BackgroundAlthough HIV can infect several cellular subsets, such as CD4+ T lymphocytes and macrophages, it remains unclear whether an HIV infection in macrophages supports cytotoxic T lymphocyte (CTL) escape. Here, we tested two naturally-arising mutations located in the well-conserved polyproline region of Nef for their effects on CTL recognition, Nef's functionality, and viral replication capacity in macrophages. These mutations were selected because they are known to cause CTL escape in the context of T lymphocytes.FindingsMonocyte-derived macrophages (MDMs) infected with the wild-type virus, but not with variant viruses, were efficiently killed by CTL clones targeting Nef epitopes, VY8 (VPLRPMTY) and RY11 (RPQVPLRPMTY). The CTL-escape mutation, Arg75Thr, or Arg75Thr/Tyr85Phe double mutation, reduced the HLA class I down-regulation activity and, interestingly, increased the susceptibility of virus-infected MDMs to recognition by CTLs targeting a different epitope. The same mutations reduced the CCR5, but not CD4, down-regulation activity. Moreover, the Nef variants were impaired for Hck activation and enhancement of viral replication in MDMs.ConclusionsThese results suggest that HIV-infected MDMs are killed by CTLs targeting Nef epitopes, contributing to selection and adaptation of CTL-escape viral variants.
Antigen cross-reactivity is an inbuilt feature of the T cell compartment. However, little is known about the flexibility of T cell recognition in the context of genetically variable pathogens such as HIV-1. In this study, we used a combinatorial library containing 24 billion octamer peptides to characterize the cross-reactivity profiles of CD8+ T cells specific for the immunodominant HIV-1 subtype B Nef epitope VY8 (VPLRPMTY) presented by HLA-B*35∶01. In conjunction, we examined naturally occurring antigenic variations within the VY8 epitope. Sequence analysis of plasma viral RNA isolated from 336 HIV-1-infected individuals revealed variability at position (P) 3 and P8 of VY8; Phe at P8, but not Val at P3, was identified as an HLA-B*35∶01-associated polymorphism. VY8-specific T cells generated from several different HIV-1-infected patients showed unique and clonotype-dependent cross-reactivity footprints. Nonetheless, all T cells recognized both the index Leu and mutant Val at P3 equally well. In contrast, competitive titration assays revealed that the Tyr to Phe substitution at P8 reduced T cell recognition by 50–130 fold despite intact peptide binding to HLA-B*35∶01. These findings explain the preferential selection of Phe at the C-terminus of VY8 in HLA-B*35∶01+ individuals and demonstrate that HIV-1 can exploit the limitations of T cell recognition in vivo.
Cara sitasi: Damayanti W, Rochima E, Hasan Zahidah. 2016. Aplikasi kitosan sebagai antibakteri pada filet patin selama penyimpanan suhu rendah. Jurnal Pengolahan Hasil Perikanan Indonesia 19(3): 321-328. AbstrakPenelitian ini bertujuan untuk mendapatkan konsentrasi kitosan yang optimal sebagai bahan antibakteri dengan masa simpan filet patin paling lama pada penyimpanan suhu rendah (5-10 o C). Metode yang digunakan yaitu metode eksperimental dengan rancangan acak lengkap, dengan empat perlakuan dan tiga ulangan. Filet patin direndam dengan perlakuan kitosan 0%, 1%, 2% dan 3% selama tiga menit, dikemas dengan styrofoam dan plastik wrap, kemudian disimpan pada suhu rendah. Pengamatan dilakukan pada hari ke-1, 3, 5, 6, 7, 9, 10, 11 dan 12. Parameter yang diamati meliputi total koloni bakteri, derajat keasaman (pH), susut bobot, dan aktivitas antibakteri kitosan menggunakan metode difusi cakram. Hasil penelitian disimpulkan bahwa kitosan 2% adalah konsentrasi yang optimal untuk penyimpanan filet patin pada suhu rendah hingga hari ke-11, dengan total koloni bakteri 6,7 x10 5 cfu/g, pH 6,67 dan susut bobot sebanyak 6,78%. Kitosan juga memiliki kemampuan aktibakteri yang lebih tinggi terhadap Escherichia coli (bakteri Gram negatif) dibandingkan pada Staphylococcus aureus dan Bacillus subtilis (bakteri Gram positif).Kata kunci: antibakteri, filet patin, kitosan, suhu rendah Abstract This research were to obtain the optimal concentration of chitosan as an antibacterial material wich had the longest of storage period of pangasius fillet at low temperature storage (5-10 o C). The method used is an experimental method with a completely randomized design, four treatments and three replications. Pangasius fillet was soaked with chitosan 0%, 1%, 2% and 3% for 3 minutes, then packed with styrofoam and plastic wrap and stored at low teperature. The observation were made on day 1st, 3rd, 5th, 6th ,7th, 9th,10th, 11th and 12th. The parameters observed total bacterial colonies, the degree of acidity (pH), weight loss, and antibacterial activity of chitosan using disc diffusion methods. The conclusion of research was that the 2% chitosan is optimal concentration for pangasius fillet storage at a low temperature until day 11th, with a total 6.7 X10 5 cfu/g of bacterial colonies, pH 6.67 and total 6,78 % of weight loss.Chitosan also has a higher antibacterial capability against Escherichia coli (Gram negative bacteria) than Staphylococcus aureus and Bacillus subtilis (Gram positive bacteria).
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