Aggrey Nyongo

Burkitt’s lymphoma: new insights into molecular pathogenesis

The World Health Organisation classification reports three subcategories of Burkitt’s lymphoma (BL)—endemic, non-endemic, and immunodeficiency associated—proposed to reflect the major clinical and genetic subtypes of this disease. These different types of BL have been reviewed and studied by immunohistochemistry and molecular methods. The results point out the heterogeneity of BL and suggest that AIDS related BL may have a different pathogenesis from that of classic BL.

Genetic Alterations of the Retinoblastoma-Related Gene RB2/p130 Identify Different Pathogenetic Mechanisms in and among Burkitt’s Lymphoma Subtypes

Alterations of cell cycle-associated genes probably contribute to the pathogenesis of Burkitts Lymphoma (BL), in addition to c-myc translocation. Mutations disrupting the nuclear localization signal of the retinoblastoma-related gene RB2/p130 have been documented recently in BL cell lines and primary tumors. Given the importance of the RB2/p130 gene in controlling cell growth, mutations of this gene may result in uncontrolled cell proliferation. We tested the expression and genomic organization of the RB2/p130 gene in relation to the proliferative features of a series of BL samples collected from the endemic and sporadic regions, regardless of whether the samples were acquired immune deficiency syndrome (AIDS)-related. The expression of the Rb2/p130, p107, and cell proliferation-related proteins (cyclin A and B) was determined by immunohistochemistry. The structures of exons 19 through 22 of the RB2/p130 gene, encoding for the B domain and C terminus, were analyzed by polymerase chain reaction (PCR) analysis and single-strand conformation polymorphism (SSCP) technique. The direct PCR products were sequenced to identify the actual mutations. Our results suggest that BL is composed of a mixture of molecular types with distinct genetic and phenotypic patterns, probably resulting from different pathogenetic mechanisms. In endemic BL, the RB2/p130 gene is mutated in most of the cases, and the protein is restricted to the cytoplasm. In AIDS-related BL, high levels of nuclear expression of the wild-type pRb2/p130, p107, and cell proliferation-related proteins were detected. This finding is in line with the molecular mechanisms observed in virus-linked oncogenesis. Sporadic BLs were mainly characterized by the low nuclear values of the wild-type pRb2/p130 and, conversely, the high values of p107. The increased cell proliferation due to different alterations of cell growth control by Rb-related proteins may be the first step in lymphomagenesis, during which additional genetic changes, including missense mutations of c-myc, may subsequently occur.

Neoplastic cells of Hodgkin's disease show differences in EBV expression between Kenya and Italy

The Epstein‐Barr Virus (EBV) has been implicated in the pathogenesis of Hodgkins disease (HD). However, the association of EBV with this disease varies greatly from series to series and from country to country. Epidemiological studies have shown differences in HD occurring in different parts of the world. In particular, it has been reported that HD in developing countries differs from HD in Western countries in terms of epidemiological, pathological and clinical characteristics. These discrepancies among populations suggest an interaction with environmental factors and a direct role of different etiological agents. At present, there are no data on the frequency of association of EBV with HD in equatorial Africa. In this study, a large series of HD cases have been collected at the University of Nairobi, Kenya, and at the Universities of Bologna and Siena, Italy. The cases have been reviewed and classified according to the REAL Classification and the presence of EBV has been assessed by in situ hybridization (ISH). A statistical difference in EBV expression was found between HD from Kenya and HD from Italy. EBV‐positive neoplastic cells were detected in 92% of Kenyan cases, whereas only 48% of Italian cases showed EBER1/2 positivity in the neoplastic cells. Our results suggest that, in Kenya, EBV plays a more direct role in the pathogenesis of HD, as it does for endemic Burkitt lymphoma.

HIV-associated malignant lymphomas in Kenya (Equatorial Africa)☆

The clinical and pathological features of acquired immune deficiency syndrome (AIDS)-related lymphomas, including their relationship with other viruses, such as Epstein-Barr virus (EBV) and human herpes virus-8 (HHV8), have been the subject of several studies from North America and Europe. No consistent data have been reported in Africa, where AIDS runs an epidemiological and clinical course different from that observed in Western countries. We retrospectively evaluated the presence of human immunodeficiency virus (HIV), HHV8, and EBV in 146 cases of malignant lymphomas collected in Kenya (Equatorial Africa), with the use of polymerase chain reaction (PCR) and in situ hybridization (ISH). The PCR technique confirmed HIV infection in 16 HIV-seropositive subjects (11%) and showed the presence of HIV sequences in five additional cases (3%) in which the occurrence of lymphoma was the only clinical manifestation. Our findings suggest that AIDS-related lymphomas are not pathogenetically homogenous, and different mechanisms may contribute to lymphomagenesis in these severely immunocompromised patients. In our series, no association of Hodgkins disease (HD) with HIV infection could be shown. Among non-HIV-related lymphomas, EBV was present in 94% of Burkitt lymphoma (BL) occurring in patients younger than 15 years of age, in 87% of HD independently of age, sex, and histological types, in 60% of anaplastic large cell lymphoma (ALCL), and to a lesser extent (13%) in large B-cell lymphoma (LBCL) cases. Only one tumor, a case of HD, showed HHV8 by PCR.

RISK-FACTORS FOR MOTHER-TO-CHILD TRANSMISSION OF HUMAN IMMUNODEFICIENCY VIRUS-1 INFECTION.

Abstract OBJECTIVE: Our aim was to examine maternal, obstetric, and infant characteristics of mother-to-child transmission of human immunodeficiency virus-1 in Nairobi, Kenya. STUDY DESIGN: Proviral human immunodeficiency virus-1 was detected by polymerase chain reaction in peripheral blood samp0les taken between 6 weeks and 3 months of age from 107 children born to human immunodeficiency virus-1 seropositive women. The association of maternal, infant, and obstetric variables with human immunodeficiency virus-1 transmission was examined. RESULTS: The mother-to-child transmission rate was 31% (95% confidence interval 21.6 to 40.2) as defined by the presence of proviral human immunodeficiency virus-1 in the infant. Variables associated with transmission in a univariate analysis included placental inflammation ( 7 12 in the transmitting group as compared with 2 22 in nontransmitters, p = 0.006), low maternal CD4 and high CD8 percentages (21% and 52%, respectively, in transmitting mothers and 32% and 40% in nontransmitting mothers; p = 0.001), and the gender of the neonates ( 20 29 infected neonates were female as compared with 26 65 noninfected children, p = 0.02). Sexually transmitted diseases were found more often in transmitting mothers but the differences were not significant. Birth weight and gestational age were not related to vertical transmission of human immunodeficiency virus-1. CONCLUSION: Risk factors for mother-to-child transmission of human immunodeficiency virus-1 included chorioamnionitis, an impaired maternal immune status, and female gender.

Cellular kinetic and phenotypic heterogeneity in and among Burkitt's and Burkitt-like lymphomas.

This study asks whether the known genotypic heterogeneity within and between endemic or sporadic Burkitts lymphomas (eBLs and sBLs, n=10 each), and Burkitt‐like lymphomas (BLLs, n‐12), is reflected in divergent cytokinetics and related immunophenotypes. There was strong evidence that eBL and BLL grow markedly faster than sBL, as shown by differences in mitotic and apoptotic indices. Furthermore, in BLL, the median percentage of neoplastic cells immunoreactive for the bcl‐2 protein was much higher than that observed in eBL and sBL. The reverse was true for the median fraction of cells containing c‐myc protein. In eBL and sBL, the median fraction of bcl‐6 protein‐positive cells reached values above 50 per cent, while cells of 8/12 BLLs did not contain detectable amounts of this protein. This observation indicates that in this respect, eBL and sBL resemble normal germinal centres of lymphatic tissue much more than do BLL. Evidence for infection of neoplastic cells by the Epstein‐Barr virus (EBV) was observed in 9/10 cases of eBL and in 3/10 of sBL, but not in BLL. EBV‐positive lymphomas were associated with distinctly lower apoptotic indices and smaller median percentages of bcl‐6‐positive cells than EBV‐negative tumours.

Pyramidal neurones in pathological human motor cortex express nitric oxide synthase

The enzyme nicotinamide adenine dinucleotide phosphate diaphorase (NADPH diaphorase) is widely used as a sensitive marker for indicating the presence of nitric oxide synthase in neurones. Pyramidal neurones in the healthy neocortex do not contain detectable levels of nitric oxide synthase. However, in the precentral gyrus of brains showing pathological damage, a high proportion of Betz cells (11-50%) and some smaller pyramidal neurones contained low to moderate levels of NADPH diaphorase. They were located in layers V and VI and were present in a newborn baby, older children and elderly adults. Thus, under pathological conditions, some pyramidal neurones are apparently capable of synthesising nitric oxide and this may have a neuroprotective function.

Fatal Cytomegalovirus Infection in a Patient without Evidence of Prior Immunodeficiency

Cytomegalovirus (CMV) infection is a common cause of death among immunocompromised individuals, whereas among immunocompetent hosts, CMV infections are generally subclinical. We describe a case of CMV infection with a rapidly fatal outcome in a patient for whom there was no evidence of prior immunodeficiency. A 62-year-old, previously healthy African man was admitted to the Nairobi Hospital (Nairobi, Kenya) on 1 June 1996 for evaluation of fatigue, fever, cough, and dyspnea of 4 weeks’ duration. Physical examination revealed a very ill-appearing patient who was dyspneic and febrile (temperature, 38.57C). Bilateral basal crepitus was elicited on auscultation, and hepatosplenomegaly was detected on abdominal palpation; there was no evidence of superFigure 1. Photomicrograph of lung sections at autopsy from a ficial lymphadenopathy. The patient’s blood pressure was 100/60 62-year-old male with cytomegalovirus infection showing enlarged mm Hg, his heart rate was 110, and his respirations were 28/min. alveolar epithelial cells containing characteristic ‘‘owl’s eye’’ cytomegalovirus inclusions at arrow (stain, hemotoxylin-eosin; original A chest radiograph showed an interstitial pulmonary process. magnification, 1375). Laboratory hematologic evaluation revealed anemia (hemoglobin level, 8.2 g/dL; RBC count, 3.1/mm), leukopenia (WBC count, 2.3/mm with 32% neutrophils, 62% lymphocytes, and 6% monocytes), a low platelet count (100,000/mm), and hypoproteinemia cyte proliferation. There were numerous CMV inclusions in the alveolar epithelial cells (figure 1). (total protein level, 39.5 g/L; normal range, 60–80 g/L). Parameters for liver and renal function were within normal limits. EvaluaGross examination of the spleen at autopsy (weight, 1,220 g) showed focal areas of cortical infarction. Histological evaluation tion of a bone marrow biopsy specimen showed hyperplastic hemopoiesis with abnormal erythropoiesis, granulopoiesis with a left revealed fibrosis and lymphocyte depletion of the white pulp, macrophage hyperplasia with hemophagocytosis, and foci of extramedshift (without excess blast forms), and rare micromegakaryocytes with nacked nuclei. The patient developed diarrhea, and evaluation ullary hemopoiesis. The hilar as well as mediastinal and paraortic lymph nodes appeared atrophic with severe lymphocyte depletion, of a stool specimen (described as yellow and loose) showed many RBCs, WBCs, and yeasts, but no ova, cysts, or trophozoites were fibrosis, vascular proliferation, and ‘‘burnt out’’ germinal centers. CMV inclusions were evident in some cells. detected. Culture of the specimen was negative for bacteria. Broadspectrum antibiotic therapy was administered. Immunophenotyping revealed a relative reduction of CD4/ T lymphocytes with a CD4/CD8 ratio of 0.5. Examination of the Serologies for IgG to CMV were positive (11 au/mL), but those for IgM to CMV were negative, and no specific treatment was colonic mucosa showed multiple ulcerations, and characteristic CMV inclusions were detected on histological examination. Careinitiated for CMV. Serologies for antibodies to HIV-1 and HIV2 were negative, as assessed by use of ELISA. ful examination of the remaining viscera showed no relevant pathological findings. The patient’s condition deteriorated suddenly; he developed nausea and vomiting. Laboratory studies revealed the following A nested PCR that used universal lentivirus primers was performed on DNA extracted from paraffin-embedded lymph node, values: RBCs, 3.0/mm; WBCs, 1,300/mm with severe lymphocytopenia, 350/mm; and platelet count, 80,000/mm. His respiratory spleen, and lung specimens, according to previously published protocols [1]. There was no evidence of HIV-1, HIV-2, or lentivisymptoms persisted, as did the diarrhea. The patient became confused, having only intervals of lucidity, and his condition continued rus-related DNA on repeated assays. CMV infection is a common cause of death among immunocomto deteriorate until he died 10 days after his hospital admission. At autopsy, the right and left lungs weighed 1,339 g and 1,117 promised individuals, whereas among immunocompetent hosts CMV infections are generally subclinical. A mild and self-limiting g, respectively. There were fibrinous adhesions on the pleural surfaces. Histological evaluation of lung sections showed bronchiomononucleosis-like syndrome occurs in Ç10% of adults, and severe CMV disease in immunocompetent patients is rare [2–5]. litis obliterans and marked interstitial fibrosis with type II pneumoThe possibility that a subtle immunologic defect may be recognized in such cases in the future cannot be excluded, but currently there is no evidence to validate this hypothesis. We described CMV infection with rapid fatal outcome in a Reprints or correspondence: Dr. Lorenzo Leoncini, Institute of Pathological patient for whom there was no evidence of prior immunodefiAnatomy and Histology, Policlinico Le Scotte, Via delle Scotte, 6, 53100 ciency. A serology for IgM to CMV was negative in our case, as is Siena, Italy. usually observed in acute infections among immunocompromised Clinical Infectious Diseases 1998;27:659–60 patients or in reactivation of latent infections [6]. In addition, q 1998 by the Infectious Diseases Society of America. All rights reserved. 1058–4838/98/2703–0045

Routine assessment of hormonal receptor and her-2/neu status underscores the need for more therapeutic targets in Kenyan women with breast cancer

03.00 results of histology and immunophenotyping of lymphoid tissue