Coxsackievirus B cardiopathy and angiopathy in the hypercholesterolemic host

Enterovirus in arteriosclerosis: A pilot study

BACKGROUND

Various pathogens have been suspected to play a role in the initiation or amplification of the atherosclerotic lesions. Both experimental and epidemiological arguments plead for a possible role of enterovirus in this process.

OBJECTIVE

To determine the prevalence of enterovirus genome in atherosclerotic plaques, in comparison with Chlamydia pneumoniae, human cytomegalovirus (hCMV) and herpes simplex virus.

STUDY DESIGN

Pilot study on 18 patients who underwent artery resection. Five artery samples were tested for each patient and each pathogen by using PCR techniques whose sensitivity was evaluated for this kind of specimen. The quality of the extraction step was assessed by amplification of a fragment of the human aldolase A gene.

RESULTS

The genome of at least one infectious agent was detected in artery samples from 7 of the 18 patients (38.9%). In all cases, only one of the five aliquots was found positive; a confirmation was done by sequencing the PCR product. With regards to enterovirus, four patients (22.2%) were detected positive (one of them being also positive for hCMV).

CONCLUSIONS

These results suggest that small amounts of enterovirus genome are commonly found in lesions of patients with advanced arteriosclerosis. Further studies are needed to evaluate the clinical significance of this association.

Coxsackievirus-mediated hyperglycemia is enhanced by reinfection and this occurs independent of T cells

The induction of autoimmunity by viruses has been hypothesized to occur by a number of mechanisms. Coxsackievirus B4 (CB4) induces hyperglycemia in SJL mice resembling diabetes in humans. While virus is effectively cleared within 2 weeks, hyperglycemia does not appear until about 8-12 weeks postinfection at a time when replicative virus is no longer detectable. In SJL mice, reinfection with CB4 enhanced the development of hyperglycemia. As predicted, the immune system responded more rapidly to the second infection and virus was cleared more swiftly. However, while infiltrating T cells were found within the pancreas, depletion of the CD4 T cell population prior to secondary infection or use of CD8 knock-out mice had no effect on the development of virus-mediated hyperglycemia. In conclusion, enhanced hyperglycemia induced by CB4 occurs independent of the T cell response.

Procoagulant and inflammatory response of virus-infected monocytes

BACKGROUND

Monocytes play a prominent role in inflammation, coagulation and atherosclerosis by their ability to produce tissue factor (TF) and cytokines. The aim of the present study was to establish whether virus-infected monocytes initiate coagulation. In addition, the production of cytokines by monocytes may accelerate the chronic process of atherosclerosis and may contribute to coronary syndromes by eliciting plaque instability.

MATERIALS AND METHODS

Monocytes were isolated by Vacutainer(R), BD Biosciences, Alphen aan den Rijn, Netherlands and subsequent magnetic cell sorting (MACS(R), Milteny Biotec, Bergish Gladbach, Germany). Coagulation times in normal pooled plasma and Factor VII-deficient plasma were measured after infection with cytomegalovirus (CMV), Chlamydia pneumoniae (Cp) and influenza A\H1N1. Anti-TF antibodies were added to neutralize TF expressed on monocytes. Interleukins (IL) 6, 8 and 10 were measured in the supernatants.

RESULTS

Chlamydia pneumoniae- and CMV-infected monocytes decreased the clotting time by 60%, and influenza-infected monocytes by 19%, as compared to uninfected monocytes. Procoagulant activity was absent when Factor VII-deficient plasma or anti-TF antibodies were used. Monocytes produced both IL-6 and IL-8 after infection with CMV (317 pg mL-1 and 250 pg mL-1) or Cp (733 pg mL-1 and 268 pg mL-1). Similar results were obtained for influenza virus-infected monocytes, but the levels of both cytokines were 3-5-fold higher (1797 pg mL-1 and 725 pg mL-1). Interleukin-10 was not produced by infected monocytes.

CONCLUSION

The procoagulant activity of virus-infected monocytes is TF-dependent. Although influenza infection did not generate a significant reduction in clotting time, the pronounced expression of IL-6 and IL-8 may induce local and/or systemic inflammatory reactions, which may be associated with plaque rupture and atherosclerosis. The lack of production of the anti-inflammatory cytokine IL-10 may even accelerate these processes.

Effect of prolonged modified fasting in obese persons on in vitro markers of immunity: lymphocyte function and serum effects on normal neutrophils

The effects of nutritional manipulation on immune function have been extensively studied in animals, but few studies have examined dietary restriction in humans. Obese patients enrolled in a protein-sparing, calorically restricted diet were monitored over a 3-month period with in vitro examination of mitogen- and antigen-induced lymphocyte blastogenesis. The sera from these patients were evaluated for effects on neutrophil chemotaxis, phagocytosis and microbial killing. Significant changes in body weight, triglycerides and glucose occurred during the diet, and most patients exhibited urinary ketosis. The diet was associated with increased blastogenesis in unstimulated cultures and in varicella and candida antigen-stimulated cultures, but blastogenesis was unchanged for phytohemagglutinin, concanavalin A, SK-SD and histoplasma. In assays of serum effects on neutrophil function, patients with urinary ketosis had depression of chemotaxis and microbial killing but not phagocytosis when compared to baseline or nonketotic patients. This study indicates that long-term caloric restriction is associated with significant effects on in vitro lymphocyte stimulation and with significant serum effects on normal neutrophil function.

Protection against acute lethal viral infections with the native steroid dehydroepiandrosterone (DHEA)

A significant protective effect of a native adrenal steroid, dehydroepiandrosterone (DHEA), was demonstrated in studies of two lethal viral infection models in mice: systemic coxsackievirus B4 and herpes simplex type 2 encephalitis. The steroid was active either by long-term feeding or by a single subcutaneous injection. A closely related steroid, etiocholanolone, was not protective in these models. Histopathological analysis, leukocyte counts, and numbers of spleen antibody forming cells in the coxsackievirus B4 model suggests that DHEA functions by maintaining or potentiating the immune competence of mice otherwise depressed by viral infection. DHEA was not effective in genetically immunodeficient HRS/J hr/hr mice and did not demonstrate antiviral activity in vitro. While the molecular basis for DHEA's effect on the immune system is not known, studies by others suggest that it may counteract the stress related immunosuppressive effects of glucocorticoids stimulated by viral infection. Because DHEA is a native steroid that has been used clinically with minimal side effects, the utility of DHEA in the therapeutic modulation of acute and chronic viral infections including the acquired immune deficiency syndrome deserves intensive study.

Coxsackievirus group B replication in cultured fetal baboon aortic smooth muscle cells

All six coxsackievirus B (CVB) serotypes replicated to various extents in fetal baboon aortic smooth muscle cells (SMC) in culture. CVB3 and CVB4 replicated to the highest titers and induced no cytopathology at the level of light microscopy. Maximum yields of CVB3 were produced between 12 and 24 hr postinoculation. Up to 15% of SMC cells became infected, as determined by immunofluorescence assays with anti-CVB3 antiserum, yet overall cell division in infected cultures did not differ from infected SMC cultures. Electron microscopy of CVB3-inoculated SMC cultures revealed changes in some cells: viruslike particles, secondary lysosomes containing dense bodies, and peripheral nuclear chromatin condensation. CVB3 replicated well in SMC passages up to the eighth, but did not replicate in eleventh-passage cells. Because of the cardiotropic and myotropic potential of this virus and its ability to replicate in aortic SMC with associated ultrastructural alterations, CVB3 (and other CVB) should be further examined as an etiologic agent(s) that could induce atherosclerosis.

Susceptibility of endothelial cells derived from different blood vessels to common viruses

We examined whether endothelial cells derived from different blood vessels vary in their susceptibility to viral infection. Five common viral pathogens of humans (herpes simplex 1, measles, mumps, echo 9, and coxsackie B4 viruses) were evaluated for growth in endothelial cells derived from bovine fetal pulmonary artery, thoracic aorta, and vena cava. All five viruses replicated in each type of endothelial cell. There were apparent differences in the quantities of measles and mumps viruses produced in pulmonary artery endothelium compared with thoracic aorta and vena cava when endothelial cells were obtained from different animals. However, when pulmonary artery endothelial cells were compared with vena cava cells from the same animal, growth of each virus was similar in the two cell types. Four of the viruses replicated in the various endothelial cells without producing appreciable changes in cell morphology. These results indicate that endothelial cells from different blood vessels are equally susceptible to the human viruses evaluated, and that viral replication can occur without major alterations in cell morphology. Endothelial cells could serve as permissive cells permitting viruses to leave the circulation and initiate infection in adjacent tissues, including subendothelial smooth muscle cells.

An uncommon systemic arteritis--a case report

A 26-year-old male shortly after an acute respiratory disease was affected by a thrombophlebitis of the left leg. After a few days he had two syncopal attacks. Later on, a myocardial ischemia was diagnosed. Subsequently the patient began to complain of a bilateral claudication of the calves; after an attack of fever, the ischemia of the lower limbs worsened with recurring pain at rest. At the same time, in absence of any symptom, a myocardial ischemia occurred again and the presence of a thrombus was observed in the right atrium. After surgical removal of it, the ischemic troubles of the lower limbs once again began to worsen with the occurrence of bilateral gangrene of the feet. An amputation of both the legs was promptly performed at the level of the thighs. The histological examination of the arteries of the amputated legs showed segmental arteritis with partially recanalized thrombi of the popliteal, left femoral and tibioperoneal arteries. In the meantime, the titres for Coxsackie virus B2 and B6 were found slightly increased. One month later, the left radial pulse disappeared for a few days. The histopathological findings may relate this arteritis to a form of Buerger's disease even if a systemic thromboangiitis obliterans is not commonly accepted. In case that the acute respiratory infection represented the true onset of the sickness, it seems conceivable that the hypothesis of a viral infection gave raise to arteritis with morphological features recalling those of Buerger's disease.

Characterization and myocarditic capabilities of coxsackievirus B3 variants in selected mouse strains

Two variants of coxsackievirus B3 (CVB3) were compared with the original myocarditic parent variant (CVB3m) for myocarditic properties in several strains of mice. The ts1R variant produced little to no myocarditis in any of the nine mouse strains examined. The ts10R variant and CVB3m could be differentiated on the basis of the extent of myocarditis induced in mice of selected H-2b and H-2k haplotypes and in the female versus the male responses of two other inbred strains. Virus quantities recovered from the hearts of myocarditic mice did not correlate with the extent of disease. The three variants could not be differentiated on the basis of: (i) rate and extent of adsorption to heart tissue homogenates, (ii) kinetic neutralization rates with antiserum directed against CVB3m, (iii) 125I labeling of surface regions of polypeptides on purified particles, or (iv) rates of heat inactivation of infectivity at 50 degrees C. These data suggest that differences in pathogenicity cannot be attributed to major alterations in capsid polypeptides. Oligonucleotide fingerprint maps of T1 RNase digests of the genomes of purified particles of the three CVB3 variants showed distinct differences. Thus, the extent of myocarditis induced by CVB3 variants in a mouse model is affected by some subtle expression of the genome, presumably not involving capsid polypeptides, as well as by the haplotype and sex of a given mouse host species.

Impaired function of immune reactivity to Listeria monocytogenes in diet-fed mice

Mice fed a diet high in cholesterol, lard, and sucrose were shown to exhibit an impairment of specific immunity to Listeria monocytogenes. Whereas titers of L. monocytogenes in livers of normal mice decreased rapidly after 6 days of infection, L. monocytogenes persisted in livers of diet-fed mice. Adoptive transfer experiments indicated that L. monocytogenes-immune spleen cells are generated in diet-fed mice. However, the function of immune spleen cells from donors of either nutritional status was impaired in diet-fed recipients. The results indicate that the site(s) of impairment of specific immunity to L. monocytogenes in diet-fed mice occurs at a stage beyond the generation of immune T-cells.

Dietary hepatic cholesterol elevation: effects on coxsackievirus B infection and inflammation

Mice made hypercholesterolemic (HC) by diet are highly susceptible to coxsackievirus (CV) B5, whereas normal adult animals remain resistant. In attempting to define those dietary-induced physiological changes which contribute to altered resistance, a strong association between accumulation of intrahepatic cholesterol and increased CV B5-induced mortality was demonstrated, with maximum susceptibility to CV coinciding with a 2.5-fold increase in the ratio of hepatic cholesterol to protein. This metabolic imbalance was associated with a lower clearance rate of CV from the blood and liver of C57BL/6 mice, although virus-specific neutralizing antibody production was unaltered. In addition to CV, HC mice were more susceptible to an intravenous inoculation of Listeria monocytogenes in comparison to controls. The macrophage stimulant Corynebacterium parvum failed to increase resistance of HC mice to a high dose of CV B4 and L. monocytogenes and failed to induce the hepatomegaly, splenomegaly, and cellular infiltrate seen in the liver and spleen of normal animals. Furthermore, the peritoneal monocytic infiltrate induced by thioglycolate in normal animals was absent in HC mice. Results from these experiments suggest that decreased resistance to CV in the HC host is attributed to a defect in the nonspecific immune responses of macrophages and monocytes which are of primary importance in resistance to this virus and other infectious agents.

Rapid evolution of RNA genomes

RNA viruses show high mutation frequencies partly because of a lack of the proofreading enzymes that assure fidelity of DNA replication. This high mutation frequency is coupled with high rates of replication reflected in rates of RNA genome evolution which can be more than a millionfold greater than the rates of the DNA chromosome evolution of their hosts. There are some disease implications for the DNA-based biosphere of this rapidly evolving RNA biosphere.

Resistance to bacterial and parasitic infections in the nutritionally compromised host

Over the past few years the relationships and interactions of diet, disease, and immunology are becoming better defined with the development and understanding of host defenses. Nutritional state, immunity, and disease all influence each other in the hospitalized patient, the elderly, and the young. Disease can alter nutritional needs and immune responses to antigens. The roles of both dietary excesses and deficiencies on cellular, secretory, and humoral immune responses are related to diseases and disease incidence in humans and experimental animals. Malnutrition alters incidence and severity of fungal, bacterial, viral, and parasitic pathogens. The mechanisms of altered disease resistance in nutritionally stressed animal models occurs via changes in the lymphoreticular endothelial system. The effects of common nutritional deficiencies, low protein, and low carbohydrate diets on antibody production, macrophage function, secretory IgA synthesis, and T-cell functions. Nutritional supplementation can increase lymphocyte function and decrease growth of some pathogens and tumors. Alternatively, obesity and high fat have roles in infectious disease and immunity.

Suppression of aortic elastic tissue autofluorescence for the detection of viral antigen

Suppression of aortic elastic tissue autofluorescence was achieved by employing a modification of Verhoeff's elastic tissue staining procedure. Consquently, coxsackievirus B antigen present in the aortic media was detected by conventional fluorescent antibody staining.