Self-Assembly of the Recombinant Capsid Protein of a Swine Norovirus into Virus-Like Particles and Evaluation of Monoclonal Antibodies Cross-Reactive with a Human Strain from Genogroup II

Abstract

Noroviruses (NoVs) are responsible for the majority of gastroenteritis outbreaks in humans. Recently, NoV strains which are genetically closely related to human genogroup II (GII) NoVs have been detected in fecal specimens from swine. These findings have raised concern about the possible role of pigs as reservoirs for NoVs that could infect humans. To better understand the epidemiology of swine NoVs in both the swine and the human populations, rapid immunoassays are needed. In this study, baculovirus recombinants were generated to express the capsid gene of a swine NoV GII genotype 11 (GII.11) strain which self-assembled into virus-like particles (VLPs). Subsequently, the purified VLPs were used to evoke monoclonal antibodies (MAbs) in mice. A panel of eight promising MAbs was obtained and evaluated for their ability to bind to heterologous VLPs, denaturated antigens, and truncated capsid proteins. The MAbs could be classified into two groups: two MAbs that recognized linear epitopes located at the amino-terminal half (shell domain) of the swine NoV GII.11 VLPs and that cross-reacted with human GII.4 NoV VLPs. The other six MAbs bound to conformational epitopes and did not cross-react with the human GII.4 VLPs. To our knowledge, this is the first report on the characterization of MAbs against swine NoVs. The swine NoV VLPs and the MAbs described here may be further used for the design of diagnostic reagents that could help increase our knowledge of the prevalence of NoV infections in pigs and the possible role of pigs as reservoirs for NoVs.

Rabbit hemorrhagic disease virus capsid, a versatile platform for foreign B-cell epitope display inducing protective humoral immune responses

“…Baculoviruses were propagated in Trichoplusia ni High five cells (H5) grown in monolayer cultures at 28 °C in TNM-FH medium (Sigma-Aldrich), supplemented with 5% fetal calf serum (Gibco)60. Feline calicivirus (FCV), Urbana strain, kindly provided by K.Y.…”

Epitope Insertion at the N-Terminal Molecular Switch of the Rabbit Hemorrhagic Disease Virus T=3 Capsid Protein Leads to Larger T=4 Capsids

“…Our structural studies constitute a framework for the design of RHDV recombinant capsids as a delivery system for B and T cell epitopes (1,12), as high-resolution structures of viruses in the genus Lagovirus currently are not available. In addition to defining RHDV particle structure, our studies contribute to establishing the determinants of its assembly process.…”

Multiple Antigenic Sites Are Involved in Blocking the Interaction of GII.4 Norovirus Capsid with ABH Histo-Blood Group Antigens

“…Several cross-reactive MAbs have been described for noroviruses, and epitopes for most of them have been mapped within the most conserved regions of the norovirus capsid protein (C-terminal P or S domain). As suggested previously, cross-reactive MAbs could potentially be used in diagnostic assays (3,24,36,46,51); however, Oliver et al (45) described a cross-reactive MAb that recognized a linear epitope in the S domain of the VLPs from bovine noroviruses that did not detect native virions in fecal samples from experimental animals. They proposed that because the S domain forms the innermost domain of the capsid, the epitope is not accessible in native virions.…”

“…Several cross-reactive MAbs have been identified, and most of them have been mapped to the S domain or the C-terminal region of the P1 domain (3,4,35,45,46,51,65,66). It has been reported that certain MAbs block the interaction of VLPs with cells or synthetic HBGA (38,43), and two HBGA-blocking sites were recently mapped (11,37).…”

“…Because VLPs are antigenically similar to native virions (28), efforts have been made to characterize the binding of monoclonal antibodies (MAbs) developed after immunization of mice with VLPs from various norovirus genotypes (3,25,66,67). Several cross-reactive MAbs have been identified, and most of them have been mapped to the S domain or the C-terminal region of the P1 domain (3,4,35,45,46,51,65,66).…”