Identification of Nevirapine-Resistant HIV-1 in the Latent Reservoir after Single-Dose Nevirapine to Prevent Mother-to-Child Transmission of HIV-1

The most widely used intervention to prevent mother-to-child transmission of HIV-1 in resource-limited settings is a single dose of the nonnucleoside reverse-transcriptase inhibitor (NNRTI) nevirapine, administered to pregnant women at the onset of labor, followed by a dose of nevirapine administered to the infant ≤72 h after birth [1, 2]. Single-dose nevirapine decreases transmission by 41%−47% [1, 2]. However, the most sensitive assays available detected nevirapine-resistant virus in the plasma of up to 87% of mothers 6 − 8 weeks after treatment [3–6]. Although resistant virus typically fades to undetectable levels in the plasma within several months [5–7], the persistence of resistant virus in the plasma for up to 5 years has been reported [8]. The most common mutations selected by single-dose nevirapine include K103N, Y181C, and G190A [7]. These mutations also confer resistance to other NNRTIs. A major concern regarding single-dose nevirapine is that the first-line antiretroviral regimens in developing countries rely on an NNRTI along with 2 nucleoside reverse-transcriptase inhibitors. The presence of virus resistant to a key component of these regimens could lead to treatment failure. Although the development and persistence of nevirapine-resistant virus in the plasma has been well studied [3–14], evidence of archived resistance in the latent reservoir for HIV-1 in resting CD4+ T cells is lacking. The latent reservoir is established after infection of activated CD4+ T cells and integration of proviral HIV-1 DNA into the host genome. A small fraction of HIV-1–infected, activated CD4+ T cells return to a resting state as memory cells. In these cells, HIV-1 enters a state of latency in which it is protected from cellular immunity and antiretroviral drugs [15, 16]. In these inherently long-lived resting memory CD4+ T cells, the integrated HIV-1 genome is preserved for the life of the cell. Activation of a latently infected memory cell can trigger the release of archived virus [17]. Among patients receiving highly active antiretroviral therapy (HAART) for whom HIV-1 viremia was suppressed to undetectable levels, the frequency of latently infected cells is stable [18]. Thus, the latent reservoir is a major barrier to curing HIV-1 infection. It is unclear whether nevirapine-resistant virus can be permanently archived in the latent reservoir after a single dose. Analysis of this issue is complicated by the ongoing viral replication that continues in mothers after nevirapine has been cleared. In viremic patients, most of the HIV-1 DNA in resting CD4+ T cells is a labile, unintegrated form representing recent infection [19, 20], and standard methods thus cannot provide an accurate reflection of the stable latent reservoir in resting CD4+ T cells. To evaluate the presence of nevirapine-resistant virus in the latent reservoir of women who had received a single dose of this drug, we used a novel method to detect stably integrated HIV-1 in highly purified resting CD4+ T cells.