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.

Antiviral activity of seselin from Aegle marmelos against nuclear polyhedrosis virus infection in the larvae of silkworm, Bombyx mori

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Indian medicine has utilized Aeglemarmelos (L.) Corr. commonly called as bael in several indigenous systems against various diseases. Bioactive components isolated from various plant parts of A. marmelos were used in ethno-medicine. More precisely they are known for its antiviral property against various human and animal viruses.

AIM OF THE STUDY

The study was conducted to investigate the antiviral activity of A.marmelos against Bombyx mori nucleopolyhedrovirus (BmNPV).

MATERIALS AND METHODS

Among the various crude extracts tested, hexane extracts of leaves of A. marmelos with promising anti-BmNPV activity was subjected to bioactivity guided fractionation based on column chromatography. Out of 40 fractions obtained from the fractionation, fractions showing similar TLC profiles were pooled into 14 fractions. A fraction with potential activity was used to purify a molecule with anti-BmNPV activity. This molecule was characterized through structural and functional analyses.

RESULTS

The functionally and structurally characterized molecule in the fraction with prospective anti-BmNPV activity revealed a single crystal compound 'seselin' (8, 8-dimethyl pyrido oxazine-2-one).

CONCLUSION

It is therefore understood that this seselin compound could be used as a natural medicine for the management of NPV infection in the silkworm larvae under commercial conditions after suitable field evaluations.