HealtyDayS

 Researchers at the University of Minnesota have identified a protein that enables viruses such as HIV to infect cells and spread through the body.

This discovery gives drug developers a target to discover new types of drugs to stop the virus from spreading.

The research, led by Nikunj Somia, Ph.D., assistant professor of Genetics, Cell Biology and Development, will be published online this week in the Proceedings of the National Academy of Sciences, and will appear in a subsequent print edition of the journal.

HIV is a parasite that does not have enough proteins of its own to complete its life cycle. To survive, the virus needs to use proteins in the cells that it infects.

Currently, the drugs that are available to fight HIV act on proteins that the virus itself produces.

“The downfall of existing HIV drugs is that since the virus is constantly changing, the drugs eventually stop working, and the virus becomes drug resistant,” Somia said. “We hypothesized that if we could find the proteins within the cells that HIV uses to make more copies of itself, we would find a potential new and more effective way to fight HIV.”

To begin their search for these proteins, they first induced mutations in cells through chemical manipulation; this made random mutations in the DNA of the cell lines. Then they altered HIV so it contained a protein that immediately kills cells, and infected the different mutant cell lines.

The Somia laboratory found that some cell lines lived after being infected with HIV. In the cell lines that live, the HIV is able to get into the cell, but it is attacked. The cell’s proteasome, a “machine” in the cell that destroys or chews up proteins, attacks the virus, preventing it from making more copies of itself.

Proteasomes are signal dependant machines in the cell, and proteins are typically “tagged” to be destroyed.

“Finding the switch that turns on the proteasome machine in cells to seek and destroy the virus could be a powerful therapeutic agent in the fight against HIV and in controlling AIDS,” Somia said.

 HIV in the Middle East and North Africa: a review of the evidence

A review of research on the prevalence of HIV in the Middle East and North Africa has found that whilst cultural and religious practices may be behind a low prevalence of HIV in the region, they could potentially contribute to increasing the spread of HIV.

Research from the World Health Organisation, published in this week’s BMJ, argues it is possible that some practices which are common among Muslim populations may contribute to decreasing the risk of HIV transmission. One is low alcohol consumption, which reduces ‘risky’ behaviours and another is potentially male circumcision which was shown in a recent clinical trial to have a protective effect but application of these results to other epidemiological, cultural and social settings still needs to be confirmed.

At the same time other population trends, beliefs and practices in the region may have an adverse effect. Most countries in the region have young populations with a rapidly increasing age at marriage, but young people may be ill-equipped to protect themselves against sexually transmitted infections. Traditional Muslim approaches have tended to be very conservative, and it is difficult to break the silence around issues of sexual behaviour - especially those which deviate from religious norms.

A detailed analysis of religious publications and doctrinal pronouncements revealed that strong moralising views were common – HIV was seen as divine retribution and religion was presented as a protection. This can mean that those with HIV/AIDS are stigmatised.

The construction of gender also plays a part - strong prohibitions against extramarital sex, which are applied more strictly to women, are associated with lower HIV prevalence. While there are fewer women than men with HIV in the region, this sex ratio appears to be shifting, suggesting the disease is spreading and highlighting women’s special vulnerability as they are married to older men who are more likely to have been exposed to HIV infection. The cultural view that women are innocent reinforces the lack of information about sexual risk and makes it difficult for women to protect themselves.

The author notes that ‘a theology of compassion and approaches advocating harm reduction seem to be emerging in several Muslim countries, and greater acceptance of HIV positive people is justified with reference to religion. Things are also improving on a practical level - in recent years better information systems to track HIV have been put in place in the region and around half of the countries have formulated national plans to tackle HIV.’

The author concludes that whilst knowledge is still inadequate and stigma and greater discrimination prevail in many settings, over the past couple of years ‘there has been greater visibility and more public discussion of HIV/AIDS in the region. Throughout the region governments and non-governmental organisations have initiated promising projects to break the silence around HIV, spread information, promote prevention and provide care and treatment. The challenge now is how to capitalise on the strengths represented by cultural tradition while fostering effective responses to the epidemic.’

 One fifth (20 per cent) of women aged 16-49 had undergone a test for Chlamydia at some point in the past, of whom 27 per cent had done so in the previous year, according to a new report published by the Office for National Statistics (ONS).

Awareness of Chlamydia is increasing. The proportion of people who recognised that it is a sexually transmitted infection (STI) has increased sharply since the question was first asked in the 2000/01 survey – from 35 per cent to 79 per cent of men and from 65 per cent to 91 per cent for women.

Young women were most likely to have had a test for Chlamydia (31 per cent of 16-29 year-olds had been tested in the past compared with 20 per cent of 30-39 year olds and 11 per cent of 40-49 year olds.).

Women who had had more than one sexual partner in the past year were also more likely to have had a test (43 per cent compared with 20 per cent of those who had had just one partner).

Those who knew Chlamydia was an STI were asked five questions about the symptoms. Women were twice as likely as men to give correct responses to all questions (38 per cent compared to 18 per cent).

This report presents the results of a survey on contraception and sexual health carried out by the ONS in 2005/06 on behalf of the Information Centre for health and social care. Questions were addressed to women aged 16-49 and men aged 16-69.

Contraceptive use in women aged under 50

The majority (74 per cent) of women aged under 50 were using contraception. The most popular method was the contraceptive pill (24 per cent) followed by the male condom (21 per cent) - both methods were more popular among younger women.

Ten per cent of women under 50 had been sterilised (18 per cent of men under 70 had undergone a vasectomy). Sterilisation was more common among women with no qualifications than among those with qualifications.

Twenty-six per cent of women under 50 were not currently using a method of contraception (14 per cent were not in a sexual relationship with someone of the opposite sex).

Among women in a heterosexual relationship, the main reason that women did not use contraception was because their partner had been sterilised (55 per cent). The next most common reason was actual or planned pregnancy (21 per cent).

Emergency contraception

Condom failure was most common reason why hormonal emergency contraception (the morning after pill) was used (45 per cent) followed by forgetting to take the oral contraceptive pill (22 per cent).

Five per cent of women had used emergency hormonal contraception in the year before interview. Of these women, 45 per cent had obtained it directly from a chemist or pharmacy, 30 per cent from their own GP or practice nurse and 24 per cent from a family planning clinic.

Condom use

Forty-one per cent of men and 46 per cent of women said they had used a condom in the previous year. Condom use was most common among men who had had more than one sexual partner in the past year and among those with degree level qualifications.

Ninety per cent of women who used a condom said the reason was to prevent pregnancy and 43 per cent cited preventing infection, compared with 88 per cent and 47 per cent of men respectively. (People could give more than one reason).

Sexual behaviour

Sixteen per cent of men aged under 70 had had no sexual partners in the previous year, 73 per cent had had just one partner and 12 per cent had had more than one.

Twelve per cent of women aged under 50 had had no sexual partners in the previous year, 81 per cent had had just one partner and seven per cent had had more than one.

Knowledge of sexually transmitted infections Just over half of men and women reported making no changes to their behaviour as a result of what they had heard about HIV/AIDS and other STIs. However, 37 per cent said they had increased their use of condoms, nine per cent had fewer one night stands and three per cent had a test for STIs.

Television programmes were the most commonly mentioned source of information about STIs (32 per cent), followed by television advertisements (21 per cent) and newspapers, magazines or books (21 per cent).

HIV Care

In a first-of-its-kind study, UCLA researchers have shown that segments of the HIV-infected population who have little to no consistent outpatient medical care - and yet are most in need of such services - are overwhelmingly minorities, the poor and substance abusers.

Previous studies had shown minorities, the poor and substance users who were receiving routine medical care for the HIV infection, and whose data could therefore be easily captured in healthcare studies, were likelier to be medically underserved and to die more quickly. But Dr. William Cunningham, and the study’s lead author, said UCLA researchers tracked HIV-infected people who were not receiving regular care - and thus more difficult to find. Often this segment showed up in the medical system in emergency situations.

“As we expected, they are much less likely to get routine outpatient care but more likely to get acute care, when they are at their sickest,” said Cunningham, who is professor of medicine in the Division of General Internal Medicine and Health Services Research at the David Geffen School of Medicine at UCLA. “This is just the group that needs to get grassroots outreach service.”

For this study, to be published in the November issue of the journal Medical Care, the researchers compared socio-demographic, clinical and health care utilization characteristics of HIV-infected adults from two samples: 1,286 people from the 2001-02 Targeted HIV Outreach and Intervention Initiative (Outreach) and 2,267 who were interviewed in 1998 for the HIV Costs and Services Utilization Study (HCSUS).

Outreach, a multi-site program initiated in 2001 under the Ryan White Care Act, was intended to locate HIV-infected people who are hard to reach and connect them with medical care. HCSUS focused on HIV-positive patients who were receiving care. The 16 Outreach study sites, which were spread throughout the U.S., offered a variety of services such as HIV testing and counseling, social services, case management and direct medical care. They all provided outreach services linking HIV-positive patients with continuous outpatient care. The researchers examined the demographic data, the kinds of medical services the patients used and which services would be the most helpful to them.

According to the study, 59 percent of patients in the Outreach group were black, compared with 32 percent of HIV-infected people who were receiving routine care and were tracked by HCSUS. Also, 20 percent of those from the Outreach sites were Hispanic versus 16 percent from the HCSUS sample; 9 percent were Spanish speakers compared to 2 percent; 75 percent had annual incomes of $10,000 or less compared with 45 percent; and nearly 60% were unemployed, homeless, had no insurance or used heroin or cocaine compared with less than half in the HCSUS study.

Additionally, people from the Outreach group received medical care on an outpatient basis two times or less, but were likelier to have gone to emergency rooms or been hospitalized, during the prior six months. They were also less likely to be on antiretroviral drugs. And surprisingly, these patients were also more likely to have abused alcohol than drugs.

The findings can be used to develop novel interventions specifically tailored to this group, such as mobile HIV testing facilities and bringing HIV treatment to single occupancy hotels, which are typically home to drug abusers, sex workers and other marginalized people.

“Because we did this study, we know better what kind of services to tailor to them,” Cunningham said. “They’re not the same kind of services that are important to more mainstream patients.”

Male Contraceptive Pill

The development of effective, reversible, and safe contraceptives for men has lagged far behind the availability of methods for women, largely because scientists lack sufficient knowledge about male reproductive physiology. Improving this state of affairs has been a key aim of scientists at the Population Council’s Center for Biomedical Research. In one of the Council’s labs, biochemist and cell biologist C. Yan Cheng and his colleagues have found a way to target a new drug, known as Adjudin, to the testis in rats. This method induces reversible infertility without interfering with hormones secreted by the hypothalamus, pituitary gland, and testis.

“The hormones of the hypothalamus pituitary-testicular axis regulate male sex drive and maintain the health of other targets, including bone, muscle mass, and the sex organs. Male contraceptives that bypass this hormonal system would be welcome because they would be likely to leave these organs and libido intact,” says Régine Sitruk-Ware, executive director of product research and development at the Center for Biomedical Research.

Cheng’s strategies target the attachment of germ cells onto Sertoli cells in the testis. A disruption of germ cell attachment leads to the premature release of germ cells, and the net result is infertility.

Cheng was first put on the trail of one compound, AF-2364, through the work of a colleague, Professor Bruno Silvestrini at the University of Rome, who was studying an anticancer drug, lonidamine. One side effect of lonidamine was a temporary, profound disruption of spermatogenesis. Because of its toxic side effects, lonidamine could not be used as a contraceptive. However, Cheng speculated that if he could synthesize nontoxic analogs of lonidamine, they might work as a male contraceptive. AF-2364, now known as Adjudin, is one such analog that was shown to induce germ cell depletion from the testis using assays established by Dr. Dolores Mruk in the laboratory.

Adjudin interferes with the adhesion of germ cells to the supportive Sertoli cells that surround them. When this attachment is disrupted, germ cells are released before they mature and become capable of fertilizing an egg. Cheng’s research has shown Adjudin to be a potent, effective, and reversible male contraceptive in laboratory animals. Normal fertility returns a few months after treatment with Adjudin stops. The compound does not influence the hypothalamus-pituitary-testicular axis.

When Adjudin was given to animals at a high dose orally, however, it caused liver inflammation and muscle atrophy in a small subset of animals. Chang and his colleagues then set out to develop a way of delivering the drug directly to the testis at a lower dose, so that it would not interfere with these other systems. One hurdle they needed to surmount was the fact that the testes are protected by a blood-testis barrier created by the protective Sertoli cells. This blockade prevents immune system cells and foreign substances from entering the testis and damaging sperm.

They overcame the blood-testis barrier by means of a chemical Trojan horse. They attached Adjudin to a version of the follicle-stimulating hormone (FSH). The only FSH receptors in the male body are in the testis. The attachment of FSH delivered the Adjudin directly to the area of the body it was needed, the testis, and also allowed the drug to slip through the blood-testis barrier unnoticed. Using this new approach, the researchers induced infertility in rats using relatively low doses of Adjudin. There were no obvious side effects.

Since the new drug would have been broken down by the body if taken orally, instead it was injected into the rats. Frequent injections would be unacceptable to men, so the researchers are considering other possible delivery systems, such as implants or patches.

“These results show that a class of male contraceptives with potentially few side effects can be developed by interfering with cell-to-cell attachments in the testis,” says Cheng. Cheng’s study appeared in a Nature Medicine paper published online on 29 October 2006.

 Kaye Wellings (London School of Hygiene & Tropical Medicine) and colleagues analysed data from 59 countries worldwide, which included information on age at first sexual experience, condom use, and number of sexual partners.

They found that contrary to popular beliefs, there has in fact been no universal trend towards earlier sexual intercourse. Almost everywhere, sexual activity begins for most men and women in the later teenage years (ages 15–19 years), with earlier onset for men and later for women.

Monogamy is the dominant pattern in most regions of the world. Despite substantial regional variation in the prevalence of multiple partnerships most people report having only one recent sexual partner.

Surprisingly, the study found that it is developed nations that report comparatively high rates of multiple partnerships, not those parts of the world which tend to have higher rates of sexually transmitted infections and HIV, such as African countries. This suggests that social factors such as poverty, mobility and gender equality may be a stronger factor in sexual illhealth than promiscuity.

Married people have the most sex but a trend towards later marriage in most countries has led to an increase in the prevalence of premarital sex. The analysis found that sexual activity among young single people tends to be sporadic, but is more common in industrialised countries than in developing countries, and is more likely to be unprotected than among older unmarried people. As a result, adolescents have high rates of unintended pregnancy, unsafe abortions, and STIs.

In some developing countries, rates of condom use at last sexual intercourse are increasing; in the case of Uganda, strikingly so. Overall, however, rates of condom use are predictably lower in non-industrialised countries. This is likely to be due to the poor access and provision of sexual health services, say the authors.

Professor Wellings concludes: “Men and women have sex for different reasons and in different ways in different settings. This diversity needs to be respected in a range of approaches tailored to whole societies, and to particular groups and individuals within them… The comparative data are important in countering misinformation and quelling fears relating to sexual behaviour. The selection of public-health messages needs to be guided by epidemiological evidence rather than by myths and moral stances.”

 Sexual and reproductive health for all is an achievable goal - if cost-effective interventions are properly scaled up; political commitment is revitalised; and financial resources are mobilised, rationally allocated, and more effectively used, write Mahmoud Fathalla (Assiut University, Egypt) and colleagues.

Scaling-up cost effective interventions

• Interventions need to be tailored to the local context; there’s no magic bullet solution.

• Focus is needed on the modification and building of basic health-care systems, especially in rural areas.

• Training of health personnel other than physicians is needed because of the current human resource crisis.

• Non-governmental organisations have a key role to play; they can move more quickly and less clumsily than governments.

• HIV/AIDS services need to be linked with sexual and reproductive health services Revitalisation of political commitment.

• NGOs are well placed to present evidence to policymakers.

• Economic arguments about the benefits of good sexual reproductive health are the way forward in the competition for scarce resources.

Unsafe Sex and Health

The first-ever global study of sexual and reproductive health - to be published in the medical journal The Lancet starting this week - shows a picture of declining financial support, increased political interference and an overall reluctance to tackle threats to sexual and reproductive health.

The evaluation, coordinated by the World Health Organization (WHO), shows that the level of disability and premature death due to sexual and reproductive health is huge and increasing. Unsafe sex is the second most important cause of illness and death in developing countries and ninth in developed countries.

The analysis reveals a picture of growing unmet needs and neglect. More than half a million women die as a result of complications in pregnancy and childbirth every year. Access to contraception has increased worldwide but there are still an estimated 120 million couples who do not get the contraceptives they would like or need. An estimated 80 million women have unintended or unwanted pregnancies each year. 45 million end in abortion. WHO figures quoted in the survey show that there are 19 million unsafe abortions carried out each year, resulting in around 68 000 deaths and millions of injuries and permanent disabilities.

“These statistics represent an appalling catalogue of human tragedy,” says Joy Phumaphi, WHO Assistant Director-General for Family and Community Health. “Far from making progress we seem to have been going backwards since the notion of reproductive health was born in Cairo in 1994. The issue is dropping down the international agenda and governments seem to be reluctant to tackle this most fundamental threat to health and well-being.”

Several examples of this decline are quoted in the study. Between 1995 and 2003, donor support for family planning fell from US$ 560 million to US$ 460 million. According to the survey, family planning services in Africa need an extra US$ 70 million just to achieve the mid range of fertility projections recommended by the United Nations. Additionally, funding for contraceptive development has declined compared to microbicide research for HIV/AIDS. As well as surveying the statistical evidence on the increase in sexual and reproductive ill-health, the series highlights the importance of understanding sexual behaviour.

The survey of data from 59 countries shows that contrary to common belief, there is no universal trend to earlier first sexual intercourse. However, later marriages mean that there are more opportunities for premarital sex which is resulting in high rates of unintended pregnancy, unsafe abortions and sexually transmitted infections among the young.

According to Dr Paul Van Look, Director of Reproductive Health and Research at WHO, “Sexual behaviours and norms vary enormously around the world and unfortunately many people, including politicians and even health professionals, are uncomfortable dealing with such matters. This survey sounds an urgent alarm that if we do not address sexual and reproductive health openly and directly the toll of death and disability will remain with us for many years to come.”

Given the diversity of sexual and reproductive behaviours revealed by the study, the authors call for a mix of prevention strategies and caution against quick fixes and a “one size fits all” approach. They call for greater efforts to tackle the links between sexual and reproductive ill-health and poverty, gender inequalities and negative social attitudes.

The Lancet Series on Sexual and Reproductive Health will be published in the coming weeks. The series will focus on issues such as adopting a public health approach to sexual and reproductive behaviours to reduce death and disability from unsafe sex, the impact of unsafe abortions, and the need to prioritize sexual and reproductive health, family planning and contraception to achieve the Millennium Development Goals.

 HIV Gene Therapy

Researchers at the University of Pennsylvania School of Medicine report the first clinical test of a new gene therapy based on a disabled AIDS virus carrying genetic material that inhibits HIV replication. For the first application of the new vector five subjects with chronic HIV infection who had failed to respond to at least two antiretroviral regimens were given a single infusion of their own immune cells that had been genetically modified for HIV resistance.

The researchers, led by Carl June, MD, and Bruce Levine, PhD, of the Abramson Family Cancer Research Institute and the Department of Pathology and Laboratory Medicine, along with Rob Roy MacGregor, MD, Professor of Medicine, report their findings in the online edition of the Proceedings of the National Academy of Sciences. Viral loads of the patients remained stable or decreased during the study, and one subject showed a sustained decrease in viral load. T-cell counts remained steady or increased in four patients during the nine-month trial. Additionally, in four patients, immune function specific to HIV improved.

Overall, the study results are significant, say the researchers, because it is the first demonstration of safety in humans for a lentiviral vector (of which HIV is an example) for any disease. Additionally, the vector, called VRX496, produced encouraging results in some patients where other treatments have failed.

“The goal of this phase I trial was safety and feasibility and the results established that” says June. “But the results also hint at something much more.”

Each patient received one infusion of his or her own gene-modified T cells. The target dose was 10 billion cells, which is about 2 to 10 percent of the number of T cells in an average person. The T-cell count was unchanged early after the infusions. “We were able to detect the gene-modified cells for months, and in one or two patients, a year or more later,” says Levine. “That’s significant – showing that these cells just don’t die inside the patient. The really interesting part of the study came when we saw a significant decrease in viral load in two patients, and in one patient, a very dramatic decrease.”

But, cautions Levine, “just because this has produced encouraging results in one or two patients doesn’t mean it will work for everyone. We have much more work to do.” In the current study, each patient will be followed for 15 years.

Trojan Horses
“The new vector is a lab-modified HIV that has been disabled to allow it to function as a Trojan horse, carrying a gene that prevents new infectious HIV from being produced,” says Levine. “Essentially, the vector puts a wrench in the HIV replication process.” Instead of chemical- or protein-based HIV replication blockers, this approach is genetic and uses a disabled AIDS virus to carry an anti-HIV genetic payload. The modified AIDS virus is added to immune cells that have been removed from the patients’ blood by apheresis, purified, genetically modified, and expanded by a process June and Levine developed. The modified immune cells are then returned to the patients’ body by simple intravenous infusion.

This approach enables patients’ own T cells, which are targets for HIV, to inhibit HIV replication – via the HIV vector and its anti-viral cargo. The HIV vector delivers an antisense RNA molecule that is the mirror image of an HIV gene called envelope to the T cells. When the modified T cells are given back to the patient, the antisense gene is permanently integrated into the cellular DNA. When the virus starts to replicate inside the host cell, the antisense gene prevents translation of the full-length HIV envelope gene, thereby shutting down HIV replication by preventing it from making essential building blocks for progeny virus. VRX496 was designed and produced by the Gaithersburg, Md. biotech company VIRxSYS Corp.

A New Field
The new vector is based on a lentivirus, a subgroup of the well-known retroviruses. The study and its safety profile to date have now opened up the field of lentiviral vectors, which have potential advantages over other viral vectors currently being studied because they infect T cells better than adenoviruses, a commonly used viral vector. Lentiviruses also infect non-dividing or slowly dividing cells, which improves delivery to cells such as neurons or stem cells, thus enabling the evaluation of gene therapy in an even wider array of diseases than before. Furthermore, lentiviral vectors insert into cellular DNA in such a way that may be safer than other gene therapy vectors. This is because lentiviruses appear to insert differently from other retroviruses that have caused side effects in other trials involving stem-cell therapy. In addition, gene insertion by lentiviral vectors is attractive for potential therapeutics since it enables long-term gene expression, unlike other viral vectors where expression is lost over time.

Penn researchers are now recruiting for a second trial using the VRX496 vector with HIV patients whose virus is well controlled by existing anti-retroviral drugs, a group of patients who are generally healthier and have more treatment options available. This trial will use six infusions rather than one and is designed to evaluate the safety of multiple infusions and to test the effect of infusions on the patients’ ability to control HIV after removal of their anti-retroviral drugs. The hope is that this treatment approach may ultimately allow patients to stay off antiretroviral drugs for an extensive period, which are known to have significant toxicity, especially after long-term use.

The key to combating AIDS in Russia may be to treat HIV-infected drug users. A new model estimating the spread of HIV in Russia suggests that treating injection drug users with antiretroviral medication will slow transmission of the virus among the general population. The study, which will appear in the December issue of the journal AIDS, was led by Douglas Owens, MD, a researcher at the Veterans Affairs Palo Alto Health Care System and professor of medicine at the Stanford University School of Medicine, and Margaret Brandeau, PhD, professor of engineering at Stanford.

Estimates vary, but around 1 million Russians - slightly more than 1 percent of the adult population - are infected with HIV, the virus that causes AIDS. Injection drug users account for three-quarters of all HIV cases in Russia, and the epidemic is spreading rapidly to non-drug users. According to the United Nations, Russia’s HIV infection rate is among the fastest-growing in the world. By 2020, HIV could afflict 14.5 million Russians, according to a study from the Woodrow Wilson Center in Washington, D.C.

Advances in antiretroviral therapies have the potential to stem the spread of the virus in Russia, but in 2005 less than 1 percent of HIV-infected Russians - 5,000 people - received the life-extending drugs.

The situation is worse among drug users. “Almost no injection drug users in Russia are getting antiretroviral drug therapy,” said Owens.

Antiretroviral therapies now combine multiple individual drugs to reduce the amount of virus in a person’s body. The cumulative effect of two or three medicines works better than a single one to keep the virus at bay. Antiretroviral therapies have the added benefit of reducing the chances that an infected person will transmit HIV to others.

To understand how antiretroviral therapy could affect HIV transmission in Russia, Owens and Brandeau, along with doctoral student Elisa Long, created a computer model of the virus’ spread through the adult population in St. Petersburg, Russia. They accounted for infection rates among drug users and non-drug users and the reduced viral transmissibility and increased life expectancy of infected individuals on antiretroviral medication.

The researchers examined the hypothetical impact of treating only non-drug users, treating only addicts, treating both groups or maintaining the status quo. Owens called the approach a “thought experiment,” designed to predict how treating different groups in the population would affect the overall epidemic.

“Exclusively treating non-drug users is not a wise approach. It’s the least efficient and it’s the least effective,” said Long.

According to the model, treating only HIV-infected drug users will prevent more infections among non-drug users than exclusively targeting the non-drug users. Injection drug users are likely to spread HIV through unprotected sex, so reducing their ability to spread the virus can significantly reduce the spread of HIV to the general population.

The researchers also looked at the expense of the various treatment strategies, which had an estimated cost between $9.4 and $11.2 billion over 20 years. Giving medication only to non-drug users was not the most expensive approach, but it prevented the fewest new infections, according to the study. Treating both populations equally provided the most health benefit for the money, said Owens.

One key to implementing treatment programs will be keeping injection drug users on their HIV medications, said Owens. Antiretroviral therapy regimens have become much simpler, often requiring patients to take just one or two pills per day.

“If they can get the treatment and support, intravenous drug users can do well taking their medications,” said Owens.

The study has important implications for Russia’s approach to combating AIDS. Antiretroviral therapy is expanding in Russia, but it remains to be seen whether drug addicts will receive treatment, Owens said. “Our main message is that really to have an impact on the epidemic, you have to treat both the drug users and non-drug users.”