Modulation of immune system gene expression in Rhinella toads submitted to an immunological challenge with lipopolysaccharide (LPS) and heat-killed bacteria (Aeromonas hydrophila)

• Grant number: 21/14134-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: April 01, 2023
• End date: January 31, 2026
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Fernando Ribeiro Gomes
• Grantee: Felipe Rangel Floreste
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated scholarship(s): 23/06734-8 - Host-parasite immune dynamics in the range-expanding invasive cane toads (Rhinella marina), BE.EP.DD

Abstract

The ongoing populational decline of amphibians has been widely documented in the last decades. Frequently, such decline has been associated with neuro-immune-endocrine interactions to explain the fragilization of the amphibian immune system dealing with potential stressors (such as habitat fragmentation and new pathogens). Therefore, a detailed characterization of their inflammatory response in different organs is necessary, integrating the temporal dynamics of immune system components and immunomodulator hormones secretion (corticosterone - CORT, testosterone - T, melatonin - MEL). This project aims to characterize the time course of immune genes expression and immunomodulator hormones secretion during the first hours of an inflammatory response in anurans. We also aim to explore daily variations between the immune response during day and night. For that, we used lipopolysaccharide (LPS) to mimic a bacterial infection in Rhinella toads while tracking plasma hormone levels (CORT, T, MEL), related gene markers (AANAT and Asmt), and immune genes expression (cytokines, receptors, acute-phase proteins, signaling proteins) in the spleen, liver and eyes of individuals. Moreover, a transcriptome of the main immune tissues (spleen and liver) will be executed in Rhinella toads after an injection with heat-killed bacteria (Aeromonas hydrophila), offering a comprehensive overview of the gene expression alterations during the infection. Our preliminary results show differential expression of cytokines and complement system proteins between the spleen and the liver during the first 18 hours of the immune challenge. In the future, we will explore variations between the inflammatory response during the day and at night in toads, measuring mRNA levels of immune system components and using ocular tissue to investigate the gene expression of MEL-synthetizing enzymes. (AU)