The genus Anaplasma: drawing back the curtain on tick-pathogen interactions

Abstract

Tick-borne illnesses pose a serious concern to human and veterinary health and their prevalence is on the rise. The interactions between ticks and the pathogens they carry are largely undefined. However, the genus Anaplasma, a group of tick-borne bacteria, has been instrumental in uncovering novel paradigms in tick biology. The emergence of sophisticated technologies and the convergence of entomology with microbiology, immunology, metabolism and systems biology has brought tick-Anaplasma interactions to the forefront of vector biology with broader implications for the infectious disease community. Here, we discuss the use of Anaplasma as an instrument for the elucidation of novel principles in arthropod-microbe interactions. We offer an outlook of the primary areas of study, outstanding questions and future research directions.

Keywords: Anaplasma; arthropod vectors; ehrlichia; orientia; rickettsia; tick-borne diseases.

Figure 1.

Current research topics in tick–Anaplasma phagocytophilum interactions. Survival: Anaplasma phagocytophilum confers survival advantages to the tick by promoting cold tolerance. Metabolic reprogramming: A. phagocytophilum manipulates tick metabolic processes to promote colonization. Immunity: A. phagocytophilum activates the tick immune deficiency (IMD) pathway through lipids derived from infection. Microbiome: A. phagocytophilum disrupts the tick microbiome and alters biofilm formation to enable colonization. Saliva: tick saliva limits inflammation and wound healing at the bite site, which may facilitate A. phagocytophilum transmission. CXCL12: C-X-C motif chemokine 12; IAFGP: I. scapularis antifreeze glycoprotein; SL2: sialostatin L2.

Figure 2.

Cutting-edge technologies in tick-Anaplasma spp. research. Spatially resolved transcriptomics: couples transcriptome sequencing with microscopy for visualizing expression changes in tissues [shown: Spatial Transcriptomics (Ståhl et al. 2016)]. Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene editing: draws on principles of non-homologous end joining (NHEJ) and homology directed repair (HDR) to introduce loss-of-function mutations or edited DNA, respectively. Metabolomics: identifies changes in metabolites using nuclear magnetic resonance (NMR) or mass spectrometry (MS). Single cell RNA sequencing (scRNA-seq): transcriptomes of individual cells are sequenced for uncovering population heterogeneity. 16S ribosomal RNA (rRNA) sequencing: bacterial species are identified through sequencing of the bacterial16S rRNA gene.