scholarly journals Feline Leukemia Virus Envelope Sequences That Affect T-Cell Tropism and Syncytium Formation Are Not Part of Known Receptor-Binding Domains

2000 ◽  
Vol 74 (13) ◽  
pp. 5754-5761 ◽  
Author(s):  
Samuel R. Gwynn ◽  
F. Claire Hankenson ◽  
Adam S. Lauring ◽  
Jennifer L. Rohn ◽  
Julie Overbaugh
Keyword(s):  
Tissue Culture ◽  
T Cells ◽  
Amino Acid ◽  
T Cell ◽  
Envelope Protein ◽  
Leukemia Virus ◽  
Feline Leukemia Virus ◽  
Single Amino Acid ◽  
Binding Domains ◽  
Amino Acid Insertion

ABSTRACT The envelope protein is a primary pathogenic determinant for T-cell-tropic feline leukemia virus (FeLV) variants, the best studied of which is the immunodeficiency-inducing virus, 61C. We have previously demonstrated that T-cell-tropic, cytopathic, and syncytium-inducing viruses evolve in cats infected with a relatively avirulent, transmissible form of FeLV, 61E. The envelope gene of an 81T variant, which encoded scattered single-amino-acid changes throughout the envelope as well as a 4-amino-acid insertion in the C-terminal half of the surface unit (SU) of envelope, was sufficient to confer the T-cell-tropic, cytopathic phenotype (J. L. Rohn, M. S. Moser, S. R. Gwynn, D. N. Baldwin, and J. Overbaugh, J. Virol. 72:2686–2696, 1998). In the present study, we examined the role of the 4-amino-acid insertion in determining viral replication and tropism of FeLV-81T. The 4-amino-acid insertion was found to be functionally equivalent to a 6-amino-acid insertion at an identical location in the 61C variant. However, viruses expressing a chimeric 61E/81T SU, containing the insertion together with the N terminus of 61E SU, were found to be replication defective and were impaired in the processing of the envelope precursor into the functional SU and transmembrane (TM) proteins. In approximately 10% of cultured feline T cells (3201) transfected with the 61E/81T envelope chimeras and maintained over time, replication-competent tissue culture-adapted variants were isolated. Compensatory mutations in the SU of the tissue culture-adapted viruses were identified at positions 7 and 375, and each was shown to restore envelope protein processing when combined with the C-terminal 81T insertion. Unexpectedly, these viruses displayed different phenotypes in feline T cells: the virus with a change from glutamine to proline at position 7 acquired a T-cell-tropic, cytopathic phenotype, whereas the virus with a change from valine to leucine at position 375 had slower replication kinetics and caused no cytopathic effects. Given the differences in the replication properties of these viruses, it is noteworthy that the insertion as well as the two single-amino-acid changes all occur outside of predicted FeLV receptor-binding domains.

scholarly journals In Vivo Evolution of a Novel, Syncytium-Inducing and Cytopathic Feline Leukemia Virus Variant

1998 ◽  
Vol 72 (4) ◽  
pp. 2686-2696 ◽  
Author(s):  
Jennifer L. Rohn ◽  
Maria S. Moser ◽  
Samuel R. Gwynn ◽  
David N. Baldwin ◽  
Julie Overbaugh
Keyword(s):  
Amino Acid ◽  
T Cell ◽  
Leukemia Virus ◽  
Syncytium Formation ◽  
Viral Envelope ◽  
Feline Leukemia Virus ◽  
Envelope Gene ◽  
Amino Acid Insertion ◽  
Retroviral Infections

ABSTRACT Studies of feline leukemia virus (FeLV) have illustrated the importance of the genotype of the infecting virus in determining disease outcome. In FeLV infections, as in other retroviral infections, it is less clear how virus variants that evolve from the transmitted virus affect pathogenesis. We previously reported an analysis of the genotypic changes that occur in the viral envelope gene (env) in cats infected with a prototype transmissible FeLV clone, 61E (J. Rohn, M. Linenberger, E. Hoover, and J. Overbaugh, J. Virol. 68:2458–2467, 1994). In one cat, each variant (81T) had evolved, in addition to scattered amino acid changes, a four-amino-acid insertion with respect to 61E. This insertion was located at the same site in the extracellular envelope glycoprotein where the immunodeficiency-inducing molecular clone 61C possesses a six-amino-acid insertion critical for its pathogenic phenotype, although the sequences of the insertions were distinct. To determine whether acquisition of the four-amino-acid insertion was associated with a change in the replication or cytopathic properties of the virus, we constructed chimeras encoding 81T env genes in a 61E background. One representative chimeric virus, EET(TE)-109, was highly cytopathic despite the fact that it replicated with delayed kinetics in the feline T-cell line 3201 compared to the parental 61E virus. The phenotype of this virus was also novel compared to other FeLVs, including both the parental virus 61E and the immunodeficiency-inducing variant 61C, because infection of T cells was associated with syncytium formation. Moreover, in single-cycle infection assays, the 81T-109 envelope demonstrated receptor usage properties distinct from those of both 61E and 61C envelope. Thus, these studies demonstrate the evolution of a novel T-cell cytopathic and syncytium-inducing FeLV in the host. The 81T virus will be valuable for dissecting the mechanism of T-cell killing by cytopathic variants in the FeLV model.

scholarly journals Structures suggest an approach for converting weak self-peptide tumor antigens into superagonists for CD8 T cells in cancer

2021 ◽  
Vol 118 (23) ◽  
pp. e2100588118
Author(s):  
Pengcheng Wei ◽  
Kimberly R. Jordan ◽  
Jonathan D. Buhrman ◽  
Jun Lei ◽  
Hexiang Deng ◽  
...  
Keyword(s):  
T Cells ◽  
Amino Acid ◽  
T Cell ◽  
Amino Acid Substitution ◽  
Cd8 T Cells ◽  
Tumor Antigens ◽  
Vaccine Development ◽  
Single Amino Acid ◽  
Cell Repertoire ◽  
Subtle Change

Tumors frequently express unmutated self-tumor–associated antigens (self-TAAs). However, trial results using self-TAAs as vaccine targets against cancer are mixed, often attributed to deletion of T cells with high-affinity receptors (TCRs) for self-TAAs during T cell development. Mutating these weak self-TAAs to produce higher affinity, effective vaccines is challenging, since the mutations may not benefit all members of the broad self-TAA–specific T cell repertoire. We previously identified a common weak murine self-TAA that we converted to a highly effective antitumor vaccine by a single amino acid substitution. In this case the modified and natural self-TAAs still raised very similar sets of CD8 T cells. Our structural studies herein show that the modification of the self-TAA resulted in a subtle change in the major histocompatibility complex I–TAA structure. This amino acid substitution allowed a dramatic conformational change in the peptide during subsequent TCR engagement, creating a large increase in TCR affinity and accounting for the efficacy of the modified self-TAA as a vaccine. These results show that carefully selected, well-characterized modifications to a poorly immunogenic self-TAA can rescue the immune response of the large repertoire of weakly responding natural self-TAA–specific CD8 T cells, driving them to proliferate and differentiate into functional effectors. Subsequently, the unmodified self-TAA on the tumor cells, while unable to drive this response, is nevertheless a sufficient target for the CD8 cytotoxic effectors. Our results suggest a pathway for more efficiently identifying variants of common self-TAAs, which could be useful in vaccine development, complementing other current nonantigen-specific immunotherapies.

scholarly journals T cell receptor interaction with peptide/major histocompatibility complex (MHC) and superantigen/MHC ligands is dominated by antigen.

1993 ◽  
Vol 178 (2) ◽  
pp. 713-722 ◽  
Author(s):  
E W Ehrich ◽  
B Devaux ◽  
E P Rock ◽  
J L Jorgensen ◽  
M M Davis ◽  
...  
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
Amino Acid ◽  
T Cell ◽  
T Cell Activation ◽  
Single Amino Acid ◽  
Receptor Interaction ◽  
Antigenic Peptides ◽  
Major Histocompatibility ◽  
Histocompatibility Complex

While recent evidence strongly suggests that the third complementarity determining regions (CDR3s) of T cell receptors (TCRs) directly contact antigenic peptides bound to major histocompatibility complex (MHC) molecules, the nature of other TCR contact(s) is less clear. Here we probe the extent to which different antigens can affect this interaction by comparing the responses of T cells bearing structurally related TCRs to cytochrome c peptides and staphylococcal enterotoxin A (SEA) presented by 13 mutant antigen-presenting cell (APC) lines. Each APC expresses a class II MHC molecule (I-Ek) with a single substitution of an amino acid residue predicted to be located on the MHC alpha helices and to point "up" towards the TCR. We find that very limited changes (even a single amino acid) in either a CDR3 loop of the TCR or in a contact residue of the antigenic peptide can have a profound effect on relatively distant TCR/MHC interactions. The extent of these effects can be as great as that observed between T cells bearing entirely different TCRs and recognizing different peptides. We also find that superantigen presentation entails a distinct mode of TCR/MHC interaction compared with peptide presentation. These data suggest that TCR/MHC contacts can be made in a variety of ways between the same TCR and MHC, with the final configuration apparently dominated by the antigen. These observations suggest a molecular basis for recent reports in which either peptide analogues or superantigens trigger distinct pathways of T cell activation.

scholarly journals Envelope Determinants for Dual-Receptor Specificity in Feline Leukemia Virus Subgroup A and T Variants

2006 ◽  
Vol 80 (4) ◽  
pp. 1619-1628 ◽  
Author(s):  
Heather H. Cheng ◽  
Maria M. Anderson ◽  
F. Claire Hankenson ◽  
Lily Johnston ◽  
Chitra V. Kotwaliwale ◽  
...  
Keyword(s):  
Amino Acid ◽  
Leukemia Virus ◽  
Amino Acid Position ◽  
Transport Protein ◽  
Feline Leukemia Virus ◽  
Receptor Binding Domain ◽  
Receptor Specificity ◽  
Amino Acid Insertion ◽  
Membrane Spanning ◽  
Adjacent Amino Acid

ABSTRACT Gammaretroviruses, including the subgroups A, B, and C of feline leukemia virus (FeLV), use a multiple-membrane-spanning transport protein as a receptor. In some cases, such as FeLV-T, a nonclassical receptor that includes both a transport protein (Pit1) and a soluble cofactor (FeLIX) is required for entry. To define which regions confer specificity to classical versus nonclassical receptor pathways, we engineered mutations found in either FeLV-A/T or FeLV-T, individually and in combination, into the backbone of the transmissible form of the virus, FeLV-A. The receptor specificities of these viruses were tested by measuring infection and binding to cells expressing the FeLV-A receptor or the FeLV-T receptors. FeLV-A receptor specificity was maintained when changes at amino acid position 6, 7, or 8 of the mature envelope glycoprotein were introduced, although differences in infection efficiency were observed. When these N-terminal mutations were introduced together with a C-terminal 4-amino-acid insertion and an adjacent amino acid change, the resulting viruses acquired FeLV-T receptor specificity. Additionally, a W→L change at amino acid position 378, although not required, enhanced infectivity for some viruses. Thus, we have found that determinants in the N and C termini of the envelope surface unit can direct entry via the nonclassical FeLV-T receptor pathway. The region that has been defined as the receptor binding domain of gammaretroviral envelope proteins determined entry via the FeLV-A receptor independently of the presence of the N- and C-terminal FeLV-T receptor determinants.

Generating Human Immune Responses to Mutations in Bcr-Abl Kinase Selected by Imatinib.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4689-4689
Author(s):  
Javier Pinilla ◽  
Rena May ◽  
Marta Gomez ◽  
Tanya Korontsvit ◽  
Kappel Barry ◽  
...  
Keyword(s):  
T Cells ◽  
Amino Acid ◽  
T Cell ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Ifn Gamma ◽  
Abl Kinase ◽  
Human Immune ◽  
T Cell Lines

Abstract Imatinib mesylate is now standard treatment for chronic myelogenous leukemia. In spite of its high efficacy in controlling the disease, residual bcr-abl cells measured by RT-PCR are still detectable in more than 95% of the patients treated with this drug. In addition, recent reports describe the emergence of resistance to Imatinib mesylate. A major mechanism for the appearance of resistance, are point mutations changing amino acids in the bcr-abl tyrosine kinase that make imatinib ineffective. We hypothesized that some bcr-abl kinase mutations selected by imatinib would generate new immunogenic peptide-epitopes that could be recognized by the human immune system. For this purpose, we selected with predictive computer algorithms potentially immunogenic mutated amino acid sequences and synthetic analogues of mutated bcr-abl kinase sequences to study for immunogenicity and anti-leukemia activity in an in vitro human system. Initially we designed a number of synthetic peptides derived from the most frequent bcr-abl kinase mutations induced by imatinib in which single amino acid substitution was introduced at different MHC-binding positions. We investigated the most common mutations: E255V, E255K, Y253H, Y253F, F311L, T315I, M351T and H396P. Specific single and combined mutations improved the predicted binding of peptides to HLA A0201. Further additional single amino-acid substitutions on mutated peptides generated high predicted binding. Selected sequences were evaluated for eliciting MHC-restricted, peptide-specific CTL responses in an in vitro model using T-cells from different HLA A0201 healthy donors after stimulation with monocyte-derived DC. CTL lines were assessed by either IFN gamma ELISPOT or by a chromium51 release assay. Mutated derived peptides from E255K, E255V, Y253F and T315I were shown to be immunogenic in vitro by the specific release of IFN gamma. Furthermore, single amino-acid substitutions in key residues improved the immunogenicity of these peptides. Finally, T cell lines generated with optimized peptides derived from E255K and T315I (the most common imatinib-induced mutations) were able to kill peptide pulsed targets; more important, these T cell lines cross-reacted with the mutated peptides (a heteroclitic response). In conclusion, Imatinib-selected mutations of peptides from bcr-abl kinase have a better predicted binding than native kinase sequences. Selected peptides from the most common mutations are immunogenic in vitro in a HLA A0201 restricted manner. T cells generated with optimized peptides from these mutations are able to elicit heteroclitic peptide-specific cytotoxicity.

scholarly journals Single Amino Acid Insertion in Loop 4 Confers Amphotropic Murine Leukemia Virus Receptor Function upon Murine Pit1

1998 ◽  
Vol 72 (5) ◽  
pp. 4524-4527 ◽  
Author(s):  
Mikkel D. Lundorf ◽  
Finn S. Pedersen ◽  
Bryan O’Hara ◽  
Lene Pedersen
Keyword(s):  
Amino Acid ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Feline Leukemia Virus ◽  
Single Amino Acid ◽  
Receptor Function ◽  
Amphotropic Murine Leukemia Virus ◽  
Gibbon Ape Leukemia Virus ◽  
Murine Leukemia

ABSTRACT Pit1 is the human receptor for gibbon ape leukemia virus (GALV) and feline leukemia virus subgroup B (FeLV-B), while the related human protein Pit2 is a receptor for amphotropic murine leukemia virus (A-MuLV). The A-MuLV-related isolate 10A1 can utilize both Pit1 and Pit2 as receptors. A stretch of amino acids named region A was identified in Pit1 (residues 550 to 558 in loop 4) as critical for GALV and FeLV-B receptor function. We have here investigated the role of region A in A-MuLV and 10A1 entry. Insertion of a single amino acid in region A of mouse Pit1 resulted in a functional A-MuLV receptor, showing that region A plays a role in A-MuLV infection. Moreover, the downregulation of 10A1 receptor function by changes in region A of human Pit1 indicates that this region is also involved in 10A1 entry. Therefore, region A seems to play a role in infection by all viruses utilizing Pit1 and/or Pit2 as receptors.

scholarly journals A single amino acid mutation in a protein antigen abrogates presentation of certain T cell determinants.

1989 ◽  
Vol 170 (6) ◽  
pp. 2171-2176 ◽  
Author(s):  
A Finnegan ◽  
C F Amburgey
Keyword(s):  
T Cells ◽  
Amino Acid ◽  
T Cell ◽  
Synthetic Peptide ◽  
Cell Epitope ◽  
Staphylococcal Nuclease ◽  
Single Amino Acid ◽  
Antigenic Peptides ◽  
Amino Acid Mutation ◽  
Single Amino Acid Mutation

Nase-specific T cell recognize the 86-100 peptide in association with B10.A APC. Clone N40 recognizes the 86-100 peptide in association with B10.A (Ek alpha Ek beta) and B10.A (5R) (Ek alpha Eb beta) APCs. We demonstrate here that a single amino acid substitution in the staphylococcal nuclease protein alters the structure of the processed peptide such that the T cell epitope recognized by clone N40 was only available for recognition in conjunction with B10.A (5R) but not the B10.A APCs. Other Nase-specific T cells recognize the mutant nuclease, and a synthetic peptide corresponding to the immunodominant region of the mutant protein was stimulatory for all the Nase-specific T cells. These results suggest that the mutation either affects the processing of the protein into antigenic peptides or affects the conformation of the processed fragment differently from that of the peptide.

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