Intranasal application of polyethyleneimine suppresses influenza virus infection in mice

He, Biao; Fu, Yuhong; Xia, Shuai; Yu, Fei; Wang, Qian; Lu, Lu; Jiang, Shibo

In this regard, polyethyleneimine (PEI), a mucosal adjuvant, exhibits stronger mucosal adjuvanticity but induces much lower IL-17 expression than cholera toxin subunit B (CTB). 3 Therefore, for the first time, we tested PEI for its potential protective effects against influenza virus infection. Ten-week-old specific-pathogen-free (SPF) female Balb/c mice were anesthetized with pelltobarbitalum natricum. Then, 50 μL of PBS containing 20 μg of 25 kD linear PEI (Polysciences, Warrington, PA) or 2.5 μg of CTB (Sigma-Aldrich, St Louis, MO, USA) or PBS alone as a control was intranasally administered twice at 24 and 48 h before challenge with 5 LD 50 influenza virus H1N1 (A/PR/8/34). Mouse body weights were monitored every day, and those with greater than 25% loss of their initial body weight were euthanized as described. 4 As shown in Figure 1A , the body weight of the mice in the PEI-pretreated group remained stable from day 1 to day 5 after H1N1 challenge and then gradually decreased until day 11, for a total loss of 18%, before recovering. By contrast, the body weights of the mice in the CTB-and PBS-pretreated groups decreased significantly beginning on day 2 and reached losses of more than 25% by day 8 and 10, respectively, after H1N1 challenge. The final survival rate of the mice in the PEI-pretreated group was 60%, whereas that of the mice in the CTB-and PBS-pretreated groups was 0% ( Figure 1B) . We then examined the viral titers in mouse lungs as previously described 5 and found that PEI significantly reduced lung viral titers on day 2 after H1N1 challenge, whereas the viral titers in the lungs of mice in the CTB-and PBS-pretreated groups showed no significant differences ( Figure 1C ). Subsequently, we examined lung sections stained with hematoxylin and eosin as previously described. 2 On day 2 after H1N1 infection, the pulmonary alveoli were relatively intact, and only a few inflammatory cells were observed in the lung tissues of mice in the PEI-pretreated group. However, the lungs of mice in the CTB-and PBS-pretreated groups were filled with abundant inflammatory cells ( Figure 1D ). These results suggest that intranasal application of PEI has efficacy in protecting mice from challenge by influenza virus H1N1.