Leukocyte migration inhibition studies with Epstein-Barr virus (EBV) determined nuclear antigen (EBNA) in relation to the EBV-carrier status of the donor

Epstein-Barr virus (EBV) antigen-specific leukocyte migration inhibition in infectious mononucleosis. II. Kinetics of sensitization against five EBV-encoded nuclear proteins and the latent membrane protein

The T cell-mediated immune response of infectious mononucleosis (IM) patients to five Epstein-Barr virus (EBV)-determined nuclear antigens, EBNAs, and to the membrane antigen associated with growth-transformed cells (latent membrane protein, LMP) was measured by the leukocyte migration inhibition (LMI) assay. Two different antigen sources were used: extracts from cells that only expressed EBNA-1, EBNA-2, or LMP after transfection with the corresponding EBV-DNA fragment, and synthetic peptides deduced from the corresponding genes. Patients in the acute phase of the disease failed to respond to EBNA-1, -5, -6, and LMP, but became responsive during convalescence. The majority of the patients responded to EBNA-2 and/or EBNA-3 in the acute phase (9/15 and 12/15, respectively). The response to EBNA-2 and/or EBNA-3 in the acute phase (9/15 and 12/15, respectively). The response to EBNA-3 disappeared more often in convalescence than the response to EBNA-2: 6 of 15 patients were negative to EBNA-2 and 12 of 15 to EBNA-3 during recovery. In addition to its value in the assessment of host sensitization to virus EBV antigens, these studies and the derived hypotheses also provide certain predictions about the predominant antigen expression in the EBV-infected host under normal and pathological conditions that can be subjected to direct experimental tests.

Antibodies in human sera against the Epstein-Barr virus encoded latent membrane protein (LMP)

Antibodies reactive with the Epstein-Barr (EBV)-encoded latent membrane protein, LMP, were detected in human sera. Membrane fractions of the EBV-carrying Raji cells and a fusion protein (LMFP), that represents the carboxy part of LMP, were used as antigens. These were assayed by the reduction of the leukocyte migration inhibition (LMI) reaction. Reactivity with LMFP was detected in 10 of 14 sera from patients with Burkitt's lymphoma (BL) and in 3 of 23 sera from healthy EBV-seropositive individuals. The antibody levels were higher in the BL sera. Since the tumor cells do not express LMP, this may be due to the high virus load in the patients.

Cellular and humoral immune responses to synthetic peptides deduced from the amino-acid sequences of Epstein-Barr virus-encoded proteins in EBV-transformed cells

Ten synthetic peptides containing 18-22 residues deduced from the amino-acid sequences of the EBV-encoded latent-infection-associated membrane protein (LMP) and the 2 principal nuclear antigens, EBNA-1 and EBNA-2, were tested for their ability to induce lymphokine release from sensitized T-cells of EBV-seropositive donors, as measured by the leukocyte migration inhibition assay (LMI). Only one of the 10 free peptides induced EBV-specific LMI. After Sepharose-coupling, 4 additional peptides were regularly active. In parallel, the sera of the same and other donors were screened for synthetic peptide-binding antibodies, as measured by an ELISA assay. Antibodies to 9 of the 10 peptides were detected in 25-80% of EBV-antibody-positive, but not in EBV-antibody-negative sera. A comparison of the two responses indicates that the humoral immune system tends to react with more epitopes on a given protein than the cellular immune system. Furthermore, the antibody reactivity pattern to different epitopes is more variable from individual to individual than the T-cell response. Also, the epitopes detected by antibodies and sensitized T-cells are often not identical.

Stable transfection of a human lymphoma line by sub-genomic fragments of Epstein-Barr virus DNA to measure humoral and cellular immunity to the corresponding proteins

An Epstein-Barr virus (EBV)-negative human lymphoid B-cell line, DG75, was stably transfected with recombinant selection vectors that carry a subfragment of the BamHI WYH region (nucleotides 44664 to 50628), the BamHI K fragment, or a subfragment of the EcoRI D region (nucleotides 166614 to 170149) of B95-8 EBV DNA. These fragments contain the coding exons for the EBV-determined nuclear antigens EBNA2 and EBNA1, and the membrane antigen LMP, respectively. Antigen expression of the cells was detected by immunofluorescence. EBNA2 was expressed in 80-100% of the transfected cells, in contrast to EBNA1 which was expressed in only 25%, and LMP in only about 5% of the cells. Humoral antibody responses were measured by immunofluorescence and compared to cellular immunity as determined by the leukocyte migration inhibition (LMI) technique. Extracts from transfected cell lines expressing EBNA1, EBNA2 or LMP elicited an LMI response with cells from healthy EBV-seropositive individuals whereas the extract from the parental DG75 cell line did not. The results demonstrate the value of stably transfected cell lines expressing a defined EBV antigen for the monospecific analysis of host responses to the EBV-encoded antigen complex in growth-transformed cells.

Characterization of EBV-carrying B-cell populations in healthy seropositive individuals with regard to density, release of transforming virus and spontaneous outgrowth

Peripheral or tonsil lymphocyte populations of EBV-seropositive donors give rise to EBV-carrying LCLs upon in vitro explantation. Such lines can arise either by a 2-step mechanism, namely release of virus from some of the explanted cells followed by infection of previously uninfected B cells, or by direct outgrowth of virus-harboring B cells (Rickinson et al., 1974; Dalens et al., 1975; Hinuma and Katsuki 1978; Katsuki et al., 1979). We observed that cells responsible for both the 2-step mechanism and for direct outgrowth are found in the purified B-cell compartment. Virus release was more frequent than direct outgrowth. The majority of virus-releasing cells were found in the low-density fraction that contains large, activated B blasts. Cells that were capable of spontaneous outgrowth in the presence of the viral inhibitor PFA and of virus-neutralizing antibody gave rise to cell lines that carried the sex chromosome marker of the original donor, rather than that of admixed cord blood lymphocyte of the opposite sex. Such cells were found in both the low- and the high-density fractions. The majority of the EBV-carrying B cells in vivo are thus low-density blasts. Rare small B cells of high density harboring EBV were capable of spontaneous outgrowth. This may be indicative of a host control mechanism that is removed upon cultivation in vitro.

Epstein-Barr virus (EBV) antigen-specific leukocyte migration inhibition (LMI) in infectious mononucleosis (IM). I. Kinetics and response to a membrane protein on EBV-transformed cells

Cell-mediated immune response of mononucleosis (IM) patients to Epstein-Barr virus (EBV)-determined antigens was measured by the leukocyte migration inhibition (LMI) assay. Patients in the acute phase of the disease failed to respond to partially purified nuclear antigen, EBNA, or to cell extracts that contained EBNA as the predominant EBV antigen. They showed a strong specific response to cell extracts enriched in early antigen (EA) and virus capsid antigen (VCA). The LMI response to EBNA appeared in convalescence in parallel with EBNA-specific antibodies, slightly later in children than in adults. Membrane fractions of EBV-carrying, virus nonproducer Raji cells induced an EBV-specific LMI at approximately the same time. A bacterial fusion protein containing the hydrophilic part of the virus-coded membrane antigen of latently EBV-infected cells also induced an EBV-specific response that parallelled the LMI reaction elicited by the Raji membrane fraction. This is in line with our previous finding (D. Sulitzeanu et al., J. Virol. 58, 230, 1986) that this fusion protein shares an epitope with Raji cell membranes.

Leukocyte migration inhibition demonstrates a human T-cell response to a membrane protein expressed in latent Epstein-Barr virus infection

Leukocyte migration inhibition tests show that lymphocytes of Epstein-Barr virus-seropositive individuals recognize a Raji cell membrane antigen and a membrane protein encoded by Epstein-Barr virus in latently infected cells. Antiserum against the latter blocks the leukocyte migration inhibition triggered by both preparations, suggesting that the two antigens are associated with the same protein complex.

Leukocyte migration inhibitory factor production by activated lymphocytes representing immunological memory or virus-receptor interaction: response of T cell subsets to Epstein-Barr virus nuclear antigen, response of B cells to UV inactivated Epstein-Barr virus

Both T and B lymphocytes are known to produce leukocyte migration inhibitory factor (LIF) after appropriate activation. We showed that EBV nuclear antigen (EBNA) triggered T cells for LIF production in an immunologically specific way: only T cells of seropositive individuals responded. Both Fc receptor positive and negative T cells produced LIF, and the presence of macrophages was necessary. The virus itself activated B cells independently of the serological status of the donors, thus the function was not based on immunological memory. This phenomenon was independent of the transforming capacity of the virus, because UV-inactivated virus also elicited LIF production by B lymphocytes. This triggering seems to be the consequence of the virus-receptor interaction on the cell surface.

Epstein-Barr virus (EBV)-specific cell-mediated and humoral immune responses in ataxia-telangectasia patients

As a part of studies on cell-mediated immune (CMI) responses of immunocompromised, Epstein-Barr virus (EBV)-infected patients who can or cannot restrict the proliferation of EBV-transformed B cells, we have studied 16 Turkish patients with ataxia-telangectasia (AT). Fifteen were EBV seropositive; one was seronegative. Among the seropositives, eight had no or only low anti-EBV-determined nuclear antigen (EBNA) antibody titers, while seven had normal anti-EBNA levels. EBV-seropositive and -seronegative healthy Turkish children were used as controls. We have particularly asked the question whether low EBNA antibody titers can be correlated with the level of EBV-specific and -nonspecific cell-mediated immunity. Non-EBV-specific tests included cell count, phenotypical characterization with monoclonal antibodies, assessment of natural killer (NK)-cell activity, and ability to suppress mitogen-induced immunoglobulin production. Two EBV-specific CMI tests were used: outgrowth inhibition (OI) and leukocyte migration inhibition (LMI). The majority of the patients of the low-EBNA antibody group was IgA deficient and had high levels of alpha-fetoprotein (a-FP). Cells reacting with OKT8 monoclonal antibody predominated in both AT patient groups. In contrast, the suppressor activity was present in only a few patients and NK and interferon-activated killing (IAK) activities were normal. EBV-specific cell-mediated responses were defective in seven of eight patients in the low-anti-EBNA group and five of seven patients in the group with normal anti-EBNA titers. It is concluded that AT patients are often defective in their EBV-specific cell-mediated immune responses and with regard to their EBNA antibody levels. These defects are associated with a predominance of T cells reacting with OKT8 monoclonal antibody.

Detection of an Epstein-Barr virus-associated membrane antigen in Epstein-Barr virus-transformed nonproducer cells by leukocyte migration inhibition and blocking antibody

Soluble membrane fractions derived from Raji cells trigger lymphocytes of Epstein-Barr virus (EBV)-seropositive, but not EBV-seronegative, individuals to release a lymphokine that inhibits leukocyte migration. The reaction can be blocked by the sera of patients with EBV-DNA-carrying tumors, Burkitt lymphoma, or nasopharyngeal carcinoma. Absorption of these sera with EBV-positive, but not EBV-negative, cells abrogates their blocking activity. These findings suggest that the antigen responsible for the leukocyte migration inhibition reaction is an EBV-encoded or an EBV-induced membrane component. The antigen is not identical with EBV-associated nuclear antigen or any other known antibody-detected EBV antigen.

Virologic, immunologic, and clinical observations on a patient during the incubation, acute, and convalescent phases of infectious mononucleosis

One patient with infectious mononucleosis (IM) was studied from the probable time of Epstein-Barr virus (EBV) infection (38 days before the onset of clinically overt disease), during the incubation and acute phases, until 6 months after clinical remission. Analysis of spontaneous outgrowth of EBV-carrying lymphoblastoid cells, by limiting dilution on feeder layer cultures, showed that virus containing B lymphocytes are already present early during the incubation period. Also low interferon serum levels were detected early after infection, and only before the onset of clinical disease. All other studied clinical laboratory and virus-associated variables were within normal range during the incubation phase, but changed to a pattern characteristic of IM in parallel to the clinical symptoms. During the acute disease EBV-associated nuclear antigen (EBNA)-positive cells could be directly detected among the lymphocytes, and antibodies to EBV antigens appeared. Lymphocytes stained by monoclonal antibodies, detecting Ia-like determinants (activated cells) and suppressor cells, increased dramatically, in parallel to a strong increase of functional suppressor cell activity, measured by inhibition of blastogenesis and PWM-induced immunoglobulin production. During the acute phase there was also a decrease of spontaneous cytotoxicity against the NK-sensitive cell line K562, while cytotoxicity (spontaneous) against an autologous EBV-positive lymphoblastoid cell line (LCL) was detected only during this phase. These reactions correlated to the presence of blasts, and the autologous reaction was exerted mainly by Fc-receptor-negative cells. Lymphokine production in response to EBV antigens was also initiated during the acute phase. During the convalescence period the serological and cellular immune parameters adjusted to the pattern of a normal EBV-seropositive person.

EGNA-specific LIF production of human lymphocyte subsets

Using the indirect leukocyte migration inhibition technique T cells have been identified as being responsible for Epstein-Barr virus nuclear antigen-induced specific leukocyte migration inhibitory factor production. The response was dependent on the presence of macrophages or their product, T-lymphocyte activating factor.

Epstein-Barr virus-associated antibody pattern in untreated non-Hodgkin lymphoma patients. Relationship to clinical variables and lymphocyte functions

Sera from 296 unselected and untreated patients with non-Hodgkin lymphoma (NHL) classified according to the Rappaport and the Kiel systems were analyzed for antibodies to Epstein-Barr virus (EBV). The aim of the study was to determine whether antibody spectra and titers to EBV-coded antigens correlated to clinical and immunological variables and whether the titers were of any prognostic significance. Increased antibody titers to EB viral capsid antigen (VCA) and slightly raised titers to early antigens (EA) of the diffuse (D) and restricted (R) types were noted frequently. Anti-VCA antibody titers correlated to clinical stage and age of the patients but not to histological subgroups according to the Rappaport or the Kiel classification systems. However, anti-VCA titers greater than or equal to 1:2560 were seen only in diffuse lymphomas according to the Rappaport and in non-follicle cell-derived lymphomas according to the Kiel classifications. Patients with complement-receptor-positive diffuse lymphomas had higher anti-VCA titers than complement-receptor-positive nodular cases. Anti-VCA titers also correlated positively to serum IgG levels (p less than 0.01). Total number of lymphocytes separated from peripheral blood and mitogen induced (ConA, PWM) DNA synthesis were recorded before treatment in 56 of the patients. The patients exhibited a significant lymphocytopenia as well as a significantly reduced lymphocyte response to mitogens (p less than 0.001) compared to healthy controls. Elevated anti-VCA titers and anti-EA titers correlated to a good mitogen-induced lymphocyte response (p less than 0.05). Only anti-D 1:40 at diagnosis predicted a poor prognosis.

A prospective study on infectious mononucleosis in childhood--symptoms, serology, Epstein-Barr-Virus specific leukocyte migration inhibition

The clinical course, serological changes and the development of the specific cell-mediated immune response to Epstein-Barr-Virus (EBV), measured in terms of leukocyte migration inhibition, were followed in 40 children suffering from an EBV infection. The patients were followed for between six and 24 months. Although the majority of the children were under six years of age, they presented a typical clinical course; heterophil antibodies could only be demonstrated in 60% of the cases. Anti-VAC-IgM and IgG antibodies were found in all patients during the acute phase, but no anti-EBNA could be demonstrated. In children under three years of age, no antibodies against the D component of the early antigen were found; this antibody was found in 50% of the adolescents. An antibody against the R component of the early antigen could be demonstrated in 73% of the children five to six months after the onset of the disease. Specific leukocyte migration inhibition was present only during convalescence or later. A relationship between the appearance of anti-EBNA and the development of specific leukocyte migration inhibition has been established.

Migration inhibition caused by EBV-specific 48K subcomponent of EBNA and the associated 53K cellular protein

Leukocytes from EBV-seropositive but not seronegative healthy donors responded with significant migration inhibition to the 48K subcomponent of the Epstein-Barr virus determined nuclear antigen (EBNA), known to carry the virally determined antigenic specificity. A concentration of 10 micrograms/ml was still effective while 5 micrograms/ml had no detectable effect. EBNA-associated cellular 53K protein had no effect by itself, but it potentiated the effect of 48K, even if the latter was added at the subliminal concentration of 5 micrograms/ml. The related 53K protein, isolated from EBV-negative human lymphoma cells, was also effective, whereas the corresponding murine-tumor-associated 53K had no potentiating effect. Immunization of mice with an extract of DNA-binding proteins from EBV-carrying Raji cells, known to contain both 48K and 53K, induced a significant macrophage migration inhibition response, to both human 48K and 53K. Murine 53K was ineffective, however. Human but not murine 53K increased the migration inhibitory activity of subliminal concentrations of 48K in the murine macrophage system as well. These findings suggest that human but not murine 53K may reconstitute with 48K (EBNA) to form a highly immunogenic complex.

Use of cryopreserved lymphocytes for the indirect leukocyte migration inhibition assay

Production of leukocyte migration inhibitory factor (LIF) by fresh and cryopreserved lymphocytes from the same donors was detected by indirect leukocyte migration inhibition (LMI) assay. The same results were obtained when fresh and frozen lymphocytes were tested in parallel. This indicates that cryopreservation does not impair the ability of lymphocytes to produce LIF.