Min-Jun Xu

Comparative analyses of the complete mitochondrial genomes of Ascaris lumbricoides and Ascaris suum from humans and pigs.

Ascaris lumbricoides and Ascaris suum are parasitic nematodes living in the small intestine of humans and pigs, and can cause the disease ascariasis. For long, there has been controversy as to whether the two ascaridoid taxa represent the same species due to their significant resemblances in morphology. However, the complete mitochondrial (mt) genome data have been lacking for A. lumbricoides in spite of human and animal health significance and socio-economic impact globally of these parasites. In the present study, we sequenced the complete mt genomes of A. lumbricoides and A. suum (China isolate), which was 14,303 bp and 14,311 bp in size, respectively. The identity of the mt genomes was 98.1% between A. lumbricoides and A. suum (China isolate), and 98.5% between A. suum (China isolate) and A. suum (USA isolate). Both genomes are circular, and consist of 36 genes, including 12 genes for proteins, 2 genes for rRNA and 22 genes for tRNA, which are consistent with that of all other species of ascaridoid studied to date. All genes are transcribed in the same direction and have a nucleotide composition high in A and T (71.7% for A. lumbricoides and 71.8% for A. suum). The AT bias had a significant effect on both the codon usage pattern and amino acid composition of proteins. Phylogenetic analyses of A. lumbricoides and A. suum using concatenated amino acid sequences of 12 protein-coding genes, with three different computational algorithms (Bayesian analysis, maximum likelihood and maximum parsimony) all clustered in a clade with high statistical support, indicating that A. lumbricoides and A. suum was very closely related. These mt genome data and the results provide some additional genetic evidence that A. lumbricoides and A. suum may represent the same species. The mt genome data presented in this study are also useful novel markers for studying the molecular epidemiology and population genetics of Ascaris.

Canine and feline parasitic zoonoses in China

Canine and feline parasitic zoonoses have not been given high priority in China, although the role of companion animals as reservoirs for zoonotic parasitic diseases has been recognized worldwide. With an increasing number of dogs and cats under unregulated conditions in China, the canine and feline parasitic zoonoses are showing a trend towards being gradually uncontrolled. Currently, canine and feline parasitic zoonoses threaten human health, and cause death and serious diseases in China. This article comprehensively reviews the current status of major canine and feline parasitic zoonoses in mainland China, discusses the risks dogs and cats pose with regard to zoonotic transmission of canine and feline parasites, and proposes control strategies and measures.

First Report of Genotyping of Toxoplasma gondii Isolates From Wild Birds in China

Abstract: Toxoplasma gondii is an important cosmopolitan opportunistic protozoan parasite, which threatens the health of human beings and animals. Genetic characterization of isolates from South America has revealed high genetic diversity. In contrast, isolates from North America and Europe were highly clonal, with 3 major lineages known as the Types I, II, and III. However, limited information on T. gondii genotypes has been reported in The Peoples Republic of China. Here we conducted a survey to determine genetic diversity of this parasite in wild birds of China. In total, tissues from breast muscle of 178 wild birds, including 98 common pheasants (Phasianus colchicus), 35 tree sparrows (Passer montanus), 22 house sparrows (Passer domesticus), 20 saxaul sparrows (Passer ammodendri), and 1 cinnamon sparrow (Passer rutilans), were tested for T. gondii infection, 4 of which were found to be positive for the T. gondii B1 gene by PCR amplification. These positive DNA samples were typed at 10 genetic markers, including 9 nuclear loci, i.e., SAG1, 5′- and 3′-SAG2, alternative SAG2, SAG3, GRA6, L358, PK1, c22-8, c29-2, and an apicoplast locus Apico. Of these, 3 isolates were genotyped with complete data for all loci, and 2 genotypes (Type I and Type II variant) were identified. This is the first report of genetic typing of T. gondii isolates from wild birds from different regions in China. The results suggest that the Type I and II variant strains are circulating in wild birds in China, and these birds are potential reservoirs for T. gondii transmission.

Characterization of microRNAs in Taenia saginata of zoonotic significance by Solexa deep sequencing and bioinformatics analysis

The beef tapeworm Taenia saginata infects human beings with symptoms ranging from nausea, abdominal discomfort to digestive disturbances and intestinal blockage. In the present study, microRNA (miRNA) expressing profile in adult T. saginata was analyzed using Solexa deep sequencing and bioinformatics analysis. A total of 15.8 million reads was obtained by Solexa sequencing, and 13.3 million clean reads (1.73 million unique sequences) was obtained after removing reads smaller than 18 nt. Ten conserved miRNAs corresponding to 607,382 reads were found when matching the reads against known miRNAs of Schistosoma japonicum in miRBase database. The miR-71 had the most abundant expression in T. saginata, followed by miR-219-5p, but some other common miRNAs such as let-7, miR-40, and miR-103 were not identified in T. saginata. Nucleotide bias analysis found that the known miRNAs showed high bias and the uracil was the dominant nucleotide, particularly at the first and 11th positions which were almost at the beginning and middle of conserved miRNAs. One novel miRNA (Tsa-miR-001) corresponding to ten precursors was identified and confirmed by stem-loop RT-PCR. To our knowledge, this is the first report of miRNA profiles in T. saginata, which will contribute to better understanding of the complex biology of this zoonotic trematode. The reported data of T. saginata miRNAs should provide valuable references for miRNA studies of closed related zoonotic Taenia cestodes such as Taenia solium and Taenia asiatica.

Genomics and molecular genetics of Clonorchis sinensis: Current status and perspectives

Clonorchiasis caused by Clonorchis sinensis is an important foodborne parasitosis of humans and animals, and is predominantly a hepatobiliary disease. Globally, nearly 35 million people were infected with C. sinensis, with approximately 15 million being in China. Patients would chronically present fatigue, jaundice, abdominal discomfort, along with the increased risk of developing into a form of cholangiocarcinoma that is fatal to humans. Treatment of clonorchiasis by praziquantel has been very successful, but this is dependent on early accurate diagnosis and correct species identification. The present article reviews the current status of knowledge in genomics and functional genomics of C. sinensis, and summarizes the main DNA-based techniques for the specific diagnosis of C. sinensis infection and studies of genetic variation in C. sinensis, and provides perspectives for future studies. The advances in genomics and molecular genetics of C. sinensis shed new sight on our understanding of population structure of C. sinensis as well as the prevention and control of clonorchiasis.

Toxoplasma gondii: protective immunity against experimental toxoplasmosis induced by a DNA vaccine encoding the perforin-like protein 1.

Toxoplasma gondii is an important zoonotic parasite infecting about one third of the world population, causing congenital infections and eye disease. T. gondii perforin-like protein 1 (TgPLP1) is believed to be involved in the acute virulence of T. gondii in mice, and is therefore of interest as a vaccine candidate. In this study, we constructed a DNA vaccine expressing TgPLP1, and evaluated the immune response in Kunming mice. The gene sequence encoding TgPLP1 was inserted into the eukaryotic expression vector pVAX I, and Kunming mice were immunized intramuscularly with the plasmid. After immunization, we evaluated the immune response using lymphoproliferative assay, cytokine and antibody measurements, and the survival times of mice challenged lethally with 1×10(3) tachyzoites of the virulent T. gondii RH strain. The results showed that pVAX/TgPLP1 alone or with pVAX/IL-18 developed specific anti-TLA (T. gondii lysate antigen) antibodies and specific lymphocyte proliferative responses. Co-injection of pVAX/IL-18 significantly increased the production of IFN-γ and IL-2. Further, challenge experiments showed that co-immunization of pVAX/TgPLP1 with pVAX/IL-18 significantly (P<0.05) increased survival time (12.7±1.2days) of immunized mice, compared with pVAX/TgPLP1 alone (11.3±0.9days). These results demonstrate that TgPLP1 is a potential vaccine candidate against toxoplasmosis, worth further evaluation in other animal hosts. IL-18 could enhance the immune effect of TgPLP1, prolonging the survival time of immunized mice.

First report of Toxoplasma gondii infection in market-sold adult chickens, ducks and pigeons in northwest China

BackgroundToxoplasma gondii infection is a global concern, affecting a wide range of warm-blooded animals and humans worldwide, including poultry. Domestic and companion birds are considered to play an important role in the transmission of T. gondii to humans and other animals. However, little information on T. gondii infection in domestic birds in Lanzhou, northwest China was available. Therefore, this study was performed to determine the seroprevalence of T. gondii infection in domestic birds in Lanzhou, northwest China.MethodsIn the present study, the seroprevalence of T. gondii antibodies in 413 (305 caged and 108 free-range) adult chickens, 334 (111 caged and 223 free-range) adult ducks and 312 adult pigeons in Lanzhou, northwest China, were examined using the modified agglutination test (MAT).Results30 (7.26%) chickens, 38 (11.38%) ducks and 37 (11.86%) pigeons were found to be positive for T. gondii antibodies at the cut-off of 1:5. The prevalences in caged and free-range chickens were 6.23% and 10.19% respectively, however, statistical analysis showed that the difference was not significant (P > 0.05). The seroprevalences in caged and free-range ducks were 6.31% and 13.90% respectively, but the difference was not statistically significant (P > 0.05).ConclusionsThe results of the present survey indicated the presence of T. gondii infection in adult chickens, ducks and pigeons sold for meat in poultry markets in Lanzhou, northwest China, which poses a potential risk for T. gondii infection in humans and other animals in this region. This is the first seroprevalence study of T. gondii infection in domestic birds in this region.

Identification and characterization of microRNAs in Trichinella spiralis by comparison with Brugia malayi and Caenorhabditis elegans.

Trichinella spiralis is an important zoonotic nematode causing trichinellosis which is associated with human diseases such as malaise, anorexia, nausea, vomiting, abdominal pain, fever, diarrhea, and constipation. microRNAs (miRNAs) are endogenous small non-coding RNAs that play important roles in the regulation of gene expression. The objective of the present study was to examine the miRNA expression profile of the larvae of T. spiralis by Solexa deep sequencing combined with stem-loop real-time polymerase chain reaction (PCR) analysis. T. spiralis larvae were collected from the skeletal muscle of naturally infected pigs in Henan province, China, by artificial digestion using pepsin. The specific identity of the T. spiralis larvae was confirmed by PCR amplification and subsequent sequence analysis of the internal transcribed spacer of ribosomal DNA. A total of 17,851,693 reads with 2,773,254 unique reads were obtained. Eleven conserved miRNAs from 115 unique xsmall RNAs (sRNAs) and 12 conserved miRNAs from 130 unique sRNAs were found by BLAST analysis against the known miRNAs of Caenorhabditis elegans (ftp://ftp.ncbi.nih.gov/genomes/Caenorhabditis_elegans) and Brugia malayi dataset (http://www.ncbi.nlm.nih.gov/genomeprj?Db=genomeprj&cmd=ShowDetailView&TermToSearch=9549) in miRBase, respectively. One novel miRNA with 12 precursors were identified and certified using the reference genome of B. malayi, while no novel miRNA was found when using the reference genome of C. elegans. Nucleotide bias analysis showed that the uracil was the prominent nucleotide, particularly at the 1st, 6th, 18th, and 23th positions, which were almost at the beginning, middle, and the end of the conserved miRNAs. The identification and characterization of T. spiralis miRNAs provides a new resource to study regulation of genes and their networks in T. spiralis.

Angiostrongylus cantonensis: identification and characterization of microRNAs in male and female adults.

Angiostrongylus cantonensis causes eosinophilic meningitis and eosinophilic pleocytosis in humans and is of significant socio-economic importance globally. microRNAs (miRNAs) are endogenous small non-coding RNAs that play crucial roles in gene expression regulation, cellular function and defense, homeostasis and pathogenesis. They have been identified in a diverse range of organisms. The objective of this study was to determine and characterize miRNAs of female and male adults of A. cantonensis by Solexa deep sequencing. A total of 8,861,260 and 10,957,957 high quality reads with 20 and 23 conserved miRNAs were obtained in females and males, respectively. No new miRNA sequence was found. Nucleotide bias analysis showed that uracil was the prominent nucleotide, particularly at positions of 1, 10, 14, 17 and 22, approximately at the beginning, middle and the end of the conserved miRNAs. To our knowledge, this is the first report of miRNA profiles in A. cantonensis, which may represent a new platform for studying regulation of genes and their networks in A. cantonensis.

Changes in the proteomic profiles of mouse brain after infection with cyst-forming Toxoplasma gondii

BackgroundToxoplasma gondii is an opportunistic pathogenic protozoan parasite, which infects approximately one third of the human population worldwide, causing opportunistic zoonotic toxoplasmosis. The predilection of T. gondii for the central nervous system (CNS) causes behavioral disorders and fatal necrotizing encephalitis and thus constitutes a major threat especially to AIDS patients.MethodsIn the present study, we explored the proteomic profiles of brain tissues of the specific pathogen-free (SPF) Kunming mice at 7 d, 14 d and 21 d after infection with cysts of the Toxoplasma gondii Prugniaud (PRU) strain (Genotype II), by two-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF tandem mass spectrometry (MS/MS).ResultsA total of 60 differentially expressed protein spots were selected. Fifty-six spots were successfully identified, which corresponded to 45 proteins of the mouse. Functional analysis using a Gene Ontology database showed that these proteins were mainly involved in metabolism, cell structure, signal transduction and immune responses, and will be beneficial for the understanding of molecular mechanisms of T. gondii pathogenesis.ConclusionsThis study identified some mouse brain proteins involved in the response with cyst-forming T. gondii PRU strain. These results provided an insight into the responsive relationship between T. gondii and the host brain tissues, which will shed light on our understanding of the mechanisms of pathogenesis in toxoplasmic encephalitis, and facilitate the discovery of new methods of diagnosis, prevention, control and treatment of toxoplasmic encephalopathy.