Investigation on the host factors that are associated with the immunogenicity of influenza vaccine

Abstract

Influenza is an infectious disease that is caused by influenza viruses. The annual mortality rate associated with this respiratory disease is estimated between 300,000 and 600,000, most of which are elderly people. Vaccination is one of the effective approaches to prevent the infection of the influenza A virus (IVA), a subtype that mainly infects humans. However, antibody waning is a major issue that is observed from the vaccinated elderly resulting in a shorter period of protection. The reason why there is shorter durability of vaccine protection in the elderly is still not clear. I hypothesized that host factors including the immunological or metabolic status in the elderly may correlate with the immunogenicity or durability of the influenza vaccine. To address this question, I recruited fourteen volunteers aged above 60 years to participate in my observational study. Sixteen participants aged at or below 60 years were served as the control group. The blood samples were collected before vaccination as well as 7 days, 1 month, 6 months, and 12 months after vaccination. Stool samples were additionally collected before vaccination. The levels of cytokines, metabolites, and influenza-specific antibodies in the blood, as well as the composition of the microbiota in stool, were measured from the participants. My cohort study showed that vaccinees who were aged above 60 years had a lower level of influenza-specific neutralizing antibodies at 12 months after vaccination compared to the group who were aged at or below 60 years. Correlation analysis showed that lower levels of specific metabolites including isobutyrate, butyrate, and caproate before vaccination in those above 60 years old were correlated to their lower influenza-specific neutralizing antibodies at 12 months after vaccination. Taken together, my study established a multi-omics analysis platform to determine the host factors that are associated with the antibody waning in the elderly after receiving the influenza vaccine.