ABSTRACT
The recent pandemic caused by the SARS-CoV-2 virus continues to be an enormous global challenge faced by the healthcare sector. Availability of new vaccines and drugs targeting SARS-CoV-2 and sequelae of COVID-19 has given the world hope in ending the pandemic. However, the emergence of mutations in the SARS-CoV-2 viral genome every couple of months in different parts of world is a persistent danger to public health. Currently there is no single treatment to eradicate the risk of COVID-19. The widespread transmission of SARS-CoV-2 due to the Omicron variant necessitates continued work on the development and implementation of effective vaccines. Moreover, there is evidence that mutations in the receptor domain of the SARS-CoV-2 spike glycoprotein led to the decrease in current vaccine efficacy by escaping antibody recognition. Therefore, it is essential to actively identify the mechanisms by which SARS-CoV-2 evades the host immune system, study the long-lasting effects of COVID-19 and develop therapeutics targeting SARS-CoV-2 infections in humans and preclinical models. In this review, we describe the pathogenic mechanisms of SARS-CoV-2 infection as well as the innate and adaptive host immune responses to infection. We address the ongoing need to develop effective vaccines that provide protection against different variants of SARS-CoV-2, as well as validated endpoint assays to evaluate the immunogenicity of vaccines in the pipeline, medications, anti-viral drug therapies and public health measures, that will be required to successfully end the COVID-19 pandemic.
ABSTRACT
In response to the SARS-CoV-2 pandemic many vaccines have been developed and evaluated in human clinical trials. The humoral immune response magnitude, composition and efficacy of neutralizing SARS-CoV-2 are essential endpoints for these trials. Robust assays that are reproducibly precise, linear, and specific for SARS-CoV-2 antigens would be beneficial for the vaccine pipeline. In this work we describe the methodologies and clinical qualification of three SARS-CoV-2 endpoint assays. We developed and qualified Endpoint titer ELISAs for total IgG, IgG1, IgG3, IgG4, IgM and IgA to evaluate the magnitude of specific responses to the trimeric spike (S) antigen and total IgG specific to the spike receptor binding domain (RBD) of SARS-CoV-2. We also qualified a pseudovirus neutralization assay which evaluates functional antibody titers capable of inhibiting the entry and replication of a lentivirus containing the Spike antigen of SARS-CoV-2. To complete the suite of assays we qualified a plaque reduction neutralization test (PRNT) methodology using the 2019-nCoV/USA-WA1/2020 isolate of SARS-CoV-2 to assess neutralizing titers of antibodies in plasma from normal healthy donors and convalescent COVID-19 individuals.