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Elizabethkingia meningoseptica is Gram-negative, rod-shaped opportunistic bacterial pathogen increasingly reported in hospital-acquired outbreaks. This bacterium is well known to thrive in...

Eye disorders and resulting visual loss are major public health problems affecting millions of people worldwide. In this context, the sclera is an opaque, thick outer coat covering more than 80% of the eye, and essential in maintaining the shape of the eye and protecting the intraocular contents against infection and the external environment. Despite efforts undertaken to decipher the scleral proteome, the functional and structural picture of the sclera still remain elusive. Recently, proteomics has arisen as a powerful tool that enables identification of proteins playing a critical role in health and disease. Therefore, we carried out an in-depth proteomic analysis of the human scleral tissue using a high-resolution Orbitrap Fusion Tribrid mass spectrometer. We identified 4493 proteins using SequestHT and Mascot as search algorithms in Proteome Discoverer 2.1. Importantly, the proteins, including radixin, synaptopodin, paladin, netrin 1, and kelch-like family member 41, were identified for the first time in human sclera. Gene ontology analysis unveiled that the majority of proteins were localized to the cytoplasm and involved in cell communication and metabolism. In sum, this study offers the largest catalog of proteins identified in sclera with the aim of facilitating their contribution to diagnostics and therapeutics innovation in visual health and autoimmune disorders. This study also provides a valuable baseline for future investigations so as to map the dynamic changes that occur in sclera in various pathological conditions.

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.

Insects sustain the invading bacterial pathogens by inducing the production of lectin which participates in surveillance of non-self molecules. The antibacterial property of lectin is an inevitable aspect of innate immune system especially for the insects feeding the detritus organic matter. β-galactoside binding lectin possessing antibacterial property was detected and purified from the hemolymph of larvae of caddisfly, Stenopsyche kodaikanalensis using affinity chromatography. The purified lectin exhibited highest hemagglutination titer value against buffalo erythrocytes and has affinity to lactose and fetuin which contains β-galactoside linkages. It was found to be calcium independent, EDTA insensitive and heat labile. These reveal the characteristics features of S-Lac lectin. The molecular weight of lectin was 360 kDa with five distinct subunits such as 95, 90, 66, 62 and 47 kDa. The sequences acquired through MALDI-TOF-MS analysis shared homologies to the putative conserved region of leguminous lectin. Antibacterial studies were carried out with native soil bacterial isolates. It revealed that the lectin possessed the specific modes of action against bacteria that it can agglutinate the Bacillus subtilis and lyse the Bacillus flexus.

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.