Quantification of SARS-CoV-2 neutralizing antibody by wild-type plaque reduction neutralization, microneutralization and pseudotyped virus neutralization assays.

Virus neutralization assays measure neutralizing antibodies in serum and plasma, and the plaque reduction neutralization test (PRNT) is considered the gold standard for measuring levels of these antibodies for many viral diseases. We have developed procedures for the standard PRNT, microneutralization assay (MNA) and pseudotyped virus neutralization assay (PNA) for severe acute respiratory syndrome coronavirus 2. The MNA offers advantages over the PRNT by reducing assay time, allowing increased throughput and reducing operator workload while remaining dependent upon the use of wild-type virus. This ensures that all severe acute respiratory syndrome coronavirus 2 antigens are present, but Biosafety Level 3 facilities are required. In addition to the advantages of MNA, PNA can be performed with lower biocontainment (Biosafety Level 2 facilities) and allows for further increases in throughput. For each new vaccine, it is critical to ensure good correlation of the neutralizing activity measured using PNA against the PRNT or MNA. These assays have been used in the development and licensure of the ChAdOx1 nCoV-19 (AstraZeneca; Oxford University) and Ad26.COV2.S (Janssen) coronavirus disease 2019 vaccines and are critical for demonstrating bioequivalence of future vaccines.

An unusual outbreak of rotavirus genotype G2P[6] during the 2005-2006 epidemic season in Philadelphia.

Most rotavirus gastroenteritis is caused by G1P[8] strains. When G2 infections are encountered, the P type has most often been reported to be P[4]. The purpose of our study was to describe an unusual outbreak of G2P[6] cases. Children presenting to The Children's Hospital of Philadelphia with acute gastroenteritis have been monitored for rotavirus antigen in stool by ELISA (with G-typing if ELISA positive) since 1994-1995. Compared to the last 12 rotavirus seasons before the 2006 introduction of a new rotavirus vaccine, the 2005-2006 season had by far the highest number of evaluable rotavirus infections [n = 275 from September 2005 through June 2006, of which 261 (95%) were G typed] and the greatest number of G2 cases (n = 101, 39% of typed strains). Only 16% of G2 strains were associated with P[4], whereas genotype G2P[6] was responsible for 83% of the G2 infections. Eighty-eight percent of the 84 G2P[6] cases occurred in the 60% of patients who were African-Americans, most of whom were urban residents. Among 157 African-American patients, G2 cases (n = 80; 52%) predominated, including 74 due to G2P[6]. Children <6 months old accounted for 27% of cases overall, but 36% of the G2P[6] cases. G2 rotaviruses caused over a third of the community-acquired rotavirus cases in children presenting to CHOP in 2005-2006, attesting to the potential impact of G2 strains during some epidemics. The large majority of G2 strains had the rare P[6] genotype. Urban African-American children under 6 months of age were disproportionately affected.