Virus engineering functionalization and stabilization

Mateu, ; Chiu et al. Culver et al. Thus, the rational engineering of additional electrostatic interactions between capsid subunits could provide a general approach for the thermal stabilization of viral particles. Compared with the introduction of disulfide bonds, introduction of electrostatic and especially Coulombic interactions may have the advantage of being much less stereochemically demanding. A proof of principle for this approach is provided by a recent study using FMDV. These are intrinsically highly thermolabile and readily dissociate into pentamers, which are much less immunogenic than whole viral particles.

As a consequence, transportation of the vaccine requires a strict and expensive cold chain, which is prone to failures in many countries where this economically very important disease is prevalent. Thus, there is a clearly perceived need to develop FMD vaccines that are less dependent on a faultless cold chain Hegde et al. As a step in that direction, the FMDV virion has been rationally engineered to increase its stability against thermal dissociation into pentameric subunits, without disrupting any of the many biological functions needed for its infectivity.

Normal infectivity was required because the virus must be grown during vaccine production. A systematic alanine-scanning analysis of the interpentamer interfaces in the FMDV virion was first undertaken to try and find functionally tolerant sites for mutation. The vast majority of the interfacial residues were found to be required for infectivity Mateo et al. Some of the few amino acid side chains located at or near the interpentamer interfaces, and either predicted or found to be dispensable for infectivity, were replaced by others that had the potential to establish either disulfide bonds or new electrostatic interactions between pentamers.

Two of the five electrostatically modified virions were normally infectious, genetically stable and antigenically indistinguishable from the natural virus, but showed as intended a dramatically increased thermal stability against dissociation into pentamers, relative to the non-mutated virion Mateo et al.

Electrostatic interactions do mediate this stabilizing effect V. The increasing use of virus particles in materials science and nanotechnology has led to a renewed interest in viruses from the physicist's point of view. Several groups have recently started to theoretically or experimentally investigate the mechanical properties of viral particles, considered as physical objects of nanometric size. The mechanical flexibility of several other phage, animal virus and plant virus particles have also begun to be explored by AFM Carrasco et al.

In this approach to virus mechanics, viral particles are physically deformed indented by applying a force through the extremely fine tip of the cantilever in an atomic force microscope.

From the data, the spring constant k of the viral particle can be determined. Different viruses have been shown to differ in mechanical stiffness. A natural mutation in the CCMV capsid that increases the stability in high salt conditions also increases virion stiffness Michel et al.

These and other studies have started to provide some hints on the molecular basis for the mechanical properties of viruses. From a nanobiotechnological point of view, viral particles with increased mechanical stability may be useful for applications in which they may be subjected to high mechanical stress.

They could be useful for many other applications as well, as they may withstand better the action of heat or other physical or chemical agents without losing function see next. Very recently, a mechanical property of viral particles has been rationally manipulated by protein engineering for the first time Carrasco et al. Castellanos, R. Crystallographic studies of MVM and other parvoviruses had shown that ordered segments of the genomic single-stranded DNA interact with DNA-binding sites located at equivalent positions in the capsid inner wall Tsao et al.

A mutational analysis by alanine scanning showed that those capsid-DNA interactions contribute to stabilize the MVM virion against thermal inactivation without particle dissociation Reguera et al. It was then hypothesized that for variants of a same virus species there could be a direct relationship between thermal stability and mechanical rigidity, because an increase in capsid stiffness could impair the spatial displacements of atoms and functional groups associated with a thermally induced change of conformation.

In such a case, the capsid—DNA interactions that thermally stabilize MVM should also contribute to increase its mechanical rigidity, and the DNA-containing virion would be mechanically more rigid than the DNA-free capsid. This prediction was experimentally confirmed using AFM Carrasco et al. As the MVM capsid is structurally nearly unchanged even at the atomic level in the presence or absence of the genomic DNA Kontou et al.

Unexpectedly, for MVM the DNA-mediated increase in stiffness was anisotropic, with the virion being stiffer than the capsid along the threefold and, especially, 2-fold symmetry axes, but not along the 5-fold axes. The predictions of a very simple finite element model supported the proposal that the observed DNA-mediated anisotropic increase in stiffness would be specifically due to the capsid-bound DNA patches Carrasco et al.

This prediction was experimentally tested by removing in the virion-specific capsid—DNA interactions by site-directed mutation of capsid residues at the DNA binding site.

AFM measurements showed that the mutations did not affect the stiffness of the empty capsid, but they did significantly reduce as predicted the difference in stiffness between the DNA-filled virion and the empty capsid Carrasco et al.

From previous knowledge on MVM and the above results, it has been proposed that the DNA-mediated, anisotropic mechanical rigidification of MVM may have arisen from a balance between two selection pressures: on the one hand, the biological advantage of a higher mechanical rigidity that would impair the observed thermally induced inactivation of the virion Reguera et al.

By evolving in the MVM capsid DNA-binding sites closer to the 2-fold and 3-fold axes and farther from the 5-fold axes pores, the genomic DNA may have been recruited to act as an architectural element that mechanically and thermally reinforces the MVM virion, while still allowing the local conformational rearrangements needed for infectivity Carrasco et al.

This model has in turn led to the prediction that mutations of certain capsid residues that impair infectivity would increase the mechanical stiffness, relative to that of the natural capsid; this prediction has been now experimentally confirmed by protein engineering M.

In summary, from a biotechnological point of view, this series of studies has provided: i genetically modified virions of increased mechanical flexibility, by removing DNA—capsid interactions; ii genetically modified capsids of increased mechanical rigidity, by engineering amino acid substitutions at predicted capsid locations; iii a proof of principle that it is possible to rationally manipulate the mechanical properties of viral particles by protein engineering.

The chemical approach has generally involved the functionalization of the viral particle surface or inner wall through a chemically reactive group, either naturally present or genetically engineered. The protein engineering approach has relied in most cases on knowledge-based genetic manipulation of the viral particle to: i present heterologous peptides or proteins on the capsid surface or include them inside the capsid cavity , by incorporating the poly peptides as an extension of a free terminal end of a capsid protein; ii present heterologous peptides on the capsid surface by insertion in exposed loops; iii substitute in a capsid protein one or a few dispensable residues, to provide new sites for covalent cross-linking or non-covalent binding of heterologous inorganic, organic or biological components or, much less frequently, to modify some intrinsic property or functionality of the viral particle itself.

Thanks to the inbuilt features and versatility of the protein-made virus capsids, the above bio chemical and genetic approaches have led to a vast collection of modified viral nanoparticles with remarkable and diverse properties and functions.

More complex genetic modifications of the intrinsic structure and embedded properties and functions of the viral particles themselves and not only for the attachment of heterologous functional elements may have to be attempted for many applications. For virions, where phenotype and genotype are physically coupled, this approach can very productive.

However, for empty capsids and VLPs in general, at least some combinatorial approaches may be technically difficult to implement. Rational protein engineering is and will remain a fundamental approach for the modification of viral particles. Structure—function studies on the self-assembly, physical properties and the molecular mechanisms underlying the complex functions of viral particles are providing part of the knowledge needed for emerging virus engineering projects, including the physical stabilization of viral particles.

In turn, the exploration of uncharted areas of sequence and conformational space of viruses and their protein capsids with applied goals in mind is also throwing new light on the properties and biological function of viruses, and suggesting new approaches in the fight against viral disease. I am indebted to Sir A. Fersht and associates for their help and support there. I also gratefully acknowledge recent past and present members of my group M.

Bocanegra, A. Carreira, M. Castellanos, M. Fuertes, I. Luna, R. Mateo, R. Reguera, V. Almendral and associates, C. Carrasco, P. Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation.

Although safer, these are generally less immunogenic than traditional vaccines [ 1 , 2 ]; thus, several strategies have been exploited to improve the immune response of subunit vaccines.

Examples include the addition of adjuvants, optimization of delivery systems, or the use of particulate antigen assemblies, in which antigens are attached to particles [ 2 ]. In addition, the applicability of subunit vaccines is not restricted to infectious diseases, but may also be used in cancer therapy [ 3 ] and treatment of autoimmune diseases [ 4 , 5 ].

When considering subunit vaccination, there is ample evidence that nanoparticle-anchored antigens are more efficacious than monomeric, soluble ones [ 6 ]. The affinity between the nanoparticle surface and the cell membrane contributes to a more efficient cellular uptake of the anchored antigens when compared to antigens alone [ 7 ]. These cells are the starting point of the adaptive immune response as they detect pathogens, sample them, and migrate to lymph nodes LNs where they present antigens to T- and B-cells thus triggering an immune response [ 7 ].

The pharmacokinetics of nanoparticle-carried antigens is distinct from that of monomeric, soluble antigens. While the latter are diffused into body fluids and diluted upon administration, nanoparticles allow the maintenance of antigen clusters, and those with size ranges of 20— nm are found to have long circulation times [ 10 ].

Another benefit of nanoparticles is the likelihood of enhanced transport to LNs, which augments antigen uptake by LN-resident DCs and subsequent activation of immunological responses by T- and B- cells [ 7 ]. A further advantage of nanoparticle-based vaccines is the possibility of retention at the injection site, which enhances antigen uptake and presentation by DCs [ 6 ]. Natural-derived nanoparticles are biocompatible and hydrophilic, rendering them strong contenders for biomanufacturing purposes.

Among these, protein-based nanocages with self-assembling properties such as ferritin and virus-like particles [ 11 ] are especially interesting for vaccine development as they mimic both the size and structure of pathogens and are amenable to surface conjugation of antigens to promote the interaction with immune cells [ 12 ].

Ferritin can be found in almost all living organisms, including bacteria, fungi, plants, and animals [ 13 ]. Its major physiological function is to store iron in an insoluble non-toxic form while keeping it bioavailable intracellularly by converting it to its soluble form [ 14 ], having an important role in iron homeostasis. It also provides a protective effect against toxicities involving free iron, such as the generation of reactive oxygen species which can damage cellular machinery and lead to cell death [ 15 ].

Ferritin has recently emerged as a promising platform for antigen display [ 16 ]. Besides vaccine development, ferritin has been used in nanobiotechnology for drug delivery, biomimetic synthesis, bioimaging, and cell targeting [ 17 , 18 , 19 , 20 , 21 ]. Schematic overview of the topics discussed in this review: ferritin characteristics, functionalization, and recombinant expression of ferritin nanoparticles for antigen-display applications.

Ferritin nanoparticles ubiquitously found in nature contain a hollow core of inner and outer diameters of 8 and 12 nm, respectively, that can internalize up to iron atoms in the form of ferric oxyhydroxide [ 22 ], with variable amounts of phosphate [ 23 ]. The ferritin structure of mammalians, amphibians, plants, and bacteria has been reviewed elsewhere [ 24 ]. Ferritin particles isolated from vertebrates are composed of two types of subunits, H-chain heavy, 21 kDa and L-chain light, 19 kDa , whereas those found in plants and bacteria contain only one type resembling the H-chain of vertebrates [ 24 ].

Each ferritin particle is made up of 24 identical or homologous subunits that self-assemble in octahedral symmetry such that small channels are formed at the 4-fold and 3-fold symmetry axes Figure 2 a,b. These channels allow the passage of iron and other ions or small molecules [ 22 ], with iron being guided via the 3-fold channels [ 25 ]. Additionally, a long loop L of about nineteen residues connects the C-terminal of B-helix to the N-terminal of C-helix.

The N-terminal, L loop, and A- and C-helices are solvent-accessible, while the C-terminal, and B- and D-helices face the inner side of the ferritin nanocage [ 24 ].

Native ferritin structure. Quaternary structure of human L-chain ferritin PDB ID: 2FFX [ 26 ] , consisting of 24 subunits, assembled in octahedral symmetry around the a 4-fold and b 3-fold axes. X-ray diffraction experiments conducted on horse spleen apoferritin suggested that stable dimers are the first intermediates in self-assembly, as dimers interact along most of their length and have a larger mutual area of contact than those around the 3- or 4-fold axes [ 29 ].

The second step of the assembly was hypothesized to be the formation of hexamers by aggregation of dimers around the triagonal axis [ 29 ] because, compared to the 4-fold axis, the contact region around the 3-fold is greater.

In addition, the contact between subunits around the 4-fold pore is tenuous lined by the short E-helices thus making it unlikely for stable symmetrical tetramers to occur. Gerl and Jaenicke [ 30 ] were the first to propose the self-assembly mechanism of ferritin when the reconstitution of ferritin monomers of horse spleen apoferritin was monitored through chemical cross-linking and subsequent spectroscopic analysis. The overall proposed mechanism is described by Equation 1 :.

More recently, Sato et al. Differently from the hetereopolymeric horse spleen ferritin, monomers and trimers were reported to be unlikely intermediates during the assembly of homopolymeric ferritin. Sato et al. Although the SAXS profile is consistent with the work developed by Gerl and Jaenicke [ 30 ] ferritin assembly follows a second-order reaction and is based on the association of oligomers , the simplified model presented in Equation 2 had some limitations such as being concentration-dependent and unable to identify all possible intermediates according to SAXS data.

There is evidence that native ferritin can undergo post-translational modifications, including change in isoelectric point [ 32 ], phosphorylation [ 33 ], and glycosylation [ 34 ]. Physiologically, most of the synthesized ferritin remains within the cell where it is responsible for maintaining the intracellular iron homeostasis. There, both H- and L-chains of human ferritin are unglycosylated, and their ratio varies between different cell types and maturation stages.

Ferritin can also be found in the plasma consisting mainly of N -glycosylated L-chain [ 34 ] that may be sialylated [ 35 ]. Glycosylation may influence the removal rate of ferritin from the plasma by hepatocytes, the major cell type responsible for clearing plasma ferritins.

These cells enclose in their membrane a specific receptor for both glycosylated and non-glycosylated ferritin [ 36 ], and there is evidence that glycosylated ferritin is cleared at a slower rate than non-glycosylated ferritin, determining a significantly longer half-life for the glycosylated ferritins [ 34 ].

Microbes e. Most laboratory-produced ferritin is unglycosylated. This results from either i using expression systems that are unable to perform glycosylation E. The latter is distinct from the others since ferritin is produced in its unglycosylated form through genetic engineering. In this case, suppressing glycosylation sites on ferritin avoids glycan-induced steric hindrance or undesired interactions between the glycan and chemical groups on antigens of interest AOI that may be fused to the ferritin; that else could prevent the antigen from acquiring its natural tertiary structure, and thus its immunogenic potential is at an impasse.

Ferritin sources used for ferritin-based vaccine production, expression system, and putative N -glycosylation sites. While consensus sequence N 8 -Y 9 -S 10 of the L-chain may lie on the outside of the assembled molecule [ 75 ], the consensus sequence on the H-chains may occur at an intersubunit interface [ 75 ], thus prohibiting N -glycosylation bond. Other mutations have also been performed to improve the use of ferritin nanoparticles in nanobiotechnology: i the point mutation R64K in Pyrococcus furiosus ferritin eliminated a potential cleavage site [ 9 ], ii ligands with affinity for thiol groups were conjugated to engineered ferritin mutants from Archaeoglobus fulgidus and P.

Conversely, the conjugation of a trimannose moiety to ferritin nanoparticles led to a pronounced accumulation of these particles on follicular DCs i. Hence, the presence of even simple glycans on ferritin could be beneficial, potentially directing vaccine nanoparticles to the follicular LNs network and prolonging the half-life of ferritin-based vaccines upon administration. Ferritin nanoparticles contain three distinct exploitable interfaces: the interior and external surfaces, and the intersubunit regions.

All are amenable to manipulation through chemical and genetic engineering to render them useful nanocages in biotechnology. Usually, ferritin subunits assemble spontaneously upon expression. Huard et al. In a different study [ 77 ], the interface of ferritin subunits was genetically modified to yield nanocages capable of disassembly at pH 4.

The hollow cavity of ferritin can be engineered to encapsulate and transport several molecules with distinct purposes, including peptides, drugs, imaging agents, and polymers [ 14 ]. In addition, it can also act as a size-constrained reaction vessel for nanomaterial synthesis [ 18 ]. By adding targeting moieties to the external surface of ferritin, the encapsulated molecules can be delivered in a site-specific manner.

Additionally, the outer surface of ferritin can be engineered to impart increased circulatory half-life e. In the following sections, functionalization of the outer surface of ferritin will be thoroughly described since this interface enables antigen presentation for the development of ferritin-based vaccines Figure 3.

Technologies used for the design of functionalized ferritin nanoparticles. The outer surface of ferritin Ft nanoparticles can be functionalized with a protein of interest POI by genetic fusion green-shaded and modular assembly blue-shaded.

CID—chemically inducible dimerization. Delivering antigens anchored to a scaffold can be achieved by genetic fusion of the gene encoding the AOI to the gene encoding the protein scaffold. After expression, self-assembly of the protein scaffold subunits results in multimerization and ordered display of antigens.

For efficient presentation and interaction with cellular receptors, it is crucial that antigens retain their structural stability and conformation. However, it is challenging to recombinantly express antigens fused to a scaffold without impairing their stability or conformation, and consequently their activity.

For instance, the antigen may interfere with intersubunit interactions of the protein scaffold, hindering its assembly into nanoparticles. In addition, the optimal host for protein scaffold expression may not be optimal for AOI expression, or vice-versa.

Since Li et al. Surface functionalization of ferritin nanoparticles by genetic fusion for antigen-display applications. One example is the work of Kanekiyo et al. By fusing the HA gene to the N-terminal of ferritin, which is opportunely located around the 3-fold axis, HA monomers were in proximity to interact with each other, resulting in reciprocal stabilization and allowing for the oligomerization of conformation-dependent trimeric antigens.

The ferritin-HA nanoparticles not only acquired the desired physical properties final product homogeneity, native conformation, and symmetric display but also enhanced the immunological potency, compared to the licensed inactivated vaccine—the nanoparticle vaccine-elicited HA antibody titters over fold higher in immunized mice.

The promising results obtained with this design have motivated the development of three vaccines against influenza, to be tested in Phase 1 clinical trials ClinicalTrials. No significant adverse effects were detected. The approach by Kanekiyo et al.

One of these vaccine candidates was reported to elicit rapid immune responses after a single immunization and being highly protective in a mouse challenge model and is now currently been assessed in a Phase 1 clinical trial ClinicalTrials.

Compared to soluble gp, the neutralization capacity of the gpferritin nanoparticle increased to fold in immunized mice. Kim et al. Antigens derived from human viruses are prone to the formation of inclusion bodies when expressed in bacterial hosts, and their display in multimeric nanoparticles remains a challenge. In order to improve the production of nanoparticle vaccines in bacterial hosts, RNA was implemented as a molecular chaperone to improve protein folding and enable soluble expression in bacteria.

Nanoparticles generated in more than a single stage i. Compared to genetic fusion, modular assembly adds complexity to the process as the number of production and purification steps increases, yet it bypasses the challenges associated with genetic fusion.

Distinct approaches of modular assembly to functionalize the outer surface of ferritin nanoparticles are depicted in Figure 3 and summarized in Table 3. Surface functionalization of ferritin nanoparticles by the modular assembly for antigen-display applications.

The classic approach of the modular assembly comprises chemical conjugation between the nanoparticle and a protein of interest POI using crosslinkers that interact with reactive species on the side chains of the proteins. The sulfhydryl group —SH of cysteine residues Cys is traditionally exploited since this amino acid rarely exists on the surface of proteins and allows site-specificity when a single Cys is available on the protein.

The other end of the crosslinker may react with primary amines —NH 2 , found in lysine residues Lys and at the N-terminal of a protein, or, less frequently, with hydroxyl groups —OH , found in serine Ser and threonine Thr residues and at the C-terminal of a protein.

Chemical crosslinking to decorate the outer surface of ferritin has been reported in the literature. Falvo et al. Primary amines available on the antibodies were acetylated at the expense of N -hydroxy succinimide NHS , yielding IgG-PEG-Mal, followed by alkylation of Cys on the surface of ferritin by the maleimide arm of the crosslinker.

Using a different strategy, Luo et al. Finally, this molecule was conjugated to available Lys on the surface of ferritin at the expense of NHS. Generally, a protein contains several available primary amines and hydroxyl groups on its surface, thus the final product of chemical crosslinking between proteins is heterogenous and difficult to predict or analyze. Another drawback associated with this method is that Cys residues, added to a genetically engineered protein to offer site-specificity, may interfere with the formation of pre-existing disulfide bonds.

To circumvent the challenges associated with chemical crosslinkers, novel approaches of bioconjugation have been explored, which are addressed next. CID uses a small molecule as an intermediate to induce the binding of two different proteins. Compared to a bifunctional crosslinker used in chemical conjugation, it offers higher affinity and specificity, as well as faster kinetics [ 87 ].

Ducasse et al. Similar to genetic fusion, CID allows for homogeneity of the final product but restricts conjugation to either the N- or C-terminal of the conjugated proteins since the peptides binding to the dimerizer e.

Click chemistry is an alternative method in which unnatural amino acids uAAs , bearing biorthogonal reactive groups, are incorporated in the polypeptide chain of a protein-based nanoparticle.

This type of reaction occurs between functional groups and is characterized by being fast, selective, and having high yields. While this approach offers the advantage of enabling the conjugation of proteins at nearly any site in the uAA-containing protein, it requires artificial amino acid incorporation, metabolic engineering, and additional synthetic steps thus considerably increasing process complexity and cost and hampering scale-up.

In addition, the conjugate protein must be functionalized with a ligand with affinity to the uAA. This strategy was used by Khoshnejad et al. Enzyme-mediated conjugation is similar to CID, but instead of using a dimerizer as an intermediate to bind two peptides, it uses a catalyzer i.

The anti-EGFR nanobody 7D12 was engineered to present a glutamine Q residue at the C-terminal, which becomes activated upon addition of transglutaminase and conjugates to a genetically added Lys-Lys at the N-terminal of ferritin [ 73 ].

Enzyme-mediated conjugation does not restrict the attachment of a protein to either the C- or N-terminal of ferritin as in genetic fusion and CID approaches. For instance, tyrosinase enables direct conjugation of solvent-exposed tyrosine residues Tyr to Cys sulfhydryl groups. Genetically modified endorphin to present Tyr at its terminal was successfully activated and irreversibly conjugated to MS2 viral capsids, each subunit of the mer nanoparticle containing a single native Cys residue at position 47 [ 88 ].

However, as aforementioned, the mutation of a protein to add a Cys residue amenable of conjugation may interfere with the formation of native disulfide bonds. CnaB2 contains a single isopeptide bond, and by splitting it into peptide and protein fragments followed by rational modification of the parts, a peptide tag of 13 amino acids SpyTag can spontaneously form a stable covalent bond with its protein partner SpyCatcher, amino acids, 15 kDa [ 89 ].

Upon mixture, the proteins conjugate without the need for an intermediate, contrarily to CID and enzyme-mediated conjugation. As discussed above, some modular assembly strategies allow for a flexible selection of the position where the POI is attached to ferritin, while others and genetic fusion are restricted to the C- or N-terminals of ferritin.

When this is the case, most studies opt to fuse the POI to the N-terminal of ferritin to prevent or at least reduce its impact on proper folding of the ferritin subunit, and also because the N-terminal faces the exterior of the nanoparticle. This display is ideally suited for small-sized antigens characterized by a hairpin conformation, such as the Fc binding peptide [ 56 ] and MtrE peptide loops from N.

The functionalization of the C-terminal of ferritin has also been reported. Since the C-terminal faces the inner side of the nanoparticle, it is not surprising that it induces a weaker immune response compared to peptides displayed on the exterior surface [ 38 ].

Interestingly, Lee et al. The future applications of VLPs are always driven by the development of emerging technologies and new requirements of modern life. Keywords: biomaterials; inside encapsulation; nanoparticle; surface bioconjugation; virus-like particle. This website requires cookies, and the limited processing of your personal data in order to function. By using the site you are agreeing to this as outlined in our privacy notice and cookie policy. Abstract Available from publisher site using DOI.

A subscription may be required. Mateu MG 1. Affiliations 1 author 1. Share this article Share with email Share with twitter Share with linkedin Share with facebook.

Abstract Viruses and their protein capsids can be regarded as biologically evolved nanomachines able to perform multiple, complex biological functions through coordinated mechano-chemical actions during the infectious cycle. The advent of nanoscience and nanotechnology has opened up, in the last 10 years or so, a vast number of novel possibilities to exploit engineered viral capsids as protein-based nanoparticles for multiple biomedical, biotechnological or nanotechnological applications.

This chapter attempts to provide a broad, updated overview on the self-assembly and engineering of virus capsids, and on applications of virus-based nanoparticles. Different sections provide outlines on: i the structure, functions and properties of virus capsids; ii general approaches for obtaining assembled virus particles; iii basic principles and events related to virus capsid self-assembly; iv genetic and chemical strategies for engineering virus particles; v some applications of engineered virus particles being developed; and vi some examples on the engineering of virus particles to modify their physical properties, in order to improve their suitability for different uses.

Full text links Read article at publisher's site DOI : Similar Articles To arrive at the top five similar articles we use a word-weighted algorithm to compare words from the Title and Abstract of each citation. Virus engineering: functionalization and stabilization. Invariant polymorphism in virus capsid assembly.