A new role for PGRP-S (Tag7) in immune defense: lymphocyte migration is induced by a chemoattractant complex of Tag7 with Mts1

PGRP-S (Tag7) is an innate immunity protein involved in the antimicrobial defense systems, both in insects and in mammals. We have previously shown that Tag7 specifically interacts with several proteins, including Hsp70 and the calcium binding protein S100A4 (Mts1), providing a number of novel cellular functions. Here we show that Tag7–Mts1 complex causes chemotactic migration of lymphocytes, with NK cells being a preferred target. Cells of either innate immunity (neutrophils and monocytes) or acquired immunity (CD4⁺ and CD8⁺ lymphocytes) can produce this complex, which confirms the close connection between components of the 2 branches of immune response.     

Annual cycles of four flea species in the central Negev desert

Bionomics of fleas (Siphonaptera) parasitizing rodent hosts, mostly the gerbil Gerbillus dasyurus (Wagner) and the jird Meriones crassus Sundevall (Gerbillidae), were investigated in the central Negev desert of Israel. Populations were sampled weekly (by Sherman trapping of hosts) from August 2000 to July 2001. Among 1055 fleas of nine species captured, four species predominated (94%). Two species of Pulicidae, Xenopsylla dipodilli Smit and X. ramesis (Rothschild), reproduced perennially, whereas adults of Nosopsyllus iranus theodori Smit (Ceratophyllidae) and Stenoponia tripectinata medialis Jordan (Hystrichopsyllidae) occurred only in cool months (October-March). During their main activity season on the most infested host species (estimated from > 300 trap-nights/month), prevalence of these four flea species reached 40-70%, 20-30%, 100% and 50-70%, respectively, with infestation intensities of 2-2.7, 7-12, 2-3.5 and 2.5-7 fleas per infested rodent, respectively. Xenopsylla dipodilli oviposition peaked during autumn with parous rate > 80% by September-October. During December-April, the majority of X. dipodilli females were immature and/or nulliparous (defined as having mature ovaries but no follicular relics). In contrast, X. ramesis had two reproductive peaks, in mid-spring and autumn, evidenced by the influx of immature females in late spring and summer (30-40%) and in winter (20-30%) after maximal parous rates: 80-100% in March-April and 95-100% in October-November. Nosopsyllus iranus theodori and Stenoponia tripectinata medialis adults occurred only during cool months. At the beginning of activity, during October-November, the sex ratio of N. i. theodori was strongly biased to females (86%) that were immature and/or nulliparous. In winter, adult females were 52-65% parous and 10-32% immature. In March, as the adult population of N. i. theodori declined, 78% of females were parous and 12% immature. Seasonal activity of S. t. medialis (November-March) was shorter than for the other three species; females were predominantly nulliparous in November (80%), after which the proportion of parous females increased gradually to 84% in February. Two females of S. t. medialis collected in March were mature but nulliparous, suggesting that this species of flea might 'oversummer' (as pupae or teneral adults) in the cocooned stage.     

Larval interspecific competition in two flea species parasitic on the same rodent host

Abstract.  1. The fleas Xenopsylla conformis and Xenopsylla ramesis exploit the same rodent host, Meriones crassus , and replace each other between two different habitats situated at the opposite sides of a steep precipitation gradient. It was hypothesised that the reason for this paratopic distribution is competition between larvae of the two species for food resources.
2. This hypothesis was tested by studying the performance of larvae of the two species in terms of their developmental success in mixed-species and single-species treatments under different air temperatures, relative humidities, substrate textures, and food abundance.
3. The number of individuals of X. conformis that survived until emergence depended significantly on the presence of competing species, being, in general, lower in mixed-species compared with single-species treatments. The decrease in developmental success of X. conformis in mixed-species treatments was found mainly during food shortage. In contrast, presence of the competitor did not affect the number of X. ramesis that survived until emergence. No effect of the presence of the competitor on duration of development or sex ratio was found in either species.
4. The results of this study, together with the results of our previous studies, provide an explanation for the paratopic distribution of X. conformis and X. ramesis that exploit the same host species.     

Host discrimination by two desert fleas using an odour cue

We compared the responses of two fleas, Xenopsylla dipodilli and Parapulex chephrenis simultaneously exposed to the odours of their rodent hosts, Gerbillus dasyurus (specific host ofX. dipodilli ) and Acomys cahirinus (specific host of P. chephrenis). We hypothesized that fleas are able to discriminate between host species by using an odour cue and predicted that X. dipodilli andP. chephrenis would select an odour of an appropriate host species. Xenopsylla dipodilli choseG. dasyurus significantly more often than A. cahirinus, whereas P. chephrenis choseA. cahirinus significantly more often than G. dasyurus. The ability to select an appropriate host species did not differ significantly either between flea species or between individuals of different sex or age classes within flea species. No X. dipodilli, but 67 of 150 P. chephrenis, refused to choose a host. The latency to move in an experimental maze was significantly shorter for X. dipodilli than P. chephrenis. The flea species also differed in the time taken from the beginning of the movement to the choice of a host, withX. dipodilli being faster than P. chephrenis. Neither flea sex nor age affected this parameter in either species. Females of both flea species produced significantly more eggs when they fed on their specific host than when they fed on the other host species. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

AmylPepPred: Amyloidogenic Peptide Prediction tool

We present an efficient computational architecture designed using supervised machine learning model to predict amyloid fibril forming protein segments, named AmylPepPred. The proposed prediction model is based on bio-physio-chemical properties of primary sequences and auto-correlation function of their amino acid indices. AmylPepPred provides a user friendly web interface for the researchers to easily observe the fibril forming and non-fibril forming hexmers in a given protein sequence. We expect that this stratagem will be highly encouraging in discovering fibril forming regions in proteins thereby benefit in finding therapeutic agents that specifically aim these sequences for the inhibition and cure of amyloid illnesses.

Availability

AmylPepPred is available freely for academic use at www.zoommicro.in/amylpeppred     

Development rates of two Xenopsylla flea species in relation to air temperature and humidity

The rate of development of immature fleas, Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild (Siphonaptera: Xenopsyllidae) was studied in the laboratory at 25 degrees C and 28 degrees C with 40, 55, 75 and 92% relative humidity (RH). These fleas are separately associated with the host jird Meriones crassus Sundevall in different microhabitats of the Ramon erosion cirque, Negev Highlands, Israel. This study of basic climatic factors in relation to flea bionomics provides the basis for ecological investigations to interpret reasons for paratopic local distributions of these two species of congeneric fleas on the same host. Both air temperature and RH were positively correlated with duration of egg and larval stages in both species. Change of humidity between egg and larval environments did not affect duration of larval development at any temperature. At each temperature and RH, the eggs and larvae of X. ramesis did not differ between males and females in the duration of their development, whereas female eggs and larvae of X. conformis usually developed significantly faster than those of males. For both species, male pupae developed slower than female pupae at the same air temperature and RH. Air temperature, but not RH, affected the duration of pupal development. At each humidity, duration of the pupal stage was significantly longer at 25 degrees C than at 28 degrees C: 15.3+/-1.7 vs. 11.7+/-1.2 days in X. conformis; 14.1+/-2.0 vs. 11.5+/-1.7 days in X. ramesis, with a significantly shorter pupal period of the latter species at 25 degrees C. These limited interspecific bionomic contrasts in relation to basic climatic factors appear insufficient to explain the differential habitat distributions of X. conformis and X. ramesis.