A skewed maturation of HIV-specific CD4+ and CD8+ T-cells has been observed in HIV-infected patients, involving defective memory cell production and increasing defects in effector cell function, in conjunction with lack of antigen clearance [14–19]. Additionally, a selective loss of HIV-1 specific central memory CD4+ T cells, associated with an expanded monophenotypic CD4+ CD45RA2CCR72 response has been demonstrated, and there is strong evidence of the development of antigen-specific CD8+ T cells biased towards an effector, rather than a central memory phenotype. These phenotypic findings have been associated with the lack of control of the immune system on viral replication, owing to the fact that, in HIV infection, CD45RA2CCR72 CD4+ T cells are functionally characterized by low-IL-2/high interferon(IFN)-c production and minimal proliferative ability, and CD45RA2CCR72 CD8+ T cells are endowed with lower content of lysis molecules, low proliferative ability, and altered cytokine production and ability [20–26]. Limited information is available regarding the phenotypic and functional heterogeneity of CD4+ and CD8+ T cells regenerating after high dose chemotherapy and ASCT; and to date no comprehensive characterization of maturative patterns has risen in these patients. The aim of our study was to compare phenotypic and functional patterns of T-cells in ASCT recipients and in HIV- infected subjects, with comparable CD4+ lymphopenia but with starkly contrasting infectious risks. Results Study groups Ten age-matched subjects with comparable CD4+ lymphopenia were recruited: 5 cancer patients receiving ASCT 9 months before observation (ASCT) and 5 HIV+ antiretroviral na¨ıve subjects (HIV). Demographic and clinical data are presented in Table 1. According to institutional review board-approved chemotherapy protocols, high-dose chemotherapy for cancer patients consisted of ICE, ifosfamide (12 g/m 2 ), carboplatin (1800 mg/m2) and etopo- 2 side (2 g/m ), for breast cancer patients (n = 2) and melphalan (cumulative dose 200 mg/m2) for multiple myeloma patients (n = 3). Febrile neutropenia was observed in 4/5 (80%) ASCT recipients during pre-engrafment phase and has been treated with large-spectrum empiric antibiotic. No opportunistic infections were observed in ASCT recipients until time of the analysis. Of HIV-infected patients, 4/5 had opportunistic infections during the six months previous to observation (2 patients esophageal candidiasis, 1 patient bacterial pneumonia and oropharingeal candidiasis and 1 patient thoracic VZV and oropharingeal candidiasis). Sulphamethoxazole/trimethoprim was administered as Pneumocystis jiroveci pneumonia prophylaxis to ASCT recipients and HIV-infected subjects with less than 200/mL CD4+ at observation. At time of the analysis, ASCT recipients and HIV- infected patients displayed comparable CD4+ absolute number and percentage: ASCT recipients 230/ml (range 164–300), 16% (range 10–25); HIV+ 255/ml (range 189–300), 17% (range 11–20) (p.0.05). CD8 lymphocytes absolute count and percentage did not show significant differences between the two groups: ASCT recipients 670/ml (range 496–919), 54% (range 48–69); HIV+ 658/ml (range 540–823), 51% (range 47–62) (p.0.05). Comparison of lymphocytes subsets phenotype and func- tional studies was made to data obtained from age-matched healthy subjects (n = 5) used as controls (HC), who displayed CD4+ and CD8+ absolute count and percentage within the normality range: CD4+ 1098/ml (range 797–2365), 45% (range 35.9–66.9); CD8+ 475 (range 447–628), 18.3% (range 17.7–21.3). Lymphocytes in ASCT and HIV Table 1. Characteristics of the ASCT (Group A) and HIV- infected patients (Group B). Inclusion criteria CD4+ counts (cell/mL) Actual opportunistic infections No Current HAART Neoplasia’s relapse Baseline characteristics Age (years) median range median range median range median range median range median range Actual CD4+ T cells/mL Actual CD4+ % Actual CD8+ T cells/mL Actual CD8+ T % CD4/CD8 ratio Group A (n = 5) ,300 Non applicable No 48 40–59 255 189–300 17 11–20 658 540–823 51 47–62 0.34 0.24–0.52 Group B (n = 5) ,300 No No Non applicable 43 36–60 230 164–300 16 10–25 670 496–919 54 48–69 0.29 0.15–0.58 p ns ns ns ns ns ns doi:10.1371/journal.pone.0003616.t001 CD4+ lymphocytes maturation patterns are skewed in ASCT recipients and in HIV-infected patients We investigated phenotypical maturation pattern of lympho- cytes in ASCT recipients and in HIV patients, analyzing cells based on the expression of CD45 isoforms and chemokine receptor CCR7. Despite contrasting clinical risk, ASCT recipients displayed a skewed CD4+ phenotype distribution very similar to what observed in HIV-infected subjects (Fig. 1). Indeed, the fraction of na¨ıve CD4+ T cells (CD45RA+CCR7+) was signifi- cantly lower in both population compared to healthy controls (ASCT, 5.49%; HIV, 8.13%;HC, 35,9%; p,0.05 for HC versus ASCT and HIV; p.0.05 for ASCT versus HIV). Moreover, an expansion of effector memory CD45RA2CCR72 cells was seen both in ASCT and in HIV-infected patients with respect to age- matched healthy subjects (ASCT 62.6%; HIV 62.3%; HC 27.8%; p,0.05 for HC versus ASCT and HIV; p.0.05 for ASCT versus HIV), while ASCT recipients displayed the highest levels of effector CD45RA+CCR72 cells (ASCT 11.2%, HIV 2.18%, HC 1.89, p, 0.05 for ASCT versus HC, p.0.05 for ASCT versus HIV). Central memory cells (CD45RA2CCR7+), which have been recognized as the predominant CD4+ subpopulation in healthy controls together with na¨ıve CD4+ T cells, were evidenced at lower frequency in ASCT recipients (8.48%) and HIV-infected subjects (17.9%), with statistical significance in the comparison between ASCT patients and healthy subjects (ASCT 8.48%, HIV 17.9%, PLoS ONE | www.plosone.org 2 October 2008 | Volume 3 | Issue 10 | e3616