Human Antibody Responses to Avian Influenza A(H7N9) Virus, 2013

Abstract

Understanding host antibody response is crucial for predicting disease severity and for vaccine development. We investigated antibody responses against influenza A(H7N9) virus in 48 serum samples from 21 patients, including paired samples from 15 patients. IgG against subtype H7 and neutralizing antibodies (NAbs) were not detected in acute-phase samples, but ELISA geometric mean titers increased in convalescent-phase samples; NAb titers were 20–80 (geometric mean titer 40). Avidity to IgG against subtype H7 was significantly lower than that against H1 and H3. IgG against H3 was boosted after infection with influenza A(H7N9) virus, and its level in acute-phase samples correlated with that against H7 in convalescent-phase samples. A correlation was also found between hemagglutinin inhibition and NAb titers and between hemagglutinin inhibition and IgG titers against H7. Because of the relatively weak protective antibody response to influenza A(H7N9), multiple vaccinations might be needed to achieve protective immunity.

Sero‐epidemiologic study of influenza A(H7N9) infection among exposed populations, China 2013‐2014

“…Among samples with elevated HI titers, we observed relatively lower corresponding MN titers. This was consistent with previous experience in which the neutralizing antibody response among confirmed influenza A(H7N9) cases was relatively weak compared with the neutralizing antibody response against the 2009 pandemic A(H1N1) and avian influenza A(H5N1) virus using a similar MN assay21.…”

“…This may have led to a lower seroprevalence among poultry workers than we would have found had we only enrolled workers from LPMs with positive influenza A (H7N9) environmental samples. Finally, it is important to note that serologic testing may not detect all infections due to waning or lack of antibody response to influenza A(H7N9) infection, especially mild infection, and thus, our study may underestimate influenza A(H7N9) infection rates during the early stages of the outbreak15, 21.…”

Suboptimal Humoral Immune Response against Influenza A(H7N9) Virus Is Related to Its Internal Genes

“…MN titers were also lower than HI titers in patients infected with A(H7N9) virus. Guo et al (19) showed that the MN titers of A(H7N9) patients were only 20 to 80 in serum samples collected 102 to 125 days after symptom onset, compared to HI titers of 80 to 640 for the same samples (19). The MN titers after A(H7N9) infection were also much lower than those induced by A(H5N1) virus infection, in which the MN GMT in convalescent patients was 540 at 1 to 2 months after symptom onset (20).…”

T cell epitope engineering: an avian H7N9 influenza vaccine strategy for pandemic preparedness and response

“…20 The results of alternative vaccine strategies have also been subpar with both inactivated H7N9 split vaccine and H7N9 HA virus-like particle vaccine eliciting HI seroconversion rates of only 6% and 15.6% in Phase I trials respectively. 21,22 This compares poorly with the ~ 89% rate reported for similar seasonal influenza subunit vaccines. 23–25 Even with the addition of adjuvant and a booster injection, the inactivated split H7N9 vaccine elicited HI seroconversion in only 59% of subjects in an early Phase II clinical trial.…”