Efficacy of Tuberculosis Vaccine Enhanced Thanks to New Research

ScienceDaily (Feb. 19, 2011) — Nele Festjens and Nico Callewaert of VIB and Ghent University have improved the efficacy of the vaccine for tuberculosis. The new vaccine affords -- as already proven in mice -- better protection against the disease. The development of a new tuberculosis vaccine is a priority in the fight against the disease which claims the lives of 1.7 million people each year. The current vaccine provides only partial protection.

Nico Callewaert: "Our vaccine is more effective because it is more quickly recognized by the immune system of the vaccinated person. We have, as it were, undressed the existing vaccine by removing its protective shield."

Tuberculosis: a worldwide problem

One third of the world population is infected with the Mycobacterium tuberculosis bacterium which causes tuberculosis (TB). TB, AIDS and malaria are the three infectious diseases claiming the largest number of fatalities worldwide. The World Health Organization (WHO) estimates that each year 8 to 10 million people become infected. TB is in particular a disease of the poor and mainly affects young adults in their most productive years. Most TB fatalities are in the developing countries, more than half of them in Asia. In almost all of these countries, multidrug-resistant TB is becoming increasingly frequent. This form of TB is very hard to treat.

Prevention is better than cure

TB treatments are expensive and also very difficult because of multidrug-resistant TB. There has therefore been a strong focus on vaccination in the fight against TB. The only vaccine on the market is Bacillus Calmette-Guérin (BCG). It is produced from attenuated live bovine tuberculosis bacterium, Mycobacterium bovis, which has lost its virulence in humans. In children, the vaccine prevents only half of cases of tuberculosis and in adolescents and adults the degree of protection is much lower still.

In recent years, several other candidate vaccines have been developed and some of these have been tested on humans. Only a few have led to a moderate improvement in protection compared with the BCG vaccine. The search for a more efficient vaccine is therefore still on.

Removing the bacterium's defense shield

The bacterium from which the BCG vaccine is derived hides as it were from the immune system of the organism in which it ends up. This may well be the reason why the vaccine is not very effective. The fact is that a vaccine is meant to trigger an immune reaction in order to be able to afford good protection. Nele Festjens and Nico Callewaert have discovered that the bacterium hides behind the SapM enzyme that acts as a kind of shield.

They have used this knowledge to develop a new vaccine. They adapted Mycobacterium bovis BCG in such a way that it was no longer able to generate SapM and could therefore no longer hide from the immune system. Testing the new vaccine on mice has shown that it affords better protection than the present BCG vaccine.

A different mechanism

The researchers also demonstrated that their vaccine works in a way different from the other vaccines currently being tested. In fact, it acquires its extra protective value by emitting signals that provoke inflammation and in this way activate the right cells of the immune system. Festjens and Callewaert are convinced that applying their strategy -- removing the protective shield -- in the new vaccines that are somewhat better than the vaccine currently being marketed should lead to a vaccine that affords genuine protection against TB.

Conventional Wisdom of How Neurons Operate Challenged: Axons Can Work in Reverse

ScienceDaily (Feb. 19, 2011) — Neurons are complicated, but the basic functional concept is that synapses transmit electrical signals to the dendrites and cell body (input), and axons carry signals away (output). In one of many surprise findings, Northwestern University scientists have discovered that axons can operate in reverse: they can send signals to the cell body, too.

Computer-generated image representing connections between neurons. 

It also turns out axons can talk to each other. Before sending signals in reverse, axons can perform their own neural computations without any involvement from the cell body or dendrites. This is contrary to typical neuronal communication where an axon of one neuron is in contact with another neuron's dendrite or cell body, not its axon. And, unlike the computations performed in dendrites, the computations occurring in axons are thousands of times slower, potentially creating a means for neurons to compute fast things in dendrites and slow things in axons.

A deeper understanding of how a normal neuron works is critical to scientists who study neurological diseases, such as epilepsy, autism, Alzheimer's disease and schizophrenia.

The findings are published in the February issue of the journalNature Neuroscience.

"We have discovered a number of things fundamental to how neurons work that are contrary to the information you find in neuroscience textbooks," said Nelson Spruston, senior author of the paper and professor of neurobiology and physiology in the Weinberg College of Arts and Sciences. "Signals can travel from the end of the axon toward the cell body, when it typically is the other way around. We were amazed to see this."

He and his colleagues first discovered individual nerve cells can fire off signals even in the absence of electrical stimulations in the cell body or dendrites. It's not always stimulus in, immediate action potential out. (Action potentials are the fundamental electrical signaling elements used by neurons; they are very brief changes in the membrane voltage of the neuron.)

Similar to our working memory when we memorize a telephone number for later use, the nerve cell can store and integrate stimuli over a long period of time, from tens of seconds to minutes. (That's a very long time for neurons.) Then, when the neuron reaches a threshold, it fires off a long series of signals, or action potentials, even in the absence of stimuli. The researchers call this persistent firing, and it all seems to be happening in the axon.

Spruston and his team stimulated a neuron for one to two minutes, providing a stimulus every 10 seconds. The neuron fired during this time but, when the stimulation was stopped, the neuron continued to fire for a minute.

"It's very unusual to think that a neuron could fire continually without stimuli," Spruston said. "This is something new -- that a neuron can integrate information over a long time period, longer than the typical operational speed of neurons, which is milliseconds to a second."

This unique neuronal function might be relevant to normal process, such as memory, but it also could be relevant to disease. The persistent firing of these inhibitory neurons might counteract hyperactive states in the brain, such as preventing the runaway excitation that happens during epileptic seizures.

Spruston credits the discovery of the persistent firing in normal individual neurons to the astute observation of Mark Sheffield, a graduate student in his lab. Sheffield is first author of the paper.

The researchers think that others have seen this persistent firing behavior in neurons but dismissed it as something wrong with the signal recording. When Sheffield saw the firing in the neurons he was studying, he waited until it stopped. Then he stimulated the neuron over a period of time, stopped the stimulation and then watched as the neuron fired later.

"This cellular memory is a novelty," Spruston said. "The neuron is responding to the history of what happened to it in the minute or so before."

Spruston and Sheffield found that the cellular memory is stored in the axon and the action potential is generated farther down the axon than they would have expected. Instead of being near the cell body it occurs toward the end of the axon.

Their studies of individual neurons (from the hippocampus and neocortex of mice) led to experiments with multiple neurons, which resulted in perhaps the biggest surprise of all. The researchers found that one axon can talk to another. They stimulated one neuron, and detected the persistent firing in the other unstimulated neuron. No dendrites or cell bodies were involved in this communication.

"The axons are talking to each other, but it's a complete mystery as to how it works," Spruston said. "The next big question is: how widespread is this behavior? Is this an oddity or does in happen in lots of neurons? We don't think it's rare, so it's important for us to understand under what conditions it occurs and how this happens."

In addition to Spruston and Sheffield, other authors of the paper are Tyler K. Best and William L. Kath, from Northwestern, and Brett D. Mensh, from Harvard Medical School.

Two Genes Involved in Hereditary Breast and Ovary Cancer Cases

ScienceDaily (Feb. 18, 2011) — Between 5 and 10 percent of breast cancer cases are hereditary, arising because the patient inherits from the father or mother a mutation in a gene that is susceptible to causing the illness. BRCA1 and BRCA2 have already been identified as two of the genes to be monitored. It is estimated that 30 percent of hereditary breast cancer cases are due to mutations in one of these two genes (which suggests, at the same time, that there are other genes involved, but exactly how is still unknown). In any case, few of the mutations found in BRCA1 and BRCA2 could be clearly identified as pathological. The fact is that the mutations found were numerous; their variation even depending on the population.

Biologist Elena Beristain has been investigating the CAPV-EAE population. Concretely, for her study she took 521 patients mainly from the Txagorritxu hospital in the Basque capital city of Vitoria-Gasteiz, and the Cruces hospital in Barakaldo, near Bilbao: 274 patients with breast or ovarian cancer (given that the latter is also associated with mutations in the BRCA1 and BRCA2 genes), 115 family relations of these, and another 132 women who acted as a control population. Ms Beristain molecularly characterised the BCRA1 y BCRA2 genes of these individuals; apart from the exon 10 of the CHEK2 gene, also associated with the illness. Her thesis was defended at the University of the Basque Country (UPV/EHU) and it is entitled, Genetic study amongst women resident in the CAPV-EAE with hereditary breast/ovary cancer.

Could rise to 12 percent

According to the results shown, different types of variations in the genes under study have been found, including pathological ones, neutral ones and those of uncertain significance. As regards the clearly pathological mutations, the frequency is 10 percent. Nevertheless, Ms Beristain stressed that, amongst those sporadic cases of under-40s, that is a especially rare condition: only in one case was a pathological mutation found. This is why she suggested discarding under-35s in this type of research, and in which case the result arrived at in her study rises from 10 percent to 12 percent. In any case, the percentages of pathological mutations found in this genetic study of the CAPV-EAE population turned out to be less than amongst other European populations.

The study has thrown up more data regarding age. For example, the percentages show that, for family-member carriers of mutation in the main genes under study, the accumulated risk of suffering breast cancer at 70 is 69 percent for the BRCA1 and 67 percent for the BRCA2. This means that penetration is not complete and there exists the possibility that this gene does not, in the end, express itself. As regards the data on gender, it is significant that masculine breast cancer is mainly associated with mutations in the BRCA2 gene.

Different mutations in the Autonomous Community of the Basque Country

The variability from population to population in mutations in general is also clear from the results of this thesis. Ms Beristain explained that a great number of alterations, hitherto unrecorded, have been found, and from this she concludes that many of the mutations found in the CAPV-EAE are different from those described for other populations. However, she explains, amongst these, no founder effect mutation was found, i.e. there has been no case of some, many or all Basque patients coming from a small population of individuals having transmitted this common genetic characteristic to all their descendents. However it may be, the new types of mutations found represent a contribution to the already existing variability.

Como Disordered Proteínas Spread de célula a célula, potencial propagação da doença

ScienceDaily (Feb. 18, 2011) — One bad apple is all it takes to spoil the barrel. And one misfolded protein may be all that's necessary to corrupt other proteins, forming large aggregations linked to several incurable neurodegenerative diseases such as Huntington's, Parkinson's and Alzheimer's.

An image of U2OS cells infected with Q91 polygluytamine aggregates (in green) colocalized with intracelluluar expressed (red) Q25.

Stanford biology Professor Ron Kopito has shown that the mutant, misfolded protein responsible for Huntington's disease can move from cell to cell, recruiting normal proteins and forming aggregations in each cell it visits.

Knowing that this protein spends part of its time outside cells "opens up the possibility for therapeutics," he said. Kopito studies how such misfolded proteins get across a cell's membrane and into its cytoplasm, where they can interact with normal proteins. He is also investigating how these proteins move between neuronal cells.

The ability of these proteins to move from one cell to another could explain the way Huntington's disease spreads through the brain after starting in a specific region. Similar mechanisms may be involved in the progress of Parkinson's and Alzheimer's through the brain.

Kopito discussed his research on Feb. 18 at the annual meeting of the American Association for the Advancement of Science in Washington, D.C.

Not all bad

Not all misfolded proteins are bad. The dogma used to be that all our proteins formed neat, well-folded structures, packed together in complexes with a large number of other proteins, Kopito said. But over the past 20 years, researchers have found that as much as 30 percent of our proteins never fold into stable structures. And even ordered proteins appear to have some disordered parts.

Disordered proteins are important for normal cellular functions. Unlike regular proteins, they only interact with one partner at a time. But they are much more dynamic, capable of several quick interactions with many different proteins. This makes them ideal for a lot of the standard communication that happens within a cell for its normal functioning, Kopito said.

But if some of our proteins are always disordered, how do our cells tell which proteins need to be properly folded, and which don't? "It's a big mystery," said Kopito, and one that he's studying. This question has implications for how people develop neurodegenerative diseases, all of which appear to be age-related.

Huntington's disease is caused by a specific mutated protein. But the body makes this mutant protein all your life, so why do you get the disease in later adulthood? Kopito said it's because the body's protective mechanisms stop doing their job as we get older. He said his lab hopes to determine what these mechanisms are.

A bad influence

But it's clear what happens when these mechanisms stop working -- misfolded proteins start recruiting normal versions of the same protein and form large aggregations. The presence of these aggregations in neurons has been closely linked with several neurodegenerative diseases.

Kopito found that the mutant protein associated with Huntington's disease can leave one cell and enter another one, stirring up trouble in each new cell as it progresses down the line. The spread of the misfolded protein may explain how Huntington's progresses through the brain.

This disease, like Parkinson's and Alzheimer's, starts in one area of the brain and spreads to the rest of it. This is also similar to the spread of prions, the self-replicating proteins implicated in mad cow disease and, in humans, Creutzfeldt-Jakob disease. As the misfolded protein reaches more parts of the brain, it could be responsible for the progressive worsening of these diseases.

Now that we know that these misfolded proteins spend part of their time outside of cells, traveling from one cell to another, new drugs could target them there, Kopito said. This could help prevent or at least block the progression of these diseases.

Kopito is currently working to figure out how misfolded proteins get past cell membranes into cells in the first place. It is only once in the cell's cytoplasm that these proteins can recruit others. So these studies could help find ways to keep these mischief-makers away from the normal proteins.

He is also collaborating with biology professor Liqun Luo to track these proteins between cells in the well-mapped fruit fly nervous system. In the future, Kopito said he hopes to link his cell biology work to disease pathology in order to understand the role misfolded proteins play in human disease.

Male Fertility Is in the Bones: First Evidence That Skeleton Plays a Role in Reproduction

ScienceDaily (Feb. 18, 2011) — Researchers at Columbia University Medical Center have discovered that the skeleton acts as a regulator of fertility in male mice through a hormone released by bone, known as osteocalcin.

Researchers have found an altogether unexpected connection between a hormone produced in bone and male fertility. The study shows that the skeletal hormone known as osteocalcin boosts testosterone production to support the survival of the germ cells that go on to become mature sperm.

The research, led by Gerard Karsenty, M.D., Ph.D., chair of the Department of Genetics and Development at Columbia University Medical Center, is slated to appear online on February 17 in Cell, ahead of the journal's print edition, scheduled for March 4.

Until now, interactions between bone and the reproductive system have focused only on the influence of gonads on the build-up of bone mass.

"Since communication between two organs in the body is rarely one-way, the fact that the gonads regulate bone really begs the question: Does bone regulate the gonads?" said Dr. Karsenty.

Dr. Karsenty and his team found their first clue to an answer in the reproductive success of their lab mice. Previously, the researchers had observed that males whose skeletons did not secrete a hormone called osteocalcin were poor breeders.

The investigators then did several experiments that show that osteocalcin enhances the production of testosterone, a sex steroid hormone controlling male fertility. As they added osteocalcin to cells that, when in our body produce testosterone, its synthesis increased. Similarly, when they injected osteocalcin into male mice, circulating levels of testosterone also went up.

Conversely, when osteocalcin is not present, testosterone levels drop, which causes a decline in sperm count, the researchers found. When osteocalcin-deficient male mice were bred with normal female mice, the pairs only produced half the number of litters as did pairs with normal males, along with a decrease in the number of pups per litter.

Though the findings have not yet been confirmed in humans, Dr. Karsenty expects to find similar characteristics in humans, based on other similarities between mouse and human hormones.

If osteocalcin also promotes testosterone production in men, low osteocalcin levels may be the reason why some infertile men have unexplained low levels of testosterone.

Skeleton Regulates Male Fertility, But Not Female

Remarkably, although the new findings stemmed from an observation about estrogen and bone mass, the researchers could not find any evidence that the skeleton influences female reproduction.

Estrogen is considered one of the most powerful hormones that control bone; when ovaries stop producing estrogen in women after menopause, bone mass rapidly declines and can lead to osteoporosis.

Sex hormones, namely estrogen in women and testosterone in men, have been known to affect skeletal growth, but until now, studies of the interaction between bone and the reproductive system have focused only on how sex hormones affect the skeleton.

"We do not know why the skeleton regulates male fertility, and not female. However, if you want to propagate the species, it's probably easier to do this by facilitating the reproductive ability of males," said Dr. Karsenty. "This is the only rationale I can think of to explain why osteocalcin regulates reproduction in male and not in female mice."

Other Novel Functions of Osteocalcin Reported Earlier

The unexpected connection between the skeleton and male fertility is one of a string of surprising findings in the past few years regarding the skeleton. In previous papers, Dr. Karsenty has found that osteocalcin helps control insulin secretion, glucose metabolism and body weight.

"What this work shows is that we know so little physiology, that by asking apparently naïve questions, we can make important discoveries," Dr. Karsenty says. "It also shows that bone exerts an important array of functions all affected during the aging process. As such, these findings suggest that bone is not just a victim of the aging process, but that it may be an active determinant of aging as well."

Next Steps and Potential Drug Development

Next, the researchers plan to determine the signaling pathways used by osteocalcin to enhance testosterone production.

And as for potential drug development, since the researchers have also identified a receptor of osteocalcin, more flexibility in designing a drug that mimics the effect of osteocalcin is expected.

Whether it's for glucose metabolism or fertility, says Dr. Karsenty, knowing the receptor will make it easier for chemists to develop a compound that will bind to it.

"This study expands the physiological repertoire of osteocalcin, and provides the first evidence that the skeleton is a regulator of reproduction," said Dr. Karsenty.