Cold Symptoms Linked to Immune Response, Not Cold Virus

Currently, there is not a cure for the common cold. When you catch a cold, doctors often advise that you drink a lot of fluids and maybe even have a bowl or two of chicken soup. You could take some cold medication, but these just work to mask the symptoms rather than cure the problem. However, recent research may change the way the common cold is dealt within fact, it may even lead to a cure.

The research, published in the November issue of American Journal of Respiratory and Critical Care Medicine, indicates that cold symptoms, such as coughing, sneezing, and a runny nose, are not caused by the human rhinovirus (HRV). (HRV is responsible for 30-50 percent of all common cold cases.) Instead, these symptoms result from the immune system response. The study was led by David Proud, a professor in the department of physiology and biophysics at the University of Calgary in Canada. In conducting his research, Proud collaborated with scientists at the University of Virginia and Procter & Gamble Company.

In the study, 35 volunteers were injected with either HRV or a harmless substance. Skin scrapings from the inside of each volunteer’s nose were taken both before and after infection. Researchers at Procter & Gamble used gene chip technology to analyze whether any genetic changes took place after infection. Gene chip technology lets scientists see every gene in the human genome–allowing scientists to see how genes respond to a stimulus, such as the introduction of a cold virus.

The researchers did not detect any changes to the test subjects’ DNA after a period of 8 hours. However, after a period of 48 hours, scientists discovered that over 6500 genes had been altered. The affected genes showed either an increased or decreased amount of activity. The genes that were most affected were those that make antiviral proteins and pro-inflammatory chemicals. This finding shows that antiviral proteins work to thwart the rhinovirus, but also produce the symptoms associated with a cold.

Results from this research may help scientists develop an effective cure for the common cold. If they can identify the pro-inflammatory genes, they could develop methods to block the genes’ function. However, researchers are hoping to find more than just a cure for the common cold. The pathogen responsible for the rhinovirus has also been implicated in more serious health conditions such as asthma and chronic obstructive pulmonary disease (COPD). By learning how to combat the rhinovirus, researchers may also be able to find a way to cure these conditions as well.

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The Spoils of War — How T Cells Refuel to Wage War on Pathogens

A killer T cell attacks an infected cell.

In humans, T cells fight viruses and other invaders. Scientists have long thought T cells simply killed an enemy and then moved on to fight others, but new research suggests that some T cells use the spoils of their battles to win the larger war.

White blood cells are part of the immune system, the human body’s main defense against viruses and other infectious agents, all of which are called pathogens. Pathogens take over the machinery of a cell and cause it to manufacture more pathogens, leading to infection. The body has six major classes of white blood cells, each offering specific weaponry and tactics for combating infection. One class of white blood cells is the lymphocytes, which include T cells and B cells.

Killer T Cells

One type of T cell, the CD8+ T cell, is known more commonly as a “killer” T cell. It attacks infected cells with cytoxins, which cause the plasma membrane of an infected cell to open, allowing water, ions, and toxins to rush in. The infected cell then swells and bursts, destroying the pathogens that have taken over the cell. Until recently, scientists thought that T cells left their victims after killing them and simply moved on to attack other infected cells. Results of recent research, however, show that the interaction between killer T cells and infected cells is more like that of predator and prey.

Caught “Green-Handed”

Mark Slifka and Carol Beadling, researchers at Oregon Health & Science University’s Vaccine and Gene Therapy Institute, happened upon this discovery while observing interactions between killer T cells and cells infected by a virus.

Slifka and Beadling dyed infected cells with a fluorescent green dye so that these cells could be more easily seen under a microscope. They then unleashed killer T cells that were specific to the virus of the infected cells, to observe their interactions. They watched the small T cells attack and kill the large green infected cells as expected. But Slifka and Beadling noticed something strange. The T cells, which had not been dyed, were themselves turning green as the infected cells broke apart. Slifka and Beadling realized that the T cells were actually eating portions of the infected cells’ membranes. Like a child whose tongue is stained purple from a popsicle, the fluorescent dye was a telltale sign that the killer T cells weren’t just killing the infected cells, they were feeding on them. They had been caught “green-handed.”

A Well-Fed Army

A fluorescent infected cell is killed and partially devoured by killer T cells. (Credit: David Parker and Scott Wetzel/OHSU)

“This is truly a case of microscopic cannibalism,” Slifka says. “And this is the first time we’ve seen virus-specific killer T-cells ingest parts of infected cells.” Slifka thinks that the benefit of this behavior is that T cells can refuel themselves before fighting other infected cells. He compares this to an army of warriors that invades a city, destroys it, but takes care to gather resources that could help it maintain strength in its ongoing war. “Not only do you have this warrior cell coming in and attacking these virus factories, but it’s able to take away nourishment from this in order to help it to continue the fight against the infection,” he says.

A similar response to virus-infected cells by CD4+ T cells, also known as “helper” T cells, was observed by researcher David Parker, also of the Oregon Health & Science University. The value, Slifka says, of these discoveries about T cells is that the same experimental techniques used to study interactions with pathogens could be applied to observe and measure the response of T cells to a vaccine.

Hope for Vaccines?

A vaccine is a substance that carries the identifying markers, or antigens, of a virus but does not have the destructive capabilities of the actual virus. Some vaccines are made from dead viruses. Others are weakened versions of a virus. A vaccine triggers an immune response. The body produces lymphocytes such as B and T cells that will be able to recognize the real virus should it ever appear in the body. In other words, a vaccine teaches the human body how to identify and defeat a virus, but without putting the body through the danger of the real viral infection.

Slifka’s findings suggest that if a vaccine were marked with a fluorescent green dye, and killer T cells were then unleashed to attack and consume the vaccine, scientists could accurately measure the interaction between the vaccine and the killer T cells. This could help determine a vaccine’s effectiveness, as well as the dosage needed to immunize a person.

More to Explore

Check out the following sites to hear from Dr. Slifka, read more about his discovery, and watch killer T cells as they kill and eat an infected cell.