The biological and practical significance of antigenic variability in protective T cell responses against Theileria parva

The evolution of antigenically distinct pathogen strains that fail to cross-protect is well documented for pathogens controlled primarily by humoral immune responses. Unlike antibodies, which recognise native proteins, protective T cells can potentially recognise epitopes in a variety of proteins that are not necessarily displayed on the pathogen surface. Moreover, individual hosts of different MHC genotypes generally respond to different sets of epitopes. It is therefore less easy to envisage how strain restricted immunity can arise for pathogens controlled by T cell responses, particularly in antigenically complex parasites. Nevertheless, strain restricted immunity is clearly a feature of a number of parasitic infections, where immunity is known to be mediated by T cell responses. One such parasite is Theileria parva which induces potent CD8 T cell responses that play an important role in immunity. CD8 T cells specific for parasitized lymphoblasts exhibit strain specificity, which appears to correlate with the ability of parasite strains to cross-protect. Studies using recently identified T. parva antigens recognised by CD8 T cells have shown that the strain restricted nature of immunity is a consequence of the CD8 T cell response in individual animals being focused on a limited number of dominant polymorphic antigenic determinants. Responses in animals of different MHC genotypes are often directed to different parasite antigens, indicating that, at the host population level, a larger number of parasite proteins can serve as targets for the protective T cell response. Nevertheless, the finding that parasite strains show overlapping antigenic profiles, probably as a consequence of sexual recombination, suggests that induction of responses to an extended but limited set of antigens in individual animals may overcome the strain restricted nature of immunity.     

Analysis of neutral glycosphingolipids from Trypanosoma brucei

Neutral glycosphingolipids (GSLs) were isolated from Trypanosoma brucei and analyzed by thin-layer chromatography (TLC), TLC/secondary ion mass spectrometry (TLC/SIMS), and liposome immune lysis assay (LILA). Three species of neutral GSLs, designated as N-1, -2, and -3 were separated on TLC. N-1 GSL migrated very close to glucosylceramide (GlcCer) and N-2 GSL showed the same mobility as lactosylceramide (LacCer). On the other hand, the mobility of N-3 GSL on the TLC plate was slower than globotetraosylceramide (Gb4). In order to characterize the molecular species of neutral GSLs from T. brucei, N-1, -2 and -3 GSLs were analyzed by TLC/SIMS. The TLC/SIMS analysis of N-1 of the parasites revealed a series of (M–H)⁻ ions from m/z 698 to 825 representing the molecular mass range of ceramide monohexoside (CMH) (GlcCer or galactosylceramide). On the other hand, the TLC/SIMS spectra of N-2 GSL revealed a series of (M–H)⁻ ions from m/z 944–987 indicating the molecular mass range of LacCer. In the TLC/SIMS analysis of N-3 GSL, however, the characteristic molecular ions that can elucidate the structure of N-3 GSL were not obtained. In order to confirm the results obtained from TLC/SIMS, N-1, -2, and -3, GSLs were tested by LILA with specific antibodies against GlcCer, LacCer, and Gb4, respectively. N-1 GSL had reactivity to anti-GlcCer antibody and N-2 GSL reacted with the antibody against LacCer. However, N-3 GSL was not recognized by anti-Gb4 antibody. Using anti-GlcCer and anti-LacCer antibodies, furthermore, we studied the expression of GlcCer and LacCer in T. brucei parasites. Both GlcCer and LacCer were detected on the cell surface of T. brucei.     

马骡急性致死性肠炎病原体药敏试验

作者以急性致死性肠炎病马血浆中的原虫(简称虫体)及其纯培养液中的虫体为试虫,选用19种试敏药物,按试管液体二倍稀释法稀释药液,进行试管内药物敏感试验。经统计学处理,毒力线及毒力比测定,并用SSR法对各药药效进行多重比较,根据给药四小时药物作用结果,则筛选出呋喃唑酮、盐酸左咪唑、高锰酸钾、喹乙醇、新胂凡纳明,酒石酸锑钾等六种药物为对虫体的敏感药。以呋喃唑酮为标准药,各剂与其毒力比分别为:1、0.5754、0.1148、0.0575、0.0408、0.0363。F4h353.086,F8h100.744,F4h和F8h均大于f00.05(6,12)=3,各药抑虫率均数具有显著差异,呋喃唑酮明显优于其它各药。故确定呋喃唑酮,盐酸左咪唑为首选药;高锰酸钾,新胂凡纳明、酒石酸锑钾为次选药:喹乙醇为辅助治疗药.并证实各药高浓度药液及给药4或8小时药物作用最强,均可供临床试用。     

Influence of texture on habitable pore space and bacterial-protozoan populations in soil

Summary Soil texture affects pore space, and bacterial and protozoan populations in soil. In the present study we tested the hypothesis that bacteria are more protected from protozoan predation in fine-textured soils than in coarse-textured soils because they have a larger volume of protected pore space available to them. The experiment consisted of three sterilized Orthic Black Chernozemic soils (silty clay, clay loam, and sandy loam) inoculated with bacteria, two treatments (with and without protozoa), and five sampling dates. The soils were amended with glucose and mineral N on day 0. On day 4 bacterial numbers in all three soils were approximately 3×10⁹ g^–1 soil. The greatest reduction in bacteria due to protozoan grazing occurred between day 4 and day 7. Compared to the treatment without protozoa, bacteria in the treatment with protozoa were reduced by 68, 50, and 75% in the silty clay, clay loam, and sandy loam, respectively. On day 4, 2 days after the protozoan inoculation, all protozoa were active. The numbers were 10330, 4760, and 15 380 g^–1 soil for the silty clay, clay loam, and sandy loam, respectively. Between day 4 and day 7, the period of greatest bacterial decline, total protozoa increased greatly to 150480, 96160, and 192100 g^–1 soil for the three soils, respectively. Most protozoa encysted by day 7. In all soils the addition of protozoa significantly increased CO₂–C evolution per g soil relative to the treatment without protozoa. Our results support the hypothesis that bacteria are more protected from protozoan predation in fine-textured soils than in coarse-textured soils.     

Effect of anti-ganglioside antibody in experimental Trypanosoma brucei infection in mice

The effect of antibody against ganglioside antigen on Trypanosoma brucei parasites was examined in vitro and in vivo using anti-ganglioside GM1 (AGM-1) monoclonal antibody. The antibody showed complement-dependent cytotoxicity against T. brucei with mouse complement. Furthermore, mice given AGM-1 were challenged intraperitoneally with T. brucei. Although all non-treated control mice died within six days after infection, all of AGM-1-injected mice had survived by six days post-infection. These data suggest that antibody against ganglioside antigen on T. brucei has potential in protection against T. brucei infection.     

Protozoan response to addition of the bacteria Mycobacterium chlorophenolicum and Pseudomonas chlororaphis to soil microcosms

 Protozoa are important predators of bacteria in soil and protozoan predation is one of the main factors responsible for the decline of bacterial populations introduced into soil. Bacteria, however, are not equally susceptible to protozoan predation. We have studied the response of indigenous protozoan populations to the introduction of the polychlorophenol-degrading bacterium Mycobacterium chlorophenolicum PCP-1 (DSM 43826), and Pseudomonas chlororaphis (ATCC 43928), into soil microcosms. Introduction of P. chlororaphis to the soil resulted in a huge increase in the numbers of heterotrophic flagellates and naked amoebae during the first 8 days of the experiment. Addition of M. chlorophenolicum to soil caused only a slight increase in protozoan numbers, which was similar to the increase caused by addition of water. There was no indication that addition of M. chlorophenolicum to soil resulted in any increase in the number of protozoa able to feed on this bacterium. The number of colony forming units (CFU) decreased rapidly in the treatment amended with P. chlororaphis cells, whereas there was no decrease in CFUs in the M. chlorophenolicum treatment. The only slight increase in protozoan numbers in the M. chlorophenolicum treatment, as well as the apparently low mortality rate of M. chlorophenolicum in the soil microcosms, coincided with significantly lower soil respiration in the soil microcosms amended with M. chlorophenolicum compared to those amended with P. chlororaphis. The results suggest that the indigenous soil protozoa did not graze on M. chlorophenolicum at all, presumably because it is not a suitable food source. Received: 23 February 2000     

Protozoan predation and the turnover of soil organic carbon and nitrogen in the presence of plants

Summary The impact of protozoan grazing on the dynamics and mineralization of ¹⁴C- and ¹⁵N-labelled soil organic material was investigated in a microcosm experiment. Sterilized soil was planted with wheat and either inoculated with bacteria alone or with bacteria and protozoa or with bacteria and a 1:10 diluted protozoan inoculum. ¹⁴C–CO₂ formation was continuously monitored. It served as an indicator of microbial activity and the respiration of soil organic C. The activity of protozoa increased the turnover of ¹⁴C-labelled substrates compared to soil without protozoa. The accumulated ¹⁴C–CO₂ evolved from the soils with protozoa was 36% and 53% higher for a 1:10 and for a 1:1 protozoan inoculum, respectively. Protozoa reduced the number of bacteria by a factor of 2. In the presence of protozoa, N uptake by plants increased by 9% and 17% for a 1:10 and a 1:1 protozoan inoculum, respectively. Both plant dry matter production and shoot: root ratios were higher in the presence of protozoa. The constant ratio of ¹⁵N: ¹⁴⁺¹⁵N in the plants for all treatments indicated that in the presence of protozoa more soil organic matter was mineralized. Bacteria and protozoa responded very rapidly to the addition of water to the microcosms. The rewetting response in terms of the ¹⁴C–CO₂ respiration rate was significantly higher for 1 day in the absence and for 2 days in the presence of protozoa after the microcosms had been watered. It was concluded that protozoa improved the mineralization of N from soil organic matter by stimulating the turnover of bacterial biomass. Pulsed events like the addition of water seem to have a significant impact on the dynamics of food-chain reactions in soil in terms of C and N mineralization.Communication No. 19 of the Dutch Programme on Soil Ecology of Arable Farming Systems     

Occurrence of Trypanosoma evansi in Horses in the State of Minas Gerais,Brazil

Ttrypanosomosis caused by Trypanosoma evansi is a condition that causes significant losses to farmers in endemic areas. This study aimed to report one case of trypanosomiasis in the municipality of Itabira, state of Minas Gerais, Brazil. In November 2010, on a farm with 16 horses, three horses had clinical signs of anemia, limb edema, weight loss, lameness, muscle atrophy, and incoordination of the hind limbs. Trypanosomosis was suspected, and the animals with clinical signs were treated with two doses of diminazene aceturate (7 mg/kg, intramuscular) every 7 days; the treated animals recovered from the clinical symptoms. Blood samples were collected from six horses on the farm, including the three treated animals, to perform polymerase chain reaction specific for T evansi. Four samples were polymerase chain reaction negative, including those collected from three treated horses. However, two other asymptomatic horses were positive for the parasite based on the molecular testing. Based on the results, we concluded that the initial clinical suspect of trypanosomosis was correct, and the treatment used was effective. Probably the disease was introduced to Minas Gerais State through a stallion, which acquired the infection in an endemic area in southern Brazil.     

AM真菌与原生动物在花生上双接种效应初探

通过AM真菌和原生动物对花生进行双接种 ,研究他们之间的相互作用。结果表明 :双接种比AM真菌单接种降低了AM真菌侵染率 ;比对照增加了植株干物重 ;比对照提高氮、磷吸收量 ,最高可分别提高 12 0 %和 87 7%。原生动物的主要作用在于改善作物氮素营养 ,而AM菌根主要作用在于改善作物磷素营养 ,其协同作用促进了植株的生长及营养状况