Distribution and levels of neutralizing antibody of H1N1 and H3N2 influenza virus in the blood donors in Guangzhou

Objective To explore positive rate and titer of neutralizing antibody levels of H1N1 and H3N2 influenza virus in blood donation population in Guangzhou, in order to provide a reference for the study of the epidemiological characteristics of influenze virus in Guangzhou area. Methods From October to November 2015, a total of 498 healthy blood donors were included in this study by age-stratified random sampling method. All the donors were divided into 3 groups according to age: 18-20 years old group(n=150), 21-30 years old group(n=210) and 31-60 years old group(n=138). Titer of neutralizing antibody levels of H1N1 and H3N2 influenze virus were tested by micro neutralization titration experiment, and positive rate and titer levels of differents gender and age were analyzed statistically, respectively. Results In 498 healthy blood donors, the positive rates of H1N1 and H3N2 influenze virus neutralizing antibody were 3.6% (18/480) and 4.6% (23/498) respectively, and no statistical difference was found between these two influenze virus subtypes (χ2=0.636, P=0.425). The positive rates of H1N1 and H3N2 influenze virus neutralizing antibody in 156 male donors were 3.8%(6/156) and 4.5%(7/156)respectively, and were 3.2%(11/342) and 4.4%(15/342)in 342 female donors respectively. There were no significant differences in the positive rates of H1N1 and H3N2 influenze virus neutralizing antibody in different genders (χ2=0.129, 0.003; P>0.05). The positive rates of H1N1 influenze virus neutralizing antibody in 18-20 years old group, 21-30 years old group and 31-60 years old group were 4.0%, 5.2% and 0.7% respectively, and 6.0%, 5.2% and 2.2% of H1N1 influenze virus neutralizing antibody in each group respectively. There were no significant differences in the positive rates of H1N1 and H3N2 influenze virus neutralizing antibody in 3 groups (χ2=4.961, 2.705; P>0.05). The geometric mean titer (GMT) of H1N1 influenze virus neutralizing antibody in 18-20 years group, 21-30 years group and 31-60 years group were 1∶1.38, 1∶1.48 and 1∶1.05 respectively, for an average of 1∶1.32; while those of H1N1 influenze virus neutralizing antibody in 18-20 years group, 21-30 years group and 31-60 years group were 1∶1.62, 1∶1.51 and 1∶1.19 respectively, for an average of 1∶1.44. There were no significant differences of antibody titers of H1N1 and H3N2 influenze virus neutralizing antibody among these 3 groups (χ2=4.887, 2.702; P>0.05). Conclusions The neutralizing antibody levels of H1N1 and H3N2 influenza virus were low in the blood donors in Guangzhou area, and people of different gender and age are generally susceptible to influenza virus. Key words: Influenza, human; Influenza A virus, H1N1 subtype; Influenza A virus, H3N2 subtype; Blood donors; Antibodies, neutralizing