Acidic amino acids increase fusion activity in the specific fusion domain of Newcastle disease virus fusion protein.

To explore the effects of amino acids Gln and Asn within the specific fusion domain of fusion (F) protein on the specific membrane fusion in Newcastle disease virus (NDV), the mutants Q204E-Q205E and N245D were constructed in the specific fusion domain of F protein. The mutant genes were co-expressed with homologous or heterologous hemagglutinin-neuraminidase (HN) in BHK21 cells. Cell fusion functions of mutants were analyzed with Giemsa staining and reporter gene methods. Cell surface expression efficiency was analyzed with immunofluorescence assay and fluorescence-activated cell sorter analysis. Co-immunoprecipitation was performed to analyze the interaction of mutant F proteins with the homotypic HN protein. Both Q204E-Q205E and N245D mutations caused increased cell-cell fusion activity when they were co-expressed with homotypic HN protein. The mutant F proteins had slight changes in cell surface expression compared with that of wild-type F protein. The interactions of Q204E-Q205E or N245D with their homotypic HN increased significantly (P < 0.01) compared with the wild-type F protein. Neither Q204-Q205E nor N245D caused cell fusion in the presence of heterologous HN protein. Our data suggested that the residues Q204, Q205, and N245 play a critical role in the regulation of cell fusion. They may decrease the interaction of wild-type NDV F and NDV HN to suppress the fusion activity for survival of the infected host, which may enable a persistent virus infection and long-term virus reproduction and spread.

[Clinical Application of Screening Cell Combination Method in the Prediction of Red Blood Cell Alloantibody].

OBJECTIVE: To explore the clinical application of screening cell combination method in the prediction of red blood cell alloantibody, so as to provide basis for clinical diagnosis. METHODS: From October 2018 to April 2020, 9 680 samples were screened with automatic blood group instrument, 79 patients with positive alloantibodies were identified by 4 sets of screening cells from different manufacturers (referred to as combined method). At the same time, cell panel Panocell-16 was used for comparative analysis. Meanwhile, the combined method was also used to identify the antibodies of 20 samples from National Center for Clinical Laboratories external quality assessment (EQA) in China and 12 samples from WHO EQA. RESULTS: The 79 alloantibodies included anti-Mia antibody (7 cases), anti-M antibody (13 cases), anti-Lea antibody (9 cases), anti-P1 antibody (2 cases), anti-E antibody (22 cases), anti-c + E antibody (9 cases), anti-D antibody (4 cases), anti-e antibody (2 cases), anti-C + e antibody (3 cases), anti-C antibody (3 cases), anti-H antibody (1 case), anti-Fyb antibody (1 case), anti-E + M antibody (1 case), autoantibody + anti-E (2 cases). However, 7 cases of anti-Mia antibody and 1 case of anti- Lea antibody were missed in Panocell-16 identification results. The results of antibody identification in 20 samples from National Center for Clinical Laboratories EQA in China and 12 samples from WHO EQA were 100% accurate by combination method. The identification results between combined method identification and Panocell-16 identification showed no significant difference. CONCLUSION: The combined method can identify the alloantibodies of red blood cells in Chinese population. The screening cells can be used for screening of irregular antibodies without wasting reagents at the same time.