Minor Displacements in the Insertion Site Provoke Major Differences in the Induction of Antibody Responses by Chimeric Parvovirus-like Particles

Abstract

An antigen-delivery system based on hybrid virus-like particles (VLPs) formed by the self-assembly of the capsid VP2 protein of canine parvovirus (CPV) and expressing foreign peptides was investigated. In this report, we have studied the effects of inserting the poliovirus C3:B epitope in the four loops and the C terminus of the CPV VP2 on the particle structure and immunogenicity. Epitope insertions in the four loops allowed the recovery of capsids in all of the mutants. However, only insertions of the C3:B epitope in VP2 residue 225 of the loop 2 were able to elicit a significant anti-peptide antibody response, but not poliovirus-neutralizing antibodies, probably because residue 225 is located in an small depression of the surface. To fine modulate the insertion site in loop 2, a cassette-mutagenesis was carried out to insert the epitope in adjacent positions 226, 227, and 228. The epitope C3:B inserted into these positions was well recognized by the specific monoclonal antibody C3 by immunoelectron microscopy. BALB/c mice immunized with these chimeric C3:B CPV:VLPs were able to elicit an strong neutralizing antibody response (>3 log(10) units) against poliovirus type 1 (Mahoney strain). Therefore, minor displacements in the insertion place cause dramatic changes in the accessibility of the epitope and the induction of antibody responses.

Identification of Immunogenic Hot Spots within Plum Pox Potyvirus Capsid Protein for Efficient Antigen Presentation

“…It is therefore not surprising that displacements of only 1 or 2 aa in the insertion sites could cause the shift from the null immunogenicity of foreign sequences cloned in the ␥ site to the efficient induction of antibodies of sequences cloned in any of the g sites (Table 1). A precedent of minor displacements in the insertion site causing drastic changes in the immunogenicity of the inserted sequences has been previously reported for epitope expression on the surface of chimeric parvovirus (35) and cowpea mosaic virus (39) particles. These results illustrate the utility of structure and immunogenicity predictions and fine-tuning experimental approaches in the development of antigen presentation systems based on virion capsids.…”

Thermal Stability of RNA Phage Virus-Like Particles Displaying Foreign Peptides

“…Enlarging the loop obviously disrupts the turn's structure and replaces it with a large, presumably flexible segment, thus reducing protein stability. Although a number of studies have noted the reduced yields of viruses or VLPs displaying foreign peptides [11-14], we are aware of only one other reporting the effects of loop insertions on virus-like particle stability: Carreira et. al.…”

Novel chimeric virus-like particles vaccine displaying MERS-CoV receptor-binding domain induce specific humoral and cellular immune response in mice

“…Moreover, canine parvovirus (CPV) does not cause disease in human, therefore parvovirus-like particles is a safe expression platform. Parvovirus VLP has been successfully used for the expression of foreign antigens and induction of robust B-, Tcell responses (Miyamura et al, 1994;Casal et al, 1999;Lo-Man et al, 1998;Xu et al, 2014;Rueda et al, 1999).…”