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排序方式: 共有180条查询结果,搜索用时 15 毫秒
81.
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Duvall MG Jaye A Dong T Brenchley JM Alabi AS Jeffries DJ van der Sande M Togun TO McConkey SJ Douek DC McMichael AJ Whittle HC Koup RA Rowland-Jones SL 《Journal of immunology (Baltimore, Md. : 1950)》2006,176(11):6973-6981
Unlike HIV-1-infected people, most HIV-2-infected subjects maintain a healthy CD4+ T cell count and a strong HIV-specific CD4+ T cell response. To define the cellular immunological correlates of good prognosis in HIV-2 infection, we conducted a cross-sectional study of HIV Gag-specific T cell function in HIV-1- and HIV-2-infected Gambians. Using cytokine flow cytometry and lymphoproliferation assays, we show that HIV-specific CD4+ T cells from HIV-2-infected individuals maintained proliferative capacity, were not terminally differentiated (CD57-), and more frequently produced IFN-gamma or IL-2 than CD4+ T cells from HIV-1-infected donors. Polyfunctional (IFN-gamma+/IL-2+) HIV-specific CD4+ T cells were found exclusively in HIV-2+ donors. The disparity in CD4+ T cell responses between asymptomatic HIV-1- and HIV-2-infected subjects was not associated with differences in the proliferative capacity of HIV-specific CD8+ T cells. This study demonstrates that HIV-2-infected donors have a well-preserved and functionally heterogeneous HIV-specific memory CD4+ T cell response that is associated with delayed disease progression in the majority of infected people. 相似文献
83.
Immunologic pressure within class I-restricted cognate human immunodeficiency virus epitopes during highly active antiretroviral therapy 下载免费PDF全文
Casazza JP Betts MR Hill BJ Brenchley JM Price DA Douek DC Koup RA 《Journal of virology》2005,79(6):3653-3663
Cytotoxic T lymphocytes (CTL) and highly active antiretroviral therapy (HAART) are known to exert strong evolutionary pressures on the virus population during human immunodeficiency virus (HIV) infection. However, it is not known whether CTL responses continue to substantially affect viral evolution during treatment. To study the effect of immunologic pressure on viral sequences during HAART, we identified 10 targeted HIV-specific CD8+-T-cell epitopes in five treatment-naive patients, sequenced each epitope in plasma-derived viruses, and then identified evidence of immunologic pressure at these epitopes by comparing the frequency of viral variants in plasma to the frequency of the CD8+-T-cell response for each variant identified. For one of the five patients, evidence of viral evolution was found during therapy. The sequence of the CTL-targeted epitope changed from an apparent escape variant prior to the initiation of therapy, to the sequence that is best recognized by the CTL response after the initiation of therapy, and then finally to a new escape variant during continued therapy. These data show that CTL-mediated pressure can continue to affect viral evolution after the initiation of HAART, even when treatment drives the viral load below detectable levels, and suggest that antiretroviral therapy may preferentially inhibit those virus variants that escape the CTL response. 相似文献
84.
Phylogenetic analyses of the rbcL sequences from haptophytes and heterokont algae suggest their chloroplasts are unrelated 总被引:2,自引:0,他引:2
Using the large subunit of RuBisCo (rbcL) sequences from cyanobacteria,
proteobacteria, and diverse groups of algae and green plants, we evaluated
the plastid relationship between haptophytes and heterokont algae. The rbcL
sequences were determined from three taxa of heterokont algae
(Bumilleriopsis filiformis, Pelagomonas calceolata, and Pseudopedinella
elastica) and added to 25 published sequences to obtain a data set
comprising 1,434 unambiguously aligned sites (approximately 98% of the
total rbcL gene). Higher levels of mutational saturation in third codon
positions were observed by plotting the pairwise substitutions with and
without corrections for multiple substitutions at the same site for first
and second codon positions only and for third positions only. In accordance
with this finding phylogeny reconstructions were completed by omitting
third codon positions, thus using 956 bp in weighted-parsimony and
maximum-likelihood analyses. The midpoint-rooted phylogenies showed two
major clusters, one containing cyanobacteria, glaucocystophytes, a
phototrophic euglenoid, chlorophytes, and embryophytes (the green lineage),
the other containing proteobacteria, haptophytes, red algae, a cryptophyte,
and heterokont algae (the non-green lineage). In the nongreen lineage, the
haptophytes formed a sister group to the clade containing heterokont algae,
red algae, and the cryptophyte Guillardia theta. This branching pattern was
well supported in terms of bootstrap values in weighted- parsimony and
maximum-likelihood analyses (100% and 92%, respectively). However, the
phylogenetic relationship among red algae, heterokonts, and a cryptophyte
taxon was not especially well resolved. A four- cluster analysis was
performed to further explore the statistical significance of the
relationship between proteobacteria, red algae (including and excluding
Guillardia theta), haptophytes, and heterokont algae. This test strongly
favored the hypothesis that the heterokonts and red algae are more closely
related to each other than either is to proteobacteria or haptophytes.
Hence, this molecular study based on a plastid-encoded gene provides
additional evidence for a distant relationship between haptophytes and the
heterokont algae. It suggests an evolutionary scenario in which the
ancestor of the haptophyte lineage engulfed a phototrophic eukaryote and,
more recently, the heterokont lineage became phototrophic by engulfing a
red alga.
相似文献
85.
Overlapping epitopes in human immunodeficiency virus type 1 gp120 presented by HLA A, B, and C molecules: effects of viral variation on cytotoxic T-lymphocyte recognition. 总被引:2,自引:2,他引:0 下载免费PDF全文
C C Wilson S A Kalams B M Wilkes D J Ruhl F Gao B H Hahn I C Hanson K Luzuriaga S Wolinsky R Koup S P Buchbinder R P Johnson B D Walker 《Journal of virology》1997,71(2):1256-1264
Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) are thought to exert immunologic selection pressure in infected persons, yet few data regarding the effects of this constraint on viral sequence variation in vivo, particularly in the highly variable Env protein, are available. In this study, CD8+ HIV type 1 (HIV-1) envelope-specific CTL clones specific for gp120 were isolated from peripheral blood mononuclear cells of four HIV-infected individuals, all of which recognized the same 25-amino-acid (aa) peptide (aa 371 to 395), which is partially contained in the CD4-binding domain of HIV-1 gp120. Fine mapping studies revealed that two of the clones optimally recognized the 9-aa sequence 375 to 383 (SFNCGGEFF), while the two other clones optimally recognized the epitope contained in the overlapping 9-aa sequence 376 to 384 (FNCGGEFFY). Lysis of target cells by the two clones recognizing aa 375 to 383 was restricted by HLA B15 and Cw4, respectively, whereas both clones recognizing aa 376 to 384 were restricted by HLA A29. Sequence variation, relative to the IIIB strain sequence used to identify CTL clones, was observed in autologous viruses in the epitope-containing region in all four subjects. However, poorly recognized autologous sequence variants were predominantly seen for the A29-restricted clones, whereas the clones specific for SFNCGGEFF continued to recognize the predominant autologous sequences. These results suggest that the HLA profile of an individual may not only be important in determining the specificity of CTL recognition but may also affect the ability to recognize virus variants and suppress escape from CTL recognition. These results also identify overlapping viral CTL epitopes which can be presented by HLA A, B, and C molecules. 相似文献
86.
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89.
TOSHIHIRO TOKIWA DAVID MODRÝ AKIRA ITO KATEŘINA POMAJBÍKOVÁ KLÁRA J. PETRŽELKOVÁ SOICHI IMAI 《The Journal of eukaryotic microbiology》2010,57(2):115-120
ABSTRACT. Troglocorys cava n. g., n. sp. is described from the feces of wild eastern chimpanzee, Pan troglodytes schweinfurthii, in Uganda. This new species has a spherical body with a frontal lobe, a long vestibulum, a cytoproct located at the posterior dorsal side of the body, an ovoid macronucleus, a contractile vacuole near the cytoproct, and a large concavity on the left surface of the body. Buccal ciliature is non‐retractable and consists of three ciliary zones: an adoral zone surrounding the vestibular opening, a dorso‐adoral zone extending transversely at the basis of the frontal lobe, and a vestibular zone longitudinally extending in a gently spiral curve to line the surface of the vestibulum. Two non‐retractable somatic ciliary zones comprise arches over the body surface: a short dorsal ciliary arch extending transversely at the basis of the frontal lobe and a wide C‐shaped left ciliary arch in the left concavity. Because of the presence of three ciliary zones in the non‐retractable buccal ciliature, the present genus might be a member of the family Blepharocorythidae, but the large left concavity and the C‐shaped left ciliary arch are unique, such structures have never been described from other blepharocorythids. 相似文献
90.
The worldwide increase in the use of antibiotics as an integral part of poultry and livestock production industry has recently received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria in human beings. To gauge the presence of the aforementioned scenario in the Indian context, a preliminary survey was conducted to assess the use of chlortetracycline (CTC) in 12 commercial layer farms and to quantify and confirm its residue in the egg. Samples of feed and eggs were collected at day 0 (prior to CTC addition), 3rd, 5th and 7th day during treatment and on the 9th and 14th day (2nd and 7th day after withdrawal of CTC) from each of the 12 commercial poultry farms studied. Concentration of CTC in feed was significantly (P<0.01) high on the 3rd, 5th and 7th day. On the 9th day and 14th day CTC concentration in feed was significantly (P<0.01) lower compared to the earlier 3 days studied. A highly significant difference (P<0.01) of the antibiotic residue in egg was observed in all the 5 days with high residual levels of CTC in egg. CTC in feed and its residue in egg were detected even on the 9th and 14th day respectively. 相似文献