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Biomedical subjects

L Xiao

Publications and source records attributed to L Xiao.

At least 109 records · Page 6Linked to original sources
PubMed1999

Effect of immune activation induced by Cryptosporidium parvum whole antigen on in vitro human immunodeficiency virus type 1 infection.

Previous epidemiologic investigations have suggested that persons with AIDS who are infected with Cryptosporidium parvum have a shorter survival time than those with other opportunistic infections. In this study, the effect of immune activation by a crude Cryptosporidium whole antigen on human immunodeficiency virus type 1 (HIV-1) infection was evaluated. Peripheral blood mononuclear cells from healthy persons without HIV-1 infection had increased proliferative and cytokine (interleukin-4, interferon-gamma, and tumor necrosis factor [TNF]-alpha) responses to stimulation with the crude Cryptosporidium whole antigen. This stimulation increased HIV-1 p24 antigen production in in vitro infection by>30-fold. A similar increase in p24 production was also seen when stimulation was done after cells were infected with HIV-1. Neutralization of TNF-alpha reduced Cryptosporidium antigen-induced p24 production by >50%. Results of this study suggest that Cryptosporidium-induced immune activation may be a cofactor in regulating HIV-1 production.

Animals↗
PubMed1999

Evaluation of Cryptosporidium parvum genotyping techniques.

We evaluated the specificity and sensitivity of 11 previously described species differentiation and genotyping PCR protocols for detection of Cryptosporidium parasites. Genomic DNA from three species of Cryptosporidium parasites (genotype 1 and genotype 2 of C. parvum, C. muris, and C. serpentis), two Eimeria species (E. neischulzi and E. papillata), and Giardia duodenalis were used to evaluate the specificity of primers. Furthermore, the sensitivity of the genotyping primers was tested by using genomic DNA isolated from known numbers of oocysts obtained from a genotype 2 C. parvum isolate. PCR amplification was repeated at least three times with all of the primer pairs. Of the 11 protocols studied, 10 amplified C. parvum genotypes 1 and 2, and the expected fragment sizes were obtained. Our results indicate that two species-differentiating protocols are not Cryptosporidium specific, as the primers used in these protocols also amplified the DNA of Eimeria species. The sensitivity studies revealed that two nested PCR-restriction fragment length polymorphism (RFLP) protocols based on the small-subunit rRNA and dihydrofolate reductase genes are more sensitive than single-round PCR or PCR-RFLP protocols.

Animals↗
PubMed1999

Phylogenetic analysis of Cryptosporidium parasites based on the small-subunit rRNA gene locus.

Biological data support the hypothesis that there are multiple species in the genus Cryptosporidium, but a recent analysis of the available genetic data suggested that there is insufficient evidence for species differentiation. In order to resolve the controversy in the taxonomy of this parasite genus, we characterized the small-subunit rRNA genes of Cryptosporidium parvum, Cryptosporidium baileyi, Cryptosporidium muris, and Cryptosporidium serpentis and performed a phylogenetic analysis of the genus Cryptosporidium. Our study revealed that the genus Cryptosporidium contains the phylogenetically distinct species C. parvum, C. muris, C. baileyi, and C. serpentis, which is consistent with the biological characteristics and host specificity data. The Cryptosporidium species formed two clades, with C. parvum and C. baileyi belonging to one clade and C. muris and C. serpentis belonging to the other clade. Within C. parvum, human genotype isolates and guinea pig isolates (known as Cryptosporidium wrairi) each differed from bovine genotype isolates by the nucleotide sequence in four regions. A C. muris isolate from cattle was also different from parasites isolated from a rock hyrax and a Bactrian camel. Minor differences were also detected between C. serpentis isolates from snakes and lizards. Based on the genetic information, a species- and strain-specific PCR-restriction fragment length polymorphism diagnostic tool was developed.

Animals↗
PubMed1999

Genetic diversity within Cryptosporidium parvum and related Cryptosporidium species.

To assess the genetic diversity in Cryptosporidium parvum, we have sequenced the small subunit (SSU) rRNA gene of seven Cryptosporidium spp., various isolates of C. parvum from eight hosts, and a Cryptosporidium isolate from a desert monitor. Phylogenetic analysis of the SSU rRNA sequences confirmed the multispecies nature of the genus Cryptosporidium, with at least four distinct species (C. parvum, C. baileyi, C. muris, and C. serpentis). Other species previously defined by biologic characteristics, including C. wrairi, C. meleagridis, and C. felis, and the desert monitor isolate, clustered together or within C. parvum. Extensive genetic diversities were present among C. parvum isolates from humans, calves, pigs, dogs, mice, ferrets, marsupials, and a monkey. In general, specific genotypes were associated with specific host species. A PCR-restriction fragment length polymorphism technique previously developed by us could differentiate most Cryptosporidium spp. and C. parvum genotypes, but sequence analysis of the PCR product was needed to differentiate C. wrairi and C. meleagridis from some of the C. parvum genotypes. These results indicate a need for revision in the taxonomy and assessment of the zoonotic potential of some animal C. parvum isolates.

Animals↗
PubMed1999

Partial protection against Plasmodium vivax blood-stage infection in Saimiri monkeys by immunization with a recombinant C-terminal fragment of merozoite surface protein 1 in block copolymer adjuvant.

Merozoite surface protein 1 is a candidate for blood-stage vaccines against malaria parasites. We report here an immunization study of Saimiri monkeys with a yeast-expressed recombinant protein containing the C terminus of Plasmodium vivax merozoite surface protein 1 and two T-helper epitopes of tetanus toxin (yP2P30Pv20019), formulated in aluminum hydroxide (alum) and block copolymer P1005. Monkeys immunized three times with yP2P30Pv20019 in block copolymer P1005 had significantly higher prechallenge titers of immunoglobulin G (IgG) antibodies against the immunogen and asexual blood-stage parasites than those immunized with yP2P30Pv20019 in alum, antigen alone, or phosphate-buffered saline (PBS) (P < 0.05). Their peripheral blood mononuclear cell proliferative responses to immunogen stimulation 4 weeks after the second immunization were also significantly higher than those from the PBS control group (P < 0.05). Upon challenge with 100,000 asexual blood-stage parasites 5 weeks after the last immunization, monkeys immunized with yP2P30Pv20019 in block copolymer P1005 had prepatent periods longer than those for the control alone group (P > 0.05). Three of the five animals in this group also had low parasitemia (peak parasitemia, </=20 parasites/microliter of blood). Partially protected monkeys had significantly higher levels of prechallenge antibodies against the immunogen than those unprotected (P < 0.05). There was also a positive correlation between the prepatent period and titers of IgG antibodies against the immunogen and asexual blood-stage parasites and a negative correlation between accumulated parasitemia and titers of IgG antibodies against the immunogen (P < 0.05). These results indicate that when combined with block copolymer and potent T-helper epitopes, the yeast-expressed P2P30Pv20019 recombinant protein may offer some protection against malaria.

Adjuvants, Immunologic↗
PubMed1999

Testing the efficacy of a recombinant merozoite surface protein (MSP-1(19) of Plasmodium vivax in Saimiri boliviensis monkeys.

Saimiri boliviensis monkeys were immunized with the yeast-expressed recombinant protein yP2P30Pv200(19). The antigen consisted of the C-terminus (amino acid Asn1622-Ser1729) of the merozoite surface protein 1 of the Plasmodium vivax Salvador I strain. Two universal T helper cell epitopes (P2 and P30) of tetanus toxin and six histidine residues for purification purposes were attached to the N- and C-termini, respectively. Four groups of five monkeys were given three immunizations at four-week intervals with either 250 microg of yP2P30Pv200(19) formulated with nonionic block copolymer P1005, 250 microg of antigen adsorbed to alum, 250 microg of antigen in phosphate-buffered saline (PBS), or PBS alone. Five weeks after the last immunization, each animal was inoculated with 100,000 parasitized erythrocytes of the Salvador I strain of P. vivax. Animals were splenectomized one week after challenge to increase parasite densities; after seven weeks of infection, animals were treated. Eighteen weeks later, the animals were rechallenged with the homologous parasite. Following the first challenge, three monkeys immunized with the antigen with P1005 were protected; no animals were protected from rechallenge. One monkey immunized with yP2P30Pv200(19) with alum was protected; no protection was seen after rechallenge. Two monkeys immunized with antigen alone were protected; none were protected from rechallenge. One control animal had a low parasite count following primary infection; none were protected against rechallenge. Adverse reactions were only observed with animals receiving P1005. It is proposed that splenectomy of the monkeys prevented adequate assessment of the efficacy of this antigen. Identification of a monkey host that supports high density parasitemia without splenectomy appears needed before further testing of blood-stage vaccines against P. vivax.

Adjuvants, Immunologic↗
PubMed1999

Role of eicosanoids in the pathogenesis of murine cerebral malaria.

Because microvascular damage is a common feature of cerebral malaria, we have examined the role eicosanoid metabolites (prostaglandins and leukotrienes) in experimental cerebral malaria. Eighty ICR mice were infected with Plasmodium berghei ANKA, with 40 uninfected mice as controls. Half of the infected mice were treated on days 4 and 5 with aspirin, a prostaglandin synthesis inhibitor. Infected mice started to die of cerebral malaria on day 6, and by day 17, all infected mice died. In contrast, all infected mice treated with aspirin died by day 12. Infected mice had increased phospholipase A2 mRNA expression in the spleen and cyclooxygenase 1 (COX1) and COX2 expression in the brain. At the peak of cerebral malaria, infected mice had higher serum leukotriene B4 levels than control mice, and aspirin-treated infected mice had higher serum leukotriene B4 levels than untreated infected mice. These results suggest that prostaglandins are protective whereas leukotrienes are detrimental in cerebral malaria.

Animals↗
PubMed1999

Cytokine production in rhesus monkeys infected with Plasmodium coatneyi.

Plasmodium coatneyi infection in rhesus monkeys has been used as a model for studying human malaria. Cytokine production in this model, however, has so far not been examined. In this study, four rhesus monkeys were infected with P. coatneyi, with another four animals serving as uninfected controls. Blood samples were taken for the determination of daily parasitemia, and cytokine and prostaglandin E2 (PGE2) levels at days 0, 3, 5, 7, and 10. All inoculated animals became infected, with synchronized appearance of ring-stage parasites. Infected monkeys had increased plasma levels of proinflammatory cytokines (interleukin-1beta, interferon-gamma, and tumor necrosis factor-alpha) during the late stage of the infection. They also had increased production of ciliary neurotrophic factor. In conjunction with the production of proinflammatory cytokines, infected monkeys also had gradual increases in the production of PGE2. A continued definition of the P. coatneyi/rhesus monkey animal model should be useful for the elucidation of the immunopathogenesis of human malaria.

Animals↗
PubMed1999

Molecular epidemiology of cryptosporidiosis outbreaks and transmission in British Columbia, Canada.

Isolates from 25 (13 sporadic and 12 outbreak) cryptosporidiosis cases, 24 of which were from British Columbia, Canada, were characterized using nested polymerase chain reaction amplification of the polymorphic internal transcribed spacer 1 locus. Two predominant Cryptosporidium parvum genotypes were found. Twelve (8 sporadic and 4 outbreak) isolates amplified with the cry7/cry21 primer pair and 12 (5 sporadic and 7 outbreak) isolates amplified with the cry7/cryITS1 primer pair. Multi-locus gene analysis using sequence polymorphisms on 3 other loci, i.e., the thrombospondin-related adhesion protein gene, the dihydrofolate reductase gene, and the 18S rRNA gene on 8 (4 outbreak and 4 sporadic) isolates showed non-random association among the human and animal alleles of the 4 different C. parvum gene loci. Associations between these 2 parasite genotypes and different routes of cryptosporidiosis transmission such as zoonotic, anthroponotic, and waterborne transmission were studied using municipal population and agricultural information, as well as detection of C. parvum oocysts in municipal drinking water specimens of the residential communities of sporadic and outbreak cases.

Animals↗
PubMed1999

Biallelic polymorphism in the intron region of beta-tubulin gene of Cryptosporidium parasites.

Nucleotide sequencing of polymerase chain reaction amplified intron region of the Cryptosporidium parvum beta-tubulin gene in 26 human and 15 animal isolates revealed distinct genetic polymorphism between the human and bovine genotypes. The separation of 2 genotypes of C. parvum is in agreement with our previous genotyping data based on the thrombospondin-related adhesion protein (TRAP-C2) gene, indicating these genotype characteristics are linked at 2 genetic loci. Characterization of Cryptosporidium muris and Cryptosporidium serpentis has further shown that non-parvum Cryptosporidium parasites have beta-tubulin intron sequences identical to bovine genotype of C. parvum. Thus, results of this study confirm the lineage of 2 genotypes of C. parvum at 2 genetic loci and suggest a need for extensive characterization of various Cryptosporidium spp.

Alleles↗
PubMed1999

Phylogenetic analysis of Cryptosporidium isolates from captive reptiles using 18S rDNA sequence data and random amplified polymorphic DNA analysis.

Sequence alignment of a polymerase chain reaction-amplified 713-base pair region of the Cryptosporidium 18S rDNA gene was carried out on 15 captive reptile isolates from different geographic locations and compared to both Cryptosporidium parvum and Cryptosporidium muris isolates. Random amplified polymorphic DNA (RAPD) analysis was also performed on a smaller number of these samples. The data generated by both techniques were significantly correlated (P < 0.002), providing additional evidence to support the clonal population structure hypothesis for Cryptosporidium. Phylogenetic analysis of both 18S sequence information and RAPD analysis grouped the majority of reptile isolates together into 1 main group attributed to Cryptosporidium serpentis, which was genetically distinct but closely related to C. muris. A second genotype exhibited by 1 reptile isolate (S6) appeared to be intermediate between C. serpentis and C. muris but grouped most closely with C. muris, as it exhibited 99.15% similarity with C. muris and only 97.13% similarity with C. serpentis. The third genotype identified in 2 reptile isolates was a previously characterized 'mouse' genotype that grouped closely with bovine and human C. parvum isolates.

Animals↗
PubMed1999

Induction of islet transplantation tolerance with anti-CD4, anti-CD8 immunotoxins and donor soluble antigen.

OBJECTIVE: To induce islet grafting tolerance by intravenous injection of anti-CD4, anti-CD8 immunotoxins and donor soluble antigen. METHODS: Fourteen days or 7 days prior to transplantation, the immunotoxin of anti-CD4, anti-CD8 200 micrograms respectively, and donor soluble antigen 500 micrograms were intravenously injected and then 500 donor islets were transplanted under the left renal subcapsular space of diabetes recipients (Sprague-Dawley rats). RESULTS: The islet grafting survival time for those recipients pretreated with immunotoxin and donor soluble antigen was > 60 days (P < 0.01). The immunotoxins, donor soluble antigen treatment alone might only slightly prolong the grafting survival time. CONCLUSION: The anti-CD4, anti-CD8 immunotoxins jointly used with donor soluble antigen can induce donor specific immunotolerance.

Animals↗
PubMed1999

[Clinical study of fibrinolysis indicators in patients with chronic pulmonary heart disease].

OBJECTIVE: To investigate the change of D-dimer and other fibrinolysis indicators in patients with chronic pulmonary heart disease. METHODS: The fibrinolytic activity of plasma was measured in 42 patients with chronic pulmonary heart disease and in 20 controls (matched with sex and age). RESULTS: The D-dimer level was significantly higher in exacerbated patients than in controls (P < 0.001). The fibrinolytic activity in patients was lower than in controls. The plasma fibrinolytic activity was positively correlated with PaO2 and negativly correlated with PaCO2. CONCLUSIONS: The depressed fibrinolysis may be associated with hypercoagulability state of chronic pulmonary heart disease and contributes to thrombi in small pulmonary arteries and arterioles. D-dimer can be used in diagnosis of thrombi formation in small pulmonary arteries and arterioles. Patients with chronic pulmonary heart disease can be treated with fibrinolysis drugs.

Aged↗
PubMed1999

[Co-transplantation of islet and allogeneic testicular cell induced immune privilege].

OBJECTIVE: To induce islet allograft long-term survival through co-transplantation islet with sertoli cell. METHODS: Testicular sertoli cell was prepared by digestion of collagenase, trypsin and Dnase, and cultured for 48 hours. Purified donor (Wistar rat) islet was co-transplanted with allergic sertoli cell, in the absence of systemic immunosuppression. TUNEL (terminal deoxynucleotidyl transferase-mediated X-dUTP nick end labeling) was used to label the apoptosis of lymphocytes surrounding the islet graft. The SABC method was used to label the expression of Fas ligand in co-transplantation. RESULTS: Islet co-transplantation with 1 x 10(7) sertoli cell reversed the diabetic state for more than 60 days in 100% (6/6) of the chemically diabetic SD recipients. Similar grafts consisting of islet alone or islet plus 1 x 10(5)-sertoli cell survived only for 5 - 6 days. Apoptosis of the lymphocytes surrounding the islet was quite clear. CONCLUSIONS: Co-transplantation islet with FasL(+) sertoli cell induces local immune privilege and allows long-term graft survival without systemic immunosuppression.

Animals↗
PubMed1999

[Polymorphism at cholesteryl ester transfer protein gene loci in patients with gallstone].

This study was designed to reveal the association between the polymorphism of cholesteryl ester transfer protein (CETP) gene loci and gallbladder stone disease. By means of polymerase chain reaction (PCR) and restriction fragment length polymorphisms (RFLEs) of CETP taqIB, BamHI genes were examined in 104 patients subjected to cholecystectomy for symptomatic gallstone disease and 68 healthy controls. The distribution of CETP taqIB polymorphism in the patients with gallstones differed significantly from that of the controls. The B1 allele and B1B1 jects were more frequently revealed in patients with gallstones (0.523, vs 0.346, 0.288 vs 0.1176, P < 0.05). The B2 allele and the B2B2 jects appeared in the controls more frequently (0.654 vs 0.477, 0.4264 vs 0.242, P < 0.05). The H1 allele, H2 allele and H1H1 genotypic, H2H2 genotypic frequencies of the patients with gallstones were not significantly different from those of the controls (P > 0.05). The results suggest that B1 allele is the major gene in the patients with gallstones, and B2 allele is more frequently revealed in the controls.

Adult↗
PubMed1999

[Changes of telomere length in human nasopharyngeal carcinoma].

Using Southern hybridization, we analysed the telomere length from thirty patients with nasopharyngeal carcinoma and demonstrated telomere reduction in these individuals when compared with their age-matched controls. Of the 30 samples, 16.67% had telomere elongation, 76.67% had telomere reduction and 6.67% exhibited equal lengths as compared with the controls. Analysis of leukocytes from 30 controls indicated that the telomere length decreased (average 39 base Pairs Per year) with aging and a statistically significant correlation between the length and age was noted (r = -0.3913, P < 0.05). These results suggest that the consequences of telomere shortening in nasopharyngeal carcinoma may lead to chromosome instability.

Adult↗
PubMed1999

[Change of high density lipoprotein receptor of hepatocyte during cholesterol gallstone formation in rabbit model].

In order to study the formation of cholesterol gallstone through rabbit model which was induced by high cholesterol diet (HCD), we investigated the high density lipoprotein receptor (HDLr) activities of hepatocytes, total bile acids and cholesterol of common duct bile at 1 week(1 w), 2 weeks(2 w), 3 weeks (3 w) and 4 weeks(4 w) in comparison with those of a control group respectively. The results were as follows: 1. The HDLr Bmax decreased and the kd value increased significantly (1 w group vs control group, P < 0.05); In 2 w group the two variables recovered to the level of control group; and after that, the HDLr Bmax increased and Kd value decreased markedly (3 w and 4 w groups vs control group, P < 0.05). 2. Total bile acids in bile increased slightly in 1 w group (vs control group, P > 0.05), then decreased in 2 w, 3 w and 4 w groups (4 w group vs control group, P < 0.05). 3. The concentration of cholesterol in bile increased gradually as the time of feeding HCD went on (3 w and 4 w groups vs control group, P < 0.05). The results demonstrated that owing to the intake of HCD with the passage of time, the activity of HDLr was up at the beginning and down gradually in the rest period. The change in concentrations of bile acids was similar to that of HDLr, and the concentration of cholesterol in bile was foreign to the change of HDLr. These results suggest that the decrease of HDLr activity may cause the absence of material for bile acids synthesis and it may play an important role in the formation of gallstone.

Animals↗