Reviewing the effects of food provisioning on wildlife immunity

While urban expansion increasingly encroaches on natural habitats, many wildlife species capitalize on anthropogenic food resources, which have the potential to both positively and negatively influence their responses to infection. Here we examine how food availability and key nutrients have been reported to shape innate and adaptive immunity in wildlife by drawing from field-based studies, as well as captive and food restriction studies with wildlife species. Examples of food provisioning and key nutrients enhancing immune function were seen across the three study type distinctions, as were cases of trace metals and pharmaceuticals impairing the immunity of wildlife species. More generally, food provisioning in field studies tended to increase innate and adaptive responses to certain immune challenges, whereas patterns were less clear in captive studies. Mild food restriction often enhanced, whereas severe food restriction frequently impaired immunity. However, to enable stronger conclusions we stress a need for further research, especially field studies, and highlight the importance of integrating nutritional manipulation, immune challenge, and functional outcomes. Despite current gaps in research on this topic, modern high throughput molecular approaches are increasingly feasible for wildlife studies and offer great opportunities to better understand human influences on wildlife health.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'

Hantavirus infection : Insights into entry, assembly and pathogenesis

Hantaviruses (family Bunyaviridae, genus Hantavirus) are enveloped viruses incorporating a segmented, negative-sense RNA genome. Each hantavirus is carried by its specific host, either a rodent or an insectivore (shrew), in which the infection is asymptomatic and persistent. In humans, hantaviruses cause Hemorrhagic fever with renal syndrome (HFRS) in Eurasia and Hantavirus cardiopulmonary syndrome (HCPS) in the Americas. In Finland, Puumala virus (genus Hantavirus) is the causative agent of NE, a mild form of HFRS. The HFRS-type diseases are often associated with renal failure and proteinuria that might be mechanistically explained by infected kidney tubular cell degeneration in patients. Previously, it has been shown that non-pathogenic hantavirus, Tula virus (TULV), could cause programmed cell death, apoptosis, in cell cultures. This suggested that the infected kidney tubular degeneration could be caused directly by virus replication. In the first paper of this thesis the molecular mechanisms involved in TULV-induced apoptosis was further elucidated. A virus replication-dependent down-regulation of ERK1/2, concomitantly with the induced apoptosis, was identified. In addition, this phenomenon was not restricted to TULV or to non-pathogenic hantaviruses in general since also a pathogenic hantavirus, Seoul virus, could inhibit ERK1/2 activity. Hantaviruses consist of membrane-spanning glycoproteins Gn and Gc, RNA-dependent RNA polymerase (L protein) and nucleocapsid protein N, which encapsidates the viral genome, and thus forms the ribonucleoprotein (RNP). Interaction between the cytoplasmic tails of viral glycoproteins and RNP is assumed to be the only means how viral genetic material is incorporated into infectious virions. In the second paper of this thesis, it was shown by immunoprecipitation that viral glycoproteins and RNP interact in the purified virions. It was further shown that peptides derived from the cytoplasmic tails (CTs) of both Gn and Gc could bind RNP and recombinant N protein. In the fourth paper the cytoplamic tail of Gn but not Gc was shown to interact with genomic RNA. This interaction was probably rather unspecific since binding of Gn-CT with unrelated RNA and even single-stranded DNA were also observed. However, since the RNP consists of both N protein and N protein-encapsidated genomic RNA, it is possible that the viral genome plays a role in packaging of RNPs into virions. On the other hand, the nucleic acid-binding activity of Gn may have importance in the synthesis of viral RNA. Binding sites of Gn-CT with N protein or nucleic acids were also determined by peptide arrays, and they were largely found to overlap. The Gn-CT of hantaviruses contain a conserved zinc finger (ZF) domain with an unknown function. Some viruses need ZFs in entry or post-entry steps of the viral life cycle. Cysteine residues are required for the folding of ZFs by coordinating zinc-ions, and alkylation of these residues can affect virus infectivity. In the third paper, it was shown that purified hantavirions could be inactivated by treatment with cysteine-alkylating reagents, especially N-ethyl maleimide. However, the effect could not be pin-pointed to the ZF of Gn-CT since also other viral proteins reacted with maleimides, and it was, therefore, impossible to exclude the possibility that other cysteines besides those that were essential in the formation of ZF are required for hantavirus infectivity.Hantavirukset (perhe Bunyaviridae, suku Hantavirus) ovat vaipallisia negatiivi-juosteisen RNA genomin omaavia viruksia. Niiden kantajina on yleisesti pidetty jyrsijöitä, tosin viime aikoina on todettu joidenkin hyönteissyöjien myös voivan toimia kantajina hantaviruksille. Kantajissaan hantavirukset aiheuttavat pysyvän, oireettoman infektion. Sen sijaan ihmisissä osa hantavirus-lajeista tiedetään aiheuttavan munuaisoireista verenvuotokuumetta (HFRS), johon myös Suomessa esiintyvä Puumala-hantaviruksen aiheuttama myyräkuume (Nephropathia Epidemica) kuuluu. Munuaisoireiseen verenvuotokuumeeseen liittyy munuaisten vajaatoimintaa, mitä voidaan ainakin osittain selittää munuaisten tubulaarisolujen rappeutumisella. Jotkut hantavirukset kykenevät tietyissä olosuhteissa aiheuttamaan ohjattua solukuolemaa, apoptoosia, soluviljelymallissa ja on siksi mahdollista, että virus aikaansaa munuaisoireet suoran tubulaarisoluinfektion seurauksena. Tämän tutkimuksen ensimmäisessä osatyössä pyrittiin selvittämään solun signaalireittejä, jotka liittyvät hantavirusten aiheuttamaan apoptoosiin soluviljelymallissa. Solun elintoimintoja ylläpitävien kinaasien ERK1/2 aktiivisuuden havaittiin laskevan virus-infektion seurauksena, millä todennäköisesti on yhteys myös apoptoosin ilmentymiseen. ERK1/2 kinaasien esto oli merkittävin Tula-hantaviruksella, jonka uskotaan aiheuttavan oireettoman infektion ihmisessä, mutta se todennettiin myös taudinaiheuttamiskykyisillä hantaviruksilla. Hantavirukset koostuvat ulkokuoren vaippaproteiineista Gn ja Gc sekä vaipan sisälle pakkautuvista ribonukleoproteiineista (RNP). RNP:t koostuvat nukleokapsidiproteiinista N ja genomisesta RNA:sta. Jotta RNP:t voisivat pakkautua virukseen tehokkaasti, on niiden tunnistettava toinen tai molemmat viruksen vaippaproteiineista. Tämän tutkimuksen toisessa osatyössä RNP:n ja rekombinantti-tekniikalla tuotetun N proteiinin vuorovaikutus vaippaproteiinien Gn ja Gc välillä osoitettiin. Neljännessä osatyössä näytettiin että Gn kykenee sitomaan myös nukleiinihappoja, mukaan lukien viruksen genomista RNA:ta. Molemmissa aikasemmin mainituissa osatöissä käytettiin hyväksi myös peptideitä, joiden avulla vuorovaikutukset paikannettiin tiettyyn osaan Gn vaippaproteiinia. Nämä osatyöt yhdessä osoittavat, että RNP kykenee tunnistamaan viruksen vaippaproteiinit proteiini- ja nukleiinihappo-välitteisesti ja osaltaan selventävät hantavirusten koostumisen mekanismeja isäntäsolussa. Kolmannen osatyön tarkoituksena oli tutkia hantaviruspartikkelissa olevien vapaiden tiolien roolia viruksen sisäänmenossa isäntäsoluun. Tulokset osoittivat että vapaat tiolit ovat ratkaisevassa osassa tässä prosessissa ja että hantavirusten infektiivisyys kyetään estämään tioleja alkyloivilla yhdisteillä. Hantavirusten käsittely tiolien kanssa reagoivilla yhdisteillä ei heikentänyt virusten antigeenisuutta osoittaen, että tällä tavoin inaktivoitu hantavirus voi olla hyödyllinen diagnostiikassa tai ehkä jopa rokotteena

Neutrophil Activation in Acute Hemorrhagic Fever With Renal Syndrome Is Mediated by Hantavirus-Infected Microvascular Endothelial Cells

Hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS) in humans. Both diseases are considered to be immunologically mediated but the exact pathological mechanisms are still poorly understood. Neutrophils are considered the first line of defense against invading microbes but little is still known of their role in virus infections. We wanted to study the role of neutrophils in HFRS using blood and tissue samples obtained from Puumala hantavirus (PUUV)-infected patients. We found that neutrophil activation products myeloperoxidase and neutrophil elastase, together with interleukin-8 (the major neutrophil chemotactic factor in humans), are strongly elevated in blood of acute PUUV-HFRS and positively correlate with kidney dysfunction, the hallmark clinical finding of HFRS. These markers localized mainly in the tubulointerstitial space in the kidneys of PUUV-HFRS patients suggesting neutrophil activation to be a likely component of the general immune response toward hantaviruses. We also observed increased levels of circulating extracellular histones at the acute stage of the disease supporting previous findings of neutrophil extracellular trap formation in PUUV-HFRS. Mechanistically, we did not find evidence for direct PUUV-mediated activation of neutrophils but instead primary blood microvascular endothelial cells acquired a pro-inflammatory phenotype and promoted neutrophil degranulation in response to PUUV infection in vitro. These results suggest that neutrophils are activated by hantavirus-infected endothelial cells and may contribute to the kidney pathology which determines the severity of HFRS.Peer reviewe

The fundamental role of endothelial cells in hantavirus pathogenesis

Peer reviewe

The Clinical Presentation of Puumala Hantavirus Induced Hemorrhagic Fever with Renal Syndrome Is Related to Plasma Glucose Concentration

Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome characterized by thrombocytopenia, increased capillary leakage, and acute kidney injury (AKI). As glucosuria at hospital admission predicts the severity of PUUV infection, we explored how plasma glucose concentration associates with disease severity. Plasma glucose values were measured during hospital care in 185 patients with PUUV infection. They were divided into two groups according to maximum plasma glucose concentration: P-Gluc < 7.8 mmol/L (n = 134) and P-Gluc ≥ 7.8 mmol/L (n = 51). The determinants of disease severity were analyzed across groups. Patients with P-Gluc ≥7.8 mmol/L had higher hematocrit (0.46 vs. 0.43; p < 0.001) and lower plasma albumin concentration (24 vs. 29 g/L; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. They presented with higher prevalence of pulmonary infiltrations and pleural effusion in chest radiograph, higher prevalence of shock and greater weight change during hospitalization. Patients with P-Gluc ≥ 7.8 mmol/L were characterized by lower platelet count (50 vs. 66 × 109/L; p = 0.001), more severe AKI (plasma creatinine 272 vs. 151 µmol/L; p = 0.001), and longer hospital treatment (8 vs. 6 days; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. Plasma glucose level is associated with the severity of capillary leakage, thrombocytopenia, inflammation, and AKI in patients with acute PUUV infection

Plasma bradykinin concentrations during septic shock determined by a novel LC-MS/MS assay

Background: Bradykinin is an important mediator of inflammation and vascular permeability and could have an important role in the development of septic shock. Measurement of bradykinin by immunological methods may suffer from interference and lack of specificity. We developed and validated a liquid chromatography mass spectrometry assay (LC-MS/MS) for plasma bradykinin. Methods: We used plasma samples from healthy volunteers (n = 19) and patients with septic shock (n = 47). Stable isotope bradykinin internal standard was added to samples before solid-phase extraction and quantification by LC-MS/MS. Stability of bradykinin was studied for 12 months. Results: Our assay has good sensitivity (0.1 nmol/l) and a wide linear range (0.1-1000 nmol/1). Bradykinin added to plasma was stable for 12 months at -20 degrees C when a mixture of protease inhibitors was added at sampling but degraded during repeated freezing and thawing. Bradykinin concentration in plasma from septic shock patients (<0.1-0.6 nmol/l) did not change significantly during shock and recovery but differed slightly from that in healthy individuals (0.5-1.1 nmol/1). Conclusions: Our bradykinin assay was successfully used to determine bradykinin concentrations in plasma samples. Intensive care unit patients with septic shock had low concentrations of plasma bradykinin during both shock and recovery phases.Peer reviewe

Urinary extracellular vesicles carry multiple activators and regulators of coagulation

Cells shape their extracellular milieu by secreting intracellular products into the environment including extracellular vesicles which are lipid-bilayer limited membrane particles. These vesicles carry out a range of functions, including regulation of coagulation, via multiple contributor mechanisms. Urinary extracellular vesicles are secreted by various cells, lining the urinary space, including the nephron and bladder. They are known to have procoagulant properties, however, the details of this function, beyond tissue factor are not well known. The aim of the study was to access the role of urinary extracellular vesicles in impacting coagulation upon supplementation to plasma. This could indicate their physiological function upon kidney injury or pathology. Supplementation to standard human plasma and plasmas deficient in various coagulation factors was used for this purpose, and calibrated automated thrombogram (CAT (R)) was the major technique applied. We found that these vesicles contain multiple coagulation-related factors, and their lipid composition affects coagulation activities of plasma upon supplementation. Remarkably, these vesicles can restore thrombin generation in FVII, FVIII, FIX and FXI -deficient plasmas. This study explores the multiple roles of urinary extracellular vesicles in coagulation in in vitro blood coagulation and implies their importance in its regulation by several mechanisms.Peer reviewe

Hantaviruses and TNF-alpha act synergistically to induce ERK1/2 inactivation in Vero E6 cells.

BACKGROUND: We have previously reported that the apathogenic Tula hantavirus induces apoptosis in Vero E6 epithelial cells. To assess the molecular mechanisms behind the induced apoptosis we studied the effects of hantavirus infection on cellular signaling pathways which promote cell survival. We previously also observed that the Tula virus-induced cell death process is augmented by external TNF-a ... [More

Differential Regulation of PAI-1 in Hantavirus Cardiopulmonary Syndrome and Hemorrhagic Fever With Renal Syndrome

We analyzed the levels of circulating tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI)-1 in acute hantavirus cardiopulmonary syndrome (HCPS) and hemorrhagic fever with renal syndrome (HFRS). The levels of tPA commonly increased in both diseases, whereas PAI-1 correlated with disease severity in HCPS but not in HFRS.Peer reviewe

Coagulopathy in Acute Puumala Hantavirus Infection

Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome (HFRS), also called nephropathia epidemica (NE), which is mainly endemic in Europe and Russia. The clinical features include a low platelet count, altered coagulation, endothelial activation, and acute kidney injury (AKI). Multiple connections between coagulation pathways and inflammatory mediators, as well as complement and kallikrein-kinin systems, have been reported. The bleeding symptoms are usually mild. PUUV-infected patients also have an increased risk for disseminated intravascular coagulation (DIC) and thrombosis.Peer reviewe