Publications by authors named "Tomoyuki Maekawa"

5 Publications

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HLA-B*35: 05 is a protective allele with a unique structure among HIV-1 CRF01_AE-infected Thais, in whom the B*57 frequency is low.

AIDS 2014 Apr;28(7):959-67

Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Sakamoto, Nagasaki City, Nagasaki, Japan.

Objective: To identify protective human leukocyte antigen (HLA) alleles in an HIV-infected south-east Asian population, in whom HLA-B*57 prevalence is lower than other ethnic groups, and HIV-1 CRF01_AE is the dominant circulating subtype.

Design: Cross-sectional study of Thai patients with chronic HIV infection.

Methods: Five hundred and fifty-seven HIV-1 CRF01_AE-infected Thais were recruited. Their HLA type and viral load were determined to statistically analyze the association of each allele in viral control. In-silico molecular dynamics was also used to evaluate the effect of HLA structure variants on epitope binding.

Results: HLA-B*35:05 was identified as the most protective allele (P=0.003, q=0.17), along with HLA-B*57:01 (P=0.044, q=0.31). Structurally, HLA-B*35:05 belonged to the HLA-B*35-PY group of HLA-B*35 alleles; however, unlike the other HLA-B*35 alleles that carry Arg (R) at residue 97, it has unique sequences at T94, L95, and S97, located within the peptide-binding groove. Analysis of the three-dimensional HLA structure and molecular dynamics indicates that S97 in HLA-B*35:05 leads to less flexibility in the groove, and shorter distances between the α-helixes compared with the disease-susceptible HLA-B*35-PY allele, HLA-B*35:01.

Conclusion: These data indicate the existence of a protective effect of HLA-B*57 across ethnic groups and highlight HLA-B*35:05 as an allele uniquely protective in subtype CRF01_AE-infected Thais. The divergence of HLA-B*35:05 from conventional HLA-B*35-PY structural sequences at the peptide-binding groove is consistent with previous studies that have identified HLA residue 97 as strongly influential in shaping HLA impact on immune control of HIV, and that a more restricted peptide-binding motif may be associated with improved control.
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April 2014

Development of a novel in silico docking simulation model for the fine HIV-1 cytotoxic T lymphocyte epitope mapping.

PLoS One 2012 27;7(7):e41703. Epub 2012 Jul 27.

Institute of Tropical Medicine, Nagasaki University, Nagasaki City, Nagasaki, Japan.

Introduction: Class I HLA's polymorphism has hampered CTL epitope mapping with laborious experiments. Objectives are 1) to evaluate the novel in silico model in predicting previously reported epitopes in comparison with existing program, and 2) to apply the model to predict optimal epitopes with HLA using experimental results.

Materials And Methods: We have developed a novel in silico epitope prediction method, based on HLA crystal structure and a peptide docking simulation model, calculating the peptide-HLA binding affinity at four amino acid residues in each terminal. It was applied to predict 52 HIV best-defined CTL epitopes from 15-mer overlapping peptides, and its predictive ability was compared with the HLA binding motif-based program of HLArestrictor. It was then used to predict HIV-1 Gag optimal epitopes from previous ELISpot results.

Results: 43/52 (82.7%) epitopes were detected by the novel model, whereas 37 (71.2%) by HLArestrictor. We also found a significant reduction in epitope detection rates for longer epitopes in HLArestrictor (p = 0.027), but not in the novel model. Improved epitope prediction was also found by introducing both models, especially in specificity (p<0.001). Eight peptides were predicted as novel, immunodominant epitopes in both models.

Discussion: This novel model can predict optimal CTL epitopes, which were not detected by an existing program. This model is potentially useful not only for narrowing down optimal epitopes, but predicting rare HLA alleles with less information. By introducing different principal models, epitope prediction will be more precise.
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April 2013

Positive selection of Toll-like receptor 2 polymorphisms in two closely related old world monkey species, rhesus and Japanese macaques.

Immunogenetics 2012 Jan 9;64(1):15-29. Epub 2011 Jul 9.

Department of Immunogenetics, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.

Toll-like receptor 2 (TLR2) plays an important role in the recognition of a variety of pathogenic microbes. In the present study, we compared polymorphisms of TLR2 locus in two closely related old world monkey species, rhesus monkey (Macaca mulatta) and Japanese monkey (Macaca fuscata). By nucleotide sequencing of the third exon of TLR2 gene from 21 to 35 respective individuals, we could assign 17 haplotype combinations of 17 coding SNPs of ten non-synonymous and seven synonymous substitutions. A non-synonymous substitution at codon position 326 appeared to be differentially fixed in each species, asparagine for M. mulatta whereas tyrosine for M. fuscata, and may contribute to certain functional properties because it locates in the region contributing to ligand binding and interaction with dimerization partner of TLR2-TLR1 heterodimeric complex. Although TLR2 alleles have diverged to similar extent in both species, they have evolved in significantly different ways; TLR2 of M. fuscata has undergone purifying selection while the membrane-proximal part of the extracellular domain of M. mulatta TLR2 exhibits higher rates of non-synonymous substitutions, indicating a trace of Darwinian positive selection.
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January 2012

Receptor for advanced glycation end products binds to phosphatidylserine and assists in the clearance of apoptotic cells.

EMBO Rep 2011 Apr 11;12(4):358-64. Epub 2011 Mar 11.

Department of Advanced Preventive Medicine for Infectious Disease, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan.

Clearance of apoptotic cells is necessary for tissue development, homeostasis and resolution of inflammation. The uptake of apoptotic cells is initiated by an 'eat-me' signal, such as phosphatidylserine, on the cell surface and phagocytes recognize the signal by using specific receptors. In this study, we show that the soluble form of the receptor for advanced glycation end products (RAGE) binds to phosphatidylserine as well as to the apoptotic thymocytes. RAGE-deficient (Rage(-/-)) alveolar macrophages showed impaired phagocytosis of apoptotic thymocytes and defective clearance of apoptotic neutrophils in Rage(-/-) mice. Our results indicate that RAGE functions as a phosphatidylserine receptor and assists in the clearance of apoptotic cells.
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April 2011

Two types of matter economy for the wintering of evergreen shrubs in regions of heavy snowfall.

J Plant Res 2003 Aug 15;116(4):327-30. Epub 2003 May 15.

Department of Biology, School of Education, Waseda University, Tokyo 169-8050, Japan.

Plant adaptation to an environment subject to heavy snowfalls was investigated in four species of evergreen shrubs growing in a Fagus crenata forest in an area of Honshu on the Sea of Japan. These shrubs stored carbohydrates in some organs before the snowy season and were covered with snow for 4-5 months. Aucuba japonica var. borealis, Camellia rusticana, and Ilex crenata var. paludosa maintained a reserve of carbohydrates during the snowy season. In Daphniphyllum macropodum var. humile, the reserve of carbohydrates decreased during winter. The respiration rates in the first three species decreased from autumn to winter, whereas the decrease in D. macropodum was slight. It was found that the first three species could use reserve carbohydrates for the growth of new shoots after the thaw, whereas in the last species the growth of new shoots depends on high photosynthetic activity in late spring. Our findings suggest some types of matter economy in evergreen shrubs for wintering in an environment of heavy snow.
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August 2003