AIDS Update
UN revises worldwide AIDS figures

UNAIDS and World Health Organisation have lowered their estimates of how many people are living with HIV/AIDS worldwide, Reuters/New York Times reports. According to the report about 33 million people worldwide are living with HIV/AIDS, compared with an estimate of nearly 40 million in 2006.

The UN bodies said that better methods of data collection and increased data availability from countries show that HIV/AIDS is not quite as widespread as previously thought (Reuters/New York Times, 11/20).

The report also found that about 2.5 million people will become newly infected with HIV this year, a 40% decrease from last year's estimate primarily because of methodological changes used to derive these estimates but also to more recent reductions in incidence, the Los Angeles Times reports (Chong/Maugh, Los Angeles Times, 11/20).

New cases peaked in the late 1990s and have been declining since 2001 – when it is estimated that about 2.2 million people in sub- Saharan Africa contracted HIV, compared with an estimated 1.7 million in the region this year – the report says.

In addition, the report found that the number of AIDS-related deaths have declined somewhat since 2005 in part because access to antiretroviral drugs has expanded. The report estimated that about 2.1 million people worldwide will die of AIDS-related causes in 2007 (Donnelly, Boston Globe, 11/20).

Although the number of new cases has decreased, the number of people worldwide living with HIV/AIDS has increased as people are living longer with HIV, new infections are continuing, and there is general population growth, the study says.

The percentage of adults worldwide living with HIV/AIDS has remained constant at about 0.8%, according to the study (McNeil, New York Times, 11/20). According to the Los Angeles Times, although the number of new cases has declined in some countries in Eastern and Western Africa because of widespread changes in sexual behaviour, the “bulk of the apparent decrease” is because of improved sampling methods.

Earlier estimates often were taken from pregnant women at prenatal clinics who were more likely to live in urban areas and be sexually active than women in the general population (Los Angeles Times, 11/20).

The new data were taken from national population estimates in 30 countries with high HIV prevalence that involved family interviews and blood tests, the Wall Street Journal reports (Chase, Wall Street Journal, 11/20). The report also says that revised estimates for India, released earlier this year, accounted for a significant part of the decrease in global numbers.

“The single biggest reason for this reduction was the intensive exercise to access India's HIV epidemic, which resulted in major revision of that country's estimates,” the report says. India's revisions, as well as those in five other countries, together accounted for 70% of downward change in the prevalence estimate between last year's published figure and this year's (Reuters/New York Times, 11/20).

According to Paul DeLay – director of evidence, monitoring and policy for UNAIDS – another significant reason for the decrease in new cases is a decrease in the number of sex partners in high-prevalence areas in Southern Africa. DeLay added that consistent condom use among highrisk groups, including commercial sex workers; treatment of sexually transmitted infections; and male circumcision also contributed to the decline.

Reaction

DeLay said that experts are “seeing” the “effect” of program interventions designed to fight the spread of HIV. “In some parts of sub-Saharan Africa, the evidence is pretty convincing that the epidemic has turned,” DeLay said, adding, “We have up to five years of data.

In other areas, we are just starting to see a change with the numbers coming down” (Boston Globe, 11/20). Despite the decrease in figures, the report still shows that the HIV/AIDS pandemic is widespread and that efforts to fight the disease should be increased, UNAIDS officials said.

“These improved data present us with a clearer picture of the AIDS epidemic, one that reveals both challenges and opportunities,” UNAIDS executive director Peter Piot said in a statement.

He added: “Unquestionably, we are beginning to see a return on investment – new HIV infections and mortality are declining and the prevalence of HIV leveling. But with more than 6,800 new infections and over 5,700 deaths each day due to AIDS, we must expand our efforts in order to significantly reduce the impact of AIDS worldwide” (Reuters/New York Times, 11/20).

James Chin of the University of California- Berkeley said UNAIDS and WHO have “been overemphasising and exaggerating” the impact of the virus “in an effort” to increase global funding to fight the disease.

“It's getting closer to what it ought to be, but it's still high,” Chin said. DeLay said it was “absurd” to think the data had been exaggerated, adding that it would “technically impossible to somehow rig the numbers” (Los Angeles Times, 11/20). U.N. officials said the revised data stem from better measurements rather than from shifts in the epidemic, adding that they continually seek to improve monitoring of the pandemic (Timberg, Washington Post, 11/20).

New way to fight HIV identified

Researchers at University of California San Francisco (UCSF), United States and the University of Toronto, Canada, have identified a potential new way of fighting against HIV infection that relies on the remnants of ancient viruses, human endogenous retroviruses (HERV), which have become part of the genome of every human cell.

Researchers believe that their findings, published 9 November 2007 in the journal PLoS Pathogens, could lead to a vaccine targeting HERV that kills HIV infected cells.

Mounting evidence suggests that HIV infection could enable HERV expression by disrupting the normal controls that keep HERV in check. In some HIVinfected individuals, infection fighting T cells are able to target HERV expressing cells.

“One important limitation to a T-cell vaccine targeting HIV itself is that HIV exists in so many variations and is constantly mutating. If we can find other ways for the immune system to target HIVinfected cells, we can overcome this problem in making an HIV vaccine.

HERV may provide us with a good target to test,” said study co-author, Dr Keith E. Garrison.

HERV, human endogenous retroviruses, are the genomic fossils left behind from ancient viral infections that exist largely dormant within every cell. While HERV are present in every cell, HIV may disrupt the normal constraints on HERV activity as it alters the cell to produce more HIV.

This led the authors of the study to look for T cell responses to HERV in HIV-positive people. They found T cell responses to HERV in HIV-positive people that were not present in HIVnegative people. The researchers also compared the T cells that recognise HERV to other types of T cells, including those that recognise HIV.

They found that T cells recognising HERV were different from T cells that recognise HIV. “HIV is poorly contained by the immune system, resulting in disease progression in most people. In contrast, infection with cytomegalovirus (CMV) is generally controlled for life.

HERV specific T cells have more features in common with T cells that kill CMV, than with T cells that kill HIV. This is an encouraging finding which suggests that HERV specific T cells may be more effective than HIV specific T cells in controlling virus,” said study co-author, Brad Jones.

The researchers looked at 29 individuals recently infected with HIV from the UCSF OPTIONS Project, 13 HIV-negative individuals and 3 hepatitis-C-infected, HIV-negative individuals.

In the group recently infected with HIV, researchers found a relationship between the degrees of T-cell response to HERV and the levels of HIV virus present in their blood. “Although these results are preliminary, they encourage new ways to make the immune system potentially target HIV infected cells,” said study co-author Prof. Mario A.

Ostrowski from the University of Toronto. Researchers believe that a vaccine could be created containing HERV antigens that would stimulate T-cells targeting cells expressing HERV.

Although the vaccine would not produce T cells capable of recognising HIV itself, it would evoke a cellular immune response that could still protect people from becoming infected or limit the extent of damage caused by HIV.

“These findings may lead to new lines of attack against HIV, and the clue came from the study of the viruses within us,” said study coauthor, Prof Douglas F. Nixon from UCSF.

 Date of upload: 22nd Jan 2008

                                  
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