Using lymph node transplantation as an approach to image cellular interactions between the skin and draining lymph nodes during parasitic infections

The growing use of protozoan parasites expressing fluorescent reporter genes, together with advances in microscopy, is enabling visualisation of their behaviour and functions within the host from the very earliest stages of infection with previously unparalleled spatiotemporal resolution. These developments have begun to provide novel insights, which are informing our understanding of where host immune responses may be initiated, which cells are involved and the types of response that are elicited. Here we will review some of these recent observations that highlight the importance of cellular communication between the site of infection and the draining lymph node (dLN) in establishing infection and immunity. We also highlight a number of remaining challenges and unknowns that arise through our inability to follow and fate map the journey of a single cell between spatially separated tissue sites. In response to these challenges, we review a recently described experimental strategy that extends the spatial and temporal limits of previous imaging approaches, most significantly allowing longitudinal analysis of cellular migration between the skin and draining lymph nodes in vivo, without the requirement for invasive surgery.     

Early steps of retrovirus replicative cycle

During the last two decades, the profusion of HIV research due to the urge to identify new therapeutic targets has led to a wealth of information on the retroviral replication cycle. However, while the late stages of the retrovirus life cycle, consisting of virus replication and egress, have been partly unraveled, the early steps remain largely enigmatic. These early steps consist of a long and perilous journey from the cell surface to the nucleus where the proviral DNA integrates into the host genome. Retroviral particles must bind specifically to their target cells, cross the plasma membrane, reverse-transcribe their RNA genome, while uncoating the cores, find their way to the nuclear membrane and penetrate into the nucleus to finally dock and integrate into the cellular genome. Along this journey, retroviruses hijack the cellular machinery, while at the same time counteracting cellular defenses. Elucidating these mechanisms and identifying which cellular factors are exploited by the retroviruses and which hinder their life cycle, will certainly lead to the discovery of new ways to inhibit viral replication and to improve retroviral vectors for gene transfer. Finally, as proven by many examples in the past, progresses in retrovirology will undoubtedly also provide some priceless insights into cell biology.     

Infection of Chinese cabbage by Plasmodiophora brassicae leads to a stimulation of plant growth: impacts on cell wall metabolism and hormone balance

The importance of plant hormones in clubroot infection has long been recognized. The morphological changes, such as cell division and cell elongation leading to gall formation are triggered in the early stages of infection. We analysed cell expansion by localizing Xyloglucan endoTransglucosylase/Hydrolase (XTH)-action and screened the endogenous concentrations of several classes of phytohormones by mass spectrometry in the early stages of Plasmodiophora brassicae infection in Chinese cabbage (Brassica rapa spp. pekinensis). Infected plants showed a general transient growth promotion early in infection. Furthermore a clear XTH action was visible in the epidermal layer of infected roots. Complex changes in the endogenous phytohormone profile were observed. Initially infection resulted in an increased total auxin pool. The auxin increase, together with an increased XTH action, results in wall loosening and consequently cell expansion. When the first secondary plasmodia are formed, thirteen days after infection (DAI), can be considered a switch point in phytohormone metabolism. Twenty-one DAI the plasmodia might act as a plant hormone sink resulting in a reduction in the active cytokinin pool and a lower indole-3-acetic acid content in the infected plants.     

西方长寿与衰老研究史精要

长寿是一个美丽的梦想,衰老是一个神秘的谜团.旨在回顾西方文明从远古至20世纪初,从民间到学术界,探索长寿之路,破解衰老之谜,冥思苦想苦苦追寻的漫漫历程,并按历史的足迹,将这错综复杂的过程分为八个历史时期予以阐述.     

Manipulation of host innate immune responses by the malaria parasite

It has long been known that malaria infection causes host immune modulation by various mechanisms. However, the role of Toll-like receptors (TLRs) in mediating innate immune responses to parasite-derived components during the blood stages of malaria has only recently been described. TLRs might have an important role in pathogenesis during malaria infection, as supported by genetic analyses in mice and humans. Moreover, recent findings revealed that sporozoites can partially differentiate in lymph nodes and that liver stages induce the formation of previously unknown parasite-filled vesicles (merosomes) that could function as immune escape machinery. Elucidation of the mechanisms by which the host innate immune system responds to, and/or is manipulated by, Plasmodium infection will hopefully lead to discoveries of potential targets that will ultimately prevent and/or intervene in malaria infection.     

Transient antiretroviral treatment during acute simian immunodeficiency virus infection facilitates long-term control of the virus

Experimental evidence and mathematical models indicate that CD4+ T-cell help is required to generate memory cytotoxicT-lymphocyte precursors (CTLp) that are capable of persisting without ongoing antigenic stimulation, and that such responses are necessary to clear an infection or to control it in the long term. Here we analyse mathematical models of simian immunodeficiency virus (SIV) replication in macaques, assuming that SIV impairs specific CD4+ T-cell responses. According to the models, fast viral replication during the initial stages of primary infection can result in failure to generate sufficient long-lived memory CTLp required to control the infection in the long term. Modelling of drug therapy during the acute phase of the infection indicates that transient treatment can minimize the amount of virus-induced immune impairment, allowing a more effective initial immune sensitization. The result is the development of high levels of memory CTLp that are capable of controlling SIV replication in the long term, in the absence of continuous treament. In the model, the success of treatment depends crucially on the timing and duration of antiretroviral therapy. Data on SIV-infected macaques receiving transient drug therapy during acute infection support these theoretical predictions. The data and modelling suggest that among subjects controlling SIV replication most efficiently after treatment, there is a positive correlation between cellular immune responses and virus load in the post-acute stage of infection. Among subjects showing less-efficient virus control, the correlation is negative. We discuss our findings in relation to previously published data on HIV infection.     

The immune response of male DSN hamsters to a primary infection with Ancylostoma ceylanicum

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3-4 times the weight in control animals by weeks 3-7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3-4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.     

Peculiarities of metabolism of the microsporidia Nosema grylli during the intracellular development

A long adaptation of Microsporidia to intracellular development supposes the host-derived ATP dependence of merogony and sporogony stages. To prove this assumption the activities of ten carbohydrate and energy metabolism enzymes were compared in the microsporidia Nosema grylli intracellular stages and mature spores. This species infects the fat body of crickets Gryllus bimaculatus. We have demonstrated lower activities of glycolytic enzymes, phosphoglucomutase and glucose-6-PhDH in the metabolically active meronts and sporonts than in the dormant mature spores. Low glycolysis level indicates that carbohydrate catabolism is not a principal mechanism of ATP supply in the N. grylli intracellular stages. Furthermore, we have not revealed a preferable expenditure of glycogen in comparison with triglycerides in infected cricket fat bodies. The N. grylli infection causes an equal reduction of glycogen and lipid content approximately in 2-3 times. Microsporidia have not mitochondria, Krebs cycle and electron-transport chain. Therefore they are not able to utilise fat reserves for ATP production. It seems to be proposed that microsporidia consume exogenous ATP which is produced by host cell metabolic system. The N. grylli infection provokes an increase of ATP content and ratio of ATP/ADP concentrations in cricket fat bodies approximately in 4 times. These data indicates a rise of host cell energy metabolism rate during the infection.     

A revised arithmetic model of long slender to short stumpy transformation in the African trypanosomes

An arithmetic model that closely approximates an African trypanosome infection in immunosuppressed mice is presented. The final model was based on an examination of the following parameters: the rate of long slender to short stumpy transition, the maximum percentage of long slender to short stumpy stages that can be induced, the survival time or half life of the short stumpy stage in vivo, and the rate (%) of long slender to short stumpy stage transition following the peak in transformation. The model is based on the assumption that the long slender to short stumpy transition is parasite population dependent and that in mice the long slender to short stumpy transition only begins when the trypanosome population reaches a density of 1 x 10(7) trypanosomes/ml. The model predicts that the parasitemia during the first several days of an infection is controlled solely by the kinetics of the transition of the dividing long slender stage to the nondividing short stumpy stage. It was not necessary to include in the model the host's immune response in order to simulate the early growth kinetics of pleomorphic trypanosomes in infected mice.     

Leishmania manipulation of sand fly feeding behavior results in enhanced transmission

In nature the prevalence of Leishmania infection in whole sand fly populations can be very low (<0.1%), even in areas of endemicity and high transmission. It has long since been assumed that the protozoan parasite Leishmania can manipulate the feeding behavior of its sand fly vector, thus enhancing transmission efficiency, but neither the way in which it does so nor the mechanisms behind such manipulation have been described. A key feature of parasite development in the sand fly gut is the secretion of a gel-like plug composed of filamentous proteophosphoglycan. Using both experimental and natural parasite-sand fly combinations we show that secretion of this gel is accompanied by differentiation of mammal-infective transmission stages. Further, Leishmania infection specifically causes an increase in vector biting persistence on mice (re-feeding after interruption) and also promotes feeding on multiple hosts. Both of these aspects of vector behavior were found to be finely tuned to the differentiation of parasite transmission stages in the sand fly gut. By experimentally accelerating the development rate of the parasites, we showed that Leishmania can optimize its transmission by inducing increased biting persistence only when infective stages are present. This crucial adaptive manipulation resulted in enhanced infection of experimental hosts. Thus, we demonstrate that behavioral manipulation of the infected vector provides a selective advantage to the parasite by significantly increasing transmission.     

Focal adhesion kinase is a component of antiviral RIG-I-like receptor signaling

Viruses modulate the actin cytoskeleton at almost every step of their cellular journey from entry to?egress. Cellular sensing of these cytoskeletal changes may function in the recognition of viral infection. Here we show that focal adhesion kinase (FAK), a focal adhesion localized tyrosine kinase that transmits signals between the extracellular matrix and the cytoplasm, serves as a RIG-I-like receptor antiviral signaling component by directing mitochondrial antiviral signaling adaptor (MAVS) activation. Cells deficient in FAK are highly susceptible to RNA virus?infection and attenuated in antiviral signaling. We show that FAK interacts with MAVS at the mitochondrial membrane in a virus infection-dependent manner and potentiates MAVS-mediated signaling via a kinase-independent mechanism. A cysteine protease encoded by enteroviruses cleaves FAK to suppress its role in innate immune signaling. These findings suggest that FAK serves as a link between cytoskeletal perturbations that occur during virus infection and activation of innate immune signaling.     

Virus trafficking - learning from single-virus tracking

What could be a better way to study virus trafficking than 'miniaturizing oneself' and 'taking a ride with the virus particle' on its journey into the cell? Single-virus tracking in living cells potentially provides us with the means to visualize the virus journey. This approach allows us to follow the fate of individual virus particles and monitor dynamic interactions between viruses and cellular structures, revealing previously unobservable infection steps. The entry, trafficking and egress mechanisms of various animal viruses have been elucidated using this method. The combination of single-virus trafficking with systems approaches and state-of-the-art imaging technologies should prove exciting in the future.     

The Plasmodium sporozoite journey: a rite of passage

Sporozoites are the most versatile of the invasive stages of the Plasmodium life cycle. During their passage within the mosquito vector and the vertebrate host, sporozoites display diverse behaviors, including gliding locomotion and invasion of, migration through and egress from target cells. At the end of the journey, sporozoites invade hepatocytes and transform into exoerythrocytic stages, marking the transition from the pre-erythrocytic to the erythrocytic part of the life cycle. This article discusses recent work, mostly done with rodent malaria parasites, that has contributed to a better understanding of the sporozoites' complex biology and which has opened up new avenues for future sporozoite research.     

The Biology of Trypanosoma diemyctyli, Tobey. III. Factors influencing the cycle of Trypanosoma diemyctyli in the vertebrate host Triturus v. viridescens.

SYNOPSIS. The effects of some environmental influences on the cycle of Trypanosoma diemyctyli in Triturus v. viridescens are described. Bleeding of the host produced a reduction in the number of trypanosomes but did not affect their growth rate. The temperature at which the host was maintained affected the cycle of the trypanosomes. The length of the post-inoculation latent stage increased from 24 hours at 25°C. to an indefinitely long time at 5°C. The trypanosomes were found to be dimorphic. Adult parasites of the short form had a range of 45–75 μ and those of the long form of 76–116 μ. Growth rate of the trypanosomes was inhibited or greatly retarded at temperatures of 10°C. or lower and was greatest at 25°C. The size attained by the parasites and the number of parasites were greatest at 15°C. At this temperature the infection was pathogenic and the dimorphic parasites were in their long form. At the higher temperatures (20–25°C.) the infection was non-pathogenic with the trypanosomes in their short form.
The infection is primarily one of adult newts. Experiments indicated that the larvae were resistant to the trypanosomes at all temperatures while the red efts were not. The latter are usually free from the trypanosomes because they are not exposed to them. Attempts to infect other newts and to locate any cryptic stages by the injection of blood and tissues from infected newts gave negative results.
Starvation, sodium salicylate, and treatments used to control fungus infection of the newts had no detectable effects on the trypanosomes.     

Modified Oligonucleotides: New Structures,New Properties,and New Spheres of Application

Russian Journal of Bioorganic Chemistry - Nucleic acids have made a long and arduous journey “from the bench to the bedside.” At&nbsp;present, it can be assumed that drugs based on...     

Road transport of farm animals: effects of journey duration on animal welfare

Transport of farm animals gives rise to concern about their welfare. Specific attention has been given to the duration of animal transport, and maximum journey durations are used in legislation that seek to minimise any negative impact of transport on animal welfare. This paper reviews the relatively few scientific investigations into effects of transport duration on animal welfare in cattle, sheep, horses, pigs and poultry. From the available literature, we attempt to distinguish between aspects, which will impair welfare on journeys of any duration, such as those associated with loading, and those aspects that may be exacerbated by journey time. We identify four aspects of animal transport, which have increasing impact on welfare as transport duration increases. These relate to (i) the physiological and clinical state of the animal before transport; and - during transport - to (ii) feeding and watering; (iii) rest and (iv) thermal environment. It is thus not journey duration per se but these associated negative aspects that are the cause of compromised welfare. We suggest that with a few exceptions, transport of long duration is possible in terms of animal welfare provided that these four issues can be dealt with for the species and the age group of the animals that are transported.     

Rotavirus Entry: a Deep Journey into the Cell with Several Exits

Rotaviruses are the leading etiological agents of acute gastroenteritis in infants and young children worldwide. These nonenveloped viruses enter cells using different types of endocytosis and, depending on the virus strain, travel to different endosomal compartments before exiting to the cytosolic space. In this Gem, we review the viral and cellular factors involved in the different stages of a productive virus cell entry and share with the readers the journey that we have taken into the cell to learn about virus entry.     

An immunological assay for determination of baculovirus titers in 48 hours

Th baculovirus expression system is a system of choice for expressing eukaryotic proteins. Large amounts of biologically active material can be generated using this system by infecting insect cells with a baculovirus expressing the target protein. At several stages during the production of a baculovirus stock, it is necessary to titer the virus. Current methods have long time lines and are either technically difficult or are limited to viruses expressing a reporter gene. The new assay described here yields titers in 48 h, is easy to perform using 96-well plates, and is applicable to any Autographa californica nucleopolyhedrovirus-based recombinant baculovirus. This assay uses an antibody to a viral envelope glycoprotein to detect infected cells via immunostaining. The titer is determined by counting foci of infection under a light microscope. The required incubation period is shortened considerably because infected cells express viral antigens long before the macroscopic signs of infection scored in other assays become apparent. Titers determined using this immunological assay are comparable, both in value and variability, to those obtained using a traditional method, provided that the stocks have titers above 10(4) pfu/ml.     

Dead reckoning in a small mammal: the evaluation of distance

When hoarding food under infra-red light, golden hamsters Mesocricetus auratus W. return fairly directly from a feeding place to their nest site by evaluating and updating internal signals that they have generated during the previous outward journey to the feeding place. To test more specifically the animals' capacity to evaluate the linear components of the outward journey, the subjects were led from their (cone-shaped) nest to a feeding place along a detour which comprised either 2 (experiment 1) or 5 (experiment 2) segments; adjoining segments were at right angles to each other. In these conditions, the subjects remained significantly oriented towards the nest and therefore were capable of assessing translations as well as rotations during the outward journey. In experiment 3, the nest was removed after the hamsters had started the direct outward journey to the feeding place and the hamsters were rotated during the food uptake. The animals were no longer oriented towards the starting point of their journey, but nonetheless covered, along a fairly straight path, the correct homing distance, and then changed over to a circular search path. These results confirm that mammals can derive the linear components of an outward journey from self-generated signals and therefore are able to judge the homing distance without relying on cues from the environment. For a number of detour outward journeys, our data yield an unexpectedly good fit to Müller and Wehner's (1988) model of dead reckoning in ants. However, this is no longer the case when the outward journey contains an initial loop which brings the subject back to the starting point. These findings are discussed in terms of the biological significance and limitations of an approximate form of path integration.     

Schistosomiasis mass drug administration in the Philippines: lessons learnt and the global implications

Schistosomiasis was first reported in the Philippines in 1906. A variety of treatments have been deployed to cure infection and to control the disease in the long-term. We discuss the journey to combat the disease in the Philippines and the lessons learnt which have implications for schistosomiasis control globally.