Bursicon homodimers enhance the expression of innate immune genes and delay WSSV-induced mortality in Litopenaeus vannamei

Bursicon (burs) is a neuropeptide hormone composing of α and β heterodimeric subunits (bursα and bursβ) that regulates various physiological processes during development and reproduction in insects and crustaceans. Recently, the homodimeric form of bursicon has been demonstrated for its possible function in immune response by activating several antimicrobial peptide (AMP) genes in crustaceans. This study aims to investigate the function of bursα and bursβ homodimers in the Pacific white shrimp, Litopenaeus vannamei with a hypothesis that Lvbursα and Lvbursβ function in the activation of AMP gene expression and inhibit viral replication in L. vannamei. The cDNAs encoding Lvbursα and Lvbursβ were amplified and characterized. Lvbursα and Lvbursβ were specifically expressed in neuronal tissues with the high expression level in thoracic ganglia, and were upregulated during white spot syndrome virus (WSSV) challenge. Functional analysis of recombinant Lvbursα and Lvbursβ revealed that both proteins significantly activate the transcription of key genes involved in multiple immune-related signaling pathways and AMP genes, including Dorsal, Relish, IKK-β, ProPO1, Crustin, ALF, and Pen3. Pre-treatment with either Lvbursα or Lvbursβ prior to WSSV challenge exhibited a delay in cumulative mortality, indicating their antiviral potential. These results suggested that Lvbursα and Lvbursβ homodimers play a significant role in innate immune response by enhancing multiple immune-related pathways. These findings provide evidence supporting the role of homodimeric bursicon in innate immune modulation and highlight its potential relevance in enhancing resistance to viral infection in crustaceans.