The pause on avian H5N1 influenza virus transmission research should be ended

A voluntary 60-day pause on avian H5N1 influenza virus transmission research was announced in January 2012 by the international community of influenza scientists engaged in this work to provide time to explain the benefits of such work and the risk mitigation measures in place. Subsequently, the pause was extended to allow for time for review of the biosafety and bios-ecurity conditions. After almost 8 months, these conditions have been met in some countries and are close to being met in others. Because H5N1 virus transmission studies are essential for pandemic preparedness, researchers who have approval from their governments and institutions to conduct this research safely under appropriate biosecurity conditions should resume this important work

Multiple reassortment events in the evolutionary history of H1N1 influenza A virus since 1918

The H1N1 subtype of influenza A virus has caused substantial morbidity and mortality in humans, first documented in the global pandemic of 1918 and continuing to the present day. Despite this disease burden, the evolutionary history of the A/H1N1 virus is not well understood, particularly whether there is a virological basis for several notable epidemics of unusual severity in the 1940s and 1950s. Using a data set of 71 representative complete genome sequences sampled between 1918 and 2006, we show that segmental reassortment has played an important role in the genomic evolution of A/H1N1 since 1918. Specifically, we demonstrate that an A/H1N1 isolate from the 1947 epidemic acquired novel PB2 and HA genes through intra-subtype reassortment, which may explain the abrupt antigenic evolution of this virus. Similarly, the 1951 influenza epidemic may also have been associated with reassortant A/H1N1 viruses. Intra-subtype reassortment therefore appears to be a more important process in the evolution and epidemiology of H1N1 influenza A virus than previously realized

Genetic characterization of H5N1 influenza viruses isolated from chickens in Indonesia in 2010

Since 2003, highly pathogenic H5N1 avian influenza viruses have caused outbreaks among poultry in Indonesia every year, producing the highest number of human victims worldwide. However, little is known about the H5N1 influenza viruses that have been circulating there in recent years. We therefore conducted surveillance studies and isolated eight H5N1 viruses from chickens. Phylogenic analysis of their hemagglutinin and neuraminidase genes revealed that all eight viruses belonged to clade 2.1.3. However, on the basis of nucleotide differences, these viruses could be divided into two groups. Other viruses genetically closely related to these two groups of viruses were all Indonesian isolates, suggesting that these new isolates have been evolving within Indonesia. Among these viruses, two distinct viruses circulated in the Kalimantan islands during the same season in 2010. Our data reveal the continued evolution of H5N1 viruses in Indonesia

Pandemic potential of highly pathogenic avian influenza clade 2.3.4.4 A(H5) viruses

The panzootic caused by A/goose/Guangdong/1/96-lineage highly pathogenic avian influenza (HPAI) A(H5) viruses has occurred in multiple waves since 1996. From 2013 onwards, clade 2.3.4.4 viruses of subtypes A(H5N2), A(H5N6), and A(H5N8) emerged to cause panzootic waves of unprecedented magnitude among avian species accompanied by severe losses to the poultry industry around the world. Clade 2.3.4.4 A(H5) viruses have expanded in distinct geographical and evolutionary pathways likely via long distance migratory bird dispersal onto several continents and by poultry trade among neighboring countries. Coupled with regional circulation, the viruses have evolved further by reassorting with local viruses. As of February 2019, there have been 23 cases of humans infected with clade 2.3.4.4 H5N6 viruses, 16 (70%) of which had fatal outcomes. To date, no HPAI A(H5) virus has caused sustainable human-to-human transmission. However, due to the lack of population immunity in humans and ongoing evolution of the virus, there is a continuing risk that clade 2.3.4.4 A(H5) viruses could cause an influenza pandemic if the ability to transmit efficiently among humans was gained. Therefore, multisectoral collaborations among the animal, environmental, and public health sectors are essential to conduct risk assessments and develop countermeasures to prevent disease and to control spread. In this article, we describe an assessment of the likelihood of clade 2.3.4.4 A(H5) viruses gaining human-to-human transmissibility and impact on human health should such human-to-human transmission occur. This structured analysis assessed properties of the virus, attributes of the human population, and ecology and epidemiology of these viruses in animal hosts

Antigenic Change in Human Influenza A(H2N2) Viruses Detected by Using Human Plasma from Aged and Younger Adult Individuals

Human influenza A(H2N2) viruses emerged in 1957 and were replaced by A(H3N2) viruses in 1968. The antigenicity of human H2N2 viruses has been tested by using ferret antisera or mouse and human monoclonal antibodies. Here, we examined the antigenicity of human H2N2 viruses by using human plasma samples obtained from 50 aged individuals who were born between 1928 and 1933 and from 33 younger adult individuals who were born after 1962. The aged individuals possessed higher neutralization titers against H2N2 viruses isolated in 1957 and 1963 than those against H2N2 viruses isolated in 1968, whereas the younger adults who were born between 1962 and 1968 possessed higher neutralization titers against H2N2 viruses isolated in 1963 than those against other H2N2 viruses. Antigenic cartography revealed the antigenic changes that occurred in human H2N2 viruses during circulation in humans for 11 years, as detected by ferret antisera. These results show that even though aged individuals were likely exposed to more recent H2N2 viruses that are antigenically distinct from the earlier H2N2 viruses, they did not possess high neutralizing antibody titers to the more recent viruses, suggesting immunological imprinting of these individuals with the first H2N2 viruses they encountered and that this immunological imprinting lasts for over 50 years

Protection from the 2009 H1N1 Pandemic Influenza by an Antibody from Combinatorial Survivor-Based Libraries

Influenza viruses elude immune responses and antiviral chemotherapeutics through genetic drift and reassortment. As a result, the development of new strategies that attack a highly conserved viral function to prevent and/or treat influenza infection is being pursued. Such novel broadly acting antiviral therapies would be less susceptible to virus escape and provide a long lasting solution to the evolving virus challenge. Here we report the in vitro and in vivo activity of a human monoclonal antibody (A06) against two isolates of the 2009 H1N1 pandemic influenza virus. This antibody, which was obtained from a combinatorial library derived from a survivor of highly pathogenic H5N1 infection, neutralizes H5N1, seasonal H1N1 and 2009 “Swine” H1N1 pandemic influenza in vitro with similar potency and is capable of preventing and treating 2009 H1N1 influenza infection in murine models of disease. These results demonstrate broad activity of the A06 antibody and its utility as an anti-influenza treatment option, even against newly evolved influenza strains to which there is limited immunity in the general population

Functional Analysis of Conserved Motifs in Influenza Virus PB1 Protein

The influenza virus RNA polymerase complex is a heterotrimer composed of the PB1, PB2, and PA subunits. PB1, the catalytic core and structural backbone of the polymerase, possesses four highly conserved amino acid motifs that are present among all viral RNA-dependent RNA polymerases. A previous study demonstrated the importance of several of these conserved amino acids in PB1 for influenza polymerase activity through mutational analysis. However, a small number of viruses isolated in nature possesses non-consensus amino acids in one of the four motifs, most of which have not been tested for their replicative ability. Here, we assessed the transcription/replication activities of 25 selected PB1 mutations found in natural isolates by using minireplicon assays in human and avian cells. Most of the mutations tested significantly reduced polymerase activity. One exception was mutation K480R, observed in several pandemic (H1N1) 2009 viruses, which slightly increased polymerase activity relative to wild-type. However, in the background of the pandemic A/California/04/2009 (H1N1) virus, this mutation did not affect virus titers in cell culture. Our results further demonstrate the functional importance of the four conserved PB1 motifs in influenza virus transcription/replication. The finding of natural isolates with non-consensus PB1 motifs that are nonfunctional in minireplicon assays suggests compensatory mutations and/or mixed infections which may have ‘rescued’ the inactive PB1 protein

Toll-like receptor pre-stimulation protects mice against lethal infection with highly pathogenic influenza viruses

<p>Abstract</p> <p>Since the beginning of the 20th century, humans have experienced four influenza pandemics, including the devastating 1918 'Spanish influenza'. Moreover, H5N1 highly pathogenic avian influenza (HPAI) viruses are currently spreading worldwide, although they are not yet efficiently transmitted among humans. While the threat of a global pandemic involving a highly pathogenic influenza virus strain looms large, our mechanisms to address such a catastrophe remain limited. Here, we show that pre-stimulation of Toll-like receptors (TLRs) 2 and 4 increased resistance against influenza viruses known to induce high pathogenicity in animal models. Our data emphasize the complexity of the host response against different influenza viruses, and suggest that TLR agonists might be utilized to protect against lethality associated with highly pathogenic influenza virus infection in humans.</p

Characterization of Oseltamivir-Resistant 2009 H1N1 Pandemic Influenza A Viruses

Influenza viruses resistant to antiviral drugs emerge frequently. Not surprisingly, the widespread treatment in many countries of patients infected with 2009 pandemic influenza A (H1N1) viruses with the neuraminidase (NA) inhibitors oseltamivir and zanamivir has led to the emergence of pandemic strains resistant to these drugs. Sporadic cases of pandemic influenza have been associated with mutant viruses possessing a histidine-to-tyrosine substitution at position 274 (H274Y) in the NA, a mutation known to be responsible for oseltamivir resistance. Here, we characterized in vitro and in vivo properties of two pairs of oseltaimivir-sensitive and -resistant (possessing the NA H274Y substitution) 2009 H1N1 pandemic viruses isolated in different parts of the world. An in vitro NA inhibition assay confirmed that the NA H274Y substitution confers oseltamivir resistance to 2009 H1N1 pandemic viruses. In mouse lungs, we found no significant difference in replication between oseltamivir-sensitive and -resistant viruses. In the lungs of mice treated with oseltamivir or even zanamivir, 2009 H1N1 pandemic viruses with the NA H274Y substitution replicated efficiently. Pathological analysis revealed that the pathogenicities of the oseltamivir-resistant viruses were comparable to those of their oseltamivir-sensitive counterparts in ferrets. Further, the oseltamivir-resistant viruses transmitted between ferrets as efficiently as their oseltamivir-sensitive counterparts. Collectively, these data indicate that oseltamivir-resistant 2009 H1N1 pandemic viruses with the NA H274Y substitution were comparable to their oseltamivir-sensitive counterparts in their pathogenicity and transmissibility in animal models. Our findings highlight the possibility that NA H274Y-possessing oseltamivir-resistant 2009 H1N1 pandemic viruses could supersede oseltamivir-sensitive viruses, as occurred with seasonal H1N1 viruses