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Abstract：
P21 is a protein secreted by all forms of Trypanosoma cruzi (T. cruzi) with recognized biological activities determined in studies using the recombinant form of the protein. In our recent study, we found that the ablation of P21 gene decreased Y strain axenic epimastigotes multiplication and increased intracellular replication of amastigotes in HeLa cells infected with metacyclic trypomastigotes. In the present study, we investigated the effect of P21 in vitro using C2C12 cell lines infected with tissue culture-derived trypomastigotes (TCT) of wild-type and P21 knockout (TcP21-/-) Y strain, and in vivo using an experimental model of T. cruzi infection in BALB/c mice. Our in-vitro results showed a significant decrease in the host cell invasion rate by TcP21-/- parasites as measured by Giemsa staining and cell count in bright light microscope. Quantitative polymerase chain reaction (qPCR) analysis showed that TcP21-/- parasites multiplied intracellularly to a higher extent than the scrambled parasites at 72h post-infection. In addition, we observed a higher egress of TcP21-/- trypomastigotes from C2C12 cells at 144h and 168h post-infection. Mice infected with Y strain TcP21-/- trypomastigotes displayed higher systemic parasitemia, heart tissue parasite burden, and several histopathological alterations in heart tissues compared to control animals infected with scrambled parasites. Therewith, we propose that P21 is important in the host-pathogen interaction during invasion, cell multiplication, and egress, and may be part of the mechanism that controls parasitism and promotes chronic infection without patent systemic parasitemia.
摘要：
P21是由所有形式的克氏锥虫分泌的蛋白质（T。cruzi）具有公认的生物学活性，在使用重组形式的蛋白质的研究中确定。在我们最近的研究中,我们发现，P21基因的消融降低了Y菌株轴性附生附生体的增殖，并增加了感染了异环色素动物的HeLa细胞的细胞内复制。在本研究中,我们使用野生型和P21敲除（TcP21-/-）Y菌株的组织培养来源的色素动物（TCT）感染的C2C12细胞系研究了P21的体外作用，并在体内使用T.cruzi感染BALB/c小鼠的实验模型。我们的体外结果表明，通过Giemsa染色和明亮的显微镜下的细胞计数，TcP21-/-寄生虫的宿主细胞侵袭率显着降低。定量聚合酶链反应（qPCR）分析显示，感染后72小时，TcP21-/-寄生虫在细胞内的繁殖程度高于杂乱的寄生虫。此外,我们在感染后144h和168h观察到来自C2C12细胞的TcP21-/-色素动物的较高出口。感染Y株TcP21-/-色素动物的小鼠表现出更高的全身性寄生虫血症，心脏组织寄生虫负担，和一些组织病理学改变在心脏组织相比，对照动物感染了混乱的寄生虫。因此，我们认为P21在入侵过程中的宿主-病原体相互作用中很重要，细胞增殖，和出口，并且可能是控制寄生虫和促进慢性感染而没有全身性寄生虫血症的机制的一部分。
