Infant Peri-Exposure Prophylaxis to Prevent HIV-1 Transmission by Breastfeeding: Mechanisms & Safety

Background Besides optimal efficacy, Prevention of mother-to-child transmission of HIV(PMTCT) strategies must have a very good safety profile (1). Indeed, very large quantities of children will be exposed to these strategies, and the vast majority of them will not eventually be infected. Because in utero HIV exposure followed by one year of antiretroviral treatment (i.e at the time of infant embryogenesis and maturation) may have long-term consequences, such as hampering child development, an evaluation of safety beyond the end of prophylaxis is necessary to get a comprehensive knowledge of the true benefits/risks balance of PMTCT strategies.

A recent review of the state of the art identified several knowledge gaps in the current understanding of Mother To Child Transmission (2). The role of HIV breast milk cell reservoirs in the HIV transmission through breastfeeding is still unclear. The effect of immune factors present in breast milk of HIV infected mothers on HIV population dynamics is also unknown as well as the permeability of infant's gut mucosa and the mechanisms involved on HIV transmission.

The ANRS 12174 randomized controlled trial (ClinicalTrials.gov Identifier: NCT00640263) evaluated 3TC and LPV/r as infant Prep drugs for 50 weeks in HIV uninfected babies at day 7, with monthly follow-up. In addition, breast milk samples were collected four times during follow-up with infant plasma and cell pellets collected at weeks 6, 22 and 38, and infants Dried Blood Spots (DBS) every 3 months. The final results showed that both 3TC and LPV/r achieved very low rates of transmission with an excellent clinical tolerance and no difference between arms in terms of efficacy or safety. In total, 1103 infants completed the final visit.

This study presents a unique opportunity to i) investigate the mechanisms of HIV-1 post-natal transmission, iii) to assess long-term safety of LPV/r and 3TC and ii) to estimate the final efficacy of infant peri-exposure prophylaxis (PreP), since some children were still exposed at the end of the study.

The study will be conducted at the four ANRS 12174 PROMISE-PEP trial sites, namely East London (South Africa), Ouagadougou (Burkina Faso), Lusaka (Zambia) and Mbale (Uganda).

Clinical and Biological safety component At enrolment, children will be assessed for hospitalisation events since the end of the ANRS 12174 PROMISE-PEP trial, mortality rate, growth, neurodevelopment, mitochondrial and genomic toxicity, and blood biochemical parameters such as full blood count, liver function and the level of adrenal hormones. All biological assays and explorations in this study will be carried out blindly, Mitochondrial DNA depletion study: DBS will be collected from all children at enrolment. Samples will be randomized and only 50 samples from Burkina Faso, Uganda and Zambia will be analysed (N=150) as it give us enough power to detect the statistical inferences within the population.

Genome integrity study:The genome integrity assessment will include 50 children from each of the two PROMISE-PEP arms selected by randomization. (n=100 in total). The Zambian site is the only one with the necessary expertise and laboratory equipment for freezing cells. Therefore, the genome integrity study will only be conducted at this site. As a source of adherent cells, plucked hairs will be collected and frozen in 10% dimethylsulfoxide (DMSO) solution.

Children will be assessed through a battery of tests; the Kaufman Assessment Battery for Children - Second edition (KABC-II), the Movement Assessment Battery for Children - Second Edition (M-ABC2), the Test of Variables of Attention (TOVA)-visual, the Strengths and Difficulties Questionnaire (SDQ25) designed to evaluate the main neuropsychological domains considered to be affected in HIV pediatric disease. Children will be evaluated when they are over 5 years of age.

The 'mechanisms' component includes biological assays to be conducted on breast milk samples previously collected from HIV infected, transmitting or not transmitting mothers enrolled at ANRS 12174 PROMISE-PEP trial. Two studies will be conducted.

• The first study will investigate the specific microRNAs found in exosomes present in breast milk that are linked to regulation immune pathways. We propose to investigate the different miRNA profile in human breast milk in correlation to HIV status and HIV transmission. We also hypothesize that the involved pathways on may be linked with the local mucosal immunity of the mother breast but also with the gut mucosal immunity of the recipient child.
• The second study will focus on the effect of breast milk effect on the cytokine profile of infant's intestinal cells. We aim to determine 1/ the enterocyte cytokine profile exposed to breast milk compounds; 2/ the influence of milk on the transcytosis of T-lymphocytes, both HIV-infected and HIV negative.