Leading The Way: Using Advanced Assays to Fight SARS-CoV-2

The outbreak of the SARS-CoV-2 virus caused a sudden shift in focus for the biopharmaceutical industry. After the genetic sequence of the virus was released in early 2020, vaccine manufacturers across the globe began the race to research and develop vaccines to combat the virus.


As the world learned more about SARS-CoV-2, it proved to be both highly transmissible and virulent, requiring a BSL-3 facility necessary to handle the live virus. In order to avoid the development delays that would occur due to a limited number of qualified BSL-3 facilities, Nexelis pivoted their approach to solve the problem before it could even start.


Constructing A Robust Assay: How Nexelis Stayed At The Forefront Of COVID-19


Anticipating industry demand, Nexelis quickly switched to a VSVΔG-luciferase format to produce the pseudotyped virus for SARS-CoV-2 for a pseudoneutralization assay (PNA) from the previous low yielding microneutralization assay (MNA) that relies on the wild-type virus. The Protein Sciences Team at Nexelis developed a SARS-CoV-2 pseudotyped virus that is neutralized by antibodies like the wild-type, but lacks the gene for viral replication. This genetic alteration made the pseudotyped virus viable for use in BSL-2 facilities at high throughput. The quick adoption of a new production system showcases the strategic importance of Nexelis’ in house protein scientists. This is a unique function of Nexelis.


Another critical benefit of having in-house teams is the ability for direct collaboration. The Protein Sciences Team at Nexelis worked closely with the Clinical Team to produce customized and fully characterized reagents without reliance on a third-party vendor or commercial availability.


After meeting all initial criteria, the pseudotyped virus qualified for head-to-head technical bridging in pseudotyped neutralization assay (PNA) tests before being approved for use in clinical trials. Additionally, the pseudotyped virus and other particles are stress tested, and their long-term stability is assessed periodically to ensure reliability in the PNA results.


Ensuring Accuracy And Precision

After successfully producing the pseudotyped virus, Nexelis developed a robust PNA to assess immunogenicity.


In order to show the precision of the PNA, Nexelis participated Duke University’s concordance initiative. This initiative compared the results of 48 reference laboratories around the globe (18 using a wild-type assay and 30 a PNA method). The results demonstrate that Nexelis’ assay is best in class, assessing vaccine efficacy as accurately and precisely as the gold-standard wild-type assay. Because PNA assays can be performed in a high-throughput BSL-2 environment, Nexelis’ PNA solved a good portion of the industrial issue of constrained capacity feasible within a BSL-3 laboratory.


Additional Assay Development

Along with the PNA, Nexelis’ SARS-CoV-2 assay portfolio expanded to address humoral and cellular response, supporting preclinical to late phase clinical testing. Three ELISA assays were developed to assess the humoral response in its entirety:


• ELISA-S and ELISA-RBD assess antibodies that target the entire Spike protein and the Receptor Binding Domain respectively, which have been the most popular targets of vaccines


ELISA-N assesses antibodies targeting the Nucleocapsid, and was developed to assess pre-exposure to SARS-CoV-2

Additionally, ELISpot and flow cytometry assays were developed to assess the cellular response induced following immunization with SARS-CoV-2 Spike vaccines. The ELISpot assay is required to assess safety of new vaccine candidates and ensure a normal immune response. This evaluation is critical to test that the candidate does not cause an overproduction of cytokines, inducing a cytokine storm.


While stimulating both a humoral and cellular response is ideal for optimum protection against SARS-CoV-2, an overproduction of antibodies and/or cytokines can be harmful to an individual. Nexelis’ robust, validated assays help to ensure appropriate immune responses are triggered by the vaccines, while still providing the necessary results to ensure its safety.


To learn more about our robust assay development process and how we’ve stayed at the forefront of vaccine development against SARS-CoV-2, you can read our new ebook “Through A CRO’s Perspective: Innovative, Agile Solutions In Vaccine Efficacy Testing”. This ebook showcases how Nexelis’ agility and willingness to collaborate with industry competitors led to an unprecedented response to the SARS-CoV-2 pandemic and contributed to bringing effective vaccines to market.