Monkeys develop AIDS twice as fast if `binge drinking`

Heavy drinking can accelerate time to AIDS among rhesus macaques infected with simian immunodeficiency virus (SIV), researchers from Louisiana State University report in the October edition of Alcoholism: Clinical & Experimental Research. The monkeys were exposed to alcohol for four days a week at levels designed to simulate `binge` drinking, and compared with a control group.

Heavy consumption of alcohol can impair immunity, leading to infections like pneumonia. Alcohol abuse is also more common among individuals already infected with human immunodeficiency virus (HIV) than among the population as a whole. New research findings show that chronic binge drinking can accelerate the progression of end-stage simian immunodeficiency virus (SIV) among rhesus macaques, likely mimicking what happens to humans infected with HIV.

"Previous research has found that HIV-infected people are more likely to consume alcohol than the general population," said Gregory J. Bagby, Professor of Physiology and Medicine at Louisiana State University Health Sciences Center and corresponding author for the study. "One very recent study conducted in Miami, for example, found that more than 60% of its HIV-infected participants reported heavy alcohol use."

Professor Bagby said that the protracted nature of HIV disease, along with the complex behaviours of HIV-positive patients, makes the study of alcohol consumption or abuse on HIV-disease progression extremely difficult.

"While alcohol abuse is known to impair immune defenses," he said, "resulting in a higher incidence and severity of infections - especially pneumonia - the adverse consequences of heavy alcohol consumption on the HIV-infected patient as it relates to disease progression are poorly understood. The few studies that exist have failed to find an association between alcohol use and HIV disease progression. For this reason, we adopted the rhesus macaque SIV model of HIV disease in order to more effectively isolate the effect of alcohol consumption on infectivity, pathogenesis and progression."

Previous macaque studies have shown higher viral load and greater CD4 cell loss immediately after exposure to SHIV in monkeys persistently exposed to alcohol when compared to animals that received no alcohol, but this difference had disappeared by week 24 and the study did not look at clinical disease progression over the long-term (Kumar 2005).

"The key issue with alcohol consumption and HIV/AIDS is when to start individuals on life-saving antiretrovirals versus the need to avoid their toxic effects that damage the liver and gut along with the alcohol," added Kendall Bryant, Coordinator of HIV/AIDS Research at the National Institute on Alcohol Abuse and Alcoholism. "This 'set point,' which is unobserved, is not characterised by traditional measures of disease status. Professor Bagby's research suggests that the speed of progression of AIDS - at least for alcohol users - is in part set by past and current drinking very early on in the disease. This tells us that we need to get HIV+ alcohol users into treatment much earlier in order to reduce their alcohol use."

For twelve weeks, study authors administered alcohol to 16 male rhesus macaques for five hours on four consecutive days per week via an indwelling intragastric catheter in order to attain a blood alcohol concentration of 0.23 to 0.28 percent. This would be considered the human equivalent of "chronic binge drinking." (defined in the United States as five alcoholic drinks within the space of two hours. In the United Kingdom binge drinking is defined as eight units of alcohol (two thirds of a bottle of wine or four pints of beer) consumed in one 24-hour period).

Control rhesus macaques (n=16 males) were given a sucrose solution under the same conditions. After three months, eight alcohol-treated and eight sucrose-treated macaques were inoculated with SIV_DeltaB670 and followed to end-stage disease. Eight alcohol-treated and eight sucrose-treated macaques were not infected with SIV.

"There are two key findings," said Prof. Bagby. "First, chronic binge alcohol consumption accelerated time to AIDS of rhesus macaques infected with SIV, a virus that mimics what happens to humans infected with HIV. The average time to end-stage disease was decreased from 900 days in control animals to 374 days in the alcohol-treated rhesus monkeys. Second, animals receiving alcohol had higher viral loads in the blood in the early months after being infected with the virus. This higher viral load is associated with more rapid disease progression in both SIV-infected rhesus macaques and HIV-infected humans. Because SIV infection in rhesus macaques is so similar to what happens in HIV-infected humans, we can expect that alcohol would have similar consequences in humans."

Both differences were statistically significant (p

"If these findings are confirmed in HIV-positive individuals, the prevention implications are that both past and current alcohol use impacts disease progression and that many additional years of life will be lost if one continues to drink while infected," said Kendall Bryant.

Professor Bagby noted that although his study implicates alcohol abuse as a cofactor in accelerating SIV disease progression and, by extrapolation, HIV disease - the exact mechanisms by which this occurs remain unclear.

"Each episode of alcohol intoxication can suppress multiple elements of immune function in humans," he said. "This suppression can be largely responsible for the increased incidence of infections such as pneumonia. However, chronic alcohol consumption can also stimulate the immune system, leading to diseases like hepatitis. In this case, perhaps both effects of alcohol are involved: immunosuppression could increase the incidence of opportunistic infections, and immune stimulation could activate cells infected with the virus, causing more cells to become infected."

Notwithstanding what mechanisms may be involved, both Prof. Bagby and Bryant said that HIV-positive individuals must realise that heavy alcohol consumption can accelerate disease progression to AIDS and death.

"We also need to prioritise questions and realise that the HIV epidemic is still with us and that it is growing in many countries with few health resources," said Bryant. "Alcohol use is an important modifiable factor in the AIDS epidemic. It should not be overlooked or underfunded."