Baculovirus expression of parvovirus B19 (B19V) NS1: utility in confirming recent infection

Abstract

Background: The presence of anti-parvovirus B19 (B19V) IgM against viral capsid proteins (VP1 and VP2) has long been used to detect recent infection. The utility of antibodies directed against B19V NS1 protein has received less attention as a serological indicator of recent infection, although anti-B19V NS1 IgG has been associated with persistent infection. Objecti6es: To elucidate the role of anti-B19V NS1 antibody detection in recent infection, full-length B19V NS1 was expressed and purified. The resultant antigen was used to develop both Western blot assays and microplate ELISA for the detection of NS1 antibodies. Study design: Serum specimens were obtained from individuals recently infected with B19V (children (n= 16), adults (n=40)) and from 17 individuals with no evidence of recent B19V infection. All specimens were screened for anti-B19V NS1 IgG and IgM. Results: It was observed that 68.8% (11/16) of children recently infected with B19V were anti-B19V NS1 IgG seropositive. Furthermore, 27.5% (11/40) anti-B19V VP2 IgM positive specimens also contained anti-B19V NS1 IgM when tested by ELISA, while no reactivity was observed following Western blot analysis, possibly due to the absence of conformational epitopes. Conclusions: Anti-B19V NS1 IgM detection may have utility in the confirmation of recent infection with B19V.

Leucine aminopeptidase of the human blood flukes, Schistosoma mansoni and Schistosoma japonicum

“…Production and purification of recombinant S. mansoni LAP in baculovirus expression vector system Spodoptera frugiperda (Sf 9 ) insect cells (Invitrogen) were transformed with pBlueBac4.5 plasmid construct incorporating the S. mansoni LAP cDNA as previously described (Ennis et al, 2001). Cell suspensions were lysed in the presence of 0.05% (v/v) Tween w 20 (Sigma) detergent in 50 mM NaH 2 PO 4 , 300 mM NaCl, and 10 mM imidazole (pH 8.0, lysis buffer), and then incubated on ice for 30 min.…”

B Cell Memory Is Directed toward Conformational Epitopes of Parvovirus B19 Capsid Proteins and the Unique Region of VP1

“…B19 recombinant proteins VP1, VP2, and NS1 were produced in, and purified from, Spodoptera frugiperda (Sf9) insect cells infected with recombinant baculovirus encoding either VP1, VP2, or NS1 open-reading frames, as described elsewhere [10,[14][15][16].…”

“…In fact, specific IgG against linear epitopes of VP2 disappears within 6-12 months after infection [8]. More dramatically, there is a near-total diminution of NS1-specific IgG in previously infected individuals [10]. It is, therefore, firmly established that detection of B19-specific IgG against conformational epitopes is currently the most reliable method for the detection of previous infection with, and probable immunity to, B19.…”

Establishment of functional B cell memory against parvovirus B19 capsid proteins may be associated with resolution of persistent infection

“…Although initially thought to be a marker of persistent infection only [von Poblotzki et al, 1995], the detection of NS1 IgG has also been shown to be present during acute B19 infection in 61%-69% of individuals [Hemauer et al, 2000;Ennis et al, 2001]. Moreover, significant T cell responses to NS1 have also been reported in recently infected individuals and patients who developed chronic arthropathy following B19 infection [Mitchell et al, 2001].…”