Long-lasting flu vaccine could replace yearly shots
November marked the start of flu season in the Northern Hemisphere. So if you haven’t gotten your flu shot yet, now’s the time. Unlike other vaccines that people may only need once in their lives, flu shots must be given yearly (to account for the ever-morphing virus it targets). But that soon may change. Researchers have just developed a vaccine that protects against many more types, or strains, of the flu virus. Its benefit? These shots might be able to confer lifelong protection from flu.
A flu shot can help you avoid fever, aches and fatigue that are no fun. But influenza poses far bigger risks for people who are very young or very old, or who have a weak immune system. For them this viral infection can be deadly.
U.S. statistics show how variable the risk of flu mortality can be from year to year. In some flu seasons, as few as 3,000 flu victims may die. Other years are far worse. Roughly 56,000 U.S. residents died from flu during the winter of 2012 to 2013.
Flu shots are the best defense against these infections. These vaccines teach the immune system how to identify a flu virus. That lets the body respond quickly to quash an infection before it can take hold.
But the flu virus evolves rapidly. The strains most likely to infect people this year will be different from last year’s major strains. If your immune system doesn’t recognize the latest version, you could get sick.
So scientists create new vaccines each year to target the latest variants. That’s why people need a new shot each year. But researchers at the University of Nebraska–Lincoln have developed a new vaccine that could last longer. To create it, they probed the genes of flu viruses and then “rewound” their evolutionary clock.
Hunting viral ancestors
Eric Weaver led the team. As a virologist, he studies viruses and how they affect the body. His group started by figuring out what the ancestral flu virus might have looked like. From what they learned, these researchers hoped to partially recreate some shared ancestor of today’s flu strains.
If two people trace their family trees back far enough, they will find a shared ancestor. That’s what Weaver and his team did with genes in the flu viruses. They traced them back to find genes from an ancestor that modern flu strains share in common.
There are 18 subtypes of flu, Weaver notes. The researchers worked with just four. These are the strains most likely to cause disease outbreaks in people. The scientists analyzed the viruses’ genes. From these, they created an average set of flu genes and put them into an artificial virus. This new virus might resemble the ancestor to the four modern strains.
Next, they created a vaccine to their artificial virus. To do this, they altered the genes so that they couldn’t cause illness. Then they inserted these into yet another virus. That recipient virus is called a vector. It can insert genes into cells. For their vector, the scientists chose a virus that causes the common cold.
That vector had been changed so it couldn’t make people or animals sick. Yet it could still insert its DNA into a host’s cells. That trait was important. (Viruses can’t reproduce on their own. Instead, they inject their genes into a host animal’s cells, which forces those cells to copy the virus.)
The researchers used their vector to deliver their new vaccine into cells. That triggered an immune response to the ancestral virus.
The team then tested its vaccine in mice. Some mice got a low dose of the vaccine (similar to what people might receive). Others got a high dose of it. A third group got a high dose of FluMist. This is a standard flu vaccine that’s not delivered as a shot. (It’s instead spritzed up the nose.) A final group of mice got a high dose of FluZone, the annual flu shot.
Four weeks later, scientists exposed the mice to one of nine different flu strains. Each mouse received enough virus to kill five to 50 mice, Weaver says.
Mice vaccinated with FluMist or FluZone died. These vaccines could not protect them from those heavy doses of virus. But mice that got the new vaccine were protected. Those getting a low dose of vaccine survived seven of the nine viruses.
"Mice are extremely well protected by this vaccine,” Weaver concludes.
Many studies have focused on how well just one part of the immune system responds to a flu vaccine, notes Matthew Miller. He was not involved with the new research, but he’s familiar with such studies. Miller’s own work at McMaster University in Ontario, Canada, focuses on immunity to viruses. Most studies in this field look at how well the body makes antibodies — a class of proteins — in response to the vaccine, he says. Those immune proteins help tag infected cells, he explains. But the ancestral-flu treatment stimulated other parts of the immune system, too. He suspects that difference “is really critical to having a vaccine that works well.”
When might the new vaccine be ready to give to people? It could be a while, Weaver thinks. One potential hurdle is those cold viruses commonly used as vectors. By the time people reach age 18, anywhere from one-fifth to half of them will already have been exposed to those viruses, Weaver says. So their immune systems may attack those vectors before they can help them the body build up a defense against influenza.
If scientists can overcome that challenge, however, a treatment like this one might one day replace yearly flu shots. “If we can use it as a childhood vaccine,” Weaver says, “we may be able to set up potentially life-long immunity.”
annual Adjective for something that happens every year.
antibody Any of a large number of proteins that the body produces from B cells and releases into the blood supply as part of its immune response. The production of antibodies is triggered when the body encounters an antigen, some foreign material. Antibodies then lock onto antigens as a first step in disabling the germs or other foreign substances that were the source of those antigens.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall.
Centers for Disease Control and Prevention (CDC) An agency of the U.S. Department of Health and Human Services, CDC is charged with protecting public health and safety by working to control and prevent disease, injury and disabilities. It does this by investigating disease outbreaks, tracking exposures by Americans to infections and toxic chemicals, and regularly surveying diet and other habits among a representative cross-section of all Americans.
DNA (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.
evolve (adj. evolving) To change gradually over generations, or a long period of time. In living organisms, such an evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs).
gene (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
host (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents.
immune system The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.
immunity The ability of an organism to resist a particular infection or poison by providing cells to remove, kill or disarm the dangerous substance or infectious germ. Or, when used colloquially, it means the ability to avoid some other type of adverse impact (such as firing from a job or being bullied).
infection A disease that can spread from one organism to another. It’s usually caused by some type of germ.
influenza (also known as flu) A highly contagious viral infection of the respiratory passages causing fever and severe aching. It often occurs as an epidemic.
morph Short for metamorphosis, it means to change from one form to another (such as from a caterpillar to a butterfly). Or it can mean to evolve or mutate, where one or more parts of the genome undergo some sort of change in their chemistry — and potentially in their function.
mortality Deaths. From mortal, meaning deadly.
outbreak The sudden emergence of disease in a population of people or animals. The term may also be applied to the sudden emergence of devastating natural phenomena, such as earthquakes or tornadoes.
protein A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
strain (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.
tag (in immunology) A chemical change that allows the immune system to identify cells or other material that it should attack and disable or remove.
trait A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.
vaccine (v. vaccinate) A biological mixture that resembles a disease-causing agent. It is given to help the body create immunity to a particular disease. The injections used to administer most vaccines are known as vaccinations.
variant A version of something that may come in different forms.
vector (in biology) A material used to introduce the genes of some outside organism, often for genetic engineering, immunology or other purposes.
virologist A researcher who studies viruses and the diseases they cause.
virus Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.