Identification of HIV-1 transmission clusters: application in epidemiological studies and forensic cases

Zaković, Suzana

http://hdl.handle.net/10400.26/19076

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Authors

Zaković, Suzana

Advisor(s)

Taveira, Nuno

Abstract(s)

In this study, HIV-1 transmission clusters were analysed, to identify transmission networks in Angola and investigate their viral and host correlates, and to identify relatedness of strains in a potential HIV-1 criminal transmission in Portugal. Two methods of cluster analysis, visual inspection and automatic search of reliable nodes on the phylogenetic trees, were applied on the partial pol gene from 365 HIV-1 infected Angolans. Afterwards, HIV-1 diversity and transmission dynamics were analysed in identified transmission networks. It was found that 44.65% of analyzed individuals were part of the transmission networks. The majority (73%) from 63 identified clusters were pairwise, and the largest clusters (n=3) were comprised of 7 individuals, suggesting that current drivers of local epidemics are large number of small clusters. Besides, slow transmission dynamics was identified (median=27 months), which is, together with prevalence of small clusters, concordant with main mode of HIV transmission in Angola, heterosexual transmission. Extreme diversity of subtypes and gradual changes of subtype distribution were identified. This was observed in increased frequency of subtypes A (19.75%), and recombinant CRF02_AG (11.11%), which could indicate on their preferential transmission, and in frequency of CRF18_cpx and CRF37_cpx, that had established successful transmission in the country in recent years. Moreover, potential criminal HIV-1 transmission, involving a father and a son, was analyzed with phylogenetic analysis. Based on analysis of three HIV-1 gene fragments, this relationship could not be refuted. However, although epidemiological link was confirmed, deliberate transmission could not be proved, nor the presence of the third party could be excluded. Understanding the epidemiology of HIV infection is a prerequisite to address public health issues and implement HIV preventive measurements. This study has showed that transmission clusters identification, is a useful tool to approach these issues through analysis of transmission dynamics, viral phenotypic and genotypic properties, trends of current HIV diversity and HIV forensics.