[A molecular epidemiological study of respiratory syncytial virus circulating in southern Zhejiang Province, China, from 2009 to 2014]

OBJECTIVE

To find out the prevalence of respiratory syncytial virus (RSV) genotypes in southern Zhejiang Province, China, and to study the genetic characteristics of G protein from subtype A of RSV.

METHODS

The lower respiratory tract secretions of children under 5 years of age who were hospitalized for pneumonia and bronchiolitis in three hospitals in southern Zhejiang Province from July 2009 to June 2014 were collected. Direct immunofluorescence assay was used to detect RSV antigens from the collected secretions. A total of 200 samples were randomly selected from RSV-positive specimens in each prevailing year (from July of a specific year to June of the next year). RT-PCR was used to determine RSV subtypes, and the near-full length gene sequence of G protein from subtype A was amplified and sequenced to identify the genotype.

RESULTS

A total of 25 449 samples of lower respiratory tract secretions were collected from 2009 to 2014, among which 6 416 (25.21%) samples were RSV-positive. Among the 1 000 RSV-positive specimens randomly sampled, 462 strains (46.2%) were subtype A, and 538 strains (53.8%) were subtype B. Subtype A accounted for 22.5%, 74.5%, 84.5%, 19.0%, and 30.5% of the total strains in each year from 2009 to 2014. A total of 25 RSV subtype A strains were randomly sampled and sent out for bidirectional sequencing in each year, which confirmed 52 positive subtype A strains. Four genotypes of subtype A strains were obtained from the above strains, including NA1 (39 strains), NA4 (1 strain), ON1 (10 strains), and GA2 (2 strains). NA1 was the dominant genotype between 2009 and 2012, and ON1 was the only genotype of subtype A during 2013-2014. The nucleotide homology and amino acid homology between the G protein of subtype A and the prototype strain A2 were 80.7%-89.3% and 74.4%-82.6%, respectively. The nucleotide homology and amino acid homology between the isolates of subtype A were 81.5%-100% and 80.2%-100%, respectively.

CONCLUSIONS

In southern Zhejiang Province from 2009 to 2014, there was a co-circulation of RSV subtypes A and B, as well as a co-circulation of several different genotypes of RSV subtype A, which had highly variable G protein genes.

[Epidemiological characteristics of respiratory syncytial virus in hospitalized children with acute lower respiratory tract infection in Chongqing, China, from 2013 to 2018: an analysis of 2 066 cases]

OBJECTIVE

To study the detection rate, epidemic pattern, and clinical features of respiratory syncytial virus (RSV) in hospitalized children with acute lower respiratory infection (ALRI).

METHODS

Nasopharyngeal aspirates were collected from children with ALRI, aged < 2 years, who were hospitalized in Children's Hospital of Chongqing Medical University from June 2013 to May 2018. Multiplex PCR was used to detect 16 common respiratory viruses. The epidemiological characteristics of RSV were analyzed.

RESULTS

A total of 2 066 hospitalized children with ALRI were enrolled. Among the children, 1 595 (77.20%) tested positive for virus and 826 (39.98%) tested positive for RSV [410(49.6%) positive for RSV-A, 414 (50.1%) positive for RSV-B, and 2 (0.2%) positive for both RSV-A and RSV-B]. RSV-B was the main subtype detected in 2013-2014 and 2016-2017, while RSV-A was the main subtype in 2014-2015 and 2017-2018, and these two subtypes were prevalent in 2015-2016. The highest detection rate of RSV was noted in winter. RSV + human rhinovirus was the most common combination of viruses and was detected in 123 children. These children were more likely to develop wheezing than those with single RSV detected (P=0.030). A total of 298 samples were detected with single RSV, 148 were detected with RSV mixed with other viruses, 389 were detected with other viruses, and 241 were detected negative for viruses. Compared with the other viruses and negative virus groups, the single RSV group had a significantly younger age and significantly higher incidence rates of dyspnea, respiratory failure, and severe lower respiratory tract infection (P < 0.0083). The RSV-A positive group had a significantly higher proportion of boys than the RSV-B positive group (P=0.004), but there were no significant differences in clinical manifestations between the two groups.

CONCLUSIONS

In Chongqing in 2013-2018, RSV-A and RSV-B not only can predominate alternately, but also can co-circulate during a season. RSV is the major viral pathogen of hospitalized children with ALRI and can cause severe lower respiratory tract infection. There are no differences in clinical manifestations between children with RSV-A infection and those with RSV-B infection, but boys are more susceptible to RSV-A infection.

[Airway inflammation induced by Poly(I:C) stimulation in the late stage of respiratory syncytial virus infection in mice and its mechanism]

OBJECTIVE

To investigate the pathogenic mechanisms of airway inflammation and recurrent wheezing induced by recurrent respiratory virus infection after respiratory syncytial virus (RSV) infection.

METHODS

Sixty-four female BALB/c mice (aged 6-8 weeks) were randomly divided into four groups: control, RSV, Poly(I:C), and RSV+Poly(I:C) (n=16 each). The bronchoalveolar lavage fluid (BALF) was collected on the 3rd day after Poly(I:C) administration, and the total cell number and differential counts in BALF were determined. Hematoxylin-eosin staining was used to observe pulmonary pathological changes. The airway responsiveness was detected. ELISA was used to measure the levels of interferon-γ (IFN-γ), interleukin-4 (IL-4), interleukin-13 (IL-13), matrix metallopeptidase-9 (MMP-9), and tissue inhibitor of metalloproteinase-1 (TIMP-1) in BALF.

RESULTS

Compared with the other three groups, the RSV+Poly(I:C) group had significant increases in the total number of inflammatory infiltrating cells in the airway, airway responsiveness, and MMP-9 level in BALF (P<0.05). The RSV+Poly(I:C) group showed more severe pulmonary tissue injuries compared with the control and RSV groups (P<0.01). Compared with the RSV group, the RSV+Poly(I:C) group showed significant reductions in the levels of IL-4 and TIMP-1 in BALF (P<0.01).

CONCLUSIONS

Viral re-infection in the late stage of RSV infection may cause an imbalance of MMP-9/TIMP-1 expression and thus contribute to aggravated airway inflammation.

[Expression of interferon-λ1 in respiratory epithelial cells in children with human rhinovirus infection]

OBJECTIVE

To study the expression of interferon-λ1 (IFN-λ1) in respiratory epithelial cells in children with human rhinovirus (HRV) infection.

METHODS

Sputum samples and nasopharyngeal swabs were collected from the children who were hospitalized due to acute respiratory infection from February to October, 2017. Bacterial culture was performed, and nucleic acid test was performed for 11 respiratory pathogens. A total of 90 children with positive HRV alone were enrolled as the HRV infection group, and 95 children with positive respiratory syncytial virus (RSV) alone were enrolled as the RSV infection group. A total of 50 healthy children who underwent outpatient physical examination during the same period of time and had negative results for all pathogen tests were enrolled as the healthy control group. Nasopharyngeal swabs were collected from all groups, and quantitative real-time PCR was used to measure viral load and the mRNA expression of IFN-λ1.

RESULTS

In the HRV infection group, there was no significant difference in the mRNA expression of IFN-λ1 between boys and girls and across all age groups (P>0.05). In the HRV infection group, there was no correlation between the mRNA expression of IFN-λ1 and HRV load (P>0.05). The mRNA expression of IFN-λ1 in the HRV infection group was significantly higher than that in the healthy control group (P<0.05), but significantly lower than that in the RSV infection group (P<0.05).

CONCLUSIONS

HRV can induce the expression of IFN-λ1 in respiratory epithelial cells, suggesting that IFN-λ1 may play an important role in anti-HRV infection in children.

[A molecular epidemiological study of respiratory syncytial virus circulating in southern Zhejiang Province, China, from 2009 to 2014]

OBJECTIVE

To find out the prevalence of respiratory syncytial virus (RSV) genotypes in southern Zhejiang Province, China, and to study the genetic characteristics of G protein from subtype A of RSV.

METHODS

The lower respiratory tract secretions of children under 5 years of age who were hospitalized for pneumonia and bronchiolitis in three hospitals in southern Zhejiang Province from July 2009 to June 2014 were collected. Direct immunofluorescence assay was used to detect RSV antigens from the collected secretions. A total of 200 samples were randomly selected from RSV-positive specimens in each prevailing year (from July of a specific year to June of the next year). RT-PCR was used to determine RSV subtypes, and the near-full length gene sequence of G protein from subtype A was amplified and sequenced to identify the genotype.

RESULTS

A total of 25 449 samples of lower respiratory tract secretions were collected from 2009 to 2014, among which 6 416 (25.21%) samples were RSV-positive. Among the 1 000 RSV-positive specimens randomly sampled, 462 strains (46.2%) were subtype A, and 538 strains (53.8%) were subtype B. Subtype A accounted for 22.5%, 74.5%, 84.5%, 19.0%, and 30.5% of the total strains in each year from 2009 to 2014. A total of 25 RSV subtype A strains were randomly sampled and sent out for bidirectional sequencing in each year, which confirmed 52 positive subtype A strains. Four genotypes of subtype A strains were obtained from the above strains, including NA1 (39 strains), NA4 (1 strain), ON1 (10 strains), and GA2 (2 strains). NA1 was the dominant genotype between 2009 and 2012, and ON1 was the only genotype of subtype A during 2013-2014. The nucleotide homology and amino acid homology between the G protein of subtype A and the prototype strain A2 were 80.7%-89.3% and 74.4%-82.6%, respectively. The nucleotide homology and amino acid homology between the isolates of subtype A were 81.5%-100% and 80.2%-100%, respectively.

CONCLUSIONS

In southern Zhejiang Province from 2009 to 2014, there was a co-circulation of RSV subtypes A and B, as well as a co-circulation of several different genotypes of RSV subtype A, which had highly variable G protein genes.

[Epidemiological characteristics of respiratory syncytial virus in hospitalized children with acute lower respiratory tract infection in Chongqing, China, from 2013 to 2018: an analysis of 2 066 cases]

OBJECTIVE

To study the detection rate, epidemic pattern, and clinical features of respiratory syncytial virus (RSV) in hospitalized children with acute lower respiratory infection (ALRI).

METHODS

Nasopharyngeal aspirates were collected from children with ALRI, aged < 2 years, who were hospitalized in Children's Hospital of Chongqing Medical University from June 2013 to May 2018. Multiplex PCR was used to detect 16 common respiratory viruses. The epidemiological characteristics of RSV were analyzed.

RESULTS

A total of 2 066 hospitalized children with ALRI were enrolled. Among the children, 1 595 (77.20%) tested positive for virus and 826 (39.98%) tested positive for RSV [410(49.6%) positive for RSV-A, 414 (50.1%) positive for RSV-B, and 2 (0.2%) positive for both RSV-A and RSV-B]. RSV-B was the main subtype detected in 2013-2014 and 2016-2017, while RSV-A was the main subtype in 2014-2015 and 2017-2018, and these two subtypes were prevalent in 2015-2016. The highest detection rate of RSV was noted in winter. RSV + human rhinovirus was the most common combination of viruses and was detected in 123 children. These children were more likely to develop wheezing than those with single RSV detected (P=0.030). A total of 298 samples were detected with single RSV, 148 were detected with RSV mixed with other viruses, 389 were detected with other viruses, and 241 were detected negative for viruses. Compared with the other viruses and negative virus groups, the single RSV group had a significantly younger age and significantly higher incidence rates of dyspnea, respiratory failure, and severe lower respiratory tract infection (P < 0.0083). The RSV-A positive group had a significantly higher proportion of boys than the RSV-B positive group (P=0.004), but there were no significant differences in clinical manifestations between the two groups.

CONCLUSIONS

In Chongqing in 2013-2018, RSV-A and RSV-B not only can predominate alternately, but also can co-circulate during a season. RSV is the major viral pathogen of hospitalized children with ALRI and can cause severe lower respiratory tract infection. There are no differences in clinical manifestations between children with RSV-A infection and those with RSV-B infection, but boys are more susceptible to RSV-A infection.

[Effects of respiratory syncytial virus infection on epidermal growth factor receptor, tight junction association proteins and mucin in airway epithelial cells]

OBJECTIVE

To study the effects of respiratory syncytial virus (RSV) infection on epidermal growth factor receptor (EGFR), tight junction association proteins and mucin in the human airway epithelial cells.

METHODS

Human airway epithelial cells NCI-H292 were randomly treated by ultraviolet light-inactivated RSV (control group) or thawed RSV (RSV infection group). After 48 hours of treatment, the protein levels of occludin, E-cadherin, phosphorylated EGFR and EGFR in NCI-H292 cells were measured by Western blot. The distribution and expression levels of occludin and E-cadherin in NCI-H292 cells were examined by immunofluorescence technique. The expression levels of MUC5AC mRNA in NCI-H292 cells were assessed by RT-PCR.

RESULTS

The protein levels of occludin and E-cadherin were significantly reduced in the RSV infection group compared with the control group (P<0.05). The protein levels of phosphorylated EGFR and EGFR increased significantly in the RSV infection group compared with the control group (P<0.05). The MUC5AC mRNA levels also increased significantly in the RSV infection group compared with the control group (P<0.05).

CONCLUSIONS

RSV may down-regulate the tight junction association proteins and up-regulate the expression of MUC5AC in airway epithelial cells, which contributes to epithelial barrier dysfunction. EGFR phosphorylation may play an important role in regulation of airway barrier.

[Expression of interferon-λ1 in respiratory epithelial cells in children with human rhinovirus infection]

OBJECTIVE

To study the expression of interferon-λ1 (IFN-λ1) in respiratory epithelial cells in children with human rhinovirus (HRV) infection.

METHODS

Sputum samples and nasopharyngeal swabs were collected from the children who were hospitalized due to acute respiratory infection from February to October, 2017. Bacterial culture was performed, and nucleic acid test was performed for 11 respiratory pathogens. A total of 90 children with positive HRV alone were enrolled as the HRV infection group, and 95 children with positive respiratory syncytial virus (RSV) alone were enrolled as the RSV infection group. A total of 50 healthy children who underwent outpatient physical examination during the same period of time and had negative results for all pathogen tests were enrolled as the healthy control group. Nasopharyngeal swabs were collected from all groups, and quantitative real-time PCR was used to measure viral load and the mRNA expression of IFN-λ1.

RESULTS

In the HRV infection group, there was no significant difference in the mRNA expression of IFN-λ1 between boys and girls and across all age groups (P>0.05). In the HRV infection group, there was no correlation between the mRNA expression of IFN-λ1 and HRV load (P>0.05). The mRNA expression of IFN-λ1 in the HRV infection group was significantly higher than that in the healthy control group (P<0.05), but significantly lower than that in the RSV infection group (P<0.05).

CONCLUSIONS

HRV can induce the expression of IFN-λ1 in respiratory epithelial cells, suggesting that IFN-λ1 may play an important role in anti-HRV infection in children.

[Expression of interferon-λ1 in respiratory epithelial cells of children with RSV infection and its relationship with RSV load]

OBJECTIVE

To investigate the expression of IFN-λ1 in respiratory epithelial cells of children with respiratory syncytial virus (RSV) infection and its relationship with RSV load.

METHODS

The nasopharyngeal swabs were collected from the children who were hospitalized with respiratory tract infection from June 2015 to June 2016. A direct immunofluorescence assay was used to detect the antigens of seven common respiratory viruses (including RSV) in the nasopharyngeal swabs. A total of 120 children who were only RSV positive were selected as the RSV infection group. A total of 50 children who had negative results in the detection of all viral antigens were selected as the healthy control group. Fluorescence quantitative real-time PCR was used to determine the RSV load and the expression of IFN-λ1 mRNA in the nasopharyngeal swabs of children in the two groups.

RESULTS

The expression of IFN-λ1 in the RSV infection group was significantly higher than that in the healthy control group (P<0.05). The expression of IFN-λ1 was positively correlated with RSV load (r=0.56, P<0.05).

CONCLUSIONS

RSV can induce the expression of IFN-λ1 in respiratory epithelial cells, suggesting that IFN-λ1 may play an important role in anti-RSV infection.

[Expression of interferon-λ1 in respiratory epithelial cells of children with RSV infection and its relationship with RSV load]

OBJECTIVE

To investigate the expression of IFN-λ1 in respiratory epithelial cells of children with respiratory syncytial virus (RSV) infection and its relationship with RSV load.

METHODS

The nasopharyngeal swabs were collected from the children who were hospitalized with respiratory tract infection from June 2015 to June 2016. A direct immunofluorescence assay was used to detect the antigens of seven common respiratory viruses (including RSV) in the nasopharyngeal swabs. A total of 120 children who were only RSV positive were selected as the RSV infection group. A total of 50 children who had negative results in the detection of all viral antigens were selected as the healthy control group. Fluorescence quantitative real-time PCR was used to determine the RSV load and the expression of IFN-λ1 mRNA in the nasopharyngeal swabs of children in the two groups.

RESULTS

The expression of IFN-λ1 in the RSV infection group was significantly higher than that in the healthy control group (P<0.05). The expression of IFN-λ1 was positively correlated with RSV load (r=0.56, P<0.05).

CONCLUSIONS

RSV can induce the expression of IFN-λ1 in respiratory epithelial cells, suggesting that IFN-λ1 may play an important role in anti-RSV infection.