Why study capsid structures?
Scientists have turned viruses into a drug delivery vehicle
Viral infections are not always a bad thing. The abilities of some modified viruses allow scientists to use the infection for the benefit of the human body, for example, to deliver molecules of potent drugs directly to the place of their application. One of these "useful" viruses is the cowpea mosaic virus (CPMV) virus, which usually affects cells of plant origin. Minor changes in the structure of this virus make it possible to use it to diagnose the presence of malignant tumors and to deliver chemotherapy drugs to cancer cells directly, without exposing the rest of the patient's body to the harmful effects of these drugs.
Scientists from The Scripps Research Institute (Perfecting a Viral Pack Mule) have succeeded in turning the CPMV virus into a useful tool. CPMV viruses, devoid of a pathogenic component, are the subject of increased interest from scientists due to the fact that they have about 300 places on the outer and inner surfaces where "payload" molecules can be attached. Since the CPMV virus affects only plant cells, it is absolutely safe for humans, and to eliminate even the most insignificant negative effect on the human body, scientists have created an "empty" variant of the CPMV virus, devoid of any own genetic material, called eVLP (empty virus-like particle).
"eVLP is no longer a virus, it's an empty protein capsule," says Vijay Reddy, one of the leading researchers.
One of the problems that researchers faced when creating a safe eVLP virus was determining the preservation of the original viral structure of CPMV after removing part of the viral genome.
Scientists used for this purpose a shooting technology called X-ray crystallography, which allows to obtain an image of the virus with a sufficiently high resolution. The obtained images showed that the structure of eVLP virus particles is very similar to the structure of the original CPMV particles, which should determine the similarity of the parameters and functions of these particles.
The essence of the work, the article about which (Huynh et al., Crystal Structure and Proteomics Analysis of Empty Virus-like Particles of Cowpea Mosaic Virus) was published in the journal Structure, consists precisely in determining the protein structure of the virus envelope. And their colleagues from Case Western Reserve University and Dartmouth University not so long ago not only received exactly the same shells, but also found out that they, even empty, with the help of an unknown mechanism, cured melanoma in mice – VM
New studies, in which high-quality images were obtained, revealed many features of eVLP particles. Scientists have noticed three places of "split", where the amino acids of the protein body of the viral particle did not connect in the same way as the original virus. Note that in the course of previous studies, scientists were able to identify only one such place. Having information about the position of the "split" sites, scientists will try to place the "payload" molecules on the surface of the particle so that they do not bind to the amino acids remaining in the active state.
These new studies do not yet have practical value in themselves, i.e. their results cannot yet be used for practical purposes. But based on the results obtained, individual vaccines designed for a specific patient and new methods of "molecular therapy" can be created in the future.
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14.04.2016