Isolation of midgut agglutinin of Culex quinquefasciatus ( Diptera , Culicidae)

Document Type : Original Article

Author

Entomology Department, Faculty of Science, Cairo University

Abstract

A Lectin that agglutinates Eschrechia coli (ATCC 25922) , Staphylococcus aureus (ATCC 6538) live bacteria and various  mammalian red blood  cells (RBCs)  was identified in Culexquinquefasciatus midgut extract ( Cqlec) by using human (three groups: A, B,  and O, RH+)mouse, rat, guinea-pig, rabbit  and goat erythrocytes. With the use of (NH4)2 SO4 fractionation, anion - exchange and GluNA -CBr-Sepharose 6B affinity chromatography, C.quinquefasciatus mid gut lectin has been purified to homogeneity. IEF and reducing SDS/PAGE revealed that the isolated mid gut lectin have isoelectric point (PI) of 6.30, and a subunit approximate molecular weight of 34.5 KDa .The highest agglutination activity of crude and isolated Cqlec   were detected against both Eschrechia coli cells and rabbit RBCs. Significant differences in hemagglutinin titers and carbohydrate inhibition were detected between sugar fed and blood fed  adult female mosquitoes.Overall agglutinin levels were increased following a blood meal feeding  and E. coli induction using a hypodermic needle. This study presents the first report on the occurrence of heterogeneous anti rabbit RBC agglutinins in the midgut extracts of C.quinquefasciatus from Al kharj area in Saudi Arabia. The HA of lectins are Ca2+independent, heat-resistant, and are strongly inhibited by D(+)-mannose and D(+) glucose  followed by N-acetyl-D-glucosamine. Raffinose and N-acetyl-D-manosamine were found to be moderate inhibitors. Non of the lectins were inhibited by galactose , lactose , trehalose or fetuin (1%) but the glycosubstances mucin and laminarin showed strong inhibitition using low concentrations . 2D-NMR spectroscopy revealed a component of the corresponding residue in structure having group regions of  resolution spectrum of  Man9- GlcNAc2Asn.

Keywords