Epstein-Barr virus (EBV)-associated antibody patterns in malignant lymphoma and leukemia. II. Chronic lymphocytic leukemia and lymphocytic lymphoma

Clonality and methylation status of the Epstein-Barr virus (EBV) genomes in in vivo-infected EBV-carrying chronic lymphocytic leukemia (CLL) cell lines

Directly growing Epstein-Barr virus (EBV)-carrying cell lines were established from a chronic lymphocytic leukemia (CLL) patient (PG) on repeated occasions. The lines carried the same ring chromosome 15 as the leukemia cells in vivo and were similarly trisomic for chromosome 12. They all showed the same JH rearrangement, indicating that they had arisen from the same B-cell progenitor. They also had the same single EBV-terminal repeat (TR), indicating that they had been generated by a single EBV infection event. It may be surmised that a single CLL cell had been infected by EBV in vivo and established itself subsequently as a subclone within the CLL population. This subpopulation persists in vivo but does not appear to expand with time. After explantation, it transforms into lymphoblastoid cells and proliferates selectively as immortalized lines. The leukemia-representative CLL lines were phenotypically indistinguishable from the B95-8 virus-transformed normal diploid cells of the patient, established in parallel by in vitro infection. They grew as typical LCL clusters and expressed the same B-cell activation markers. The methylation status of EBV-DNA was different in the CLL lines and the B95-8-virus-transformed LCLs. When Hpall- and Mspl- digested DNA was probed with BamHI C, E, H and W fragments, the CLL lines showed a mixture of methylated and unmethylated restriction fragments as in certain EBV-carrying Burkitt lymphoma (BL) lines. In contrast, the EBV-DNA of B95-8 virus-transformed normal diploid cells was completely unmethylated, as in other LCLs.

Direct outgrowth of in vivo Epstein-Barr virus (EBV)-infected chronic lymphocytic leukemia (CLL) cells into permanent lines

In the course of our efforts to characterize the EBV-carrying cells that are responsible for direct growth or the 2-step mechanism, based on virus release from the explanted cells and subsequent transformation of previously uninfected cells, we have encountered an unusual CLL patient who carried a small subpopulation of in vivo EBV-infected leukemia cells. These were predominantly present in the low-density fraction and grew into EBV-carrying lines upon explantation after a relatively short latency period, 3-4 weeks. Cytogenetic examination conclusively proved the leukemic origin of the established CLL lines. They carry a ring chromosome 15 and are trisomic for chromosome 12. The same changes are also found in the majority of the peripheral blood lymphocyte population. Taken together, our results suggest that the EBV-genome and the cytogenetic changes may have contributed to the immortalization of the CLL cells in a complementary or synergistic fashion.

Possible aetiological factors in leukaemias in Africa

The hypothesis that the true incidence of c-ALL is relatively uniform throughout the world is not supported by experience in tropical Africa, where ALL is uncommon under five years of age. A high rate of spontaneous somatic mutation in pre-B cells may initiate the development of c-ALL, but its progress could be determined by (i) a leukaemogenic agent causing a second genetic event, (ii) the effects of intense antigenic barrage, either stimulating or suppressing pre-B-cell mitosis, or (iii) genetic determinants. Epidemiological patterns in populations of low, intermediate and high socio-economic status may be classified I-III with increasing incidence of diagnosed T-ALL in children over five years and c-ALL in younger children, and subclassified A and B with decreasing incidence of BL. There may be two forms of AML, one similar to that seen in industrialized countries, the other occurring at high prevalence in African children of low socio-economic status, often presenting with chloroma, and perhaps associated with immune suppression secondary to malnutrition, malaria and other intercurrent infections. Uncontrolled exposure to petroleum and other chemicals, and the use of alkylating agents in treatment of neoplasms in young patients could emerge as important causes of ANLL in Africa. There are two varieties of CLL also, one similar to that seen in the western world, the other prevalent in adults below 45 years of age, especially women: transmission of a leukaemogenic agent is postulated, to which women are more susceptible due to immunosuppression during normal pregnancy. The human population and some subhuman primates of subSaharan Africa are the largest reservoir of HTLV-1, which shows association with B-CLL over 50 years of age and ATL.

Increased incidence of IgA antibodies to the Epstein-Barr virus-associated viral capsid antigen and early antigens in patients with chronic lymphocytic leukemia

Antibody titers to Epstein-Barr virus (EBV)-associated early antigens (EA) and the viral capsid antigen (VCA) were determined by ELISA on 263 sera obtained from healthy donors, patients with Hodgkin's disease (HD), non-Hodgkin lymphomas (NHL), infectious mononucleosis (IM), Burkitt's lymphoma (BL), and nasopharyngeal carcinoma (NPC). As expected, most lymphoma patients showed markedly elevated anti-VCA IgG and anti-EA IgG antibody titers. Only one patient in the NHL group (n = 56) consisting of patients with lymphomas other than chronic lymphocytic leukemia (CLL) and hairy-cell leukemia (HCL), and 3 patients with HCL (n = 19) had high antibody titers of the IgA class to VCA and EA. Seventeen out of 48 patients (36%) with CLL had high IgA anti-VCA titers and 10 of these sera (21%) also contained IgA anti-EA. The geometric mean titer (GMT) of IgA anti-VCA was 2,510, the GMT of IgA anti-EA was 780. These antibody titers were about 10 times lower than the corresponding GMT of the NPC patients investigated in this study. The elevated IgG and IgA antibody titers to VCA and EA in CLL and HCL patients seem to reflect an immunodeficiency secondary to the malignant disease leading to reactivation of latent EBV infection. The possibility that at least some of these B-cell lymphomas are associated with EBV cannot be excluded.

An immunoperoxidase assay for the detection of specific IgA antibody in Epstein-Barr virus infections

A technique using indirect immunoperoxidase antibody was developed for the detection of specific serum IgA antibody to Epstein-Barr virus capsid antigen and early antigen. The IgA technique was compared with an immunofluorescence antibody method. Epstein-Barr virus IgA antibody against viral capsid antigen was detected in all nine patients with Epstein-Barr virus associated undifferentiated nasopharyngeal carcinoma, in 13 (72.2%) of 18 patients with infectious mononucleosis, in 21 (28.3%) of 74 patients with acute lymphoblastic leukaemia, and in six (20%) of 30 patients who had recently had kidney transplants. Epstein-Barr virus IgA antibody against viral capsid antigen was also detected in four (10%) of 40 healthy subjects, but it was not found in any of 20 cord blood samples. Epstein-Barr virus IgA antibody to early antigen was detected in six (66.6%) patients with nasopharyngeal carcinoma and in two (2.7%) patients with acute lymphoblastic leukaemia. The immunoperoxidase assay for Epstein-Barr virus specific IgA was simple, reliable, and rapid and correlated well (r = 0.94) with the immunofluorescence antibody technique.

Reactivity with patient antibodies of partially purified gp40 antigen from immune complexes in Burkitt's lymphoma and nasopharyngeal carcinoma

A glycoprotein antigen (gp40) was previously identified as a major component of immune complexes isolated from sera of patients with Burkitt's lymphoma (BL) and nasopharyngeal carcinoma (NPC). In the present work gp40 was partially purified from a pool of BL/NPC sera. Sera of patients with BL and NPC as well as sera of patients with other malignant and non-malignant diseases were tested for antibodies against gp40, using a double antibody radioimmunoassay. Practically all normal sera and sera of patients with non-malignant diseases had antibodies capable of binding radioiodinated gp40. In contrast, sera of patients with BL or NPC had very low binding, while sera of patients with other malignant diseases had intermediate binding values. The low binding activity of BL/NPC sera was shown to be due to inhibition by excess gp40 present in such sera. Effusions of patients with breast or ovarian cancer also contained demonstrable amounts of gp40. The origin of gp40 is still unknown.

Detection of the EBV-determined nuclear antigen (EBNA) in Burkitt's lymphoma and nasopharyngeal carcinoma biopsies by the acid fixed nuclear binding (AFNB) technique

Epstein-Barr virus (EBV) carrying biopsies of Burkitt lymphoma (BL) and nasopharyngeal carcinoma (NPC) were used to examine the question whether the EBV-associated nuclear antigen (EBNA) can be demonstrated by the acid fixed nuclear binding (AFNB) technique, developed previously for the demonstration of EBNA in cultured cell lines [11]. Extracts of 5 BL and 5 NPC biopsies gave a brilliant, EBNA specific fluorescence after binding to acid fixed chicken red cells. Similar extracts of 3 other African tumors that are not known to carry the EBV-genome were negative, in spite of the fact that they were derived from EBV-seropositive patients with relatively high anti-EBV (VCA) antibody titers. Crude extraction and DNA-cellulose purification gave equally active extracts, provided that incubation was carried out at 4 degrees C. These results show that the acid fixed nuclear binding technique can be applied to biopsy material. This may be helpful in searching for EBNA carrying cells in heterogeneous normal and tumor tissues in vivo where the direct in situ ACIF staining for EBNA is known to meet great difficulties.

Anti-EBV antibody titers in non-Hodgkin lymphomas

Antibody titers to Epstein-Barr virus (EBV)-related antigens, i.e. viral capsid antigen (VCA), the D and R components of the early antigen (EA) complex and the EBV-associated nuclear antigen (EBNA), were determined in a series of 86 patients with non-Hodgkin lymphomas and in 150 matched control subjects. The lymphoma patients belonged to four histological groups: diffuse, nodular, hyperbasophilic malignant lymphoma (HML) and unclassified. The EBV-related serological data were compared to the incidence of antibodies to other herpes viruses, i.e. cytomegalovirus (CMV), herpes simplex virus (HSV) and varicella zoster virus (VZV), and correlated with immune disorders, which are particularly frequent in the HML type of lymphoma. The results revealed a significantly higher incidence of anti-EA-D titers in lymphoma patients and slight but significant increases in the geometric mean anti-VCA titers in the HML and unclassified group of patients. These elevated anti-EBV titers in patients were not associated with an increase in titres of antibodies to other herpes viruses. They did not correlate with the signs of immune deficiency observed or with the incidence of auto-antibodies.

Burkitt's lymphoma - a human tumor model system for immunological studies

Burkitt's lymphoma occurs mainly in parts of tropical Africa and has attracted the attention of experimental workers due to its epidemiological and clinical features, which indicate a viral etiology and a host immune response to the tumor. As a result of virological studies, Epstein-Barr virus (EBV) DNA has been demonstrated in almost all tested biopsies of African BL. This contrasts to the absence of EBV in all, or almost all, of the non-African Burkitt's lymphoma-like tumors, even though the number of tested tumors in this group is small, and to the lack of EBV in all other types of lymphoma or leukemia. Immunological studies have revealed the presence of antibodies to different EBV-associated antigens in all African patients with Burkitt's lymphoma. However the antibodies are not specific for Burkitt's lymphoma but are found in most adults all over the world, although at lower levels. They cannot therefore serve diagnostic purposes, but they can give prognostic information and occasionally give clues to the mechanisms behind late tumor recurrences, and possibly guide so-called immunotherapy. Burkitt's lymphoma patients contrast to appropriate control groups where some of the persons are anti-EBV seronegative, and this, together with the presence of EBV in Burkitt's lymphoma biopsies and the absence of EBV in other lymphomas, even though the cell type involved may be infectable by EBV in vitro and the tumor may arise in an EBV-carrying person, favors an etiological role in EBV in Burkitt's lymphoma and speaks against the "passenger" hypothesis, according to which EBV is picked up by the Burkitt's lymphoma cell which happens to be particularly suitable for EBV persistence. To explain the geographical distribution, a cofactor, such as certain forms of malaria, has been implied.

Antibodies to Epstein-Barr virus in patients with Hodgkin's disease and leukemia

Sera from 67 Hodgkin's disease patients, 71 leukemia patients, and 186 healthy subjects were tested for antibodies to Epstein-Barr (EB) viral antigens by immunofluorescence methods. In both disease categories, in particular Hodgkin's disease patients, levels of antibodies to the viral capsid antigen (EBV-VCA) and MGT were higher than in the healthy controls. Significantly higher titers were found in Jewish patients of Asian-African origin, as compared to Jews of European origin, with Arab patients as intermediates. The effect of ethnic origin was independant of age and histopathologic type. Sex had no effect on titer. Inconsistent differences in titer were found between age groups in the various ethnic-histopathologic type groups. Some of the leukemia patients had no detectable antibodies to EBV, while all Hodgkin's disease patients showed previous contact with EB virus. Antibodies to the early antigen (EBV-EA) were found in 27% of Hodgkin's and 37% of leukemia patients, and in none of the healthy controls tested.