Objective:To construct a nanoparticle vaccine displaying the prefusion F (preF) protein of respiratory syncytial virus (RSV) using the I53-50 protein nanoparticle platform, and to systematically evaluate its immunogenicity and protective efficacy.Methods:The RSV preF trimer antigen was genetically fused to I53-50A and assembled in vitro with I53-50B to form preF-I53-50 nanoparticles, theoretically displaying 20 preF antigens per particle. The structure and purity were characterized by size-exclusion chromatography, SDS-PAGE, and negative-stain electron microscopy. BALB/c mice were intramuscularly immunized with varying doses (1 μg or 5 μg) of preF antigen or an equimolar amount of preF-I53-50 nanoparticles. Humoral immunity, B-cell responses, and protective efficacy were assessed following intranasal viral challenge.Results:The preF-I53-50 nanoparticles self-assembled into spherical structures (50-60 nm in diameter) with uniformly arrayed antigens. The nanoparticle vaccine enhanced RSV-specific IgG1 and IgG2a antibody responses, promoting a Th1-biased immune profile. At equimolar preF doses, the neutralizing antibody titers induced by 1 μg and 5 μg nanoparticle formulations were 2.8-fold and 2.3-fold higher, respectively, than those elicited by preF alone ( P<0.05). Notably, even the low-dose nanoparticle group outperformed the high-dose preF group (1.6-fold increase). Viral challenge experiments demonstrated that preF-I53-50 effectively suppressed pulmonary viral replication, mitigated pathological damage, and induced stronger germinal center and memory B-cell responses, suggesting enhanced B-cell affinity maturation and long-term immune memory. Conclusion:The preF-I53-50 vaccine improves the immunogenicity and protective efficacy of RSV preF through multivalent antigen display.

Objective:To construct a nanoparticle vaccine displaying the prefusion F (preF) protein of respiratory syncytial virus (RSV) using the I53-50 protein nanoparticle platform, and to systematically evaluate its immunogenicity and protective efficacy.Methods:The RSV preF trimer antigen was genetically fused to I53-50A and assembled in vitro with I53-50B to form preF-I53-50 nanoparticles, theoretically displaying 20 preF antigens per particle. The structure and purity were characterized by size-exclusion chromatography, SDS-PAGE, and negative-stain electron microscopy. BALB/c mice were intramuscularly immunized with varying doses (1 μg or 5 μg) of preF antigen or an equimolar amount of preF-I53-50 nanoparticles. Humoral immunity, B-cell responses, and protective efficacy were assessed following intranasal viral challenge.Results:The preF-I53-50 nanoparticles self-assembled into spherical structures (50-60 nm in diameter) with uniformly arrayed antigens. The nanoparticle vaccine enhanced RSV-specific IgG1 and IgG2a antibody responses, promoting a Th1-biased immune profile. At equimolar preF doses, the neutralizing antibody titers induced by 1 μg and 5 μg nanoparticle formulations were 2.8-fold and 2.3-fold higher, respectively, than those elicited by preF alone ( P<0.05). Notably, even the low-dose nanoparticle group outperformed the high-dose preF group (1.6-fold increase). Viral challenge experiments demonstrated that preF-I53-50 effectively suppressed pulmonary viral replication, mitigated pathological damage, and induced stronger germinal center and memory B-cell responses, suggesting enhanced B-cell affinity maturation and long-term immune memory. Conclusion:The preF-I53-50 vaccine improves the immunogenicity and protective efficacy of RSV preF through multivalent antigen display.

Objective:To establish a Plaque-reduction Neutralization Test (PRNT) for the detection of neutralizing antibody titers of Human Respiratory Syncytial Virus (HRSV) and optimize the conditions for preliminary application.Methods:The CHO expression system was used to produce palivizumab monoclonal antibody (palivizumab) and the influencing factors such as cell type, cell culture duration, fixation and permeabilization protocols, and blocking agents. The reproducibility of the method was verified and its correlation was verified with conventional PRNT. Finally, the optimized PRNT assay was further used to determine neutralizing antibody titers against HRSV subtypes A and B in BALB/c mouse serum (immunized by intramuscular injection of HRSV fusion proteins).Results:Palivizumab was expressed at approximately 50 mg/L. The optimal working conditions for PRNT were as follows: culturing HEp-2 cells for 2 days, fixing with 4% (V/V) paraformaldehyde at room temperature for 15 min followed by 0.2% (V/V) Triton X-100 permeabilization for 15 minutes as the optimal fixation-permeabilization and removing the blocking step. The overall coefficient of variation (CV) for the reproducibility validation of this method was <15%, showing a good linear relationship with the conventional PRNT. The Spearman correlation coefficient r s was 0.983. This method was used to detect neutralizing antibody titers in mouse sera against HRSV subtype A strain long and subtype B strain 9320, and the fusion proteins combined with AlOH and CpG adjuvant induced the highest neutralizing antibody titers in mice. Conclusion:The HRSV neutralizing antibody assay established in this study is rapid, reproducible, high-throughput, and can be used to detect neutralizing antibodies to HRSV subtypes A and B.

Objective:To establish a Plaque-reduction Neutralization Test (PRNT) for the detection of neutralizing antibody titers of Human Respiratory Syncytial Virus (HRSV) and optimize the conditions for preliminary application.Methods:The CHO expression system was used to produce palivizumab monoclonal antibody (palivizumab) and the influencing factors such as cell type, cell culture duration, fixation and permeabilization protocols, and blocking agents. The reproducibility of the method was verified and its correlation was verified with conventional PRNT. Finally, the optimized PRNT assay was further used to determine neutralizing antibody titers against HRSV subtypes A and B in BALB/c mouse serum (immunized by intramuscular injection of HRSV fusion proteins).Results:Palivizumab was expressed at approximately 50 mg/L. The optimal working conditions for PRNT were as follows: culturing HEp-2 cells for 2 days, fixing with 4% (V/V) paraformaldehyde at room temperature for 15 min followed by 0.2% (V/V) Triton X-100 permeabilization for 15 minutes as the optimal fixation-permeabilization and removing the blocking step. The overall coefficient of variation (CV) for the reproducibility validation of this method was <15%, showing a good linear relationship with the conventional PRNT. The Spearman correlation coefficient r s was 0.983. This method was used to detect neutralizing antibody titers in mouse sera against HRSV subtype A strain long and subtype B strain 9320, and the fusion proteins combined with AlOH and CpG adjuvant induced the highest neutralizing antibody titers in mice. Conclusion:The HRSV neutralizing antibody assay established in this study is rapid, reproducible, high-throughput, and can be used to detect neutralizing antibodies to HRSV subtypes A and B.

Objective:To understand the common viral infection among the surveillance cases of fever respiratory syndrome (FRS) in nine provinces in China.Methods:The research data were obtained from nine provinces (Anhui, Beijing, Guangdong, Hebei, Hunan, Jilin, Shandong, Shaanxi and Xinjiang) in the "Infectious Disease Surveillance Technology Platform Information Management System" of the Chinese Center for Disease Control and Prevention from January 2009 to June 2021. Finally, 8 243 FRS cases with nucleic acid detection results of eight viruses [human influenza virus (HIFV), human respiratory syncytial virus (HRSV), human adenovirus (HAdV), human parainfluenza virus (HPIV), human rhinovirus (HRV), human metapneumovirus (HMPV), human coronavirus (HCoV) and human Boca virus (HBoV)] were included in the study. The χ 2 test/Fisher exact probability method was used to analyze the difference of virus detection rate in different age groups, regions and seasons. Results The M ( Q1, Q3) age of 8 243 FRS cases was 4 (1, 18) years old, and 56.56% (4 662 cases) were children under 5 years old. Males accounted for 58.1% (4 792 cases) of all cases. All cases were from outpatient/emergency department (2 043 cases) and inpatient department (6 200 cases). The virus detection rates of FRS cases from high to low were HRSV, HIFV, HPIV, HRV, HAdV, HMPV, HCoV and HBoV. Two or more viruses were detected simultaneously in 524 cases, accounting for 15.66% of virus-positive cases. The difference of the virus detection rate in different age groups was statistically significant (all P values<0.05), and the virus detection rate in children<5 years old was higher (49.96%). The positive rate of any virus in south China was higher than that in north China ( P<0.001). The virus-positive FRS cases were detected throughout the year. The detection rate of HRSV was higher in autumn and winter. The detection rate of HIFV was higher in winter. The detection rate of HMPV was higher in winter and spring. The detection rates of HPIV, HRV, HCoV and HBoV were higher in summer and autumn, while there was no significant difference in the detection rate of HAdV in different seasons. Compared with 2009-2019, the detection rate of any virus in 2020-2021 decreased from 41.37% to 37.86%. The detection rate of HIFV decreased sharply from 10.62% to 1.37%. The detection rate of HPIV decreased from 8.24% to 5.88%. The detection rate of HRV and HBoV increased from 5.43% and 1.79% to 9.67% and 3.19%, respectively. Conclusion:HRSV and HIFV infections are more common among FRS cases in nine provinces in China from 2009 to 2021, and the epidemiological characteristics of eight common respiratory viruses vary in different age groups, regions and seasons.

Objective:To evaluate the effect of synthetic CpG oligodeoxynucleotide (CpG-ODN) as adjuvant on immune response induced by inactivated human adenovirus (HAdV)-55 antigen in BALB/c mice.Methods:HAdV-55 virus QS prototype strain was purified by plaque to construct a seed bank of vaccine candidate strain. The amplified product of vaccine candidate strain was inactivated by 0.05%β-propiolactone, and purified to prepare perfect virus particle antigen. The purified HAdV-55 antigen was mixed with the same volume CPG-ODN and aluminum hydroxide adjuvant in low-dose group (0.2 mg/ml) and high-dose group (1 mg/ml), respectively, and inoculated BALB/c mice after emulsification. Meanwhile, the control group was set with PBS, and the immunization was enhanced once every 21 days. Respectively on primary immune 21 and 35 days after collecting venous blood in mice and separation of serum, serum was collected at the end of the time of separating spleen lymphocytes in mice. The levels of HAdV-55 specific IgG antibody and neutralization antibody in serum of immunized mice were observed by ELISA and micro-neutralization test, and the levels of lymphocytes secreting IL-4 and IFN-γ cytokines were detected by ELISpot.Results:No matter with or without adjuvant, along with the increase of the number of immunization and vaccination dose of inactivated HAdV-55 antigen induced BALB/c mice virus specific IgG antibody was also significantly increased. However, neutralizing antibody can reach detectable level only after enhanced immunity, and the geometric mean titer (GMT) of neutralizing antibody is between 1: 11 and 1: 23. Different adjuvants have significant effects on the immune response of mice. Low dose antigen combined with CPG-ODN and aluminum hydroxide mixed adjuvant can induce higher humoral and cellular immune responses in mice, and the levels of specific IgG antibody and neutralizing antibody are 2.2 and 1.8 times higher than those in the aluminum hydroxide adjuvant group, respectively. The number of lymphocytes secreting IFN-γ was 2.3 times that of the group immunized with aluminum hydroxide adjuvant.Conclusions:The novel CPG-ODN adjuvant significantly increased the immunogenicity of the inactivated HAdV-55 whole virus antigen in BALB/c mice and directed the cellular immune response toward Th1 type.

Objective:To understand the common viral infection among the surveillance cases of fever respiratory syndrome (FRS) in nine provinces in China.Methods:The research data were obtained from nine provinces (Anhui, Beijing, Guangdong, Hebei, Hunan, Jilin, Shandong, Shaanxi and Xinjiang) in the "Infectious Disease Surveillance Technology Platform Information Management System" of the Chinese Center for Disease Control and Prevention from January 2009 to June 2021. Finally, 8 243 FRS cases with nucleic acid detection results of eight viruses [human influenza virus (HIFV), human respiratory syncytial virus (HRSV), human adenovirus (HAdV), human parainfluenza virus (HPIV), human rhinovirus (HRV), human metapneumovirus (HMPV), human coronavirus (HCoV) and human Boca virus (HBoV)] were included in the study. The χ 2 test/Fisher exact probability method was used to analyze the difference of virus detection rate in different age groups, regions and seasons. Results The M ( Q1, Q3) age of 8 243 FRS cases was 4 (1, 18) years old, and 56.56% (4 662 cases) were children under 5 years old. Males accounted for 58.1% (4 792 cases) of all cases. All cases were from outpatient/emergency department (2 043 cases) and inpatient department (6 200 cases). The virus detection rates of FRS cases from high to low were HRSV, HIFV, HPIV, HRV, HAdV, HMPV, HCoV and HBoV. Two or more viruses were detected simultaneously in 524 cases, accounting for 15.66% of virus-positive cases. The difference of the virus detection rate in different age groups was statistically significant (all P values<0.05), and the virus detection rate in children<5 years old was higher (49.96%). The positive rate of any virus in south China was higher than that in north China ( P<0.001). The virus-positive FRS cases were detected throughout the year. The detection rate of HRSV was higher in autumn and winter. The detection rate of HIFV was higher in winter. The detection rate of HMPV was higher in winter and spring. The detection rates of HPIV, HRV, HCoV and HBoV were higher in summer and autumn, while there was no significant difference in the detection rate of HAdV in different seasons. Compared with 2009-2019, the detection rate of any virus in 2020-2021 decreased from 41.37% to 37.86%. The detection rate of HIFV decreased sharply from 10.62% to 1.37%. The detection rate of HPIV decreased from 8.24% to 5.88%. The detection rate of HRV and HBoV increased from 5.43% and 1.79% to 9.67% and 3.19%, respectively. Conclusion:HRSV and HIFV infections are more common among FRS cases in nine provinces in China from 2009 to 2021, and the epidemiological characteristics of eight common respiratory viruses vary in different age groups, regions and seasons.

Objective:The purpose of this study was to investigate the characteristics of viral pathogen spectrum and the epidemiological characteristics of each viral pathogen in hospitalized cases associated with severe acute respiratory infection (SARI) in Luohe City, Henan Province from 2017 to 2019.Methods:Based the SARI Case Surveillance Platform, SARI cases were collected in Central Hospital of Luohe City, Henan Province from November 2017 to February 2019. In the end, 783 SARI cases were included, whose throat swabs were taken within 24 h of admission, as well as their demographic characteristics, onset time, clinical characteristics and other information recorded. At the same time, viral identification was performed, and the age and time distribution of each virus were analyzed.Results:The age of 783 SARI cases shown as M ( P 25, P 75) was 3 (1, 5) years old, ranging from 1 month to 95 years old. Children under 5 years old were the majority (71.01%). The males (61.81%) were more than females (38.18%). Among the 783 SARI cases, a total of 9 kind of viruses were identified with 64.88% (508/783) of the throat swabs tested positive for at least one virus. The positive rate of influenza virus and human respiratory syncytial virus were both 20.18% (158 cases), which was the highest among all the detected respiratory virus. The co-infection rate was 15.84% (124/783), among which double infection was the most common, accounting for 85.48% (106/124) of the co-infected cases. And human respiratory syncytial virus, human rhinovirus and influenza virus were the most common pathogen in co-infection cases. Moreover, the viral positive rate was 68.71% in children aged 5 years and 63.27% in people aged 60-95 years. Influenza and human respiratory syncytial virus dominated in winter and spring, while human parainfluenza virus was the main infection in summer. Conclusion:Influenza virus and human respiratory syncytial virus were the main viruses in throat swabs of SARI cases from 2017 to 2019 in Luohe City, Henan Province. There were differences in the age and seasonal epidemiological characteristics of each virus.

Objective:The purpose of this study was to investigate the characteristics of viral pathogen spectrum and the epidemiological characteristics of each viral pathogen in hospitalized cases associated with severe acute respiratory infection (SARI) in Luohe City, Henan Province from 2017 to 2019.Methods:Based the SARI Case Surveillance Platform, SARI cases were collected in Central Hospital of Luohe City, Henan Province from November 2017 to February 2019. In the end, 783 SARI cases were included, whose throat swabs were taken within 24 h of admission, as well as their demographic characteristics, onset time, clinical characteristics and other information recorded. At the same time, viral identification was performed, and the age and time distribution of each virus were analyzed.Results:The age of 783 SARI cases shown as M ( P 25, P 75) was 3 (1, 5) years old, ranging from 1 month to 95 years old. Children under 5 years old were the majority (71.01%). The males (61.81%) were more than females (38.18%). Among the 783 SARI cases, a total of 9 kind of viruses were identified with 64.88% (508/783) of the throat swabs tested positive for at least one virus. The positive rate of influenza virus and human respiratory syncytial virus were both 20.18% (158 cases), which was the highest among all the detected respiratory virus. The co-infection rate was 15.84% (124/783), among which double infection was the most common, accounting for 85.48% (106/124) of the co-infected cases. And human respiratory syncytial virus, human rhinovirus and influenza virus were the most common pathogen in co-infection cases. Moreover, the viral positive rate was 68.71% in children aged 5 years and 63.27% in people aged 60-95 years. Influenza and human respiratory syncytial virus dominated in winter and spring, while human parainfluenza virus was the main infection in summer. Conclusion:Influenza virus and human respiratory syncytial virus were the main viruses in throat swabs of SARI cases from 2017 to 2019 in Luohe City, Henan Province. There were differences in the age and seasonal epidemiological characteristics of each virus.

Objective To establish an indirect ELISA method for detection of measles virus antibody based on the nucleoprotein of measles virus expressed in prokaryotic system selected as the coating antigen.Methods The working conditions were screened and optimized to determine the operation process of indirect ELISA.The anti-measles virus IgG antibody in 157 sera of healthy children and mothers of newborn infants was detected and compared with the commercial measles virus ELISA IgG antibody detection kit.Results The result showed that the coefficient of variation of intra and inter assay repeatability of the indirect ELISA was less than 10％.Compared with the result of the commercial kit,the total concordance rate of serum samples was 95.5％,and the sensitivity and specificity were 94.8％ and 98.3％,respectively.There was no significant difference between the two methods (x2 =0.313,P＞0.05;x2 =0.000,P＞ 0.05) in the positive rate of measles virus IgG antibody in 85 healthy children at the age of 0～ 15 years.The level of measles virus antibody detected by ELISA established in this study showed the same increasing and decreasing trend as that detected by the commercial kit in different age groups.The correlation coefficient r of the quantitative result was 0.893 (P＜ 0.001),which showed the quantitative potential of the method.Conclusions The ELISA method established in this study has good stability,high sensitivity and specificity,and there was no significant difference between the detection results of commercial kit and the ELISA method.It can be used for the seroepidemiological investigation of measles virus and the evaluation of antibody level of the population after vaccination.