By: Richard Liang 18’

Vaccination is one of the best methods to guard against influenza, as it allows human dendritic cells (DCs) to promote long-term adaptive immunity. Due to the rapid pace of influenza mutation, the composition of influenza vaccines varies annually, with a focus on immunogenicity as opposed to vaccine efficacy. To improve efficacy, immunological agents known as adjuvants can be added to vaccines. In the United States, however, adjuvants are not added to vaccines, due to the possibility of adverse physiological reactions. In a recent study led by Shruti Athale from the Baylor Institute for Immunology Research, it was discovered that subtypes of nonadjuvanted vaccines promote immunity with different mechanisms, offsetting the loss of efficacy in the absence of adjuvants.

According to the results of this experiment, different subtypes of nonadjuvanted vaccines trigger different molecular signaling pathways in DC subsets. The effects of the nonadjuvanted monovalent H1N1 Calfiornia vaccine (MIV-09) and nonadjuvanted trivalent Fluzone 2009-2010 vaccine (TIV-09) were compared in cultures of human monocytes. In previous studies, MIV-09 was determined to be less effective than TIV-09, though the reason for this was unknown. In these cultures, it was discovered that both MIV-09 and TIV-09 induce plasmacytoid DCs to secrete type I interferons (IFNs), a factor known to assist in the development of immune system cells such as DCs and B cells. However, only TIV-09 was observed to stimulate secretion of IFNs from monocyte-derived DCs and conventional DCs. TIV-09 also induced the secretion of other immunity factors like macrophage inflammatory protein-1β (MIP-1β), IL-6, tumor necrosis factor, and chemokines IFN-g-inducible protein 10 (IP-10), while MIV-09 did not.

While these additional secretions might be the key to the increased effectiveness of TIV-09 as an influenza vaccine compared to MIV-09, it is important to note the limitations of the study. The researchers cautioned that the results may not be representative of in situ events, as they utilized an in vitro model. It can be concluded that research will lead to the development of influenza vaccines with higher efficacies, even without adjuvants.

References

1. Athale, et al., Influenza vaccines differentially regulate the interferon response in human dendritic cell subsets. Science Translational Medicine 9, (2017). DOI: 10.1126/scitranslmed.aaf9194

Image retrieved from: http://www.pixnio.com/free-images/science/microscopy-images/influenza/3-dimensional-model-of-influenza-subtypes-found-in-people-are-influenza-a-h1n1-and-influenza-a-h3n2-viruses.jpg