Biomedical subjects

M Rowe

Publications and source records attributed to M Rowe.

At least 73 records · Page 4Linked to original sources

PubMed1996

Expression of the Epstein Barr virus transforming protein LMP1 causes a rapid and transient stimulation of the Bcl-2 homologue Mcl-1 levels in B-cell lines.

The EBV-encoded latent membrane protein 1 (LMP1) suppresses apoptosis in B lymphocytes through up-regulation of Bcl-2. However, the maximum induction of Bcl-2 by LMP1 takes about 48-72 h. We show in this report that up-regulation of the Bcl-2 homologue Mcl-1 by LMP1 preceded the induction of Bcl-2 and that the up-regulation was transient; therefore, Mcl-1 levels decreased when Bcl-2 levels started to increase. This finding supports the hypothesis that Mcl-1 functions as a rapidly inducible, short-term effector of cell viability. LMP1 also blocked the decline in the Mcl-1 levels in response to apoptotic stimulation triggered by elevated cyclic AMP. This effect of LMP1 was associated with a delayed cell death in the EBV-negative Burkitt lymphoma cell line BL41. The maintenance of Mcl-1 expression by LMP1 is likely to be a crucial immediate-early response that enables cells to survive until Bcl-2 can be up-regulated.

Apoptosis↗

PubMed1996

Cytostatic effect of Epstein-Barr virus latent membrane protein-1 analyzed using tetracycline-regulated expression in B cell lines.

Tetracycline-regulated vectors were used to obtain inducible expression in stable transfected B cell lines of two Epstein-Barr virus (EBV) latent genes, LMP1 and EBNA2. The transfected genes were tightly repressed by low, nontoxic concentrations of tetracycline (< or = 1 microgram/ml) and, following removal of tetracycline, were induced to levels comparable to or up to 3x that of EBV-transformed normal lymphoblastoid cell lines. In transfected DG75 cells, induced expression of LMP1, but not of EBNA2, led to the expected upregulation of various cell surface markers, including: CD40, CD54, CD58, and HLA class I.A novel observation was that both LMP1 and EBNA2 independently caused the downregulation of surface IgM, an effect mirrored in EBV-positive Burkitt lymphoma lines undergoing phenotypic drift during the transition from latency I to latency III in which both LMP1 and EBNA2 are upregulated. Most remarkably, induced LMP1 expression almost completely inhibited cell growth for 4 to 5 days, after which the cells recovered a limited proliferative capacity. The cytostatic effect of LMP1 was observed in all three B cell lines studied: DG75, BJAB, and Akata. Further analysis showed that induction of LMP1 coincided with a reduction in the levels of c-myc, and that the cytostatic effect was due to an accumulation of cells at the G2/M phase of the cell cycle. These data suggest a novel function for the LMP1 oncogene in controlling the proliferation of EBV-infected cells by regulating progress through G2/M phase.

Antigens, Surface↗

PubMed1996

A taxonomic study of the genus Listeria using sodium dodecyl sulphate-polyacrylamide gel electrophoresis of intracellular proteins.

Fifty-one strains of Listeria spp. and one strain of Jonesia denitrificans were subjected to sodium dodecyl sulphate-polyacrylamide gel electrophoresis and the resulting histograms compared using the unweighted pair group method with averaging. The majority of L. monocytogenes strains formed a discrete cluster with a minimum correlation of 73% similarity. The position of strain NCTC 11994 within the main L. monocytogenes cluster supports the recommendation by the National Collection of Type Cultures that it, rather than NCTC 10357, be adopted as the type strain of the species. All L. innocua strains formed a discrete cluster with a minimum correlation of 85% similarity. The similarity shown by L. grayi and L. murrayi, both between each other and with the other Listeria strains tested, support their designation as a single species within the genus Listeria. Although the single strain of J. denitrificans showed the least similarity with the other strains it was not sufficient to warrant support for its removal from the genus Listeria. This limited study provides a different perspective both between species in the genus Listeria and between the genera Listeria and Jonesia.

Bacterial Proteins↗

PubMed1996

Child mortality following standard, medium or high titre measles immunization in West Africa.

BACKGROUND: The World Health Organization (WHO) recommended the use of high titre measles vaccine in 1989. Subsequent long term follow-up of several trials yielded results suggesting higher mortality among children inoculated with medium and high titre vaccines compared to standard titre vaccines, although none of the individual trials found significant differences in mortality. METHODS: Long term survival after standard, medium and high titre measles vaccines has been investigated in a combined analysis of all West African trials with mortality data. In trials from Guinea-Bissau, The Gambia and Senegal, children received medium or high titre vaccines from 4 months of age and were compared to control groups recruited at the same time later receiving standard titre vaccine from 9 months of age. All children were followed up to at least 3 years old. RESULTS: Combining trials of high titre vaccines showed higher mortality among the high titre group compared to the standard group: mortality ratio (MR) = 1.33 (95% CI : 1.02-1. 73). Mortality among recipients of medium titre vaccines was not different from that in the standard vaccine group, MR = 1.11 (95% CI: 0.54-2.27). In a combined analysis by sex, the adjusted mortality ratios comparing high titre vaccine with standard vaccine were 1.86 (95% CI : 1.28-2.70) for females and 0.91 (95% CI : 0.61-1.35) for males. The trials were not designed to study long term mortality. Adjustments for several possible sources of bias did not alter the results. CONCLUSIONS: The combined analysis showed a decreased survival related to high titre measles vaccine compared with standard titre vaccines, though solely among females. As a result of these studies from West Africa and a study from Haiti, WHO has recommended that high titre measles vaccine no longer be used.

Age Distribution↗

PubMed1996

Frequency of multiple Epstein-Barr virus infections in T-cell-immunocompromised individuals.

The Epstein-Barr virus (EBV) carrier state is characterized by latent infection of the general B-cell pool and by chronic virus replication at oropharyngeal sites. In Caucasian populations, most healthy carriers seem to harbor one dominant transforming virus strain, usually of type I rather than type 2, which persists over time and is detectable both in the blood and in the throat. This finding implies that once the virus carrier state is established, both viral reservoirs are largely if not completely protected from infection with additional strains. However, it is not known which facets of the immune response offer that protection. Here we address this question by a detailed study of EBV carriage in patients T-cell immunocompromised as a result of chronic human immunodeficiency virus (HIV) infection. Resident EBV strains were rescued from blood and from throat washings by using an in vitro transformation assay which aims to minimize bias toward faster-growing transformants; in this way, a mean of 16 independent isolations were made from each of 35 HIV-positive (predominantly male homosexual) patients. These virus isolates were characterized first at the DNA level by PCR amplification across type-specific polymorphisms in the EBNA2 and EBNA3C genes and across the 30-bp deletion and 33-bp repeat loci in the LMP1 gene and then at the protein level by immunoblotting for the strain-specific "EBNAprint" of EBNA1, -2, and -3C molecular weights. By these criteria, 18 of 35 patients harbored only one detectable EBV strain, usually of type 1, as do healthy carriers. However, the other 17 patients showed clear evidence of multiple infection with different EBV strains. In eight cases these strains were of the same type, again usually type 1, and were more often found coresident in throat washings than in the blood. By contrast, a further nine patients gave evidence of coinfection with type 1 and type 2 strains, and in these cases both virus types were detectable in the blood as well as in the throat. Immunological assays on these HIV-positive patients as a group showed a marked impairment of T-cell responses, reflected in reduced levels of EBV-specific cytotoxic T-cell memory, but an elevation of humoral responses, reflected in raised antibody titers to the EBV envelope glycoprotein gp340 and by the maintenance of virus neutralizing antibodies in serum. We infer that selective impairment of the T-cell system predisposes the host to infection with additional exogenously transmitted EBV strains.

AIDS-Related Opportunistic Infections↗

PubMed1996

Isolation of intertypic recombinants of Epstein-Barr virus from T-cell-immunocompromised individuals.

All wild-type isolates of Epstein-Barr virus (EBV) analyzed to date for allelic polymorphisms of the nuclear antigen EBNA2 gene (in the BamHI YH region of the genome) and of the EBNA3A,-3B, -3C genes (tandemly arranged in the BamHI E region) have proved either uniformly type 1 or uniformly type 2 at all four loci. The absence of detectable intertypic recombination in the wild probably reflects the rarity with which individual carriers, and certainly individual target cells, become coinfected with both virus types. Studying a group of human immunodeficiency virus-positive T-cell-immunocompromised patients known to be at enhanced risk of multiple EBV infections, we have isolated intertypic EBV recombinants from 2 of 40 patients analyzed. These recombinants, whose in vitro transforming capacity appeared at least equal to that of type 1 strains, carried a type 1 EBNA2 allele and type 2 EBNA3A,-3B, and -3C alleles. This was clearly demonstrable at the DNA level by PCR amplification using type-specific primer-probe combinations and was confirmed at the protein level (for EBNA2 and EBNA3C) by immunoblotting with type-specific antibodies. In one patient, the recombinant appeared to be the predominant strain, being the virus most commonly rescued by in vitro transformation both from the blood and from the throat washings on two separate occasions 20 months apart. A regular type 1 virus strain was also present in this individual, but this was not related to the recombinant since the two viruses carried type 1 EBNA2 genes with different patterns of variance from the B95.8 prototype sequence. In the other patient, recombinants were isolated on one occasion from the blood and on a separate occasion, 21 months later, from the throat; these recombinants were almost certainly related, being identical at several genomic polymorphisms and differing only in one facet of the "EBNAprint," the size of the EBNA1 protein. Three different type 1 viruses were also isolated from this patient, two of which carried EBNA2 genes with the same pattern of sequence variation from B95.8 as the recombinant; however, since this is a fairly common pattern of variance, the relationship of these viruses to the recombinant remains an open question. We infer that intertypic recombinants of EBV are not uncommon in HIV-positive T-cell-immunocompromised patients, that they arise in such individuals as a consequence of their increased frequency of mixed-type infections, and that they will prove capable of efficient transmission in the human population.

Amino Acid Sequence↗

PubMed1996

The application of multiple quality-of-life instruments in individuals with mild-to-moderate psoriasis.

The 36-item Short-Form Health Survey Questionnaire (HSQ SF-36), Psoriasis Disability Index (PDI), and Dermatology Life Quality Index (DLQI) were administered to individuals with mild-to-moderate psoriasis to validate the general quality-of-life instrument against the dermatosis-specific, and the dermatology-specific, disability measure. The population consisted of 644 adults with psoriasis involving up to 20% of the body surface area, who were enrolled in 2 US multicentre, evaluator-blinded, parallel-group clinical trials for a new psoriasis medication. Patients averaged 16.5% of maximum possible disability as measured by the PDI, and 23.4% of maximum possible disability as measured by the DLQI. Normalised T-scores showed that the patients approximated US population means on all 8 of the HSQ SF-36 dimensions. The HSQ SF-36 scales did not reflect substantial quality-of-life impairment, although all showed statistically significant correlations with both the PDI and DLQI (correlation coefficients ranging from -0.13 to -0.45). Moreover, while the disability indices were more responsive to psoriasis characteristics than the HSQ SF-36 quality-of-life scales, all 8 HSQ SF-36 dimensions demonstrated sensitivity to at least some objective and/or subjective ratings of severity. The strongest relationships were observed between the PDI, DLQI and the HSQ SF-36 Mental Health and Social Functioning dimensions, suggesting that the HSQ SF-36 is sensitive to psychosocial suffering related to psoriasis, which is not conveyed in objective clinical measures of severity.

Adolescent↗

PubMed1996

Rectal bleeding in Prader-Willi syndrome.

Individuals with Prader-Willi syndrome manifest severe skin picking behavior. We report three patients with this syndrome in whom an extension of this behavior to rectal picking resulted in significant lower gastrointestinal bleeding and anorectal disease. The recognition of this behavior is important to avoid misdiagnosing inflammatory bowel disease in this group of patients.

Adolescent↗

PubMed1995

Heterogeneous expression of Epstein-Barr virus latent proteins in endemic Burkitt's lymphoma.

Epstein-Barr virus (EBV)-infected cells may sustain three distinct forms of virus latency. In lymphoblastoid cell lines, six EBV-encoded nuclear antigens (EBNA1, 2, 3A, 3B, 3C, -LP), three latent membrane proteins (LMP1, 2A, 2B), and two nuclear RNAs (EBERs) are expressed. This form of latency, termed latency III, is also encountered in some posttransplant lymphoproliferative disorders. In EBV-positive cases of Hodgkin's disease, the EBERs, EBNA1, and the LMPs are expressed (latency II), whereas in Burkitt's lymphoma (BL) only the EBERs and EBNA1 have been detected (latency I). We have studied the expression of EBV proteins in 17 cases of EBV-positive endemic BL by immunohistology. Expression of LMP1 was seen in variable proportions of tumor cells in two cases and EBNA2 was detected in some tumor cells in three other cases. Also, the BZLF1 trans-activator protein was expressed in a few tumor cells in 6 cases, indicating entry into the lytic cycle. A phenotypic drift from latency I to latency III has been observed previously in some BL cell lines. Our results suggest that a similar phenomenon may occur in BL in vivo and indicate that the operational definition of EBV latencies is not easily applied to human tumors.

Adolescent↗

PubMed1995

Class I major histocompatibility complex-restricted cytotoxic T lymphocytes specific for Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines against which they were raised.

We have raised CD8+ cytotoxic T lymphocytes (CTL) from three Epstein-Barr virus-seropositive donors by incubating peripheral blood lymphocytes with irradiated autologous B95.8-strain EBV-transformed B lymphoblastoid cells (LCL). However, to detect lysis in a standard 51Cr release assay of the LCL against which these CTL were raised, superinfection with recombinant vaccinia expressing the appropriate EBV protein or incubation with the peptide epitope was necessary. The untreated LCL were not lysed, even though Western blotting demonstrated that they expressed the EBV antigens containing the CTL epitopes. We have found CTL of this phenotype that are restricted by human leukocyte antigen-A2, -A3, -B7, or -B39, and which recognize the EBV latent proteins, EBV nuclear antigen (EBNA)-3A, EBNA-3C, or terminal protein. During these experiments, we identified a new human leukocyte antigen-A3-restricted EBNA-3A epitope, residues 603-611, RLRAEAGVK. We raised a spontaneous LCL, transformed by endogenous EBV, from one donor, but this was also not lysed. For at least one of the epitopes, CTL from another donor lysed the LCL without superinfection or addition of peptides. We conclude that the CTL were unable to achieve a high enough avidity of interaction with untreated LCL to trigger effector function, although the LCL were able to stimulate them to grow in vitro for up to 4 mo. To assess whether a small percentage of the LCL might possess a higher antigen density, we used an assay of tumor necrosis factor release from a CTL clone, which was able to detect antigen-bearing cells representing only 1% of a stimulating LCL population. Nevertheless, the untreated autologous LCL line failed to stimulate tumor necrosis factor release.

Amino Acid Sequence↗

PubMed1995

Analysis of VH genes used by neoplastic B cells in endemic Burkitt's lymphoma shows somatic hypermutation and intraclonal heterogeneity.

Tumor cell lines from six typical cases of endemic Epstein-Barr virus (EBV) genome-positive Burkitt's lymphoma (BL) have been investigated for usage and mutational pattern of Ig VH genes. The neoplastic cells all had a t(8;14) (q24;q32) translocation involving the c-myc protooncogene. The VH genes were derived from VH1, VH3 and VH4, and both the IgM-positive (four cases) and IgG-positive (two cases) were extensively mutated from germline sequence. In two cases, early and late passage tumor cells were available, and the VH nucleotide sequences were identical, indicating that mutations had not accumulated in vitro. In a further case, there was evidence of sequence heterogeneity, which appeared to have been generated in vivo, indicating that the tumor cell VH gene was able to undergo posttranslocation somatic hypermutation. Analysis of the relatively nonpolymorphic VH4 genes for the pattern of replacement or silent mutations did not show a role for antigen selection in the expressed sequences.

Amino Acid Sequence↗

PubMed1995

The Epstein-Barr virus latent membrane protein-1 (LMP1) mediates activation of NF-kappa B and cell surface phenotype via two effector regions in its carboxy-terminal cytoplasmic domain.

The Epstein-Barr virus (EBV) encoded latent membrane protein, LMP1, is oncogenic in rodent fibroblasts and is an essential effector protein in EBV-induced growth-transformation of human B lymphocytes. Previous structure-function studies with LMP1 have relied largely on rodent fibroblast transformation as a functional readout, with apparently conflicting results. We have now analysed several LMP1 mutants in various human cell types, including B cells, T cells and epithelial cells, using two independent functional assays; (i) activation of NF-kappa B, and (ii) induction of two cell surface activation markers, CD54 and CD40. The results suggest that the cytosolic N-terminus is not essential for LMP1 function in any cell type studied. The third and fourth transmembrane helices and the intracytosolic loops are dispensable for activation of NF-kappa B, but they do influence the induction of CD54 and CD40. The major effector domain appears to be the cytosolic C-terminus in which were identified two 'C-terminal activating regions', CTAR-1 (residues 194-232) and CTAR-2 (residues 351-386). Whilst the exact results depended upon the host cell line, CTAR-2 was generally more important for activation of NF-kappa B, and both CTAR-1 and CTAR-2 were required for optimal induction of CD54 and CD40. Analysis of NF-kappa B activation by LMP1 in Rat-1 fibroblasts indicated that many mutations that were functional in human cells were poorly tolerated in the rodent cells; a result that is in broad agreement with published Rat-1 transformation data.

Animals↗

PubMed1995

Reduction of tissue edema by microdialysis.

OBJECTIVE: This is the first report (to our knowledge) of the use of tissue microdialysis to reduce tissue edema. In this study, a hyperosmotic solution was perfused through microdialysis catheters, allowing direct treatment of interstitial edema by osmosis. DESIGN: First, the catheter and perfusate characteristics were tested in vitro. A physiologic, controlled trial was then performed, with two outcome variables: osmolarity of the effluent and tissue water content. SUBJECTS: Twenty male Sprague-Dawley rats. One rat was withdrawn. INTERVENTIONS: Tissue microdialysis catheters were implanted in the rats. The control side of the animals was not perfused. The experimental side was perfused for 9 hours. RESULTS: Osmolarity of the perfusate was reduced 16.5 mOsm after passing through the catheter, indicating that fluid was removed from the tissue. Tissue edema was reduced by an average 1.8 mL of fluid per 100 g of wet tissue. CONCLUSIONS: Tissue microdialysis removed tissue fluid and reduced edema. This treatment may have a beneficial effect on edematous tissues. Potential use and limitations of this therapeutic modality are discussed.

Animals↗

PubMed1995

Restoration of endogenous antigen processing in Burkitt's lymphoma cells by Epstein-Barr virus latent membrane protein-1: coordinate up-regulation of peptide transporters and HLA-class I antigen expression.

Group I Burkitt lymphoma (BL) lines retaining the original BL tumor cell phenotype are unable to present endogenously expressed antigens to HLA class I-restricted cytotoxic T cells (CTL) but can be recognized if the relevant HLA class I/peptide epitope complex is reconstituted at the cell surface by exogenous addition of synthetic target peptide. Endogenous antigen-processing function is restored in BL lines that have undergone Epstein-Barr virus (EBV)-induced drift in culture to the group III phenotype typically displayed by EBV-transformed lymphoblastoid cell lines (LCL) of normal B cell origin. We compared group I versus group III cells for their expression of proteasome components, transporter proteins and HLA-class I antigens, all of which are thought to be involved in the endogenous antigen processing pathway. By Western blot analysis, there were not consistent differences in the low molecular mass protein subunits of proteasomes (lmp)-2, lmp-7 and delta, although the mb-1 proteasome subunit was regularly present at higher levels in group I BL lines relative to group III lines or LCL. By contrast there were marked differences in the expression of peptide transporter-associated proteins (Tap), with down-regulation of Tap-1 and Tap-2 in 8/8 and 7/8 group I BL lines, respectively. Surface levels of HLA class I antigens were also consistently lower in group I cells; this was not associated with an intracellular accumulation of free HLA heavy chains, such as is seen in the Tap-deficient T2 processing-mutant line, but instead reflected a reduced rate of HLA class I synthesis in group I cells. Analysis of EBV gene transfectants of the B lymphoma lines BJAB and BL41 showed that the virus-encoded latent membrane protein-1 (LMP1), which is one of several EBV antigens expressed in group III but not in group I cells, was uniquely able to up-regulate expression both of the Tap proteins and HLA class I. Furthermore, this was accompanied by a restoration of antigen-processing function as measured by the ability of these cells to present an endogenously expressed viral antigen to CTL. These effects of LMP1 were similar to those induced in the same cell lines by interferon-gamma treatment. The results implicate both Tap and HLA class I expression as factors limiting the antigen-processing function of BL cells, and suggest that the accessibility of other EBV-associated malignancies to CTL surveillance may be critically dependent upon their LMP1 status.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

The association of an HPV16 oncogene variant with HLA-B7 has implications for vaccine design in cervical cancer.

HLA-restricted cytotoxic T-lymphocyte (CTL) recognition of human papillomavirus (HPV) oncogene products may be important in the control of the HPV infections associated with the development of cervical cancer. We have identified, in HLA-B7 individuals, a consistent variation in the HPV16 E6 oncoprotein sequence, which alters an HLA-B7 peptide binding epitope in a way likely to influence immune recognition by CTLs. These results illustrate a biologically relevant mechanism for escape from immune surveillance of HPV16 in HLA-B7 individuals. Thus, both HLA type and HPV16 strain variation need to be considered in the screening of at-risk individuals and for the rational design of anti-HPV vaccines.

Amino Acid Sequence↗

PubMed1995

The role of repetitive DNA sequences in the size variation of Epstein-Barr virus (EBV) nuclear antigens, and the identification of different EBV isolates using RFLP and PCR analysis.

The six Epstein-Barr virus (EBV) nuclear antigen proteins (EBNA-1-6) show characteristic size variations between different virus isolates; this is a feature that has been used to identify the source of virus isolates in epidemiological studies (Ebnotyping). We have now studied the correlation between restriction fragment length polymorphisms (RFLPs) within exons coding for the EBNAs and the molecular masses of the respective proteins. The B95-8 EBV strain was used as the prototype virus. The variation in apparent molecular mass of EBNA-1, -3 and -6 correlated positively with the size of RFLP coding for repeat sequences in these polypeptides. For EBNA-2, no correlation between apparent molecular mass and length of the repetitive sequences was found. The EBNA-4 protein showed virtually no variation in apparent molecular mass and RFLP size across the repeat sequence. Based on the strong correlation between apparent molecular mass and RFLP size for EBNA-6, we developed an EBNA-6 PCR assay that discriminated between different isolates of EBV. This assay offers the advantage of EBV characterization using uncultured material (e.g. throat washings, blood or biopsies), thus avoiding the selection against poorly transforming strains that occurs during establishment of lymphoblastoid cell lines required for Ebnotyping at the protein level.

Animals↗

PubMed1995

Mechanisms for the mechanical plasticity of tracheal smooth muscle.

In smooth muscle tissues, the relationship between muscle or cell length and active force can be modulated by altering the cell or tissue length during stimulation. Mechanisms for this mechanical plasticity were investigated by measuring muscle stiffness during isometric contractions in which contractile force was graded by changing stimulus intensity or muscle length. Stiffness was significantly higher in contracted than in resting muscles at comparable forces; however, the relationship between stiffness and force during force development was curvilinear and independent of muscle length and stimulus intensity. This suggests that muscle stiffness during force development reflects properties of cellular components other than cross bridges which contribute to the series elasticity only during activation. During the tonic phase of isometric contraction, muscle stiffness increased while force remained constant. A step decrease in the length of a contracted muscle resulted in a high level of stiffness relative to force during isometric force redevelopment following the length step. We propose that the arrangement of the cytoskeleton can adjust to changes in the conformation of resting smooth muscle cells but that the organization of the cytoskeleton becomes more fixed upon contractile activation and is modulated very slowly during a sustained contraction. This may provide a mechanism for optimizing force development to the physical conformation of the cell at the time of activation.

Animals↗

PubMed1994

Patterns of Epstein-Barr virus latent and replicative gene expression in Epstein-Barr virus B cell lymphoproliferative disorders after organ transplantation.

B cell lymphoproliferative disorders arising in organ transplant recipients (B cell posttransplant lymphoproliferative disorders [PTLD]) are generally associated with EBV. In previous reports, B cell PTLD were shown to express the full pattern of EBV latent genes, as in vitro-established lymphoblastoid cell lines. Although viral linear DNA was detected in 40% of lymphoproliferative disorders from immunocompromised hosts, immunophenotypic studies failed to detect late EBV replicative antigens. The aim of this study was to investigate the relationship of EBV latent gene expression in B cell PTLD to morphology, clonality, and immunophenotype, and to examine the replicative state of EBV in malignant cells. For this purpose, 9 cases of EBV-related B cell PTLD were analyzed. Immunoglobulin gene rearrangements were detected by Southern blot analysis. The presence of EBV was assessed by Southern blot and by in situ hybridization. B cell differentiation antigens, adhesion and activation molecules, and EBV latent and replicative gene expression were studied using immunohistochemistry techniques. We demonstrated that EBV-related B cell PTLD exhibited varying patterns of latent viral gene expression. Higher levels of adhesion molecules were detected in latent membrane protein 1 (LMP1) or LMP1 plus EBV nuclear antigen 2 (EBNA2)-positive tumors than in LMP1 and EBNA2-negative tumors. In contrast, there was no relationship between CD21 and CD23 expression and latent EBV phenotype. Activation of the EBV replicative cycle was highlighted by BamHI Z left frame 1 expression in 5 of 9 cases. Less frequent expression of late viral proteins suggested that the initiation of the EBV lytic cycle might not always lead to virions production.

Adult↗