Experimental Approach to Flu Prevention Could Block Multiple Strains

WASHINGTON, DC - JANUARY 20, 2015 - A new biologic drug prevented death when administered to mice a week in advance of lethal challenge with influenza H7N9, a disease that has shown a  roughly 30 percent mortality rate in humans. The biologic had previously proven protective in mice against the pandemic 2009 H1N1 and the highly pathogenic H5N1 influenza viruses. “This suggests that our approach could work for any strain of the influenza virus,” says corresponding author Elena Govorkova, of St. Jude Children’s Research Hospital, Memphis, Tennessee. The research is published ahead of print in Antimicrobial Agents and Chemotherapy.

Influenza viruses are notoriously mutable, making it a huge annual challenge for scientists to predict each new year’s strain, and to formulate an effective vaccine. Collaborators Garry Taylor and co-corresponding author Helen Connaris at the University of St. Andrews, United Kingdom came up with an ingenious approach to thwart influenza viruses. Rather than predicting which antibodies would work against each new strain, they developed a way of “barring the door” to the respiratory tract cells.

“Influenza viruses attach to a very specific sugar molecule that decorates all the cells that line the respiratory tract,” coauthor Robert Webster of St. Jude’s explains. “Following attachment, the virus is engulfed by the cell and then replicates therein to produce more viruses that are released to infect even more cells.” So Taylor and Connaris developed a novel engineered protein, which goes by the unwieldy moniker, Sp2CBMTD. This biologic binds to those sugar molecules, blocking the viruses from entry.

The investigators engineered Sp2CBMTD using multiple copies of a small sugar-binding section, or “domain” of a protein they isolated from Streptococcus pneumoniae, which the bacterium, a normal inhabitant of the human throat, also uses to bind to those cells.

In the study, the investigators administered the biologic nasally to mice, either as a single large dose, or repeated low doses, up to a week in advance of lethal influenza challenge. “In most cases, the mice were fully protected,” says Govorkova.

“Our findings suggest that this preventive approach could protect people during periods of flu vaccine development, particularly in the case of a pandemic, or in situations where vaccine efficacy may vary amongst specific populations groups such as the elderly, immunocompromised individuals, or those with pre-existing respiratory diseases,” says Connaris. “Several other respiratory diseases attach to the same sugar molecule as influenza virus, suggesting that our biologic has an even broader potential in preventing respiratory disease.”

Govorkova says that even after administration of the biologic, there is sufficient viral replication to stimulate an immune response, and speculates that this might provide protection against repeat infection. 

Buffer Zone Guidelines May Be Inadequate to Protect Produce From Feedlot Contamination

WASHINGTON, DC - DECEMBER 23, 2014 - The pathogen Escherichia coli O157:H7 can spread, likely airborne, more than one tenth mile downwind from a cattle feedlot onto nearby produce, according to a paper published ahead of print in Applied and Environmental Microbiology. The high percentages of leafy greens contaminated with E. coli suggest great risk for planting fresh produce 180 m [590 feet] or less from a feedlot,” the investigators write. That suggests that current buffer zone guidelines of 120 meters [400 feet] from a feedlot may be inadequate. This is the first comprehensive and long-term study of its kind, says first author Elaine D. Berry, of the U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, in Clay Center, Nebraska.
 
In the study, the investigators sampled leafy greens growing in nine plots; three each at 60, 120, and 180 meters downwind from the cattle feedlot at the research center, over a two year period. The rate of contamination with the pathogenic E. coli O157:H7 declined with distance from an average of 3.5 percent of samples per plot at 60 meters to 1.8 percent at 180 meters. 
 
The researchers sampled the produce six times between June and September of each year. They also sampled the feedlot surface manure in 10 feedlot pens for E. coli O157:H7, finding it in an average of 71.7 to 73.3 percent of samples in 2012 and 2011, respectively.  Moreover, the study’s long-term nature enabled sampling under a greater diversity of weather conditions.
 
A variety of conditions can affect the level of contamination, says Berry. For example, following a period of high cattle management activity when the feedlot was dry and dusty, including removal of around 300 head of cattle for shipping, the rate of total non-pathogenic E. coli-contaminated samples per plot at 180 meters shot up to 92.2 percent.
Conversely, total E. coli-positive leafy green samples were notably lower on one August sample date than on any other date, a finding the investigators attribute to cleaning and removal of feedlot surface manure from the nearby pens a few weeks earlier.
 
The investigators also found E. coli in air samples at 180 meters from the feedlot, though the instruments were not sensitive enough to pick up E. coli O157:H7. However, the presence of E. coli in the air samples serves as a surrogate for E. coli O157:H7, demonstrating that the pathogen may also be transmitted in this manner, says Berry. The highest levels of contamination found on leafy greens, in August and September of 2012, followed several weeks of very little rainfall and several days of high temperatures, conditions that appear to abet airborne transport of bacteria from the feedlot, she says.
 
Limitations of the research include that it was conducted only in one state—Nebraska, which is not a produce growing state. Nonetheless, Berry says that the location was a reasonable model for some of the U.S.’s major produce growing regions, such as California’s Central Coast, as winds there can blow almost as hard as in Nebraska, and both places can have dry summers, which are conducive to airborne transport of bacteria.
 
The impetus for conducting the research was the rising incidence of foodborne disease outbreaks caused by contamination of fresh produce, says Berry.

Seasonal Flu Vaccines Boost Immunity to Many Types of Flu Viruses

WASHINGTON, DC – December 9, 2014 – Seasonal flu vaccines may protect individuals not only against the strains of flu they contain but also against many additional types, according to a study published this week in mBio®, the online open-access journal of the American Society for Microbiology.
The work, directed by researchers at St. Jude Children’s Research Hospital in Memphis, Tenn., found that some study participants who reported receiving flu vaccines had a strong immune response not only against the seasonal H3N2 flu strain from 2010, when blood samples were collected for analysis, but also against flu subtypes never included in any vaccine formulation.


The finding is exciting “because it suggests that the seasonal flu vaccine boosts antibody responses and may provide some measure of protection against a new pandemic strain that could emerge from the avian population,” said senior study author Paul G. Thomas, PhD, an Associate Member in the Department of Immunology at St. Jude. “There might be a broader extent of reactions than we expected in the normal human population to some of these rare viral variants.”


Because avian influenza viruses have an important role in emerging infections, Thomas and colleagues tested whether exposure to different types of birds can elicit immune responses to avian influenza viruses in humans. They studied blood samples taken from 95 bird scientists attending the 2010 annual meeting of the American Ornithologist Union. They exposed plasma from the samples to purified proteins of avian influenza virus H3, H4, H5, H6, H7, H8 and H12 subtypes using two laboratory tests to see how many different viruses participants reacted to, and how strongly. The first test, ELISA, measures if any antibodies -- proteins produced by the body that are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses – combine in any way to a protein called HA on the surface of the virus. The second, HAI, measures if antibodies can bind to HA and interrupt its association with a substance viruses use to get inside human cells.


In the ELISA tests, 77 percent of participants had detectable antibodies against avian influenza proteins. Most individuals tested had a strong antibody response to the seasonal H3N2 human virus-derived H3 subtype, part of that year’s vaccine (2009-2010), but many also had strong measurable antibody responses to group 1 HA (avian H5, H6, H8, H12) and group 2 HA (avian H4, human H7) subtypes. Sixty-six percent of participants had some level of detectable antibodies against four or more HA proteins, and a few had responses to all subtypes tested, most of which have not previously been detected in the human population.
In additional experiments, the scientists found that participants who had significant antibody responses did not necessarily also have significant immune system T cell responses to avian viruses, indicating that these two arms of immunity can be independently boosted after vaccination or infection; that individuals who reported receiving seasonal influenza vaccination had significantly higher antibodies to the avian H4, H5, H6, and H8 subtypes; and that participants with exposure to poultry had significantly higher antibody responses to the H7 subtype, but to none of the other subtypes tested. Exposure to other types of birds did not play a role in immunity.


A person’s immune response on the ELISA test did not necessarily predict response on the HAI test, and vice versa. As HAI antibodies only target the “head” of the HA while ELISA antibodies can be against the head or the relatively conserved “stalk” domain, this result indicated that some individuals were more likely to target the conserved stalk region (i.e. show greater reactivity in ELISA than in HAI).


The work has opened up a lot of questions in figuring out why people mount different types of responses, and potentially how the seasonal vaccine may play a role in boosting these responses, Thomas said. He has started additional studies in other groups of people with varied vaccination and infection histories to tease apart what exposures boost immunity against avian influenza viruses.


The study was supported by the National Institutes of Health Centers of Excellence for Influenza Research and Surveillance (St. Jude CEIRS, contract HHSN272201400006C) and the American Lebanese Syrian Associated Charities (ALSAC), a fund-raising organization for the hospital. The article can be found online at http://bit.ly/mbiodec9.


# # #
mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online at http://mbio.asm.org.

The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.

Commensal bacteria were critical shapers of early human populations

WASHINGTON, DC—December 16, 2014—Using mathematical modeling, researchers at New York and Vanderbilt universities have shown that commensal bacteria that cause problems later in life most likely played a key role in stabilizing early human populations. The finding, published in mBio®, the online open-access journal of the American Society for Microbiology, offers an explanation as to why humans co-evolved with microbes that can cause or contribute to cancer, inflammation, and degenerative diseases of aging.

The work sprung from a fundamental question in biology about senescence, or aging past the point of reproduction.  “Nature has a central problem—it must have a way to remove old individuals, whether fish or trees or people,” says Martin Blaser, microbiologist at New York University Langone Medical Center in New York City. “Resources are always limited. And young guys are ultimately competing with older ones.”

In most species, individuals die shortly after the reproductive phase.  But humans are weird—we have an extra long senescence phase. Blaser began to think about the problem from the symbiotic microbe’s point of view and he came up with a hypothesis: “The great symbionts keep us alive when we are young, then after reproductive age, they start to kill us.” They are part of the biological clock of aging.

In other words, he hypothesized that evolution selected for microbes that keep the whole community of hosts healthy, even if that comes with a cost to an individual host’s health.

Modeling of early human population dynamics could tell him if he was on the right track. Blaser worked together with his collaborator Glenn Webb, professor of mathematics at Vanderbilt University in Nashville, to define a mathematical model of an early human population, giving it characteristics similar to a time 500-100,000 years ago, when the human population consisted of sparse, isolated communities.

Webb came up with a non-linear differential equation to describe the variables involved, their rates of change over time, and the relationship between those rates. “It can reveal something that’s not quite appreciated or intuitive, because it sorts out relationships changing in time,” even with many variables, such as age-dependent fertility rates and mortality rates, changing simultaneously, explains Webb.

Using this baseline model, the team could tweak the conditions to see what happened to the population dynamics. For example, they increased the fertility rate from roughly six children per female to a dozen, proposing that this might be one way for populations to overcome the burden of senescence, by boosting juvenile numbers. Instead, they were surprised to see that this created wild oscillations in total population size over time—an unstable scenario.

“You could imagine if something bad happens during a low point, like a drought, then the population crashes or might be extinguished,” says Blaser. Over time, the increased fertility rate adds to the pressure that a larger population of older people puts on the juveniles due to limited resources. Likewise, when Blaser and Webb plugged parameters into the model that greatly increased mortality from a microbial infection akin to Shigella, which primarily kills children, the population crashed to zero.

Next they set juvenile mortality to a constant, low level and senescent mortality risk was set to increase each year with age—a condition that mimics certain symbiotic bacteria such as Helicobacter pylori that can become harmful in old age. This model exhibited a stable population equilibrium.

“By preferentially knocking off older individuals, you get a robust population, and this is what Nature is doing,” says Blaser. Now, though, the legacy of co-evolving with such microbes has become a burden as longevity stretches out, because some of these microbes contribute to inflammatory and degenerative diseases. Recognizing that our own once-beneficial microbes might be the agents of mortality in later life, could lead to better preventives or treatments for diseases of aging.

Restrooms: Not As Unhealthy As You Might Think

WASHINGTON, DC – December 1, 2014 -- Microbial succession in a sterilized restroom begins with bacteria from the gut and the vagina, and is followed shortly by microbes from the skin. Restrooms are dominated by a stable community structure of skin and outdoor associated bacteria, with few pathogenic bacteria making them similar to other built environments such as your home. The research is published ahead of print in Applied and Environmental Microbiology.

In the study, the investigators characterized the structure, function, and abundance of the microbial community, on floors, toilet seats, and soap dispensers, following decontamination of each surface. They analyzed the surfaces hourly at first, and then daily, for up to eight weeks. “We hypothesized that while enteric bacteria would be dispersed rapidly due to toilet flushing, they would not survive long, as most are not good competitors in cold, dry, oxygen-rich environments,” says corresponding author Jack A. Gilbert of San Diego State University. “As such, we expected the skin microbes to take over—which is exactly what we found.”

“Reproduceable successional ecology is remarkable,” says Gilbert, who has conducted similar studies of the home (www.homemicrobiome.com), and the hospital (www.hospitalmicrobiome.com). “Most systems have the potential to have multiple outcomes. The restroom surfaces, though, were remarkably stable, always ending up at the same endpoint.”

Indeed, the communities associated with each surface became more similar in species and abundance within five hours following initial sterilization, and the resulting late-successional surface community structure remained stable for the remainder of the 8 weeks’ sampling. Floor communities showed a rapid reduction in abundance of Firmicutes and Bacteroidetes, while the relative abundance of Proteobacteria, Cyanobacteria, and Actinobacteria declined over the course of a day. Cyanobacteria are likely derived from dietary plant biomass or from plant material tracked in from outdoors.

Toilet seat samples, alone, clustered according to restroom gender, with Lactobacillus and Anaerococcus—vaginal flora—dominating ladies’ room toilet seats, while the gut-associated Roseburia and Blautia, were more copious on toilet seats in men’s rooms.

Ultimately, skin and outdoor-associated taxa comprised 68-98 percent of cultured communities, with fecal taxa representing just 0-15 percent of these. And out-door-associated taxa predominated in restrooms prior to sterilization, as well as in long-term post-sterilization communities, suggesting that over the long term, human-associated bacteria need to be dispersed in restrooms in order to be maintained there.

Overall, the research suggests that the restroom is no more healthy or unhealthy than your home, says Gilbert.”A key criterion of of healthy or unhealthy might be the presence or relative abundance of pathogens. While we found cassettes associated with methicillin-resistant Staphylococcus aureus (MRSA) the predominant Staph organisms didn’t harbor those genes, so MRSA may be there but it is very rare.” Restrooms, he says, are not necessarily unhealthy, but classifying them as healthy would not necessarily be accurate.

The research, he says, is very important for understanding the environmental ecology of the built environment, and will likely help in building restrooms and buildings generally that are healthier for humans.

###

Journal of Virology is a publication of the American Society for Microbiology (ASM). The ASM is the largest single life science society, composed of over 39,000 scientists and health professionals. Its mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.

TPL_asm2013_SEARCH