[Cross-reaction of seasonal influenza vaccine immune serum against Eurasian Avian-like H1N1 swine influenza virus].

ABSTRACT

Objective: To evaluate the cross-reaction of seasonal influenza vaccine immune serum against Eurasian avian-like H1N1 swine influenza virus. Methods: Nine human infected Eurasian avian-like H1N1 swine influenza virus strains were obtained from national influenza surveillance network laboratories in Jiangsu, Hebei, Shandong, Yunnan, Hunan, Fujian and Tianjin provinces, and their genetic characteristics of hemagglutinin were analyzed by deep sequencing. 30 volunteers were recruited respectively from children (2-5 years old), adults (24-57 years old) and elderly (60-84 years old) who received 2019-2020 seasonal influenza vaccine in Anning city, Yunnan Province in October 2019, and serum samples were collected before and 1 month after vaccination. The hemagglutination inhibition test was used to evaluate the cross-reaction of serum before and after immunization against 4 strains of human infection with Eurasian avian-like H1N1 swine influenza virus isolated since 2015. Results: The homology of hemagglutinin genes of 9 Eurasian avian-like H1N1 swine influenza viruses was similar, but the difference of hemagglutinin heavy chain and light chain amino acid genes with A (H1N1) pdm09 (vaccine strain) were 90-101 and 24-30 amino acids respectively. The antibody titer of vaccine strain antiserum to vaccine strain was 2 560; the antibody titers of the vaccine strain antiserum to Eurasian avian-like H1N1 swine influenza virus and the Eurasian avian-like H1N1 swine influenza virus antiserum to vaccine strain were same as 640. The proportion of children, adults and elderly vaccinated with seasonal influenza vaccine with antibody titer ≥40 against vaccine strain was 90.0%, 70.0% and 73.3%, respectively; while the proportion merely were 46.7%, 36.7% and 33.3%-43.3% to 4 strains of Eurasian avian-like H1N1 swine influenza virus, respectively. Conclusion: Seasonal influenza vaccination does not provide effective cross-protection against Eurasian avian-like H1N1 swine influenza virus.