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A study of HIV infection among Texas inmates has identified one patient who was infected while in prison and then within one year of infection had acquired nine HIV drug mutations although he had never received antiretroviral treatment. "So this is the first report of transmission of highly resistant virus during primary infection in prisons," says William A. O’Brien, MD, professor of medicine, pathology, and microbiology and immunology at the University of Texas Medical Branch and Division of Infectious Diseases in Galveston.
O’Brien accessed plasma samples from inmates in 1998, looking at resistance patterns among HIV-infected prisoners who had viral loads of 5,000 copies or more. "Our center takes care of patients in the Department of Justice as well as in the university setting, so I analyzed about 700 samples, about half in prison and half in the university, to make a comparison of the two different populations," O’Brien says.
He found that people who have more than 5,000 viral copies showed a lot of resistance in both patient populations. The resistance mutation that emerged most significantly was the one associated with the use of the antiretroviral drug 3TC.
The chief difference between the two populations was that there was significantly more mutation associated with 3TC among the prison population, with resistance approaching 80%, vs. 50% among the university health center patients. "There are a number of explanations, and one of the best is that because it’s such a well-tolerated and easy-to-take drug, people in prison can continue to get this drug even after they fail their regimen that contains this drug," O’Brien says. "So this is a value of resistance testing."
If prison physicians used resistance testing among patients who were failing their therapy, they would have known that this mutation was present and could have avoided the drugs that were associated with the mutation, he adds.
While conducting the research, O’Brien came across one patient who had high-risk sexual behaviors for HIV infection and had several negative HIV tests while incarcerated. Then, in early 1997, the man had his first positive antibody test. He was not placed on antiretroviral therapy. Eleven months later, the man’s blood tests showed that he had nine HIV mutations associated with drug resistance. These same mutations were found again a little more than a year later, although he had never received antiretroviral drugs.
"What makes this case even more interesting is that there are a number of reports that show that resistant virus can be transmitted with HIV infection, and there have been reports of multidrug-resistant virus," O’Brien says. "But the resistance mutations usually fade away over time if patients are not treated, because the virus without mutations may be able to grow a little better."
That’s why it was so unusual to find an untreated patient with nine drug-resistant mutations existing a year or more after they were transmitted, O’Brien says. "So this suggests that resistant virus can be transmitted to people who are already infected," O’Brien says. "I’ve been cautioning patients for 15 years that even if they already have HIV, it’s theoretically possible they could get a virus that’s worse than the one they already have."
The study also suggests that clinicians should consider obtaining a resistance test of HIV patients before beginning therapy when those patients have high-risk behaviors that would make it likely they’ve been exposed to drug-resistant virus, O’Brien says.
Drug-resistant virus may be more common in some prison settings because inmates may be unwilling to subject themselves to the hassle of following a strict medication regimen. Those who start therapy may be inconsistent in taking medications, and others may decline to take drugs altogether because they don’t want to be identified as an inmate who has HIV, O’Brien says. "If a young man goes to the prison’s pill window two or three times a day, everyday, then he’s identified as having HIV infection," he says.
O’Brien’s continuing research will focus on providing routine resistance testing and following patients’ drug regimens to see whether resistance testing is providing a benefit in their therapy. "We will look at which drugs are selected and what their viral load response is," O’Brien says. "Interpretation will be made by doctors at our center and made through direct observation of prison patients when they come to our center."