Delayed-onset adenosine deaminase deficiency with a novel synonymous mutation and a case series from China.

BACKGROUND: Adenosine deaminase (ADA) is a key enzyme in the purine salvage pathway. Genetic defects of the ADA gene can cause a subtype of severe combined immunodeficiency. To date, few Chinese cases have been reported. METHODS: We retrospectively reviewed the medical records of patients diagnosed with ADA deficiency in Beijing Children's Hospital and summarized the previously published ADA deficiency cases from China in the literature. RESULTS: Nine patients were identified with two novel mutations (W272X and Q202 =). Early-onset infection, thymic abnormalities and failure to thrive were the most common manifestations of Chinese ADA-deficient patients. The ADA genotype has a major effect on the clinical phenotype. Notably, a novel synonymous mutation (c.606G>A, p.Q202=) was identified in a delayed-onset patient, which affected pre-mRNA splicing leading to a frameshift and premature truncation of the protein. Furthermore, the patient showed γδT cells expansion with an increased effect or phenotype, which may be associated with the delayed onset of disease. In addition, we reported cerebral aneurysm and intracranial artery stenosis for the first time in ADA deficiency. Five patients died with a median age of four months, while two patients received stem cell transplantation and are alive. CONCLUSIONS: This study described the first case series of Chinese ADA-deficient patients. Early-onset infection, thymic abnormalities and failure to thrive were the most common manifestations in our patients. We identified a synonymous mutation that affected pre-mRNA splicing in the ADA gene, which had never been reported in ADA deficiency. Furthermore, we reported cerebral aneurysm in a delayed-onset patient for the first time. Further study is warranted to investigate the underlying mechanisms.

Respiratory syncytial virus infection induces higher Toll-like receptor-3 expression and TNF-α production than human metapneumovirus infection.

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are common causes of respiratory infections in children. Diseases caused by hMPV are generally considered to be less severe than those caused by RSV; the underlying mechanisms, however, remain unknown. In the present study, the expressions of TLRs in airway epithelial cells and lungs of BALB/c mice infected by hMPV or RSV were measured in an attempt to explore the differences in the airway inflammation caused by the two viruses. Our results demonstrate that both hMPV and RSV infection upregulated the expressions of TLRs and inflammatory cytokines. Specifically, the TLR3 expression was revealed to be elevated in vitro and in mouse lungs. IFN-α produced by A549 cells after RSV or hMPV infection remained undistinguishable, whereas production of TNF-α was significantly higher after RSV infection than hMPV infection either in the presence or absence of Poly I:C. This study provides a clue that more severe clinical syndrome of RSV infection may be due to the greater magnitude of induction of airway inflammation by RSV involving TLR3 activation and production of TNF-α.

Characterization of human metapneumoviruses isolated in Chongqing, China.

BACKGROUND: Human metapneumovirus (hMPV) has recently been recognized as a notable respiratory pathogen in children. However, no isolation processes and only a limited understanding of hMPV epidemiology present in Chinese children are documented by far. METHODS: Nasopharyngeal aspirates from 86 hospitalized children with acute respiratory tract infections from December 2004 to July 2005 were inoculated onto Vero-E6 cells for hMPV isolation. Total RNA was extracted from infected cells with a cytopathic effect and then subjected to a RT-PCR amplification of the N and F genes of the hMPV. Nucleotide sequences of amplified F gene products were examined using a variation analysis with the MegAlign program and the phylogenetic tree construction using the neighbor-joining algorithm with a Phylip package. RESULTS: Six strains of hMPV were isolated from the samples during winter, spring and summer. The most common symptoms were coughing and cyanosis, and the diagnoses were bronchiolitis, bronchopneumonia, infantile asthma, or upper respiratory tract infection. All isolates were in the A2 genetic sublineage and shared a high percentage of homology with the F gene in the nucleotide (99.8%-100%) and amino acid (99.3%-100%) sequences. CONCLUSIONS: This report indicates that hMPV is an important viral agent for acute respiratory tract infections present in Chongqing, China. Knowledge of phylogeny and genes will benefit the studies on the treatment and prophylaxis of hMPV infection.

[Isolation of human metapneumovirus from children with acute respiratory tract infection in Chongqing, China].

OBJECTIVE: To isolate and characterize the newly discovered human metapneumovirus (hMPV) in Chongqing, China and elucidate the clinical manifestations of hMPV infection. METHODS: Eighty-six patients hospitalized for acute respiratory tract infection in Children's Hospital, Chongqing University of Medical Sciences from December 2004 to July 2005 were enrolled in the present study. Nasopharyngeal aspirates were collected for screening for common respiratory viruses by direct immunofluorescence assay, including respiratory syncytial virus, influenza virus types A and B, parainfluenza virus types 1, 2, 3 and adenovirus, and for inoculating onto Vero-E6 and LLC-MK2 cells for hMPV isolation. Cultures were maintained in the presence of trypsin and observed for development of cytopathic effect (CPE) for 3 weeks. Presence of hMPV was first indicated by positive CPE and subsequently confirmed by reverse transcription polymerase chain reaction targeting N and F genes. Sequence of amplified F fragments were analyzed and submitted to NCBI GenBank. The clinical findings of hMPV infection were collected and analyzed. RESULTS: Of the collected 86 NPAs, six showed CPE characterized by clustering of infected cells, increased granules and eventuall detachment from cell monolayer and obvious syncytium formation. Successful isolation of hMPVs was confirmed with RT-PCR targeting hMPV F and N genes. Of the six hMPV-positive specimens, two were collected in winter (December, January), two in spring (May) and the other two in autumn (June, July). All the six patients were younger than 2 years of age with disease spectrum of bronchiolitis (2/6), bronchopneumonia (2/6), infantile asthma (1/6) and upper respiratory tract infection (1/6). Clinical findings included fever, cough, wheezing, polypnea, cyanosis and rales. Parainfluenza 3 and adenovirus seemed to beviral pathogens of co-infection. CONCLUSION: Six hMPVs were successfully isolated in the mainland of China for the first time. HMPV appears to be one important viral pathogen for acute lower respiratory tract infections in young children with a detection rate of 7% (6/86) by viral isolation. The virus causes respiratory diseases similar to those caused by respiratory syncytial virus. These findings highlight the need for future investigations to define disease burden of hMPV infection and molecular epidemiology among children in China.