C-Type Lectins Link Immunological and Reproductive Processes in Aedes aegypti

Abstract

Summary Physiological trade-offs between mosquito immune response and reproductive capability can arise due to insufficient resource availability. C-type lectin family members may be involved in these processes. We established a GCTL-3 −/− mutant Aedes aegypti using CRISPR/Cas9 to investigate the role of GCTL-3 in balancing the costs associated with immune responses to arboviral infection and reproduction. GCTL-3 −/− mutants showed significantly reduced DENV-2 infection rate and gut commensal microbiota populations, as well as upregulated JAK/STAT, IMD, Toll, and AMPs immunological pathways. Mutants also had significantly shorter lifespans than controls and laid fewer eggs due to defective germ line development. dsRNA knock-down of Attacin and Gambicin , two targets of the AMPs pathway, partially rescued this reduction in reproductive capabilities. Upregulation of immune response following GCTL-3 knock-out therefore comes at a cost to reproductive fitness. Knock-out of other lectins may further improve our knowledge of the molecular and genetic mechanisms underlying reproduction-immunity trade-offs in mosquitoes.

Transgenic Expression of Human C-Type Lectin Protein CLEC18A Reduces Dengue Virus Type 2 Infectivity in Aedes aegypti

“…The expression of mosquito-specific C-type lectins can influence DENV infection characteristics and success rates both directly and indirectly. For example, AAEL008069 expression decreases DENV replication rates ( 59 ); on the other hand expression of other C-type lectins, such as mosGCTL-3, mosGCTL-15, and mosGCTL-19, can increase DENV replication ( 32 , 43 ).…”

“…Activated Toll, IMD, and JAK/STAT pathways initiate the expression of antimicrobial peptides (AMPs) ( 36 , 37 , 40 ), such as cecropins, defensins, gambicin, diptericin , and attacins , which combat viral infection via many different mechanisms ( 41 , 42 ). The relative importance of different CTLs in modulating these pathways remains relatively unexplored, with different CTLs appearing to play significantly different roles ( 43 ).…”

“…Previous experiments in which immune genes were expressed in Aedes mosquitoes, illustrate the potential opportunities available to not only investigate the influence of the CTLs on mosquito immune responses but also for generating novel transgenic lines to use as vector control tools. This includes the introduction of DENV2 RNAi to inhibit the replication of DENV2 ( 44 ); expression of specific monoclonal antibody single-chain variable fragments to neutralize several DENV serotypes ( 45 ); activation of the JAK/STAT pathway to enhance resistance to DENV infection ( 46 ); and knockdown of mosquito GCTL-3 to reduce DENV2 infection ( 43 ).…”

Generating mutant Aedes aegypti mosquitoes using the CRISPR/Cas9 system

“…Aegypti target gene GCTL-3 (AaegL3_AAEL000535, AaegL5_AAEL029058) as an example for gene knock-in. We have described this process in our recent publication ( Li et al., 2020 ). Note: The original ID of GCTL-3 was AAEL000535 in AaegL3, but has been changed to AAEL029058 with an annotation and assembly in AaegL5.…”

“…We also provide general guidance for establishing mutant mosquito lines. For details on the practical use and execution of this protocol, please refer to Li et al. (2020) .…”