Wild-Type Human Adenovirus (Serotype 26)

Human adenovirus type 26 (HAdV26) has been recognized as a promising platform for vaccine vector development, and a COVID-19 vaccine based on HAdV26 has recently been approved for emergency use. However, the basic biology of the virus, namely the pathway by which HAdV26 enters cells, remains poorly understood. Here, researchers show that infection of human epithelial cells expressing low amounts of αvβ3 integrin by HAdV26 involves clathrin and is independent of caveolin-1, whereas HAdV26 infection of cells expressing high amounts of αvβ3 integrin does not involve clathrin but is dependent on caveolin-1. Thus, caveolin-1 is a limiting factor for αvβ3 integrin-mediated HAdV26 infection. HAdV26 infection involves dynamin-2 regardless of αvβ3 integrin expression. These data describe for the first time the cellular entry pathway of HAdV26, enriching our understanding of HAdV26 infection. Given that the function of adenoviral vectors is influenced by their cellular entry pathways and intracellular trafficking, these findings will help to better understand the immunogenicity and antigen presentation of HAdV26 when used as a vaccine vector.

The researchers used specific siRNA to reduce the expression of dynamin-2 and studied how its reduced expression affected the transduction efficiency and cellular internalization of HAdV26. After transfection of A549 cells with dynamin-2-specific siRNA, the expression of dynamin-2 was reduced to 0.23 compared with A549 cells transfected with control siRNA. After downregulating dynamin-2 in A549 cells, the transduction efficiency of HAdV5 (reduced to 0.30) and HAdV26 (reduced to 0.72) was reduced (Figure 1A), and the internalization of fluorescently labeled HAdV5 (reduced to 0.67) and HAdV26 (reduced to 0.81) was also reduced (Figure 1B-E), indicating that HAdV26 enters cells through dynamin-2-dependent endocytosis. To further confirm the role of dynamin-2 in HAdV26 infection, the researchers treated A549 cells with dyngo 4a, a specific inhibitor of dynamin-2-dependent endocytosis, and tested the transduction efficiency of HAdV26 in cells. Compared with untreated cells, Dyngo 4a treatment reduced the transduction efficiency of HAdV26 by nearly 50% (Figure 1F).

Figure 1. HAdV26 cell infection involves dynamin-2 (DNM2). (Nestić D, et al., 2022)