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Human immunodeficiency virus-1 (HIV-1) infection of CD8+ lymphocytes has been described in several in vitro culture systems, but whether CD8+ cells are a target and also serve as a reservoir for infection in vivo as yet is unknown. We addressed this issue in patients with acquired immunodeficiency syndrome (AIDS)-related lower respiratory tract chronic inflammation, which is characterized by a massive influx of CD8+ HIV-1-specific cytotoxic T lymphocytes (CTL). Proviral load in lung T lymphocytes and their subpopulations was evaluated by using the DNA-polymerase chain reaction (PCR) technique on cells retrieved by bronchoalveolar lavage. To avoid the possibility that the presence of HIV-1 DNA could be caused by contaminating CD4+ cells, serial dilutions of highly purified CD8+ cells were also analyzed by PCR. Our findings showed that lung CD8+ cells harbor and express HIV-1. To explore the possible mechanisms leading to pulmonary CD8+ lymphocyte infection, we evaluated CD4 gene expression on highly purified CD8+ cells by means of reverse transcriptase PCR. Despite the lack of membrane CD4 reactivity, we could show that CD8+ cells may express CD4 RNA. Coinfection of lung CD8+ cells harboring proviral HIV-1 sequences by viral agents capable of inducing CD4 expression (ie, HHV-6) was not detected. Our data indicate that not only CD4+ T lymphocytes and macrophages, but also CD8+ cells, may represent a target and/or a reservoir for HIV-1 in vivo, and suggest that lung CD8+ lymphocytes could derive from precursors equipped with enough CD4 molecules to become HIV-1 permissive. Aside from the cell-to-cell contact between activated HIV-1 specific CTL and relevant targets, the infection of precursors could represent an additional mechanism accounting for the infection of pulmonary CD8+ cells and their functional impairment.

Human immunodeficiency virus‐1 (HIV‐1) primary isolates differ in replicative capacity on peripheral blood mononuclear cells, tropism for primary monocyte‐derived macrophages (MDM) and T‐cell lines and syncytium‐inducing (SI) capability on MT‐2 cells in vitro. To assess the role of viral phenotype in mother‐to‐child HIV‐1 transmission and the progression of vertically acquired HIV‐1 infection, we studied 57 HIV‐1‐infected women at the time of delivery and 24 HIV‐1‐infected infants. Eight mothers transmitted the infection to their children. Primary isolates, obtained from 7 and 33 transmitting and non‐transmitting mothers, respectively, differed in replicative capacity and SI activity, and no significant differences between the two groups were found regarding these viral properties. However, all primary isolates from transmitting mothers, but about half of those from non‐transmitting mothers, were able to infect and replicate in MDM, regardless of their replicative capacity and/or SI activity; moreover, the monocyto‐macrophage tropism of the maternal isolate correlated with an increased risk of transmission. Viral isolates from HIV‐1‐infected children were typed before 2 months of age; all but four showed a tropism for MDM, further supporting the notion that monocyto‐macrophage tropic variants are selectively transmitted from mother to child and/or selectively replicated upon transmission. Clinical follow‐up disclosed that 7/11 infants with a rapid/high replicating virus but none of the 17 with a slow replicating virus developed severe symptoms of disease and/or severe immunodepression by 1 year of age. By means of competitive RNA‐polymerase chain reaction (PCR), a relationship was found between viral phenotype and dynamics of HIV‐1 replication early in life in children who experienced different patterns of disease progression.

The third variable region (V3) of the envelope protein of human immunodeficiency virus type 1 (HIV-1) contains group- and type-specific epitopes for neutralizing antibodies and contains determinants involved in viral tropism and syncytium-inducing (SI) activity. We studied the in vivo relationship between V3 sequences and viral phenotypes in 24 perinatally HIV-1-infected children. To avoid in vitro selection of intrapatient minor variants, genetic studies were performed directly on uncultured peripheral blood mononuclear cells (PBMC), and the tropisms of HIV-1 isolates were evaluated by culturing patients' PBMC directly with monocyte-derived macrophages, lymphocytes, and MT-2 cells. According to their phenotypes, we could define five types of primary isolates: (i) non-syncytium-inducing (NSI) macrophagetropic, (ii) NSI macrophage-lymphotropic, (iii) NSI lymphotropic, (iv) SI lympho-T-cell line-tropic, and (v) SI pleiotropic. The SI viral phenotype was correlated with a more advanced status of disease. Genetic analysis of intrapatient molecular variants revealed that no relationship between the degree of intrapatient V3 variability and the pattern of viral tropism existed; moreover, within a single patient, the values for V3 variability between CD4+ lymphocytes and CD14+ monocytes were similar, thus suggesting that in vivo variability of the monocytotropic variants is more extensive than previously appreciated. A comparison between the intrapatient major variants and the phenotype of primary isolates disclosed that a negatively charged amino acid at residue site 25 was associated with an NSI macrophage- and macrophage-lymphotropic viral phenotype. Finally, by comparing the V3 sequences derived from our study population with those of several prototypes, we observed that the majority of isolates circulating in Italy are related to the North American subtype B macrophagetropic isolates.