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Background: Evasion of apoptosis contributes to the pathogenesis of solid tumours including non-small cell lung cancer (NSCLC). Malignant cells resist apoptosis through over-expression of inhibitor of apoptosis proteins (IAPs), such as X-linked IAP (XIAP).Methods: A phenylurea-based small molecule inhibitor of XIAP, XIAP antagonist compound (XAC) 1396-11, was investigated preclincally to determine its ability to sensitise to clinically relevant cytotoxics, potentially allowing dose reduction while maintaining therapeutic efficacy.Results: XIAP protein expression was detected in six NSCLC cell lines examined. The cytotoxicity of XAC 1396-11 against cultured NSCLC cell lines in vitro was concentration- and time-dependent in both short-term and clonogenic assays. XAC 1396-11-induced apoptosis was confirmed by PARP cleavage and characteristic nuclear morphology. XAC 1396-11 synergised with vinorelbine+/-cisplatin in H460 and A549 NSCLC cells. The mechanism of synergy was enhanced apoptosis, shown by increased cleavage of caspase-3 and PARP and by the reversal of synergy by a pan-caspase inhibitor. Synergy between XAC 1396-11 and vinorelbine was augmented by optimising drug scheduling with superior effects when XAC 1396-11 was administered before vinorelbine.Conclusion: These preclinical data suggest that XIAP inhibition in combination with vinorelbine holds potential as a therapeutic strategy in NSCLC. [ABSTRACT FROM AUTHOR]

To define the amino acids involved in IgG subclass reactivity to two overlapping HIV-1 gp41 (E34/32; amino acid positions 582-613) peptides, sera from 18 HIV-infected individuals were studied. Peptides mimicking E34 but with single amino acid deletions or glycine substitutions were used to define the amino add residues necessary for antibody binding. Two dominating immunogenic epitopes, containing highly hydrophilic amino acids, were found on the original peptide. Further analysis was undertaken with two corresponding omission sets of dodecapeptides representing halves of the complete E34 plus a terminal cystein peptide. The subclass reactivities usually differed between the patients with regard to the epitopes with which the different IgG subclasses reacted and also to the importance of different amino acids in antibody binding. The 600 glycine and the 601 lysine were involved in the binding of all IgG1,2 and 4 and most IgG3. The development of E34/32-reactive IgM and IgG subclasses showed different patterns in four patients with primary HIV infections, contradicting the existence of a general pattern for the development of IgG subclasses to this peptide. The findings suggest that different progenitor clones are selected for synthesis of the different subclasses. [ABSTRACT FROM AUTHOR]

Helper T cell determinants should be an Important component of an anti-human Immunodeflciency virus (HIV) vaccine aimed at either antibody or cytotoxic T cell Immunity. However, model protein studies have raised concern about the usefulness of any single determinant, because a given determinant is likely to be seen by only a small subset of major histocompatiblllty complex (MHC) types within the population. Here, we use 44 peptldes, Including ones predicted and not predicted on the basis of amphipathicity to be potential T cell sites, to locate T cell antlgenic determinants recognized by mice of four MHC haplotypes immunized with the whole gpl6O envelope protein. Although the preselectlon of peptides necessitates caution in a statistical analysis, α-amphipathic peptides predominated among sites eliciting the strongest response. Although we have not tested the entire sequence, we have identified six multideterminant regions, in which overlapping peptides are recognized by mice of either three or all four MHC types. Four of the six regions have sequences relatively conserved among HIV.1 isolates. The existence of such multideterminant regions recognized by multiple MHC haplotypes suggests the possibilIty that use of peptides longer than a minimal determinant and containing several overlapping determinants may be a possible approach to circumvent the serious problem of MHC restriction in peptide vaccines aimed at eliciting T cell immunity. [ABSTRACT FROM PUBLISHER]

A group of eight synthetic peptides, corresponding in sequence to selected regions of HLA-DQ histocompatibility antigens, was used for rabbit immunization to examine their antigenicity and for localizing exposed regions in the native glycoproteins. Those antibodies were then tested in their ability to recognize the HLA-DQ alloantigens. Seven peptides elicited rabbit antibodies, four of which reacted with human glycoproteins prepared from chronic lymphocytic leukaemia cells. The results indicate that sequence stretches 63 to 79 and probably 82 to 93 of the beta chain correspond to exposed regions in DQw1, DQw2 and DQw3 molecules. However, the specificity of those antipeptide antibodies was low, due to extensive crossreactions with amino acid sequencies of high homology occurring in DQ alloantigens. [ABSTRACT FROM AUTHOR]

Uncoupled synthetic peptide representing the sequence of amino acids 141–160 of foot-and-mouth disease virus (FMDV) protein VP1 induced a virus-neutralizing antibody response in guinea-pigs. This response required incomplete Freund's adjuvant (IFA) for the primary inoculation and was dependent on the presence of an added cysteine residue with an unblocked sulphydryl group at the carboxy-terminus. Secondary immunization could be carried out in the absence of adjuvant. A study of the relative activities of nested sets of uncoupled peptides from 150–160 to 135–160 and 141–160 to 141–155 indicated that amino acids 146–156 were critical for the induction of virus-neutralizing antibodies and that extension to 137–160 further improved this response. Results of in vitro proliferation studies demonstrated that the carboxy-terminal residues on this peptide may form a T- cell epitope. The significance of these observations in the broader context of synthetic peptide vaccines is discussed. [ABSTRACT FROM AUTHOR]

A rabbit was immunized with B lymphoblastoid cells, and subsets of the antibodies produced were isolated on affinity columns made from synthetic peptides corresponding to known amino acid sequences from the human class II antigens DQ and DP, Those peptides for which specific antibodies were isolated could be assumed to contribute to the antigenic properties of the intact antigen. The antibody subsets were tested for binding to synthetic peptides, to glycoprotein fractions isolated from cells with different DR and DQ specificities, and to the cells used for immunization of the rabbit. The isolation of those antibodies directed against well-defined amino acid stretches of the histocompatibility antigens is proof of the role of those regions in determining the antigenic properties of these molecules. [ABSTRACT FROM AUTHOR]