Inflammatory markers in breast milk of HIV-infected and uninfected women in sub-Saharan African women
At least 20% of women of reproductive age in parts of sub Saharan Africa are HIV-infected and transmission of HIV from mother-to-child through breastfeeding up to 2 years postpartum may account for half of the vertical transmission observed. However, little is known about factors within the breast that may influence milk viral load and/or transmission of HIV to the infant. The aim of this study was to explore the inflammatory processes that may affect the risk of mother-to-child transmission. This thesis was based on work from 4 different field studies: Rural Tanzania (n=85), urban South Africa (n=144), an urban hospital in Zambia (n=22) and an urban community in Zambia (n=112). Two of these studies were fully undertaken by the author (Zambian community and Zambian hospital studies) and two of the studies involved retrospective laboratory and statistical analysis by the author (Tanzanian study and South Africa study). The studies were designed to investigate the influence of social, biological and breastfeeding indicators on HIV status and severity of HIV infection in breastfeeding women. In addition, to determine if breast milk C-reactive protein (CRP) was a suitable surrogate measure for systemic inflammation and risk of mother-to-child transmission measured by non-invasive breast milk sampling. HIV infection in breastfeeding Zambian women was independently associated with raised breast milk CRP with an odds ratio (OR) of 3.91 (95% CI: 1.50, 10.17, p=0.005), giving birth to a male infant (OR=2.53; 95% CI: 1.38, 4.64; p 0.01) and greater maternal wealth (OR=1.12; 95% CI: 1.05, 1.22; p=0.001). Severity of HIV infection (women with a CD4 count at delivery of 500 cells/mm3 ) was independently associated with raised breast milk CRP (OR=2.49; 95% CI: 1.61, 3.87; p 0.001) and breast milk RNA (OR=1.28; 95% CI: 1.00, 1.63; p=0.05). Breast milk CRP was found to correlate with plasma CRP (rs > 0.60; p 0.05) and breast milk IL-8 (rs 0.42; p 0.05); to be associated with poor infant feeding technique, poor feeding practice, maternal breast inflammation and reduced infant weight gain (p 0.05). Breast milk CRP was shown to positively correlate with breast milk RNA and inversely correlate with maternal CD4 count in South African women (p 0.05). Breast milk CRP has been shown to be associated with maternal HIV status and increased HIV severity in breastfeeding sub Saharan African women. Further work is needed to assess if CRP could be used as a surrogate risk factor for mother to child transmission of HIV.