# Aptamer selection against cell extracts containing the zoonotic obligate intracellular bacterium, Anaplasma phagocytophilum

## TL;DR

Researchers developed DNA aptamers to study the tick-borne bacterium Anaplasma phagocytophilum, which is hard to study due to its intracellular nature.

## Contribution

The study presents a novel method to select DNA aptamers against A. phagocytophilum using a customized SELEX protocol.

## Key findings

- Three DNA aptamers with high affinity for A. phagocytophilum-infected cells were successfully selected.
- The aptamers likely target proteins expressed at different stages of infection.
- The aptamers could aid in understanding host-bacterium interactions and developing new diagnostics or therapies.

## Abstract

A. phagocytophilum is a zoonotic and tick-borne bacterium, threatening human and animal health. Many questions persist concerning the variability of strains and the mechanisms governing the interactions with its different hosts. These gaps can be explained by the difficulty to cultivate and study A. phagocytophilum because of its strict intracellular location and the lack of specific tools, in particular monoclonal antibodies, currently unavailable. The objective of our study was to develop DNA aptamers against A. phagocytophilum, or molecules expressed during the infection, as new study and/or capture tools. Selecting aptamers was a major challenge due to the strict intracellular location of the bacterium. To meet this challenge, we set up a customized selection protocol against an enriched suspension of A. phagocytophilum NY18 strain, cultivated in HL-60 cells. The implementation of SELEX allowed the selection of three aptamers, characterized by a high affinity for HL-60 cells infected with A. phagocytophilum NY18 strain. Interestingly, the targets of these three aptamers are most likely proteins expressed at different times of infection. The selected aptamers could contribute to increase our understanding of the interactions between A. phagocytophilum and its hosts, as well as permit the development of new diagnostic, therapeutic or drug delivery appliances.