A novel type of particle platform for application in biotechnology is provided by the present invention. Said platforms comprise RNA-free particles generated by thermal denaturation and structural remodeling of helical plant viruses. Tobamovir-uses and, in particular, tobacco mosaic virus (TMV) coat protein (CP) subunits, denatured, at high temperatures are specifically self-assembled by two-stage assembly into the spherical particles (SPs) of similar shape and varying size including nanoparticles (SNPs) with a diameter up to 100-150 nm and spherical microparticles (SMPs) with a diameter up to 800 nm and more. The size of said SPs depends on the virus concentration used and, therefore can be controlled. Said SPs are biologically safe, highly stable and highly immunogenic. Said SNPs and SMPs are structurally distinct from viruses presently known. They are unique, having no protein nano-particle analogs in the nature. Said particles can be produced by the native virus and also by different forms of viral CP lacking RNA. The SPs can be generated by thermal denaturation and structural remodeling of different helical plant viruses belonging to genera Tobamovirus, Hordeivirus and family Flexiviridae. The invention relates to the creation of functionally active compostions on the base of said SP-platforms for use in medicine, veterinary, virology, immunology and diagnostics.In accordance with this aspect of the present invention, several immunogenic compositions were obtained comprising SP platform and linked to the SP surface foreign full-size proteins, including green fluorescent protein, coat protein of PVX or epitopes of several different viruses (e.g. human influenza A virus and rubella virus epitopes). The procedure of in vitro assembly of said type of composition took about one hour. Apparently, the nanocomplexes of SNP/SMP with foreign antigens/epitopes could be regarded as candidate nanovaccines. In accordance with another aspect of the present invention, we found
