Yongfeng Fu

High prevalence of Entamoeba infections in captive long-tailed macaques in China

Long-tailed macaques (Macaca fascicularis) are bred in China for export and for use in experiments. Entamoeba infections in captive long-tailed macaques were surveyed in one of the biggest colonies located in Guangxi Province, China. One stool sample was obtained from each of the 152 different cages representing >3,000 macaques in the colony. The samples were examined by PCR for five Entamoeba species. The number of detected Entamoeba coli infections comprised 94% of the samples, 93% for Entamoeba chattoni, and 83% for Entamoeba dispar. In contrast, Entamoeba histolytica and Entamoeba nuttalli were not detected. Six isolates of E. dispar were obtained by culture in Tanabe–Chiba medium. Analysis of serine-rich protein genes in these isolates showed two genotypes, one of which is identical to that of the E. dispar SAW760 strain in humans. This suggests transmission of E. dispar between humans and nonhuman primates. These results demonstrate that Entamoeba infections are common, but virulent Entamoeba species are absent in this colony. This work also confirms the need for monitoring with PCR-based identification of Entamoeba species for captive macaques in breeding colonies to ensure animal health and protection of humans from zoonotic hazards.

Prevalence and genetic diversity of Entamoeba species infecting macaques in southwest China

Many colonies of macaques (Macaca fascicularis and Macaca mulatta) are maintained in China, especially in Guangxi and Guizhou. A total of 803 fresh stool samples infected with Entamoeba were obtained from three big colonies of macaques located in southwest China. The samples were examined for the presence of five Entamoeba species using PCR. Entamoeba nuttalli, Entamoeba dispar, Entamoeba coli, and Entamoeba chattoni infections were detected, but Entamoeba histolytica infection was not. This study is the first to report on the prevalence of E. nuttalli in wild macaques from China. Eighteen E. nuttalli isolates and five E. dispar isolates were obtained by culturing the samples in Tanabe–Chiba medium. The serine-rich protein (SRP), ribosomal RNA (rRNA), hexokinase (HXK), glucose-6-phosphate isomerase (GPI), and phosphoglucomutase (PGM) genes of E. nuttalli isolates were compared with other reported isolates. The results showed clear differences among the Chinese E. nuttalli isolates and other isolates based on the SRP gene sequences. However, HXK, GPI, and PGM genes of these strains were similar to those of other isolates. The rRNA genes of E. coli and E. chattoni were also amplified and analyzed from these samples. The results suggested that host species might be a more important factor than geographic location in amebic genetic diversity.

Unique short tandem repeat nucleotide sequences in Entamoeba histolytica isolates from China

A few PCR-based DNA typing methods using repetitive elements contained within both protein-coding genes and noncoding DNAs have been reported for Entamoeba histolytica over the years. The serine-rich E. histolytica protein and tRNA-linked short tandem repeats (STRs) are most commonly used to investigate the relationship between parasite genotype and E. histolytica infection outcome. Many E. histolytica infections in China have been reported; however, little genome information has been provided. In the current paper, five Chinese E. histolytica samples were reported: three amoebic liver abscess cases, one combined case and one asymptomatic case. Our study is the first to report on the DNA typing information of E. histolytica in China. We included two city, one imported, and two country cases. Sequence analysis of serine-rich protein genes confirmed the presence of seven sequence types in five isolates. The STRs amplified from the samples revealed five STR variations in the A-L, four in the N-K2, and R-R loci, three in D-A, STGA-D and S-Q loci. Two country patients were found to have a different outcome of infection with the same genotypes of E. histolytica, whereas in a city case, one E. histolytica strain had led to different outcome of the infection in one patient. Analyses of the results suggest that more genome information of E. histolytica strains from China through accurate methods is needed to interpret how the parasite genome plays a role in determining the outcome of E. histolytica infections.

Generation of a Neutralizing Human Monoclonal Antibody Fab Fragment to Surface Antigen 1 of Toxoplasma gondii Tachyzoites

ABSTRACT A combinatorial immunoglobulin gene library was constructed from lymphocytes in peripheral blood of a patient with toxoplasmosis and screened for production of human monoclonal antibody Fab fragments to recombinant surface antigen 1 (SAG1) of Toxoplasma gondii. Two Fab clones, Tox203 and Tox1403, which consisted of a common heavy chain and different light chains, showed positive staining on the entire surface of tachyzoites in confocal microscopy. Sequence analysis of the heavy-chain gene revealed that the closest germ line V segments were VH3-23. The germ line D segment was D1-7, and the closest germ line J segment was JH4. In the light-chain genes, the closest germ line V segment was Vκ1-17 with the Jκ1 or Jκ4 segments. The dissociation constants of these Fab fragments with recombinant SAG1 were 3.09 × 10−9 M for Tox203 and 2.01 × 10−8 M for Tox1403, indicating that the affinity of Tox203 was 7 times higher than that of Tox1403. Preincubation of T. gondii tachyzoites with Tox203 significantly inhibited their attachment to cultured MDBK cells. Passive immunization of mice with Tox203 also significantly reduced mortality after challenge with T. gondii tachyzoites. This is the first report of bacterial expression of human monoclonal antibody Fab fragments to SAG1 of T. gondii. These results also demonstrate that human Fab fragments to SAG1 might be applicable for immunoprophylaxis of toxoplasmosis.

Evaluation of the C-Terminal Fragment of Entamoeba histolytica Gal/GalNAc Lectin Intermediate Subunit as a Vaccine Candidate against Amebic Liver Abscess.

Background Entamoeba histolytica is an intestinal protozoan parasite that causes amoebiasis, including amebic dysentery and liver abscesses. E. histolytica invades host tissues by adhering onto cells and phagocytosing them depending on the adaptation and expression of pathogenic factors, including Gal/GalNAc lectin. We have previously reported that E. histolytica possesses multiple CXXC sequence motifs, with the intermediate subunit of Gal/GalNAc lectin (i.e., Igl) as a key factor affecting the amoebas pathogenicity. The present work showed the effect of immunization with recombinant Igl on amebic liver abscess formation and the corresponding immunological properties. Methodology/Principal Findings A prokaryotic expression system was used to prepare the full-length Igl and the N-terminal, middle, and C-terminal fragments (C-Igl) of Igl. Vaccine efficacy was assessed by challenging hamsters with an intrahepatic injection of E. histolytica trophozoites. Hamsters intramuscularly immunized with full-length Igl and C-Igl were found to be 92% and 96% immune to liver abscess formation, respectively. Immune-response evaluation revealed that C-Igl can generate significant humoral immune responses, with high levels of antibodies in sera from immunized hamsters inhibiting 80% of trophozoites adherence to mammalian cells and inducing 80% more complement-mediated lysis of trophozoites compared with the control. C-Igl was further assessed for its cellular response by cytokine-gene qPCR analysis. The productions of IL-4 (8.4-fold) and IL-10 (2-fold) in the spleen cells of immunized hamsters were enhanced after in vitro stimulation. IL-4 expression was also supported by increased programmed cell death 1 ligand 1 gene. Conclusions/Significance Immunobiochemical characterization strongly suggests the potential of recombinant Igl, especially the C-terminal fragment, as a vaccine candidate against amoebiasis. Moreover, protection through Th2-cell participation enabled effective humoral immunity against amebic liver abscesses.

Comparison of serine-rich protein genes of Entamoeba histolytica isolates obtained from institutions for the mentally retarded in Kanagawa and Shizuoka Prefectures, Japan

In Japan, amebiasis has been observed in homosexual men, in institutionalized persons, and in overseas travelers. We have previously reported an outbreak of amebiasis that occurred from 1986 to 1994 in institutions for the mentally retarded in Kanagawa and Shizuoka Prefectures in Eastern Japan. Entamoeba histolytica but not Entamoeba dispar was identified in Entamoeba cultures obtained from cyst passers in four institutions located in different municipalities in this region. In the present study, serine-rich protein genes of eight isolates from the four institutions were sequenced, and their polymorphism was analyzed. The results showed that all the sequences from the E. histolytica isolates were identical. This retrospective study led us to conclude that the outbreak of amebiasis in different municipalities was derived from a single source of E. histolytica.

Apoptosis of Acanthamoeba castellanii Trophozoites Induced by Oleic Acid

Acanthamoeba spp. can be parasitic in certain situations and are responsible for serious human infections, including Acanthamoeba keratitis, granulomatous amoebic encephalitis, and cutaneous acanthamoebiasis. We analyzed the fatty acid composition of Acanthamoeba castellanii trophozoites and tested the inhibitory activity of the main fatty acids, oleic acid and arachidonic acid, in vitro. Oleic acid markedly inhibited the growth of A. castellanii, with trophozoite viability of 57.4% at a concentration of 200 μM. Caspase‐3 staining and annexin V assays showed that apoptotic death occurred in A. castellanii trophozoites. Quantitative PCR and dot blot analysis showed increased levels of metacaspase and interleukin‐1β converting enzyme, which is also an indication of apoptosis. In contrast, arachidonic acid showed negligible inhibition of growth of A. castellanii trophozoites. Stimulated expression of Atg3, Atg8 and LC3A/B genes and monodansylcadaverine labeling suggested that oleic acid induces apoptosis by triggering autophagy of trophozoites.

Microfluidic system for high-throughput immunoglobulin-E analysis from clinical serum samples.

Rapid and high-throughput analytical techniques for IgE that requires a small serum amount are very important, especially for pediatric patients. In these patients, blood is collected from veins, which is painful compared to fingertip blood collection. Herein, a novel microfluidic system capable of high-throughput parallel analyses of allergen-specific IgE from small amounts of patient serum was successfully developed. A six-plex immunoassay was constructed within a microfluidic chip, and the entire system was validated using samples from clinical patients. Major antigens from house dust mite (Dermatophagoides farinae and Blomia tropicalis), cat (Felis domesticus), fungus (Cladosporium herbarum), ragweed (Humulus japonicas), and tree pollen (Platanus acerifolia) were used as analysis targets. Sample consumption decreased to <0.05 µL compared with the 480µL serum consumption by fluoroenzyme immunoassay (UniCAP system Pharmacia Diagnostics AB, Uppsala, Sweden), the 50 µL serum consumption by enzyme-linked immune sorbent assay (ELISA), or the 1.5 µL serum consumption by conventional protein chip analysis. Analysis duration, reagent cost, and total cost for each measurement were also considerably decreased. The assay showed good accuracy and sensitivity toward the clinical samples. A significant correlation of allergen-specific IgE levels was found among the microfluidic assay, UniCAP system, and ELISA.

Identification of Human UMP/CMP Kinase 1 as Doxorubicin Binding Target Using Protein Microarray

Doxorubicin (DOX) is a leading anthracycline drug with exceptional efficacy; however, little is known about the molecular mechanisms of its side effects, which include heart muscle damage, noncancerous cell death, and drug resistance. A total of 17,950 human proteins expressed in HEK293 cells were screened and yielded 14 hits. Competitive and binding experiments further verified the binding of DOX to UMP/CMP kinase 1 (CMPK1), and microscale thermophoresis showed that DOX binds to CMPK1 with a Kd of 1216 nM. In addition, we observed that the binding of DOX to CMPK1 activated the phosphorylation of CMP, dCMP, and UMP. A significant activation was observed at the concentration of 30 µM DOX and reached plateau at the concentration of DOX 30 µM, 150 µM, and 100 µM, respectively. DOX would add up stimulation of CMPK1 by DTT and overcome inhibition of CMPK1 by NaF, EDTA. In summary, we showed that DOX might bind to the nonactive site of CMPK1 and regulate its activity with magnesium.

Rapid microfluidic immunoassay for surveillance and diagnosis of Cryptosporidium infection in human immunodeficiency virus-infected patients

Cryptosporidiosis has been reported to be associated with HIV/acquired immune deficiency syndrome, which greatly reduces the quality of life and shortens the life expectancy of HIV-infected patients. In order to properly treat the infected patients, accurate and automatic diagnostic tools need to be developed. In this study, a novel microfluidic immunochip system was presented for the surveillance and the rapid detection of Cryptosporidium infection in 190 HIV-infected patients from Guangxi, China, using the P23 antigen of Cryptosporidium. The procedure of detection can be completed within 10 min with 2 μl sample consumption. The system also was evaluated using the standard ELISA method. Among 190 HIV-infected individuals, the rate of P23 positivity was 13.7%. Seropositivity in HIV-infected individuals was higher in female patients. The seropositivity to P23 was higher in HIV-infected individuals with high viral load, although the difference was statistically insignificant. Significantly higher Cryptosporidium seropositivity was observed in HIV-infected individuals with a CD4(+) T-cell count of <200 cells/μl than in those with ≥200 cells/μl. Our results also demonstrate that a lower CD4(+) T-cell count may reflect an increased accumulated risk for cryptosporidiosis. The detection system was further validated using the standard ELISA method and good correlation between the two methods was found (r = 0.80). Under the same sensitivity, this new microfluidic chip device had a specificity of 98.2%. This developed system may provide a powerful platform for the fast screening of Cryptospordium infection in HIV-infected patients.