Structural equation modelling of viral tropism reveals its impact on achieving viral suppression within 6 months in treatment-naive HIV-1-infected patients after combination antiretroviral therapy

Abstract

Objectives: To evaluate the role of pre-treatment co-receptor tropism of plasma HIV on the achievement of viral suppression (plasma HIV RNA 1.69 log10 copies/mL) at the sixth month of combination antiretroviral therapy (cART) in a cohort of naive patients using, for the first time in this context, a path analysis (PA) approach. Patients and methods: Adult patients with chronic infection by subtype B HIV-1were consecutively enrolled from the start of first-line cART (T0). Genotypic analysis of viral tropism was performed on plasma and interpreted using the bioinformatic tool Geno2pheno, with a false positive rate of 10%. A Bayesian network starting from the viro-immunological data at T0 and at the sixth month of treatment (T1) was set up and this model was evaluated using a PA approach. Results: A total of 262 patients (22.1% bearing an X4 virus) were included; 178 subjects (67.9%) achieved viral suppression. A significant positive indirect effect of bearing X4 virus in plasma at T0 on log10 HIV RNA at T1 was detected (P=0.009), the magnitude of this effect was, however, over 10-fold lower than the direct effect of log10 HIV RNA at T0 on log10 HIV RNA at T1 (P=0.000). Moreover, a significant positive indirect effect of bearing an X4 virus on log10 HIV RNA at T0 (P=0.003) was apparent. Conclusions: PA overcame the limitations implicit in common multiple regression analysis and showed the possible role of pre-treatment viral tropism at the recommended threshold on the outcome of plasma viraemia in naive patients after 6 months of therapy.