India has put a group of volunteers on a year-long watch after giving them a trial vaccine against the HIV virus, marking a key phase in the search for a drug to prevent AIDS, a scientist said on Thursday.

Home to the second-largest number of people living with the killer virus after South Africa, India started giving the vaccine to 30 healthy volunteers in varying doses from February last year.

"The trials have entered the follow-up stage where they will be observed," R.S. Paranjape, deputy director of the National AIDS Research Institute, told Reuters.

During the trials healthy volunteers are given a controlled dosage of the HIV subtype C virus to create resistance. All volunteers sign on to the trial, accepting the risks of possible HIV infection.

India's trial vaccine targets this subtype, widely prevalent in India, South Africa and China.

A vaccine for the developing world, where anti-retroviral drugs are either unavailable or too expensive for millions of HIV-infected people, would be the ultimate prize in the fight against AIDS.

But efforts to find one have been hampered by the virus's ability to mutate, scientists say.

"We will begin collecting data from the volunteers after one year from this month," Paranjape said, adding that similar trials in Belgium and Germany have completed the year-long study and are waiting for the Indian scientists to catch up.

"Once the follow-up stage is over, data from volunteers in these three countries will be collated and decoded to study the result," Paranjape said.

The International AIDS Vaccine Initiative, which coordinates the global search for a vaccine, says India is important because of its advanced biomedical research facilities and a strong pharmaceutical industry which has developed cheap and effective AIDS drugs that are exported across the world.

India is also working on a second vaccine -- called the Modified Vaccinia Ankara -- that will target HIV subtype C.

The world's second-most populous country has an official HIV/AIDS caseload of more than 5 million people and experts say that number could quadruple by 2010 as many people are still reluctant to discuss safe sex openly.

Many experts say the true infection rate may be far higher than government figures suggest. Many Indians cannot afford anti-retroviral drugs which cost 1,300 rupees ($29.40) a month.

Human trials of vaccines against various strains of the HIV virus are being conducted in the United States, Europe and Africa.

An injection of two drugs normally used to treat HIV patients completely protected monkeys from becoming infected with the AIDS virus, U.S. researchers reported on Monday.

While it is too early to tell whether people can pop a pill and escape infection, the study provides the strongest evidence yet that it might be possible, the researchers said.

Dr. Walid Heneine of the Centers for Disease and Prevention studied rhesus monkeys that were injected with a version of Truvada -- Gilead Sciences Inc.'s once-a-day pill that includes its drugs Viread, or tenofovir, and Emtriva, or emtracitibine.

The pill is often used in drug cocktails to treat HIV infection, although they cannot cure it.

The monkeys were then exposed to a combined human-monkey AIDS virus called SHIV, using a rectal method aimed at simulating male homosexual contact. That happened daily for 14 days and the monkeys also got daily injections.

"Treatment continued for four weeks after last challenge," Heneine told the Conference on Retroviruses and Opportunistic Infections, a meeting of AIDS researchers being held in Denver.

The six monkeys that received the drug combination were all completely protected from infection. By comparison, nine monkeys that took part in a previous experiment all eventually became infected with the SHIV virus.

"Study authors believe the findings may be the strongest animal data yet suggesting that potent antiretrovirals given before HIV exposure may prevent sexual HIV transmission," the CDC said in a statement.

The researchers cautioned the drug dose was slightly different from that seen in people taking Truvada and said studies under way will answer the question of whether the findings will translate to humans.

Either drug taken alone prevents HIV infection for a while, but imperfectly, Heneine said.

The CDC noted that Truvada was highly effective in suppressing the AIDS virus in people already infected. It is not a cure but is among the drugs that can help keep HIV patients healthy.

It also has fewer side effects than some of the older, hard-to-take combination regimens.

Dr. Myron Cohen of the University of North Carolina at Chapel Hill said the study suggested that people who know they are at high risk of infection might be able someday to protect themselves by taking a pill.

"Adolescent women in South Africa go from having a 10 percent risk of HIV infection to a 30 percent risk in a matter of two years," said Cohen, who was not involved in the study. "This is a big epidemic that is not going away."

In emerging nations, young women have the highest risk of becoming infected with HIV, often by husbands or boyfriends who refuse to use condoms.

In richer countries, women are also at risk, as are men having sex with other men and injecting drug users. Cohen said these groups may also benefit from taking prophylactic doses of HIV drugs.

U.S. President George W. Bush's administration stresses abstinence as the best way to avoid AIDS, but Cohen and other experts said if the epidemic is to be stopped, people should make decisions based on science, rather than moral or emotional judgments.

"There are many other examples of people taking medications to protect themselves from disease," Cohen said.

When it comes to fighting the AIDS virus, the sooner patients start taking powerful drug cocktails, the better -- even when it comes to side-effects known as toxicities, U.S. researchers reported on Tuesday.

Deaths, the rate of opportunistic infections and side effects all were the lowest in patients who started treatment early -- while their immune systems were still relatively intact, the team at the University of Colorado Health Sciences Center and the Centers for Disease Control and Prevention found.

"Earlier was better in almost everything we looked at," said Dr. Kenneth Lichtenstein of the University of Colorado.

"If you stayed on treatment and started earlier, you had the best outcomes," Lichtenstein said in an interview.

He said current guidelines that recommend delaying therapy are based on incorrect assumptions that starting drugs early worsens toxicity, because his study found that early treatment reduces toxic side-effects.

Lichtenstein and colleagues used the medical records of 2,304 HIV-positive patients in eight U.S. cities who were part of a larger HIV Outpatient Study between 1996 and 2005.

They looked for three common treatment-related toxicities -- kidney insufficiency, a type of nerve damage known as peripheral neuropathy, and a form of wasting known as lipoatrophy.

They broke the patients down into five groups based on the number of CD4 T-cells they had -- known as the CD4 count. As HIV infection worsens, the virus attacks these immune cells and the count goes down.

All the patients were on drug cocktails known as HAART or highly active antiretroviral therapy. These three and four drug mixes can keep patients healthy if taken properly.

HIGHER CELL COUNTS

Patients are generally told to start HAART at a CD4 cell count of 200 or below. But some patients started treatment with cell counts of 350, 500 or higher.

Those patients who started treatment at CD4 counts above 350 were at least 60 percent less likely to develop kidney insufficiency, 30 percent less likely to have peripheral neuropathy, and 60 percent less likely to develop lipoatrophy than patients who started at a CD4 count of 200 cells or below, the researchers told the Conference on Retroviruses and Opportunistic Infections.

Lichtenstein said it appeared the drug was the most active in and around cells when there were the fewest CD4 cells.

Inflammation seems to be an important factor, he said. "The state of inflammation associated with disease brings up the toxicity," Lichtenstein said.

This suggests there is no reason to delay HAART treatment, and no reason to delay getting tested for HIV, Lichtenstein said.

Drug companies have simplified the regimens so that patients can often take just two pills a day. In the past patients often had to juggle 20 pills, taken at specified times of day, some with meals.

The side-effects also were debilitating, ranging from diarrhea and nausea to serious organ damage.

And there were fewer choices of drugs, so patients often were wise in hesitating to start therapy until they really "needed" it, because if the virus became resistant to a drug, a patient had few others to turn to.

"Now there are four classes of drugs, soon to be five classes," Lichtenstein said. These include the old-line reverse transcriptase inhibitors, such as AZT, the protease inhibitors, the non-nucleoside reverse transcriptase inhibitors, fusion inhibitors and entry inhibitors.

They all attack the virus at different points of its life cycle. None destroy it but they can suppress it almost completely if taken in the right combinations.

Which particular kind of HIV virus an AIDS patient has may be more important than other factors in how quickly death comes, U.S. and Ugandan researchers reported on Monday.

They found that people infected with a clade, or subtype, of HIV called D died more quickly that those with infections from the A clade.

Clade was a better predictor than viral load -- how much virus can be found in a patient's blood -- of rapid death from AIDS, the researchers told a conference.

"Knowing a person's HIV subtype is important for the management of the infection because the disease can progress more rapidly in those infected with subtype D ... than in those with other subtypes," said Oliver Laeyendecker, a senior research associate at The Johns Hopkins University School of Medicine who led the study.

If an HIV patient is fortunate enough to have medical care, DNA testing to determine clade may be an important part of that care, the researchers said.

More than 40 million people are infected with the incurable and fatal human immunodeficiency virus. HIV killed more than 3 million people in 2005 and infected 5 million new patients, according to United Nations.

Africa is by far the worst-hit continent.

GEOGRAPHICAL BOUNDARIES

The virus has mutated into nine clades that correspond to rough geographical boundaries. Clades A and D are common in Uganda, for instance, while clade C circulates in Botswana, South Africa, India and parts of China. Clade B is common in Europe and the United States.

Researchers are not certain yet if clade is important for making vaccines against AIDS.

Laeyendecker, Dr. Maria Wawer, Dr. Thomas Quinn and colleagues were studying the Rakai cohort, a group of 12,000 people in Uganda. The volunteers get annual blood tests, so researchers know when each patient becomes infected and can track the pattern of the epidemic in Uganda.

They concentrated on 300 men and women newly infected between 1995 and 2001. Of them, 53 were infected with clade A HIV and 203 infected with clade D. Another 70 were infected with a virus that had mixed genetic lineages of A and D.

Ten percent of those infected with subtype D died within three years, while none with subtype A died that quickly, the researchers told the Conference on Retroviruses and Opportunistic Infections in Denver.

On average, the people infected with A lived 8.8 years, those with D lived 6.9 years and those with the A-D mixture lived just 5.8 years.

VIRAL LOAD

In richer countries doctors usually keep track of HIV by measuring viral load. Current drug cocktails that help control HIV infection suppress the load to very low levels, and patients usually start to become ill if it goes up.

But in the Rakai cohort, viral load varied greatly and was not a good predictor of who died the soonest, the researchers said.

The Johns Hopkins team said clade D may be more virulent than A because D uses multiple doorways, called receptors, to get into human immune cells called T-cells that it infects.

Clade A HIV uses only one receptor called CCR5, to infect T-cells. But the researchers found that 25 percent of clade D virus also used a receptor called CXCR4. Two-thirds of the patients whose virus used CXCR4 died within three years, the researchers said.

An earlier study done in Senegal found that women with clade C, D, or G infections were more likely to progress to AIDS within 5 years of infection than women with subtype A.

Male circumcision, which has been shown to protect men from infection with the AIDS virus, appears to protect women, too, U.S. and Ugandan researchers reported on Wednesday.

Circumcising men reduced infections in their female partners by 30 percent, the researchers found. One said the difference may be related to the structure of the foreskin, which is removed in circumcision.

In the study of more than 300 Ugandan couples in which the man infected the woman, the researchers found that 299 women caught HIV from uncircumcised partners and only 44 were infected by circumcised men.

Circumcision also reduced the risk of infection with other sexually-transmitted diseases such as trichomonas and bacterial vaginosis, but not syphilis, gonorrhea or chlamydia, the researchers told an AIDS meeting in Denver.

Dr. Thomas Quinn of Johns Hopkins University in Baltimore has been leading a team that studies 12,000 volunteers in Rakai, Uganda. They have been studying transmission of the human immunodeficiency virus that causes AIDS.

Last year they reported that circumcised men were less likely to become infected with HIV. Now, they told the Conference on Retroviruses and Opportunistic Infections, it appears that among infected men, circumcision reduces the likelihood they will transmit the virus through sex.

They also presented more evidence that circumcision protects men. They reanalyzed previous studies and found that circumcision reduced the risk of HIV infection in men by 50 percent -- and by 70 percent in the highest-risk men.

The findings will have to be confirmed in other groups before being used as the basis for recommendations, Quinn said. However, he said, "early indications are dramatic." If borne out, for every 15 to 60 circumcisions, one case of HIV infection could be prevented, he said.

Circumcision's benefits may stem from the structure of the foreskin of the penis. Its inner lining, or mucosa, carries cells that are vulnerable to the AIDS virus.

"Also that mucosal layer does not have the thick keratin (skin) that the outside skin of the foreskin has," Oliver Laeyendecker, who worked on the study, said in an interview.

"Not only do you have more virus there because of the types of cells that are there, but the barrier is easier to go through from the man to the woman on that skin surface because it doesn't have to go through a lot."

The AIDS virus is transmitted by semen, blood and breast milk and via sex, shared needles or other contacts with infected blood.

Semen can transmit the virus, but levels in the semen drop over time, while remaining elevated in the blood, Laeyendecker said.

The theory is that the virus can pass in tiny amounts of blood in the foreskin. "Because of the nature of that membrane, because it is thin, because it is susceptible to micro-tears, you have a lot of openings," Laeyendecker said.

"Plus you have more cells with virus there, so it lends itself to being a more transmissible surface."

The AIDS virus infects close to 40 million people globally, most of them in Africa. It kills 3 million people a year and infects 5 million new people every year.

It is eventually fatal and there is no cure or vaccine, although drug cocktails can keep patients healthy for years. Laeyendecker said the Uganda volunteers have access to at least some of the drugs through a U.S. program.

The drug nevirapine prevents the spread of the AIDS virus from mother to child time after time, a new study suggests, challenging earlier findings.

The new research presented Wednesday at a scientific meeting in Denver found that in Ugandan women who received the drug during a first pregnancy, HIV transmission was prevented during second pregnancies as well.

The research may ease concerns raised in previous studies that HIV develops resistance to the drug, said Dr. Michael Thigpen, a medical epidemiologist with the U.S. Centers for Disease Control and Prevention.

"Based on these findings, we believe nevirapine in repeat pregnancies remains an effective option in these resource-limited countries," said Thigpen, who is part of the research team.

The study looked at 198 women treated in 2004 and 2005 at a hospital in Kampala, Uganda.

Nevirapine is an inexpensive and easy-to-take medication that has become a mainstay in the effort to prevent mother-to-child HIV transmission in poor countries. Proponents say the drug cuts the transmission risk in half.

Mothers receive a pill when they go into labor, and their newborns get the medication in a syrup within 72 hours of birth.

The drug came into question in earlier studies done in South Africa and Uganda, which found that 20 percent to 40 percent of HIV-infected women developed resistance to nevirapine after taking one dose to protect their newborns from getting the infection.

The new research found that the HIV infection rate was 14.6 percent for babies born to nevirapine-treated women who also took the drug during a previous pregnancy. The rate was 17.6 percent for nevirapine-treated women who were not given the drug during an earlier pregnancy.

The research is good news, said Mark Isaac, a vice president for the Elizabeth Glaser Pediatric AIDS Foundation, which funds HIV/AIDS research and worldwide treatment programs.

A study of multiple pregnancies in South Africa and Ivory Coast, also announced Wednesday, produced similar results. Three other studies showed low risks of nevirapine resistance in women who took the medicine more than a year after the initial dose.

"It's fair to say we're breathing a sigh of relief," Isaac said.

Thigpen said there are different subtypes of HIV, and one that circulates in southern Africa appears especially resistant to nevirapine.

"In Uganda, there are a couple of different subtypes. That (fact) may limit our ability to associate these findings with other areas of Africa," Thigpen said, referring to his study's findings.

Pediatricians should speak out in support of needle exchange programs to reduce the spread of HIV among injection drug users, the American Academy of Pediatrics says in a toughened policy statement.

Doctors also should discuss HIV risk with their teenage patients "with a nonjudgmental approach" and offer confidential help if local laws allow, the group says in the statement appearing Monday in the journal Pediatrics.

"If we can help young people avoid a chronic illness that we have no cure for, I would hope people would embrace that idea," said the lead author, Dr. Lisa Henry-Reid of Chicago's John H. Stroger Jr. Hospital.

The previous version of the group's policy, dated 1994, said clean needle programs should be "encouraged and expanded."

Half of new HIV infections in the United States are among people younger than 25, Henry-Reid said.

Unprotected sex is the most common way young people become infected, but sharing dirty needles or having sex with an injection drug user accounts for about 13 percent of youth AIDS cases.

The policy drew criticism from Wendy Wright of Concerned Women for America, the group that last year blasted the pediatricians' academy for its support of over-the-counter emergency contraception.

"The recommendation will not rescue patients and neither does it promote healthy behavior," Wright said. "Instead, they have been promoting programs that encourage riskier activities."

The new policy statement says of needle exchange programs, which let addicts trade dirty syringes for clean ones: "Pediatricians should advocate for unencumbered access to sterile syringes and improved knowledge about decontamination of injection equipment."

The beefed-up wording is based on research showing the programs reduce HIV infection, said Dr. Peter Havens of the Medical College of Wisconsin, a member of the committee that wrote the policy. Needle exchange programs can include counseling to further reduce risky behavior, but opponents say they work against efforts to fight drug abuse.

Congress has banned federal funding of needle exchange programs, but the Centers for Disease Control and Prevention says they can reduce the spread of disease without increasing drug use.

Thirty-six states and the District of Columbia have needle exchange programs, according to the nonprofit North American Syringe Exchange Network.

A particularly bad strain of chlamydia not usually seen in this country appears to be slowly spreading among gay and bisexual men, an infection that can increase their chances of getting or spreading the AIDS virus.

Called LGV chlamydia, this sexually transmitted disease has caused a worrisome outbreak in Europe, where some countries have confirmed dozens of cases. Diagnoses confirmed by U.S. health officials still are low, just 27 since they warned a year ago that the strain was headed here.

But specialists say that's undoubtedly a fraction of the infections, because this illness is incredibly hard to diagnose: Few U.S. clinics and laboratories can test for it. Painful symptoms can be mistaken for other illnesses, such as irritable bowel syndrome.

And because LGV chlamydia doesn't always cause noticeable symptoms — right away, at least — an unknown number of people may silently harbor and spread it, along with an increased risk of HIV transmission.

"My feeling is that what we're seeing now is still the tip of the iceberg," says Dr. Philippe Chiliade of the Whitman-Walker Clinic in Washington, D.C., which diagnosed its first few cases of LGV last month and is beginning to push for asymptomatic men to be screened.

The Centers for Disease Control and Prevention already was counting an 8 percent increase in HIV among gay and bisexual men between 2003 and 2004, before LGV's arrival was recognized.

"We are really concerned about this," says Dr. Catherine McLean of CDC's HIV and STD prevention program.

Increasing the ability to test for LGV is "what's really critically important," she adds. "The prevalence of the disease is probably quite a bit higher than the reported cases indicate, either here or in Europe, but we don't yet know that."

Three weeks of the antibiotic doxycycline effectively treats LGV. But patients have to know they're at risk, and then find a test.

Chlamydia, caused by bacteria, is among the most common sexually transmitted diseases. As many as 3 million Americans a year may become infected with common strains, best known for causing infertility in women if left untreated.

This more virulent strain is called "lymphogranuloma venereum," or LGV. It's not a new form, but one rarely seen outside of Africa or Southeast Asia. So STD specialists were stunned in late 2004, when the Netherlands announced an outbreak that reached over 100 cases; last summer, one clinic there reported seeing one to two new patients a week. Cases also have surfaced in much of Western Europe and Britain. As with the U.S. cases, many also have HIV.

Symptoms differ from regular chlamydia: swollen lymph nodes in the groin; genital or rectal ulcers; and painful bowel movements and other gastrointestinal symptoms that may mimic inflammatory bowel disease. Such symptoms leave patients particularly susceptible to HIV infection if they also encounter that virus.

LGV can infect both sexes, although new cases diagnosed so far are among men having sex with men.

Screening requires nucleic acid testing, a complex type of genetic testing not yet commercially available for rectal use. The CDC then uses even more sophisticated testing to confirm the diagnosis.

Because testing is difficult, no one knows how prevalent LGV truly is. In a surprise finding last fall, Dutch scientists tested some tissue samples stored in San Francisco since the 1980s, and found evidence that today's LGV strain had gone unrecognized at the time. So has it been simmering here all along, or is it on the rise?

Regardless of how that question turns out, LGV is one more sexually transmitted illness that plays a role in HIV.

Thus, the CDC is encouraging doctors who spot LGV symptoms to contact their local health department for help in finding a nearby testing lab, or in shipping samples to CDC for testing there.

"But I don't want people to think you have to have severe pain," cautions Chiliade, whose clinic recently became authorized to offer the NAT rectal screening — and who recommends it for gay men who have had unprotected sex even if they feel no symptoms.