Maternal ABO and rhesus blood group phenotypes and hepatitis B surface antigen carriage

In view of a persistently high prevalence of hepatitis B surface antigen (HBsAg) carriage in our obstetric population, we examined the association between HBsAg carriage with maternal ABO and rhesus (Rh) blood group phenotypes determined at routine antenatal screening. In a retrospective study, the antenatal screening results of women booked for confinement between 1998 and 2011 in our hospital were examined for the relationship between HBsAg carriage with the ABO and rhesus blood groups, taking into account also the effects of advanced maternal age (≥ 35 years) and parity status (nulliparous or multiparous), and year of birth before or following the availability of the hepatitis B vaccine (1984). HBsAg carriage was found in 9.9%, 9.6%, 9.1% and 10.2% (P = 0.037) for group-A (n = 20 581 or 26.1%), -B (n = 20 744 or 26.4%), -AB (n = 5138 or 6.5%) and -O (n = 32 242 or 41.0%) among the 78705 women in the study cohort. Rhesus negativity was found in 0.6%, and HBsAg carriage was 12.3% and 9.8%, respectively, for the Rh-negative and Rh-positive women (P = 0.071). Carriage rate between group-O and non-O was influenced by nulliparity, age ≥ 35 years and Rh-positive status. Regression analysis indicated that group-B (P = 0.044, aOR = 1.062, 95% CI 1.002-1.127) and group-AB (P = 0.016, aOR = 1.134, 95% CI 1.024-1.256) were associated with HBsAg carriage. Blood groups-B and -AB are associated with increased hepatitis B virus (HBV) infection in our population, and further studies are warranted to elucidate the implications of this on the sequelae of HBV infection.

Antiviral effect of a selective COX-2 inhibitor on H5N1 infection in vitro

A selective cyclooxygenase-2 (COX-2) inhibitor has been previously shown to suppress the hyper-induced pro-inflammatory responses in H5N1 infected primary human cells. Here, we demonstrate that COX-2 inhibitors suppress H5N1 virus replication in human macrophages suggesting that H5N1 virus replication (more so than seasonal H1N1 virus) is dependent on activation of COX-2 dependent signaling pathways in host cells. COX-2 and its downstream signaling pathways deserve detailed investigation as a novel therapeutic target for treatment of H5N1 disease.

Systems-level comparison of host responses induced by pandemic and seasonal influenza A H1N1 viruses in primary human type I-like alveolar epithelial cells in vitro

BACKGROUND

Pandemic influenza H1N1 (pdmH1N1) virus causes mild disease in humans but occasionally leads to severe complications and even death, especially in those who are pregnant or have underlying disease. Cytokine responses induced by pdmH1N1 viruses in vitro are comparable to other seasonal influenza viruses suggesting the cytokine dysregulation as seen in H5N1 infection is not a feature of the pdmH1N1 virus. However a comprehensive gene expression profile of pdmH1N1 in relevant primary human cells in vitro has not been reported. Type I alveolar epithelial cells are a key target cell in pdmH1N1 pneumonia.

METHODS

We carried out a comprehensive gene expression profiling using the Affymetrix microarray platform to compare the transcriptomes of primary human alveolar type I-like alveolar epithelial cells infected with pdmH1N1 or seasonal H1N1 virus.

RESULTS

Overall, we found that most of the genes that induced by the pdmH1N1 were similarly regulated in response to seasonal H1N1 infection with respect to both trend and extent of gene expression. These commonly responsive genes were largely related to the interferon (IFN) response. Expression of the type III IFN IL29 was more prominent than the type I IFN IFNβ and a similar pattern of expression of both IFN genes was seen in pdmH1N1 and seasonal H1N1 infection. Genes that were significantly down-regulated in response to seasonal H1N1 but not in response to pdmH1N1 included the zinc finger proteins and small nucleolar RNAs. Gene Ontology (GO) and pathway over-representation analysis suggested that these genes were associated with DNA binding and transcription/translation related functions.

CONCLUSIONS

Both seasonal H1N1 and pdmH1N1 trigger similar host responses including IFN-based antiviral responses and cytokine responses. Unlike the avian H5N1 virus, pdmH1N1 virus does not have an intrinsic capacity for cytokine dysregulation. The differences between pdmH1N1 and seasonal H1N1 viruses lay in the ability of seasonal H1N1 virus to down regulate zinc finger proteins and small nucleolar RNAs, which are possible viral transcriptional suppressors and eukaryotic translation initiation factors respectively. These differences may be biologically relevant and may represent better adaptation of seasonal H1N1 influenza virus to the host.

Avian influenza H5N1 virus induces cytopathy and proinflammatory cytokine responses in human astrocytic and neuronal cell lines

It has previously been reported that the avian H5N1 type of influenza A virus can be detected in neurons and astrocytes of human brains in autopsy cases. However, the underlying neuropathogenicity remains unexplored. In this study, we used differentiated human astrocytic and neuronal cell lines as models to examine the effect of H5N1 influenza A viral infection on the viral growth kinetics and immune responses of the infected cells. We found that the influenza virus receptors, sialic acid-alpha2,3-galactose and sialic acid-alpha2,6-galactose, were expressed on differentiated human astrocytic and neuronal cells. Both types of cells could be infected with H5N1 influenza A viruses, but progeny viruses were only produced from infected astrocytic cells but not neuronal cells. Moreover, increased expression of interleukin (IL)-6 and/or tumor necrosis factor alpha (TNF-alpha) mRNA was detected in both astrocytic and neuronal cells at 6 and 24 h post-infection. To examine the biological consequences of such enhanced cytokine expression, differentiated astrocytic and neuronal cells were directly treated with these two cytokines. TNF-alpha treatment induced apoptosis, as well as proinflammatory cytokine, chemokine and inflammatory responses in differentiated astrocytic and neuronal cells. Taken together, our findings reveal that avian influenza H5N1 viruses can infect human astrocytic and neuronal cells, resulting in the induction of direct cellular damage and proinflammatory cytokine cascades. Our observations suggest that avian influenza H5N1 infection can trigger profound CNS injury, which may play an important role in the influenza viral pathogenesis.

Systems-level comparison of host-responses elicited by avian H5N1 and seasonal H1N1 influenza viruses in primary human macrophages

Human disease caused by highly pathogenic avian influenza (HPAI) H5N1 can lead to a rapidly progressive viral pneumonia leading to acute respiratory distress syndrome. There is increasing evidence from clinical, animal models and in vitro data, which suggests a role for virus-induced cytokine dysregulation in contributing to the pathogenesis of human H5N1 disease. The key target cells for the virus in the lung are the alveolar epithelium and alveolar macrophages, and we have shown that, compared to seasonal human influenza viruses, equivalent infecting doses of H5N1 viruses markedly up-regulate pro-inflammatory cytokines in both primary cell types in vitro. Whether this H5N1-induced dysregulation of host responses is driven by qualitative (i.e activation of unique host pathways in response to H5N1) or quantitative differences between seasonal influenza viruses is unclear. Here we used microarrays to analyze and compare the gene expression profiles in primary human macrophages at 1, 3, and 6 h after infection with H5N1 virus or low-pathogenic seasonal influenza A (H1N1) virus. We found that host responses to both viruses are qualitatively similar with the activation of nearly identical biological processes and pathways. However, in comparison to seasonal H1N1 virus, H5N1 infection elicits a quantitatively stronger host inflammatory response including type I interferon (IFN) and tumor necrosis factor (TNF)-α genes. A network-based analysis suggests that the synergy between IFN-β and TNF-α results in an enhanced and sustained IFN and pro-inflammatory cytokine response at the early stage of viral infection that may contribute to the viral pathogenesis and this is of relevance to the design of novel therapeutic strategies for H5N1 induced respiratory disease.

Heterologous influenza vRNA segments with identical non-coding sequences stimulate viral RNA replication in trans

The initiation of transcription and replication of influenza A virus requires the 5' and 3' ends of vRNA. Here, the role of segment-specific non-coding sequences of influenza A virus on viral RNA synthesis was studied. Recombinant viruses, with the nonstructural protein (NS) segment-specific non-coding sequences replaced by the corresponding sequences of the neuraminidase (NA) segment, were characterized. The NS and NA vRNA levels in cells infected with these mutants were much higher than those of the wild type, whereas the NS and NA mRNA levels of the mutants were comparable to the wild-type levels. By contrast, the PB2 vRNA and mRNA levels of all the tested viruses were similar, indicating that vRNA with heterologous segment-specific non-coding sequences was not affected by the mutations. The observations suggested that, with the cooperation between the homologous 5' and 3'segment-specific sequences, the introduced mutations could specifically enhance the replication of NA and NS vRNA.

Biology of influenza a virus

The outbreaks of avian influenza A virus in poultry and humans over the last decade posed a pandemic threat to human. Here, we discuss the basic classification and the structure of influenza A virus. The viral genome contains eight RNA viral segments and the functions of viral proteins encoded by this genome are described. In addition, the RNA transcription and replication of this virus are reviewed.

Generation of recombinant influenza A virus without M2 ion-channel protein by introduction of a point mutation at the 5' end of the viral intron

The aim of this study was to inhibit influenza virus M2 protein expression by mutating the splicing signal of the M gene. Mutations were introduced into the GU dinucleotide sequence at the 5'-proximal splicing site of the M gene (corresponding to nt 52-53 of M cRNA). Transfected cells expressing mutated M viral ribonucleoproteins failed to generate M2 mRNA. Interestingly, recombinant viruses with mutations at the dinucleotide sequence were viable, albeit attenuated, in cell culture. These recombinants failed to express M2 mRNA and M2 protein. These observations demonstrated that the GU invariant dinucleotide sequence at the 5'-proximal splicing site of M gene is essential for M2 mRNA synthesis. These results also indicated that the M2 ion-channel protein is critical, but not essential, for virus replication in cell culture. This approach may provide a new way of producing attenuated influenza A virus.

Detection of SARS coronavirus in patients with severe acute respiratory syndrome by conventional and real-time quantitative reverse transcription-PCR assays

BACKGROUND

A novel coronavirus (CoV) was recently identified as the agent for severe acute respiratory syndrome (SARS). We compared the abilities of conventional and real-time reverse transcription-PCR (RT-PCR) assays to detect SARS CoV in clinical specimens.

METHODS

RNA samples isolated from nasopharyngeal aspirate (NPA; n = 170) and stool (n = 44) were reverse-transcribed and tested by our in-house conventional RT-PCR assay. We selected 98 NPA and 37 stool samples collected at different times after the onset of disease and tested them in a real-time quantitative RT-PCR specific for the open reading frame (ORF) 1b region of SARS CoV. Detection rates for the conventional and real-time quantitative RT-PCR assays were compared. To investigate the nature of viral RNA molecules in these clinical samples, we determined copy numbers of ORF 1b and nucleocapsid (N) gene sequences of SARS CoV.

RESULTS

The quantitative real-time RT-PCR assay was more sensitive than the conventional RT-PCR assay for detecting SARS CoV in samples collected early in the course of the disease. Real-time assays targeted at the ORF 1b region and the N gene revealed that copy numbers of ORF 1b and N gene sequences in clinical samples were similar.

CONCLUSIONS

NPA and stool samples can be used for early diagnosis of SARS. The real-time quantitative RT-PCR assay for SARS CoV is potentially useful for early detection of SARS CoV. Our results suggest that genomic RNA is the predominant viral RNA species in clinical samples.