Early Antibody Response Contributes to the Virus Eradication and Clinical Recovery of H7N9 Influenza Infection.

A new type of highly pathogenic avian influenza virus, H7N9, has been a great threat to public health since its 2013 outbreak. The humoral immune response plays a critical role in protection from the influenza virus, but its role and kinetics in H7N9-infected patients remain to be determined. In this study, we performed a retrospective investigation of the antibody response in plasma samples from 37 cases of hospitalized patients and analysed the relationship between the antibody response and the clinical outcomes. Our results showed that the HA7-binding antibody was generated earlier than the neutralizing antibody. Higher titer of HA7-binding antibody during the first 14 days after disease onset were associated with a shorter virus-positive continuation period, which is an important risk predictor (<0.05). Additionally, the titers of HA7-binding antibody were consistently and significantly lower in patients who died than those who recovered from the severe disease. Unexpectedly, no correlation between the titer of neutralizing antibody and the resulting clinical outcomes was found, suggesting that a neutralizing antibody-independent mechanism also contributed to virus control. In summary, our data suggests that an early antibody response against H7N9 influenza virus contributes to the eradication of the virus. A higher, early HA7-binding antibody response is associated with better clinical outcomes in H7N9 patients.