Viral and Host Factors Associated with HIV-1 Vertical Transmission and Pathogenesis

Abstract

The majority of neonates and infants acquire HIV-1 infection through vertical transmission. In addition these HIV-1 infected infants have a higher viral load and progress to AIDS faster than adults, often times more rapidly than their own infected mothers. However, the mechanisms of this differential disease progression are not well understood. Several studies have shown, including work from our laboratory, that it is the transmission of the minor genotype with the R5 phenotype that is involved in transmission. We have also shown that a lower viral heterogeneity may influence vertical transmission. Moreover, we have also shown that there is a differential HIV- influenced at the level of HIV-1 gene expression and not at the level of expression of receptors or coreceptors. Moreover, I have characterized the cellular gene expression profile of uninfected and infected cord monocyte-derived macrophages (MDM) as compared with adult MDMs. Evaluation of these cellular factors identified genes that fell into several classes including transcriptional activators/repressors, cytokines, and matrix metalloproteinases, all of which may be able to influence HIV-1 gene expression. To explain this differential HIV-1 gene expression, I have modulated the level of cellular factors (IL6 and STAT3) using short hairpin RNA (shRNA) technology to determine if these cellular factors were playing a role in an increased HIV-1 replication and gene expression. I found that upon downregulation of these factors, there was a decrease in HIV-1 LTR directed gene expression. Taken together, the results from this dissertation provide new insights into elucidating the mechanisms of HIV-1 vertical transmission and HIV-1 gene expression in neonates and infants. This work which has identified several cellular factors may offer new possibilities for the development of therapeutic strategies to treat pediatric AIDS.1 replication and HIV-1 gene expression in neonatal cells as compared to adult cells. The hypothesis of this dissertation is that viral determinants and cellular factors in neonatal and adult mononuclear cells influence HIV-1 replication and HIV-1 gene expression. In this dissertation I have molecularly characterized the HIV-1 long terminal repeat (LTR) from 6 mother-infant HIV-1 infected pairs, and shown that mutations generated during vertical transmission correlate with HIV-1 gene expression. Furthermore, I have also shown that there was a low degree of viral heterogeneity and a high conservation of critical transcription factor binding sites within the LTR. I have also shown that nuclear extracts from neonatal (cord) mononuclear cells bind with higher efficiencies to HIV-1 LTR as compared to nuclear extracts from adult mononuclear cells. In addition, I have also made strides in trying to elucidate the mechanisms of differential HIV-1 replication and gene expression. I have shown that there is a differential HIV-1 replication in naïve and memory T-lymphocytes from cord vs. adults and this increased HIV-1 replication was