Arch Virol (2002) 147: 119–130
Baculovirus expression and antigenic characterization
of the capsid proteins of three Norwalk-like viruses
, W. M. Zhong
, T. Farkas
, P. W. Huang
, N. Wilton
, E. Barrett
, R. Morrow
, and D. O. Matson
Center for Pediatric Research, Children’s Hospital of The King’s Daughters,
Eastern Virginia Medical School, Norfolk, Virginia, U.S.A.
Virginia Department of Health, Richmond, Virginia, U.S.A.
Navy Environmental Health Center, Norfolk, Virginia, U.S.A.
Children’s Hospital Medical Center, Cincinnati, Ohio, U.S.A.
Accepted July 20, 2001
Summary. Human caliciviruses (HuCVs) are antigenically diverse. The anti-
genic relationships among different HuCVs have been difﬁcult to study because
HuCVs cannot be passaged in the laboratory. In this study, we describe cloning,
sequencing and expression of the viral capsid proteins of three HuCVs that were
identiﬁed in outbreaks of acute gastroenteritis in Virginia in 1997–1998. Yields
of the capsid proteins similar to previously expressed recombinant Norwalk virus
were obtained using the baculovirus expression system. Recombinant VA97207
capsid protein (rVA97207) and rVA98387, but not rVA98115, formed virus-like
particles (VLPs). All three recombinant capsid antigens detected seroresponses in
patients involved in outbreaks of acute gastroenteritis associated with genetically
homologous or related HuCVs. The antigenic relationships of the three strains
were further characterized using hyperimmune antisera against the three capsid
antigens as well as four previously characterized recombinant capsid antigens of
Norwalk (rNV), Mexico (rMxV), Hawaii (rHV), and Grimsby viruses (rGrV).
VA98387 shared 98% aa identity with GrV; rVA98387 was detected by antisera
to GrV. VA98115 shared 87% aa identity with Desert Storm virus and 65% aa
identity with prototype Norwalk virus (NV); rVA98115 reacted weakly with NV
antisera. VA97207 shared 80% aa identity with Amsterdam and 75% aa identity
with Leeds strains and rVA97207 was not detected by any of the heterologous
antibodies. In conclusion, VA97207 and VA98115 may belong to CV antigenic
types not previously expressed, while VA98387 is a GrV-like virus. Low levels
of cross-reactive antibodies were detected between types. Further studies to char-
acterize these antigens and to develop enzyme immune assays (EIAs) for these
strains are in progress.