First detection of <Emphasis Type="Italic">Vespa velutina nigrithorax</Emphasis> (Hymenoptera: Vespidae) in the Balearic Islands (Western Mediterranean): a challenging study case

The yellow-legged hornet, Vespa velutina nigrithorax is an Invasive Alien Species introduced into Europe in 2004, and is currently present in France, Italy, Spain, Portugal, Germany, and Belgium. It was also recently introduced in the United Kingdom and Switzerland. Here we present the first detection of V. velutina in the westernmost Mediterranean islands (Majorca, Balearic archipelago). In October 2015, a specimen of hornet, which was later identified as V. velutina, was sent to the laboratory of Zoology at the University of the Balearic Islands by a beekeeper from the locality of Sóller (northwest of Majorca). After the identification, and in coordination with the local authorities, an intensive survey was implemented in the area of first detection using sticky traps baited with protein and nest detection by directly observing the flight route of adult hornets from two or three feeding points. The first nest was detected on 30th October 2015 and was entirely removed. The next year, nine other nests were located from August to November 2016 in the same area and again, all of them were removed entirely. It is the first report on an island of destroying nests as a means of controlling the spread, a scenario very different to mainland Europe. All nests were detected in evergreen tree species (pines, holm oaks, and common cypress) in the “Serra de Tramuntana”, a mountain range located in the north-west of the island of Majorca (3667 km²), which is situated 176 km off the mainland. Considering the presumably early stage of the invasion of V. velutina in Majorca, the size of the island, and the confinement of the detection area, we consider that this species could be eradicated if resources and a specific program for eradication in Majorca are implemented in coordination with all involved partners.     

The immune status of Schwann cells: what is the role of the P2X7 receptor?

The peripheral nervous system (PNS) displays structural barriers and a lack of lymphatic drainage which strongly limit the access of molecules and cells from the immune system. In addition, the PNS has the ability to set up some specific mechanisms of immune protection to limit the pathogenicity of inflammation processes following insults by pathogens or inflammatory autoimmune diseases like the Guillain-Barré syndrome. Schwann cells are among the most prominent cells which can display immune capabilities in the PNS. Numerous in vitro studies have shown that Schwann cells were indeed able to display a large repertoire of properties, ranging from the participation to antigen presentation, to secretion of pro- and anti-inflammatory cytokines, chemokines and neurotrophic factors. In vivo studies have confirmed the immune capabilities of Schwann cells. The aim of this review is to present how Schwann cells can participate to the initiation, the regulation and the termination of the immune response in the light of the recent discovery of the Schwann cell expression of purinergic P2X7 receptors.     

Opening and refolding of simian virus 40 and in vitro packaging of foreign DNA.

Simian virus 40 (SV40) can be disassembled under mild conditions by reducing disulfide bonds in the capsid and removing calcium ions. The nucleoprotein complexes formed, analyzed by electron microscopy, were circular and made up of 59 +/- 4 subunits, each with a diameter of about 10 nm. The complexes contained the viral DNA, histones, and the viral capsid proteins. The complexes had much-reduced infectivities compared with intact SV40. Addition of calcium ions to the disrupted virus caused the nucleoprotein complexes to refold into virus-like structures which sedimented at the same rate as intact SV40 and regained infectivity. Treatment of the disrupted SV40 with a high concentration of salt dissociated the viral proteins from the DNA. Lowering stepwise the salt concentration, removing the reducing agent, and adding calcium ions allowed structures to be reformed, and these structures sedimented, like SV40, at 240S and were infectious. The plaque-forming ability of the reconstituted particles was between that of the dissociated components and that of intact SV40. The addition of purified DNA of polyomavirus to the dissociated SV40 before the lowering of the salt concentration showed that virus-like structures could be formed from SV40 proteins and a foreign DNA.     

Modulation of neurotransmission by reciprocal synapse-glial interactions at the neuromuscular junction

Perisynaptic Schwann cells are glial cells that are closely associated with pre- and postsynaptic elements of the neuromuscular junction. Recent evidence shows that these cells detect and modulate neurotransmission in an activity-dependent fashion. Through G-protein signalling and Ca²⁺ released from internal stores they can decrease or increase neurotransmitter release, respectively. Thus, they help to establish the level of neurotransmission associated with activity dependent short-term synaptic plasticity. We discuss evidence implicating perisynaptic Schwann cells as being active partners in neurotransmission at the neuromuscular junction, with emphasis on the modulation of short-term plasticity and potential implications for long-term changes.     

Maturation and release of interleukin-1beta by lipopolysaccharide-primed mouse Schwann cells require the stimulation of P2X7 receptors

The P2X7 receptor, mainly expressed by immune cells, is a ionotropic receptor activated by high concentration of extracellular ATP. It is involved in several processes relevant to immunomodulation and inflammation. Among these processes, the production of extracellular interleukin-1beta (IL-1beta), a pro-inflammatory cytokine, plays a major role in the activation of the cytokine network. We have investigated the role of P2X7 receptor and of an associated calcium-activated potassium conductance (BK channels) in IL-1beta maturation and releasing processes by Schwann cells. Lipopolysaccharide-primed Schwann cells synthesized large amounts of pro-IL-1beta but did not release detectable amounts of pro or mature IL-1beta. ATP on its own had no effect on the synthesis of pro-IL-1beta, but a co-treatment with lipopolysaccharide and ATP led to the maturation and the release of IL-1beta by Schwann cells. Both mechanisms were blocked by oxidized ATP. IL-1beta-converting enzyme (ICE), the caspase responsible for the maturation of pro-IL-1beta in IL-1beta, was activated by P2X7 receptor stimulation. The specific inhibition of ICE by the caspase inhibitor Ac-Tyr-Val-Ala-Asp-aldehyde blocked the maturation of IL-1beta. In searching for a link between the P2X7 receptor and the activation of ICE, we found that enhancing potassium efflux from Schwann cells upregulated the production of IL-1beta, while strongly reducing potassium efflux led to opposite effects. Blocking BK channels actually modulated IL-1beta release. Taken together, these results show that P2X7 receptor stimulation and associated BK channels, through the activation of ICE, leads to the maturation and the release of IL-1beta by immune-challenged Schwann cells.     

Phoretic relationship between the myceliophagous mite Microdispus lambi (Acari: Microdispidae) and mushroom flies in Spanish crops

We studied the role played by the phorid Megaselia halterata (Wood) and the sciarid Lycoriella auripila (Winnertz) in the phoretic dispersion of the myceliophagous mite Microdispus lambi (Acari: Pygmephoridae). Twenty‐four crops were monitored during 18 months in commercial mushroom farms in Castilla‐La Mancha (Spain). Adults of both species were collected weekly and the mites they carried were counted and identified. Both phorids (19.6%) and sciarids (4.4%) carried the mite M. lambi. The calculated load of each was 3.4 M. lambi mites per phorid and 1.9 per sciarid. The same percentage of male and female phorid was used as vector, but the load was slightly higher for females (1.86 mites per female compared with1.48 mites per male). A mean of 7.2% of the phorids examined in winter were vectors of M. lambi, while in spring and autumn of the first year the average was more than 22%. The mean load did not vary significantly between seasons. Inside the mushroom farms, less than 10% of a small initial population of phorids carried mites (less than two mites per phorid). As the cycle progressed, more than 35% of a larger population of emerging flies did so (average 3.5 mites per phorid vector). At the end of the growth cycle, the flies may fly off to colonise nearby farms, favouring the propagation of M. lambi from infested to uninfested crops. Megaselia halterata is the principal vector of M. lambi in the mushroom farms of Castilla‐La Mancha due to their high numbers, the high percentage carrying mites and the number of M. lambi they carry.