Session 19aOral Abstract Presentations Maternal-Fetal/Pediatrics/Women's Health Session Day and Time: Wednesday 10 am - 12 noon Presentation Time: 10:00 Room: 302-306
96 Breast Milk Shedding of Drug-resistant Subtype C HIV-1 and Among Women Receiving Single-dose Nevirapine E. Lee*1, R. Kantor1, E. Johnston1, P. Mateta2, L. Zijenah2, D. Katzenstein1 1Stanford Univ, Palo Alto, CA and 2Univ of Zimbabwe, Harare
Background: Breastfeeding is a significant risk factor for HIV mother to child transmission (MTCT) with estimated transmission rates at 0.5%-2% per month. Interventions in MTCT include single-dose (SD) maternal nevirapine (NVP) and NVP prophylaxis to breastfeeding infants. Selection and shedding of NVP resistant virus in breast milk (BM) after SD NVP may limit prophylaxis effectiveness.
Methods: In the HPTN 023 study, 33 women from Chitungwiza, Zimbabwe, received SD NVP at the onset of labor. Plasma (P) and BM were collected at 2, 8, 16, and 20 wks postpartum. HIV-1 RNA virus load (VL) from P and BM was quantified by ultra-sensitive Roche 1.5 Amplicor Monitor and converted to log10 copies/ml. HIV-1 RNA was isolated using the Qiagen RNA Kit and sequenced with the Visible Genetics, TruGene Kit. Statistical analysis of P and BM data were conducted on the SAS program.
Results: Plasma RNA was quantified in all women at 8 wks post-NVP ranging from 2.6-5.9 log copies/ml with a median of 4.6 log copies/ml. BM HIV-1 RNA was detectable in 23/33 (70%) women ranging from 0.9-4.3 copies/ml (median 2.5 log copies/ml). There was little correlation (Spearman’s r = 0.29, p = 0.17) between 23 BM and P paired VL measures. HIV RT consensus sequence was obtained from 33 samples of maternal P and 61% (20/33) of the women’s BM. The frequency of mutations in BM associated with NVP resistance 13/20 (65%) was significantly higher than the 24.2% (8/33) (Chi-Square, p < 0.01). Using a paired test comparing the mutations in 20 P and BM samples, there was also a significant increase in the frequency of BM mutation compared to P (McNemar’s test, p = 0.02). K103N (often as a mixture of K103K/N) was the most frequent NVP mutation in BM (12/20) and P (5/33) with additional NVP associated mutations including Y188C, V106A, G190A in BM and Y181C, V106A in P. Only 4/20 pairs of P and BM demonstrated the same mutation(s). Phylogenetic analysis of RT showed all samples were subtype C. The 20 BM and P samples from each woman were more closely related to one another than to sequences from other women.
Conclusions: Cell-free HIV-1 RNA in BM, detectable at low levels in at least 70% of the women, was associated with a high prevalence of NVP-resistance mutations. Significantly higher frequency of resistance mutations in BM compared to P provides evidence for differential selection and expression of NVP resistance in the BM compartment after SD NVP.
