The production of human parvovirus capsid proteins in Escherichia coli and their potential as diagnostic antigens

Abstract

We have expressed a number of polypeptides derived from the capsid proteins of the human parvovirus B 19 in Escherichia coli. These include native VP1 (8410 and VP2 (58K) proteins and also fusions to flo galactosidase containing differing amounts of the amino terminus of the VP1/2 polypeptide. Although each of these was expressed at high levels and the majority were produced as full-length proteins, only one was soluble. This soluble polypeptide, p132, is a/3-galactosidase fusion protein that includes 145 amino acids from B19 which are entirely derived from the region unique to VP1. Despite containing such a small portion of VP1, which itself constitutes only 4% of total capsid protein, p132 reacted with all our known anti-B19 IgM-positive human serum samples. We conclude that this region contains epitopes which must be prominently exposed on the intact virus. We have demonstrated the use of this recombinant antigen in a simple diagnostic assay for B19-specific antibodies which can be used for initial screening of human serum samples. In a survey of 103 serum specimens, our ELISA positively identified all samples (19/19) which were positive by IgM antibody capture radioimmunoassay. The recombinant p132 antigen is efficiently produced and readily purified from E. coli, and its use as a diagnostic antigen should increase the availability of routine clinical testing for human parvovirus infection.

Serodiagnosis of Human Bocavirus Infection

“…This was surprising in comparison with the other human-pathogenic parvovirus, B19, in which the VP1u is very immunoreactive [30] and contains many neutralizing epitopes [31][32][33][34][35]. Indeed, both VP2 and the VP1u region have been successfully used in the diagnosis of B19 infections [30,[36][37][38]. One possible reason for the dissimilarity between the 2 viruses might be a difference in the location of VP1u within the capsid [34,39,40], which could affect its accessibility to host immunity.…”

Unique region of the minor capsid protein of human parvovirus B19 is exposed on the virion surface.

“…Symmetry considerations (7) and the assumption that the basic residues on VPl help stabilize the viral DNA led to the prediction that VPl folds inside the viral capsid, and only the amino terminus of VP2 would enter the cylinders. We (17), and later others (18), have demonstrated that specific reactivity to the VPl unique region develops during natural infection and that VP1 is the dominant species recognized by convalescent human serum (17 parvoviruses have been mapped to regions ofVP2 (20), making this a more likely area for receptor binding in these structurally similar viruses. Either as a membrane contact region or receptor ligand, VP I would be expected to be an efficient target for neutralizing antibody.…”

Human Parvovirus B19: Molecular Virology, Clinical Features, Prevalence, Diagnosis and Control

“…Moreover, its incorporation into serological assays was thought essential (Rayment et al, 1990). However, it is now clear that this observation, which was based on the absence of antibodies to linear epitopes within the VP2 protein, when screened by Western blot, is erroneous.…”