Researchers find that Texas clinic's HIV resistance is stable over time
Researchers find that Texas clinic's HIV resistance is stable over time
Clinic's population shifts to more Hispanics
HIV clinicians and researchers still are learning how HIV evolves through mutations and development of resistance. If patterns of increasing resistance emerge then this has serious implications for HIV treatment and prevention.
One way to find out whether a population's virus is changing or becoming more resistant over time is to compare 2 different timelines in the same area, which is what Texas investigators recently did.
"We had snapshots of what the baseline looked like in our clinic in 1999 and also in 2003-2004, so I evaluated another snapshot of 2004 to 2006 and compared that with the 2 prior time points," says Tanvir K. Bell, MD, an assistant professor of medicine at the University of Texas Medical School in Houston, TX.
"The purpose of the study was to look at the genotypes, the demographics, and the CD4 cell counts," Bell says. "I wrote in my conclusion that as patients access medical care at more advanced medical disease, there are missed opportunities for diagnosis and intervention."
Overall, the resistance patterns have stayed stable over the 3 different time periods, Bell notes.
"In other populations, they've seen more increasing resistance, and people talk about the non-nucleoside reverse transcriptase inhibitor (NNRTI) class developing resistance at an increasing rate," Bell says. "In our study, it went up from 2.5 percent in 1999 to 4.5 percent in 2003-2004, but then it stayed stable at 4.5 percent."
Investigators found that nucleoside reverse transcriptase inhibitor (NRTI) mutations were found in 4.5 percent of patients in 1999, 2.5 percent in the 2003-2004 period, and zero in the 2004-2006 period.1
NRTI resistance might have faded in the more recent time period because these mutations go away quicker than NNRTI or PI resistance, Bell suggests.
"And this population hasn't been on medications because they were either newly infected or had just never been on antiretrovirals," Bell says. "So what we're capturing are people as they get resistant virus from wherever they acquire the HIV virus."
The genotype test was conducted before they started drug therapy, she adds.
"Some mutations don't last long in the body if someone doesn't have the pressure of drugs," Bell notes. "M144V is a common mutation against NRTIs; it's 3TC resistance."
But resistance to the mutation fades when the patient does not take antiretrovirals, she adds.
NNRTI resistance was found in 2.5 percent of patients in 1999, 4.5 percent in 2003-2004, and 4.5 percent in 2004-2006. And protease inhibitor (PI) resistance was found in 2.5 percent of patients in 1999, 4.5 percent in 2003-2004, and 3 percent in 2004-2006.1
"One of the limitations of this study is that the sample sizes are relatively small," Bell says.
There were 44 patients included in the 1999 data, 40 in the 2003-2004 data, and 66 in the 2004-2006 data.1
One of the more interesting trends noted in the study was the change in patient demographics over the 7 year period. In 1999, 69 percent of the patients were African American, and 22 percent were Hispanic. By 2004-2006, the racial composition was 35 percent African American and 53 percent Hispanic.1
"The people captured in the last time frame included more Hispanics at 53 percent," Bell says. "We probably have some Spanish-speaking providers in our clinics, and so now we have more Spanish-speaking clients."
Another trend noted was that HIV patients tended to be sicker in the more recent time period when they first arrived at the clinic.
The mean CD4 cell count in 1999 was 288; it was 274 in 2003-2004, and in 2004-2006, it was 122.1
Median RNA viral loads were higher between 1999 and 2006, with a median of 4.87 log10 in 1999 and 5.32 log10 in 2004-2006.1
"We're seeing a lot of new clients with CD4 cell counts of about 130 when they come into the clinic," Bell says. "We take care of predominantly uninsured or Medicare/Medicaid patients, and so we see a lot of people who don't have access to good medical care because they're uninsured."
Investigators have 2 hypotheses about their findings: "One is that people are coming in later, and we may not catch the resistance," Bell says. "And the other is there's not as much resistance being spread around in certain populations."
The populations where resistance might increase include those in which a large number of people are on antiretroviral therapy and they engage in high-risk behaviors, such as sharing needles, Bell says.
The Houston population includes patients who are infected with a virus that has not yet developed resistance, so the virus is sensitive still to drugs, Bell says.
The clinic does not routinely perform genotyping, although doctors can order the test for patients according to their own discretion, Bell says.
For clinics in other parts of the country, however, Bell says she would recommend that they also develop snapshots of their area's resistance patterns in order to see if resistance rates are high enough to warrant more routine resistance screening.
Reference:
- Bell TK, et al. Changing genotypic resistance patterns and demographics of antiretroviral-naïve HIV patients in Houston: 1999-2006. Presented at the 44th Annual Meeting of IDSA, held Oct. 12-15, 2006, in Toronto, Canada. Poster: 1111.
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