Development of monoclonal antibody based antigen capture ELISA to detect chikungunya virus antigen in mosquitoes.

BACKGROUND & OBJECTIVES: Chikungunya (CHIK) virus has caused numerous large outbreaks in India. No active or passive surveillance has been carried out since the last epidemic which occurred in 1971. For active surveillance, it is necessary to have a test, which can detect the virus from a large number of field-collected mosquitoes. METHODS: The present study describes the standardization of monoclonal antibody (MAb) based antigen capture ELISA to detect chikungunya virus antigen from the mosquitoes. CHIK virus antigen from suspension of experimentally infected mosquitoes and their progeny was captured on mouse polyclonal antibody, while biotinylated CHIK Mab was used as a probing antibody. CHIK virus antigen in the head squashes of virus inoculated mosquitoes was detected using indirect immunofluorescence antibody (IFA) test for confirmation of ELISA results. RESULTS: The ELISA test was sensitive enough to detect antigen even if a small fraction of a single infected mosquito homogenate was incorporated in the test. The IFA test failed to detect CHIK antigen in 10 and 25 microliters of suspension whereas with ELISA it was detected in all the samples. Progeny of Aedes aegypti and Ae. albopictus mosquitoes infected with chikungunya virus did not show the possibility of existence of transovarial transmission. INTERPRETATION & CONCLUSION: This test is rapid and simple since it can be completed in two days as compared to the conventional mosquito inoculation and IFA techniques, which require at least 10 days. There is an additional advantage with this test that a large number of samples can be processed, and the remaining homogenate of the mosquitoes can be used for screening other viruses. Experimental data raised using this test showed that transovarial transmission of this virus does not occur in these vector species.

Exploring the glycan repertoire of genetically modified mice by isolation and profiling of the major glycan classes and nano-NMR analysis of glycan mixtures.

The production of mice with genetic alterations in glycosyltransferases has highlighted the need to isolate and study complex mixtures of the major classes of oligosaccharides (glycans) from intact tissues. We have found that nano-NMR spectroscopy of whole mixtures of N- and O-glycans can complement HPLC profiling methods for elucidating structural details. Working toward obtaining such glycan mixtures from mouse tissues, we decided to develop an approach to isolate not only N- and O-glycans, but also to separate out glycosphingolipids, glycosaminoglycans and glycosylphosphatidylinositol anchors. We describe here a comprehensive Glycan Isolation Protocol that is based primarily upon the physicochemical characteristics of the molecules, and requires only commonly available reagents and equipment. Using radiolabeled internal tracers, we show that recovery of each major class of glycans is as good or better than with conventional approaches for isolating individual classes, and that cross-contamination is minimal. The recovered glycans are of sufficient purity to provide a "glycoprofile" of a cell type or tissue. We applied this approach to compare the N- and O-glycans from wild type mouse tissues with those from mice genetically deficient in glycosyltransferases. N- and O-glycan mixtures from organs of mice deficient in ST6Gal-I (CMP-Sia:Galbeta1-4GlcNAc alpha2-6 sialyltransferase) were studied by the nano-NMR spectroscopy approach, showing no detectable alpha2-6-linked sialic acids. Thus, ST6Gal-I is likely responsible for generating most or all of these residues in normal mice. Similar studies indicate that this linkage is very rare in ganglioside glycans, even in wild-type tissues. In mice deficient in GalNAcT-8 (UDP-GalNAc:polypeptide O-Ser/Thr GalNAc transferase 8), HPLC profiling indicates that O-glycans persist in the thymus in large amounts, without a major change in overall profile, suggesting that other enzymes can synthesize the GalNAc-O-Ser/Thr linkage in this tissue. These results demonstrate the applicability of nano-NMR spectroscopy to complex glycan mixtures, as well as the versatility of the Glycan Isolation Protocol, which makes possible the concurrent examination of multiple glycan classes from intact vertebrate tissues.

Plasma lactic dehydrogenase in mice infected with Japanese encephalitis & West Nile viruses.

A study of the total and isoenzymes fractions of lactic dehydrogenase (LDH) enzyme was carried out in the plasma of mice infected with Japanese encephalitis (JE) and West Nile (WN) viruses. Only 2 isoenzymes (LDH 4 and LDH 5) were present in control mice. There was a rapid increase of total LDH in the animals infected with the wild strain of viruses. Mice infected with wild strains of JE showed all 5 isoenzymes. LDH 1 disappeared after 12 days of infection but LDH 2 and LDH 3 persisted for 3 wk. The attenuated strain of JE did not produce any change either of the total content of the enzyme or of the isoenzyme pattern. In the plasma of mice infected with wild strains of WN viruses only 4 isoenzyme bands (LDH 2, 3, 4, 5) were detected. The LDH 3 persisted longer than LDH 2. With one strain of WN virus an extra band near LDH 4 was seen.

The effect of alkaline borohydride treatment on N-linked carbohydrates of glycoproteins.

The effects of treatments of the glycoprotein ribonuclease-B, the proteins ribonuclease-A and myoglobin, and the glyco-amino acid GlcNAc beta(1-N)Asn with alkali, alkaline sodium borohydride, and aqueous sodium borohydride were systematically studied as a function of the concentration of the reagents, the temperature, and the length of the treatment. High-field 1H-NMR spectroscopy, chromatographic methods and amino-acid analysis were used to characterize products of the treatments of the various compounds. Our results indicate that mild alkaline borohydride treatment, as well as aqueous borohydride treatment alone, is capable of extensively degrading polypeptides and of partially releasing the N-linked glycans from ribonuclease-B. Initially, glycopeptides are produced, the peptide portion of which consists of several amino acids, which are further hydrolyzed to yield a mixture of glyco-asparagines and oligosaccharide-alditols in the ratio of approximately 4:1. Strong alkaline borohydride treatment of ribonuclease-B is capable of completely releasing the N-linked carbohydrates as oligosaccharide-alditols.

Structural studies on the carbohydrate moieties of human liver alpha-L-fucosidase.

alpha-L-Fucosidase was purified from human liver to apparent homogeneity and subjected to exhaustive digestion with Pronase. The resulting glycopeptides were isolated by gel filtration on Sephadex G-50 and further fractionated by Bio-Gel P-4 chromatography. Five glycopeptide fractions were obtained. The structures of the carbohydrate portions of all glycopeptide components were fully characterized by a combination of 500-MHz 1H NMR spectroscopy and carbohydrate composition analysis. Fraction I contained disialyl diantennary glycopeptides of the N-acetyllactosamine type. Fractions II and III contained predominantly mono(sialyl-N-acetyllactosaminyl) diantennary glycopeptides with the NeuAc alpha(2----6)Gal beta(1----4)GlcNAc beta(1----2) branch attached to alpha(1----3)-linked Man in II and to alpha(1----6)-linked Man in III. The N-acetyllactosamine-type glycopeptides in fractions I to III have a small portion (10-15%) of their Asn-linked GlcNAc residues substituted by additional alpha(1----6)-linked Fuc. Also, a minor portion of the NeuAc residues appeared to be attached to Gal in alpha(2----3) rather than alpha(2----6) linkage. Fraction IV contained a mixture of larger-size oligomannoside-type glycopeptides with a variable number (6 to 9) of Man residues. Smaller-size oligomannoside-type glycopeptides were found in fraction V, containing 3 or 5 Man residues; a small portion (10%) of the Man3GlcNAc2Asn component appeared to contain in addition a Fuc residue in alpha(1----6) linkage to the Asn-bound GlcNAc. The overall ratio of oligomannoside-type to N-acetyllactosamine-type carbohydrate structures was found to be 5:4. This article is the first account of the complete characterization of the oligomannoside-type structures in alpha-L-fucosidase; furthermore, the occurrence in alpha-L-fucosidase of mono(sialyl-N-acetyllactosaminyl) structures, Fuc-containing oligosaccharides, and NeuAc alpha(2----3) linked to Gal are reported for the first time.