An antibody diagnostic for hymenopteran parasitism is specific for a homologue of elongation factor-1 alpha

Detection of parasitism in diamondback moth, Plutella xylostella (L.), using differential melanization and coagulation reactions

Diamondback moth (DBM), Plutella xylostella, is known for causing damage to Brassica crops and developing resistance to chemical and biological pesticides; it has become one of the most difficult pests to manage in many regions around the world. The only way to reduce reliance on pesticides is to maximize the role of natural control agents for integrated pest management programs and be able to incorporate the mortality from control agents into pest control decision-making. More than 90 hymenopterous parasitoids are associated with DBM worldwide; among them, Diadegma semiclausum, is a major endoparasitoid of P. xylostella. To optimize parasitism of pests in pest control decision-making, it is necessary to develop rapid and simple methods for distinguishing parasitized from non-parasitized larvae in the field. Here we report on a number of diagnostic tools to identify parasitized larvae. One is based on differential melanization reactions in hemolymph due to immune suppression in parasitized larvae. The lack of coagulation reactions in hemolymph provides a simple initial test, where squashing a non-parasitized larva onto nitrocellulose membrane traps chlorophyll-containing gut content on the membrane leaving a green dot of clotted gut material. However, in immune-suppressed parasitized larvae, the gut content was washed away in absence of coagulation reactions and the membrane lacks a green dot. This tool alone or combined with others, allows quick detection of parasitized caterpillars in the field. We further showed that the antibody MAb 9A5 can be used to detect D. semiclausum parasitized larvae of DBM in Western blots.

Molecular methods for assessing insect parasitism

Determining insect parasitism rates is problematic due to the small size and lack of useful distinguishing morphological characters of many parasitoid taxa. To solve this problem, entomologists have employed one of four general methods to detect parasitoid protein or nucleic acid markers: serological assay; random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR); allozyme electrophoresis; or specific PCR. Serological methods, especially with monoclonal antibodies, are unrivalled for specificity, enabling discrimination at the stage as well as species level. However, they have not found favour with many workers, possibly due to complexity and expense. RAPD-PCR has been widely used, but can only be recommended for restricted applications because of its poor reproducibility. Allozyme electrophoresis provides reproducible detection and discrimination of closely related species. Specific-PCR is highly specific and reproducible, and also has the shortest latency for detection, usually 24 h or less after parasitization. The substantial existing literature on allozyme electrophoresis and specific PCR is used to support recommendations on what are apt to be fruitful enzyme systems or genomic regions for detecting and discriminating parasitoids in untried parasitoid-host assemblages.

Proteomic approach for characterization of immunodominant membrane-associated 30- to 36-kiloDalton fraction antigens of Leishmania infantum promastigotes, reacting with sera from Mediterranean visceral leishmaniasis patients

The aim of the present study was to identify and characterize proteins of a 30- to 36-kDa fraction of Leishmania infantum promastigote membranes previously shown to be an immunodominant antigen(s) in Mediterranean visceral leishmaniasis (MVL) and a consistent and reliable serological marker of this disease. By the first approach, Coomassie-stained protein bands (32- and 33-kDa fractions) that specifically reacted by immunoblotting with sera from MVL patients were excised from the gel and submitted to enzymatic digestion to generate peptides. Four peptides were sequenced, three of which were shown to be definitely associated with MVL-reactive antigens and ascribed to a mitochondrial integral ADP-ATP carrier protein from L. major, a putative NADH cytochrome b(5) reductase, and a putative mitochondrial carrier protein, respectively. The second approach combined two-dimensional gel electrophoresis of membrane antigens and mass spectrometry (liquid chromatography-mass spectrometry/mass spectrometry) by using a quadrupole time-of-flight analysis. Six immunoreactive spots that resolved within a molecular mass range of 30 to 36 kDa and a pH range of 6.7 to 7.4 corresponded to four Leishmania products. The sequences derived from two spots were ascribed to a beta subunit-like guanine nucleotide binding protein, known as the activated protein kinase C receptor homolog antigen LACK, and to a probable member of the aldehyde reductase family. One spot was identified as a probable ubiquinol-cytochrome c reductase (EC 1.10.2.2) Rieske iron-sulfur protein precursor. The remaining three spots were identified as truncated forms of elongation factor 1alpha. These antigens correspond to conserved proteins ubiquitously expressed in eukaryotic cells and represent potential candidates for the design of a reliable tool for the diagnosis of this disease.

Monoclonal antibodies to elongation factor-1alpha inhibit in vitro translation in lysates of Sf21 cells

Elongation factor-1alpha (EF-1alpha) is an enzyme that is essential for protein synthesis. Although EF-1alpha offers an excellent target for the disruption of insect metabolism, agents known to interfere with EF-1alpha activity are toxic to humans. In this article, we describe the development of monoclonal antibodies (MAbs) that can disrupt the activity of insect EF-1alpha without cross-reacting with the human enzyme. MAbs were generated to EF-1alpha from Sf21 cells derived from the fall armyworm, Spodoptera frugiperda, by immunizing mice with EF-1alpha eluted from SDS-PAGE gels. The MAbs reacted with EF-1alpha in eggs and first through fifth instars of the fall armyworm in immunoblots of SDS-PAGE gels, but did not recognize EF-1alpha in human carcinoma cells and normal tissues. MAbs with the ability to recognize EF-1alpha in its native conformation, identified through immunoprecipitation experiments, were added to Sf21 cell lysates to determine whether the antibodies could inhibit incorporation of [(35)S]methionine into newly synthesized in vitro translation products. Of the four EF-1alpha-specific MAbs tested, three significantly inhibited protein synthesis when compared to the negative control antibody (P < 0.001, one-way ANOVA; followed by Dunnett's test, P < 0.05).