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The Power of First Impressions: Can Influenza Imprinting during Infancy Inform Vaccine Design?
Melissa Rioux1, Mara McNeil1, Magen E Francis1,2
1Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, NS B3H 4R2, Canada.
Insights
Infant influenza imprinting, the first infection establishing lifelong immunity, is key to developing better vaccines. Understanding this process in infant immune systems can improve protection for all age groups.
Area of Science:
- Immunology
- Virology
- Vaccinology
Background:
- Influenza causes severe respiratory illness globally, with infants disproportionately affected due to immature immune systems and respiratory tracts.
- Current influenza vaccines show reduced efficacy in infants and children under two years old, with no vaccines available for infants under six months.
- Infant immune systems differ significantly from adults, possessing fewer antigen-presenting cells and soluble immune factors, impacting vaccine responses.
Purpose of the Study:
- To explore the concept of influenza imprinting in infants and its implications for vaccine design.
- To understand how the infant immune system's response to initial influenza infection influences long-term immunity.
- To highlight the necessity of infant animal models for studying influenza imprinting and improving vaccine strategies.
Main Methods:
- Review of existing literature on infant immune and respiratory development in the context of influenza.
- Examination of current influenza vaccine strategies and their limitations in pediatric populations.
- Emphasis on the utility of infant influenza animal models (mice, ferrets) for studying imprinting.
Main Results:
- First-time influenza infection in infancy or childhood establishes lifelong immunity to that specific strain (influenza imprinting).
- Infant immune systems exhibit unique characteristics that affect both disease severity and vaccine immunogenicity.
- Infant animal models are crucial for elucidating the mechanisms of influenza imprinting.
Conclusions:
- Understanding influenza imprinting within the infant immune system is critical for designing more effective influenza vaccines.
- Research utilizing infant animal models can provide insights into optimizing vaccine efficacy for all age groups, including young children.
- Targeting the imprinting event offers a novel approach to enhance long-term influenza protection and vaccine development.
Abstract:
Influenza virus infection causes severe respiratory illness in people worldwide, disproportionately affecting infants. The immature respiratory tract coupled with the developing immune system, and lack of previous exposure to the virus is thought to synergistically play a role in the increased disease severity in younger age groups. No influenza vaccines are available for those under six months, although maternal influenza immunization is recommended. In children aged six months to two years, vaccine immunogenicity is dampened compared to older children and adults. Unlike older children and adults, the infant immune system has fewer antigen-presenting cells and soluble immune factors. Paradoxically, we know that a person's first infection with the influenza virus during infancy or childhood leads to the establishment of life-long immunity toward that particular virus strain. This is called influenza imprinting. We contend that by understanding the influenza imprinting event in the context of the infant immune system, we will be able to design more effective influenza vaccines for both infants and adults. Working through the lens of imprinting, using infant influenza animal models such as mice and ferrets which have proven useful for infant immunity studies, we will gain a better understanding of imprinting and its implications regarding vaccine design. This review examines literature regarding infant immune and respiratory development, current vaccine strategies, and highlights the importance of research into the imprinting event in infant animal models to develop more effective and protective vaccines for all including young children.
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