Lab Matters Fall 2022 | Page 37

APHL 2022 POSTER ABSTRACTS
Results : The reportable range is 2-200 BAU / mL and with 1:50 dilution up to 10,000 BAU / mL . The clinical specificity of the VITROS IgG Quant assay for the 533 pre-pandemic healthy blood donors was 100.0 % ( 533 / 533 ) [ 95 % exact CI ( 99.3-100.0 %)]. The PPA with RT-PCR for 264 PCR positive individual ’ s samples collected 15 days or more from onset of symptoms was 92.4 % ( 244 / 264 ) [ exact 95 % CI ( 88.5-95.3 %)]. The observed total reproducibility for the 6 panel members ranged from 0.4 to 14.9 % CV . The assay demonstrated a quantitative increase in antibody titer throughout the course of vaccination and all vaccinated individuals demonstrated a result > 600 BAU / mL after the second vaccine dose . Antibody response to the vaccine doses was greater in individuals with evidence of previous infection , based on nucleocapsid antibody reactivity prior to the first dose . Evidence of antibody waning post vaccination was also observed in fully vaccinated individuals tested months after vaccination .
Conclusion : The VITROS Anti-SARS-CoV-2 IgG Quant assay * demonstrates excellent clinical and analytical performance and can detect quantitative antibody response to COVID-19 infection or vaccination .
* For EUA Only . Note , dilution and vaccine response not authorized by the FDA
Presenter : Paul Contestable , Ortho Clinical Diagnostics , paul . contestable @ orthoclinicaldiagnostics . com
After a second incubation at 37 ° C , 2 ml of overlay was added to each well . After 24 h incubation at 37 ° C , a second overlay containing neutral red was dispensed into each well and the number of plaques was counted 48 – 72 h after initial inoculation . The highest dilution of serum that inhibited plaque formation by 50 % ( PRNT50 ) was determined based upon the titer of the samples and the number of plaques present at each dilution . Samples with PRNT50 titers less than or equal to 1:20 are considered negative for nAbs . 25 samples were blind-tested with both the VITROS IgG Quant assay and the CSU PRNT , 20 known positive for SARS-CoV-2 antibody and 5 negatives . Correlation of the VITROS IgG Quant values to CSU PRNT50 was determined .
Results : The VITROS IgG Quant results ranged from < 2 to 1473 BAU / mL . The CSU PRNT50 results ranged from < 1:20 to 1:1280 . Pearson correlation coefficient was calculated to be 0.912 demonstrating a good correlation between the VITROS IgG Quant results and the CSU PRNT50 titers .
Conclusion : The VITROS Anti-SARS-CoV-2 IgG Quantitative assay demonstrates a strong correlation to PRNT50 for measurement of SARS-CoV-2 nAb titers .
* For EUA Only . Note , correlation to PRNT not authorized by the FDA
Presenter : Paul Contestable , Ortho Clinical Diagnostics , paul . contestable @ orthoclinicaldiagnostics . com
Correlation of the VITROS ® Anti-SARS-CoV-2 IgG Quantitative Assay * with SARS-CoV-2 Plaque Reduction Neutralization Test
B Hirsch 1 , P Contestable 1 , B Novick 1 , L Hartson 2 , I Ragan 2 , R Goodrich 2 , L Li 1 ; 1 Ortho Clinical Diagnostics , 2 Colorado State University
Background : This study was designed to assess the correlation of the VITROS Immunodiagnostic Products Anti-SARS-CoV-2 IgG Quantitative assay ( VITROS IgG Quant ) to a plaque reduction neutralization test developed at Colorado State University ( CSU PRNT ). The VITROS IgG Quant assay is for the quantitative detection of SARS-CoV-2 IgG antibodies with calibration traceable to the First WHO International Standard for Anti-SARS-CoV-2 antibody . Results are reported in both qualitative ( reactive / non-reactive ) and quantitative values ( Binding Antibody Units ( BAU )/ mL ). PRNT is considered the gold standard method for determining neutralizing antibody ( nAb ) titers .
Methods : VITROS IgG Quant : The VITROS IgG Quant assay is a fully automated , high throughput method run on the VITROS family of immunoassay analyzers . First , antibodies to SARS-CoV-2 present in the sample bind with S1 subunit of the spike protein coated on wells . After washing , HRP-labeled murine monoclonal antihuman IgG antibodies are added . Following a final wash , bound HRP conjugates are detected using the VITROS signal reagent . The amount of conjugate directly correlates to the amount of SARS- CoV-2 IgG antibody present and is reported in BAU / mL .
CSU PRNT : Samples were heat inactivated for 30 min at 56 ° C and serial two-fold dilutions were prepared in a 96-well plate . Viral stock ( strain hCoV-19 / USA / WA1 / 2020 ) containing ~ 200 pfu per 0.1 ml was added to each well containing serum dilutions . Following an incubation at 37 ° C in 5 % CO2 , 6-well plates containing recently confluent Vero cells were inoculated with the virus – serum mixtures .
SARS-CoV-2 Detection by the VITROS ® Immunodiagnostic Products SARS-CoV-2 Antigen Assay * is Unaffected by Mutated Variant Nucleocapsid Proteins
L Li , C Noeson , P Hosimer , B Hirsch , P Contestable and P Lunderg , Ortho Clinical Diagnostics
Background : Ortho Clinical Diagnostics continuously monitors emerging SARS-CoV-2 variants for their potential impact on the VITROS ® SARS-CoV-2 tests , including the VITROS Immunodiagnostic Products SARS-CoV-2 Antigen assay ( VITROS CV2Ag assay ) used to detect acute infection through the detection of SARS-CoV-2 nucleocapsid antigens . Monitoring comprises : 1 ) in silico analysis of variant proteins to evaluate for potential interference , 2 ) monitoring of customer false negative ( FN ) reports across the globe and 3 ) wet lab testing of recombinant mutant proteins and patient samples . Here , we focus on mutation monitoring in nucleocapsid and testing of recombinant nucleocapsid protein using the VITROS CV2Ag assay , with a particular emphasis on B . 1.1.28.1 ( Gamma ), B . 1.617.2 ( Delta ) and B . 1.1.529 ( Omicron ).
Methods : To date , seven specific mutations near the epitopes for the monoclonal antibodies used in the VITROS CV2Ag assay have been tested . Testing was performed at 15 pg / mL , which is 3X the level of detection ( LoD ; 5 pg / mL ) for the assay . Matching supplier wild-type ( Wuhan-Hu-1 nucleocapsid ) was used to normalize signals . Data are presented for select mutations and variants . At the time of the abstract submission , clinical nasopharyngeal samples from patients infected with SARS-CoV-2 Omicron were being procured and results will be shown and contrasted with data from non-Omicron samples .
Results : The VITROS CV2Ag assay uses recombinant wild-type Wuhan-Hu-1 ( WT ) nucleocapsid calibrators . Potentially interfering mutations from in silico analysis were ordered as recombinant proteins and tested using the WT nucleocapsid as control . In all instances , recombinant mutants were detected to the same extent ,
COVID-19
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