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Title: Human cytomegalovirus transmission in early childhood and impact of maternal HIV in Zambia : a molecular study
Author: Musonda, K. G.
ISNI:       0000 0004 6351 0534
Awarding Body: London School of Hygiene & Tropical Medicine
Current Institution: London School of Hygiene and Tropical Medicine (University of London)
Date of Award: 2017
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Human cytomegalovirus (HCMV) is the leading infectious cause of birth defects and neurodevelopmental delay, with worst outcomes in congenital infection. HCMV exacerbates neurological disease and progression to AIDS in HIV co-infected infants. In Zambia HCMV has adverse effects on growth and development even in maternally HIV-exposed uninfected infants, affecting a third. Transmission to infants can be congenital or postnatal primarily through breast milk, similar to HIV. However, the route affecting infant development is not established, but critical to understand for deployment of appropriate interventions and hospital diagnostics. In this thesis, congenital HCMV infection was investigated in newborns using PCR and nucleotide sequencing of saliva and umbilical cord DNA, and showed 1% prevalence, which was too low to account for the widespread adverse growth effects. Therefore, maternal HCMV secretion via breast milk and the effects of maternal HIV were investigated. HCMV viral loads were measured by qPCR in 461 breast milk samples from both HIV-infected and uninfected mothers at postpartum day 3 and weeks 2, 4, 9, 12, and 16. Results showed higher HCMV viral loads and longer secretion in HIV-positive compared to negative mothers, peaking at week 4 (p=.026) and remaining elevated at week 16 (p < .001). HCMV strains were investigated using the hypervariable glycoprotein gO, with all eight genotypes detected, but no relationship to viral load. Next, Illumina NGS was used to further analyse strains and mixed infections in order to assess the burden of infection. A script was developed to identify linked gO and gN 'Molecular tags' via analyses of FASTQ reads. In 21 samples, mixed infections were identified, showing 1-7 genotypes and a dominant genotype constituting 45-100%. ZMB240, a full-length HCMV genome - the first reference strain from a healthy donor representing a transmission population, and also first from Africa - was derived directly from breast milk DNA and found similar to elsewhere, including the reference Merlin. Overall, the thesis provided evidence that breast milk is the principal route for early HCMV infection in breastfed Zambian infants, and that maternal HIV increases HCMV load, burden of infection, and duration of secretion in breast milk, thereby escalating and prolonging risk of early infant HCMV infection.
Supervisor: Gompels, U. Sponsor: Commonwealth Scholarship ; HHV-6 Foundation
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral