Increased virulence of a human enterovirus (coxsackievirus B3) in selenium-deficient mice

Could Selenium Supplementation Prevent COVID-19? A Comprehensive Review of Available Studies

The purpose of this review is to systematically examine the scientific evidence investigating selenium's relationship with COVID-19, aiming to support, or refute, the growing hypothesis that supplementation could prevent COVID-19 etiopathogenesis. In fact, immediately after the beginning of the COVID-19 pandemic, several speculative reviews suggested that selenium supplementation in the general population could act as a silver bullet to limit or even prevent the disease. Instead, a deep reading of the scientific reports on selenium and COVID-19 that are available to date supports neither the specific role of selenium in COVID-19 severity, nor the role of its supplementation in the prevention disease onset, nor its etiology.

Selenium status and immunity

Selenium is found at the active centre of twenty-five selenoproteins which have a variety of roles, including the well-characterised function of antioxidant defense, but it also is claimed to be involved in the immune system. However, due to limited and conflicting data for different parameters of immune function, intakes of selenium that have an influence on immune function are uncertain. This review covers the relationship between selenium and immune function in man, focusing on the highest level of evidence, namely that generated by randomised controlled trials (RCT), in which the effect of selective administration of selenium, in foods or a supplement, on immune function was assessed. A total of nine RCT were identified from a systematic search of the literature, and some of these trials reported effects on T and natural killer cells, which were dependent on the dose and form of selenium administered, but little effect of selenium on humoral immunity. There is clearly a need to undertake dose-response analysis of cellular immunity data in order to derive quantitative relationships between selenium intake and measures of immune function. Overall, limited effects on immunity emerged from experimental studies in human subjects, though additional investigation on the potential influence of selenium status on cellular immunity appears to be warranted.

Selenium and immune function: a systematic review and meta-analysis of experimental human studies

BACKGROUND

Selenium is an essential trace element with both beneficial and detrimental effects on health depending on dose and chemical form. Currently, there is debate on recommendations for selenium supplementation as a public health measure to improve immune function and reduce infectious disease susceptibility.

OBJECTIVES

We performed a systematic review and meta-analysis of experimental studies assessing the effect of selenium supplementation on immunity-related outcomes in healthy people.

METHODS

We undertook a search of published and unpublished studies in literature databases such as PubMed/MEDLINE, Embase, and clinicaltrials.gov up to 17 October, 2022, and performed a meta-analysis comparing the effects on immunity-related outcomes between Se-supplemented versus control arms. Whenever possible we assessed the nonlinear relation using a dose-response approach.

RESULTS

9 trials were included, 5 in North America, and 4 in Europe, with a duration between 8 and 48 weeks and supplementation of both inorganic and organic selenium forms. Selenium supplementation did not substantially affect immunoglobulin or white blood cell concentrations, and the dose-response meta-analysis indicated that an increase in plasma selenium concentrations above 100 μg/L did not further increase IgA levels nor T cells. An inverted U-shaped relation emerged for NK cell count, with a lower number of these cells both below and above 120 μg/L. The only beneficial effect of selenium supplementation was the increased activity for NK lysis, but the available data did not permit dose-response analysis. Cytokine levels were substantially unaffected by selenium supplementation.

CONCLUSIONS

Although some of the data suggested beneficial effects of selenium supplementation on immune function, the overall picture appears to be inconsistent and heterogeneous due to differences in trial duration and interventions, plus evidence of null and even detrimental effects. Overall, the evidence that we extracted from the literature in this systematic review does not support the need to supplement selenium beyond the recommended dietary intake to obtain beneficial effects on immune function. This trial was registered at PROSPERO (CRD42022312280).

Exploration of PDCoV-induced apoptosis through mitochondrial dynamics imbalance and the antagonistic effect of SeNPs

Porcine Deltacoronavirus (PDCoV), an enveloped positive-strand RNA virus that causes respiratory and gastrointestinal diseases, is widely spread worldwide, but there is no effective drug or vaccine against it. This study investigated the optimal Selenium Nano-Particles (SeNPs) addition concentration (2 - 10 μg/mL) and the mechanism of PDCoV effect on ST (Swine Testis) cell apoptosis, the antagonistic effect of SeNPs on PDCoV. The results indicated that 4 μg/mL SeNPs significantly decreased PDCoV replication on ST cells. SeNPs relieved PDCoV-induced mitochondrial division and antagonized PDCoV-induced apoptosis via decreasing Cyt C release and Caspase 9 and Caspase 3 activation. The above results provided an idea and experimental basis associated with anti-PDCoV drug development and clinical use.

Inhibition of selenoprotein synthesis by Zika virus may contribute to congenital Zika syndrome and microcephaly by mimicking SELENOP knockout and the genetic disease PCCA

Selenium status plays a major role in health impacts of various RNA viruses. We previously reported potential antisense interactions between viral mRNAs and host mRNAs encoding isoforms of the antioxidant selenoprotein thioredoxin reductase (TXNRD). Here, we examine possible targeting of selenoprotein mRNAs by Zika virus (ZIKV), because one of the most devastating outcomes of ZIKV infection in neonates, microcephaly, is a key manifestation of Progressive Cerebello-Cerebral Atrophy (PCCA), a genetic disease of impaired selenoprotein synthesis. Potential antisense matches between ZIKV and human selenoprotein mRNAs were identified computationally, the strongest being against human TXNRD1 and selenoprotein P (SELENOP), a selenium carrier protein essential for delivery of selenium to the brain. Computationally, ZIKV has regions of extensive (~30bp) and stable (ΔE < -50kcal/mol) antisense interactions with both TXNRD1 and SELENOP mRNAs. The core ZIKV/SELENOP hybridization was experimentally confirmed at the DNA level by gel shift assay using synthetic oligonucleotides. In HEK293T cells, using Western blot probes for SELENOP and TXNRD1, ZIKV infection knocked down SELENOP protein expression almost completely, by 99% (p<0.005), and TXNRD1 by ~90% (p<0.05). In contrast, by RT-qPCR, there was no evidence of significant changes in SELENOP and TXNRD1 mRNA levels after ZIKV infection, suggesting that their knockdown at the protein level is not primarily a result of mRNA degradation. These results suggest that knockdown of SELENOP and TXNRD1 by ZIKV in fetal brain, possibly antisense-mediated, could mimic SELENOP knockout, thereby contributing to neuronal cell death and symptoms similar to the genetic disease PCCA, including brain atrophy and microcephaly.

Role of Selenium in Viral Infections with a Major Focus on SARS-CoV-2

Viral infections have afflicted human health and despite great advancements in scientific knowledge and technologies, continue to affect our society today. The current coronavirus (COVID-19) pandemic has put a spotlight on the need to review the evidence on the impact of nutritional strategies to maintain a healthy immune system, particularly in instances where there are limited therapeutic treatments. Selenium, an essential trace element in humans, has a long history of lowering the occurrence and severity of viral infections. Much of the benefits derived from selenium are due to its incorporation into selenocysteine, an important component of proteins known as selenoproteins. Viral infections are associated with an increase in reactive oxygen species and may result in oxidative stress. Studies suggest that selenium deficiency alters immune response and viral infection by increasing oxidative stress and the rate of mutations in the viral genome, leading to an increase in pathogenicity and damage to the host. This review examines viral infections, including the novel SARS-CoV-2, in the context of selenium, in order to inform potential nutritional strategies to maintain a healthy immune system.

The Role of Nutrition in COVID-19 Susceptibility and Severity of Disease: A Systematic Review

BACKGROUND

Many nutrients have powerful immunomodulatory actions with the potential to alter susceptibility to coronavirus disease 2019 (COVID-19) infection, progression to symptoms, likelihood of severe disease, and survival.

OBJECTIVE

The aim was to review the latest evidence on how malnutrition across all its forms (under- and overnutrition and micronutrient status) may influence both susceptibility to, and progression of, COVID-19.

METHODS

We synthesized information on 13 nutrition-related components and their potential interactions with COVID-19: overweight, obesity, and diabetes; protein-energy malnutrition; anemia; vitamins A, C, D, and E; PUFAs; iron; selenium; zinc; antioxidants; and nutritional support. For each section we provide: 1) a landscape review of pertinent material; 2) a systematic search of the literature in PubMed and EMBASE databases, including a wide range of preprint servers; and 3) a screen of 6 clinical trial registries. All original research was considered, without restriction to study design, and included if it covered: 1) severe acute respiratory syndrome coronavirus (CoV) 2 (SARS-CoV-2), Middle East respiratory syndrome CoV (MERS-CoV), or SARS-CoV viruses and 2) disease susceptibility or 3) disease progression, and 4) the nutritional component of interest. Searches took place between 16 May and 11 August 2020.

RESULTS

Across the 13 searches, 2732 articles from PubMed and EMBASE, 4164 articles from the preprint servers, and 433 trials were returned. In the final narrative synthesis, we include 22 published articles, 38 preprint articles, and 79 trials.

CONCLUSIONS

Currently there is limited evidence that high-dose supplements of micronutrients will either prevent severe disease or speed up recovery. However, results of clinical trials are eagerly awaited. Given the known impacts of all forms of malnutrition on the immune system, public health strategies to reduce micronutrient deficiencies and undernutrition remain of critical importance. Furthermore, there is strong evidence that prevention of obesity and type 2 diabetes will reduce the risk of serious COVID-19 outcomes. This review is registered at PROSPERO as CRD42020186194.

Advances in Research on the Toxicological Effects of Selenium

Selenium is a trace element necessary for the growth of organisms. Moreover, selenium supplementation can improve the immunity and fertility of the body, as well as its ability to resist oxidation, tumors, heavy metals, and pathogenic microorganisms. However, owing to the duality of selenium, excessive selenium supplementation can cause certain toxic effects on the growth and development of the body and may even result in death in severe cases. At present, increasing attention is being paid to the development and utilization of selenium as a micronutrient, but its potential toxicity tends to be neglected. This study systematically reviews recent research on the toxicological effects of selenium, aiming to provide theoretical references for selenium toxicology-related research and theoretical support for the development of selenium-containing drugs, selenium-enriched dietary supplements, and selenium-enriched foods.

G6PD deficiency, redox homeostasis, and viral infections: implications for SARS-CoV-2 (COVID-19)

The COVID-19 pandemic has so far affected more than 45 million people and has caused over 1 million deaths worldwide. Infection with SARS-CoV-2, the pathogenic agent, which is associated with an imbalanced redox status, causes hyperinflammation and a cytokine storm, leading to cell death. Glucose-6-phosphate dehydrogenase (G6PD) deficient individuals may experience a hemolytic crisis after being exposed to oxidants or infection. Individuals with G6PD deficiency are more susceptible to coronavirus infection than individuals with normally functioning G6PD. An altered immune response to viral infections is found in individuals with G6PD deficiency. Evidence indicates that G6PD deficiency is a predisposing factor of COVID-19.

An overview of the immune mechanisms of viral myocarditis

Viral myocarditis has been identified as a major cause of dilated cardiomyopathy (DCM) that can lead to heart failure. Historically, Coxsackieviruses and adenoviruses have been commonly suspected in myocarditis/DCM patients in North America and Europe. However, this notion is changing as other viruses such as Parvovirus B19 and human herpesvirus-6 are increasingly reported as causes of myocarditis in the United States, with the most recent example being the severe acute respiratory syndrome coronavirus 2, causing the Coronavirus Disease-19. The mouse model of Coxsackievirus B3 (CVB3)-induced myocarditis, which may involve mediation of autoimmunity, is routinely used in the study of immune pathogenesis of viral infections as triggers of DCM. In this review, we discuss the immune mechanisms underlying the development of viral myocarditis with an emphasis on autoimmunity in the development of post-infectious myocarditis induced with CVB3.

Selenium, Selenoproteins and Viral Infection

Reactive oxygen species (ROS) are frequently produced during viral infections. Generation of these ROS can be both beneficial and detrimental for many cellular functions. When overwhelming the antioxidant defense system, the excess of ROS induces oxidative stress. Viral infections lead to diseases characterized by a broad spectrum of clinical symptoms, with oxidative stress being one of their hallmarks. In many cases, ROS can, in turn, enhance viral replication leading to an amplification loop. Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation. Among the nutrients implicated in viral infection, selenium (Se) has an important role in antioxidant defense, redox signaling and redox homeostasis. Most of biological activities of selenium is performed through its incorporation as a rare amino acid selenocysteine in the essential family of selenoproteins. Selenium deficiency, which is the main regulator of selenoprotein expression, has been associated with the pathogenicity of several viruses. In addition, several selenoprotein members, including glutathione peroxidases (GPX), thioredoxin reductases (TXNRD) seemed important in different models of viral replication. Finally, the formal identification of viral selenoproteins in the genome of molluscum contagiosum and fowlpox viruses demonstrated the importance of selenoproteins in viral cycle.

On the diverse and opposing effects of nutrition on pathogen virulence

Climate change and anthropogenic activity are currently driving large changes in nutritional availability across ecosystems, with consequences for infectious disease. An increase in host nutrition could lead to more resources for hosts to expend on the immune system or for pathogens to exploit. In this paper, we report a meta-analysis of studies on host-pathogen systems across the tree of life, to examine the impact of host nutritional quality and quantity on pathogen virulence. We did not find broad support across studies for a one-way effect of nutrient availability on pathogen virulence. We thus discuss a hypothesis that there is a balance between the effect of host nutrition on the immune system and on pathogen resources, with the pivot point of the balance differing for vertebrate and invertebrate hosts. Our results suggest that variation in nutrition, caused by natural or anthropogenic factors, can have diverse effects on infectious disease outcomes across species.

Cellular Selenoprotein mRNA Tethering via Antisense Interactions with Ebola and HIV-1 mRNAs May Impact Host Selenium Biochemistry

Regulation of protein expression by non-coding RNAs typically involves effects on mRNA degradation and/or ribosomal translation. The possibility of virus-host mRNA-mRNA antisense tethering interactions (ATI) as a gain-of-function strategy, via the capture of functional RNA motifs, has not been hitherto considered. We present evidence that ATIs may be exploited by certain RNA viruses in order to tether the mRNAs of host selenoproteins, potentially exploiting the proximity of a captured host selenocysteine insertion sequence (SECIS) element to enable the expression of virally-encoded selenoprotein modules, via translation of in-frame UGA stop codons as selenocysteine. Computational analysis predicts thermodynamically stable ATIs between several widely expressed mammalian selenoprotein mRNAs (e.g., isoforms of thioredoxin reductase) and specific Ebola virus mRNAs, and HIV-1 mRNA, which we demonstrate via DNA gel shift assays. The probable functional significance of these ATIs is further supported by the observation that, in both viruses, they are located in close proximity to highly conserved in-frame UGA stop codons at the 3′ end of open reading frames that encode essential viral proteins (the HIV-1 nef protein and the Ebola nucleoprotein). Significantly, in HIV/AIDS patients, an inverse correlation between serum selenium and mortality has been repeatedly documented, and clinical benefits of selenium in the context of multi-micronutrient supplementation have been demonstrated in several well-controlled clinical trials. Hence, in the light of our findings, the possibility of a similar role for selenium in Ebola pathogenesis and treatment merits serious investigation.

Selenium deficiency associated porcine and human cardiomyopathies

Selenium (Se) is a trace element playing an important role in animal and human physiological homeostasis. It is a key component in selenoproteins (SeP) exerting multiple actions on endocrine, immune, inflammatory and reproductive processes. The SeP family of glutathione peroxidases (GSH-Px) inactivates peroxides and thereby maintains physiological muscle function in humans and animals. Animals with high feed conversion efficiency and substantial muscle mass have shown susceptibility to Se deficiency related diseases since nutritional requirements of the organism may not be covered. Mulberry Heart Disease (MHD) in pigs is an important manifestation of Se deficiency often implicating acute heart failure and sudden death without prior clinical signs. Post-mortem findings include hemorrhagic and pale myocardial areas accompanied by fluid accumulation in the pericardial sac and pleural cavity. Challenges in MHD are emerging in various parts of the world. Se is of fundamental importance also to human health. In the 1930s the Se deficiency associated cardiomyopathy named Keshan Disease (KD) was described for the first time in China. Various manifestations, such as cardiogenic shock, enlarged heart, congestive heart failure, and cardiac arrhythmias are common. Multifocal necrosis and fibrous replacement of myocardium are characteristic findings. Pathological findings in MD and KD show striking similarities.

Selenium status alters the immune response and expulsion of adult Heligmosomoides bakeri worms in mice

Heligmosomoides bakeri is a nematode with parasitic development exclusively in the small intestine of infected mice that induces a potent STAT6-dependent Th2 immune response. We previously demonstrated that host protective expulsion of adult H. bakeri worms from a challenge infection was delayed in selenium (Se)-deficient mice. In order to explore mechanisms associated with the delayed expulsion, 3-week-old female BALB/c mice were placed on a torula yeast-based diet with or without 0.2 ppm Se, and after 5 weeks, they were inoculated with H. bakeri infective third-stage larvae (L3s). Two weeks after inoculation, the mice were treated with an anthelmintic and then rested, reinoculated with L3s, and evaluated at various times after reinoculation. Analysis of gene expression in parasite-induced cysts and surrounding tissue isolated from the intestine of infected mice showed that the local-tissue Th2 response was decreased in Se-deficient mice compared to that in Se-adequate mice. In addition, adult worms recovered from Se-deficient mice had higher ATP levels than worms from Se-adequate mice, indicating greater metabolic activity in the face of a suboptimal Se-dependent local immune response. Notably, the process of worm expulsion was restored within 2 to 4 days after feeding a Se-adequate diet to Se-deficient mice. Expulsion was associated with an increased local expression of Th2-associated genes in the small intestine, intestinal glutathione peroxidase activity, secreted Relm-β protein, anti-H. bakeri IgG1 production, and reduced worm fecundity and ATP-dependent metabolic activity.

Selenistasis: epistatic effects of selenium on cardiovascular phenotype

Although selenium metabolism is intricately linked to cardiovascular biology and function, and deficiency of selenium is associated with cardiac pathology, utilization of selenium in the prevention and treatment of cardiovascular disease remains an elusive goal. From a reductionist standpoint, the major function of selenium in vivo is antioxidant defense via its incorporation as selenocysteine into enzyme families such as glutathione peroxidases and thioredoxin reductases. In addition, selenium compounds are heterogeneous and have complex metabolic fates resulting in effects that are not entirely dependent on selenoprotein expression. This complex biology of selenium in vivo may underlie the fact that beneficial effects of selenium supplementation demonstrated in preclinical studies using models of oxidant stress-induced cardiovascular dysfunction, such as ischemia-reperfusion injury and myocardial infarction, have not been consistently observed in clinical trials. In fact, recent studies have yielded data that suggest that unselective supplementation of selenium may, indeed, be harmful. Interesting biologic actions of selenium are its simultaneous effects on redox balance and methylation status, a combination that may influence gene expression. These combined actions may explain some of the biphasic effects seen with low and high doses of selenium, the potentially harmful effects seen in normal individuals, and the beneficial effects noted in preclinical studies of disease. Given the complexity of selenium biology, systems biology approaches may be necessary to reach the goal of optimization of selenium status to promote health and prevent disease.

Both selenium deficiency and modest selenium supplementation lead to myocardial fibrosis in mice via effects on redox-methylation balance

SCOPE

Selenium has complex effects in vivo on multiple homeostatic mechanisms such as redox balance, methylation balance, and epigenesis, via its interaction with the methionine-homocysteine cycle. In this study, we examined the hypothesis that selenium status would modulate both redox and methylation balance and thereby modulate myocardial structure and function.

METHODS AND RESULTS

We examined the effects of selenium-deficient (<0.025 mg/kg), control (0.15 mg/kg), and selenium-supplemented (0.5 mg/kg) diets on myocardial histology, biochemistry and function in adult C57/BL6 mice. Selenium deficiency led to reactive myocardial fibrosis and systolic dysfunction accompanied by increased myocardial oxidant stress. Selenium supplementation significantly reduced methylation potential, DNA methyltransferase activity and DNA methylation. In mice fed the supplemented diet, inspite of lower oxidant stress, myocardial matrix gene expression was significantly altered resulting in reactive myocardial fibrosis and diastolic dysfunction in the absence of myocardial hypertrophy.

CONCLUSION

Our results indicate that both selenium deficiency and modest selenium supplementation leads to a similar phenotype of abnormal myocardial matrix remodeling and dysfunction in the normal heart. The crucial role selenium plays in maintaining the balance between redox and methylation pathways needs to be taken into account while optimizing selenium status for prevention and treatment of heart failure.

Human immunodeficiency virus & cardiovascular risk

Highly active antiretroviral therapy (HAART) significantly changed the prevalence of the cardiovascular manifestations of human immunodeficiency virus (HIV)/AIDS. In developed countries, a 30 per cent reduction in the prevalence of cardiomyopathy and pericardial effusion was observed, possibly related to a reduction of opportunistic infections and myocarditis. In developing countries, however, where the availablity of HAART is limited, and the pathogenic impact of nutritional factors is significant, a 32 per cent increase was seen in the prevalence of cardiomyopathy and related high mortality rate from congestive heart failure. Also, some HAART regimens in developed countries, especially those including protease inhibitors, may cause, in a high proportion of HIV-infected patients, a lipodystrophy syndrome that is associated with an increased risk of cardiovascular events related to a process of accelerated atherosclerosis. Careful cardiac screening is warranted for patients who are being evaluated for, or who are receiving HAART regimens, particularly for those with known underlying cardiovascular risk factors, according to the most recent clinical guidelines.

Arsenic trioxide influences viral replication in target organs of coxsackievirus B3-infected mice

New antiviral agents are urgently needed. Based on in vitro studies, arsenic trioxide (As₂O₃) seems to affect viral replication, although this has been studied only marginally in vivo. In this study the replication of coxsackievirus B3 (CVB3) was studied in Balb/c mice administered 1 mg As₂O₃/kg bw once daily during 7 days of infection and in Vero cells exposed for 3 or 5 days to 0.4, 2 or 4 μM As₂O₃. Viral RNA was measured by reverse transcription PCR (RT-PCR) (in vitro and in vivo) and arsenic concentration was measured by inductively coupled plasma-mass spectrometry (ICP-MS) (in vivo). In vivo, As₂O₃ decreased viral RNA in the brain on days 3 (by 81%; p < 0.05) and 7 (by 97%; p < 0.01) and in the pancreas on day 7 (by 75%; p < 0.05), two of the target organs of this infection. The results were confirmed in vitro, where As₂O₃ dose-dependently reduced viral RNA, with the effect being more pronounced in the surrounding culture medium than inside the infected cells, indicating an impaired virion release. Thus, As₂O₃ reduced CVB3 replication both in vitro and in vivo, indicating that As₂O₃ is a viable option in the pursuit of new therapeutic agents against viral infections.

Regulation and function of selenoproteins in human disease

Selenoproteins are proteins containing selenium in the form of the 21st amino acid, selenocysteine. Members of this protein family have many diverse functions, but their synthesis is dependent on a common set of cofactors and on dietary selenium. Although the functions of many selenoproteins are unknown, several disorders involving changes in selenoprotein structure, activity or expression have been reported. Selenium deficiency and mutations or polymorphisms in selenoprotein genes and synthesis cofactors are implicated in a variety of diseases, including muscle and cardiovascular disorders, immune dysfunction, cancer, neurological disorders and endocrine function. Members of this unusual family of proteins have roles in a variety of cell processes and diseases.

Induced susceptibility of host is associated with an impaired antioxidant system following infection with Cryptosporidium parvum in Se-deficient mice

BACKGROUND

Susceptibility or resistance to infection with Cryptosporidium parvum (C.parvum) correlates with Selenium (Se) deficiency in response to infection. Both adult Se-adequate and Se-deficient mouse models of cryptosporidiosis were used to study the cell-mediated immune response during the course of C. parvum infection.

METHODOLOGY/PRINCIPAL FINDINGS

Blood samples from mouse models were used for Se status. The concentration of MDA, SOD, GPx and CAT in blood has revealed that lower Se level exist in Se-deficient mice. Mesenteric lymph node (MLN) lymphocytes from both mouse models were proliferated after ex vivo re-stimulation with C. parvum sporozoite antigen. The study of the cytokine profiles from the supernatant of proliferated MLN cells revealed that Se-adequate mice produced higher levels of Th1 (IFN-gamma and IL-2) and moderate amounts of Th2 (IL-4) cytokines throughout the course of infection. Whereas, MLN cells from Se-deficient mice produced lower levels of IFN-gamma, IL-2 and IL-4 cytokines. The counts of total white cell and CD3, CD4, CD8 cell in Se-adequate were higher than that in Se-deficient mice.

SIGNIFICANCE

These results suggest that Cell immunity is affected by Se status after infection with C. parvum from kinetic changes of different white cells and cytokine. In conclusion, induced susceptibility of host is associated with an impaired antioxidant system following infection with C. parvum in C57BL/6 Selenium deficient mice.

Viral RNA kinetics is associated with changes in trace elements in target organs of Coxsackie virus B3 infection

Trace elements are pivotal for the host defense, as well as potentially important for viral replication and virulence. Studies of sequential changes in viral replication in target organs of infection are sparse and a possible association with changes in specific trace elements is unknown. In this study Balb/c mice were infected with Coxsackie virus B3 (CVB3). Results indicated that sequential changes in viral replication (RT-PCR) were related to changes in trace element (arsenic, copper, iron, selenium and zinc) concentrations (as determined by ICP-MS) on days 3, 5 and 7 of the infection in serum, heart, lung, liver, pancreas, kidney, spleen, intestine and brain. After an initial viral peak on day 3, viral load drastically decreased in all organs, i.e. by >99% (serum), 97% (lung), 98% (liver), 60% (pancreas), 95% (kidney) and 93% (spleen), except in the heart, intestine and brain in which viral load increased after day 3. Selenium decreased in all organs except the heart while arsenic decreased in all organs except the kidney, spleen and brain. Moreover, selenium was negatively correlated to viral load in serum, liver, pancreas and intestine. To conclude, these findings give evidence that trace elements are directly involved in the replication of CVB3.

Malnutrition and infection: an update

The original Scrimshaw, Taylor and Gordon conceptual framework for the interaction of nutrition and infection has well served the scientific community for almost half a century. At its core is the notion of synergistic (mutually reinforcing) and antagonistic (mutually nullifying) influences of the malnourished state on infectious conditions and vice versa. Research on a series of advancing fronts, however, has allowed the incorporation of both relevant public health issues (parasitosis, emerging infectious diseases, obesity and overweight, etc.) and advancing science (molecular immunology, oxidation biology, multiple micronutrient deficiencies, etc.). The present review is an interpretative update on close to 50 years of demographic and epidemiological evolution in the field of human nutrition and the implications for the interaction in the context of microbiological and immunological developments on the infectious side of the dialectic.

Tissue uptake of mercury is changed during the course of a common viral infection in mice

Mercury (Hg) has been shown to have immunotoxic effects and to influence the severity of infection. However, the impact of infection on the normal Hg homeostasis in different target organs involved in the disease process has not been studied. In this study, Hg was measured through inductively coupled plasma-mass spectrometry (ICP-MS) in the intestine, serum, liver, and brain on days 3, 6, and 9 of coxsackievirus B3 (CVB3) infection in female Balb/c mice. The severity of the infection was assessed from clinical signs of disease and the number of virus particles in infected organs. CVB3 and gene expression of metallothionein 1 (MT1) was measured by reverse transcription-polymerase chain reaction (RT-PCR). Gene expression of MT1 increased and peaked on day 3 in the brain (93%, p<0.01) and liver (19-fold, p<0.01) and on day 6 in the intestine (seven-fold, p<0.01). This peak in MT1 in the liver and brain corresponded to the peak in virus numbers in these tissues. Hg in the intestine and serum tended to decrease on all days of infection. The maximum decrease, in comparison with non-infected mice, occurred in the intestine (78%, p<0.001) on day 9 and in serum (50%, p<0.05) on day 6. However, in the brain, Hg increased by 52% (p<0.05) on day 6. Hg went unchanged in the liver. An infection-induced increase of Hg in the brain but unchanged level in the liver may be due to the peak of virus replication and an associated infection-induced expression of MT1. Moreover, the decrease of Hg in serum and the intestine but a concomitant intestinal increase in MT1 on day 6 may reflect a flux and increased retention of Hg to infected organs such as the brain. The pathophysiological interpretation of these preliminary findings requires further research.

Gastrointestinal uptake of trace elements are changed during the course of a common human viral (Coxsackievirus B3) infection in mice

Most infectious diseases are accompanied by a change in levels of several trace elements in the blood. However, it is not known whether changes in the gastrointestinal uptake of trace elements contribute to this event. Coxsackievirus B3 (CVB3), adapted to Balb/c mice, was used to study whether infection induces gene expression of metallothionein (MT1) and divalent-metal transporter 1 (DMT1) in the intestine and liver and hepcidin in the liver, as well as whether trace elements in these tissues are changed accordingly. Quantitative expression of CVB3, MT1, DMT1 and hepcidin was measured by real-time RT-PCR and six trace elements by ICP-MS on days 3, 6 and 9 of the infection. The copper/zinc (Cu/Zn) ratio in serum increased as a response to the infection. High concentrations of virus were found in the intestine and liver on day 3 and in the intestine on day 6. MT1 in the intestine and liver increased on days 3 and 6. The increase of MT1 in the liver correlated positively with Cu and Zn. Hepcidin in the liver showed a non-significant increase on days 3 and 6 of the infection, whereas DMT1 in the intestine decreased on day 9. Accordingly, iron (Fe) in the liver increased progressively during the disease, whereas in the intestine DMT1 was negatively correlated to Fe. Arsenic (As), cadmium (Cd) and mercury (Hg) were found to decrease to various degrees in the intestine, serum and liver. Thus, enteroviral infections, and possibly many other infections, may cause a change in the gastrointestinal uptake of both non-essential and essential trace elements.

The immune response to herpes simplex virus encephalitis in mice is modulated by dietary vitamin E

Herpes simplex virus encephalitis (HSE) is the most common fatal sporadic encephalitis in humans. HSE is primarily caused by herpes simplex virus (HSV)-1 infection of the brain. HSE results in increased levels of oxidative stress, including the production of reactive oxygen species, free radicals, and neuroinflammation. The most biologically active form of vitamin E (VE) is alpha-tocopherol (alpha-TOC). In cellular membranes, alpha-TOC prevents lipid peroxidation by scavenging free radicals and functioning as an antioxidant. Supplementation with VE has been shown to decrease immunosenescence, improve immune function, and may be neuroprotective. To determine how VE deficiency and VE supplementation would alter the pathogenesis of HSE, we placed weanling male BALB/cByJ mice on VE-deficient (VE-D), VE-adequate (VE-A), or 10x VE-supplemented diets for 4 wk, and then infected the mice intranasally with HSV-1. VE-D mice had more severe symptoms of encephalitis than VE-A mice, including weight loss, keratitis, hunched posture, and morbidity. VE-D mice had increased cytokine and chemokine expression in the brain and increased viral titers. In contrast, VE supplementation failed to decrease cytokine production and had no effect on viral titer. We demonstrated that adequate levels of VE are important in limiting HSE pathology and that 10x supplementation does not enhance protection.

Nutrition-based health in animal production

Events such as BSE, foot and mouth disease and avian influenza illustrate the importance of animal health on a global basis. The only practical solution to deal with such problems has usually been mass culling of millions of animals at great effort and expense. Serious consideration needs to be given to nutrition as a practical solution for health maintenance and disease avoidance of animals raised for food. Health or disease derives from a triad of interacting factors; diet–disease agent, diet–host and disease agent–host. Various nutrients and other bioactive feed ingredients, nutricines, directly influence health by inhibiting growth of pathogens or by modulating pathogen virulence. It is possible to transform plant-based feed ingredients to produce vaccines against important diseases and these could be fed directly to animals. Nutrients and nutricines contribute to three major factors important in the diet–host interaction; maintenance of gastrointestinal integrity, support of the immune system and the modulation of oxidative stress. Nutrition-based health is the next challenge in modern animal production and will be important to maintain economic viability and also to satisfy consumer demands in terms of food quality, safety and price. This must be accomplished largely through nutritional strategies making optimum use of both nutrients and nutricines.

Coxsackievirus B3 infection affects metal-binding/transporting proteins and trace elements in the pancreas in mice

OBJECTIVE

The trigger of juvenile diabetes has been suggested to be an interaction between a virus and trace elements, where enteroviruses, including coxsackievirus B3 (CVB3), have been discussed as potential initiators. The aim of this study was to investigate the effects in the pancreas on gene expressions of metallothionein 1 (MT1), divalent metal transporter 1 (DMT1), and zinc transporter 5 (ZnT-5) and concomitant changes in iron (Fe), copper (Cu), and zinc (Zn) in serum and pancreas of Balb/c mice on days 3, 6, and 9 of CVB3 infection.

METHODS

Trace elements were measured through inductively coupled plasma-mass spectrometry, and CVB3, MT1, DMT1, and ZnT-5 were measured by reverse transcription-polymerase chain reaction.

RESULTS

Virus was found in the pancreas on all days, with a peak on day 3. Infection tended to increase Fe in both serum and the pancreas. The Cu/Zn ratio in the pancreas increased early in the infection because of a great decrease in Zn. In serum, the Cu/Zn ratio was not increased until day 9 of the disease. In the pancreas, MT1 decreased, whereas DMT1 tended to increase on day 6, and ZnT-5 increased progressively during the course of the disease.

CONCLUSIONS

Virus-induced changes in trace elements, MT1, DMT1, and ZnT-5 in the pancreas may reflect early stages of the development of pancreatitis and prestages of diabetic disease.

Interactions among infections, nutrients and xenobiotics

During recent years there have been several incidents in which symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Furthermore, outbreaks of infections in food-producing animals have attracted major attention regarding the safety of consumers, e.g., Bovine Spongiform Encephalitis (BSE) and influenza in chicken. As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and associated complications. Moreover, during ongoing infection, xenobiotic uptake and distribution are often changed resulting in increased toxic insult to the host. The interactions among infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology as well as in food-borne diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects among microorganisms, nutrients, and xenobiotics will have to be considered. Otherwise, such effects may gradually change the disease panorama in society.

Virus induces metal-binding proteins and changed trace element balance in the brain during the course of a common human infection (coxsackievirus B3) in mice

Autopsy of the brain has shown a change in trace element balance in some virus-infected individuals, but it is not known whether this event was a result of the infection. In the present study coxsackievirus B3 (CVB3) adapted to Balb/c mice was used to study whether infection induces gene expression of the metal-binding/transporting proteins metallothionein (MT1 and MT3) and divalent-metal transporter 1 (DMT1) and whether it changes the balance of trace elements in the brain. Virus and MT1, MT3, and DMT1 were quantitatively measured by RT-PCR on days 3, 6 and 9 of the infection. Trace elements (13) were measured in serum and the brain by ICP-MS. High numbers of virus were found in the brain on days 3 and 6, but virus counts were decreased and present only in 50% of the mice on day 9. Gene expression of MT1 tended to increase on all days, whereas that of MT3 only showed a minor and not significant increase on day 3. No clear effect was observed in the expression of DMT1. The increase of MT3 was correlated to the brain concentration of Cu. The Cu/Zn ratio in serum increased as a response to the infection. There was a similar decrease in Cd in serum and the brain. On day 6 of the infection, Hg increased in the brain (p<0.05) and was positively correlated to a concomitant decrease (p<0.05) in serum. Virus numbers in the brain were on day 6 positively correlated (p<0.05) to As concentrations. Enteroviral infections may therefore be an underlying factor regarding the changes in essential as well as potentially toxic trace elements in the brain.

Undernutrition can affect the invading microorganism

Undernutrition or malnutrition adversely affects host defenses against many invading microorganisms, thereby increasing the severity of infection. Studies of RNA viruses (e.g., coxsackievirus B and influenzavirus) have shown that selenium or vitamin E deficiency in mice increases disease severity and results in stable genomic changes in the virus that increase virulence. Changes in H3N2 influenzavirus were predominantly in the ordinarily stable M1 matrix protein. Whether this represents selection of already-existing variants or direct effects on viral RNA is unclear. Related questions include whether undernutrition in persons who acquire infection with influenzavirus H5N1 could promote genomic changes during infection that result in greater virulence and higher case-fatality rates, and whether undernutrition could help create the multiple mutations needed to instigate human-to-human transmission. These possibilities emphasize the importance of alleviating world poverty and malnutrition. In addition, these findings suggest that the neglected area of undernutrition affecting invading microorganisms merits intensive investigation in humans and experimental models.

Selenium in global food systems

Food systems need to produce enough of the essential trace element Se to provide regular adult intakes of at least 40 μg/d to support the maximal expression of the Se enzymes, and perhaps as much as 300 μg/d to reduce risks of cancer. Deprivation of Se is associated with impairments in antioxidant protection, redox regulation and energy production as consequences of suboptimal expression of one or more of the Se-containing enzymes. These impairments may not cause deficiency signs in the classical sense, but instead contribute to health problems caused by physiological and environmental oxidative stresses and infections. At the same time, supranutritional intakes of Se, i.e. intakes greater than those required for selenocysteine enzyme expression, appear to reduce cancer risk. The lower, nutritional, level is greater than the typical intakes of many people in several parts of the world, and few populations have intakes approaching the latter, supranutritional, level. Accordingly, low Se status is likely to contribute to morbidity and mortality due to infectious as well as chronic diseases, and increasing Se intakes in all parts of the world can be expected to reduce cancer rates.

Sequential trace element changes in serum and blood during a common viral infection in mice

When trace elements are used as diagnostic tools during disease, it is important to know whether the balance is changed in free or bound elements. Although acute infections are associated with changed trace element balance in serum/plasma, it is not known whether changes occur concomitantly in serum and blood. In the present study the human coxsackievirus B3 (CB3), here adapted to Balb/c mice, was used to study whether infection alters the normal physiological trace element balance in blood and serum. Virus was quantitatively measured in two target organs (pancreas and liver) of this infection by reverse transcription polymerase chain reaction (RT-PCR), showing high concentrations of virus proving ongoing infection. Concentrations of 14 elements were measured in whole blood and serum using inductively coupled plasma mass spectrometry (ICP-MS) on days 3, 6 and 9 of the infection. Free and total thyroxine were measured in serum to prove metabolic changes associated with the infection. The thyroxine decreased, while iron and the Cu/Zn ratio in serum increased as a response to the infection. No clear changes in these elements were observed in blood. Cd and Hg tended to decrease in serum but to increase in blood, indicating accumulation in blood cells. Moreover, Al showed a similar decreasing trend in both serum and blood. A correlation between serum and blood levels was observed at different time points of the disease for 9 of the elements. However, As was the only element indicating correlations between serum and blood during the entire course of the disease.

Coxsackievirus myocarditis: interplay between virus and host in the pathogenesis of heart disease

Coxsackievirus (CVB) infection is a significant cause of myocarditis and dilated cardiomyopathy (DCM). Heart disease may be caused by direct cytopathic effects of the virus, a pathologic immune response to persistent virus, or autoimmunity triggered by the viral infection. CVB interacts with its host at multiple stages during disease development. Signaling through viral receptors may alter the intracellular environment in addition to facilitating virus entry. Viral genetic determinants that encode cardiovirulence have been mapped and may change depending on the nutritional status of the host. Virus persistence is directly associated with pathology, and recent work demonstrates that CVB evolves into a slowly replicating form capable of establishing a low-grade infection in the heart. The innate immune response to CVB has taken on increasing importance because of its role in shaping the development of the adaptive immune response that is responsible for cardiac pathology. Studies of T cell responsiveness and the development of autoimmunity at the molecular level are beginning to clarify the mechanisms through which CVB infection causes inflammatory heart disease.

Arsenic is decreased in target organs during viral infection in mice

Arsenic (As), a potentially toxic trace element, has been shown to influence viral replication and resistance to microbial infection. However, the impact of infection on the normal As status in target organs involved in the disease process has not been studied to date. In the present study, As was measured through inductively coupled plasma mass spectrometry in the plasma, liver, spleen, kidney, heart, pancreas and brain at days 1 and 3 of coxsackievirus B3 infection in female Balb/c mice. The severity of the infection was assessed from clinical signs of disease. The infection changed plasma As in a biphasic pattern with a small increase (n.s.) at day 1 that turned into a decreasing trend (13%, p<0.05) by day 3. In the liver, spleen, heart, pancreas and kidney As was unchanged at day 1 but, at day 3, it had decreased by 71% (p<0.01), 64% (p<0.01), 55% (p<0.01), 63% (p<0.01) and 73% (p<0.01), respectively. In the brain, As went unchanged. The pathophysiological interpretation of these findings requires further research.

A nutritional supplement formula for influenza A (H5N1) infection in humans

By early February 2006, the World Health Organization had reported 165 human cases of H5N1 influenza since December 2003, with 88 fatalities. However, the avian H5N1 influenza virus apparently is not yet efficiently transmitted between humans. Though a near-term possibility of a global H5N1 influenza pandemic remains, currently there is no vaccine or anti-viral drug that is proven to be safe and effective in preventing or treating H5N1 influenza in humans. There is thus a compelling public interest in developing alternative prophylaxis and treatment strategies for H5N1 influenza, which would need to address the complex pathogenesis of H5N1 influenza that is responsible for its apparently unusually high virulence. The authors present here a significant body of medical and scientific evidence to support the prophylactic use of a carefully designed nutritional supplement formulation that may antagonize the major pathogenic processes of H5N1 influenza in humans. Through several independently-mediated mechanisms, the formulations may: (a) degrade H5N1 virulence by directly affecting the virus itself, (b) inhibit H5N1 viral replication by maintaining cellular redox equilibrium in host cells, (c) inhibit H5N1 replication by a blockade of the nuclear-cytoplasmic translocation of the viral ribonucleoproteins and reduced expression of late viral proteins related to the inhibition of protein kinase C activity and its dependent pathways, (d) down-regulate activation and proliferation of proinflammatory cytokines in respiratory epithelial cells and macrophages that are implicated in the pathogenesis of H5N1 influenza, and (e) protect the lungs and other vital organs from virus- and cytokine-induced oxidative stress by supplying and maintaining sufficient levels of exogenous and endogenous antioxidants. Key mediators in these processes include selenium, vitamin E, NAC/glutathione, resveratrol, and quercetin. Taken prophylactically, and throughout the duration and recovery of an H5N1 infection, the nutritional supplement formula may aid humans infected with H5N1 influenza to survive with a reduced likelihood of major complications, and may provide a relatively low-cost strategy for individuals as well as government, public-health, medical, health-insurance, and corporate organizations to prepare more prudently for an H5N1 pandemic. Some evidence also indicates that the supplement formulation may be effective as an adjunctive to H5N1 vaccine and anti-viral treatments, and should be tested as such.

Deficiencies in selenium and/or vitamin E lower the resistance of mice to Heligmosomoides polygyrus infections

Previous studies have shown that deficiencies in selenium (Se) and/or vitamin E (VE) can exacerbate the infectivity and pathogenesis of coxsackievirus B3 and influenza. Both Se and VE play a role in immune function and antioxidant defense. To determine whether these deficiencies would affect the normal course of infection with a metazoan parasite, mice were made deficient in Se and/or VE and inoculated with the gastrointestinal nematode parasite Heligmosomoides polygyrus. Both primary and secondary infections were assessed. Although the course of a primary infection with H. polygyrus was unaffected by diet, diets deficient in Se, VE, and both Se and VE (Se/VE double-deficiency) all caused delayed adult worm expulsion and increased fecundity during a secondary infection; suggesting an impaired intestinal response. H. polygyrus-induced IL-4 levels were diet-independent; but Se/VE double-deficiency blocked the H. polygyrus-induced IL-4 receptor-associated decrease in sodium-dependent glucose absorption in the jejunum that contributes to worm expulsion. In contrast, Se/VE double-deficiency had no effect on the infection-induced, IL-4R-associated increase in epithelial cell permeability that accompanies the infection. These results suggest that both Se and VE are required for specific IL-4-related changes in intestinal physiology that promote host protection against H. polygyrus.

Benign coxsackievirus damages heart muscle in iron-loaded vitamin E-deficient mice

Several oxidative stressors (dietary selenium deficiency, dietary vitamin E deficiency coupled with fish oil feeding, genetic reduction of glutathione peroxidase activity) allow a normally benign coxsackievirus B3 (CVB3/0) to damage heart muscle in host mice. This study investigated whether dietary iron overload, another oxidant stress, would also permit CVB3/0 to exert a cardiopathologic effect in vitamin E-deficient (-VE) mice. Four groups of mice were fed either a -VE or a +VE diet containing either an adequate or an excessive (30x) amount of iron. After 4 weeks of feeding, the mice were inoculated with CVB3/0 and heart damage was assessed at various times postinfection. Mice fed a diet sufficient in VE with excess iron developed heart damage equivalent to mice fed a diet deficient in vitamin E without excess iron. However, severe heart damage occurred in the group fed a diet deficient in VE with excess iron, which was the most pro-oxidative diet. The highest heart viral titers were found in mice fed the -VE/excessive iron diet. However, the extent of heart damage did not always correlate with the formation of TBARS in liver homogenates. Further research is needed to clarify the role of oxidative stress and iron overload in determining the course of viral infection.

Glutathione depletion and cardiomyocyte apoptosis in viral myocarditis

BACKGROUND

The course of viral myocarditis is highly variable. Oxidative stress and Bcl-2 family genes may play a role in its pathogenesis by regulating the amount of cardiomyocyte apoptosis. Apoptosis is difficult to detect and quantify in vivo. Therefore, we set to look for indicators of this potentially preventable form of cell death during various phases of experimental murine coxsackievirus B3 myocarditis.

METHODS

BALB/c mice were infected with the cardiotropic coxsackievirus B3 variant. Glutathione (HPLC), cardiomyocyte apoptosis (TUNEL and caspase-3 cleavage), Bax and Bcl-X(L) mRNA expression (real time RT-PCR), histopathology and viral replication (plaque assay and real time RT-PCR) were measured from day 3 to day 20 after infection.

RESULTS

Infection caused severe myocarditis and led to progressive decrease of plasma glutathione levels. Myocardial mRNA levels of pro-apoptotic Bax and antiapoptotic Bcl-X(L) were significantly increased from day 3 onwards. Bax mRNA and ratio of Bax to Bcl-X(L) correlated with cardiomyocyte apoptosis (r = 0.77, P = < 0.001 and r 0.51, P < 0.01, respectively). Cardiomyocyte apoptosis was highest on day 5, coinciding with a rapid decline in plasma glutathione (r = -0.52, P = 0.003).

CONCLUSIONS

Systemic oxidative stress as indicated by decreased plasma glutathione levels coincides with cardiomyocyte apoptosis in experimental coxsackievirus myocarditis. Decreased plasma glutathione levels and changes in cardiac Bax and Bcl-X(L) mRNA expression identify a phase of myocarditis in which the potentially preventable cardiomyocyte apoptosis is mostly observed.

Ethical consequences for professionals from the globalization of food, nutrition and health

Globalization is the process of increasing interconnections and linkages, within societies and across geography, due to improved communication and expanded world trade. It limits the differentiation wrought by human cultural evolution, and homogenizes health practices, diet and lifestyle. There are both beneficial and adverse consequences of the globalization process. Globalization also presents a challenge to the development of ethics for practice and advocacy by food and nutrition professionals. Among the related terms, 'morals', 'values' and 'ethics', the latter connotes the basic rules of conduct for interactions within society and with the inanimate environment; rules based on recognized principles (ethical principles). The application of these principles is to resolve ethical dilemmas that arise when more than one interest is at play. Recognized ethical principles include autonomy, beneficence, non-maleficence, justice, utility and stewardship. These can be framed in the context of issues that arise during advocacy for material and behavioural changes to improve the nutritional health of populations. Clearly, at the global level, codes of good conduct and the construction of good food governance can be useful in institutionalizing ethical principles in matters of human diets and eating practices. Ethical dilemmas arise in the context of innate diversity among populations (some individuals benefit, whereas others suffer from the same exposures), and due to the polarity of human physiology and metabolism (practices that prevent some diseases will provoke other maladies). Moreover, the autonomy of one individual to exercise independent will in addressing personal health or treatment of the environment may compromise the health of the individual's neighbours. The challenges for the professional in pursuit of ethical advocacy in a globalized era are to learn the fundamentals of ethical principles; to bear in mind a respect for difference and differentiation that continues to exist, and which should exist, among individuals and societies; and to avoid a total homogenization of agriculture and food supplies.

Coxsackievirus B3-resistant mice become susceptible in Se/vitamin E deficiency

The severity of the heart damage caused by a coxsackievirus infection in mice is determined by several factors, including the genotype of the infecting virus as well as the genetic background of the infected host. Earlier work by us showed that the cardiovirulence of a given coxsackievirus genotype could be increased substantially by feeding the host a diet nutritionally deficient in either selenium or vitamin E. Here we report that host genetic background as a determinant of viral infection outcome is superseded by feeding the host a diet nutritionally deficient in both selenium and vitamin E. Mice of the C57Bl/6 strain, normally resistant to coxsackievirus B3-induced myocarditis, become susceptible when fed such a doubly deficient diet. Our results demonstrate the powerful influence of host nutritional status on the course of viral infection compared to other variables traditionally considered to play major roles in determining the extent of virally induced inflammatory heart disease.

Trace element changes in the pancreas during viral infection in mice

INTRODUCTION

The trigger for some cases of juvenile diabetes has been suggested to be an interaction between a virus and various trace elements. Infection with human coxsackievirus B3 (CB3) in the murine model results in viral replication and inflammation in the pancreas.

AIM

To determine how infection affects the trace element balance in the pancreas.

METHODOLOGY

Concentrations of the following trace elements were measured in the serum and pancreas during the early phase (days 1 and 3) of CB3 infection in female Balb/c mice: aluminium, arsenic, cadmium (Cd), calcium (Ca), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), mercury (Hg), selenium, silver, vanadium (V), and zinc (Zn). The trace element concentrations were measured through inductively coupled plasma mass spectrometry. The histopathology was established by hematoxylin-eosin techniques and immunohistochemical staining of both CD4 and CD8 cells of the pancreas.

RESULTS

Infected mice developed expected clinical signs of disease. The only changes at day 1 occurred in the serum, with a pronounced decrease in the Zn concentration and a small increase in the V concentration. At day 3, concentrations of several trace elements, including Cu, Zn, Fe, Ca, V, and Mn, showed pronounced changes in both the serum and the pancreas. Ca, Cu, Mg, Mn, and V, but none of the potentially toxic elements, accumulated in the pancreas. Cu and V concentrations increased in the serum as well.

CONCLUSION

Several trace element changes, preceding the development of pancreatitis, occurred in the pancreas in this viral infection, the exact pathogenic interpretation of which warrants further studies.

Trends in selenium biochemistry

The biochemistry of selenium-containing natural products, including selenoproteins, is reviewed up to May 2002. Particular emphasis is placed on the assimilation of selenium from inorganic and organic selenium sources for selenoprotein synthesis, the catalytic role of selenium in enzymes, and medical implications of an unbalanced selenium supply. The review contains 393 references on key discoveries and recent progress.