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Anaplasma phagocytophilum-induced gene expression in both human neutrophils and HL-60 cells
Hin C Lee1, Mitomu Kioi, Jing Han
1Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
Abstract:
Anaplasma phagocytophilum (Ap), the etiologic agent of the tick-borne disease human granulocytic anaplasmosis, is an obligate intracellular pathogen unique in its ability to target and replicate within neutrophils. We define and compare the spectra of host gene expression in response to Ap infection of human neutrophils and of HL-60 cells using long (70-mer)-oligonucleotide array technology. In addition to apoptosis-related genes, genes involved in signaling pathways, transcriptional regulation, immune response, host defense, cell adhesion, and cytoskeleton were modulated in neutrophils infected with Ap. Ap infection affected the same pathways in HL-60 cells but transcriptional changes occurred more slowly and in a reduced spectrum of genes. Gene expression changes detected by microarray were confirmed for randomly selected genes by QRT-PCR and Western blot studies. These studies demonstrate for the first time that the ERK pathway is activated in Ap-infected neutrophils and also define multiple pathways that are activated during intracellular Ap infection, which together serve to prolong the cell survival that is needed to allow bacterial replication and survival in neutrophils, which otherwise would rapidly apoptose.
Insights
Anaplasma phagocytophilum (Ap) manipulates host neutrophils to survive by activating specific gene pathways. This tick-borne pathogen prolongs neutrophil survival, enabling its replication and persistence within these immune cells.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Anaplasma phagocytophilum (Ap) causes human granulocytic anaplasmosis, a tick-borne illness.
- Ap is an obligate intracellular pathogen that specifically infects neutrophils.
Purpose of the Study:
- To compare host gene expression changes in human neutrophils and HL-60 cells upon Ap infection.
- To identify host pathways modulated by Ap infection that facilitate pathogen survival.
Main Methods:
- Utilized 70-mer oligonucleotide arrays to analyze gene expression.
- Confirmed microarray findings using quantitative reverse transcription PCR (QRT-PCR) and Western blot analysis.
Main Results:
- Ap infection modulated genes involved in apoptosis, signaling, transcription, immune response, cell adhesion, and cytoskeleton in neutrophils.
- Similar pathways were affected in HL-60 cells, but with delayed and reduced transcriptional changes.
- Demonstrated ERK pathway activation in Ap-infected neutrophils.
Conclusions:
- Ap infection activates multiple host pathways, including the ERK pathway, to prolong neutrophil survival.
- This prolonged survival is crucial for Ap replication and persistence within neutrophils, preventing premature host cell apoptosis.
