Precise location of linear epitopes on the capsid surface of feline calicivirus recognized by neutralizing and non-neutralizing monoclonal antibodies

Abstract

We report the generation, characterization and epitope mapping of a panel of 26 monoclonal antibodies (MAbs) against the VP1 capsid protein of feline calicivirus (FCV). Two close but distinct linear epitopes were identified at the capsid outermost surface (P2 subdomain) of VP1, within the E5′HVR antigenic hypervariable region: one spanning amino acids 431-435 (PAGDY), highly conserved and recognized by non-neutralizing MAbs; and a second epitope spanning amino acids 445-451 (ITTANQY), highly variable and recognized by neutralizing MAbs. These antibodies might be valuable for diagnostic applications, as well as for further research in different aspects of the biology of FCV.

Chimeric RHDV Virus-Like Particles Displaying Foot-and-Mouth Disease Virus Epitopes Elicit Neutralizing Antibodies and Confer Partial Protection in Pigs

“…We have developed a system for the generation of VLPs derived from different caliciviruses, such as swine norovirus [ 42 ], feline calicivirus [ 43 ] and RHDV [ 25 ]. Our previous results have shown that RHDV VLPs can be produced to high yields, are highly immunogenic and are suitable to be used as diagnostic reagents or vaccines for the control of RHDV in rabbits [ 24 , 41 , 44 ].…”

Immunogenicity of Multi-Target Chimeric RHDV Virus-Like Particles Delivering Foreign B-Cell Epitopes

“…The B-cell epitopes: FCV22 (GSGNDITTANQYDAADIIRN), derived from FCV capsid protein [27], and 2L21 (SDGAVQPDGGQPAVRNERATGS), derived from CPV VP2 protein [29], were prepared as synthetic peptides by solid phase synthesis and HPLC purification (D. Andreu, Pompeu Fabra University, Barcelona, Spain), and were used in ELISA assays to detect specific antibody titers.…”

“…For Western blot analyses, proteins were transferred from gels onto polyvinylidene difluoride (PVDF) membranes using Trans-Blot ®® Turbo™ Transfer System (Bio-Rad Laboratories, Hercules, CA, USA). Membranes were saturated (overnight, 4 • C) with PBS, 5% (wt/vol) skim milk, and 0.5% (vol/vol) Tween 20 and incubated (1 h, 37 • C) with either a rabbit hyperimmune serum against RHDV to detect VP60 protein, 51D10 monoclonal antibody recognizing FCV22 epitope [27], or 3C9 monoclonal antibody against 2L21 epitope [28]. After several washes with PBS-0.05% Tween 20, membranes were incubated (1 h, 37 • C) with HRP-conjugated goat anti-rabbit IgG (Thermo Fisher Scientific, Waltham, MA, USA) or HRP-conjugated goat anti-mouse IgG (Invitrogen, Carlsbad, CA, USA).…”

“…Two control samples (serial dilutions) were added to each plate: a monoclonal antibody specific against the target antigen (2E7 for RHDV VP60 protein [24], 51D10 for FCV22 epitope [27], or 3C9 for 2L21 epitope [29]) and a pre-immune serum lacking target antigenspecific antibodies.…”

“…Our aim was to evaluate if chimeric RHDV VLPs harbouring two different B-cell epitopes would be able to induce strong humoral responses against both of them, or if immune interference between the target epitopes incorporated could exert a detrimental effect in the foreign antigen-specific immune responses elicited by such bivalent vaccines. We used two model epitopes: a newly described neutralizing B-cell epitope derived from the feline calicivirus (FCV) capsid protein (epitope FCV22) [12,27] and a well characterized B-cell epitope derived from the VP2 capsid protein of canine parvovirus (CPV, epitope 2L21) [28,29]. This epitope is located at the N-terminal end of VP2 and it is well conserved across different related parvoviruses such as feline panleukopenia virus (FPV), mink enteritis virus (MEV), raccoon parvovirus (RPV), and minute virus of mice (MVM) [29,30].…”