The microRNA-let-7b-mediated attenuated strain of influenza A (H1N1) virus in a mouse model.
BACKGROUND
Evaluating the attenuation of influenza viruses in animal studies is important in developing safe and effective vaccines. This study aimed to demonstrate that the microRNA (miRNA)-let-7b-mediated attenuated influenza viruses (miRT-H1N1) are sufficiently attenuated and safe in mice.


METHODS
The pathogenicity of the miRT-H1N1virus was investigated in a mouse model, evaluated with median lethal dose (LD50). The replicative dynamics of the miRT-H1N1, wild type (wt)-H1N1, and scramble (scbl)-H1N1 viruses in the lungs of infected mice were compared. The degrees of lesions and the expression levels of IL-6, TNF-α, and IFN-β in the lungs of mice infected with different viruses were also analyzed.


RESULTS
In miRT-H1N1 virus-infected mice, 100% of mice survived, and a lower pathogenicity was characterized with non-significant weight loss when compared to mice infected with the control wt virus. The miRT-H1N1 virus was not fatal for mice, even at the highest dose administered. The viral load in the lungs of miRT-H1N1-infected mice was significantly lower than that of the wild-type virus-infected mice. Fewer pulmonary lesions and lower levels of selected pro-inflammatory cytokines in the lungs of the mice infected with the miRT-H1N1 virus were also observed. The virulence of the miRT-H1N1 virus reduced significantly, suggesting that the miRT-H1N1 virus was safe for mice.


CONCLUSIONS
Our study demonstrated that the miRNA-mediated gene silencing is an alternative approach to attenuating the pathogenicity of wt influenza viruses that have potential in the development of influenza vaccines.
Jinling Hospital, Nanjing University School of Medicine, Nanjing, China. xiyoujay@126.com.
Mingming
M
Tan
Wenkui
W
Sun
Chunlai
C
Feng
Di
D
Xia
Xiaoyue
X
Shen
Yuan
Y
Ding
Zhicheng
Z
Liu
Zheng
Z
Xing
Xin
X
Su
Yi
Y
Shi
D000818:Animals; D001665:Binding Sites; D016207:Cytokines / Q000032:analysis; D005260:Female; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000472:pathogenicity*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects*; D007928:Lethal Dose 50; D008168:Lung / Q000473:pathology* / Q000821:virology; D008807:Mice, Inbred BALB C; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000009:adverse effects; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000009:adverse effects
D016207:Cytokines; D007252:Influenza Vaccines; D035683:MicroRNAs; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; C542687:mirnlet7 microRNA, mouse