Antibody Profiling in COVID-19 Patients with Different Severities by Using Spike Variant Protein Microarrays

The
disease progression of COVID-19 varies from mild to severe,
even death. However, the link between COVID-19 severities and humoral
immune specificities is not clear. Here, we developed a multiplexed
spike variant protein microarray (SVPM) and utilized it for quantifying
neutralizing activity, drug screening, and profiling humoral immunity.
First, we demonstrated the competition between antispike antibody
and ACE2 on SVPM for measuring the neutralizing activity against multiple
spike variants. Next, we collected the serums from healthy subjects
and COVID-19 patients with different severities and profile the neutralizing
activity as well as antibody isotypes. We identified the inhibition
of ACE2 binding was stronger against multiple variants in severe compared
to mild/moderate or critical patients. Moreover, the serum IgG against
nonstructural protein 3 was elevated in severe but not in mild/moderate
and critical cases. Finally, we evaluated two ACE2 inhibitors, Ramipril
and Perindopril, and found the dose-dependent inhibition of ACE2 binding
to all the spike variants except for B.1.617.3. Together, the SVPM
and the assay procedures provide a tool for profiling neutralizing
antibodies, antibody isotypes, and reagent specificities.