Virological and serological characterization of critically ill patients with COVID-19 in the UK: Interactions of viral load, antibody status and B.1.1.7 variant infection.
Ratcliff J., Nguyen D., Fish M., Rynne J., Jennings A., Williams S., Al-Beidh F., Bonsall D., Evans A., Golubchik T., Gordon AC., Lamikanra A., Tsang P., Ciccone NA., Leuscher U., Slack W., Laing E., Mouncey PR., Ziyenge S., Oliveira M., Ploeg R., Rowan KM., Shankar-Hari M., Roberts DJ., Menon DK., Estcourt L., Simmonds P., Harvala H.
BACKGROUND: Convalescent plasma containing neutralising antibody to SARS-CoV-2 is under investigation for COVID-19 treatment. We report diverse virological characteristics of UK intensive care patients enrolled in the Immunoglobulin Domain of the REMAP-CAP randomised controlled trial that potentially influence treatment outcomes. METHODS: SARS-CoV-2 RNA in nasopharyngeal swabs collected pre-treatment was quantified by PCR. Antibody status was determined by spike-protein ELISA. B.1.1.7 was differentiated from other SARS-CoV-2 strains using allele-specific probes or restriction site polymorphism (SfcI) targeting D1118H. RESULTS: Of 1274 subjects, 90% were PCR-positive with viral loads 118-1.7x10 11 IU/ml. Median viral loads were 40-fold higher in those seronegative for IgG antibodies (n=354; 28%) compared to seropositives (n=939; 72%). Frequencies of B.1.1.7 increased from <1% in early November, 2020 to 82% of subjects in January 2021. Seronegative individuals with wild-type SARS-CoV-2 had significantly higher viral loads than seropositives (medians 5.8x10 6 and 2.0 x10 5 IU/ml respectively; p=2x10 -15). However, viral load distributions were elevated in both seronegative and seropositive subjects infected with B.1.1.7 (4.0x10 6 and 1.6x10 6 IU/ml respectively). CONCLUSIONS: High viral loads in seropositive B.1.1.7-infected subjects and resistance to seroconversion indicate less effective clearance by innate and adaptive immune responses. SARS-CoV-2 strain, viral loads and antibody status define subgroups for analysis of treatment efficacy.