ABSTRACT
The antigenicity of SARS-CoV-2 is a critical issue for the effectiveness of the vaccine, and thus it should be phenotypically evaluated by serological assays as new field isolates emerge. The hemagglutination/hemagglutination-inhibition (HA/HI) tests are well-known as a representative method for antigenic analysis of influenza viruses, but SARS-CoV-2 is unlikely to agglutinate to human or guinea pig red blood cells. Therefore, the antigenic analysis requires complicated enzyme-linked immunosorbent assay (ELISA) or cell-based assays such as the microneutralization assay. In this study, we developed the particle agglutination/particle agglutination-inhibition (PA/PAI) test to easily and rapidly quantify the virus and antibody using human angiotensin-converting enzyme 2 (hACE2)-bound latex beads. The PA titer was positively correlated with the plaque-forming units. The PAI titer using post-infection Syrian hamster antisera clearly revealed the antigenic difference between the omicron and previous variants. The results show the PAI test is useful for easy and rapid antigenic analysis of SARS-CoV-2.
ABSTRACT
The Diamond Princess (DP) cruise ship was put under quarantine offshore Yokohama, Japan, after a passenger who disembarked in Hong Kong was confirmed as a COVID-19 case. We performed whole genome sequencing of SARS-CoV-2 directly from PCR-positive clinical specimens and conducted a haplotype network analysis of the outbreak. All tested isolates exhibited a transversion at G11083T, suggesting that SARS-CoV-2 dissemination on the DP originated from a single introduction event before the quarantine started. Although further spreading might have been prevented by quarantine, some progeny clusters were linked to transmission through mass-gathering events in the recreational areas and direct transmission among passengers who shared cabins during the quarantine. This study demonstrates the usefulness of haplotype network analysis in identifying potential infection routes.