Compartmentalization of human immunodeficiency virus type 1 between blood monocytes and CD4+ T cells during infection

Abstract

Distinct sequences of human immunodeficiency virus type 1 (HIV-1) have been found between different tissue compartments or subcompartments within a given tissue. Whether such compartmentalization of HIV-1 occurs between different cell populations is still unknown. Here we address this issue by comparing HIV-1 sequences in the second constant region through the fifth hypervariable region (C2 to V5) of the surface envelope glycoprotein (Env) between viruses in purified blood CD14(+) monocytes and CD4(+) T cells obtained longitudinally from five infected patients over a time period ranging from 117 to 3,409 days postseroconversion. Viral populations in both cell types at early infection time points appeared relatively homogeneous. However, later in infections, all five patients showed heterogeneous populations in both CD14(+) monocytes and CD4(+) T cells. Three of the five patients had CD14(+) monocyte populations with significantly more genetic diversity than the CD4(+) T-cell population, while the other two patients had more genetic diversity in CD4(+) T cells. The cellular compartmentalization of HIV-1 between CD14(+) monocytes and CD4(+) T cells was not seen early during infections but was evident at the later time points for all five patients, indicating an association of viral compartmentalization with the time course of HIV-1 infection. The majority of HIV-1 V3 sequences indicated a macrophage-tropic phenotype, while a V3 sequence-predicted T-cell tropic virus was found in the CD4(+) T cells and CD14(+) monocytes of two patients. These findings suggest that HIV-1 in CD14(+) monocytes could disseminate and evolve independently from that in CD4(+) T cells over the course of HIV-1 infection, which may have implications on the development of new therapeutic strategies.

FIG. 1.

Two-color fluorescence analysis of isolated CD14⁺ monocytes (A) and CD4⁺ T cells (B) from sample II from patient 2. Purified cells were stained with a fluorescein isothiocyanate-conjugated anti-CD14 or phycoerythrin-conjugated anti-CD3 monoclonal antibody. The cells were also stained with fluorescein isothiocyanate- or phycoerythrin-conjugated isotype IgG2a to control for nonspecific binding. The purity of CD14⁺ monocytes was 98.2% ± 0.94% and the purity of CD4⁺ T cells was 98.87% ± 0.36%. The purified cells were also shown to be free from CD8⁺ T cells and B cells (data not shown).

FIG. 2.

Phylogenetic trees based on the maximum-likelihood method showing the evolutionary relationship between HIV-1 C2-to-V5 sequences from blood monocytes (M) and CD4⁺ T cells (T) from each of the five study patients. Panels A to E are for patients 1 to 5, respectively. I to IV, sampling time points shown in Table 1. The scale bar for each tree indicates the percent genetic distance. The numbers in parentheses represent the number of clones with identical sequences.

FIG. 3.

Deduced amino acid sequences of HIV-1 V3 loops from patients 1 to 5. The amino acid sequences have been aligned with the consensus sequences of both monocytes and CD4⁺ T cells from sample I from each patient. Dots indicate identity with the consensus sequences and dashes indicate deletions. Amino acids at positions 11 and 25 of the V3 loop are shaded; positively charged amino acids (R or K) at these two positions are shown in bold.

FIG. 3.

Deduced amino acid sequences of HIV-1 V3 loops from patients 1 to 5. The amino acid sequences have been aligned with the consensus sequences of both monocytes and CD4⁺ T cells from sample I from each patient. Dots indicate identity with the consensus sequences and dashes indicate deletions. Amino acids at positions 11 and 25 of the V3 loop are shaded; positively charged amino acids (R or K) at these two positions are shown in bold.

FIG. 3.

Deduced amino acid sequences of HIV-1 V3 loops from patients 1 to 5. The amino acid sequences have been aligned with the consensus sequences of both monocytes and CD4⁺ T cells from sample I from each patient. Dots indicate identity with the consensus sequences and dashes indicate deletions. Amino acids at positions 11 and 25 of the V3 loop are shaded; positively charged amino acids (R or K) at these two positions are shown in bold.