Humoral immune response characterization of heterologous prime-boost vaccination with CoronaVac and BNT162b2

Soluble SARS‐CoV‐2 RBD and human ACE2 peptidase domain produced in DrosophilaS2 cells show functions evoking virus–cell interface

“…Experimental datasets obtained with variable levels of immobilized shACE2‐ST gave an average K D = 8.29 ± 0.69 nM (Figure 3b; Supporting Information Table S3), consistent with proteins expressed in human (Liu et al, 2021) and insect cells (Lan et al, 2020). Additionally, we demonstrated that RBD‐ST binds full‐length cell‐associated hACE2 in a dose‐dependent way, as seen by flow cytometry (Figure 3c), and that RBD clv is specifically recognized by human sera from naturally infected individuals (Figure 3d) as seen before (Amanat et al, 2020; Rammauro et al, 2022). Finally, we demonstrate with competition ELISA that reactive serum samples can block the interaction between immobilized RBD clv and soluble shACE2‐ST, providing proof‐of‐concept for its usage in sVNTs developed in‐house (Figure 3e).…”

“…The effect of RBD deglycosylation on binding with serum antibodies was assessed by SPR analysis as before (Rammauro et al, 2022), capturing RBD‐ST and deg RBD‐ST at final densities of 46 and 52 RUs in two parallel surfaces and injecting 1:50 dilutions of sera from individuals who received a three doses heterologous vaccination scheme (two doses of CoronaVac + booster with BNT162b).…”

“…S2 stable cell lines expressing RBD-ST and shACE2-ST were obtained as described before (Rammauro et al, 2022) by co-transfection with the respective expression vector and pCoPuro selection plasmid using Effectene reagent (QIAGEN). Transfected cells were selected at 28 C in Insect Xpress medium (LONZA) added with 6 μg/ mL puromycin.…”

“…ELISA was done as previously described (Rammauro et al, 2022) using plates coated with 200 ng of RBD clv or RBD clv -IEX fractions and incubated with 1:100 dilutions of negative (pre-pandemic), positive (SARS-CoV-2 infection confirmed by PCR), or vaccinated (two doses of CoronaVac + booster with BNT162b) human sera. Competition ELISA was done with plates coated with variable amounts of RBD clv (0.0, 0.5, 1.0, and 2.0 micrograms per well) and incubated for 1 h at RT with a pre-mix of variable concentrations of shACE2-ST (0, 6, 12, and 24 μg/ mL) and human sera diluted 1:20 in PBS.…”

“…The rapid spread of SARS‐CoV‐2 in 2020 was followed by the fast development of effective vaccines, which were globally distributed, showing inequalities in access (Mathieu et al, 2021), concomitant with the emergence of multiple variants of concern (VOCs) with increased virulence, transmission, and immune escape (Mistry et al, 2022). In addition, different vaccine platforms have been shown to trigger a robust humoral immune response that wanes after a few months, motivating several countries to implement vaccine booster immunization that improves the response (Pascuale et al, 2022; Rammauro et al, 2022).…”