Vertical transmission of HIV infection during the peripartum period or while breastfeeding was associated with maternal HIV drug resistance, viral load, and CD4 counts These findings, from a case-control study, were published in Clinical Infectious Diseases.

Data from the Promoting Maternal and Infant Survival Everywhere (PROMISE) study were used for this analysis. This randomized, open-label strategy trial was conducted at 14 sites in 7 countries between 2011 and 2016. The trial included women with HIV infection who were pregnant and had CD4 counts greater than or equal to 350 /mL were assigned to receive antiretroviral therapy. Risk factors associated with vertical transmission to infants either during peripartum or while breastfeeding were assessed between cohorts of women who transmitted to their infant (n=85) and a matched cohort of non-transmitters (n=255). Vertical transmission was categorized as occurring during the peripartum period if nucleic acids were detected in the infant within 2 weeks following birth, and as occurring while breastfeeding if nucleic acids were detected in the infant between 2 and 104 weeks of age.

The researchers found that there was an increased risk for vertical transmission during the peripartum period (n=48) compared with the breastfeeding period (n=37).


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Of mothers who transmitted HIV, the researchers noted an increased rate of HIV drug resistance at infant diagnosis (14.6% vs 6.7%; P =.0039), increased HIV RNA viral loads at infant diagnosis (median, 4.28 vs 3.86 log10 copies/mL; P <.0001), and decreased CD4 cell counts at enrollment (median, 496 vs 539.5 /mL; P =.028).

The researchers found no association between peripartum transmission and a lack of an antepartum treatment regimen (adjusted odds ratio [aOR], 9.82; 95% CI, 2.07-46.7; P =.004), zidovudine monotherapy (aOR, 4.54; 95% CI, 1.70-12.1; P =.003), and viral load at enrollment (aOR, 3.45; 95% CI, 1.24-9.57; P =.018).

Risk for transmission during breastfeeding was associated with drug resistant genotype scores of10 or greater (aOR, 4.45; 95% CI, 1.34-14.7; P =.015) and HIV RNA viral loads of greater than or equal to 4 log10 cells/mL (aOR, 4.03; 95% CI, 1.43-11.4; P =.008).

Among HIV infected infants, transmission during the peripartum period was associated with a decreased rate of drug resistance compared with transmission while breastfeeding (12.2% vs 52.8%; P <.001); however, with time, resistance increased among all infants to 55.5% and 78.9%, respectively.

This study was limited by its inclusion of only women with asymptomatic HIV infection who had relatively increased CD4 cell counts, and the lack of ability to assess associations between postpartum treatment regimens and maternal drug resistance as most mother-infant pairs were followed observationally while breastfeeding.

These data indicated that vertical HIV transmission to infants either during the peripartum period or while breastfeeding was associated with maternal HIV drug resistance, viral load, and CD4 cell counts; supporting the recommendation to replace treatment with nevirapine prophylaxis alone with treatment regimens that have increased barriers to drug resistance.

Reference

Boyce CL, Sils T, Ko D, et al. Maternal HIV drug resistance is associated with vertical transmission and is prevalent in infected infants. Clin Infect Dis. 2021;ciab744. doi:10.1093/cid/ciab744