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Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster
Published on: May 13, 2015
Drosophila melanogaster mounts a unique immune response to the Rhabdovirus sigma virus
C W Tsai1, E A McGraw, E-D Ammar
1Department of Entomology, The Ohio State University-OARDC, Wooster, Ohio 44691, USA.
Abstract:
Rhabdoviruses are important pathogens of humans, livestock, and plants that are often vectored by insects. Rhabdovirus particles have a characteristic bullet shape with a lipid envelope and surface-exposed transmembrane glycoproteins. Sigma virus (SIGMAV) is a member of the Rhabdoviridae and is a naturally occurring disease agent of Drosophila melanogaster. The infection is maintained in Drosophila populations through vertical transmission via germ cells. We report here the nature of the Drosophila innate immune response to SIGMAV infection as revealed by quantitative reverse transcription-PCR analysis of differentially expressed genes identified by microarray analysis. We have also compared and contrasted the immune response of the host with respect to two nonenveloped viruses, Drosophila C virus (DCV) and Drosophila X virus (DXV). We determined that SIGMAV infection upregulates expression of the peptidoglycan receptor protein genes PGRP-SB1 and PGRP-SD and the antimicrobial peptide (AMP) genes Diptericin-A, Attacin-A, Attacin-B, Cecropin-A1, and Drosocin. SIGMAV infection did not induce PGRP-SA and the AMP genes Drosomycin-B, Metchnikowin, and Defensin that are upregulated in DCV and/or DXV infections. Expression levels of the Toll and Imd signaling cascade genes are not significantly altered by SIGMAV infection. These results highlight shared and unique aspects of the Drosophila immune response to the three viruses and may shed light on the nature of the interaction with the host and the evolution of these associations.
Insights
The Drosophila innate immune response to Sigma virus (SIGMAV) involves specific antimicrobial peptide genes, unlike responses to other viruses. This reveals unique host-pathogen interactions and immune evasion strategies.
Area of Science:
- Virology
- Immunology
- Genetics
Background:
- Rhabdoviruses are significant pathogens transmitted by insects.
- Sigma virus (SIGMAV) infects Drosophila melanogaster and is vertically transmitted.
- Understanding Drosophila's innate immunity is crucial for pathogen research.
Purpose of the Study:
- To investigate the Drosophila innate immune response to SIGMAV infection.
- To compare the immune response to SIGMAV with that of nonenveloped viruses (DCV, DXV).
- To identify specific genes and pathways involved in the host response.
Main Methods:
- Microarray analysis to identify differentially expressed genes.
- Quantitative reverse transcription-PCR (qRT-PCR) to validate gene expression.
- Comparison of gene expression profiles across different viral infections.
Main Results:
- SIGMAV infection upregulated specific peptidoglycan receptor protein (PGRP) genes (PGRP-SB1, PGRP-SD) and antimicrobial peptide (AMP) genes (Diptericin-A, Attacin-A/B, Cecropin-A1, Drosocin).
- SIGMAV did not induce certain AMP genes (Drosomycin-B, Metchnikowin, Defensin) or alter Toll and Imd signaling pathways, unlike DCV/DXV infections.
- Distinct immune responses were observed between SIGMAV and nonenveloped viruses.
Conclusions:
- Drosophila exhibits a unique innate immune response to SIGMAV, involving a specific set of PGRP and AMP genes.
- The Toll and Imd pathways appear less involved in the SIGMAV response compared to other viral infections.
- These findings illuminate host-pathogen interactions and the evolution of viral associations in Drosophila.
