"Vanishing" HIV, A Vaccine to Sniff
British "designer baby" ignites ethics debate
RESEARCHERS UNTANGLE
HIV ANTIBODY STRUCTURE...
WASHINGTON
Scientists have unraveled the structure of an antibody that effectively neutralizes HIV, the key to a possible vaccine against the fatal acquired immune deficiency syndrome, according to a June 26 report in Science.
"What we found was an unusual configuration of the antibody in which its two Fab domains-the antigen recognition units-are 'interdigitating' with each other," wrote Ian Wilson, one of two Scripps Research Institute professors who led the research. "Nothing like this has ever been seen before," he said. This new structure is an important step toward the goal of designing an effective vaccine against HIV and it gives researchers a new way to design antibodies in general."
"It may enable us to make antibodies that recognize whole new sets of molecules," wrote coauthor Prof. Dennis Burton.
The Scripps team explained that HIV causes AIDS by binding to, entering, and ultimately killing "T" helper cells, immune cells that are necessary to fight off infections by common bacteria and other pathogens. "As HIV depletes the body of T helper cells, common pathogens can become potentially lethal," they said.
... DISCOVER HIV VANISHING ACT
PARIS
Scientists in the US believe the AIDS virus craftily hijacks an immune cell to help it evade elimination by powerful antiretroviral drugs.
Dismaying evidence started to emerge a few years ago that highly active antiretroviral therapy (HAART), introduced in 1995, was not the HIV slayer that it initially appeared to be. It was discovered that HAART can beat HIV back to below detectable levels in the bloodsteam-but, as soon as the medication is stopped, the virus bounces back from some hidden "reservoir," presumed to be the lymph glands. So a frantic search was launched to find out how the virus did this disappearing trick. Until now, it has yielded few clues.
Reporting in the July 10 issue of Nature, a team led by Mario Stevenson of the University of Massachusetts Medical School says that HIV1 uses a "pirate protein" to hide inside inactive immune cells, then reappears at a later date.
The virus first infects a cell called a macrophage, inducing it into producing a viral protein called Nef. Nef then prompts the macrophage into releasing a couple of other proteins called soluble factors, which go on to stimulate other components of the immune system that are called B cells. These subverted B cells then come into contact with inactive defenders of the immune system-resting T cells-and in effect open up the T cells, making them vulnerable to infection by HIV.
It amounts to an astonishingly complex ballet by signaling molecules. In particular, it smashes a hole in the prevailing belief that HIV-1 could infect only T cells that had been activated after encountering an invader and were starting to replicate.
"Nef seems to engage in molecular piracy, taking over an existing cellular pathway and allowing HIV-1 to replicate in T cells in diverse activation states," said Roger Pomerantz of Thomas Jefferson University, Philadelphia in a commentary. The data show "there is an entire spectrum of interactions between the virus and host cells, which together produce the general pattern of HIV-1 reservoirs and residual disease."
"DESIGNER BABY" BORN IN BRITAIN
LONDON
A genetic "designer baby" has been born in Britain to a couple desperate to cure their young son who has a rare form of anemia, rekindling debate over the ethics of stem-cell research.
Jamie Whitaker was delivered by Caesarean section on June 16 at a hospital in Sheffield, northern England. He was genetically matched while still an IVF embryo to his four-year-old brother Charlie, who has the rare Diamond Blackfan anemia, which only a transplant of stem cells from a sibling with a perfect tissue match can cure. His parents, Jayson and Michelle Whitaker, had turned to the Reproductive Genetics Institute in Chicago, Illinois for treatment after Britain's Human Fertilization and Embryology Authority refused them permission to genetically select a tissue match embryo.
"All we did was change the odds from a one-in-four chance of a tissue match to a 98-percent chance," said Whitaker. "There was no selection on the basis of color of eyes or hair or sex." He said tests were being carried out to see if Jamie is a perfect tissue match and has the same anemia condition as his brother.
The Daily Mail said Jamie was "Britain's first designer baby."
But Lana Rechitsky of the Chicago Reproductive Genetics Institute claimed that the child was the second born in Britain as a tissue match. She rejected suggestions that Mrs. Whitaker's fertility treatment was unethical. "The main thing people say we are doing wrong is they say we are making designer babies. That is wrong," the doctor said.
She added: "These are not designer babies. We are not creating anything new. We are just trying to choose between the embryos to find the one that is normal and can save the life of its sibling. These are not babies brought into the world just to save the sibling's life. These are families who want a healthy child-and if that healthy child can also save the life of the child they already have, I think it is a double blessing. There was no other way for Charlie to survive."
Rechitsky said doctors had selected among 10 embryos to choose one that would be able to provide appropriate stem cells.
The Whitakers will have to wait six months before Charlie is treated in order to ensure that Jamie is not affected by the same syndrome. But Rechitsky said that there was believed to be no more than a three-percent chance of this happening.
NASAL FLU VACCINE
WASHINGTON
The first flu vaccine taken nasally has been approved for the US market, the US Food and Drug Administration said.
FluMist has been developed to fight flu virus strains A and B, and is the first vaccine approved by the FDA that uses active virus ingredient. The vaccine, available to adults and children five years and older, is designed to give resistance to a virus that causes around 36,000 deaths a year in the US.
While it widely affects children in the five to 14-year age group, its worst impact is felt among people already weakened by illness, as well as babies and people 65 and above, according to the US Centers for Disease Control.
"This new vaccine provides another option for protection against influenza," said FDA Commissioner Mark McClellan. "For those people who are eligible for the new vaccine and are reluctant to get a shot, such as healthy children over the age of five, the availability of FluMist will be especially welcome."
The vaccine will be effective against at least three strains of the flu virus in the 2003-2004 flu season: two belonging to type A which causes the most severe epidemics, and one from type B. It is manufactured by MedImmune Vaccines based in Gaithersburg, Maryland.
TASTES GREEK, BUT GOOD FOR THE HEART?
NEW YORK
A traditional Mediterranean diet favoring vegetables, fruits, olive oil, and fish can reduce premature mortality rates by at least 25 percent, according to a study by researchers from the Harvard School of Public Health and the University of Athens Medical School.
The main benefit of the diet-which is rich in complex carbohydrates and so-called "healthy" fats-is a sharp drop in the risk of heart disease and cancer.
"The results are clear," said Dimitrios Trichopoulos, senior author of the study that involved 22,043 adults between the ages of 20 and 86 who live in Greece. "A Mediterranean diet featuring olive oil, vegetables, fish, fruits, and low in saturated fats and enjoyed for many years by the people of that region, is healthy and promotes longevity," Trichopoulos wrote in the New Journal England of Medicine.
The study coincides with a widespread debate in the US over whether to review national dietary guidelines. Federal guidelines have long proposed a low-fat, high-carbohydrate diet, but they have recently been challenged by various studies backing the high-fat, low-carbohydrate approach championed by the late Robert Atkins.
The Mediterranean diet, when combined with healthy exercise, appears to fall neatly between both camps.
The new study began with in-depth interviews with all participants regarding their dietary habits. Points were awarded according to how closely each individual adhered to the Mediterranean diet. Regular, moderate consumption of fish garnered one point, as did a daily intake of fruits and vegetables. Moderate consumption of wine with meals-one glass for women, two for men-was also worth a point. The participants' health was then monitored for four years, with the study showing that for every two-point rise, the risk of death dropped by 25 percent.
"The magnitude of the reduction in mortality underscores the longevity advantage that adult Mediterranean populations have experienced for centuries," said Trichopoulos.
The study also showed that the relationship between closely following the Mediterranean diet and reduced mortality appeared to increase with age-suggesting the cumulative beneficial effects of a healthy diet.
NO SAFE TIME FOR SEX
TORONTO
Women may have the ability to ovulate more than once during their menstrual cycle, according to a Canadian research published in the journal Fertility & Sterility.
The study, conducted by the University of Saskatchewan and supported by the Canadian Institutes of Health Research, could shatter a long-standing belief that women could only release an egg once during their cycle.
Previous studies have shown that between 15 and 20 follicles grow in a woman's ovaries at the start of her menstrual cycle. One of them matures and is released to be fertilized, while the others die off. But the Canadian researchers found that women actually experience a wave of this activity, with at least two to three periods of follicular development each month.
"This work is particularly exciting to us because of the impact it will have on women taking oral contraceptives and undergoing fertility treatment," said Dr. Roger Pierson, director of the university's reproductive biology research unit.
It also means "there is no 'safe' time to have intercourse during the cycle [because] there may always be a follicle capable of ovulating," he added.
Their study involved 63 women with normal menstrual cycles who underwent ultrasound testing every day for a month.
"We are literally going to have to rewrite medical textbooks," Pierson said, adding that further research is needed to see if the same number of waves occurs consistently every month and why a particular egg is selected to ovulate. Similar waves of follicular development were found in cows and horses in the 1980s.
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