Background:Among HlV-infected patients initiating antiretroviral therapy (ART),early changes in CD4+ T-cell subsets are well described.However,HIV-infected late presenters initiating treatment present with a suboptimal CD4+ T-cell reconstitution and remain at a higher risk for AIDS and non-AIDS events.Therefore,factors associated with CD4+ T-cell reconstitution need to be determined in this population,which will allow designing effective immunotherapeutic strategies.Methods:Thirty-one adult patients with baseline CD4+ T-cell count ＜350 cells/mm3 exhibiting viral suppression after ART initiation were followed in the HIV/AIDS research center of Peking Union Medical College Hospital in Beijing,China,from October 2002 to September 2013.Changes in T-cell subsets and associated determinants were measured.Results:Median baseline CD4+ T-cell count was 70 cells/mm3.We found a biphasic reconstitution ofT-cell subsets and immune activation:a rapid change during the first 6 months followed by a more gradual change over the subsequent 8 years.Baseline CD4+ T-cell count ＞200 cells/ mm3 in comparison to CD4+ T-cell count ≤200 cells/mm3 was associated with more complete immune Reconstitution (77.8％ vs.27.3％ respectively;P =0.017) and normalized CD4/CD8 ratio.We showed that the baseline percentage of naive CD4+ T-cell was a predictive marker for complete immune reconstitution (area under receiver operating characteristic curve 0.907),and 12.4％ as cutoffvalue had a sensitivity of 84.6％ and a specificity of 88.2％.Conclusions:Baseline naive CD4+ T-cell percentage may serve as a predictive marker for optimal immune reconstitution during long-term therapy.Such study findings suggest that increasing thymic output should represent an avenue to improve patients who are diagnosed late in the course of infection.