Recently infected women at the time of delivery have a higher rate of in-utero transmission in PEPI-Malawi
Polly Clayden, HIV i-Base
HIV incidence infection in pregnancy is common in women in sub-Saharan Africa.
Investigators from the PEPI-Malawi trial recently developed a multi-assay algorithm (MAA) to determine incidence. They used the assay to identify women in the trial who were likely to have been recently infected with HIV at the time of delivery. They then evaluated whether those women were at increased risk of in utero mother-to-child transmission of HIV (MTCT).
Susan Eshleman and colleagues showed findings from this evaluation as a poster at CROI 2011.
PEPI-Malawi compared three infant regimens for prevention of post-natal MTCT.
The investigators obtained plasma samples from 2561 women at time of delivery. The samples were tested using the BED-Capture EIA (BED) and an avidity assay (a modified version of the BioRad HIV-1/HIV-2+0 ELISA).
For their MAA they used the following criteria to identify recently infected women:
BED<1.0 OD-n + avidity < 80% + CD4 cell count >200 cells/mm3 + HIV viral load >400 copies/mL
They indentified 73 (2.9%) women as recently infected using the MAA.
All but 9 women with non-recent infection had a BED result >1.0 and/or an avidity result >80%; 4 women with non-recent infection had a CD4 count <200 cells/mm3; and 5 had a viral load <400 copies/mL.
Of 54 women known to have non-recent HIV infection (median time since previous positive HIV test, 4.29 years, range 2.3 to 6.1 years), none were misclassified as recently infected. Nor were 9 women already receiving HAART at the time of delivery.
The recently infected group were younger, had lower parity and higher median CD4 cell count at delivery than the non recent group (all p<0.0001).
The risk of in utero MTCT was significantly higher among women identified as recently infected compared to non-recent< 17.8% vs 6.7%, p= 0.001.
In a multivariate analysis, increased risk of in utero transmission was independently associated with: recent infection AOR 2.49 (95% CI 1.30-4.78), p=0.006; viral load (per log10 increase, AOR 2.01 (95% CI 1.60-2.51), p <0.0001; and age (per 10-year increase, AOR 0.66 (95% CI 0.43-0.93), p=0.02). There was no association with CD4 count, infant gender, early presentation or infant regimen.
The investigators concluded that their results suggest recent maternal HIV acquisition is strongly associated with in utero HIV transmission independent of viral load at delivery.
This is the first randomised trial data to show the association between recent infection and in utero transmission.
Eshleman S et al. Women identified as recently infected at the time of delivery using a multi-assay algorithm for HIV incidence had a higher rate of in utero HIV Transmission: PEPI-Malawi Trial. 18th CROI, Boston. February 2011. Poster abstract 737.