Tag Archives: immunity

The United States slides towards measles epidemics (again) because people don’t vaccinate

Non-medical vaccination exemptions and wide misinformation on their efficiency are pulling America back into endemic measles outbreaks, a paper reports.

Back of female with measles.

Back of female with measles.
Image credits Wellcome Trust.

The US took great pains (in the form of strict, nationwide vaccination campaigns) to eliminate measles back in 2000. Luckily, these efforts proved fruitful. Outbreaks did spring up here and there, mostly from people who travel to and from other countries, but they numbered a few dozens, upwards to a few hundred cases yearly. Which is a really small number. Overall, however, the measles virus was considered to no longer be endemic (present in the country) since the turn of the millennia.

But rejoice not! The US is slowly inching back to pre-2000 days, when the measles virus roamed free and deadly, researchers from the Stanford and Baylor College of Medicine warn. At the heart of the issue are non-medical vaccine exemptions and non-medical delays, coupled with wide public misinformation about vaccines.

A high toll

The two researchers, Nathan Lo, Bs. and Dr. Peter Hotez, MD., PhD., report that a 5% decrease in measles-mumps-and-rubella (MMR) vaccination rates among kids aged 2-11 would triple measles cases in the age group and end up draining the public health system some $2.1 million in additional costs. But wait, it gets even better/worse — ages 2-11 make up only about a third of measles cases in current outbreaks, but it was the only age interval the researchers had sufficient data to work with. They fully expect those numbers to become much higher once enough data to model “social mixing and immunization status of adults, teens, and infants under two” becomes available.

“The results of our study find substantial public health and economic consequences with even minor reductions in MMR coverage due to vaccine hesitancy and directly confront the notion that measles is no longer a threat in the United States,” they write.

The duo says they conducted this study out of concern for growing vaccine hesitancy and use of non-medical exemptions — both largely driven by shoddy data or outright lies pertaining to the safety of vaccines, and the downplaying of just how dangerous these diseases can be.

And measles is up there on the dangerous scale. The virus is ridiculously infectious, and can keep on floating in the air hours after a carrier coughed or sneezed. Those infected develop high fevers, skin rashes, inflamed eyes, and flu-like coughs and runny nose. About 30% of cases also come with highly desirable complications such as pneumonia, brain swelling, even blindness. While this does make it really simple to spot someone sick so you can stay away, carriers can spread the virus days before symptoms pop up.

Get your kid vaccinated!

So if the Eyeball Mk.1 we all come pre-equipped with can’t spot the danger, what do we do to stay safe? Well, we immunize the herd. So to speak. Basically, the idea behind herd immunity is to make such a large proportion of the population (around 90 to 95% of everybody) immune to the virus that it simply won’t be able to spread around effectively. There aren’t enough viable carriers to take spread it around.

It’s an all for one and one-starts-an-epidemic scenario. If immunity levels drop below that percentage, a single infected individual has a much higher chance of starting an outbreak — which, in turn, will have a much easier time infecting huge numbers of people. The bad news is that in many areas of the US, immunity levels are just shy of falling below that range, and vaccination rates still keep going down. Some 18 states allow parents to forego vaccination on the ground of personal beliefs, and almost all (except Mississippi and West Virginia) allow for religious and/or philosophical exceptions, according to the NCLS.

So, to get a feel for what these exceptions will do in the long run, the duo mathematically modeled the way measles spreads based on the virus’ known behavior, data on current vaccination rates from the CDC, and the “social mixing patterns” of kids aged 2-11. To get a rough estimate of the costs these outbreaks will take on the health system, they factored in stuff like medical staff wages, the cost of laboratory analyses, and money spent on outbreak surveillance. Each measles case, they estimate, costs about $20,000.

They then checked and calibrated their model based on data from past measles outbreaks from the US and UK. After they made sure their model works, they pushed up the vaccine exemption rate from 1% to 8% to see what would happen. Unsurprisingly, larger the exemption rates led to more cases and bigger outbreaks. Eliminating the exemptions however would take MMR coverage in the US to 95%, a very comfy percentage when talking about herd immunity.

In other words, when you chose not to vaccinate your kid, you’re putting both his health and that of others at risk. Stop believing what stupid stuff people say, believe, or write on shady websites over what your physician spent years learning in med school.

And most importantly, vaccinate your kids!

JAMA Pediatrics, 2017. DOI:10.1001/jamapediatrics.2017.1695 (About DOIs).

The paper “Public Health and Economic Consequences of Vaccine Hesitancy for Measles in the United States” has been published in the journal JAMA Pediatrics.

Europeans picked up a customized immune system by having sex with Neanderthals

Researchers have discovered that people of European and African descent have very different immune responses to infections. They believe these traits could be the result of modern humans breeding with Neanderthals after leaving Africa.

Image credits Paul Hudson / Flickr.

Sometime between one hundred to a few tens of thousands of years ago, as modern humans migrated out of Africa, they met strange peoples which weren’t completely like them, but not too different either — the Neanderthals. So, naturally, they had sex with them.

The genes we acquired in that exchange may be responsible for a whole range of diseases, but it’s possible they gave our ancestors the means to better adapt to their new environment. Scientists studying the immune system of humans today have found that people of European descent have significantly different immune responses from their African counterparts — a direct consequence of the exchange, they believe.

The finding could explain why Africans generally have more robust immune systems than Europeans, but also why they’re more predisposed to certain autoimmune conditions.

“I was expecting to see ancestry-associated differences in immune response but not such a clear trend towards an overall stronger response to infection among individuals of African descent,” says University of Montreal geneticist and paper co-author Luis Barreiro.

Barreiro’s team examined samples taken from 175 American patients, roughly half and half of African and European ancestry. They extracted macrophages from their blood — white cells that kill pathogens by “eating” them — and infected the cells with Listeria and Salmonella. They let them go about their business for 24 hours, then analyzed them.

The cells retrieved from the African group had reduced the bacterial growth three times faster than the European group thanks to a stronger inflammatory response. That’s a definite plus when combating infections, but the team points out it’s a double edged sword.

“The immune system of African Americans responds differently, but we cannot conclude that it is better,” Barreiro said, “since a stronger immune response also has negative effects, including greater susceptibility to autoimmune inflammatory diseases such as Crohn’s disease.”

The team also examined the genetic makeup of the cells’ active genes, and found a link between the European sample and Neanderthal DNA — but didn’t find any similar link in the African sample.

The team says that when early humans migrated into Europe around 100,000 years ago, they encountered a continent already colonized by the Neanderthal. Finding traces of their DNA in modern European subjects suggests that the two species actively bred with each other. It makes sense, too. The new genes would have offered our ancestors an evolutionary edge in Europe, where environmental conditions were very different from those in Africa. A lower inflammatory response would also make more sense in the colder climate compared to Africa’s sweltering heat, which promotes infections.

“Our results suggest that the immune systems of African- and European-descended individuals have evolved to better respond to the specific needs imposed by their specific environments,” Barreiro told Live Science.

“What is advantageous in one context is likely to be detrimental in another.”

Too much of a good thing

A separate study also found a lower inflammatory tendency in monocytes against bacterial and viral threats in people of European descent compared to those from Africa. The study included 200 participants from France. The team, led by Lluis Quintana-Murci from the Institut Pasteur, also tied the differences to Neanderthal-like genes in the European participants. In broad lines, the results are the same. The French team also suggests that a powerful inflammatory response could actually be dangerous in Europe, so this effect could have provided an inherent evolutionary benefit — weeding out the more inflammatory-prone genes over time.

“Reducing immune inflammatory responses is a way to avoid autoimmunity, inflammatory, and allergic reactions,” Quintana-Murci told ResearchGate.

“Finding that reduced immune responses has conferred an advantage highlights the tradeoff between recognising pathogens while avoiding exacerbated, aberrant reactions that can be also harmful for the host.”

Both studies say more work needs to be done before we understand where these differences stem from. But it could help us develop things like personalized treatments or medications tailored for certain ethnicities’ needs.

“There is still much to do,” says Barreiro. “[Genetics] explains only about 30 percent of the observed differences in immune responses. Our future studies should focus on other factors, emphasising the influence of the environment and our behaviour.”

Barreiro’s and Quintana-Murci’s studies are published in the journal Cell.

Red hair and fair skin are also thought to have been inherited from Neanderthals. [Image Source: BBC News

Interbreeding with Neanderthals gave humans an immunity boost, but also allergies

Some 50,000 years ago Homo sapiens, Neanderthals and Denisovans co-existed, mingled and interbred. While only the human lineage exists today, these inter-species  third degree meetings left a permanent mark on our genome. For instance, an ancient human who lived in what is today Romania had 9% Neanderthal DNA. Today, most Europeans and Asians have between 1 to 4 percent Neanderthal DNA. Indigenous sub-Saharan Africans have no Neanderthal DNA because their ancestors did not migrate through Eurasia. Some of these genes were rendered useless by countless generations of adaption to new environmental cues, once the last Ice Age was over, agricultural and livestock tendering was introduced and other important episodes that changed forever how humans lived. Some subsisted, though. Two studies investigated the functional value of genes inherited from Neanderthals and Denisovans. The researchers found interbreeding lent genes still use today by the immune system. As pesky byproduct was that it also rendered humans more prone to allergies.

Red hair and fair skin are also thought to have been inherited from Neanderthals. [Image Source: BBC News

Red hair and fair skin are also thought to have been inherited from Neanderthals.
[Image Source: BBC News

A team at the  Institut Pasteur and the CNRS in Paris went through the vast swaths of data from the  1000 Genomes Project. Their focus was on 1,500 genes known to play a role in the innate immune system, which they examined for patterns of genetic variation and evolutionary change with an unprecedented level of detail. They were able to estimate the time it took for these variations to take place and the  extent of Neanderthalian contribution.

Apparently, Neanderthals greatly influenced the Toll-like receptor (TLR) genes TLR1, TLR6, and TLR10, which help detect and respond to components of bacteria, fungi, and parasites.

Elsewhere, a team from the Max Planck Institute for Evolutionary Anthropology in Leipzig came to similar conclusions. The fact that they weren’t actually actively looking for immune system genes strengthens those findings made by the French researchers.

What they were interested in was studying the functional importance of genes inherited from archaic humans more broadly. First, they screened modern humans’ genomes for regions which were highly similar to the Neanderthal and Denisovan genomes.  Those analyses led them to the same three TLR genes. Two of those gene variants are most similar to the Neanderthal genome, whereas the third is most similar to the Denisovan genome.

This world map shows the frequencies of Neandertal-like TLR DNA in a 1000 Genomes dataset. The size of each pie is proportional to the number of individuals within a population. Credit: Dannemann et al./American Journal of Human Genetics 2016 .

This world map shows the frequencies of Neandertal-like TLR DNA in a 1000 Genomes dataset. The size of each pie is proportional to the number of individuals within a population. Credit: Dannemann et al./American Journal of Human Genetics 2016 .

These variants increase the activity of the  TLR genes, helping us today fight pathogens better. On the flipside, it also increased the susceptibility of modern-day people to allergies.

“We found that interbreeding with archaic humans—the Neanderthals and Denisovans—has influenced the genetic diversity in present-day genomes at three innate immunity genes belonging to the human Toll-like-receptor family,” says Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

“These, and other, innate immunity genes present higher levels of Neanderthal ancestry than the remainder of the coding genome,” adds Lluis Quintana-Murci of the Institut Pasteur and the CNRS in Paris. “This highlights how important introgression events [the movement of genes across species] may have been in the evolution of the innate immunity system in humans.”

All of this makes absolute sens. Before humans arrived in Europe, Neanderthals had lived there for hundreds of thousands of years. As such, they were better adapted and had a higher chance to survive, and by interbreeding with them we humans became stronger.

Ref:

1 )American Journal of Human Genetics, Deschamps et al.: “Genomic Signatures of Selective Pressures and Introgression from Archaic Hominins at Human Innate Immunity Genes” dx.doi.org/10.1016/j.ajhg.2015.11.014
2) American Journal of Human Genetics, Dannemann et al.: “Introgression of Neandertal- and Denisovan-like Haplotypes Contributes to Adaptive Variation in Human Toll-like Receptors” dx.doi.org/10.1016/j.ajhg.2015.11.015

Visitors of the Museum for Prehistory in Eyzies-de-Tayac, France observe a Neanderthal man ancestor's reconstruction (AFP/File, Patrick Bernard)

Human mating with Neanderthals made our immune system stronger

The mating between Neanderthals and modern homo sapiens has been a highly controversial matter between scientists in the anthropology scene for decades now. That was until last year, however, when anthropologists convened that the two related species did indeed mate, but the genes passed down from Neanderthals were inactive.

Recently, there’s been another reason for contradiction, once with the publishing of a new study this Thursday by Stanford scientists in which they outline how DNA inherited from Neanderthals and newly discovered hominids, dubbed the Denisovans, has contributed to the immune system of modern day man among populations in Europe, Asia and Oceania. Just so you can get an idea of how volatile studies and discoveries in the scientific world can be.

Prehistoric interbreeding is considered responsible for 4% of the homo sapiens genome; the Standford research, lead by Peter Parham from Stanford University School of Medicine in California, identifies stretches of DNA derived from our distant relatives.

Sex with Neanderthals made modern day humans stronger

The researchers focuses their attention  on a small set of genes on chromosome six, known as the human leukocyte antigen (HLA) class I genes, which help the immune system adapt to fight off new pathogens that could cause various infections, viruses and diseases. HLA-B*73, one of the types, was traced down to the newly discovered hominids called Denisovans, who likely  mated with humans arriving in West Asia on their way out of Africa. The variant is rare in modern African populations but is common in people in west Asia.

“The HLA genes that the Neanderthals and Denisovans had, had been adapted to life in Europe and Asia for several hundred thousand years, whereas the recent migrants from Africa wouldn’t have had these genes,” said Dr. Peter Parham.

“So getting these genes by mating would have given an advantage to populations that acquired them.”

A similar scenario was found with HLA gene types in the Neanderthal genome.

“We are finding frequencies in Asia and Europe that are far greater than the whole genome estimates of archaic DNA in modern humans, which is 1-6%,” said Professor Parham.

From the analysis, the scientists estimated that more than half of the genetic variants in one HLA gene in Europeans could be traced back to Neanderthal or Denisovan DNA. Asians owe up to 80%, and Papua New Guineans up to 95%.

Skepticism among other scientists

While this is a remarkable, ground-breaking study by all means, some scientists are still reluctant to accept its impact on the immune system and, consequently, passing on off active genes.

“I’m cautious about the conclusions because the HLA system is so variable in living people,” commented John Hawks, assistant professor of anthropology at the University of Wisconsin-Madison, US.
Denisovan tooth DNA from a tooth (pictured) and a finger bone show the Denisovans were a distinct group

“It is difficult to align ancient genes in this part of the genome.

“Also, we don’t know what the value of these genes really was, although we can hypothesise that they are related to the disease environment in some way.”

The study was published in the latest edition of the journal Science.