BK virus large T and VP-1 expression in infected human renal allografts.

OBJECTIVE: We investigated the expression of early and late phase BK virus (BKV) proteins and their interactions with host cell proteins in renal allografts, with ongoing polyomavirus associated nephropathy (PVAN), and correlated this with the nuclear and cell morphology. METHODS: Frozen sections from three patients with renal allografts (two biopsies, one explant) with PVAN were analysed by indirect immunofluorescence using BKV specific anti-polyoma large T-antigen and anti-VP-1 antibodies, as well as anti-p53, anti-Ki67, anti-caspase-3, anti-bcl2 and anti-cytokeratin 22 antibodies. Nuclear morphology and size were estimated by DNA Hoechst staining. RESULTS: In infected tubular cells the early and late phases of infection could be distinguished according to expression of large T-antigen or VP-1. The early phase revealed almost normal nuclear proportions, whereas in later phases nuclear size increased about 2 to 3 fold. Expression of large T-antigen was strongly associated with accumulation of p53 in the nucleus, accompanied by the activation of the cell cycle associated cell protein Ki67. In contrast, expression of BKV VP1 correlated only weakly with p53. Virus dependent cell lysis was due to necrosis, since neither caspase 3 nor nuclear nor cytoskeleton changes indicated apoptosis. CONCLUSION: In our selected patients with PVAN a clear distinction between early and late phases was possible, according to the protein expression patterns of BKV markers. Striking nuclear enlargement is only present in the late phase of infection. In the inflammatory setting of PVAN, BKV dependent effects appear to be mediated by the inhibition of p53, resulting in the activation of the cell cycle. We assume that in PVAN similar BKV mechanisms are operative as in certain in vitro systems.

Influence of antiretroviral therapy on programmed death-1 (CD279) expression on T cells in lymph nodes of human immunodeficiency virus-infected individuals.

Human immunodeficiency virus infection leads to T-cell exhaustion and involution of lymphoid tissue. Recently, the programmed death-1 pathway was found to be crucial for virus-specific T-cell exhaustion during human immunodeficiency virus infection. Programmed death-1 expression was elevated on human immunodeficiency virus-specific peripheral blood CD8+ and CD4+ T cells and correlated with disease severity. During human immunodeficiency infection, lymphoid tissue acts as a major viral reservoir and is an important site for viral replication, but it is also essential for regulatory processes important for immune recovery. We compared programmed death-1 expression in 2 consecutive inguinal lymph nodes of 14 patients, excised before antiretroviral therapy (antiretroviral therapy as of 1997-1999) and 16 to 20 months under antiretroviral therapy. In analogy to lymph nodes of human immunodeficiency virus-negative individuals, in all treated patients, the germinal center area decreased, whereas the number of germinal centers did not significantly change. Programmed death-1 expression was mostly found in germinal centers. The absolute extent of programmed death 1 expression per section was not significantly altered after antiretroviral therapy resulting in a significant-relative increase of programmed death 1 per shrunken germinal center. In colocalization studies, CD45R0+ cells that include helper/inducer T cells strongly expressed programmed death-1 before and during therapy, whereas CD8+ T cells, fewer in numbers, showed a weak expression for programmed death-1. Thus, although antiretroviral therapy seems to reduce the number of programmed death-1-positive CD8+ T lymphocytes within germinal centers, it does not down-regulate programmed death-1 expression on the helper/inducer T-cell subset that may remain exhausted and therefore unable to trigger immune recovery.

Detection of the complement degradation product C4d in renal allografts: diagnostic and therapeutic implications.

The immunohistochemical detection of the complement degradation product C4d, a component of the classical complement pathway, offers a new and currently poorly defined tool in the evaluation of renal allograft biopsies. Our retrospective study aims at determining the diagnostic and clinical significance of C4d accumulation in kidney transplants, employing immunofluorescence microscopy. We analyzed 398 diagnostic allograft biopsies (n = 265 patients with 1 to 5 biopsies obtained 7 to 7165 d posttransplantation [tx]) and correlated the detection of C4d with 18 histologic changes, panel-reactive antibody titers, response to treatment, and outcome. One hundred twenty-five native kidney and baseline tx biopsies served as controls. Linear deposition of C4d along peritubular capillaries was only found in a subgroup (30%) of allografts post-tx, mainly during the early time-course (median, 38 d post-tx; range, 7 to 5646 d). There was no significant association with infections. C4d staining could change from negative to positive and vice versa within days to weeks. The accumulation of C4d was most tightly linked to a morphologic subtype of rejection, transplant glomerulitis (P < 0.0001). In addition, tubular MHC class II expression was correlated with C4d deposition (P < 0.0001). Both features are signs of "acute active rejection." In comparison with C4d-negative controls, 43% of C4d-positive patients showed increased (>10%) panel-reactive antibody titers (versus 19% in the negative group; P = 0.001). C4d positivity was frequently associated with higher serum creatinine levels at time of biopsy (compared with C4d-negative group; P < 0.01). More C4d-positive patients were treated with polyclonal antithymocyte globulins (ATG) or monoclonal anti-CD3 antibodies (OKT3) (P < 0.0001). Outcome did not significantly differ between C4d-positive and C4d-negative groups. In conclusion, the detection of C4d identifies a humoral alloresponse in a subgroup of kidney transplants, which is often associated with signs of cellular rejection, i.e. tx glomerulitis. Allograft dysfunction in C4d-positive rejection episodes is often more pronounced. We provide first evidence that C4d-positive rejection might benefit from intensive therapy, potentially preventing the previously reported high graft failure rate. In addition, we show that a subgroup of C4d-positive cases may not require any immediate therapeutic intervention. The presence of C4d is clinically relevant and should be reported in the histologic diagnosis.

Differential expression of viral Bcl-2 encoded by Kaposi's sarcoma-associated herpesvirus and human Bcl-2 in primary effusion lymphoma cells and Kaposi's sarcoma lesions.

Expression of human herpesvirus 8 viral Bcl-2 protein was demonstrated in spindle cells of late-stage Kaposi's sarcoma lesions but not in primary effusion lymphoma cell lines. In contrast, strong expression of human Bcl-2 was found in stimulated primary effusion lymphoma cells, whereas in Kaposi's sarcoma lesions preferential mononuclear cells, and to a lesser extent spindle cells, stained positive.

Differential diagnosis of kidney transplant rejection and cyclosporin/tacrolimus nephropathy using urine cytology.

A total of 9000 urine samples from 69 kidney transplant recipients were studied for differential diagnoses of transplant rejection and cyclosporin/tacrolimus toxicity. New-Sternheimer and Papanicolaou staining were used to differentiate cells in urine. We also employed an immunocytochemical technique for further identification of exfoliated cells. With New-Sternheimer and Papanicolaou staining, the predominance of proximal tubular cells was useful to differentiate cyclosporin/tacrolimus toxicity from acute rejection in cases of increased serum creatinine level. During rejection episodes, an increased number of mononuclear cells and renal epithelial cells were found. Immunocytochemical analysis showed a significant increase of CD2-, CD4- CD8-, CD25- and HLA-DR-positive cells with rejection. However, there was no relationship between Banff criteria rejection grade and the increase of mononuclear cells.