The seroepidemiology of genogroup 1 and genogroup 2 Norwalk-like viruses in Italy

Abstract

Southampton virus (SV) and Lordsdale viruses (LV) are small round structured viruses characterised recently and belong to two separate genogroups. The capsid genes of these viruses were expressed in insect cells using recombinant baculoviruses. Both SV (genogroup 1) and LV (genogroup 2) capsid proteins self-assembled to form virus-like particles (VLPs). The VLPs were used in a standard enzyme-linked immunosorbent assay (ELISA) to screen for antibodies to SV and LV in 1,729 age-stratified human sera collected in Verona, Italy between January and November 1996. SV VLPs were labile compared with LV VLPs. There was a large difference in the prevalence of SV (28.7%) compared with LV (91.2%). However, presentation of SV VLPs using chicken egg yolk antibody-coated wells (IgY capture ELISA) with a subset of serum samples from patients (0-19 years) increased the number of positive sera significantly (50.5%), indicating that SV antigen integrity is an important factor in the assay. Recent reverse transcription-polymerase chain reaction (RT-PCR) studies have shown that LV is circulating currently and analysis of IgY capture ELISA data showed greater reactivity for LV than SV, reflecting a genuinely lower rate of recent infection by this genogroup 1 virus.

Molecular Cloning, Expression, Self-Assembly, Antigenicity, and Seroepidemiology of a Genogroup II Norovirus Isolated in France

“…1A) as already reported (2,18,21). The 55-kDa protein might represent a possible cleavage product of the expressed protein as previously suggested (2,21).…”

“…The capsid protein obtained self-assembled spontaneously into virus-like particles (VLPs) which are morphologically and antigenically similar to the native particles. VLPs have been subsequently prepared for different strains, notably Southampton genotype I (18), Hawaii genotype II (10), Mexico genotype II (14), Toronto GII (16), and Lordsdale genotype II (6). Because noroviruses are difficult to propagate, these VLPs represent an important source of antigen that can be used in place of the native virus to study seroprevalence and to better understand immunity to caliciviruses.…”

“…1B). Such a protein has been shown to be a C-terminal cleavage product of the capsid protein (12,15) and has been reported to be mainly cell associated (15,18) (22). Such proteins have been shown also to be C-terminal fragments of the capsid protein.…”

Studies of Epidemiology and Seroprevalence of Bovine Noroviruses in Germany

“…The crude VLPs were pelleted by centrifugation for 2 h at 100,000 ϫ g using a Beckman SW28 rotor, resuspended in CsCl at 1.362 g/cm 3 , and centrifuged for 24 h at 120,000 ϫ g in a Beckman SW50.1 rotor to reach equilibrium. The CsCl was removed from gradient fractions containing VLPs by dialysis with 10 mM Tris-HCl-150 mM NaCl (pH 7.5) (27). The purified VLPs were stored in aliquots at Ϫ135°C.…”

Norovirus GII.4 antibodies in the Portuguese population

“…Since no information on the genetic characterization of norovirus infections in Portugal was available, we selected GII.4 New Orleans antigen as this GII.4 variant emerged in 2009 and continued to cause outbreaks in 2012 [13]. Compared to data from other countries, such as France which reported a prevalence of 74.1% [14]; Italy, 91.2% [15]; and the UK, 99.5% [8], the 70% we found in the Portuguese samples was relatively low. This variance could reflect real differences in exposure levels of norovirus in different European countries, or may be the result of the fact that the VLPs used in our study were unable to detect cross-reactive antibodies against non-GII.4 norovirus strains including GI [16].…”