Objective To determine the function of conserved amino acids in the fusion-promoting domain of Newcastle disease virus (NDV) hemagglutinin-neuraminidase (HN) protein,clearly understanding mechanism of cell fusion.MethodsUsing a PCR-based site-directed mutagenesis method and the method of homology recombination occurred in vivo to change six conservative amino acids into alanine respectively.Wild type (WT) and all mutant HN proteins were exepressed in BHK-21 cells by the vacciniaT7 RNA polymerase expression system.The amount of each HN protein at the cell surface was determined by fluorescence-activated cell sorter (FACS).Cell fusion efficiency,hemadsorption activity (or receptor binding activity) and neuraminidase activity were determined.Results There was no statistic difference of cell surface expression among WT and each mutant HN protein ( P＜0.05 ).Cell fusion efficiency of each mutant protein decreased to some extent,especially 1103A decreased to 14.2％ in head.Hemadsorption activity of mutant proteins were reduced in different extent,the maximum reduction of which was also 1103A,28.2％ of wt NDV HN.There was different neuraminidase activity among each mutant HN protein.L74A increased slightly to 118.6％.L110A decreased most to 5.2％.I103A decreased second most to 5.7％.Conclusion Conserved amino acids in fusion-promoting domain of NDV HN played an important role in cell fusion.I103 was identified as a key amino acid in this domain.

Objective To analyze the positive features of cytomegalovirus antibodies in children aged 0-12 years in Shandong.Methods 1 429 inpatients and outpatiens w ho came to Shandong Provincial Hospital Affil-iated to Shandong University from January 2014 to December 2016 were enrolled in the study.Cytomegalovir-us IgG and IgM antibodies were detected by chemiluminescence.SPSS21.0 software was used for statistical a-nalysis.Results The positive rate of IgG and IgM antibody of cytomegalovirus was 89.36% and 16.59% re-spectively,and the positive rate of IgG antibody of cytomegalovirus in male was 88.04%,which was signifi-cantly lower than 91.32% in female (P<0.05).The positive rate of cytomegalovirus IgM antibody in male was 14.07%,which was significantly lower than 20.31% in female (P<0.05).The positive rate of IgG anti-body of cytomegalovirus was the lowest in 6-12 months age group ( 73.68%),the highest in 0-<6 months age group (92.73%);cytomegalovirus IgM antibody positive rate was the lowest in 4-12 year-old age group (10.26%),and the highest in 1-3 year-old age group (21.57%).The positive rate of IgM antibody of cyto-megalovirus was the highest in winter (22.92%) and the lowest in autumn (11.11%),and the differences of positive rate between the four seasons were statistically significant (P<0.05).A total of 4 cytomegalovirus antibody combination patterns were detected,with the most common type of cytomegalovirus IgG antibody positive and cytomegalovirus IgM antibody double negative,accounting for 73.27%.Conclusion There were differences in sex,age and season in the positive rates of CMV antibody in Shandong area.Prevention and con-trol of cytomegalovirus infection in children should be strengthened.

Objective To determine the functions of conserved amino acids in the receptor-binding domain of human parainfluenza virus type 3 (hPIV3) hemagglutinin-neuraminidase(HN) protein.Methods Using a PCR-based site-directed mutagenesis method and the method of homology recombination occurred in vivo to change seven conservative amino acids into alanine respectively,we named them as R192A,D216A,E409A,R424A,R502A,Y530A and E549A.Wild type (wt) and all mutant HN proteins were expressed on the cell surface of BHK-21 cells.Protein folding and processing,cell surface expression,cell fusion efficiency,receptor binding activity and neuraminidase activity were determined.Results WT and each mutant HN protein were folded and processed efficiently and expressed on the cell surface of BHK-21 cells.There was no statistic difference of cell surface expression between WT and each mutant HN protein.Cell fusion efficiency of each mutant protein decreased to some extent,especially R502A to 14.2％.7he binding guinea pig erythrocytes activity of each mutant protein was corresponding to its binding human erythrocytes activity.There was different neuraminidase activity among each mutant HN protein.R502A decreased most to 18.6％,but the neuraminidase activity of E549A was similar to that of WT hPIV3 HN (94.9％).Conclusion Conserved amino acids in the receptor-binding domain of hPIV3 HN protein play an important role in cell fusion.R502 is a key amino acid.