Hemolytic activity is mediated by the endogenous lectin in the mosquito hemolymph serum

Purification and structural characterization of lectin with antibacterial and anticancer properties from grubs of hide beetle, Dermestes frischii

Lectins or haemagglutinins are diverse classes of non-immune proteins; they bind to carbohydrates and are abundant in nature. In the present study, a coleopteran lectin from grubs of hide beetle, Dermestes frischii called DFL, was purified by glutaraldehyde (fixative-agent) fixed hen erythrocytes and characterized further for its functional properties. The purified DFL was stable between pH range 5 to 9 and heat-stable up to 50C. It was insensitive to EDTA and did not require any divalent cations. DFL native molecular mass was approximately 69 kDa with three different polypeptide subunits of 33 (pI ~4.4), 22 (pI ~6) and 14 (pI ~4.4) kDa. Haemagglutinating activity of DFL was highly inhibited by N-acetyl-D-glucosamine. DFL partial peptide sequences obtained from peptide mass fingerprinting experiments matched with amino acid sequences of lectins from different organisms confirmed its nature. Biological properties of purified DFL namely antibacterial and bacterial agglutination experiments revealed that DFL have both the effects against laboratory cultures of Aeromonas hydrophila, Enterococcus faecalis, Escherichia coli and habitat bacterial isolates of Staphylococcus cohnii and Bacillus cereus. In addition, the DFL exhibited substantial anticancer properties against HeLa cells. These results concluded that purified DFL could serve as a potent therapeutic agent for various biomedical applications.

Identification and Physicochemical Properties of the Novel Hemolysin(s) From Oral Secretions of Helicoverpa armigera (Lepidoptera: Noctuidae)

Hemolysins cause the lysis of invading organisms, representing major humoral immunity used by invertebrates. Hemolysins have been discovered in hemolymph of Helicoverpa armigera larvae as immune factors. As oral immunity is great important to clear general pathogens, we presumed that hemolysins may be present in oral secretions (OS). To confirm this hypothesis, we conducted four testing methods to identify hemolysin(s) in larval OS of H. armigera, and analyzed physicochemical properties of the hemolysin in comparison with hemolytic melittin of Apis mellifera (L.) (Hymenoptera: Apidae) venom. We found hemolysin(s) from OS of H. armigera for the first time, and further identified in other lepidopteran herbivores. It could be precipitated by ammonium sulfate, which demonstrates that the hemolytic factor is proteinaceous. Labial gland showed significantly higher hemolytic activity than gut tissues, suggesting that hemolysin of OS is mainly derived from saliva secreted by labial glands. Physicochemical properties of hemolysin in caterpillar's OS were different from bee venom. It was noteworthy that hemolytic activity of OS was only partially inhibited even at 100°C. Hemolytic activity of OS was not inhibited by nine tested carbohydrates contrary to bee venom melittin. Moreover, effects of metal ions on hemolytic activity were different between OS and bee venom. We conclude that there is at least a novel hemolysin in OS of herbivorous insects with proposed antibacterial function, and its hemolytic mechanism may be different from melittin. Our study enriches understanding of the potential role of hemolysins in insect immunity and provides useful data to the field of herbivorous insect-pathogen research.

Constitutive expression and discovery of antimicrobial peptides in Zygogramma bicolorata (Coleoptera: Chrysomelidae)

The expression, identification, and discovery of less toxic antimicrobial peptides (AMPs) are significant in managing infectious pathogens. AMPs triggered in response to the immune system have evolved to defend against pathogens and wounding. The protein composition of Zygogramma bicolorata hemolymph is of diagnostic importance as the open circulatory systems of the insects involve signaling through hemolymph. They have conserved many ancestral vertebrate genes that may help better understand the evolution of innate immunity. The present work describes the isolation, purification, identification, and bioinformatics analysis of AMPs from the immunized hemolymph of Z. bicolorata. Thirty-nine peptides were isolated from reverse-phase high-performance liquid chromatography and sequenced via mass spectrometry analysis. The immunization process recorded a threefold higher protein concentration in immunized hemolymph when compared with nonimmunized one. For the first time, the proteomic study on Z. bicolorata hemolymph unveils the three novel proteins in the family Chrysomelidae with no homology in the database, indicating its novelty and the expression of the rest of 36 well-known proteins, including heat-shock, immune, structural, signaling proteins, and others speak for its method validity. Combining the expression of novel AMPs, detoxifying enzymes, hemolytic, and cytotoxic assays, and this work can elucidate new pathways to immune response mechanisms. Its molecular basis also holds the potential applicability in the future drug development process against pathogenic fungi such as Aspergillus niger and Candida albicans.

A serine protease-associated lectin in the cytolytic system of blowfly (Chrysomya megacephala) larvae: Evidence and characterization

Cytolytic activity against invading microorganisms is one of the innate forms of immunity in invertebrates. A serine protease-associated sialic acid-specific cytolytic lectin was purified using glutaraldehyde-fixed ox erythrocytes from the larval extract of blowfly (Chrysomya megacephala). The purified lectin lysed vertebrate erythrocytes with effective haemolysis of ox red blood cells (RBCs) in an isotonic medium. The degree of haemolytic (HL) activity of the purified cytolytic lectin depended on its concentration, pH, temperature, and calcium ions. It was sensitive to ethylenediaminetetraacetic acid. The native molecular mass of the C-type lectin was 260 ± 26 kDa, comprising four different polypeptide subunits of 75 kDa (pI ~8), 69 kDa (pI ~7.0), 61 kDa (pI ~5.3), and 55 kDa (pI ~4.6). The association between the C-type lectin and serine protease was confirmed by MALDI-TOF-MS analysis that revealed its homology in the same spectral peak as well as the proteases and phenylmethylsulphonyl fluoride inhibition of HL activity. Haemolysis inhibition by N-acetylneuraminic acid and other sugars revealed the properties of the lectin. The purified lectin distorted the integrity of ox RBCs and Paenalcaligenes hermetiae. This in vitro study documents the presence of a cytolytic system in blowfly (C. megacephala) larvae for the clearance of invading microbial pathogens in their feeding niche.

Purification and functional characterization of lectin with phenoloxidase activity from the hemolymph of cockroach, Periplaneta americana

Lectins also identified as hemagglutinins are multivalent proteins and on account of their fine sugar-binding specificity play an important role in immune system of invertebrates. The present study was carried out on the hemolymph lectin of cockroach, Periplaneta americana with appropriate screening and purification to understand its molecular as well as functional nature. The lectin from the hemolymph was purified using ion-exchange chromatography. The approximate molecular weight of purified lectin was 340 kDa as determined by FPLC analysis. Rabbit erythrocytes were highly agglutinated with purified lectin from the hemolymph of P. americana. The hemagglutination activity (HA) of lectin was specifically inhibited by fucose. Glycoproteins also inhibited the HA activity of lectin. The amino acid sequences of the purified lectin revealed homology with amino acid sequences of allergen proteins from P. americana. Purified lectin showed the highest phenoloxidase activity against dopamine. The activators such as exogenous proteases and LPS from Escherichia coli and Salmonella minnesota significantly enhanced the PO activity of the purified lectin. Besides, the presence of copper and hemocyanin conserved domain in the purified lectin provided a new facet that insects belonging to the ancient clade such as cockroaches retained some traces of evolutionary resemblance in possessing lectin of ancient origin.

THE ENDOPARASITOID Campoletis chlorideae INDUCES A HEMOLYTIC FACTOR IN THE HERBIVOROUS INSECT Helicoverpa armigera

Although lysis of invading organisms is a major innate form of immunity used by invertebrates, it remains unclear whether herbivorous insects have hemolysin or not. To address this general question, we tested the hemolytic (HL) activity of the hemolymph and tissue extracts from various stages of the polyphagous insect Helicoverpa armigera (Hübner) against the erythrocytes from chicken, duck, and rabbit. An HL activity was identified in the hemolymph of H. armigera larvae. Further studies demonstrated that the HL activity is proteinaceous as it was precipitable by deproteinizing agents. Hemolysins were found in Helicoverpa egg, larva, pupa, and adult, but the activity was higher in feeding larvae than in molting or newly molted larvae. Hemolysins were distributed among a variety of larval tissues including salivary gland, fat body, epidermis, midgut, or testes, but the highest activity was found in salivary gland and fat body. Relative to nonparasitized larvae, parasitization of H. armigera larvae by the endoparasitoid Campoletis chlorideae Uchida induced a 3.4-fold increase in the HL activity in the plasma of parasitized host at day two postparasitization. The present study shows the presence of a parasitoid inducible HL factor in the parasitized insect. The HL activity increased significantly in H. armigera larvae at 12 and 24 h postinjection with Escherichia coli. We infer the HL factor(s) is inducible or due to de novo synthesis, which means that the HL factor(s) is associated with insect immune response by inhibiting or clearance of invading organisms.

Establishment and characterization of two new cell lines from the mosquito Armigeres subalbatus (Coquillett) (Diptera: Culicidae)

Armigeres subalbatus (Coquillett) is a medically important mosquito and a model species for immunology research. We successfully established two cell lines from the neonate larvae of A. subalbatus using two different media. To our knowledge, this is the first report of an established Armigeres mosquito cell line. The cell lines, designated as Ar-3 and Ar-13, consist of adherent and diploid cells with compact colonies. Both these cell lines grow slowly after passage at a split ratio of 1:5 and a population doubling time of 2.7 and 3.0 d, respectively. Random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was used to confirm that these lines correspond to the species of origin and are clearly distinct from seven other insect cell lines. Furthermore, reverse-transcription PCR was used to demonstrate that the Ar-3 cell line is susceptible to the Japanese encephalitis virus and two insect flaviviruses associated with Culex and Aedes mosquitoes but relatively insensitive to dengue virus. These data indicate that the newly established cell lines are cellular models of A. subalbatus as well as beneficial tools for the propagation of viruses associated with the Armigeres mosquito.