Brief Antenatal HIV Treatment Tied to Emergence of Viral Drug Resistance

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By Will Boggs, MD

Antiretroviral resistance can emerge during the temporary treatment of HIV-positive women to prevent vertical transmission of HIV during pregnancy, according to a report in the January 3rd issue of AIDS.

"The use of three antiretroviral therapy drugs with evidence of viral control does not guarantee that resistance will not develop," Dr. Fiona E. Lyons told Reuters Health.

The impact of the current strategy of treating HIV-positive pregnant women temporarily to prevent vertical transmission of the virus on the emergence of antiretroviral resistance -- and subsequent response to antiretroviral therapy -- has not been investigated, Dr. Lyons from St. James's Hospital, Dublin, Ireland and colleagues explain.

The group studied 50 HIV-positive women who initiated antiretroviral therapy during pregnancy. The median time on antiretroviral therapy was 70 days, the report indicates, and there was substantial viral load reduction, to less than 1000 copies/mL in 97% of evaluated women.

Genotypic resistance testing was performed a median 42 days after cessation of therapy. Five of 39 postpartum sequences showed seven primary mutations in the reverse transcriptase segment, the researchers note. All five women with mutations were on nevirapine-containing regimens and had not been on antiretroviral therapy before their pregnancy.

Similarly, the findings indicate, 6 of 35 protease sequences demonstrated resistance mutations, and all women with such mutations were protease inhibitor-naive.

CD4 cell count, pretreatment viral load, duration of antiretroviral therapy, pre-delivery viral load, and time from treatment cessation to genotypic resistance testing did not differ between women with viral mutations and those with no mutations, the investigators report.

"This work was part of an ongoing cohort study of all antiretroviral therapy used in pregnancy in Ireland," Dr. Lyons explained. She noted that the study was limited by the absence of pretreatment genotyping, to check for existing resistance mutations. Even though this was unlikely in this cohort, she added, resistance testing should be undertaken ideally at the commencement of therapy, as well as when therapy ceases.

02/14/05

AIDS 2005;19:63-67.