| 51. |
- Sheik-Khalil, Enas, et al.
(författare)
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Automated image-based assay for evaluation of HIV neutralization and cell-to-cell fusion inhibition
- 2014
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Ingår i: BMC Infectious Diseases. - : Springer Science and Business Media LLC. - 1471-2334. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Background: Standardized techniques to detect HIV-neutralizing antibody responses are of great importance in the search for an HIV vaccine. Methods: Here, we present a high-throughput, high-content automated plaque reduction (APR) assay based on automated microscopy and image analysis that allows evaluation of neutralization and inhibition of cell-cell fusion within the same assay. Neutralization of virus particles is measured as a reduction in the number of fluorescent plaques, and inhibition of cell-cell fusion as a reduction in plaque area. Results: We found neutralization strength to be a significant factor in the ability of virus to form syncytia. Further, we introduce the inhibitory concentration of plaque area reduction (ICpar) as an additional measure of antiviral activity, i.e. fusion inhibition. Conclusions: We present an automated image based high-throughput, high-content HIV plaque reduction assay. This allows, for the first time, simultaneous evaluation of neutralization and inhibition of cell-cell fusion within the same assay, by quantifying the reduction in number of plaques and mean plaque area, respectively. Inhibition of cell-to-cell fusion requires higher quantities of inhibitory reagent than inhibition of virus neutralization.
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| 52. |
- Shi, Y, et al.
(författare)
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A new cell line-based neutralization assay for primary HIV type 1 isolates
- 2002
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Ingår i: AIDS Research and Human Retroviruses. - : Mary Ann Liebert Inc. - 1931-8405 .- 0889-2229. ; 18:13, s. 957-967
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Tidskriftsartikel (refereegranskat)abstract
- Simple and standardized assays for detection and quantification of neutralizing antibodies to primary HIV-1 isolates are needed in research on HIV-1 vaccines and pathogenesis. Here we describe a new HIV-1 neutralization assay that is based on plaque formation in U87.CD4-CCR5 and U87.CD4-CXCR4 cells, which is an attractive alternative to peripheral blood mononuclear cell-based assays. Infected cells form syncytia, that is, plaques, that can be stained with hematoxylin and enumerated by light microscopy. Neutralization is determined by the ability of a serum to reduce the number of plaque-forming units (PFU) relative to controls exposed to medium or negative serum. The intraassay variation of the plaque-forming unit determinations was tested with 15 serum-virus combinations and showed good reproducibility. The differences ranged from -19 to +27% and had a standard deviation of +/-9.1%. On the basis of these data the cutoff for neutralization (i.e., plaque reduction) was set to 30% (3.3 standard deviations). Virus titration experiments showed that neutralization results were dependent on virus dose and therefore the neutralization assays should be performed with a virus dose of 10-100 PFU/well. The reproducibility of the new neutralization assay was tested with 4 primary viruses and 9 sera for a total of 20 virus-serum combinations. The mean difference in neutralization (i.e. plaque reduction) determinations performed on different days was as small as 11%. None of 10 Swedish sera and I Ugandan plasma pool from HIV-1-uninfected subjects were positive for neutralization, indicating that the assay has high specificity. In summary, the new U87.CD4 cell line-based neutralization assay for primary HIV-1 isolates is a highly reproducible, sensitive, and high-throughput assay that is well suited for large-scale HIV-1 neutralization studies.
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| 53. |
- Shi, Y, et al.
(författare)
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Evolution of human immunodeficiency virus type 2 coreceptor usage, autologous neutralization, envelope sequence and glycosylation
- 2005
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Ingår i: Journal of General Virology. - : Microbiology Society. - 1465-2099 .- 0022-1317. ; 86, s. 3385-3396
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Tidskriftsartikel (refereegranskat)abstract
- To investigate why human immunodeficiency virus type 2 (HIV-2) is less virulent than HIV-1, the evolution of coreceptor usage, autologous neutralization, envelope sequence and glycosylation was studied in sequentially obtained virus isolates and sera from four HIV-2-infected individuals. Neutralization of primary HIV-2 isolates was tested by a cell line-based assay and IgG purified from patients' sera. Significant autologous neutralization was observed for the majority (39 of 54) of the HIV-2 serum-virus combinations tested, indicating that neutralization escape is rare in HIV-2 infection. Furthermore, sera from 18 HIV-2 patients displayed extensive heterologous cross-neutralization when tested against a panel of six primary HIV-2 isolates. This indicates that HIV-2 is intrinsically more sensitive to antibody neutralization than HIV-1. In line with earlier reports, HIV-2 isolates could use several alternative receptors in addition to the major coreceptors CCR5 and CXCR4. Intrapatient evolution from CCR5 use to CXCR4 use was documented for the first time. Furthermore, CXCR4 use was linked to the immunological status of the patients. Thus, all CXCR4-using isolates, except one, were obtained from patients with CD4 counts below 200 cells mu l(-1). Sequence analysis revealed an association between coreceptor usage and charge of the V3 loop of the HIV-2 envelope, as well as an association between the rate of disease progression and the glycosylation pattern of the envelope protein. Furthermore, HIV-2 isolates had fewer glycosylation sites in the V3 domain than HIV-1 (two to three versus four to five). It is proposed here that HIV-2 has a more open and accessible V3 domain than HIV-1, due to differences in glycan packing, and that this may explain its broader coreceptor usage and greater sensitivity to neutralizing antibodies.
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| 54. |
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| 55. |
- Sterjovski, Jasminka, et al.
(författare)
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Asn 362 in gp120 contributes to enhanced fusogenicity by CCR5-restricted HIV-1 envelope glycoprotein variants from patients with AIDS
- 2007
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Ingår i: Retrovirology. - : Springer Science and Business Media LLC. - 1742-4690. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Background: CCR5-restricted (R5) human immunodeficiency virus type 1 (HIV-1) variants cause CD4+ T-cell loss in the majority of individuals who progress to AIDS, but mechanisms underlying the pathogenicity of R5 strains are poorly understood. To better understand envelope glycoprotein (Env) determinants contributing to pathogenicity of R5 viruses, we characterized 37 full-length R5 Envs from cross-sectional and longitudinal R5 viruses isolated from blood of patients with asymptomatic infection or AIDS, referred to as pre-AIDS (PA) and AIDS (A) R5 Envs, respectively. Results: Compared to PA-R5 Envs, A-R5 Envs had enhanced fusogenicity in quantitative cell-cell fusion assays, and reduced sensitivity to inhibition by the fusion inhibitor T-20. Sequence analysis identified the presence of Asn 362 (N362), a potential N-linked glycosylation site immediately N-terminal to CD4-binding site (CD4bs) residues in the C3 region of gp120, more frequently in AR5 Envs than PA-R5 Envs. N362 was associated with enhanced fusogenicity, faster entry kinetics, and increased sensitivity of Env-pseudotyped reporter viruses to neutralization by the CD4bs-directed Env mAb IgG1b12. Mutagenesis studies showed N362 contributes to enhanced fusogenicity of most A-R5 Envs. Molecular models indicate N362 is located adjacent to the CD4 binding loop of gp120, and suggest N362 may enhance fusogenicity by promoting greater exposure of the CD4bs and/or stabilizing the CD4-bound Env structure. Conclusion: Enhanced fusogenicity is a phenotype of the A-R5 Envs studied, which was associated with the presence of N362, enhanced HIV-1 entry kinetics and increased CD4bs exposure in gp120. N362 contributes to fusogenicity of R5 Envs in a strain dependent manner. Our studies suggest enhanced fusogenicity of A-R5 Envs may contribute to CD4+ T-cell loss in subjects who progress to AIDS whilst harbouring R5 HIV-1 variants. N362 may contribute to this effect in some individuals.
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| 56. |
- Tranell, Anna, 1982-, et al.
(författare)
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Indole-related compounds from the National Cancer Institute (USA) repository do not inhibit HIV-1 replication in primary blood mononuclear cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Indole derived substances have been shown previously to inhibit HIV-1 replication, presumably by interfering with cellular splicing factors of the SR protein family. Here we have tested the effect of indole-related substances obtained from the NCI repository on HIV-1 gene expression in transient transfections and in primary cell cultures infected by X4 and R5 tropic HIV-1 strains. Although these substances displayed a significant inhibitory effect on HIV-1 gene expression in transiently transfected cells, they did not inhibit replication of HIV-1 in primary peripheral blood mononuclear cells. These results demonstrate important differences between transfection assays performed in cell lines and infection assays performed in primary cells and indicate that only a subset of indole-related compounds can inhibit HIV-1 replication.
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| 57. |
- Tranell, Anna, et al.
(författare)
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Inhibition of splicing by serine-arginine rich protein 55 (SRp55) causes the appearance of partially spliced HIV-1 mRNAs in the cytoplasm
- 2011
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 157:1, s. 82-91
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that SRp55 inhibits splicing from HIV-1 exon 3, thereby generating partially spliced mRNAs encoding HIV-1 vpr. Here we show that SRp55 also inhibits splicing from HIV-1 exon 5 to generate HIV-1 vpu/env mRNA, albeit with lower efficiency. We also show that inhibition of HIV-1 splicing by SRp55 causes the appearance of partially spliced vpu, env and vpr mRNAs in the cytoplasm. SRp55 could also induce production of extracellular p24gag from a rev-defective HIV-1 provirus. These results indicate that SRp55 aids in the generation of partially spliced and unspliced HIV-1 mRNAs.
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| 58. |
- Tranell, Anna, et al.
(författare)
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Serine- and Arginine-rich Proteins 55 and 75 (SRp55 and SRp75) Induce Production of HIV-1 vpr mRNA by Inhibiting the 5 '-Splice Site of Exon 3
- 2010
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 285:41, s. 31537-31547
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Tidskriftsartikel (refereegranskat)abstract
- HIV-1 non-coding exon 3 can either be spliced to exons 4, 4a, 4b, 4c, and 5 to generate tat, rev, and nef mRNAs or remain unspliced to produce the 13a7 vpr mRNA. Here we show that serine-and arginine-rich proteins 55 and 75 (SRp55 and SRp75) inhibit splicing from the 5'-splice site of exon 3 thereby causing an accumulation of the partially unspliced 13a7 vpr mRNA. In contrast, serine- and arginine-rich protein 40 (SRp40) induces splicing from exon 3 to exon 4, thereby promoting the production of the 1347 tat mRNA. We demonstrate that SRp55 stimulates vpr mRNA production by interacting with the previously identified HIV-1 splicing enhancer named GAR and inhibiting its function. This inhibition requires both serine arginine-rich and RNA-binding domains of SRp55, indicating that production of HIV-1 vpr mRNA depends on the interaction of SRp55 with an unknown factor.
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| 59. |
- Vinner, Lasse, et al.
(författare)
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Sequence analysis of HIV-1 isolates from Guinea-Bissau: selection of vaccine epitopes relevant in both West African and European countries.
- 2011
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Ingår i: APMIS : acta pathologica, microbiologica, et immunologica Scandinavica. - : Wiley. - 1600-0463. ; 119:8, s. 487-497
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Tidskriftsartikel (refereegranskat)abstract
- For a CD8 epitope-based vaccine to match different geographic locations, the targeted epitopes for cytotoxic T-lymphocytes (CTLs) must be present in the local circulating HIV-1 strains. Secondly, the vaccine epitopes should match the host population HLA types. We characterized two new HIV-1 isolates from Guinea-Bissau. Also, we have identified 15 subdominant CD8 epitopes representing common HLA super-types theoretically covering most HLA alleles in any population. Herein we demonstrate that the selected vaccine epitopes are well conserved and simultaneously present in sequences from West Africa and Denmark. Use of the selected epitopes will likely ensure 10 immune targets in the majority of candidates for experimental therapeutic vaccination in both geographic regions. Our results warrant testing of the selected vaccine epitopes in both geographic locations.
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| 60. |
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