# Potential Involvement of the South American Lungfish Intelectin-2 in Innate-Associated Immune Modulation

## TL;DR

This study explores how a protein called LpITLN2-B in the South American lungfish may help defend against pathogens by interacting with sugars.

## Contribution

The study identifies and characterizes LpITLN2-B, a novel intelectin in lungfish, revealing its structural and functional role in immune defense.

## Key findings

- LpITLN2-B is a trimeric protein with a fibrinogen-like domain and a molecular mass of 57 kDa.
- Molecular docking shows LpITLN2-B interacts preferentially with disaccharides over monosaccharides.
- Hemagglutination assays confirm lectin activity inhibition by maltose and sucrose in lungfish samples.

## Abstract

Intelectins belong to a family of lectins with specific and transitory carbohydrate interaction capabilities. These interactions are related to the activity of agglutinating pathogens, as intelectins play a significant role in immunity. Despite the prominent immune defense function of intelectins, limited information about its structural characteristics and carbohydrate interaction properties is available. This study investigated an intelectin transcript identified in RNA-seq data obtained from the South American lungfish (Lepidosiren paradoxa), namely LpITLN2-B. The structural analyses predicted LpITLN2-B to be a homo-trimeric globular protein with the fibrinogen-like functional domain (FReD), exhibiting a molecular mass of 57 kDa. The quaternary structure is subdivided into three monomers, A, B, and C, and each domain comprises 11 β-sheets: an anti-parallel β-sheet, a β-hairpin, and a disordered β-sheet structure. Molecular docking demonstrates a significant interaction with disaccharides rather than monosaccharides. The preferential interaction with disaccharides highlights the potential interaction with pathogen molecules, such as LPS and Poly(I:C). The hemagglutination assay inhibited lectins activity, especially maltose and sucrose, highlighting lectin activity in L. paradoxa samples. Overall, our results show the potential relevance of LpITLN2-B in L. paradoxa immune defense against pathogens.