Objective: To compare residual viral replication and evolution in lymph nodes (LN) and peripheral blood (PB) of patients (pts) with sustained control of viremia during different treatment strategies.

Methods: Analyses were performed on axillary LN biopsies and PB of 32 pts achieving sustained control of viremia (< 25 copies/ml for a mean of 18 mos) during HAART with 2–3 NA alone (n = 7), 2 NA + NNRTI (n = 11) or 2 NA + PI (n = 14). Residual viral replication in LN was studied by in situ hybridization and immune reconstitution by immune histochemistry and FACS analyses (proliferation and activation markers). Viral evolution was assessed by sequencing and phylogenetic analyses of RT and protease genes directly from infected LN derived MNC or supernatants after co-culture with donor PBMC and compared to PB.

Results: Productively infected cells were detected in LN of all pts with large inter-individual differences. Strikingly more FDC trapped virions and RNA⁺ T-cells (not macrophages) were present in LN of pts treated with NA alone as compared to those who received NA combined with either NNRTI or PI. Virus was co-cultured from LN in 4/11 cases, 3 of which received NA alone (one case 2 NA + SQV - HGC). Sequence analyses revealed typical resistance mutations (184V, 215Y) against NA which were actually applied. One additional 184V mutation was detected in the LN of a pt with intermittent viral blips during therapy with CBV/ABC and one 106A mutation in a pt receiving CBV/IND, both of which were not present in the corresponding PBMC sample. Phylogenetic analyses showed sequence homology (> 95%) in the other cases between LN and PB-derived viruses. The expression of activation maskers and T-cell proliferation were comparable to normal controls except the cases with abundant residual viral RNA in LN. However, immune reconstitution was more complete in LN of pts receiving additional NNRTI or PI.

Conclusions: Residual viral replication is frequently observed in LN of pts despite prolonged control of viremia by HAART. However, viral evolution with subsequent development of drug resistance mutations occurs only in a subset of pts with suboptimal response in LN. In these subjects, regimens containing NA alone appear inferior to NNRTI or PI-based therapies.