Induced hyperlipaemia and immune challenge in locusts

Injections of immunogens, such as β-1,3-glucan or lipopolysaccharide (LPS), bring about a marked hyperlipaemia with associated changes in lipophorins and apolipophorin-III in the haemolymph of Locusta migratoria. These changes are similar to those observed after injection of adipokinetic hormone (AKH). The possibility that endogenous AKH is released as part of the response to these immunogens is investigated using passive immunisation against AKH-I, and measurement of AKH-I titre in the haemolymph after injection of immunogens. The data presented show that, despite the similarity of the changes brought about by the presence of immunogens in the haemolymph to those brought about by AKH, there is no release of endogenous AKH after injection of laminarin or LPS. A direct effect of the immunogens on release of neutral lipids by the fat body cannot be demonstrated in vitro, and the mechanism by which hyperlipaemia is induced during immune challenge remains uncertain

Apolipophorin-III Mediates Antiplasmodial Epithelial Responses in Anopheles gambiae (G3) Mosquitoes

Apolipophorin-III (ApoLp-III) is known to play an important role in lipid transport and innate immunity in lepidopteran insects. However, there is no evidence of involvement of ApoLp-IIIs in the immune responses of dipteran insects such as Drosophila and mosquitoes.We report the molecular and functional characterization of An. gambiae apolipophorin-III (AgApoLp-III). Mosquito ApoLp-IIIs have diverged extensively from those of lepidopteran insects; however, the predicted tertiary structure of AgApoLp-III is similar to that of Manduca sexta (tobacco hornworm). We found that AgApoLp-III mRNA expression is strongly induced in the midgut of An. gambiae (G3 strain) mosquitoes in response to Plasmodium berghei infection. Furthermore, immunofluorescence stainings revealed that high levels of AgApoLp-III protein accumulate in the cytoplasm of Plasmodium-invaded cells and AgApoLp-III silencing increases the intensity of P. berghei infection by five fold.There are broad differences in the midgut epithelial responses to Plasmodium invasion between An. gambiae strains. In the G3 strain of An. gambiae AgApoLp-III participates in midgut epithelial defense responses that limit Plasmodium infection

Microfluidic Chip for Molecular Amplification of Influenza A RNA in Human Respiratory Specimens

A rapid, low cost, accurate point-of-care (POC) device to detect influenza virus is needed for effective treatment and control of both seasonal and pandemic strains. We developed a single-use microfluidic chip that integrates solid phase extraction (SPE) and molecular amplification via a reverse transcription polymerase chain reaction (RT-PCR) to amplify influenza virus type A RNA. We demonstrated the ability of the chip to amplify influenza A RNA in human nasopharyngeal aspirate (NPA) and nasopharyngeal swab (NPS) specimens collected at two clinical sites from 2008–2010. The microfluidic test was dramatically more sensitive than two currently used rapid immunoassays and had high specificity that was essentially equivalent to the rapid assays and direct fluorescent antigen (DFA) testing. We report 96% (CI 89%,99%) sensitivity and 100% (CI 95%,100%) specificity compared to conventional (bench top) RT-PCR based on the testing of n = 146 specimens (positive predictive value = 100%(CI 94%,100%) and negative predictive value = 96%(CI 88%,98%)). These results compare well with DFA performed on samples taken during the same time period (98% (CI 91%,100%) sensitivity and 96%(CI 86%,99%) specificity compared to our gold standard testing). Rapid immunoassay tests on samples taken during the enrollment period were less reliable (49%(CI 38%,61%) sensitivity and 98%(CI 98%,100%) specificity). The microfluidic test extracted and amplified influenza A RNA directly from clinical specimens with viral loads down to 103 copies/ml in 3 h or less. The new test represents a major improvement over viral culture in terms of turn around time, over rapid immunoassay tests in terms of sensitivity, and over bench top RT-PCR and DFA in terms of ease of use and portability

Insect immune activation by apolipophorin III is correlated with the lipid-binding properties of this protein

Apolipophorin III (apoLp-III) is an exchangeable insect apolipoprotein consisting of five amphipathic a-helices. The protein is able to open reversibly on associating with hydrophobic surfaces and plays a role both in lipid transport and induction of immune responses. Point mutations were introduced at positions 66 (N ->D) and/or 68 (K ->E) between helices 2 and 3, a region possibly serving as a hinge for the opening of the molecule when associating with lipids. The lipid-binding properties of the mutant proteins were analyzed and compared with their immune inducing activities. Structural properties of the proteins were studied by far UV circular dichroism spectroscopy and their abilities to form discoidal complexes of dimyristoyl phosphatidylcholine (DMPC) vesicles were investigated. In comparison to wildtype apoLp-III, apoLp-III(N66D/K68E), and apoLp-III(K68E) displayed significantly decreased lipid-binding abilities and immune stimulating activities, while these effects were less noticeable with apoLp-III(N66D). The secondary structure of the double mutant apoLp-III(N66D/K68E) was similar to that of wild-type apoLp-III. A noticeable reduction of alpha -helical content could be observed for the single mutants apoLp-III(N66D) and apoLp-III(K68E), which was accompanied by an increase in percentage amount of beta -turns. The stability of the secondary structure determined by heat denaturation was not affected by mutagenesis. Furthermore, the ability of all proteins to form discoidal complexes of equal size and shape in the presence of dimyristoyl phosphatidylcholine indicated that the mutagenesis did not affect the molecular architecture in the lipid-associated conformation. The relationship between reduced lipid association and reduced immune stimulating activity supports the hypothesis that apoLp-III-induced immune activation is triggered by the conformational change of the protein