Immunology – GOLLYGEE!

10.20.2014

ebola

An electron micrograph of an Ebola virus virion.

Ebola has been making lots of news this year, as the virus has popped up in several West African countries. We are in the midst of the largest and most widespread outbreak in history.

Fruit bats are the main carriers of the virus in nature. Initially, humans become infected with the ebola virus after contact with infected bats or any living or dead animals that have been infected by the bats. This contact is often thought to be from consumption of infected meat. After humans become infected, the disease spreads through contact with infected bodily fluids including sweat, saliva, urine and semen. Ebola is insidious, and in some cases can take up to 21 days after exposure before symptoms manifest. Symptoms include a sudden onset of flu-like fever, ache and fatigue followed by vomiting or diarrhea.

Sky News details why the virus is so deadly:

When ebola enters the body, it targets dendritic cells in the immune system. Normally, when a virus is detected, these cells tell other cells to produce antibodies. Ebola prevents that signal getting out. As far as the immune system knows, everything inside the body is fine. Left alone, ebola then begins replicating rapidly. It then spreads into the bloodstream, infecting the whole body. Cells start to break up and die, in huge numbers. That finally triggers the immune system, which kicks in – far too aggressively.

Ordinarily when you get sick, the body releases proteins called cytokines. Some of these cells tell your blood vessels to become more permeable. This is to let antibodies travel through the body more quickly to fight the disease. But once ebola has taken hold of your body, the immune system reacts much too aggressively – and launches a cytokine storm. This causes blood vessels to become far too permeable, and they leak. At the same time, the body’s blood clotting mechanisms also act abnormally. This causes internal and external bleeding and is why ebola is known as a haemorrhagic fever. It causes tissue damage and organ failure.

Though the disease is deadly, people do survive and countries can contain outbreaks. Survivors’ blood may contain antibodies that can be used to treat others suffering from the disease.

08.27.2014

do gut bacteria prevent allergies?

Intestinal tracts of germ free mice and mice given clostridia bacteria. The higher levels of mucus in the clostria tracts is thought to prevent allergens from leaking into the bloodstream.

Science News brings word of a recent PNAS report on gut bacteria and allergies. In the study, researchers gave a group of mice antibiotics to wipe out their gut microbiome. Feeding the mice peanuts after this treatment seemed to induce allergy-like responses, that weren’t observed in mice who didn’t receive the treatment. The researchers gave the mice Clostridia bacteria to replenish the microbiome, and the response diminished.

Cathryn Nagler of the University of Chicago and colleagues treated some mice with antibiotics to wipe out the animals’ gut bacteria, and then triggered an allergy-like response to peanut particles. Peanuts revved up the germ-free animals’ immune systems — but mice with normal gut bacteria didn’t have the bad reaction.

Giving germ-free mice a dose of Clostridia bacteria made the animals more like their counterparts with normal gut flora. The microbes encourage mouse cells to make mucus that helps seal up the intestines, keeping food particles from slipping into the bloodstream and riling up the immune system, the researchers found.

The researchers suggest that this might also hold true for humans.

11.22.2013

bacteria aid chemotherapy response

Image from Discover Magazine

In the latest edition of Science magazine, two papers describe how bacteria in the stomach and intestines can help improve chemotherapy outcomes – at least in mice.

In the first study, Iida et al. dosed a group of mice with antibiotics for a prolonged period before exposing them to cancer therapies. The antibiotic treatment eliminated their populations of gut microbes. Tumors in these mice did not shrink in response to the therapy as they did in the control group, which received no antibiotics. Similarly, mice brought up in a sterile environment also had showed no chemotherapeutic response. Mice brought up in sterile environments never develop diverse microbial populations since they don’t get exposed to them. Mice lacking the bacterial populations don’t show the production of a protein called tumor necrosis factor that generates the tumor killing response in the organism.

The researchers also found that when the chemotherapeutic drug oxaliplatin was administered to mice who were germ-free or given antibiotics, the cancer killing response was much weaker and ineffective when compared to the control.

The second group of researchers performed similar studies with a chemotherapy drug called cyclophosphamide, or CTX. CTX is used to treat breast cancers and some brain cancers and works by increasing the number of Th17/Th1 immune cells. As in the previously mentioned study, mice that were dosed with antibiotics or that were raised in sterile environments exhibited a weaker anti-tumor response to the CTX.

Results from both of these studies indicate that microbes influence anti-tumor responses. So what does that mean for cancer patients? Dr. Zitvogel, who led one of the research teams, is taking considering the implications saying “We are going to be very careful about prescribing antibiotics during chemotherapy.” Dr. Trinchieri, who led another team, says that we should be cautious about extrapolating any results from mice to humans. He also suggests studies in healthy humans examining the effect of gut bacteria on immune cell production. His sentiment would likely be seconded by most scientists. As a matter of fact, Science magazine has another article in the same issue titled “When Mice Mislead”.

GOLLYGEE!

Category: Immunology (page 1 of 7)

ebola

do gut bacteria prevent allergies?

bacteria aid chemotherapy response