Background: Colon cancer is a common gastrointestinal tumor with a poor prognosis, and thus new therapeutic strategies are urgently needed. The antitumor effect ofPlasmodiuminfection has been reported in some murine models, but it is not clear whether it has an anti-colon cancer effect. In this study, we investigated the anti-colon cancer effect ofPlasmodiuminfection and its related mechanisms using a mouse model of colon cancer.Methods: An experimental model was established by intraperitoneal injection ofPlasmodium yoelii17XNL-infected erythrocytes into mice with colon cancer. The size of tumors was observed dynamically in mice, and the expression of Ki67 detected by immunohistochemistry was used to analyze tumor cell proliferation. Apoptosis was assessed by terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining, and the expression of apoptosis-related proteins including Bax, Bcl-2, caspase-9, and cleaved caspase-3 was detected by western blot and immunohistochemistry, respectively. Transmission electron microscopy (TEM) was used to observe the ultrastructural change in colon cancer cells, and the expression of mitochondrial biogenesis correlative central protein, PGC-1α, and mitophagy relevant crucial proteins, PINK1/Parkin, were detected by western blot.Results: We found thatPlasmodiuminfection reduced the weight and size of tumors and decreased the expression of Ki67 in colon cancer-bearing mice. Furthermore,Plasmodiuminfection promoted mitochondria-mediated apoptosis in colon cancer cells, as evidenced by the increased proportion of TUNEL-positive cells, the upregulated expression of Bax, caspase-9, and cleaved caspase-3 proteins, and the downregulated expression of Bcl-2 protein. In colon cancer cells, we found destroyed cell nuclei, swollen mitochondria, missing cristae, and a decreased number of autolysosomes. In addition,Plasmodiuminfection disturbed mitochondrial biogenesis and mitophagy through the reduced expression of PGC-1α, PINK1, and Parkin proteins in colon cancer cells.Conclusions: Plasmodiuminfection can play an anti-colon cancer role in mice by inhibiting proliferation and promoting mitochondria-mediated apoptosis in colon cancer cells, which may relate to mitochondrial biogenesis and mitophagy.Graphical

Antibiotic resistance screening is crucial in the construction of recombinant plasmids. The dfrB10 gene, a short-size trimethoprim (TMP)-resistance type B dihydrofolate reductase gene, is a promising antibiotic drug screening marker for plasmid construction in molecular genetic research. Currently, available plasmid backbones (without the resistance gene) were amplified using PCR, and then we ligated these products with dfrB10 gene fragments via homologous recombination to construct new plasmid vectors with TMP resistance. The cloning, expression, and gene editing functions of the new plasmids based on their different purposes were verified. By successfully replacing the original resistance genes of pUC19, pET28a, pcDNA3.1, and pX330 plasmids with dfrB10 , we constructed a series of plasmids with TMP resistance. The change of the resistance selection marker to TMP did not affect the function of the plasmids compared to the original ones. Furthermore, a short (988 bp) TMP-resistant miniature tool plasmid, pTMi, was constructed based on the pUC19 plasmid. With the use of the dfrB10 gene as a resistance marker under TMP drug screening, various size-reduced tool plasmids can be routinely constructed. These plasmids have similar functions to the original ones and can be used for research applications in molecular genetics. IMPORTANCE: Plasmid size is one of the factors affecting transfection efficacy in most of the molecular genetic research studies. One effective approach for reducing plasmid size is to replace relatively large, conventional antibiotic resistance genes with the short-size dfrB10 gene. The successful construct of a series of dfrB10- based tool plasmids and their functional validation, via comparison with original plasmids, suggest that dfrB10 is a potent drug resistance selection marker. The antibiotic trimethoprim offers convenient usage comparable to that of ampicillin or kanamycin. Additionally, fluorescence analysis has demonstrated the compatibility of TMP with protein expression in various host cells. Based on these findings, TMP- dfrB10 could be an alternative choice for future use in molecular genetic research studies that require miniature plasmids to achieve optimal results.

The mechanisms of cellular and humoral immune responses against P. vivax parasite remain poorly understood. Several malaria immunological studies have been conducted in endemic regions where both P. falciparum and P. vivax parasites co-exist. In this study, a comparative analysis of immunity to Plasmodium vivax antigens in different geography and incidence of Plasmodium spp. infection was performed. We characterised antibodies against two P. vivax antigens, PvMSP-1 and PvAMA-1, and the cross-reactivity between these antigens using plasma from acute malaria infected patients living in the central region of China and in the western border of Thailand. P. vivax endemicity is found in central China whereas both P. vivax and P. falciparum are endemic in Thailand. There was an increased level of anti-PvMSP-1/anti-PvAMA-1 in both populations. An elevated level of antibodies to total P. vivax proteins and low level of antibodies to total P. falciparum proteins was found in acute P. vivax infected Chinese, suggesting antibody cross-reactivity between the two species. P. vivax infected Thai patients had both anti-P. vivax and anti-P. falciparum antibodies as expected since both species are present in Thailand. More information on humoral and cell mediated immunity during acute P. vivax-infection in the area where only single P. vivax species existed is of great interest in the relation of building up anti-disease severity caused by P. falciparum. This knowledge will support vaccine development in the future.