Boston Trial to Test New HIV/AIDS Vaccine

(HealthDay News) -- A new HIV/AIDS vaccine designed to overcome the problem of preexisting immunity to common vaccine vectors is being tested in an early clinical trial at Brigham and Women's Hospital in Boston.

Preexisting immunity is believed to be a major problem in developing nations.

There will be 48 healthy volunteers taking part in the trial of the vaccine, which consists of a replication-incompetent, recombinant adenovirus serotype 26 (rAd26) vector encoding an HIV-1 envelope gene.

Each volunteer will receive either two or three immunizations, and then be monitored to assess the safety of the vaccine and its ability to trigger an immune response.

The rAd26 vaccine was developed by the Integrated Preclinical/Clinical AIDS Vaccine Development (IPCAVD) program, sponsored by the U.S. National Institute of Allergy and Infectious Diseases. The program brings together academic and industry researchers to accelerate development of promising HIV/AIDS vaccine candidates.

The vaccine, the first HIV-1 vaccine candidate to emerge from the IPCAVD program, is made by Dutch biotechnology company Crucell Holland B.V.

The approach used in developing the rAd26 vaccine enables researchers to circumvent preexisting immunity to serotype 5, the virus responsible for the common cold. This virus has recently shown limitations as an HIV-1 vaccine vector.

"The rAd26 vector does not regularly occur in the human population, and human antibodies to this vector are rare. The rAd26 vector therefore is efficacious in eliciting good T and B (immune) cell responses," Jaap Goudsmit, chief scientific officer at Crucell, said in a prepared statement.

About 33.2 million people worldwide are living with HIV/AIDS, and there were 2.7 million new infections reported in 2007.

More information
Currently, there is no vaccine to protect against HIV/AIDS. The American Academy of Family Physicians offers tips for preventing HIV infection.

Testosterone Therapy May Reduce Bone Loss in Older Men

(HealthDay News) -- Injections of testosterone appear to improve bone density and reduce bone loss in older men who have low testosterone levels and may help to prevent osteoporosis, a new study suggests.

Testosterone therapy has been used to improve bone strength and muscle mass in some men. However, the hormone treatment is controversial, because it has been associated with increasing the risk of prostate cancer and high levels of red blood cells. And other potential effects of long-term use of testosterone therapy aren't known.

"These preliminary data show beneficial effects of testosterone therapy on bone turnover markers in older men with low-to-normal testosterone concentrations using both continuous and monthly cycled testosterone replacement," lead researcher E. Lichar Dillon, of the Department of Internal Medicine at the University of Texas Medical Branch in Galveston, said in a prepared statement. "The effects of sex hormones on markers of bone formation are complex, but this is an important step in understanding how the process works."

Preliminary study results were expected to be presented April 7 at the American Physiological Society's annual meeting, during the Experimental Biology 2008 conference, in San Diego.

For the study, Dillon's team studied 13 men, ranging in age from 60 to 85. During the five-month trial, the men were either given weekly injections of testosterone, weekly injections of testosterone every other month, or a placebo.

The researchers found that men receiving testosterone had reduced bone turnover, compared with men on a placebo. While the effects of testosterone therapy over the long term aren't clear, the researchers said they believed the treatment would be beneficial by preserving bone mass and preventing osteoporosis.

One expert said the study was too small to prove or disprove the value of testosterone therapy in preventing bone loss and, perhaps, preventing osteoporosis.

"This small, short-term study indicates that men with low levels of testosterone respond to appropriate replacement as far as turnover markers indicate," said John Eisman, director of the Bone and Mineral Research Program at the Garvan Institute of Medical Research, in Sydney, Australia.

While calling the study "too small and too short to provide any insight into fracture-risk reduction or safety outcomes," Eisman said it does complement research he has done. "Our study showed that men with testosterone in the lowest quartile of the population had much higher risk of osteoporotic fractures," he said.

A large, long-term trial testing whether testosterone can prevent osteoporosis in men is needed to settle the question, Eisman said.

More information
To learn more about men and osteoporosis, visit the U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Eating Less May Hinder Immune System

(HealthDay News) -- You may no longer need to remember whether it's "starve a cold, feed a fever" or vice versa. New research suggests you should just eat.

A study of deer mice has found that reducing the amount of food the mice ate impaired their immune system. The findings are published in the May/June issue of Physiological and Biochemical Zoology.

The researchers found that decreasing the amount of food the mice ate by 30 percent significantly decreased the number of B cells in their systems. B cells produce antibodies and maintain immune memory, so an immune system lacking B cells must relearn how to fight infection and disease.

"A 30 percent restriction in food intake doesn't affect body mass and only minimally reduces activity in deer mice, but it eliminates the long-term immune protection provided by antibodies," study co-author Lynn Martin said in a prepared statement. "One wonders whether similar moderate food restriction has comparable immune effects in humans."

Martin and fellow researchers cited previous studies that had found that infections were "more frequent and tend to be chronic in malnourished children." Previous studies have also found that vaccines that provoke B cells to protect the body long-term, such as the vaccine for measles, are less effective among the malnourished.

The authors proposed that future research should be done to learn what specific features of diet (calories, protein, micronutrients) affect immune system function.

More information
The U.S. National Institute of Allergy and Infectious Diseases has more on how vaccines work.