Analysis of Epstein-Barr virus gene transcription in lymphoma induced by the virus in the cottontop tamarin by construction of a cDNA library with RNA extracted from a tumour biopsy

Inoculation of the cottontop tamarin with Epstein-Barr virus (EBV) gives rise to the development of mono- and/or oligoclonal large cell malignant lymphoma. A cDNA library was generated with the RNA extracted from an EBV-induced tamarin lymphoma biopsy in order to study the transcripts expressed in the tumour tissue. Fifteen EBV-specific cDNA clones were localized in the corresponding viral genomic fragments. Among them, two correspond to the EBNA-2 gene, and two others to the latent membrane protein gene. The majority of the cDNA clones were localized in the BamHI A fragment which has not been associated with latent expression. Furthermore, cDNAs were also found from the BamHI D and I fragments. Sequence analysis of the cDNAs localized in BamHI A showed that they correspond to a rightward transcript in the BALF-3 region, with the one clone that was sequenced containing four exons and three introns. The above results were confirmed by testing three different biopsies with the rapid amplification of cDNA ends-PCR method.

Replication-defective recombinant adenovirus expressing the Epstein-Barr virus (EBV) envelope glycoprotein gp340/220 induces protective immunity against EBV-induced lymphomas in the cottontop tamarin

A replication-defective recombinant adenovirus (Ad) expressing the full length Epstein-Barr virus (EBV) major envelope glycoprotein gp340/220 was tested for its ability to protect against EBV-induced lymphoma in the cottontop tamarin. Antibody responses against Ad capsid proteins and EBV gp340/220 were observed but these antibodies did not neutralize EBV in vitro. However, all immunized animals were protected against challenge following three intramuscular doses of the recombinant Ad. These data indicate that the recombinant Ad is potentially a useful vector for vaccination.

Seasonal changes in the tissue-metal (Cd, Zn and Pb) concentrations in two ecophysiologically dissimilar earthworm species: pollution-monitoring implications

Metal (Cd, Pb, Zn) concentrations and contents were measured each month for thirteen consecutive months in two ecophysiologically distinct earthworm species, sampled from the vicinity of a disused Pb/Zn mine. Aporrectodea caliginosa, an endogeic species, enters diapause during unfavourable conditions; Lumbricus rubellus, an epigeic species, does not enter diapause. Cd concentrations were higher in A. caliginosa than in L. rubellus throughout the year: Pb concentrations were also usually higher in the endogenic species. Zn concentrations were fairly similar in both species, except during Winter and early Spring, when L. rubellus has significantly higher concentrations. Analysis of covariance indicated that the concentrations of Cd, Pb and Zn varied significantly over the thirteen-month period in L. rubellus, but only the non-essential metals (Pb, Cd) varied significantly in A. caliginosa. During diapause (observed only in the July sample), tissue concentrations of Cd and Zn in A. caliginosa were significantly lower than in 'active' worms; Pb concentrations were significantly higher during diapause. Since diapause was accompanied by a significant decrease in dry body mass, it was concluded that Pb is retained by earthworm tissues during the resting phase; but Cd and Zn are actively eliminated from the tissues before or during diapause. The implications of these findings on the use of earthworms for monitoring the relative degrees of metal contamination at different sites are discussed.

Short-term Pb accumulation by slugs sampled from clean and contaminated sites when fed artificial Pb-spiked diets

Slugs (Deroceras reticulatum and Arion subfuscus) were sampled from two distinct sites, an uncontaminated site at Dinas Powys and a Pb-contaminated, disusedmine site at Llantrisant. Batches of the slugs were exposed for ten days under laboratory conditions to an artificial diet consisting of a 5% (w/v) agar + 5% (w/v) sucrose matrix contaminated with different concentrations of Pb, as Pb (NO(3))(2). The food 'cubes' contained approximately 0, 10, 100, and 1000 microg Pb ml(-1). Tissue-Pb concentrations increased with increasing dietary-Pb concentration in both species. However, at the highest Pb exposure (1000 microg ml(-1)) the tissue-Pb concentrations in D. reticulatum and A. subfuscus sampled originally from the clean site were higher than those in their counterparts from the contaminated site, even though the Llantrisant slugs had significantly higher baseline Pb concentrations than the Dinas Powys slugs. It is suggested that these observations indicate metal tolerance phenotypically expressed as reduced accumulation in the populations with a history of Pb-exposure in their natural habitat. We discuss how biomonitoring may be affected by the way in which different slug populations deal with metals.

Distribution of epitopes within the amino acid sequence of the Epstein-Barr virus major envelope glycoprotein, gp340, recognized by hyperimmune rabbit sera

Epstein-Barr virus (EBV) is a major human pathogen for which the development of an effective vaccine remains an important goal. Rabbits were immunized with one of a set of 10 fusion proteins representing protein fragments from the EBV receptor-binding ligand and candidate subunit vaccine gp340. Sera from recipients of fragments from the amino-terminal half of the polypeptide chain bound gp340 in Western blot assays and ELISA but were not virus-neutralizing. The fine epitope specificity of these sera, and of EBV-neutralizing rabbit sera raised against whole EBV and gp340-containing immune-stimulating complexes, were assessed in a peptide ELISA. All but two of these sera bound peptides located between positions 236 and 327 in the 907 amino acids of the gp340 polypeptide chain. Among these it was possible to identify regions containing candidate virus-neutralizing B cell epitopes. The use of a gp340 fusion protein affinity column to isolate antibodies from EBV-neutralizing rabbit sera specific for this region suggests the presence of both continuous and discontinuous B cell epitopes with potential roles in EBV neutralization.

Protective immunization against Epstein-Barr virus-induced disease in cottontop tamarins using the virus envelope glycoprotein gp340 produced from a bovine papillomavirus expression vector

Inoculation with Epstein-Barr virus (EBV) induces malignant lymphomas in the cottontop tamarin (Saguinus oedipus oedipus). This provides an experimental animal model for assessing the efficacy of candidate EBV vaccines which are intended to reduce the incidence of human tumours associated with EBV infection. Previous work has shown that experimental vaccines based on the major virus envelope glycoprotein gp340 prepared from the membranes of EBV-infected cells are effective in protecting cottontop tamarins against EBV-induced disease. However, not all purified gp340 preparations induce protective immunity against EBV lymphoma in the tamarin. In this work, cottontop tamarins were immunized with recombinant gp340, produced using a bovine papillomavirus (BPV) expression vector, and a threonyl muramyl dipeptide adjuvant formulation. Although the recombinant-derived gp340 lacked the membrane anchor sequence of authentic gp340 and was expressed in mouse cells, it was immunogenic and induced virus-neutralizing antibodies. Healthy vaccinated tamarins were protected against EBV-induced disease. The demonstration that a recombinant gp340 product is able to elicit protective immunity in the cottontop tamarin is a significant step in the development of an EBV vaccine because previously it had not been clear whether a recombinant product would have the exact tertiary structure, including the necessary carbohydrate components, to induce protective immunity. A recombinant gp340 vaccine offers various advantages over production of the authentic molecule by laborious biochemical separation, including lower cost and the absence of potentially oncogenic EBV DNA. Therefore, recombinant gp340 produced using the BPV expression vector is suitable for development as a candidate EBV vaccine for a human Phase I trial and beyond.

Mapping of B-cell epitopes on the polypeptide chain of the Epstein-Barr virus major envelope glycoprotein and candidate vaccine molecule gp340

The Epstein-Barr virus (EBV) major envelope glycoprotein gp340 is the subject of current efforts to develop an EBV subunit vaccine. The importance of gp340-specific humoral immunity has been highlighted by studies of natural infection in humans and gp340 immunization of experimental animals. The former studies have demonstrated the presence of gp340-specific serum antibodies which mediate EBV neutralization, complement fixation, and antibody-dependent cellular cytotoxicity. The latter studies have often shown a correlation between the induction of gp340-specific EBV-neutralizing antibodies and protection from virus challenge. We have used a series of bacterial beta-galactosidase-gp340 fusion proteins and overlapping synthetic peptides from the gp340 open reading frame to map the positions of B-cell epitopes within the gp340 primary amino acid sequence. The data reported here indicate the presence of B-cell epitopes within the carboxy-terminal third of the gp340 polypeptide chain. These epitopes could not be detected with a peptide enzyme-linked immunosorbent assay, thereby suggesting that they are discontinuous. Affinity purification of antibodies with a gp340 fusion protein from the carboxy terminus of the gp340 polypeptide chain has been used to show that these antibodies are not EBV neutralizing in vitro. The consequences of these findings for future EBV vaccine development are considered.

Epstein-Barr virus vaccines

Epstein-Barr virus (EBV) is a human viral pathogen of considerable importance. More than 95% of the human population world-wide becomes infected with the virus during childhood, although in the West infection may be delayed until adolescence. The infection only has an undesirable significant clinical outcome in a tiny minority of cases, but because the virus is so ubiquitous the minority is numerically very significant. The virus is associated with two important human cancers, endemic Burkitt's lymphoma (BL) and undifferentiated nasopharyngeal carcinoma (NPC). These diseases have a very clearly defined geographical distribution in the Third World indicating a strong co-factor dependence. In the West, Epstein-Barr virus infection, when delayed to adolescence, is associated with infectious mononucleosis. The virus is also associated in the West with tumours arising in individuals undergoing immunosuppressive treatment or who are immunosuppressed as a result of HIV infection. More recently evidence has been obtained of an association with Hodgkin's disease which is very common in the West. A number of vaccines have been developed based on the EBV envelope glycoprotein gp340. Vaccination of those populations at risk from developing NPC or BL should lead to a reduction or elimination of these diseases. A safe and effective vaccine may also have a role in the prevention of EBV-related diseases in the West. Recombinant vaccinia, varicella and adenovirus vaccine vectors expressing gp340 are being developed and a recombinant-derived subunit vaccine based on the gp340 molecule is shortly to enter phase I human trials.

Purification and characterization of Epstein-Barr virus gp340/220 produced by a bovine papillomavirus virus expression vector system

Our initial results with a bovine papilloma virus (BPV) vector expression system indicated that we could produce significant amounts of Epstein-Barr virus (EBV) gp340/220 in the supernatant of a mouse fibroblast cell line. We have now extended these findings to show that the truncated version of gp340/220, where the membrane anchor sequence is deleted, is produced even after extended passage of the cells, at a level of approximately 1 mg/4 x 10(8) cells. A simple purification protocol using Sephacryl S300HR and gelatin agarose gives a product which is greater than 90% pure. This product is recognized by anti-gp340 monoclonal antibodies from five different epitope groups and induces antibody that recognizes the authentic gp340/220 and neutralizes EBV in vitro. The purified gp340/220 can be used in ELISA and stimulates the proliferation of T-cell clones specific for gp340/220. These characteristics, together with the fact that BPV-transformed lines have been utilized for the production of pharmaceuticals for use in humans, suggest that this gp340/220 is suitable as a source of antigen for vaccination to prevent EBV infection and related diseases.

An integrated study of the morphological and gross-elemental consequences of methyl mercury intoxication in rats, with particular attention on the cerebellum

Methylmercury accumulates in the kidney and liver of rats, but fairly selectively damages the cerebellum, resulting in the clinical symptoms of neurological ataxia after prolonged exposures. Within the cerebellum, morphological examination indicated that the small granule cells beneath the Purkinje layer are especially susceptible to the toxin, showing signs of pyknosis during the phase of locomotory disability, whilst the large Purkinje cells are relatively resistant to cytotoxic injury. Flame photometric and electron probe X-ray microanalysis (EPXMA) of digested samples of the major organs failed to detect any significant changes in the Na, K, Ca, Mg, S and P concentrations of the organs, including the cerebellum, at intervals after methylmercury administration by either gastric gavage or via the drinking water. It was suggested that if the lesion within the cerebellum is restricted, as the morphological evidence suggests, to a small cohort of functionally important granule cells, then it may be difficult to detect elemental changes within this subpopulation against the compositionally unaltered majority of cerebellar cells and their extracellular spaces. To identify and compositionally characterize the injured cells requires electron probe X-ray microanalysis of frozen sections, or fractured bulk samples. The deep-seated nature of the 'target cells' within the cerebellum presents formidable cryopreparative problems.

Identification of two T-cell epitopes on the candidate Epstein-Barr virus vaccine glycoprotein gp340 recognized by CD4+ T-cell clones

Current efforts to develop an Epstein-Barr virus subunit vaccine are based on the major envelope glycoprotein gp340. Given the central role of CD4+ T cells in regulating immune responses to subunit vaccine antigens, the present study has begun the work of identifying linear epitopes which are recognized by human CD4+ T cells within the 907-amino-acid sequence of gp340. A panel of gp340-specific CD4+ T-cell clones from an Epstein-Barr virus-immune donor were first assayed for their proliferative responses to a series of truncated gp340 molecules expressed from recombinant DNA vectors in rat GH3 cells, by using an autologous B lymphoblastoid cell line as a source of antigen-presenting cells. The first four T-cell clones analyzed all responded to a truncated form of gp340 which contained only the first 260 N-terminal amino acids. These clones were subsequently screened for responses to each of a panel of overlapping synthetic peptides (15-mers) corresponding to the primary amino acid sequence of the first 260 N-terminal amino acids of gp340. One clone (CG2.7) responded specifically to peptides from the region spanning amino acids 61 to 81, while three other clones (CG5.15, CG5.24, and CG5.36) responded specifically to peptides from the region spanning amino acids 163 to 183. Work with individual peptides from these regions allowed finer mapping of the T-cell epitopes and also revealed the highly dose-dependent nature of peptide-induced responses, with inhibitory effects apparent when the most antigenic peptides were present at supraoptimal concentrations. Experiments using homozygous typing B lymphoblastoid cell lines as antigen-presenting cells showed that the T-cell clones with different epitope specificities were restricted through different HLA class II antigens; clone CG2.7 recognized epitope 61-81 in the context of HLA DRw15, whereas clones CG5.15, CG5.24, and CG5.36 recognized epitope 163-183 in the context of HLA DRw11. The present protocol therefore makes a systematic analysis of CD4+ T-cell epitopes within gp340 possible; it will be necessary to screen gp340-specific T-cell clones from a variety of donors to assess the wider influence of HLA class II polymorphism upon epitope choice.

Salivary and serum IgA antibodies to the Epstein-Barr virus glycoprotein gp340: incidence and potential for virus neutralization

Human antibody responses to the Epstein-Barr virus (EBV) glycoprotein gp340 have been measured using purified preparations of the native molecule as the substrate in ELISAs. This glycoprotein is the dominant component of the EBV envelope and a major target for the virus-neutralizing antibody response. Healthy virus carriers (both Caucasian and Chinese) regularly show detectable anti-gp340 IgG in serum and, unexpectedly, 21-30% of these individuals are also serum anti-gp340 IgA positive. Chinese patients with the EBV-genome-positive malignancy nasopharyngeal carcinoma (NPC) show elevated serum IgA antibodies to gp340 but, given the background of responses amongst healthy virus carriers, anti-gp340 IgA titres are a poorer diagnostic indicator of NPC than serum IgA antibodies detectable by immunofluorescence against the multicomponent EBV early antigen (EA). Salivary IgA antibody responses to gp340 are potentially important as a means of neutralizing orally-transmitted virus. We detected salivary IgA (but not IgG) to gp340 in a minority (12-19%) of healthy virus carriers and in a higher proportion (49%) of NPC patients. Even saliva samples chosen for their relatively high anti-gp340 IgA titres showed only weak neutralizing activity against transforming EBV preparations whether from B95.8 cell culture supernatant or from the throat washing of an infectious mononucleosis patient. We conclude that in healthy virus carriers, salivary IgA responses to gp340 are unlikely to provide effective local immunity against re-infection with a second EBV strain.

Roots induced on cucumber cotyledons by the agropine Ri plasmid TR-DNA exhibit the transformed phenotype

Cucumber explants were transformed by Agrabacterium strains carrying Ri plasmids with functional TL and TR-DNAs, and by strains whose pRi had an intact TR-DNA but a disarmed TL-DNA lacking open reading frames (ORFs) 3 to 9, 10 (rol A), 11 (rol B), 12 (rol C), 13, 14, 15 (rol D), 16 and 17. Roots induced by all strains exhibited extensive root hair formation under axenic conditions, synthesised opines, and contained TR-specific DNA. These results confirm that the TR-DNA of an agropine Ri plasmid is able to elicit the transformed root phenotype in this plant.

Accumulation of heavy metals from polluted soils by the earthworm, Lumbricus rubellus: can laboratory exposure of 'control' worms reduce biomonitoring problems?

This paper compares the patterns of metal (Pb, Zn, Cd, Cu) accumulation in nine populations of the epigeic earthworm, Lumbricus rubellus, native on metalliferous soils, with the patterns of metal accumulation in batches of L. rubellus sampled from an uncontaminated site and maintained on the nine contaminated soils for 31 days under laboratory conditions. The primary findings were: (1) the Pb, Zn and Cd concentrations in the 'native' worms were significantly higher in most cases than in the 'introduced' worms; (2) multiple regression analyses indicated that the relationships between tissue and soil metal concentrations were similar for 'native' and 'introduced' worms; (3) high soil organic matter content reduced the bioavailability of Pb, but low pH increased Pb bioavailability. It was concluded that, although no phenotypic evidence of metal-tolerant ecotypes was obtained, the exposure of earthworms from uncontaminated soils to contaminated soils under laboratory conditions can provide meaningful integrative data concerning metal bioavailability in soils which, for biomonitoring purposes, often present formidable sampling problems.

A comparison of (Pb, Cd and Zn) accumulation in terrestrial slugs maintained in microcosms: evidence for metal tolerance

The relative tissue accumulation of Pb, Cd and Zn were compared in two populations each of two species of slugs (Arion subfuscus and Deroceras reticulatum). One population was resident at a contaminated Pb/Zn mine site, and the other population was from an uncontaminated site and was transferred for 20 days to microcosms established at the mine site. It was found that when the experiment was conducted during late spring (May), but not in late winter (February), that the Pb and Zn concentrations in the tissues of the 'transplants', were significantly higher than in the tissues of 'residents'; the Cd concentrations in the transplants, although significantly higher in the May sample than in February, did not exceed those of their 'resident' counterparts. It was postulated that: (a) Pb and Zn tolerance in slugs is phenotypically expressed by a reduction in metal accumulation; (b) Cd tolerance, if present, may be characterized by enhanced storage capacity; and (c) the presence of local metal-tolerant ecotypes is a biotic variable that may confound the relationship between dry tissue and environmental metal concentrations that forms a basis of pollution biomonitoring.

Validation of a first-generation Epstein-Barr virus vaccine preparation suitable for human use

The efficacy of a new vaccine preparation against Epstein-Barr (EB) virus was investigated in cotton-top tamarins. The vaccine consists of fast protein liquid chromatography-purified EB virus membrane antigen glycoprotein of 340 Kd (MA gp340) mixed with a synthetic muramyl dipeptide adjuvant emulsified in squalane containing a pluronic polymer; it is suitable for both scaled-up batch production and eventual administration to man. Vaccinated tamarins rapidly developed ELISA detectable high titre antibodies to MA gp340, and their sera became strongly EB virus-neutralising. After challenge with a massive 100% carcinogenic dose of EB virus, the vaccinated tamarins had a strikingly low level of circulating EB virus-carrying mononuclear cells, in contrast to a control animal, and remained entirely free of tumours. This first-generation vaccine has thus been validated in experimental animals and the way opened for a phase I human trial.

Epstein-Barr virus gene expression in malignant lymphomas induced by experimental virus infection of cottontop tamarins

Inoculation of cottontop tamarins with a large dose of Epstein-Barr virus (EBV) leads to the induction of multiple EBV genome-positive lymphomas. These tumors have been characterized as oligoclonal or monoclonal large-cell malignant lymphomas that closely resemble the EBV genome-positive B-cell lymphomas that arise in human allograft recipients. The expression of latent and lytic EBV-encoded proteins was investigated in these virus-induced tamarin lymphomas and in derived cell lines. The tamarin tumors were found to express EBV nuclear antigen 1 (EBNA 1), EBNA 2, EBNA leader protein, and the latent membrane protein (LMP) as determined both by immunohistochemical staining and by immunoblotting. However, within the limits of the immunoblotting assays, no expression of the EBNA 3a protein family could be detected. Assays for lytic-cycle proteins by using both polyclonal human sera and monoclonal antibodies against viral capsid antigen, early antigen, and membrane antigen (gp340/220) showed minimal, if any, expression of these antigens in the lymphoma biopsies. In contrast, the cell lines derived from these lymphomas, even in early passage, expressed abundant levels of the lytic-cycle antigens and also expressed the EBNA 3a protein as well as EBNA 1, EBNA 2, EBNA leader protein, and LMP. This finding suggests that the virus-lymphoma cell interaction, in particular the switch to lytic cycle, is subject to some form of host control in vivo. The expression of EBNA 2 and LMP in these tamarin lymphomas strengthens their resemblance to posttransplant lymphomas in humans, since these human tumors are also EBNA 2 and LMP positive (L. S. Young, C. Alfieri, K. Hennessy, H. Evans, C. O'Hara, K. Anderson, A. Rickinson, E. Kieff, and J. I. Cohen, submitted for publication). Since both proteins are known to be important effector molecules of virus-induced B-cell growth transformation in vitro, their expression in these lymphomas constitutes the best evidence for a direct oncogenic role for EBV in vivo.

Seasonal changes in metal levels (Cu, Pb, Cd, Zn and Ca) within the grey field slug, Deroceras reticulatum, living in a highly polluted habitat

Slugs (Deroceras reticulatum) (Muller)) were collected from a disused Pb/Zn mine site for a period encompassing 3 years. The analysis of whole body replicates, collected monthly for a period of one year, demonstrated a large variability in metal concentrations for each of the five metals (Cu, Pb, Cd, Zn and Ca) analysed. Nevertheless, a number of significant monthly differences in metal levels were found, the most regular being for Ca, and the least regular for Cu. Significant differences in metal body burdens were also found between slugs collected during the same month, but in consecutive years. The presence of such large and irregular variability greatly restricts the potential value of terrestrial slugs as biomonitors of heavy metal contamination.

Zinc sequestration by earthworm (Annelida: Oligochaeta) chloragocytes. An in vivo investigation using fully quantitative electron probe X-ray micro-analysis

The elemental compositions of chloragosome "granules" in the earthworm Lumbricus rubellus living in non-polluted and heavily Zn-polluted soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. The in vivo accumulation of Zn by the chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Zn was apparently bound by at least two ligand pools (Pool 1 = uncharacterised; Pool 2 = P-containing ligands, binding approximately 45% and 55% of the Zn, respectively) in the "control" chloragosomes. In Zn-contaminated chloragosomes, most (approximately 70%) was bound by P-containing ligand(s) but some (less than 1%) was also bound by S-containing ligands. It is suggested that the sequestration of Zn in chloragosomes results in the detoxification of the metal by accumulative immobilisation.

The effect of lead incorporation on the elemental composition of earthworm (Annelida, Oligochaeta) chloragosome granules

The elemental compositions of chloragosome 'granules' in the earthworm Lumbricus rubellus living in non-polluted (Dinas Powys) and heavily Pb-polluted (Wemyss) soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. High Pb concentrations were found in chloragosomes of Wemyss animals; Pb was not detected in chloragosomes of Dinas Powys animals. Partial correlation and regression analysis indicated that the in vivo accumulation of Pb by chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Pb is bound by P-containing ligand(s) in the chloragosome matrix. The sequestration of Pb by chloragosomes results in the detoxification of the metal by accumulative immobilization.

Demonstration in vitro of cell mediated immunity to Epstein-Barr virus in cotton-top tamarins

In the course of developing an effective Epstein-Barr (EB) virus vaccine, the immune responses in cotton-top tamarins to a tumourigenic dose of EB virus were studied. Cell mediated responses were measured using a tissue culture 'growth inhibition' assay where peripheral blood lymphocytes were tested for their ability to inhibit the outgrowth of autologous EB virus transformed lymphoblastoid cells. This system has previously been recognized as a very sensitive assay for detecting cell-mediated responses to EB virus in man. Using this assay no cell-mediated immunity was detected up to the time of death in two tamarins following injection with a tumourigenic dose of EB virus. However, two other animals which had recovered from tumours induced by a first dose of EB virus 18 months previously when subsequently re-stimulated with a second tumourigenic dose did exhibit cell-mediated responses. These latter animals remained healthy following the re-challenge and did not show evidence of EB virus-induced disease.

Prevention of Epstein-Barr (EB) virus-induced lymphoma in cottontop tamarins by vaccination with the EB virus envelope glycoprotein gp340 incorporated into immune-stimulating complexes

Experimental induction of malignant lymphomas can be achieved in the cottontop tamarin by inoculation with Epstein-Barr (EB) virus. This system provides an animal model for assessing the efficacy of vaccine protection against the virus which is intended to reduce the incidence of human tumours associated with EB virus infection, namely endemic Burkitt's lymphoma and undifferentiated nasopharyngeal carcinoma. Cottontop tamarins have been vaccinated with the major envelope glycoprotein of EB virus, gp340, incorporated into immune-stimulating complexes (iscoms) and were thereby protected against a 100% lymphomagenic dose of virus. The gp340 iscoms are highly immunogenic, requiring only a few micrograms of immunogen to induce protective immunity and thus would be a strong candidate for further development as an EB virus vaccine for use in man.

Recombinant vaccinia virus expressing Epstein-Barr virus glycoprotein gp340 protects cottontop tamarins against EB virus-induced malignant lymphomas

A strong association exists between Epstein-Barr (EB) virus and two human cancers, endemic Burkitt's lymphoma and nasopharyngeal carcinoma. In addition, the virus causes infectious mononucleosis [reviewed in Epstein and Achong, 1979, 1986] and more recently has been implicated in lymphomas arising in immunosuppressed individuals [Cleary et al., 1986]. The possibility of preventing or influencing the course of these diseases by vaccination has been advocated for a number of years [Epstein, 1976], especially in the case of undifferentiated nasopharyngeal carcinoma, which is the most common tumour of men in southern China and is prevalent in other specific regions; it therefore represents a major world cancer problem [Shanmugaratnam, 1971]. Two vaccinia virus strains were employed to make recombinants expressing the gene coding for the EB virus envelope glycoprotein, gp340, and were used to vaccinate cottontop tamarins. Protection against EB-virus-induced lymphoma was obtained in animals immunized with the laboratory (WR) strain recombinant but not with those recombinants derived from the vaccine (Wyeth) strain. Circulating antibodies to EB virus gp340 were not detected in any of the immunized animals.

Efficient purification of Epstein-Barr virus membrane antigen gp340 by fast protein liquid chromatography

A rapid and efficient procedure for the isolation of Epstein-Barr (EB) virus membrane glycoprotein gp340 has been developed. The mild, two step method consisted of anion exchange chromatography of B95-8 cell membrane detergent extracts followed by further purification by gel filtration. Production of homogeneous gp340 was achieved routinely with recoveries of at least 35% from starting material. The purified molecule, when injected into mice with a synthetic muramyl dipeptide adjuvant, N-acetylmuramyl-L-threonyl-D-isoglutamine ((Thr1)MDP), elicited high titres of EB virus-neutralizing antibody.

Earthworms as biological monitors of cadmium, copper, lead and zinc in metalliferous soils

Earthworms (Lumbricus rebellus and Dendrodrilus rubidus) were sampled from one uncontaminated and fifteen metal-contaminated sites. Significant positive correlations were found between the earthworm and 'total' (conc. nitric acid-extractable) soil Cd, Cu, Pb and Zn concentrations (data log1) transformed). The relationships were linear, and the accumulation patterns for both species were similar when a single metal was considered, even though there were species difference in mean metal concentrations. Generally, the earthworm Cd concentration exceeded that of the soil; by contrast, the worm Pb concentration was lower than the soil Pb concentration in all but one (acidic, low soil Ca) site. Our observations suggest that Cu and Zn accumulation may be physiologically regulated by both species. Total-soil Cd explained 82-86% of the variability (V2) in earthworm Cd concentration; 52-58% of worm Pb and worm Zn concentrations were explained by the total-soil concentrations of the respective metals. Total-soil Cu explained only 11-32% of the worm Cu concentration. The effect of soil pH, total Ca concentration, cation-exchange capacity (CEC) and organic carbon on metal accumulation by L. rubellus and D. rubidus was investigated by multiple regression analysis. Soil pH (coupled with CEC) and soil Ca had a major influence on Pb accumulation (V2 of worm Pb increased to 77-83%), and there was some evidence that Cd accumulation may be suppressed in extremely organic soils. The edaphic factors investigated had no effect on Cu or Zn accumulation by earthworms. In the context of biomonitoring, it is proposed that earthworms have a potential in a dual role: (1) as 'quantitative' monitors of total-soil metal concentrations (as shown for Cd); and (2) as estimators of 'ecologically significant' soil metal, integrating the effects of edaphic factors (as shown for Pb).

Calcium-lead interactions involving earthworms. Part 2: the effect of accumulated lead on endogenous calcium in Lumbricus rubellus

The calcium and lead burdens of tissue fractions of Lumbricus rubellus were quantified in 'native' animals from acidic and calcareous disused lead mines, and from control ('naive') animals exposed to lead-polluted soils under laboratory conditions. Most of the body burden of lead was accumulated within the posterior alimentary canal, and significant positive correlations were generally found between the calcium and lead burdens in this tissue fraction, which were evident in both the naturally and laboratory lead-exposed animals. The calcium:lead correlation is probably due to a proliferation of the calcium-rich, lead-sequestering chloragosome granules, and may thus be regarded as a specific tissue response to cellular lead incursion. No calcium-lead relationship was recorded in the rest (largely composed of the body wall) fraction of earthworms inhabiting the lead-polluted sites. However, a concomitant increase in calcium and lead in this tissue fraction of the laboratory lead-exposed control animals was noted. It is concluded that in naturally lead-exposed earthworms, the cells of this tissue fraction may be relatively resistant to the toxic effects of the metal. By contrast, it is apparent that a non-specific cytotoxic response by the cells of the rest of 'naive' animals occurs, as demonstrated by the concurrent increase in its calcium and lead burdens. These results suggest that a tolerance mechanism to lead, perhaps with a genetic basis, may exist in earthworms naturally exposed to lead.

Calcium-lead interactions involving earthworms. Part 1: The effect of exogenous calcium on lead accumulation by earthworms under field and laboratory conditions

Earthworms (Lumbricus rubellus and Dendrodrilus rubidus) were collected from several acidic and calcareous abandoned ferrous metalliferous mine sites. Tissue lead concentrations were substantially lower than the total soil lead concentrations, except at one site (Cwmystwyth) where the tissue lead concentrations of both species were approximately 5 to 10 times higher than that of the soil. Soil lead was the major factor in determining the tissue lead concentration, although it was demonstrated that both soil pH and soil calcium concentration could markedly increase the % variance in tissue lead concentration. These findings help explain the apparent anomaly in tissue lead concentrations of earthworms from Cwmystwyth, where the soil is acidic and has exceptionally low calcium concentrations. Soil-liming experiments provided supportive evidence that soil pH, coupled with soil calcium, influences lead accumulation by earthworms, but a filter paper feeding experiment provided unequivocal evidence that soil calcium concentration alone can influence lead accumulation by earthworms. It is concluded that, although lead accumulation by earthworms is influenced by both physico-chemical and biochemical mechanisms, the latter over-rides the former, i.e. soil calcium is more important factor in determining the accumulation of lead earthworms than is soil pH.

Varicella-zoster virus as a live vector for the expression of foreign genes

The previous demonstration of the efficacy and tolerability of the Oka strain of varicella-zoster virus (VZV) in clinical trials involving vaccination of both normal and immunocompromised individuals has laid the foundation for its use in preventing chickenpox. In this context, VZV could be useful as a vector for vaccinating against other infectious agents as well. As an initial application, a live recombinant VZV expressing Epstein-Barr virus (EBV) membrane glycoproteins (gp350/220) was generated by inserting a gene fusion of the VZV gpI promoter and hydrophobic leader-encoding sequence with the gp350/220 coding sequence into the thymidine kinase (TK) gene of VZV (Oka). Insertion of the foreign DNA into the thymidine kinase gene was demonstrated by Southern blot analysis and the ability of the recombinant virus to replicate in the presence of bromodeoxyuridine. RNA splicing, glycosylation, and plasma membrane presentation of gp350/220 in cells infected with the recombinant virus were similar to those seen in EBV-infected cells. In addition, the expression of VZV-specific glycoproteins was unaltered by the concomitant expression of this large foreign glycoprotein. Thus, VZV can be used as a live viral vector for active immunization against EBV and other pathogens.

Protection of cottontop tamarins against Epstein-Barr virus-induced malignant lymphoma by a prototype subunit vaccine

Epstein-Barr (EB) virus is one of the five herpesviruses of man. Strong links between this agent and the chain of events causing two human cancers, endemic Burkitt's lymphoma and undifferentiated nasopharyngeal carcinoma, have long been evident (reviewed in ref. 1). Because of this, and because of the very high incidence of nasopharyngeal carcinoma in certain large populations, it was suggested in 1976 that a vaccine should be developed against EB virus to prevent infection and thereby reduce tumour incidence amongst those at risk. The virus-determined membrane antigen (MA) was proposed as immunogen because it was known to elicit naturally occurring virus-neutralizing antibodies in man and because analogous antigens had been shown to act as effective experimental vaccines for preventing the herpesvirus-induced lymphomas of Marek's disease in chickens. Progress has been achieved in defining, quantifying and preparing MA molecules, and in enhancing their immunogenicity; a sensitive assay for antibodies to MA has been elaborated. Here we report that isolated cell membranes expressing MA, or purified MA glycoprotein of relative molecular mass (Mr) 340,000 (gp340), have been used to vaccinate cottontop tamarins (Saguinus oedipus oedipus), and that animals receiving either preparation were protected against the effects of a 100% tumour-inducing challenge dose of EB virus.

Individual tumors of multifocal EB virus-induced malignant lymphomas in tamarins arise from different B-cell clones

Cotton-top tamarins were inoculated with sufficient Epstein-Barr virus to induce multiple tumors in each animal within 14 to 21 days. The tumors consisted of large-cell lymphomas that contained multiple copies of the Epstein-Barr virus genome and generated Epstein-Barr virus-carrying cell lines showing no detectable consistent chromosomal abnormality. Hybridization of tumor DNA with immunoglobulin gene probes revealed that each lymphoma was oligo- or monoclonal in origin and that individual tumors from the same animal arose from different B-cell clones. Thus the virus induced multiple transformation events in tamarins in vivo to cause malignant tumors resembling the Epstein-Barr virus-associated lymphomas of patients with organ transplants.

Large-scale purification of Epstein-Barr virus membrane antigen gp340 with a monoclonal antibody immunoabsorbent

A purification method has been elaborated to isolate Epstein-Barr (EB) virus membrane antigen, gp340, in milligram amounts. The gp340 was prepared from detergent extracts of B95-8 cells by affinity chromatography with a monoclonal antibody immunoabsorbent. Bound material was eluted and the eluate, consisting of 50% gp340, was then fractionated by gel filtration. The final gp340 product was antigenically active and 95% pure. The purification method was found to be rapid and reproducible with no loss of the ability of the immunoabsorbent to retain gp340 after repeated elution. The procedure provides suitable material to permit the detailed structural analysis of gp340 necessary for both vaccine design and for the investigation of the role of gp340 in immunity to EB virus infection.

A structural investigation of the Epstein-Barr (EB) virus membrane antigen glycoprotein, gp340

Epstein-Barr (EB) virus membrane antigen (MA) glycoprotein (gp340) purified by a molecular weight-based technique has been subjected to biochemical analysis. Following treatment with glycosidases or tunicamycin during synthesis, the carbohydrate moiety was found to be made up of both O-linked and N-linked types and to constitute about 50% of the molecular mass. Digestion studies with neuraminidase and oligosaccharidase have indicated that the molecule is heavily sialated with most of the sialic acid located on the O-linked sugars. The high carbohydrate content of gp340 appears to confer resistance to proteolysis; thus, V8 protease was only effective at concentrations above 1 mg/ml when three large fragments of mol. wt. 330K, 190K and 160K were generated. Removal of sialic acid before V8 protease digestion did not alter this pattern nor affect the antigenicity of the digestion fragments. Antigenicity of the intact molecule was likewise unaffected by removal of sialic acid nor were the O-linked and N-linked carbohydrate moieties essential for this property. The binding of virus-neutralizing human sera and monoclonal antibody by gp340 from which either O-linked or N-linked sugars had been removed seems to indicate that the sites on the molecule that generate the neutralizing antibodies are present in the protein component. The significance of these results is discussed in relation to the development of a subunit vaccine against EB virus.

Comparative immunogenicity studies on Epstein-Barr virus membrane antigen (MA) gp340 with novel adjuvants in mice, rabbits, and cotton-top tamarins

The effectiveness of immunisation of mice, rabbits, and cotton-top tamarins with small amounts of EB virus MA glycoprotein gp340 , incorporated into artificial liposomes, has been compared using various routes of injection with or without additional adjuvants. Liposomes containing gp340 gave specific high titre antibodies after i.p. or i.v. administration, and the addition of lipid A to the liposomes resulted in a significant enhancement of the response. Antibodies generated by the above procedure were virus neutralising and bound gp340 specifically. These findings indicate an advantageous approach for use with a prototype vaccine for the prevention of EB virus infection.

Purification and properties of the gp340 component of Epstein-Barr virus membrane antigen in an immunogenic form

Preparative SDS-polyacrylamide gel electrophoresis has been used in the purification of the gp340 component of Epstein-Barr (EB) virus-determined membrane antigen (MA), in tractable quantities, from the B95-8 marmoset lymphoblastoid cell line. Successful renaturation of the purified molecule was achieved. This procedure gave a 50-fold increase in the recovery of antigen compared to conventional techniques. The data suggest that the antigenic sites recognized by human sera containing antibodies to MA are largely confined to the protein portion of the molecule. An eightfold improvement in the yield of gp340 was obtained when B95-8 cells were cultured in the presence of 12-O-tetradecanoyl-phorbol-13-acetate. Gel filtration studies indicate that the major polypeptide components of MA are not associated in detergent solution. Immunization of rabbits with purified and renatured gp340 resulted in the generation of high-titre antisera which were specific for gp340, demonstrating that antigen prepared by this procedure is suitable for further evaluation as an experimental vaccine against EB virus infection.

Purified Epstein-Barr virus Mr 340,000 glycoprotein induces potent virus-neutralizing antibodies when incorporated in liposomes

The purified Mr 340,000 glycoprotein component of Epstein-Barr (EB) virus-induced membrane antigen complex incorporated into liposomes was shown to be a potent immunogen in mice. High-titer antisera were induced that (i) are specific for membrane antigen components without absorption, (ii) bind the antigens induced by three different EB virus isolates, and (iii) neutralize the ability of the virus to transform fetal cord blood lymphocytes in vitro. The development of this immunogenic form of purified antigen provides an important step towards a potential subunit vaccine against Epstein-Barr virus infection.

Quantification of an Epstein-Barr virus-associated membrane antigen component

A method is described for the preparation of a 125I-labelled membrane antigen (MA) component (gp340) from B95-8 cell membranes using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Good yields of antigenic material were obtained when renaturation of the [125I]gp340 was carried out by removal of SDS in the presence of urea and subsequent removal of the urea. The availability of purified, radiolabelled gp340 has provided the essential basis for the development of a radioimmunoassay which, for the first time, permits quantification of this antigen. The assay has been used to demonstrate that cell membrane MA is a better source of gp340 for large-scale work than is the Epstein-Barr virus envelope and to measure the increase in expression of gp340 following treatment of cells with 12-O-tetradecanoyl-phorbol-13-acetate (TPA).

The accumulation and intracellular compartmentation of cadmium, lead, zinc and calcium in two earthworm species (Dendrobaena rubida and Lumbricus rubellus) living in highly contaminated soil

The earthworm Lumbricus rubellus contained more Ca and Zn, and less Pb and Cd, than Dendrobaena rubida living in the same contaminated disused-mine soil. Differences in the kinetics of Ca turnover may account for some of the inter-specific differences in heavy metal burdens, although the calciferous glands do not seem to be directly involved in heavy metal excretion. A comparison of the present findings with published data indicated that the concentration of soil Ca and the bioavailability of heavy metals, both factors being allied to soil pH, are important exogenous determinants of heavy metal accumulation by different earthworm populations. Electron microprobe X-ray analysis of air-dried smears of chloragogenous tissue showed that the metals were fairly specifically compartmentalized into two distinct organelles in both worms: Ca, Pb and Zn were found (associated with P) in the chloragosomes; Cd was found (with S and probably in stoichiometric association) in a more electron-lucent vesicular component, designated the 'cadmosome', but which may be identical with the debris vesicles which are characteristic inclusions in conventionally-fixed chloragocytes. The in vivo incorporation of Pb by the chloragosomes of D. rubida was accompanied by the loss of Ca, Zn and P.

The elemental composition of the chloragosomes of two earthworm species (Lumbricus terrestris and Allolobophora longa) determined by electron probe X-ray microanalysis of freeze-dried cryosections

The elemental composition of the chloragosomes of the two earth-worm species, one with complex highly active Ca-secreting calciferous glands (L. terrestris) and the other with non-secretory glands (A. longa), was determined by the electron probe X-ray microanalysis of unfixed freeze-dried cryosections. The predominant constituents of the chloragosomes of both species were P, Ca, Zn and S, with lesser quantities of K, Cl and Fe. The most striking species differences in chloragosomal chemistry were the higher concentrations (expressed as relative mass fractions) of P(x 2.1), Ca(x 1.5), and Zn(x 2.3) in L. terrestris, and the much higher S(x 19.6) in A. longa. These differences were discussed in relation to the general ecophysiology of the two species, and more specifically in relation to heavy metal uptake and binding.

A morphological and electron-microprobe study of the inorganic composition of the mineralized secretory products of the calciferous gland and chloragogenous

The two pairs of lobes of the calciferous gland if the earthworm Lumbricus terrestris are specialized oesophageal diverticulae that secrete spherites ranging from 0.5 - 7.0 micrometers in diameter. Correlative transmission and scanning electron microscopy indicated that the spherites (which are predominantly CaCO3) are formed extracellularly in distinctive bays bounded by secretory-cell processes, and are mobilized anteriorly from the gland lumina to the lumen of a non-secretory pouch, where the majority coalesce and undergo phase transformation to concretions 0.5 - 1.0 mm in diameter consisting of a mass of cuboidal crystals with facets up to 40 micrometers. The distribution of Sr(0.1 ml 5% SrCl2 injected into the posterior coelomic cavity) was monitored in the mineralized secretory products of the calciferous glands by X-ray microanalysis of 10 micrometers - thick air-dried cryostat sections in a SEM. Strontium was not detected in chloragosomes at 2h and 24h post-injection. Strontium was transported anteriorly and specifically incorporated into gland spherites (detectable within 2h). This technique of Sr localization afforded sufficient structural and analytical resolutions to provide a confirmation of the sequence of extracellular changes in the gland/pouch system. In addition we were able to distinguish a population of growing spherites from the vast majority of mature spherites; size alone was a singularly poor indication of spherite growth. The major element constituents of the chloragosomes were P, Ca and Zn (Ca: P ranging from 0.4 to 1.0; Zn: P from about 0.05 to 0.45). Analysis of individual spherites showed that Ca was probably bound to P or P-containing matrix components, whilst Zn was probably linked to one or more different but unknown constituents.

Antigenic differences between the membrane antigen polypeptides determined by different EB virus isolates

The antigenic specificities of the membrane antigen (MA) complex of three Epstein-Barr (EB) virus-producing cell lines have been compared by complete absorption of an anti-MA antiserum with P3HR-1 cells, followed by testing for residual anti-MA antibody activity against B95-8 and QIMR-WIL cells. Indirect membrane immunofluorescence showed that the absorbed serum, which had lost the capacity to bind P3HR-1 cells, nevertheless gave bright staining on a small proportion of B95-8 cells. SDS-polyacrylamide gel electrophoretic analysis of 125I-labelled MA polypeptides showed that the absorbed serum was able to isolate MA polypeptides from both B95-7 and QIMR-WIL cells, but not from P3HR-2 cells. The results demonstrate that there is substantial sharing of antigenic specificities between the MA determined by three isolates of EB virus, and some antigenic divergence.

Observations on the EB virus envelope and virus-determined membrane antigen (MA) polypeptides

Experiments have been carried out to identify the polypeptide components of the Epstein-Barr (EB) virus-determined membrane antigen (MA) complex. Cells were radioiodinated using lactoperoxidase and the 125I-labelled surface antigens, released by Triton X100, were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) after complexing either with human sera having anti-MA activity or with a rabbit antiserum to EB virus. Using cells carrying EB virus isolated from four different conditions, including for the first time nasopharyngeal carcinoma (NPC), we have demonstrated four major polypeptides. One, with a molecular weight of 85,000, was remarkedly constant irrespective of the cell line from which it came; two, with molecular weights varying from 240,000 to 270,000 and from 320,000 to 340,000, showed minor differences in mobility apparently depending on the species of origin of the cells (human or marmoset), rather than disparity between strains of virus. A fourth component, of 160,000 daltons, was found on only two of the cell lines studied. In addition, it has been shown for the first time that the same polypeptides composing the MA complex are present on the viral envelope itself. The fact that the rabbit antiserum to EV virus recognized only the two highest molecular weight MA components, yet showed virus-neutralizing activity, indicates the importance of these two polypeptides for use in a vaccine designed to induce virus-neutralizing antibodies.