The duration and nature of humoral immunity to SARS-CoV-2 (CoV2) infection is poorly understood. Most studies have focused on the immune response in patients with clinical illness, but little is known about antibody response to CoV2 regarding the earliest immunological events immediately after exposure and prior to onset of illness or in asymptomatic individuals and how this impacts long-term immunological memory. This proposal addresses these gaps in our knowledge by prospectively following household contacts with clinical cases of CoV2 to determine innate and adaptive immune events associated with this early viral exposure over a 28 day period. Detailed evaluation of samples from these patients including RNAseq of peripheral blood cells and proteomic analysis of oral secretions, the site of initial CoV2 replication. We will determine whether potentially cross-reactive T cells and secretory IgA may contribute to this early protective immune response and if present do they enhance the subsequent humoral immune responses by providing greater T cell help to B cells. These studies will also provide a detailed knowledge of innate immune responses to CoV2 and how this shapes the nature and duration humoral immunity. Our central hypothesis is that peripheral blood lymphocytes and oropharyngeal secretions collected from individuals at the time of viral exposure and prior to onset of symptoms will show innate and adaptive immune responses that correlate with viral clearance and predict whether or not effective humoral immunity and long-term immunological memory develops. This hypothesis will be addressed by exploring the following aims; i) evaluating the early immune humoral and cellular immune responses to CoV2 in close contacts of individuals diagnosed with COVID-19; ii) to assess early innate immune responses in close contacts of individuals diagnosed with COVID-19 and assess their relationship with humoral immune responses and viremia; and iii) to examine early drivers of humoral immunity on the durability of immunological memory and responses to vaccines. This comprehensive evaluation of the relationships between early infection with innate and adaptive immune on long-term memory and immunity will provide a rigorous basis for the development of highly informative and scalable serological tests. Our approach is therefore highly responsive to RFA-CA-20-039, through the development and validation of novel assays that simultaneously measure innate and adaptive immune responses to CoV2 from early infection; this approach will help define immune parameters and serological markers associated with asymptomatic vs. symptomatic infection and disease severity.
The study examines events associated with initial exposure to COVID-19 by following close household contacts of individuals with documented COVID-19 over a period of 28 days. From this study we will begin to learn why most individuals are asymptomatic or develop mild symptoms following infection and whether some pre-existing immunity is important. We will also learn whether they develop partial immunity to the SARS-CoV2 virus, what are markers of this immunity and how long this persists. We will develop novel tests, using the most informative markers, to screen the mouth, upper airways and blood in high risk populations, which will predict who will get seriously sick and who will be minimally impacted by the virus.
