The Novel Zoonotic Pathogen, Anaplasma capra, Infects Human Erythrocytes, HL-60, and TF-1 Cells In Vitro.

Yongshuai Peng,Pihong Gong,Rongjun Wang,Jinxing Song,Fuchun Jian,Longxian Zhang,Yaqun Yan,Chenyang Lu,Zhiyang Pei,Changshen Ning

doi:10.3390/pathogens10050600

Yongshuai Peng, Pihong Gong + Show 8 more

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https://doi.org/10.3390/pathogens10050600

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Abstract

Anaplasma capra, a species of the family Anaplasmataceae, is zoonotic tick-borne obligate intracellular bacteria. There have been no reports of human infection with this pathogen since 2015. Therefore, the zoonotic characteristics of A. capra need to be further studied. To verify the ability of A. capra to infect human cells, A. capra were inoculated in human erythrocytes, HL-60, and TF-1 cell lines in vitro. Cell smears were taken after inoculation, using Giemsa staining, transmission electron microscope (TEM), chromogenic in situ hybridization and immunocytochemistry for detection. In the Giemsa staining, many dark colored corpuscles or purple granules were seen in the inoculated erythrocytes, HL-60, and TF-1 cells. The results of chromogenic in situ hybridization show that there were brown precipitates on the surface of most erythrocytes. Immunocytochemistry results show many dark brown vacuolar structures or corpuscles in the cytoplasm of erythrocytes, HL-60, and TF-1 cell lines. The A. capra morulae were seen in the cytoplasm of both HL-60 and TF-1 in TEM, and their diameter was about 295–518 nm. Both dense-cored (DC) and reticulate cell (RC) form morulae could be seen. This study confirmed the ability of A. capra to infect human erythrocytes, HL-60, and TF-1. This study is of profound significance in further verifying the zoonotic characteristics of the pathogen and for establishing an in vitro cultivation model.

Highlights

The human erythrocytes, HL-60, and TF-1 cells, which had been inoculated for 96 h, The human erythrocytes, HL-60, and TF-1 cells, which had been inoculated for were subjected to Wright–Giemsa staining
After 96 h of inoculation of the human erythrocytes, HL-60, and TF-1 cell smears, After 96 h of inoculation of the human erythrocytes, HL-60, and TF-1 cell smears, brown brown substances were visible on the surfaces of the substantially inoculated human substances were visible on the surfaces of the substantially inoculated human erythrocytes erythrocytes (Figure 3B), indicating that these cells were infected with A. capra
A. capra- of vacuole-like structures were observed in the cytoplasm of HL-60 cells, inoculated HL-60 cells, where the vacuole edges were dark brown in color

Summary

Introduction

Anaplasma capra is one of the species of the Anaplasma genus that are considered significant zoonotic pathogens [1]. As early as 2010, Zhou et al (2010) [2] detected an unknown Anaplasma species in goat blood samples in the Chongqing region of China. In 2015, Li et al [3] detected the above pathogen at the Mudanjiang Central Hospital in Heilongjiang in the blood of patients with a tick bite history. After phylogenetic analysis based on 16S rRNA, gltA, msp, and msp loci, the above species was considered a new species of the Anaplasma genus; it was temporarily named A. capra. Similar to A. phagocytophilum and A. ovis, it could infect humans [4,5]. It is similar to A. ovis, A. centrale, and

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