In Vivo Behavior of Systemically Administered Encapsulin Protein Nanocages and Implications for their use in Targeted Drug Delivery

Abstract

Encapsulins, self‐assembling protein nanocages derived from prokaryotes, are promising nanoparticle‐based drug delivery systems (NDDS). However, the in vivo behavior and fate of encapsulins are poorly understood. In this study, we probe the interactions between the model encapsulin from Thermotoga maritima (TmEnc) and key biological barriers encountered by NDDS. Here, a purified TmEnc formulation that exhibited colloidal stability, storability, and blood compatibility was intravenously injected into BALB/c mice. TmEnc had an excellent nanosafety profile, with no abnormal weight loss or gross pathology observed, and only temporary alterations in toxicity biomarkers detected. Notably, TmEnc demonstrated immunogenic properties, inducing the generation of nanocage‐specific IgM and IgG antibodies, but without any prolonged pro‐inflammatory effects. An absence of antibody cross‐reactivity also suggested immune‐orthogonality among encapsulins systems. Moreover, TmEnc formed a serum‐derived protein corona on its surface which changed dynamically and appeared to play a role in immune recognition. TmEnc's biodistribution profile further revealed its sequestration from the blood circulation by the liver and then biodegraded within Kupffer cells, thus indicating clearance via the mononuclear phagocyte system. Collectively, these findings provide critical insights into how encapsulins behave in vivo, thereby informing their future design, modification, and application in targeted drug delivery.This article is protected by copyright. All rights reserved

Heterologous Prime-Boost with Immunologically Orthogonal Protein Nanoparticles for Peptide Immunofocusing

“…[We note that a recent report shows no immunological cross-reactivity in BALB/c mice between encapsulins from T. maritima and Quasibacillus thermotolerans, in spite of the existence of approximately 22% sequence identity between these proteins. 30 These encapsulin cousins are quite different in size, the former being 24 nm in diameter (T = 1) and the latter 42 nm (T = 4), although we do not assume that this is the source of their immunological orthogonality. ]…”

“…A recent report from Care and colleagues showed that a single administration of encapsulin particles from the bacterium Thermotoga maritima in BALB/c mice was benign, producing no signs of physical distress or increases in the serum levels of several proinflammatory cytokines. 30 The same T. maritima encapsulins were used to recombinantly display foreign protein domains such as the Matrix protein 2 ectodomain of influenza A virus 21 as a protomer loop insertion and a truncated form of the gp350 receptor-binding domain from Epstein−Barr virus as a linear extension from the protomer's C-terminus. 20 The former particle was administered to mice with Freund's adjuvant and the latter with the Sigma adjuvant system.…”

Internalization of transferrin-tagged Myxococcus xanthus encapsulins into mesenchymal stem cells

“…We have already discussed this problem partially: we presently know that, at least, Quasibacillus thermotolerans encapsulin-containing cells do not cause an immune response when implanted into mice [ 59 ] and rats [ 60 ]. In addition, an article was recently published evaluating in vivo behavior of Thermotoga maritima encapsulins administered intravenously into mice [ 61 ]. The work demonstrated that IV-injected Thermotoga maritima encapsulins exhibited an excellent safety profile.…”

Looking back, moving forward: protein corona of lipid nanoparticles

“…As a necessary consequence of adsorption theory, it can be speculated that the properties of the PC and their relative abundance are dynamically changing in nature. [161][162][163] Indeed, the adsorption of proteins on NPs is a competitive and constantly changing complex process. In order to better interpret the changing character, alteration theory is put forward.…”