticide-treated nets, have proven to be highly effective, these measures are offset by the appearance of drug-resistant parasite strains and insecticide-resistant mosquitos (Phillips et al, 2017). Sporozoites (SPZs), the infectious form of Plasmodium, are injected into the skin and blood; they travel to the liver to infect hepatocytes and initiate the infection. The P. falciparum circumsporozoite protein (PfCSP), comprised of an N terminus, a central repeating tetrapeptide region, and a C terminus, is the most abundant protein on the SPZ surface and is required for motility and hepatocyte invasion (Cerami et al, 1992; Tewari et al, 2002)

Results

Discussion

Conclusion