J. Virology: Genetics, Receptor Binding & Virulence (in Mice) Of Avian H10N8

Flu Virus binding to Receptor Cells – Credit CDC

 

# 9924

 

With all of the attention being given to the H7 and H5 avian flu strains this winter (see The Transmission Potential Of A(H7N9) In China & WHO: H5 Currently The Most Obvious Avian Flu Threat) it is easy to forget there are other avian subtypes on our radar as well. 

 

We’ve seen a handful of scattered H9N2 infections over the years, and even a one-off H6N1 in Taiwan in 2013. There’s a reservoir of mixed-host (avian, swine, equine, canine, etc.) H1, H2 & H3 viruses worthy of our attentions, as well.

 

But bringing up the rear are the H10 avian viruses, which have made a splash in the past few years.

 

Last fall, in Avian H10N7 Linked To Dead European Seals, we looked at the die off of thousands of harbor seals due to a combination of avian H10N7 influenza, pneumonia, and bacterial infection.  While known human infections with avian H10 viruses are limited, we’ve discussed them previously on several occasions. 

 

• In 2004, the first known human infections were reported among two Egyptian toddlers, as described in the  WHO/CDS/CSR/RMD report Avian Influenza Virus A (H10N7) Circulating among Humans in Egypt.
• And again, in 2012, in EID Journal: Human Infection With H10N7 Avian Influenza, we looked at a limited outbreak among workers with only mild symptoms at a chicken farm in Australia. 
• And perhaps most concerning, we saw three severe infections with an H10N8 virus in China last winter.

 

A little over a month ago, in TSRI: H10N8 and H6N1 Bind Poorly To Human Receptor Cells, we saw an encouraging report suggesting that neither subtype was poised to pose a serious pandemic threat, although they warned that these viruses bind differently than other avian viruses we’ve seen, and that our understanding of how these viruses mutate isn’t complete enough to warrant complacency.

 

All of which serves a prelude to a new study, published on April 8th in the Journal of Virology, that examines the genetic diversity, and behavior, of eight H10N8 viruses collected between 2009 and 2013. 

 

Worth noting:

• The genetic diversity (5 genotypes) detected among ducks and chickens
• Seven of the eight viruses replicated well in the lungs of mice
• Differences in virulence (in mice) between duck and chicken genotypes
• Dual binding to both Human (a2,6) and avian (a2,3) receptor cells, albeit with marked preference for avian receptors.
• The role that H9N2 has played in its evolution

 

The entire study, including an array of graphs and charts, is available at:

 

Genetics, receptor binding, and virulence in mice of H10N8 influenza viruses isolated from ducks and chickens in live poultry markets in China

Guohua Denga, Jianzhong Shia,  Jing Wanga, Huihui Konga,  Pengfei Cuia, Fang Zhanga,  Dan Tana, Yasuo Suzukib, Liling Liua, Yongping Jianga, Yuntao Guana and Hualan Chena⇑

ABSTRACT

We analyzed eight H10N8 viruses isolated from ducks and chickens in live poultry markets from 2009 to 2013 in China. These viruses showed distinct genetic diversity and formed five genotypes: the four duck isolates formed four different genotypes, whereas the four chicken viruses belong to a single genotype. The viruses bound to both human- and avian-type receptors, and four of the viruses caused 12.7% – 22.5% body weight loss in mice.

SUMMARY

In summary, our genetic studies indicate that the four duck viruses belong to four different genotypes, suggesting that they were introduced into ducks independently; the four chicken viruses belong to one genotype and appear to be hybrids of a duck virus and the local H9N2 viruses (Table 1).

The ability of H10N8 viruses to bind to human-type receptors facilitates their infection of humans, as occurred with the H7N9 viruses (28).

The more efficient replication in mice of the viruses isolated in Jiangxi province than the three duck viruses isolated in Hunan province suggests that the internal genes of the H9N2 viruses may have further increased the replicative ability and virulence of H10N8 viruses in mammals; of cause, the surface proteins may have also contributed to the difference of the virulence.

Although the viruses in our studies were all isolated from healthy birds, two H10 influenza viruses, A/turkey/England/384/79 and A/mandarin duck/Singapore/805/F-72/7/93, were reported to be highly pathogenic in chickens (3, 30). Therefore, it is important to continue monitoring the evolution of H10N8 influenza viruses and to evaluate their potential to cause disease in poultry and pandemics in humans.

 

As we’ve seen with the H5N1 and H7N9 viruses, H10N8 continues to evolve and the ubiquitous H9N2 virus appears to play a substantial role in its evolution.  An LPAI virus in chickens, H10N8 (like H7N9) can spread stealthily between flocks without the typical warning signs that HPAI viruses provide, making it more difficult to detect and eradicate.

 

While the general consensus is that the H10 family of avian viruses aren’t `ready for primetime’, H10N8 has already shown the ability to produce serious (even fatal) illness in humans, which elevates its profile when compared to many other less virulence avian strains.

 

Add in its growing genetic diversity, and its ability to reassort with other avian flu viruses, and H10N8 deservedly holds a second tier position on our list of avian flu viruses to watch.

A Genetic Predisposition To Severe Flu Infection

Photo Credit – CDC PHIL

 

 

# 9874

 

Influenza can produce a wide spectrum of illness, ranging from mild or even asymptomatic presentation to severe and/or life threatening disease.  

 

Often we talk about `high risk’ patients – where their age and/or co-morbidities (COPD, Asthma, pregnancy, etc. ) can sometimes lead to a greater chance of complications, but there may be other factors at work as well. 

 

As we saw in the 2009 H1N1 pandemic, with seasonal flu, and with several strains of avian flu (H5N1, H7N9), young, otherwise healthy adults can be quickly overwhelmed by their infections.

 

For a number of years researchers have been looking for a hematological or genetic marker that would help predict which patients would be most likely to experience severe influenza.

 

In 2008, in the Journal of Infectious Diseases, we saw a study that suggested there might be a heritable susceptibility to death from the influenza virus:

Evidence for a heritable predisposition to death due to influenza.

Albright FS, Orlando P, Pavia AT, Jackson GG, Cannon Albright LA.  

 

While interesting, this study didn’t provide us with a smoking gene.

 

In 2009 (see The Best Defense) we inched a bit closer, with research from Harvard Medical School and the Howard Hughes Medical Institute, that identified the IFITM3 protein as capable of inhibiting the replication of influenza, and other viruses, such as West Nile and Dengue. 

 

We revisited the IFITM3 story again in early 2012, in Luck Of The Draw, when we looked at research from the Wellcome Trust Sanger Institute, that found that people who carried a particular variant of the IFITM3 gene - (SNP rs12252-C) - were more likely to be hospitalized with severe influenza

 

In 2013, a study by Professor Peter Doherty (see PNAS: Genetic Marker & Cytokine Levels Linked To Severity Of Human H7N9 Infection) linked IFITM3 CC gene variant (aka C/C Genotype)  to hypercytokinemia (aka a `Cytokine Storm’), and severe outcomes in H7N9 infections.

 

This genetic marker– while comparatively rare in Caucasians - is far more common in Han Chinese, and may (partially) account for some of the particularly high mortality rates we’ve seen with novel influenza’s in Asia. 

 

Fast forward to yesterday, and we get a study published in Science Express that identifies yet another (rare) genetic marker -  a mutation of the IRF7 gene -  linked to a lack of interferon production which can lead to a more severe influenza infection. 

 

Published Online March 26 2015

Science DOI: 10.1126/science.aaa1578

Life-threatening influenza and impaired interferon amplification in human IRF7 deficiency

Michael J. Ciancanelli¹, Sarah X. L. Huang²,³,*, Priya Luthra⁴,*, Hannah Garner⁵,*, Yuval Itan¹, Stefano Volpi⁶,⁷, Fabien G. Lafaille¹, Céline Trouillet⁵, Mirco Schmolke⁴, Randy A. Albrecht⁴,⁸, Elisabeth Israelsson⁹, Hye Kyung Lim¹, Melina Casadio¹, Tamar Hermesh¹, Lazaro Lorenzo¹⁰,¹¹, Lawrence W. Leung⁴, Vincent Pedergnana¹⁰,¹¹, Bertrand Boisson¹, Satoshi Okada¹,¹², Capucine Picard¹,¹⁰,¹¹,¹³, Benedicte Ringuier¹⁴, Françoise Troussier¹⁵, Damien Chaussabel⁹,¹⁶,†, Laurent Abel¹,¹⁰,¹¹,†, Isabelle Pellier¹⁷,†, Luigi D. Notarangelo⁶,†, Adolfo García-Sastre⁴,⁸,¹⁸,†, Christopher F. Basler⁴,†, Frédéric Geissmann⁵,†, Shen-Ying Zhang¹,¹⁰,¹¹,†, Hans-Willem Snoeck²,³,†, Jean-Laurent Casanova¹,¹⁰,¹¹,¹⁹,²⁰,‡ 

Abstract

Severe influenza disease strikes otherwise healthy children and remains unexplained. We report compound heterozygous null mutations in IRF7, which encodes the transcription factor interferon regulatory factor 7, in an otherwise healthy child who suffered life-threatening influenza during primary infection. In response to influenza virus, the patient’s leukocytes and plasmacytoid dendritic cells produced very little type I and III interferons (IFNs). Moreover, the patient’s dermal fibroblasts and induced pluripotent stem cell (iPSC)-derived pulmonary epithelial cells produced reduced amounts of type I IFN and displayed increased influenza virus replication. These findings suggest that IRF7-dependent amplification of type I and III IFNs is required for protection against primary infection by influenza virus in humans. They also show that severe influenza may result from single-gene inborn errors of immunity.

Some excerpts from the Rockefeller University press release follow:

 

Genetic mutation helps explain why, in rare cases, flu can kill

March 26, 2015 | Science News

(Excerpts)

The researchers scrutinized blood and tissue samples from a young girl who, at the age of two-and-a-half, developed acute respiratory distress syndrome after catching the flu, and ended up fighting for her life in the hospital. Years after her ordeal, which she survived, scientists led by Jean-Laurent Casanova discovered that it could be explained by a rare mutation she carries that prevented her from producing a protein, interferon, that helps fight off the virus.

<SNIP>

Turning their attention to influenza, Michael J. Ciancanelli, a research associate and senior member of Casanova’s lab, and his colleagues sequenced all genes in the genomes of the young girl who survived her dangerous bout of the flu and her parents, looking for mutations that might explain her vulnerability. Knowing how rare her reaction to the flu was, they narrowed their search to mutations that were unique to her, then focused only on those that affected the immune system.

What emerged from their work was the finding that the girl had inherited two differently mutated copies of the gene IRF7, which encodes a protein that amplifies the production of interferon, a critical part of the body’s response to viral infections. “No other mutations could have explained her reaction to the influenza virus,” says Ciancanelli. “Each mutation is very uncommon and thus the likelihood of carrying two damaged copies of the gene is extremely rare.”

(Continue . . . )

 

In a separate press release from HHMI, in view of the likelihood that others care this or similar genetic factors, Dr. Casanova recommends that clinicians may want to consider including interferon alpha in the treatment of severe unexplained flu.

 

[ March 26, 2015 ]

Rare Genetic Mutations May Make Influenza Life-Threatening for Some

Summary

HHMI researchers identify a rare genetic mutation that tamps down immune response to influenza.

Highlights

• Why did the flu develop into a life-threatening infection in a two-year-old girl?
• HHMI researchers tried to identify the cause of the girl's severe response to influenza infection.
• They found that the girl carries a genetic mutation that affects production of natural antiviral molecules.

(Continue . . . )

PNAS: Immune Response To H7N9 Varies Across Ethnicities

 

# 8135

 

The 1918 H1N1 pandemic – which is estimated to have killed roughly 2% of those infected in Europe and North America – wreaked far greater havoc in other regions of the world, and proved absolutely devastating among some remote indigenous populations.

 

In the 2012 EID Journal article Differential Mortality Rates by Ethnicity in 3 Influenza Pandemics Over a Century, New Zealand, the authors from the University of Otago in Wellington, New Zealand  wrote:

 

Evidence suggests that indigenous populations have suffered disproportionately from past influenza pandemics. To examine any such patterns for Māori in New Zealand, we searched the literature and performed new analyses by using additional datasets. The Māori death rate in the 1918 pandemic (4,230/100,000 population) was 7.3× the European rate. In the 1957 pandemic, the Māori death rate (40/100,000) was 6.2× the European rate.

In the 2009 pandemic, the Māori rate was higher than the European rate (rate ratio 2.6, 95% confidence interval 1.3–5.3). These findings suggest some decline in pandemic-related ethnic inequalities in death rates over the past century. Nevertheless, the persistent excess in adverse outcomes for Māori, and for Pacific persons residing in New Zealand, highlights the need for improved public health responses.

 

From the HHS sponsored 1918 pandemic documentary We Heard The Bells, we get this account of the impact among native Americans in Alaska and the American Southwest.

NARRATOR:

There were few communities in the U.S. so small or isolated that they were sheltered from the waves of deadly disease that swept around the world.  The influenza of 1918 even touched remote Inuit villages in Alaska, sometimes killing every man, woman, and child…or killing the adults and leaving the children with no one to care for them.  The 1918 influenza struck some native peoples in the Southwest very hard, too.

 

And in 2011, in Study: Urban vs Rural Mortality From Spanish Flu, we looked at a Norwegian study that found the mortality rate in 1918 varied nearly 100 fold between remote, rural regions and urban populations, and that in the more remote areas, older persons were just as susceptible to the virus as those who were younger.

 

All of which serves a prelude to a new study appearing in PNAS, that looks at the vulnerability of some indigenous peoples to pandemic flu (specifically H7N9), and finds their innate immune response is not as finely tuned to fighting off influenza as people of Caucasian extraction.

 

While most of the world’s population lacks specific antibodies against H7N9 due to lack of previous exposure, and are assumed to be highly susceptible to infection, our innate immune system has a number of tools to help fight off infections once we acquire them.

• phagocytic cells (neutrophils, monocytes, and macrophages);
• cells that release inflammatory mediators (basophils, mast cells, and eosinophils);
• natural killer cells (NK cells); and
• molecules such as complement proteins, acute phase proteins, and cytokines.

In other words, our innate immune system throws just about everything but the kitchen sink at an unknown infection, and CD8+ T-Cells are part of that generic defense system.  But, as the study below indicates, the ability to mount this particular defense varies among different ethnicities.

 

Preexisting CD8+ T-cell immunity to the H7N9 influenza A virus varies across ethnicities

Sergio Quiñones-Parra^a, Emma Grant^a, Liyen Loh^a, Thi H. O. Nguyen^a,^b, Kristy-Anne Campbell^c, Steven Y. C. Tong^d, Adrian Miller^e, Peter C. Doherty^a,^f,¹, Dhanasekaran Vijaykrishna^g, Jamie Rossjohn^c,^h, Stephanie Gras^c, and Katherine Kedzierska^a,¹

^Significance

The severity of the novel H7N9 influenza A virus (IAV) and the lack of neutralizing antibodies raise real pandemic concerns. In this scenario, CD8⁺ T lymphocytes (CTLs) may provide a layer of protection against the H7N9 virus. Our study dissects the extent of preexisting CTL immunity with the potential to respond to H7N9.

We identified conserved immunogenic peptides with the capacity to elicit robust CTL responses against any human IAV, including the H7N9 virus, as well as the mutations that abolish CTL recognition. The human leukocyte antigen class I molecules that present these peptides vary in prevalence depending on the ethnicity. Such analyses found that the Alaskan and Australian Indigenous people may be particularly vulnerable to the H7N9 influenza disease.

 

For more on this, we turn to a feature in The Australian, with an interview one of the authors, Dr. Peter Doherty.

Aborigines 'most vulnerable' to bird flu strain

EUROPEANS may have better immune defences than other ethnic groups when facing the latest potential pandemic bird flu from China.

A study published today in the journal PNAS suggests Aborigines and other indigenous groups with a history of isolation may be most at risk if the bird flu H7N9 begins to spread widely among humans.

And Europeans may be best placed to survive any pandemic because of a long history of exposure to influenza viruses.

"There's a genetics of resistance that has evolved in western populations, we think," said Nobel prize winner Peter Doherty, whose Melbourne University colleague Katherine Kedzierska led the research team.

(Continue . . . )

 

Professor Doherty ranks Europeans, followed by Asians and Africans, as having the most developed innate flu response, and Australian Aborigines and indigenous Alaskans as having the least.

You may recall that last month I featured a study by Professor Doherty (see PNAS: Genetic Marker & Cytokine Levels Linked To Severity Of Human H7N9 Infection) that linked a specific genetic marker; IFITM3 CC gene variant (aka C/C Genotype)  to hypercytokinemia (aka a `Cytokine Storm’), and a severe outcome, in H7N9 infections.

 

This genetic marker– while relatively rare in Caucasians - is much more common in Han Chinese.

 

While the variant C/C genotype was over represented among seriously ill patients (compared to its prevalence in the local population), and the C/C genotype was also linked to more rapid disease progression than with the others, that severe disease was also seen with other genotypes.

 

So it doesn’t mean that if you have one of the other genotypes, you are guaranteed an easy time of it.  But your odds of a bad outcome appear to go up with the C/C genotype.

 

All of which illustrates that there are probably a number of variables – some we know about, and others we have yet to discover – that help explain why pandemic influenza varies in intensity around the globe. 

Researchers Discover New Flu Gene

 

# 6409

 

A reoccurring theme in this blog is just how much we have yet to learn about how our immune systems, influenza viruses, and other pathogens function.

 

Illustrative of this fact is the surprise announcement yesterday that researchers at Universities of Cambridge, Cork, Edinburgh and Utah, the Institute of Systems Biology in Seattle and the NIH have discovered a previously unknown gene hidden inside the influenza virus genome.

 

Dubbed PA-X, this gene (when active) helps attenuates the virulence of the virus. When this gene does not function properly, the flu virus can over stimulate the immune system, making the infection worse.

 

This discovery appears in a research article published yesterday by Science.

 

An Overlapping Protein-Coding Region in Influenza A Virus Segment 3 Modulates the Host Response

B. W. Jagger, H. M. Wise,J. C. Kash, K.-A. Walters, N. M. Wills, Y.-L. Xiao, R. L. Dunfee, L. M. Schwartzman, A. Ozinsky, G. L. Bell, R. M. Dalton, A. Lo, S. Efstathiou, J. F. Atkins, A. E. Firth, J. K. Taubenberger, P. Digard

 

While a short press release from the University of Edinburgh is available (see Gene discovery helps explain how flu can cause severe infections), Ed Yong’s Blog at Discover Magazine provides some of the best analysis of this research that I’ve seen. 

 

At this point, I will step aside and invite you to read Ed’s excellent article:

 

New flu gene found hiding in plain sight, and affects severity of infections

Ed Yong – Not Exactly Rocket Science

Luck Of The Draw

 

 

Photo Credit – CDC PHIL

 

# 6242

 

 

While it may seem curious to some, your humble flu blogger here at AFD has never – to his knowledge – ever suffered from a `classic’ bout of flu.

 

Oh, sure. I’ve had plenty of respiratory infections, albeit mostly upper respiratory. And a couple of times I’ve had what I’ve thought was probably influenza.

 

But I’ve never had the running fever, crushing body-aches, want-to-die kind of flu that many others seem to report.

 

I could just be lucky, I guess. 

 

But I’ve always figured I really wasn’t very susceptible to influenza. That when I’d had the flu, they had been relatively mild cases.  

 

Of course, I have no way of proving that . . .

 

But new research published in Nature by Wellcome Trust Sanger Institute lends credence to the idea that some people are genetically more likely to experience severe flu symptoms than others.

 

First some excerpts from the press release (worth reading in its entirety), then a link to the research article, then I’ll return with some other data suggestive of a genetic susceptibility to influenza.

 

Genetics of flu susceptibility

Researchers find gene that can transform mild influenza to a life-threatening disease

A genetic finding could help explain why influenza becomes a life-threating disease to some people while it has only mild effects in others. New research led by the Wellcome Trust Sanger Institute has identified for the first time a human gene that influences how we respond to influenza infection.

 

People who carry a particular variant of a gene called IFITM3 are significantly more likely to be hospitalised when they fall ill with influenza than those who carry other variants, the team found. This gene plays a critical role in protecting the body against infection with influenza and a rare version of it appears to make people more susceptible to severe forms of the disease. The results are published in the journal Nature.

 

A central question about viruses is why some people suffer badly from an infection and others do not. IFITM3 is an important protein that protects cells against virus infection and is thought to play a critical role in the immune system's response against such viruses as H1N1 pandemic influenza, commonly known as 'swine flu'. When the protein is present in large quantities, the spread of the virus in lungs is hindered, but if the protein is defective or absent, the virus can spread more easily, causing severe disease.

(Continue . . . )

 

IFITM3 restricts the morbidity and mortality associated with influenza

Aaron R. Everitt,Simon Clare,Thomas Pertel,Sinu P. John,Rachael S. Wash,Sarah E. Smith,Christopher R. Chin,Eric M. Feeley,Jennifer S. Sims,David J. Adams,Helen M. Wise,Leanne Kane,David Goulding,Paul Digard,Verneri Anttila,J. Kenneth Baillie,Tim S. Walsh,David A. Hume,Aarno Palotie,Yali Xue,Vincenza Colonna,Chris Tyler-Smith,Jake Dunning,Stephen B. Gordon,The GenISIS Investigators.et al.

Nature (2012)  doi:10.1038/nature10921

 

 

Although this research is the first to identify a specific gene that may make influenza a much more serious illness in some people than others, for some time there’s been evidence suggesting that heritable factors influence how people react to influenza.

 

In 2008, in the Journal of Infectious Diseases, we saw a study that suggested there might be a heritable susceptibility to death from the influenza virus.

 

Evidence for a heritable predisposition to death due to influenza.

Albright FS, Orlando P, Pavia AT, Jackson GG, Cannon Albright LA.

Abstract (extract)

Evidence for a heritable contribution to death due to influenza was examined using a resource consisting of a genealogy of the Utah population linked to death certificates in Utah over a period of 100 years. The relative risks of death due to influenza were estimated for the relatives of 4,855 individuals who died of influenza.

 

Both close and distant relatives of individuals who died of influenza were shown to have a significantly increased risk of dying of influenza, consistent with a combination of shared exposure and genetic effects. These data provide strong support for a heritable contribution to predisposition to death due to influenza.

 

While interesting, this study doesn’t provide us with a smoking gene.

 

However, the following year a PLoS ONE  research article doi:10.1371/journal. pone.0004857)  came a bit closer.  

 

Entitled Host Genetic Background Strongly Influences the Response to Influenza A Virus Infections by Srivastava B, Błażejewska P, Heßmann M, Bruder D, Geffers R, et al., it reports on the results of experiments utilizing seven inbred strains of lab mice that were exposed to influenza A viruses.

 

From the abstract:

 

The genetic make-up of the host has a major influence on its response to combat pathogens. For influenza A virus, several single gene mutations have been described which contribute to survival, the immune response and clearance of the pathogen by the host organism.

 

Granted, mouse models are often useful, but what happens in mice doesn’t always correspond to what happens with human physiology.

 

And last year, in Host Genetic Susceptibility to Avian Influenza, we saw an analysis of clusters of H5N1 infection in Indonesia that found that young age (under 30) and being a blood relative to the index case in a cluster, were both found to significantly increase the odds of catching the virus.

 

So there is anecdotal reason to believe that there may be genetic factors involved in either mitigating, or exacerbating, the effects of flu.

 

Never having suffered a `classic’ bout of flu admittedly gives me some hope that I might have some degree of built-in immunity to a pandemic virus.

 

But with an emerging or novel flu strain, who knows?

 

Of course, my good flu fortune may have more to do with my diligence in getting a seasonal flu shot every year, than with any genetic advantage.

 

But I can hope.