Different Neutralization Sensitivity of SARS-CoV-2 Cell-to-Cell and Cell-Free Modes of Infection to Convalescent Sera

Abstract

The COVID-19 pandemic caused by SARS-CoV-2 has posed a global threat to human lives and economics. One of the best ways to determine protection against the infection is to quantify the neutralizing activity of serum antibodies. Multiple assays have been developed to validate SARS-CoV-2 neutralization; most of them utilized lentiviral or vesicular stomatitis virus-based particles pseudotyped with the spike (S) protein, making them safe and acceptable to work with in many labs. However, these systems are only capable of measuring infection with purified particles. This study has developed a pseudoviral assay with replication-dependent reporter vectors that can accurately quantify the level of infection directly from the virus producing cell to the permissive target cell. Comparative analysis of cell-free and cell-to-cell infection revealed that the neutralizing activity of convalescent sera was more than tenfold lower in cell cocultures than in the cell-free mode of infection. As the pseudoviral system could not properly model the mechanisms of SARS-CoV-2 transmission, similar experiments were performed with replication-competent coronavirus, which detected nearly complete SARS-CoV-2 cell-to-cell infection resistance to neutralization by convalescent sera. These findings suggest that the cell-to-cell mode of SARS-CoV-2 transmission, for which the mechanisms are largely unknown, could be of great importance for treatment and prevention of COVID-19.

Protective activity of mRNA vaccines against ancestral and variant SARS-CoV-2 strains

“…Nonetheless, mutations in the B.1.617.2 alter key antigenic sites and can abrogate recognition by neutralizing antibodies ( 26 ). Other possible explanations for the loss of potency of antibodies against B.1.617.2 include differential display of B.1.617.2 spike proteins on the surface of infected cells and engagement of Fc effector functions ( 27 , 28 ) or differential ability of antibodies to block cell-to-cell spread in a strain-dependent manner ( 29 ). Our observation of B.1.617.2 infection and lung disease in low-dose mRNA-vaccinated K18-hACE2 mice corresponds to descriptions of B.1.617.2 breakthrough infections in vaccinated humans, some of which have required hospitalization ( 30 , 31 ).…”

High Individual Heterogeneity of Neutralizing Activities against the Original Strain and Nine Different Variants of SARS-CoV-2

“…This technique performed with replication-competent coronaviruses seems to have an epidemiological potential to detect the presence or absence of neutralising antibodies against the newly emerging SARS-CoV-2 variants. This technique is clearly superior to pseudoviral systems that do not reflect a real viral infection since they only mimic the entry step of the virus' life cycle and have serious limitations related to the usage of unnatural core proteins [14]. We managed to obtain convalescent plasma samples from 42 patients at least 3 weeks after a documented SARS-CoV-2 infection.…”

Snake venom phospholipase A2s exhibit strong virucidal activity against SARS-CoV-2 and inhibit the viral spike glycoprotein interaction with ACE2

“…Vero E6 (ATCC CRL-1586), 293T (ATCC CRL-3216) and 293T/ACE2 (obtained as described [34]) cells were grown in complete DMEM medium (Gibco, Thermo Fisher Scientific, Waltham, MA, USA), supplemented with 10% fetal bovine serum (FBS; HyClone, Cytiva, Marlborough, MA, USA), 1 × L-Glutamine (PanEco, Moscow, Russia) and 1 × penicillin-streptomycin (PanEco, Russia). All cell lines tested negative for mycoplasma contamination.…”