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Principal Investigator: Mark Connors
Organization: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
Fiscal Year: 2020
Award: $109,107
Funding agency: National Institute of Allergy and Infectious Diseases
Our laboratory is engaged in the study of the immune response to SARS-CoV-2 in two major areas. The first of these is the study of the immune response to natural infection. The second is the response to virus-like particles or replicating recombinant adenovirus type 4 vaccines.
We are collaborators on a large natural history study of up to 300 survivors of SARS-CoV-2 and their household contacts, led by Dr. Michael Sneller. In this study, serum and peripheral blood mononuclear cells are sampled during acute infection and over 3 years. Our laboratory will be primarily responsible for measuring the cellular immune response to SARS-CoV-2 gene products. A large panel of functions of T cells specific for SARS-CoV-2, including frequency, cytokine secretion, and cytolytic capacity, will be measured over time to examine the dynamics of frequency and functions, and the potential correlations with disease severity.
In a separate effort, two vaccine platforms that are being developed for HIV, have been repurposed to induce immunity against SARS-CoV-2. Over the past several years our section has developed several vaccine platforms for use as vaccines to present viral surface glycoproteins. Both replicating vectors and virus-like particles (VLPs) have proven to be highly immunogenic platforms in rabbit and human studies. After vaccination with Ad4 expressing influenza H5 Vietnam (Ad4-H5-Vtn), participants developed levels of neutralizing antibodies that were much higher and more durable than those induced by the licensed Sanofi vaccine (Matsuda et al., Science Immunology, 2019). In addition, H5-specific B cell expansions, and neutralizing antibody hypermutation and potency, continued for 6-12 months after a single intranasal vaccination. Vaccinee responses could be increased to even higher levels by boosting with the licensed H5 vaccine. More recently, we have developed VLP platforms to present viral surface glycoproteins. For RSV, this platform has been shown to induce levels of neutralizing antibodies above those induced by RSV infection in small animals. In our work, we have been able to use VLPs to induce H5-specific neutralizing antibodies titers in rabbits of approximately 1:1000 after two immunizations.
The reason for the HSIS to pursue the COVID-19 spike protein in these formats is two-fold. First, it will provide us with experience with another viral surface glycoprotein beyond HIV, RSV, and influenza. Second and more important, most of the approaches being considered as vaccines against COVID-19 are not complex, high valency particles, or replicating vaccines. Of the currently licensed anti-viral vaccines, only two forms provide a sufficiently potent B cell stimulus that they confer lifelong immunity. These are live-attenuated viruses and virus-like particles. Over the past several years there has been great progress in understanding the immunology that underlies the success of these approaches. Both have the potential to present the nave B cell with viral surface glycoproteins in the appropriate conformation that approximates the disease causing virus against which they protect. They can induce pro-inflammatory cytokines and contain TLR agonists that drive B cell responses. Perhaps most importantly, they are particulate in nature. There is very good experimental evidence that particulate immunogens are considerably more potent than other forms. The COVID-19 spike protein is immunogenic, relatively conserved, and with regard to immunogenicity, should behave similarly to stabilized RSV F or influenza H5. For these reasons, we feel that the more immunogenic replicating or VLP approaches will provide an important complement to other approaches being pursued.
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