Each design produced antibodies to varying degrees, but one design, ED2, had a robust immune response. In the end, the researchers developed four stable immunogen designs which were used to immunize mice, who then produced antibodies against SARS-CoV-2. The proteins were then purified and studied in the lab to ensure they closely matched with their virtual counterparts. The team used recombinant expression, a technique where bacteria are given the genetic instructions to make proteins, to create the virtually designed immunogens. The flower may be the part of the interest, but it’s not viable without the stem that offers structure and support.” This is similar to how a flower (epitope) might need its stem (scaffold protein) to survive. “Epitopes, which are small fragments of the protein, are not stable on their own in solution, so they need to be grafted to a larger protein for stability. “Proteins are complex structures that are built to withstand a variety of physical and chemical challenges in nature,” said Yashavantha Vishweshwaraiah, postdoctoral scholar in the Department of Pharmacology and first author on the paper. ![]() Dokholyan has previously described this computational biology approach. Computer simulations were used to test the stability of the immunogens. The immunogens were then structurally optimized through various design modifications, including stabilizing mutations. These areas, called epitopes, were then matched and grafted, or attached, to protein scaffolds, which provided stability to the epitopes while in solutions. The team designed the immunogens by using computational biology to identify three regions of the spike protein that remain conserved in millions of theoretical mutations that could occur. Unlike current vaccines on the market, these immunogens are designed based on conserved regions of the spike protein, areas that are less susceptible to mutation. Just weeks after the Centers for Disease Control and Prevention approved a new bivalent COVID-19 vaccine, the researchers published a study about the design and efficacy of their immunogens, which target the virus in a different way. “We identified areas of the spike protein that are least likely to mutate and used that information to engineer new proteins, which could be used to develop a vaccine that protects more broadly against not only future COVID-19 variants but potentially other related coronaviruses.” Thomas Passananti Professor and vice chair for research in the Department of Pharmacology. “Variants of concern continue to emerge due to the spike protein’s susceptibility to mutations,” said Nikolay Dokholyan, G. Existing vaccines target the receptor binding domain (RBD) of the spike protein, but the susceptibility of RBD to mutations provides escape routes for the virus from neutralizing antibodies. SARS-CoV-2’s surface spike protein - a major antibody target - allows the virus to enter host cells by engaging with a receptor called angiotensin-converting enzyme 2. ![]() The scientists used areas of the SARS-CoV-2 virus that are less susceptible to mutation to engineer proteins called immunogens, which can elicit an immune response. A vaccine design approach that could protect against new variants of SARS-CoV-2 - the virus that causes COVID-19 - but also potentially protects against other coronaviruses is one step closer to reality as a result of research at Penn State College of Medicine.
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