Self-assembled B19 parvovirus capsids, produced in a baculovirus system, are antigenically and immunogenically similar to native virions.

Abstract

B19 parvovirus is pathogenic in humans, causing fifth disease, transient aplastic crisis, some cases of hydrops fetalis, and acquired pure red cell aplasia. Efforts to develop serologic assays and vaccine development have been hampered by the virus's extreme tropism for human bone marrow and the absence of a convenient culture system. We constructed recombinants containing either the major (VP2) or minor (VP1) structural proteins of B19 in a baculovirus-based plasmid, from which the polyhedrin gene had been deleted; these recombinant plasmids were used to generate recombinant infectious baculovirus. Subsequent infection of insect cells in vitro resulted in high-level expression ofeither B19 VP1 or VP2. Parvovirus capsids were obtained by self-assembly in cell cultures coinfected with either VP1-and VP2-containing baculoviruses or, surprisingly, VP2-containing baculoviruses alone. Empty B19 capsids composed of VP1 and VP2 could replace serum virus as a source of antigen in a conventional inmmunoassay for detection ofeither IgG or IgM antiparvovirus antibodies in human serum. Immunization of rabbits with capsids composed of VP1 and VP2 resulted in production of antisera that recognized serum parvovirus on immunoblot and neutralized parvovirus infectivity for human erythroid progenitor cells. Baculovirus-derived parvovirus antigen can substitute for scarce viral antigen in immunoassays and should be suitable as a human vaccine.B19 parvovirus is the only member ofthe family Parvoviridae pathogenic in humans (1, 2). Acute infection results in fifth disease, a common childhood exanthem that in adults more usually manifests as an arthralgia/arthritis syndrome. In persons with underlying hemolysis, acute infection produces transient aplastic crisis, precipitous anemia due to hypoproliferative erythropoiesis. B19 infection can be persistent (3). In the setting of immunodeficiency, due to congenital, acquired, or iatrogenic immunodeficiency, persistent parvovirus results in chronic pure red cell aplasia. In utero infection causes hydrops fetalis, with fetal death due to severe anemia and congestive heart failure (4).Clinical studies of B19 parvovirus infection have been hampered by limited supplies of viral antigen. The virus has extraordinary tropism for human erythroid progenitor cells and has only been propagated in explanted human bone marrow (5-8), fetal liver (9), and (to a lesser degree) erythroleukemia cells (10). We describe here expression of the virus's structural proteins in a baculovirus system. Large quantities of empty viral capsids were produced, which can substitute for serum virus in clinical assays and stimulate the production of neutralizing antibodies in animals. Only the major protein was required for capsid assembly; the minor capsid protein serves an important role in virus function independent of virion assembly. MATERIALS AND METHODSCell Culture and Virus Stocks. Autographa californica nuclear polyhedrosis virus (AcMNPV) and recombinant viruses were grown in monolayers of Sf9 cells. Sf9 c...

Canine parvovirus empty capsids produced by expression in a baculovirus vector: use in analysis of viral properties and immunization of dogs

“…This is also suggested by the crystallographic structure of CPV, which indicates that the resolved polypeptide involved in the assembly of the capsid is the region after residue 38 in the VP-2 molecule, and the N-terminal regions of the VP-2 protein (or VP-1) are not resolved (Tsao et al, 1991). The structural proteins of several other viruses, including the human parvovirus B19, have been shown to selfassemble into virus-like structures when expressed by baculovirus vectors in insect cells (Brown et al, 1990;French et al, 1990;Roosien et al, 1990;Luo et al, 1990;Kajigaya et al, 1991).…”

“…Other vaccines have included use of live feline panleukopenia virus (FPV) , or expression of the complete CPV VP-1 and VP-2 genes from a bovine papillomavirus vector (Mazzara et al, 1987). Expression of the human parvovirus B19 VP-1 and/or VP-2 genes from recombinant baculoviruses gives rise to virus particles with many of the properties of authentic B19 particles (Brown et al, 1990;Kajigaya et al, 1991).…”

Efficient assembly and release of SARS coronavirus‐like particles by a heterologous expression system

“…In our study, the expression of the S protein was very high and the incorporation of S glycoprotein onto the surface of the VLPs makes these particles not only a powerful instrument for studies of the assembly and budding of SARS-CoV particles but also as a candidate vaccine and a tool for SARS diagnosis. Self-assembly of viral capsid proteins into VLPs for both RNA and DNA viruses has been reported and VLPs produced by this system usually retain the immunogenic and physiochemical properties of the native virions [27][28][29][30][31][32].…”

Detection of human parvovirus B19 in a patient with hepatitis

“…Serum samples from all patients were analyzed for IgM-specific antibodies specific for B19 as previously described by Erdman et al (18), using as antigen the B19 capsid protein expressed in baculovirus (19).…”