Central nervous system compartmentalization of HIV, an interesting model of viral evolution: from theory to clinical implications

The human immunodeficiency virus (HIV) infects the entire human body. Genetic diversity within the viral population of an infected individual is considerable and heterogeneous. Viral subpopulations develop during infection, which can lead to independent evolutions according to anatomical compartments - organs, tissues or cells - i.e. the phenomenon of viral compartmentalization. The identification of compartmentalization relies on different tests based on phylogenetic analysis of sequences of viral populations, tree topology and genetic distances. Compartmentalized viral populations are found in the central nervous system in nearly half of HIV-infected individuals. This is particularly the case when severe neurocognitive disorders, including dementia, are present. Different genetic and phenotypic properties are associated with compartmentalized HIV variants of the central nervous system, in particular the enhanced ability to infect macrophages. This is an interesting model for studying viral compartmentalization given the tightness of the blood-brain barrier, the peculiar cellular environment for this virus, and the clinical implications for the pathophysiology of HIV infection.