The Role of AaPGRP-LB in the Immune Response of Aedes albopictus Against Bacteria Infection

The initial phase of an insect's innate immune response to foreign pathogens is triggered by the identification of exogenous invaders, a mechanism facilitated by pattern recognition receptors. Among these receptors, peptidoglycan recognition proteins (PGRPs), abundant in insects, are essential components of the innate immune system. The roles of PGRPs have been extensively elucidated in <i>Drosophila melanogaster</i>; however, the mechanism underlying the immune response of <i>Aedes albopictus</i> to pathogens is unclear. Herein, we successfully cloned the full-length cDNA of a PGRP gene from <i>Ae. albopictus</i>, designated as the <i>AaPGRP-LB</i> gene. The open reading frame of <i>AaPGRP-LB</i> encodes 203 amino acids, including a secretion signal peptide and a canonical PGRP conserved domain. Multisequence alignment revealed that AaPGRP-LB possesses the amino acid residues essential for zinc binding and amidase activity. Molecular docking studies demonstrated that AaPGRP-LB exhibits a strong binding affinity for DAP-type and LYS-type peptidoglycan. The mRNA expression level of the <i>AaPGRP-LB</i> gene significantly increased after oral infection with <i>Escherichia coli</i> or <i>Staphylococcus aureus</i>. The purified recombinant AaPGRP-LB (rAaPGRP-LB) exhibited strong agglutination properties and demonstrated significant antimicrobial efficacy against <i>E. coli</i> and <i>S. aureus</i> in the presence of zinc ions. This study highlights the critical role of AaPGRP-LB in the immune response of <i>Ae. albopictus</i>. These findings provide a foundation for future research on mosquito immune pathways for innovative vector control and disease prevention strategies.