The
influenza A H7N9 virus outbreak in Eastern China in the spring of 2013 represented a novel, emerging
avian influenza transmission to humans. While clinical and microbiological features of H7N9
infection have been reported in the literature, the current study investigated acute
cytokine and antibody responses in acute H7N9
infection. Between March 27, 2013 and April 23, 2013, six patients with confirmed H7N9
influenza infection were admitted to Drum Tower Hospital, Nanjing, China. Acute phase serum
cytokine profiles were determined using a high-throughput multiplex assay. Daily
H7 hemagglutinin (HA)-specific
IgG,
IgM, and
IgA responses were monitored by ELISA.
Neutralizing antibodies specific for H7N9 viruses were determined against a pseudotyped virus expressing the novel H7 subtype HA
antigen. Five
cytokines (IL-6, IP-10, IL-10, IFNγ, and TNFα) were significantly elevated in H7N9-infected patients when compared to healthy volunteers. Serum H7 HA-specific
IgG, as well as
IgM and
IgA responses, were detected within 8 days of disease onset and increased in a similar pattern during acute
infection.
Neutralizing antibodies developed shortly after the appearance of binding antibody responses and showed similar kinetics as a fraction of the total H7 HA-specific
IgG responses. H7N9
infection resulted in hallmark serum
cytokine increases, which correlated with
fever and disease persistence. The novel finding of simultaneous development of
IgG,
IgM, and
IgA responses in acute H7N9
infection points to the potential for live influenza viruses to elicit fast and potent protective
antibodies to limit the
infection.