Possible Transmission of Pandemic (HIN1) 2009 Virus with Oseltamivir Resistance

To the Editor: In March 2009, a new strain of influenza A (H1N1) virus of swine origin emerged; the virus had crossed the species barrier to humans and acquired the capability of human-to-human transmission. Soon after, the World Health Organization raised the worldwide pandemic alert to level 6 (www.who.int/en), declaring the first influenza pandemic in the past 42 years. The virus was named influenza A pandemic (H1N1) 2009 virus. The illness caused by this virus is particularly dangerous for pregnant women and for patients with chronic diseases (1). The preferred treatment is a neuraminidase inhibitor, zanamivir or oseltamivir (2). Around the world, several dozen cases of resistance to oseltamivir in persons with or without exposure to the drug have been reported (3). However, only limited information is available with regard to initial infections with oseltamivir-resistant viruses (4). We report a case of possible human-to-human transmission of pandemic (H1N1) 2009 virus in Israel. After the recent discovery of oseltamivir-resistant strains, we conducted a retrospective study of oseltamivir-resistance mutations in viral RNA amplified from specimens from patients hospitalized>1 week with pandemic (H1N1) 2009. All samples were first tested for the H275Y mutation by using an in-house real-time reverse transcription–PCR (RT-PCR) assay developed a

Increase Human Metapneumovirus Mediated Morbidity following Pandemic Influenza Infection

Human metapneumovirus (hMPV) is a recently discovered respiratory pathogen, infecting mainly young children. The infected patients suffer from influenza like symptoms (ILS). In Israel the virus is mainly circulating in February to March. Here we report on an increased rate of hMPV infection in the winter season of 2009–10. The 2009–10 infection had several unique characteristics when compared to previous seasons; it started around January and a large number of infants were infected by the virus. Genetic analysis based on the viral L and F genes of hMPV showed that only subtypes A2 and B2 circulated in Israel. Additionally, we have identified a novel variant of hMPV within subgroup A2b, which subdivide it into A2b1 and A2b2. Finally, we showed that the hMPV infection was detected in the country soon after the infection with the pandemic influenza virus had declined, that infection with the pandemic influenza virus was dominant and that it interfered with the infection of other respiratory viruses. Thus, we suggest that the unusual increase in hMPV infection observed in 2009–10 was due to the appearance of the pandemic influenza virus in the winter season prior to 2009–10

Elucidating the Mechanisms of Influenza Virus Recognition by Ncr1

Natural killer (NK) cells are innate cytotoxic lymphocytes that specialize in the defense against viral infection and oncogenic transformation. Their action is tightly regulated by signals derived from inhibitory and activating receptors; the later include proteins such as the Natural Cytotoxicity Receptors (NCRs: NKp46, NKp44 and NKp30). Among the NCRs, NKp46 is the only receptor that has a mouse orthologue named Ncr1. NKp46/Ncr1 is also a unique marker expressed on NK and on Lymphoid tissue inducer (LTI) cells and it was implicated in the control of various viral infections, cancer and diabetes. We have previously shown that human NKp46 recognizes viral hemagglutinin (HA) in a sialic acid-dependent manner and that the O-glycosylation is essential for the NKp46 binding to viral HA. Here we studied the molecular interactions between Ncr1 and influenza viruses. We show that Ncr1 recognizes influenza virus in a sialic acid dependent manner and that N-glycosylation is important for this binding. Surprisingly we demonstrate that none of the predicted N-glycosilated residues of Ncr1 are essential for its binding to influenza virus and we thus conclude that other, yet unidentified N-glycosilated residues are responsible for its recognition. We have demonstrated that N glycosylation play little role in the recognition of mouse tumor cell lines and also showed the in-vivo importance of Ncr1 in the control of influenza virus infection by infecting C57BL/6 and BALB/c mice knockout for Ncr1 with influenza

Identification of new hMPV subtype.

<p>The figure shoe a phylogenetic tree that was constructed based on the nucleotide sequences (111 bp) of the Fusion gene (F protein).</p

A large number of infants were infected with hMPV in 2009–10.

<p>The figure shows the percentages of the age distribution of the hMPV positive cases diagnosed at the Central Virology Laboratory between November 2007 and May 2010.</p

The hMPV infection in 2009–10 is observed early than usual.

<p>Precent of hMPV infected patients throughout the year. The figure shows themonthly distribution of hMPV positive cases diagnosed at the Central Virology Laboratory between November 2007 and May 2010.</p

Percent of Hospitalized hMPV patients in Israel.

<p>Percent of patients positive for hMPV infections out of patients diagnosed for respiratory virus infections. The patients were hospitalized in the Sheba Medical Center, Israel, and three winter seasons 2007–10 are presented.</p

Respiratory viruses circulating in the country during the study period.

<p>The figure depicts percentages of patients hospitalized due to influenza-like symptoms that were found positive for infection with either influenza (A and B), with pandemic influenza (H1N1s) and hMPV between 2007–2010.</p

Neuraminidase-Mediated, NKp46-Dependent Immune-Evasion Mechanism of Influenza Viruses

Natural killer (NK) cells play an essential role in the defense against influenza virus, one of the deadliest respiratory viruses known today. The NKp46 receptor, expressed by NK cells, is critical for controlling influenza infections, as influenza-virus-infected cells are eliminated through the recognition of the viral hemagglutinin (HA) protein by NKp46. Here, we describe an immune-evasion mechanism of influenza viruses that is mediated by the neuraminidase (NA) protein. By using various NA blockers, we show that NA removes sialic acid residues from NKp46 and that this leads to reduced recognition of HA. Furthermore, we provide in vivo and in vitro evidence for the existence of this NA-mediated, NKp46-dependent immune-evasion mechanism and demonstrate that NA inhibitors, which are commonly used for the treatment of influenza infections, are useful not only as blockers of virus budding but also as boosters of NKp46 recognition

Killing of Avian and Swine Influenza Virus by Natural Killer Cells▿

Today, global attention is focused on two influenza virus strains: the current pandemic strain, swine origin influenza virus (H1N1-2009), and the highly pathogenic avian influenza virus, H5N1. At present, the infection caused by the H1N1-2009 is moderate, with mortality rates of less <1%. In contrast, infection with the H5N1 virus resulted in high mortality rates, and ca. 60% of the infected patients succumb to the infection. Thus, one of the world greatest concerns is that the H5N1 virus will evolve to allow an efficient human infection and human-to-human transmission. Natural killer (NK) cells are one of the innate immune components playing an important role in fighting against influenza viruses. One of the major NK activating receptors involved in NK cell cytotoxicity is NKp46. We previously demonstrated that NKp46 recognizes the hemagglutinin proteins of B and A influenza virus strains. Whether NKp46 could also interact with H1N1-2009 virus or with the avian influenza virus is still unknown. We analyzed the immunological properties of both the avian and the H1N1-2009 influenza viruses. We show that NKp46 recognizes the hemagglutinins of H1N1-2009 and H5 and that this recognition leads to virus killing both in vitro and in vivo. However, importantly, while the swine H1-NKp46 interactions lead to the direct killing of the infected cells, the H5-NKp46 interactions were unable to elicit direct killing, probably because the NKp46 binding sites for these two viruses are different