Exogenous nitric oxide stimulates early egress of Eimeria tenella sporozoites from primary chicken kidney cells in vitro.

Xinlei Yan,Xun Suo,Wenying Han,Xianyong Liu

doi:10.1051/parasite/2021007

Abstract

Egress plays a vital role in the life cycle of apicomplexan parasites including Eimeria tenella, which has been attracting attention from various research groups. Many recent studies have focused on early egress induced by immune molecules to develop a new method of apicomplexan parasite elimination. In this study, we investigated whether nitric oxide (NO), an immune molecule produced by different types of cells in response to cytokine stimulation, could induce early egress of eimerian sporozoites in vitro. Eimeria tenella sporozoites were extracted and cultured in primary chicken kidney cells. The number of sporozoites egressed from infected cells was analyzed by flow cytometry after treatment with NO released by sodium nitroferricyanide (II) dihydrate. The results showed that exogenous NO stimulated the rapid egress of E. tenella sporozoites from primary chicken kidney cells before replication of the parasite. We also found that egress was dependent on intra-parasitic calcium ion (Ca2+) levels and no damage occurred to host cells after egress. The virulence of egressed sporozoites was significantly lower than that of fresh sporozoites. The results of this study contribute to a novel field examining the interactions between apicomplexan parasites and their host cells, as well as that of the clearance of intracellular pathogens by the host immune system.

Highlights

Members of the Apicomplexan phylum are obligate intracellular pathogens and include Toxoplasma gondii, Plasmodium spp., and Cryptosporidium spp., which infect many vertebrate hosts including humans, causing severe disease [9, 25, 33]
We verified whether the concentration of nitric oxide (NO) released from SNP could be kept stable when dissolved in Dulbecco’s modified Eagle medium (DMEM) within 30 min by Griess reaction (Fig. 1A)
We found that exogenous NO stimulated early egress of E. tenella sporozoites from infected Primary chicken kidney cells (PCKs) in a Ca2+-dependent process

Summary

Introduction

Members of the Apicomplexan phylum are obligate intracellular pathogens and include Toxoplasma gondii, Plasmodium spp., and Cryptosporidium spp., which infect many vertebrate hosts including humans, causing severe disease [9, 25, 33]. X. Yan et al.: Parasite 2021, 28, 11 parasites that causes severe negative impacts on the poultry industry worldwide, but little is known about the egress process of this genus [11]. Eimeria spp. can lead to severe intestinal disease in chickens, causing global poultry industry losses of approximately USD 3 billion per year [16, 31]. Our previous study revealed that calcium ions (Ca2+) and microneme 2 protein (EtMic 2) secretion were crucial for the egress of eimerian parasites [35, 36]

Methods

Results

Conclusion