Epstein-Barr virus-induced human B-cell lymphomas in SCID mice reconstituted with human peripheral blood leukocytes.

Epstein-Barr virus (EBV) infection is associated with immunoblastic B-cell lymphomas in immunosuppressed or human immunodeficiency virus-infected individuals and in SCID mice reconstituted with human peripheral blood leukocytes (hu-PBL-SCID) from EBV-seropositive donors. The risk of tumors appearing in the hu-PBL-SCID mice differs among EBV-seropositive donors. Four different outcomes have been noted: (a) no tumors appear (no incidence donors); (b) tumors appear in a fraction of hu-PBL-SCID mice with a 10-20 week latent period (low- and intermediate-incidence donors); or (c) tumors appear in all hu-PBL-SCID mice within 6-10 weeks (high-incidence donors). The latter category of rapidly appearing tumor invariably involved activation of EBV replication, whereas more slowly growing tumors rarely activated EBV. The results indicate that prospective screening of high-risk individuals in the hu-PBL-SCID model may predict the risk of EBV-associated lymphoma development.

Heterogeneity among Epstein-Barr virus-seropositive donors in the generation of immunoblastic B-cell lymphomas in SCID mice receiving human peripheral blood leukocyte grafts.

Epstein-Barr virus (EBV) is associated with B-cell malignancy in immunosuppressed humans and SCID mice receiving human peripheral blood leukocyte grafts (hu-PBL-SCID). We have further characterized the process of lymphoma development in hu-PBL-SCID mice. We report that EBV-seropositive donors differ markedly in the capacity of their PBL to give rise to immunoblastic lymphomas in SCID mice; some donors (high incidence) generated tumors rapidly in all hu-PBL-SCID mice, other donors (intermediate-low incidence) gave rise to sporadic tumors after a longer latent period (greater than 10 weeks), and some donors failed to produce tumors. B-cell lymphomas arising from high incidence donors were multiclonal in origin, and EBV replication was detected in all tumors. Tumors derived from intermediate-low incidence donors were monoclonal or oligoclonal and often had no evidence of viral replication. All tumors, regardless of the donor, resembled EBV-transformed lymphoblastoid cell lines in surface phenotype but differed from lymphoblastoid cell lines by having less Epstein-Barr nuclear antigen 2 and CD23 expression. The variable patterns of lymphomagenesis seen among different EBV-sero-positive donors may be explained by lower levels of specific immunity to EBV in high incidence donors, permitting activation of EBV replication and potential transformation of secondary B-cell targets. In addition, there may be differences in the transforming potential of EBV infecting different donors. The use of the hu-PBL-SCID model may help predict patients at high risk for posttransplant or acquired immunodeficiency syndrome-associated lymphomas.

EBV-induced human B cell lymphomas in hu-PBL-SCID mice.

Epstein-Barr virus (EBV) infection is associated with Burkitt's lymphoma (BL) in normal individuals and immunoblastic B cell lymphomas in immunosuppressed or HIV-infected individuals. SCID mice reconstituted with human peripheral blood leukocytes (hu-PBL-SCID) from EBV-seropositive donors also may develop spontaneous B cell lymphomas which histologically and phenotypically resemble post-transplant tumors, and are distinct from BL. These tumors always contain EBV DNA. We have noted three different reproducible outcomes depending upon the EBV-seropositive donor used for generation of hu-PBL-SCID mice: (i) no tumors appear; (ii) tumors appear in a fraction of hu-PBL-SCID mice with a 10-20 wk. latent period; or (iii) tumors appear in all hu-PBL-SCID mice within 6-10 wk. Southern blot analysis of late versus early tumors using a probe specific for the EBV terminal repeat sequences (BamNJ), which allows distinction between circular latent and linear replicating genomes, shows that late tumors do not involve active EBV replication but that early tumors do show replicating genomes. In addition, EBV genomes were monoclonal in late tumors but polyclonal in early tumors. These data suggest two mechanisms for EBV lymphomagenesis, slow outgrowth of rare latently-infected B cells, and more rapid transformation of uninfected bystander B cells by replicating virus. The latter process may be highly amenable to therapy in patients at risk for EBV-related lymphomas. In addition, prospective screening of EBV-seropositive transplant recipients in the hu-PBL-SCID model may predict the risk of post-transplant lymphoma development.

Epstein-Barr virus nuclear protein 2 is a critical determinant for tumor growth in SCID mice and for transformation in vitro.

Injection of Epstein-Barr virus (EBV)-transformed human lymphoblastoid B cells into immunodeficient SCID mice results in the appearance of rapidly growing, fatal human B-cell tumors. To evaluate the role of EBV nuclear protein 2 (EBNA-2) in this process, we generated lymphoblastoid cell lines transformed by several EBV mutants which were identical except for deletions in the EBNA-2 gene (J. I. Cohen, F. Wang, and E. Kieff, J. Virol. 65:2545-2554, 1991). These cell lines were injected intraperitoneally into SCID mice, and the interval until tumor detection was determined. Cell lines transformed with EBV type 1 (strain W91) or with EBV type 2 (strain P3HR-1) with an inserted type 1 EBNA-2 gene grew at the same rapid rate, indicating the potential importance of EBNA-2 for tumor formation in vivo. Cell lines derived from three different EBV mutants with deletions in the amino half of EBNA-2 produced tumors more slowly than cell lines transformed by wild-type W91 virus. In contrast, a cell line transformed with an EBV mutant with a deletion in the carboxy terminus of EBNA-2 grew more rapidly than cell lines transformed by wild-type virus. EBV mutants with deletions in the amino half of EBNA-2 had had reduced transforming activity in vitro, while the carboxy-terminal EBNA-2 mutant had had transforming activity greater than or equal to that of the wild type. These data indicate that EBNA-2 plays a critical role both for B-cell tumor growth in SCID mice and for B-lymphocyte transformation in vitro.

Chemokine receptor CCR5 genotype influences the kinetics of human immunodeficiency virus type 1 infection in human PBL-SCID mice.

Individuals homozygous for a 32-bp deletion (delta 32) in the CCR5 gene encoding the coreceptor for macrophage-tropic human immunodeficiency virus type 1 (HIV-1) are resistant to virus infection, and heterozygous individuals show some slowing of disease progression. The impact of the CCR5 genotype on HIV-1 infection was assessed in vitro and in the human PBL-SCID (hu-PBL-SCID) model. Cells and hu-PBL-SCID mice from CCR5 delta 32/delta 32 donors were resistant to infection with macrophage-tropic HIV-1 and showed slower replication of dual-tropic HIV-1. hu-PBL-SCID mice derived from CCR5 delta 32/+ heterozygotes showed delayed replication of macrophage-tropic HIV-1 despite a small and variable effect of heterozygosity on viral replication in vitro. The level of CCR5 expression appears to limit replication of macrophage-tropic and dual-tropic HIV-1 strains in vivo.

Enhanced tumorigenicity of an Epstein-Barr virus-transformed lymphoblastoid cell line is associated with a unique 1:18 chromosomal translocation and decreased expression of lymphocyte function associated antigen-1a (CD11A).

An Epstein-Barr virus-transformed lymphoblastoid cell line was identified that disseminated to multiple organs and grew rapidly when transplanted to severe combined immunodeficient mice. This pattern of growth more closely resembled that of Burkitt's lymphoma cells than that of all other lymphoblastoid cell lines tested. Analysis of the rapidly growing lymphoblastoid cell line showed two distinctive changes. First, all of the cells derived from the tumor had a 1:18 chromosomal translocation [t(1;18)(p32.1;q23.3)]. Second, the lymphoblastoid cell line down-regulated expression of lymphocyte function associated antigen-1a during passage in severe combined immunodeficient mice, but regained expression upon growth in vitro. These two changes seem sufficient to explain the enhanced tumorigenicity of this cell line and may represent examples of changes that lead to more aggressive lymphomas in posttransplant lymphoproliferative disease.

The cell tropism of human immunodeficiency virus type 1 determines the kinetics of plasma viremia in SCID mice reconstituted with human peripheral blood leukocytes.

Most individuals infected with human immunodeficiency virus type 1 (HIV-1) initially harbor macrophage-tropic, non-syncytium-inducing (M-tropic, NSI) viruses that may evolve into T-cell-tropic, syncytium-inducing viruses (T-tropic, SI) after several years. The reasons for the more efficient transmission of M-tropic, NSI viruses and the slow evolution ofT-tropic, SI viruses remain unclear, although they may be linked to expression of appropriate chemokine coreceptors for virus entry. We have examined plasma viral RNA levels and the extent of CD4+ T-cell depletion in SCID mice reconstituted with human peripheral blood leukocytes following infection with M-tropic, dual-tropic, or T-tropic HIV-1 isolates. The cell tropism was found to determine the course of viremia, with M-tropic viruses producing sustained high viral RNA levels and sparing some CD4+ T cells, dual-tropic viruses producing a transient and lower viral RNA spike and extremely rapid depletion of CD4+ T cells, and T-tropic viruses causing similarly lower viral RNA levels and rapid-intermediate rates of CD4+ T-cell depletion. A single amino acid change in the V3 region of gp120 was sufficient to cause one isolate to switch from M-tropic to dual-tropic and acquire the ability to rapidly deplete all CD4+ T cells.

Donor- and ligand-dependent differences in C-C chemokine receptor 5 reexpression.

N-terminal modifications of the chemokine RANTES bind to C-C chemokine receptor 5 (CCR5) and block human immunodeficiency virus type 1 (HIV-1) infection with greater efficacy than native RANTES. Modified RANTES compounds induce rapid CCR5 internalization and much slower receptor reexpression than native RANTES, suggesting that receptor sequestration is one mode of anti-HIV activity. The rates of CCR5 internalization and reexpression were compared using the potent n-nonanoyl (NNY)-RANTES derivative and CD4(+) T cells derived from donors with different CCR5 gene polymorphisms. NNY-RANTES caused even more rapid receptor internalization and slower reexpression than aminooxypentane (AOP)-RANTES. Polymorphisms in the promoter and coding regions of CCR5 significantly affected the receptor reexpression rate after exposure of cells to NNY-RANTES. These observations may be relevant for understanding the protective effects of different CCR5 genotypes against HIV-1 disease progression.

Anti-class II antibodies in AIDS patients and AIDS-risk groups.

The specificity of anti-lymphocyte antibodies was evaluated in AIDS patients and in individuals at risk of AIDS [R-AIDS: male homosexuals (Ho) and haemophiliacs (He)]. Antibodies capable of inducing antibody-dependent cell-mediated cytotoxicity (ADCC) against non-T cells and lymphoblastoid cell lines (P3HR-1K and Raji) were detected in AIDS patients and in R-AIDS with positive or negative human immune deficiency virus (HIV) serology. Anti-class II antigen specificity was revealed by experiments in which class II antigens on target cells were blocked with monoclonal anti-class II antibody (DA6,231) and the cytotoxic reaction induced by patient's sera was abolished. In contrast, ADCC was not impaired by preincubating the target cells with anti-class I monoclonal antibody (W6/32). Prevalence of antibodies to non-T cells was confirmed by standard C-mediated microlymphocytotoxicity. However, with this technique anti-T lymphocyte cytotoxicity was also observed in three AIDS patients with haemophilia. R-AIDS peripheral blood mononuclear cells (PBMC) were also cytotoxic against autologous non-T cells, and lysis was slightly increased by sensitization of the target cells with autologous serum. In addition to ADCC and C-mediated cytotoxicity, the specificity of anti-lymphocyte antibodies was assayed by their ability to interfere the binding of fluorescein-labelled anti-class II (HLA-DR) and anti-class I (W6/32) monoclonal antibodies to PBMC, non-T cells, P3HR-1K and Raji. Anti-class II specificity was confirmed, and antibody titres tended to be higher in Ho than in He R-AIDS, using non-T cells and Raji as targets. Higher titres of anti-class II antibodies in the Ho group could play a role in the different susceptibility of HIV-infected Ho when compared to HIV (+) He to develop AIDS.

The KSHV/HHV8-infected BCBL-1 lymphoma line causes tumors in SCID mice but fails to transmit virus to a human peripheral blood mononuclear cell graft.

The body-cavity-based lymphoma cell line BCBL-1, which is infected with Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8, was injected alone or with human peripheral blood mononuclear cells into SCID mice. Immunoblastic lymphomas developed at or near the site of injection. The lymphomas appeared to derive exclusively from the injected BCBL-1 cells and not from the injected human PBMC. The tumors elicited a marked murine angiogenic response, but known angiogenic cytokines were not detected in BCBL-1 cells. Transfer of BCBL-1 cells to SCID mice may represent an in vivo model for the study of KSHV/HHV8-stimulated angiogenesis.

Hepatitis C (HCV) genotype and viral titer distribution among Argentinean hemophilic patients in the presence or absence of human immunodeficiency virus (HIV) co-infection.

Hepatitis C (HCV) infection is frequent among hemophilic patients treated with non-inactivated factor-concentrates. Both HCV genotype and viral load have been suggested to be important prognostic markers of disease progression and treatment outcome. In addition, co-infection with the human immunodeficiency virus (HIV) has been associated with increased level of HCV replication and higher risk of developing liver failure. Thus, HCV genotype, viral load, and HIV co-infection are important factors in HCV infection. Using restriction fragment length polymorphism analysis (RFLP) and the branched-DNA (bDNA) assay, we retrospectively investigated the HCV genotypes and viral loads present in 59 Argentinean hemophiliacs, in the presence or absence of HIV infection. HCV genotype 1 was the predominant viral variant detected among HIV-negative (HIV-) (76%) and HIV-positive (HIV+) (82.5%) patients, followed by genotypes 3 (10.4%), 2 (2%) and a small proportion of multiply co-infected patients including genotypes 4 and 5 (6.25%). HIV+ patients had higher plasma HCV RNA levels than HIV- patients (88.4 +/- 16.5 x 10(5) Eq/ml vs. 24.7 +/- 10(5) Eq/ml) (P < 0.001); however, no correlation between HCV replication and level of immune suppression, evaluated by CD4+ T-cell measurement, was observed among HIV+ patients (r = 0.017). Abnormal and higher ALT levels were more frequently detected among HIV+ (93%; 123.6 +/- 15.7 U/liter) than HIV- (41%; 70.2 +/- 24.2 U/liter) patients (P < 0.001; P < 0.05). Although we were able to confirm previous reports suggesting the existence of increased HCV replication in HIV/HCV co-infected hemophiliacs, our data did not support the conclusion that HIV-induced immune suppression is directly responsible for this phenomena. It is possible that other factors induced by HIV are responsible for the increased levels in HCV replication observed.

PIP: Hepatitis C virus (HCV) infection is widespread among hemophiliacs treated with non-inactivated factor concentrates. The HCV genotypes and viral loads present in 59 hemophiliacs from Argentina were investigated through use of restriction fragment length polymorphism analysis and the branched DNA assay. 30 subjects were also infected with HIV. In both HIV-positive and HIV-negative hemophiliacs, HCV genotype 1 was the predominant viral variant (82.5% and 76%, respectively), followed by genotypes 3 and 2. HIV-positive hemophiliacs had significantly higher mean HCV viral loads than HIV-negative hemophiliacs; however, there was no association between HCV replication and the level of immune suppression as evaluated by CD4 T-cell measurement. Although HCV replication was increased in individuals co-infected with HCV and HIV, the data did not support the hypothesis that HIV-induced immune suppression is directly responsible for this finding. A study currently underway is investigating a possible correlation between infecting HCV genotype or pre-existing viral load and the severity of disease as assessed by liver histology or treatment outcome.

Highly potent RANTES analogues either prevent CCR5-using human immunodeficiency virus type 1 infection in vivo or rapidly select for CXCR4-using variants.

The natural ligands for the CCR5 chemokine receptor, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and RANTES (regulated on T-cell activation, normal T-cell expressed and secreted), are known to inhibit human immunodeficiency virus (HIV) entry, and N-terminally modified RANTES analogues are more potent than native RANTES in blocking infection. However, potent CCR5 blocking agents may select for HIV-1 variants that use alternative coreceptors at less than fully inhibitory concentrations. In this study, two N-terminal chemical modifications of RANTES produced by total synthesis, aminooxypentane (AOP)-RANTES[2-68] and N-nonanoyl (NNY)-RANTES[2-68], were tested for their ability to prevent HIV-1 infection and to select for coreceptor switch variants in the human peripheral blood lymphocyte-SCID mouse model. Mice were infected with a CCR5-using HIV-1 isolate that requires only one or two amino acid substitutions to use CXCR4 as a coreceptor. Even though it achieved lower circulating concentrations than AOP-RANTES (75 to 96 pM as opposed to 460 pM under our experimental conditions), NNY-RANTES was more effective in preventing HIV-1 infection. However, in a subset of treated mice, these levels of NNY-RANTES rapidly selected viruses with mutations in the V3 loop of envelope that altered coreceptor usage. These results reinforce the case for using agents that block all significant HIV-1 coreceptors for effective therapy.

Neutralizing antibodies have limited effects on the control of established HIV-1 infection in vivo.

Neutralizing antibodies can protect against challenge with HIV-1 in vivo if present at appropriate concentrations at the time of viral challenge, but any role in the control of established infection is unclear. Here, we show that high serum concentrations of neutralizing monoclonal antibodies, either singly or as a cocktail, have little sustained effect on viral load in established HIV-1 infection in hu-PBL-SCID mice. In some instances, virus replication of neutralization-sensitive virus continues even in the presence of high levels of neutralizing antibody. In most instances, neutralization escape occurs in a few days, even from a cocktail of three antibodies that recognize distinct epitopes. The results imply that humoral immunity is unlikely to play a significant role in the control of established HIV-1 infection in humans.

Impaired response to alloantigens in HIV positive hemophilic patients.

The alloantigen responses of hemophilic patients was evaluated using a unidirectional mixed lymphocyte culture (MLC). The results of this study indicate that both the ability of peripheral blood mononuclear cells (PBMC) to proliferate in response to alloantigens and the capacity to stimulate the MLC are impaired in hemophilic patients infected with the human immune deficiency virus (HIV). These defects cannot be overcome by addition of exogenous interleukin-2 (IL-2) and are not related to the absence of IL-2 receptors (IL-2R). Lack of response was evident in PBMC from HIV+ patients with a high proportion of IL-2R+ cells. The number of IL-2 cells was similar in HIV+ and HIV- individuals, and higher than that of normal controls. Impaired MLC proliferation was not related to the occurrence of clinical symptoms. Apparently, MLC is a useful procedure for distinguishing the cell mediated immunity defects associated with HIV infection and unrelated to replacement therapy in hemophilia patients.

Altered viral fitness of HIV-1 following failure of protease inhibitor-based therapy.

HIV-1 isolated from patients with improved CD4+ T-cell counts despite virologic failure on a nucleoside reverse transcriptase inhibitor (NRTI) and protease inhibitor (PI)-containing regimen were characterized. Five paired virus isolates from patients before and after zidovudine, lamivudine, and ritonavir treatment were tested. Human peripheral blood leukocyte-reconstituted severe combined immunodeficient (hu-PBL-SCID) mice were infected with pre-or posttreatment isolates and plasma HIV-1 RNA levels and CD4+ T cells were measured. Two of five post-treatment isolates exhibited decreased replication in hu-PBL-SCID mice compared with the paired pretreatment isolate, and both had the V82A mutation in protease associated with resistance to PI. One additional posttreatment isolate with the M184V mutation in reverse transcriptase showed diminished replication. CD4+ T-cell depletion was similar following infection with either the pre-or posttreatment isolates. Subtle losses in the replication capacity of PI-or NRTI-resistant viruses may contribute to relative preservation of CD4+ T-cell counts in persons who experience virologic failure. Cytopathic effects of viral infection for target T cells vary from patient to patient but appear not to be influenced by mutations associated with failure of therapy in this system.

Evaluación de la inmunoflurescencia indirecta como ensayo confirmatorio en el diagnóstico serológico de la infección por el virus de la inmunodeficiencia humana (HIV) / Evaluation of indirect immunofluorescence as a confirmatory assay in the serological diagnosis of infection by human immunodeficiency virus (HIV)

Se compartó la técnica de inmunofluorescencia indirecta (IFI) con la Western Blot (WB) como método confirmativo en muestras repetidamente reactivas por enzimoinmunoensayo (EIE) para anticuerpos contra el virus de la inmunodeficiencia humana (HIV. Se estudairon 102 muestras de suero correspondientes a pacientes de alto riesgo; 59 hemofílicos, 38 hemosexuales, 5 SIDA. Mediante la técnica de IFI con células CEM, 36 muestras resultaron reactivas y 66 negativas. La coincidencia entre ambos métodos fue del 99%. Cuando se utilizó el EIE, 47 muestrasresultaron ser repetidamente reactivas y 55 negativas. La coincidencia observada entre las técnicas de EIE y de WB fue del 88,2%. Mediante el EIE, 12 muestras resultaron ser falsamente reactivas. mediante la técnicas de IFI se estudiaron 45 sueros control, y ninguna de las muestras presentó reactividad. Estos resultados permiten establecer que la IFI con células es un método alternativo del WB para la confirmación de muestras repetidamente reactivas por EIE