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Epstein-Barr virus (EBV), the cause of infectious mononucleosis, is involved in the pathogenesis of several human cancers, the highest frequency of association being found in undifferentiated nasopharyngeal carcinoma and endemic Burkitt's lymphoma. The development of animal models in which potential vaccines can be tested is important. EBV infection of the common marmoset, using the M81 strain originally derived from a patient with nasopharyngeal carcinoma, induces a carrier state in this animal. Persistent infection is characterized by the production of antibodies to viral antigens, and the secretion of EBV DNA into buccal fluids. Following immunization with envelope glycoprotein gp340 derived from a bovine papilloma virus expression vector, prior to EBV infection, viral DNA was detected significantly less frequently in the buccal fluids of immunized, than of nonimmunized, infected animals, indicating that although the carrier state had not been abolished, it had been altered. A reduction in virus load was also observed when offspring of seronegative, and on occasion seropositive, parents were immunized neonatally, before EBV challenge.

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Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with a variety of life-threatening diseases in humans. Therefore the development of an effective vaccine is an important objective. Many of the initial studies of vaccine efficacy analyse the ability of vaccine preparations to prevent the induction of lymphomas in cottontop tamarins by the B95-8 strain of EBV. We used a vaccinia virus recombinant expressing gp340, vMA1, tested previously in the cotton-top tamarin, to evaluate a common marmoset model in which the challenge virus, M81, resembles more closely the wild-type strains of EBV in the general population than does the standard B95-8 strain. We characterised the M81 strain of EBV with respect to the sequence of its gp340/220 gene and in regard to the presence of a region deleted in B95-8. Replication of the challenge virus in the group vaccinated with vMA1 was decreased when compared to control groups.

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Type 2 diabetes has been postulated to be a "thrifty genotype" that aids fuel conservation; to investigate this hypothesis, type 2 diabetic and nondiabetic subjects, normal weight and obese, were studied after both 6 days on a 700-calorie diet and 6 days on a 2,800-calorie diet. On 2,800 calories per day, the median basal plasma glucose was raised in diabetics compared with nondiabetic subjects (median, 5.5 and 4.5 mmol/L, respectively; P = .003), but on the low-energy diet there was no difference (4.1 and 3.7 mmol/L, respectively; P greater than .05). Basal plasma insulin levels were similar in the diabetic and nondiabetic subjects and were twofold to threefold higher on the high- than low-energy diet in both diabetic (median, 7.8 and 3.1 mU/L on high- and low-energy diets, respectively; P = .007) and nondiabetic subjects (6.8 and 2.6 mU/L, respectively; P = .005). Similarly, the postprandial insulin concentrations increased to the same degree on the high- compared with the low-energy diet in diabetic (median postprandial increment, 14.9 and 3.4 mU/L; P = .005) and nondiabetic patients (9.5 and 3.0 mU/L; P = .005) and the beta cells in type 2 diabetes appeared to modulate normally to different calorie intakes. On both diets, the diabetic subjects had an impaired first-phase insulin response to an intravenous glucose load compared with nondiabetic subjects (high-energy diet median first-phase increment, 4.3 and 21.2 mU/L in diabetic and nondiabetic subjects, P = .0007; low-energy diet, 4.0 and 20.4 mU/L, respectively, P = .003).(ABSTRACT TRUNCATED AT 250 WORDS)

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The B lymphocytes of the common marmoset Callithrix jacchus can be immortalized by infection with Epstein-Barr virus (EBV) in vitro (Desgranges et al., 1976). C. jacchus is susceptible to infection with the blood stages of several species of malaria parasite including the line designated MVF1 (Mitchell et al., 1988) from which it recovers and shows immunity to reinfection. By exploiting these two phenomena, EBV-transformed, marmoset lymphoblastoid cell lines secreting antibodies to malaria parasite antigens have been generated and cloned. We believe this to be the first time that monoclonal antibodies (MAbs) have been raised from common marmosets. Since numerous and diverse human pathogens can infect this small primate in the laboratory, these methods may prove generally applicable for the generation of MAbs whose specificities derive from immune responses to infection.

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Infection with Plasmodium vivax was established in splenectomized Callithrix jacchus marmosets by inoculation of parasitized blood from Aotus trivirgatus carrying the Vietnam Palo-Alto line of P. vivax. Subsequent blood passage through intact marmosets resulted in higher peak parasitaemias (about 1% of red cells infected) and the loss of stainable Schüffner's dots in infected cells. Primary infections with the adapted line were patent for 74 days or more, and induced both a substantial antibody response, as determined by indirect fluorescence, and some lymphocytosis, but no marked anaemia. Marmosets which had recovered from their primary infection (or in which it was drug-cured) suffered abbreviated patency with low-grade parasitaemia on re-infection.

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A soluble-phase proinsulin assay has been developed which does not require solid-phase antibody-binding. A human proinsulin standard curve is prepared in insulin-free and proinsulin-free plasma for comparison with unknown plasma samples. Proinsulin and insulin are bound with excess anti-insulin antiserum, and free C-peptide is removed by charcoal adsorption. The supernatant is then assayed using a routine C-peptide radioimmunoassay which utilises anti-C-peptide antiserum. The sensitivity of the assay (2 standard deviations above zero) is 9 pmol/L using 200 microL plasma sample. The assay is free from insulin cross-reactivity up to 100 mU/L and C-peptide up to 2000 pmol/L. Between-assay CV is 13% at 100 pmol/L. The assay has been used in subjects with hypoglycaemia of various aetiologies and has shown that a raised plasma proinsulin in the presence of hypoglycaemia can occur in sulphonylurea-induced and reactive hypoglycaemia as well as in insulinomas. After hyperglycaemic clamps at 7.5, 10 and 15 mmol/L glucose, type II diabetics both on and off sulphonylurea, were found to have lower proinsulin concentrations compared with normal subjects, commensurate with the diabetics' lower insulin responses.

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Quantitative morphometry of immunostained pancreatic islet cells in a surgical specimen from a maturity-onset diabetic (MOD) patient (A) has been combined with a study of beta-cell secretion in him and his MOD son (B). The morphometry showed intra-islet amyloid deposits in 24% of islet sections which is a similar distribution to that found in 7 other MODs, (median 24%, range 0-95%). The distribution of islet cells in the pancreas from A was similar to the 7 MODs and 9 age matched non-diabetic subjects (mean beta-cell area per exocrine area, A, 2%; MODs, 1.45%; controls 1.8%). There was a significantly smaller percentage beta-cell area per islet area in A and the other MODs compared to the controls. Beta-cell secretion was studied by an intravenous glucose infusion, 5 mg/kg ideal body wt. min-1 in A and B and 4 other MODs on sulphonylurea or diet therapy. Fasting plasma glucose was high in both A and B (16 and 7.6 mmol/l respectively) in spite of sulphonylurea therapy. Similarly, A and B had elevated fasting plasma levels of insulin, (0.055 and 0.13 pmol/ml respectively) and C-peptide (0.573 and 1.39 pmol/ml respectively). Plasma proinsulin formed a higher percentage of the immunoreactive insulin in fasting plasma samples of both A (36%) and B (43%) than in less hyperglycaemic MODs on diet alone (26%) or sulphonylurea therapy (17%) and the glucose stimulated proinsulin content was even higher (A, 50%; B, 53%; MODs, diet, 19%; sulphonylureas, 16%). Elevated proinsulin levels in a patient with islet-amyloid is consistent with the hypothesis that amyloid may be derived from abnormal beta-cell secretion.

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A 76-year-old man with fasting hypoglycaemia had impaired in-vitro binding of insulin to erythrocyte receptors. The immunoglobulin fraction of his plasma inhibited binding of insulin to normal donor erythrocytes in vitro. Autoantibodies may have stimulated the insulin receptor and produced hypoglycaemia. Hodgkin's disease developed and may have induced the autoimmunity. The hypoglycaemia did not respond to plasmapheresis or azathioprine alone, but it remitted after the addition of prednisolone, and the erythrocyte receptor binding of insulin became normal.

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The steady-state basal plasma glucose and insulin concentrations are determined by their interaction in a feedback loop. A computer-solved model has been used to predict the homeostatic concentrations which arise from varying degrees beta-cell deficiency and insulin resistance. Comparison of a patient's fasting values with the model's predictions allows a quantitative assessment of the contributions of insulin resistance and deficient beta-cell function to the fasting hyperglycaemia (homeostasis model assessment, HOMA). The accuracy and precision of the estimate have been determined by comparison with independent measures of insulin resistance and beta-cell function using hyperglycaemic and euglycaemic clamps and an intravenous glucose tolerance test. The estimate of insulin resistance obtained by homeostasis model assessment correlated with estimates obtained by use of the euglycaemic clamp (Rs = 0.88, p less than 0.0001), the fasting insulin concentration (Rs = 0.81, p less than 0.0001), and the hyperglycaemic clamp, (Rs = 0.69, p less than 0.01). There was no correlation with any aspect of insulin-receptor binding. The estimate of deficient beta-cell function obtained by homeostasis model assessment correlated with that derived using the hyperglycaemic clamp (Rs = 0.61, p less than 0.01) and with the estimate from the intravenous glucose tolerance test (Rs = 0.64, p less than 0.05). The low precision of the estimates from the model (coefficients of variation: 31% for insulin resistance and 32% for beta-cell deficit) limits its use, but the correlation of the model's estimates with patient data accords with the hypothesis that basal glucose and insulin interactions are largely determined by a simple feed back loop.

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Decreased insulin binding to receptors is associated with the insulin resistance of obese and non-obese non-insulin-dependent diabetics. 'Down Regulation' by elevated insulin levels has been suggested as the cause, but factors influencing receptor affinity have not been examined. To investigate the control of receptors in diabetes, 10 non-insulin-dependent diabetics and 10 normal subjects were studied after 6 d on low and 6 d on high calorie diets of fixed composition (700 and 2800 Kcal/70 kg of ideal body weight). The binding of insulin by erythrocytes of non-diabetics, as predicted, increased on the low and decreased on the high calorie diets, due to altered affinity. In contrast, the binding in the diabetics did not change significantly, and the responses to the low and high calorie diets were less than in the normal subjects (P less than 0.05 and P less than 0.001 respectively). Indeed, the insulin binding in all 5 non-obese diabetics changed in the opposite direction (P less than 0.01) to the non-diabetics, whereas the obese diabetics showed a mixed response. The changes in receptor binding in the diabetics was completely unrelated to the diurnal plasma insulin levels during 24 h studies. We conclude that the dietary regulation of erythrocyte insulin receptor affinity in non-insulin-dependent diabetes is abnormal, and insulin receptor affinity is regulated by factors other than insulin. The relation of this abnormality to the insulin resistance needs further investigation.

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The relative hypoglycemic effects of pulsatile versus steadily infused insulin have been examined in six normal subjects in whom pancreatic insulin output was suppressed by somatostatin-14. Soluble insulin was infused continuously overnight on one occasion and on another occasion the same quantity was given in pulses of 2-min duration with a gap of 11 min. The mean plasma glucose concentrations were lower when pulsed insulin was given [mean for the last hour: 4.66 +/- 0.08 mmol/L (+/- SEM) versus 5.53 +/- 0.06 mmol/L (+/- SEM) for steady infusion], diverging significantly (P less than 0.05 paired t test) 7 h after the start of the study. The specific binding of 125I(A14)mono-iodo-insulin to monocytes was greater after pulsed insulin (2.9% with pulsed versus 2.4% with steadily infused insulin at tracer-only point; P less than 0.02 paired t test). Thus, intravenous insulin has greater hypoglycemic effect when pulsed, possibly mediated by greater insulin receptor binding.

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In comparison to a traditional low carbohydrate diet (LC), the effect of an isocaloric high carbohydrate, high fibre diet (HC) upon the insulin binding to mononuclear blood cells of seven non-insulin-dependent diabetics was examined. Each subject, in random order, took both diets for 6 weeks each. There was no significant difference in weight during either dietary period, but a significant (P less than 0.05) increase in the monocyte insulin binding activity on the HD diet (tracer specific binding: 4.2% HC; 3.5% LC). This was accompanied by a significantly (P less than 0.02) lower fasting plasma glucose concentration (LC = 7.1 mmol/l; HC = 6.1) without a significant change in the fasting plasma insulin level. In contrast to the usual low carbohydrate diet, a high carbohydrate diet tends to correct the lowered insulin receptor status observed in maturity-onset diabetics.

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A patient wtih acute epidemic pulmonary histoplasmosis was treated with 500 mg of amphotericin B. Traditionally, such patients have not been treated, since the illness is usually self-limited; however, fatalities have been reported, and some authorities have recommended therapy with small doses of amphotericin B. Patients with acute pulmonary histoplasmosis who are acutely ill should be considered for low-dose treatment with amphotericin B, inasmuch as they are likely candidates for early dissemination. Cures have been reported with as little as 105 mg of amphotericin B administered intravenously.

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