Objective: To compare the distribution of R5-like and X4-like HIV-1 envelope sequences in plasma and peripheral blood mononuclear cell (PBMC).
Methods: Clonal sequencing of the HIV-1 glycoprotein 120 region was performed on PBMC DNA and plasma RNA of 11 HIV-1 subtype B-infected patients with high probability of carrying X4 virus. Coreceptor use was predicted using the position-specific scoring matrix (PSSM).
Results: A total of 330 and 427 clonal envelope sequences were obtained from PBMC and plasma, respectively. PSSM interpretation revealed the presence of a mixture of predicted X4 and R5 sequences in 10 patients and pure R5 sequences in 1. The X4 sequences were significantly more represented in PBMC (with an average of 52.2% of the clonal proviral sequences scored X4) compared with plasma (19.7% X4 sequences) (P < 0.0001). At the single patient level, the higher representation of X4 sequences in PBMC reached statistical significance (P < 0.002) in 6 individuals.
Conclusions: Mixtures of X4 and R5 sequences with highly divergent PSSM scores are present in both plasma and PBMC, but a shift toward a more abundant representation of X4-like PSSM scores in PBMC-derived DNA was apparent. Additional studies are needed to evaluate the clinical importance of these findings with regard to tropism prediction and the use of CCR5 antagonists.