3.4 Replication of H6N6 subtype AIV in human lung tissue
Lung and bronchus tissues of humans were collected at 12h, 24h, and 48h post-inoculation of H6N6 viruses, after which they were ground. Their supernatant was then inoculated in 10-day-old embryonated chicken eggs and MDCK cells. In the isolation and culture of embryonated chicken eggs, the virus was detected in the lungs of humans inoculated with ZZ346, the HA titers on days 3 post-inoculation were 1:8; it was not observed for ZZ1923 and JX20490 virus. For MDCK isolation, three strains were not detected. The lung tissue inoculated with ZZ346 strain showed that lung tissue structure was destroyed, inflammatory cells such as lymphocytes and monocytes infiltrated in lung interstitial and bronchiolar mucosal epithelium necrosed and fell off. However, the obvious pathological changes of lung tissue inoculated with ZZ1923 and JX20490 virus strain were not observed. But there were no obvious histopathological changes in bronchial tissue inoculated with three strains of the H6N6 virus.
The immunohistochemical method was used to detect NP protein of influenza virus in bronchial and lung inoculated with three strains of the H6N6 virus. The virus NP protein was detected in alveolar cells of lung inoculated with ZZ346 virus strain, while was not detected in human lung tissues of JX20490 and ZZ1923 virus strain (Figure 6 ). NP protein of influenza virus was not detected in bronchus and bronchioles inoculated with three strains of H6N6. Our study suggested that the ZZ346 strain of the H6N6 virus, with binding to avian-like SAα-2,3Gal and human-like SAα-2,6Gal, was effectively replicated in the human lung without prior adaptation.