Impact of seminal cytomegalovirus replication on HIV-1 dynamics between blood and semen

The genital tract of individuals infected with human immunodeficiency virus type 1 (HIV-1) is an anatomic compartment that supports local HIV-1 and cytomegalovirus (CMV) replication. This study investigated the association of seminal CMV replication with changes in HIV-1 clonal expansion, evolution and phylogenetic compartmentalization between blood and semen. Fourteen paired blood and semen samples were analyzed from four untreated subjects. Clonal sequences (n = 607) were generated from extracted HIV-1 RNA (env C2-V3 region), and HIV-1 and CMV levels were measured in the seminal plasma by real-time PCR. Sequence alignments were evaluated for: (i) viral compartmentalization between semen and blood samples using Slatkin-Maddison and F(ST) methods, (ii) different nucleotide substitution rates in semen and blood, and (iii) association between proportions of clonal HIV-1 sequences in each compartment and seminal CMV levels. Half of the semen samples had detectable CMV DNA, with at least one CMV positive sample for each patient. Seminal CMV DNA levels correlated positively with seminal HIV-1 RNA levels (Spearman P = 0.05). A trend towards an association between compartmentalization of HIV-1 sequences sampled from blood and semen and presence of seminal CMV was observed (Cochran Q test P = 0.12). Evolutionary rates between semen and blood HIV-1 populations did not differ significantly, and there was no significant association between seminal CMV DNA levels and the frequency of non-unique clonal HIV-1 sequences in the semen. In conclusion, the effects of CMV replication on HIV-1 viral and immunologic dynamics within the male genital tract are not significant enough to perturb evolution or disrupt compartmentalization in the genital tract.