South SFV Today

Researchers at Stanford Medicine have made significant strides in understanding the longevity of vaccine responses. A study led by Bali Pulendran, PhD, a professor of microbiology and immunology, suggests that megakaryocytes, blood cells typically involved in clotting, play a role in determining how long vaccines remain effective.

Pulendran's research reveals "a molecular signature in the blood" that emerges shortly after vaccination and predicts how durable a vaccine's response will be. This finding is detailed in a paper published on January 2nd in Nature Immunology. The study involved postdoctoral scholars Mario Cortese, PhD, now with Gilead Sciences, and Thomas Hagan, PhD, currently an assistant professor at the University of Cincinnati College of Medicine. Nadine Rouphael, MD from Emory University also contributed significantly to the research.

The researchers conducted an experiment using an experimental H5N1 bird flu vaccine with and without an adjuvant to enhance immune response. They tracked 50 volunteers over 100 days post-vaccination to analyze genes, proteins, and antibodies present in their blood samples. A machine-learning program was used to identify patterns correlating with antibody response durability.

Findings indicated that RNA within platelets – derived from megakaryocytes – can serve as indicators for vaccine durability. This was further supported by experiments on mice where thrombopoetin increased levels of anti-bird flu antibodies when given alongside the vaccine.

"Our hypothesis is that megakaryocytes are providing this nurturing, pro-survival environment in the bone marrow for plasma cells," said Pulendran.

The team also explored whether these findings applied to other vaccines like those for influenza and COVID-19. The same platelet RNA molecules were linked with prolonged antibody production across different vaccines.

Looking forward, Pulendran’s group aims to explore why certain vaccines activate more megakaryocytes initially. Their goal is to create tests based on their molecular signature discovery to predict vaccine longevity swiftly and accurately.

“We could develop a simple PCR assay – a vaccine chip – that measures gene expression levels in the blood just a few days after someone is vaccinated,” Pulendran explained.

This work received support from multiple institutions including NIH grants R01 AI048638 and U19 AI167903 among others. Collaborators came from various universities and organizations such as Emory Vaccine Center and NYU Grossman School of Medicine.

Pulendran has been involved with advisory boards for companies like Sanofi and Medicago Inc., emphasizing his extensive engagement within immunology circles.