Characterization in vitro and in vivo of pandemic (H1N1) 2009 influenza viruses isolated from patients.

The first influenza pandemic of the 21st century was caused by novel H1N1 viruses that emerged in early 2009. Molecular evolutionary analyses of the 2009 pandemic influenza A H1N1 [A(H1N1)pdm09] virus revealed two major clusters, cluster I and cluster II. Although the pathogenicity of viruses belonging to cluster I, which became extinct by the end of 2009, has been examined in a nonhuman primate model, the pathogenic potential of viruses belonging to cluster II, which has spread more widely in the world, has not been studied in this animal model. Here, we characterized two Norwegian isolates belonging to cluster II, namely, A/Norway/3568/2009 (Norway3568) and A/Norway/3487-2/2009 (Norway3487), which caused distinct clinical symptoms, despite their genetic similarity. We observed more efficient replication in cultured cells and delayed virus clearance from ferret respiratory organs for Norway3487 virus, which was isolated from a severe case, compared with the efficiency of replication and time of clearance of Norway3568 virus, which was isolated from a mild case. Moreover, Norway3487 virus to some extent caused more severe lung damage in nonhuman primates than did Norway3568 virus. Our data suggest that the distinct replicative and pathogenic potentials of these two viruses may result from differences in their biological properties (e.g., the receptor-binding specificity of hemagglutinin and viral polymerase activity).

Rituximab blocks protective serologic response to influenza A (H1N1) 2009 vaccination in lymphoma patients during or within 6 months after treatment.

Cancer patients are often encouraged to receive seasonal influenza vaccination. The monoclonal antibody rituximab is widely used in treatment of non-Hodgkin lymphoma. This results in a prolonged depletion of normal B cells, which might impair humoral responses. The aim of the present study was to investigate whether lymphoma patients undergoing rituximab-containing treatment regimens or having received such regimens within the past 6 months were able to mount protective antibody responses to the influenza A(H1N1) 2009 virus vaccine Pandemrix during the 2009 "swine flu" pandemic. Contrary to the control group, where 82% responded adequately to the vaccine, none of the 67 patients achieved protective antibody titers, suggesting that lymphoma patients receiving rituximab-containing regimens might not benefit from this vaccine. It is important that doctors who care for such patients are aware that they may fail to respond not only to the influenza vaccine, but also to other common vaccines.

Avian-type receptor-binding ability can increase influenza virus pathogenicity in macaques.

The first influenza pandemic of the 21st century was caused by novel H1N1 viruses that emerged in early 2009. An Asp-to-Gly change at position 222 of the receptor-binding protein hemagglutinin (HA) correlates with more-severe infections in humans. The amino acid at position 222 of HA contributes to receptor-binding specificity with Asp (typically found in human influenza viruses) and Gly (typically found in avian and classic H1N1 swine influenza viruses), conferring binding to human- and avian-type receptors, respectively. Here, we asked whether binding to avian-type receptors enhances influenza virus pathogenicity. We tested two 2009 pandemic H1N1 viruses possessing HA-222G (isolated from severe cases) and two viruses that possessed HA-222D. In glycan arrays, viruses possessing HA-222D preferentially bound to human-type receptors, while those encoding HA-222G bound to both avian- and human-type receptors. This difference in receptor binding correlated with efficient infection of viruses possessing HA-222G, compared to those possessing HA-222D, in human lung tissue, including alveolar type II pneumocytes, which express avian-type receptors. In a nonhuman primate model, infection with one of the viruses possessing HA-222G caused lung damage more severe than did infection with a virus encoding HA-222D, although these pathological differences were not observed for the other virus pair with either HA-222G or HA-222D. These data demonstrate that the acquisition of avian-type receptor-binding specificity may result in more-efficient infection of human alveolar type II pneumocytes and thus more-severe lung damage. Collectively, these findings suggest a new mechanism by which influenza viruses may become more pathogenic in mammals, including humans.

Kallikrein 4 is a proliferative factor that is overexpressed in prostate cancer.

Kallikrein 4 (KLK4) is a member of the human tissue KLK family. Whereas all other KLKs are secreted proteins with extracellular functions, KLK4 is primarily localized to the nucleus, indicating that it has a different function compared with other members of the KLK family. In addition, KLK4 expression is highly enriched in the prostate and is regulated by androgens. Here, we studied the possible functional role of KLK4 in prostate cancer cells and examined its expression at the protein level in prostate cancer specimens. Consistent with its mRNA expression, KLK4 protein is significantly overexpressed in malignant prostate compared with normal prostate. KLK4 expression is predominantly in the nucleus of basal cells in the prostate epithelium in keeping with its distribution in prostate cancer cells in vitro. Furthermore, adenovirus-mediated expression of KLK4 dramatically induces proliferation of prostate cancer cells, at least in part through significant alterations in cell cycle regulatory gene expression. Consistent with these data, small interfering RNA-mediated knockdown of endogenous KLK4 in LNCaP prostate cancer cells inhibits cell growth. These data identify KLK4 as the first member of the KLK family that is a proliferative factor with effects on gene expression and indicate that it may have an important role in prostate cancer development and progression.

Swine influenza in Norway: a distinct lineage of influenza A(H1N1)pdm09 virus.

BACKGROUND: Since the influenza A(H1N1)pdm09 virus was first introduced to the Norwegian pig population in September 2009, it has repeatedly been detected in pigs in Norway. No other subtypes of influenza virus are circulating in Norwegian pigs. OBJECTIVE: To follow the diversity of A(H1N1)pdm09 viruses circulating in pigs in Norway and to investigate the relationship between viruses circulating in Norwegian pigs and in humans. METHODS: Between January 2011 and January 2013, nasal swabs from 507 pigs were tested for A(H1N1)pdm09 virus by real-time RT-PCR. The hemagglutinin (HA) gene of virus-positive samples was sequenced and compared with publically available sequences from viruses circulating in humans at the time. RESULTS: Sequencing and phylogenetic analysis of the HA gene showed that the A(H1N1)pdm09 virus circulating in Norwegian pigs early in 2011 resembled the A(H1N1)pdm09 virus circulating in humans during this time. Viruses detected in pigs by the end of 2011 had acquired four characteristic amino acid substitutions (N31D, S84I S164F, and N473D) and formed a distinct phylogenetic group. CONCLUSIONS: A(H1N1)pdm09 virus detected in Norwegian pigs by the end of 2011 formed a distinct genetic lineage. Also, our findings indicate that reverse-zoonotic transmission from humans to pigs of the A(H1N1)pdm09 virus is still important.

Human cytomegalovirus infection increases mitochondrial biogenesis.

Fibroblasts infected by Human Cytomegalovirus (CMV) undergo a robust increase in mitochondrial biogenesis with a corresponding increase in mitochondrial activity that is partly dependent on the viral anti-apoptotic pUL37x1 protein (vMIA). The increased respiration activity is blocked by the mitochondrial translation inhibitor chloramphenicol, which additionally suppresses viral production. Intriguingly, chloramphenicol and pUL37x1 depletion have different effects on respiration capacity but similar effects on CMV production, suggesting that pUL37x1 promotes viral replication by efficient utilization of new mitochondria. These results argue for a role of pUL37x1 beyond controlling apoptosis.