The impact of size on particle drainage dynamics and antibody response

Simon Zinkhan,Anete Ogrina,Ina Balke,Gunta Reseviča,Andris Zeltins,Simone De Brot,Cyrill Lipp,Xinyue Chang,Lisha Zha,Monique Vogel,Martin F Bachmann,Mona O Mohsen

doi:10.1016/j.jconrel.2021.01.012

Abstract

Vaccine-induced immune response can be greatly enhanced by mimicking pathogen properties. The size and the repetitive geometric shape of virus-like particles (VLPs) influence their immunogenicity by facilitating drainage to secondary lymphoid organs and enhancing interaction with and activation of B cells and innate humoral immune components. VLPs derived from the plant Bromovirus genus, specifically cowpea chlorotic mottle virus (CCMV), are T = 3 icosahedral particles. (T) is the triangulation number that refers to the number and arrangements of the subunits (pentamers and hexamers) of the VLPs. CCMV-VLPs can be easily expressed in an E. coli host system and package ssRNA during the expression process. Recently, we have engineered CCMV-VLPs by incorporating the universal tetanus toxin (TT) epitope at the N-terminus. The modified CCMVTT-VLPs successfully form icosahedral particles T = 3, with a diameter of ~30 nm analogous to the parental VLPs. Interestingly, incorporating TT epitope at the C-terminus of CCMVTT-VLPs results in the formation of Rod-shaped VLPs, ~1 μm in length and ~ 30 nm in width. In this study, we have investigated the draining kinetics and immunogenicity of both engineered forms (termed as Round-shaped CCMVTT-VLPs and Rod-shaped CCMVTT-VLPs) as potential B cell immunogens using different in vitro and in vivo assays. Our results reveal that Round-shaped CCMVTT-VLPs are more efficient in draining to secondary lymphoid organs to charge professional antigen-presenting cells as well as B cells. Furthermore, compared to Rod-shaped CCMVTT-VLPs, Round-shaped CCMVTT-VLPs led to more than 100-fold increased systemic IgG and IgA responses accompanied by prominent formation of splenic germinal centers. Round-shaped CCMVTT-VLPs could also polarize the induced T cell response toward Th1. To our knowledge, this is the first study investigating and comparing the draining kinetics and immunogenicity of one and the same VLP monomer forming nano-sized icosahedra or rods in the micrometer size.

Highlights

In 1956, Crick and Watson have stated that “it is a striking fact that almost all small viruses are rods or spheres”, “These shells are con structed from a large number of identical protein molecules, of small or moderate size, packed together in a regular manner” [1]
The tetanus toxin (TT) epitope was genetically fused to the capsid protein (CP) of chlorotic mottle virus (CCMV)-Virus-like particles (VLPs) as has been previously described for our newly developed platform derived from cucumber-mosaic virus-like particles (CuMVTT-VLPs) [34]
We have studied the following cells for their ability to interact with CCMVTT-VLPs: lymphoid-derived dendritic cells (DCs) characterized by CD8+CD11c+, conventional DCs characterized by CD8− CD11c+, macrophage-derived cells char acterized by CD11b+ and macrophages characterized by CD11b+F4/80+ as well as B cells identified by CD19+ or more generally by CD45R/ B220+

Summary

Introduction

In 1956, Crick and Watson have stated that “it is a striking fact that almost all small viruses are rods or spheres”, “These shells are con structed from a large number of identical protein molecules, of small or moderate size, packed together in a regular manner” [1]. Many virus capsids are made up of multiple copies of a single coat protein (CP) arranged in an icosahedral or a helical-shaped geometry [2,3]. Triangulation refers to the number and arrangements of the subunits (pentamers and hexamers) of the coat protein of a virus or a VLP. It usually serves as a rough in dicator of size. The arrangement of CPs of VLPs in helical or rod-shape geometry is possible; tobacco-mosaic virus (TMV) is a well char acterized representative of this category. VLPs derived from the bacteriophage Qβ can assemble in a rod-shaped par ticle following the mutation of five amino acid (a.a.) residues in the FG loop of its CP [20]

Methods

Results

Conclusion