Session topic

15:40–15:45

Title: Establishment and validation of in-cell-ELISA-based assays for the rapid determination of antibodies neutralizing different viruses including Rabies virus, cytomegaloviruses, and SARS-CoV-2
ID: PS 59
Type: Poster session
Talk time: 3 + 2 min
Session: Poster session 2
Clinical virology I

Speaker: Lara Schöler (Essen/DE)


Abstract - Text

Abstract text (incl. references and figure legends)

Introduction:
Neutralizing antibodies (nAbs) prevent viral infection of permissive cells in the absence of immune cells or other mediators of the immune system. Constituting important correlates of protection, the determination of nAbs is indispensable for convalescent plasma selection, vaccine candidate evaluation, and the assessment of protective immunity.


Objectives:
In contrast to standard serological ELISAs, neutralization tests (NTs) are laborious, time-consuming, expensive, and restricted to specialized laboratories. To replace microscopic counting-based NTs by novel assays exempt from genetically modified viruses, which are inapplicable in most diagnostics departments, our aim was to establish nAb assays which can be automated and run on microplate readers.


Materials & methods: 
For this purpose, we established simple, rapid, and automated neutralization assays employing the in-cell ELISA (icELISA) approach for Rabies virus (RABV), cytomegaloviruses, and SARS-CoV-2.


Results:
After optimization of various parameters such as virus-specific antibodies, cell lines, virus doses, and duration of infection, virus-infected cells became amenable as direct antigen source for quantitative icELISA. Antiviral agents such as human sera containing nAbs or antiviral interferons dose-dependently reduced virus-specific signals.
The in-cell neutralization test (icNT) exhibited excellent intra- and inter-assay precision as well as excellent sensitivity and specificity. All seronegative and seropositive samples were diagnosed correctly. Applying increased infectious doses, the icNT was superior to NT in discriminating SARS-CoV-2 convalescent sera with high from those with intermediate neutralizing capacities.
In addition, the icNT was found to be specific, discriminating between SARS-CoV-2-specific nAbs and those raised against other coronaviruses. 
Using HA-tagged antigens, mouse, and human cytomegalovirus, we showed that the test principle is also applicable to quantify other viral antigens and nAb titers for other viruses.


Conclusions:
Altogether, the icELISA test allows rapid, automated quantification of virus infection in cell culture to evaluate the efficacy of nAbs and antiviral drugs using reagents and equipment present in most routine diagnostics departments.