HLA B37 determines an influenza A virus nucleoprotein epitope recognized by cytotoxic T lymphocytes

Understanding the Role of HLA Class I Molecules in the Immune Response to Influenza Infection and Rational Design of a Peptide-Based Vaccine

Influenza A virus is a respiratory pathogen that is responsible for regular epidemics and occasional pandemics that result in substantial damage to life and the economy. The yearly reformulation of trivalent or quadrivalent flu vaccines encompassing surface glycoproteins derived from the current circulating strains of the virus does not provide sufficient cross-protection against mismatched strains. Unlike the current vaccines that elicit a predominant humoral response, vaccines that induce CD8+ T cells have demonstrated a capacity to provide cross-protection against different influenza strains, including novel influenza viruses. Immunopeptidomics, the mass spectrometric identification of human-leukocyte-antigen (HLA)-bound peptides isolated from infected cells, has recently provided key insights into viral peptides that can serve as potential T cell epitopes. The critical elements required for a strong and long-living CD8+ T cell response are related to both HLA restriction and the immunogenicity of the viral peptide. This review examines the importance of HLA and the viral immunopeptidome for the design of a universal influenza T-cell-based vaccine.

Identification and Characterization of Antigen-Specific CD8+ T Cells Using Surface-Trapped TNF-α and Single-Cell Sequencing

CD8+ T cells are key mediators of antiviral and antitumor immunity. The isolation and study of Ag-specific CD8+ T cells, as well as mapping of their MHC restriction, has practical importance to the study of disease and the development of therapeutics. Unfortunately, most experimental approaches are cumbersome, owing to the highly variable and donor-specific nature of MHC-bound peptide/TCR interactions. Here we present a novel system for rapid identification and characterization of Ag-specific CD8+ T cells, particularly well suited for samples with limited primary cells. Cells are stimulated ex vivo with Ag of interest, followed by live cell sorting based on surface-trapped TNF-α. We take advantage of major advances in single-cell sequencing to generate full-length sequence data from the paired TCR α- and β-chains from these Ag-specific cells. The paired TCR chains are cloned into retroviral vectors and used to transduce donor CD8+ T cells. These TCR transductants provide a virtually unlimited experimental reagent, which can be used for further characterization, such as minimal epitope mapping or identification of MHC restriction, without depleting primary cells. We validated this system using CMV-specific CD8+ T cells from rhesus macaques, characterizing an immunodominant Mamu-A1*002:01-restricted epitope. We further demonstrated the utility of this system by mapping a novel HLA-A*68:02-restricted HIV Gag epitope from an HIV-infected donor. Collectively, these data validate a new strategy to rapidly identify novel Ags and characterize Ag-specific CD8+ T cells, with applications ranging from the study of infectious disease to immunotherapeutics and precision medicine.

Legacy of the influenza pandemic 1918: The host T cell response

The influenza virus was instrumental in unravelling critical aspects of the antiviral T lymphocyte mediated immune response. A major finding was the demonstration that CD8 T lymphocytes recognize short viral peptides presented by class I molecules of the major histocompatibility complex. Studies of influenza specific T cells have also led to an understanding of their important role in recovery from influenza virus infection in humans.

Nucleoprotein of influenza A virus is a major target of immunodominant CD8+ T-cell responses

Influenza A virus causes annual epidemics and sporadic pandemics, resulting in significant morbidity and mortality worldwide. Vaccines are currently available; however, they induce a non-strain-cross protective humoral immune response directed against the rapidly mutating surface glycoproteins, and thus need to be updated annually. As T cells are directed against more conserved internal influenza proteins, a T-cell-based vaccine has the potential to induce long-lasting and cross-strain protective CD8(+) T-cell immunity, and in that way minimize the severity of influenza infection. However, to rationally design such vaccines, we need to identify immunogenic T-cell regions within the most antigenic viral proteins. In this study, we have used a systematic approach to identify immunodominant peptides in HLA-A2-negative donors. A broad range of CD8(+) T-cell responses were observed and 6/7 donors had an immunodominant response against the relatively conserved internal nucleoprotein (NP). Dissecting the minimal epitope regions within the immunogenic NP led to the identification of six novel immunodominant epitopes, which include a 12-mer and an 8-mer peptides. The majority of immunodominant epitopes was clustered within the carboxyl terminal 2/3 of the NP protein and were highly conserved. We also subjected NP to three common computer algorithms for epitope prediction and found that most of the novel epitopes would not have been predicted. Our study emphasizes the importance of using a systematic approach to identify immunodominant CD8(+) T-cell responses and suggests that the epitope-rich regions within NP present a promising target for the T-cell-mediated multi-strain influenza vaccine.

Vertical T cell immunodominance and epitope entropy determine HIV-1 escape

HIV-1 accumulates mutations in and around reactive epitopes to escape recognition and killing by CD8+ T cells. Measurements of HIV-1 time to escape should therefore provide information on which parameters are most important for T cell-mediated in vivo control of HIV-1. Primary HIV-1-specific T cell responses were fully mapped in 17 individuals, and the time to virus escape, which ranged from days to years, was measured for each epitope. While higher magnitude of an individual T cell response was associated with more rapid escape, the most significant T cell measure was its relative immunodominance measured in acute infection. This identified subject-level or "vertical" immunodominance as the primary determinant of in vivo CD8+ T cell pressure in HIV-1 infection. Conversely, escape was slowed significantly by lower population variability, or entropy, of the epitope targeted. Immunodominance and epitope entropy combined to explain half of all the variability in time to escape. These data explain how CD8+ T cells can exert significant and sustained HIV-1 pressure even when escape is very slow and that within an individual, the impacts of other T cell factors on HIV-1 escape should be considered in the context of immunodominance.

Systematic identification of immunodominant CD8+ T-cell responses to influenza A virus in HLA-A2 individuals

Immunodominant T-cell responses are important for virus clearance. However, the identification of immunodominant T-cell peptide + HLA glycoprotein epitopes has been hindered by the extent of HLA polymorphism and the limitations of predictive algorithms. A simple, systematic approach has been used here to screen for immunodominant CD8(+) T-cell specificities. The analysis targeted healthy HLA-A2(+) donors to allow comparison with responses to the well-studied influenza matrix protein 1 epitope. Although influenza matrix protein 1 was consistently detected in all individual samples in our study, the response to this epitope was only immunodominant in three of eight, whereas for the other five, prominent CD8(+) T-cell responses tended to focus on various peptides from the influenza nucleoprotein that were not presented by HLA-A2. Importantly, with the four immunodominant T-cell epitopes identified here, only one would have been detected by the current prediction programs. The other three peptides would have been either considered too long or classified as not containing typical HLA binding motifs. Our data stress the importance of systematic analysis for discovering HLA-dependent, immunodominant CD8(+) T-cell epitopes derived from viruses and tumors. Focusing on HLA-A2 and predictive algorithms may be too limiting as we seek to develop targeted immunotherapy and vaccine strategies that depend on T cell-mediated immunity.

Swine influenza vaccines: current status and future perspectives

Swine influenza is an important contagious disease in pigs caused by influenza A viruses. Although only three subtypes of influenza A viruses, H1N1, H1N2 and H3N2, predominantly infect pigs worldwide, it is still a big challenge for vaccine manufacturers to produce efficacious vaccines for the prevention and control of swine influenza. Swine influenza viruses not only cause significant economic losses for the swine industry, but are also important zoonotic pathogens. Vaccination is still one of the most important and effective strategies to prevent and control influenza for both the animal and human population. In this review, we will discuss the current status of swine influenza worldwide as well as current and future options to control this economically important swine disease.

Avian influenza viral nucleocapsid and hemagglutinin proteins induce chicken CD8+ memory T lymphocytes

The avian influenza viruses (AIVs) can be highly contagious to poultry and a zoonotic threat to humans. Since the memory CD8(+) T lymphocyte responses in chickens to AIV proteins have not been defined, these responses to H5N9 AIV hemagglutinin (HA) and nucleocapsid (NP) proteins were evaluated by ex vivo stimulation with virus infected non-professional antigen presenting cells. Secretion of IFNgamma by activated T lymphocytes was evaluated through macrophage induction of nitric oxide. AIV specific, MHC-I restricted memory CD8(+) T lymphocyte responses to NP and HA were observed 3 to 9 weeks post-inoculation (p.i.). The responses specific to NP were greater than those to HA with maximum responses being observed at 5 weeks p.i. followed by a decline to weakly detectable levels by 9 weeks p.i. The cross-reaction of T lymphocytes to a heterologous H7N2 AIV strain demonstrated their ability to respond to a broader range of AIV.

Cross-reactive, cell-mediated immunity and protection of chickens from lethal H5N1 influenza virus infection in Hong Kong poultry markets

In 1997, avian H5N1 influenza virus transmitted from chickens to humans resulted in 18 confirmed infections. Despite harboring lethal H5N1 influenza viruses, most chickens in the Hong Kong poultry markets showed no disease signs. At this time, H9N2 influenza viruses were cocirculating in the markets. We investigated the role of H9N2 influenza viruses in protecting chickens from lethal H5N1 influenza virus infections. Sera from chickens infected with an H9N2 influenza virus did not cross-react with an H5N1 influenza virus in neutralization or hemagglutination inhibition assays. Most chickens primed with an H9N2 influenza virus 3 to 70 days earlier survived the lethal challenge of an H5N1 influenza virus, but infected birds shed H5N1 influenza virus in their feces. Adoptive transfer of T lymphocytes or CD8(+) T cells from inbred chickens (B(2)/B(2)) infected with an H9N2 influenza virus to naive inbred chickens (B(2)/B(2)) protected them from lethal H5N1 influenza virus. In vitro cytotoxicity assays showed that T lymphocytes or CD8(+) T cells from chickens infected with an H9N2 influenza virus recognized target cells infected with either an H5N1 or H9N2 influenza virus in a dose-dependent manner. Our findings indicate that cross-reactive cellular immunity induced by H9N2 influenza viruses protected chickens from lethal infection with H5N1 influenza viruses in the Hong Kong markets in 1997 but permitted virus shedding in the feces. Our findings are the first to suggest that cross-reactive cellular immunity can change the outcome of avian influenza virus infection in birds in live markets and create a situation for the perpetuation of H5N1 influenza viruses.

Antigenic drift in the influenza A virus (H3N2) nucleoprotein and escape from recognition by cytotoxic T lymphocytes

Viruses exploit different strategies to escape immune surveillance, including the introduction of mutations in cytotoxic T-lymphocyte (CTL) epitopes. The sequence of these epitopes is critical for their binding to major histocompatibility complex (MHC) class I molecules and recognition by specific CTLs, both of which interactions may be lost by mutation. Sequence analysis of the nucleoprotein gene of influenza A viruses (H3N2) isolated in The Netherlands from 1989 to 1999 revealed two independent amino acid mutations at the anchor residue of the HLA-B27-specific CTL epitope SRYWAIRTR (383 to 391). A R384K mutation was found in influenza A viruses isolated during the influenza season 1989-1990 but not in subsequent seasons. In the influenza season 1993-1994, a novel mutation in the same CTL epitope at the same position was introduced. This R384G mutation proved to be conserved in all influenza A viruses isolated from 1993 onwards. Both mutations R384K and R384G abrogated MHC class I presentation and allowed escape from recognition by specific CTLs.

Intranasal administration of peptide vaccine protects human/mouse radiation chimera from influenza infection

Influenza virus is characterized by frequent and unpredictable changes of the surface glycoproteins which enable the virus to escape the immune system. Approved vaccines which consist of the whole virus or the surface glycoproteins fail to induce broad specificity protection. We have previously reported that a peptide-based experimental recombinant vaccine which includes conserved epitopes of B and T lymphocytes was efficient in mice, leading to cross-strain, long-term protection. In the present study, this approach was adapted for the design of a human vaccine, based on epitopes recognized by the prevalent HLAs. These epitopes were expressed in Salmonella flagellin and tested for their efficacy in human/mouse radiation chimera in which human peripheral blood mononuclear cells (PBMC) are functionally engrafted. The vaccinated mice demonstrated clearance of the virus after challenge and resistance to lethal infection. The production of virus-specific human antibodies was also higher in this group. Control groups of either non-vaccinated, or vaccinated mice which had not been engrafted with the human PBMC, did not exhibit the protective immune response. FACS analysis showed that most human cells in the transplanted mice are CD8(+) and CD4(+). Hence, it may be concluded: (i) that the protection involves cellular mechanisms, but is most probably accomplished without direct lysis of influenza-infected pulmonary cells by cytotoxic T lymphocytes, but rather via a cytokine-mediated mechanism, (ii) that the human/mouse radiation chimera model may be of some value in the investigation of new vaccines, as an additional tool prior to clinical trials, and (iii) that the synthetic recombinant vaccine can induce a response in the human immune system and confers protection against influenza infection. Further investigation is needed to establish the efficacy of such a peptide vaccine in human subjects.

Human cytotoxic T-lymphocyte repertoire to influenza A viruses

The murine CD8(+) cytotoxic-T-lymphocyte (CTL) repertoire appears to be quite limited in response to influenza A viruses. The CTL responses to influenza A virus in humans were examined to determine if the CTL repertoire is also very limited. Bulk cultures revealed that a number of virus proteins were recognized in CTL assays. CTL lines were isolated from three donors for detailed study and found to be specific for epitopes on numerous influenza A viral proteins. Eight distinct CD8(+) CTL lines were isolated from donor 1. The proteins recognized by these cell lines included the nucleoprotein (NP), matrix protein (M1), nonstructural protein 1 (NS1), polymerases (PB1 and PB2), and hemagglutinin (HA). Two CD4(+) cell lines, one specific for neuraminidase (NA) and the other specific for M1, were also characterized. These CTL results were confirmed by precursor frequency analysis of peptide-specific gamma interferon-producing cells detected by ELISPOT. The epitopes recognized by 6 of these 10 cell lines have not been previously described; 8 of the 10 cell lines were cross-reactive to subtype H1N1, H2N2, and H3N2 viruses, 1 cell line was cross-reactive to subtypes H1N1 and H2N2, and 1 cell line was subtype H1N1 specific. A broad CTL repertoire was detected in the two other donors, and cell lines specific for the NP, NA, HA, M1, NS1, and M2 viral proteins were isolated. These findings indicate that the human memory CTL response to influenza A virus is broadly directed to epitopes on a wide variety of proteins, unlike the limited response observed following infection of mice.

The carboxyl-terminal 120-residue polypeptide of infectious bronchitis virus nucleocapsid induces cytotoxic T lymphocytes and protects chickens from acute infection

Specific cytotoxic T-lymphocyte (CTL) responses to nucleocapsid of infectious bronchitis virus (IBV) were identified by using target cells infected with a Semliki Forest virus (SFV) vector. Effector cells for CTL assays were collected from chickens infected with the Gray strain of IBV or inoculated with a DNA plasmid encoding nucleocapsid proteins. IBV-specific CTL epitopes were mapped within the carboxyl-terminal 120 amino acids of the nucleocapsid protein. CTL lysis of target cells infected with SFV encoding nucleocapsid was major histocompatibility complex restricted and mediated by CD8+ T cells. In addition, splenic T cells collected from chickens inoculated in the breast muscle with a DNA plasmid encoding this CTL epitope(s) recognized target cells infected with wild-type virus or an SFV vector encoding nucleocapsid proteins. CTL activity of splenic T cells collected from chicks immunized with a DNA plasmid encoding CTL epitopes was cross-reactive, in that lysis of target cells infected with serologically distinct strains of IBV was dose responsive in a manner similar to that for lysis of target cells infected with the homologous strain of IBV. Furthermore, chickens immunized with a DNA plasmid encoding a CTL epitope(s) were protected from acute viral infection.

Escape of human immunodeficiency virus from immune control

Cytotoxic T lymphocytes (CTL) play a crucial role in the attempt to control infection with human immunodeficiency virus (HIV). Variation in epitopes recognized by CTL is common and frequently offers potential escape routes for mutant virus. Proof of escape, however, requires demonstration of increased frequency of virus particles or provirus that carry the escape sequence. There are now several recorded examples of virus variants that escape from CTL and are then selected. Most dramatic are those in which the CTL response has been dominated by CTL recognizing a single epitope that has suddenly changed, resulting in escape to fixation. This has been seen both early and late in the infection, leaving no doubt that escape occurs. Such escape is likely to be favored when the antiviral CTL response is oligoclonal and focused on a small number of immunodominant epitopes. The heterogeneous CTL response seen in many HIV-infected patients may result from successive waves of virus escape followed by new CTL responses specific for subdominant epitopes. Mutant virus can escape by several different routes, including failure of the mutated peptide to bind to the presenting HLA molecule and altered interactions with T cell receptors (TCR), including antagonism.

Requirement of CD4+ T cells and antigen-presenting cells for primary in vitro generation of CD8+ cytotoxic T cells against Ld-binding self-peptide p2Ca

We investigated the cellular requirement for primary in vitro generation of cytotoxic T-lymphocytes (CTL) in BALB/c spleen cells against Ld-binding self-peptide p2Ca. Depletion of CD4+ T-cells in vitro by pretreatment with anti-CD4 monoclonal antibody (mAb) and complement or in vivo by administration of anti-CD4 mAb abrogated generation of CTL. Depletion of adherent cells by passing spleen cells through a nylon wool (NW) column also abrogated generation of CTL. Addition of peritoneal exudate cells (PEC) to spleen cells passed through the NW column restored CTL generation. These findings indicate that both CD4+ T-cells and antigen-presenting cells (APC) were necessary for CTL generation. Treatment of PEC with paraformaldehyde (PFA), but not mitomycin-C (MMC) abrogated their ability to restore CTL generation when mixed with spleen cells from the NW column, suggesting that an endocytic pathway could be involved in presentation of p2Ca on APC.

Structure, chromosomal localization, and expression of 12 genes of the MAGE family

We reported previously that human gene MAGE-1 directs the expression of a tumor antigen recognized on a melanoma by autologous cytolytic T lymphocytes. Probing cosmid libraries with a MAGE-1 sequence, we identified 11 closely related genes. The analysis of hamster-human somatic cell hybrids indicated that the 12 MAGE genes are located in the q terminal region of chromosome X. Like MAGE-1, the 11 additional MAGE genes have their entire coding sequence located in the last exon, which shows 64%-85% identity with that of MAGE-1. The coding sequences of the MAGE genes predict the same main structural features for all MAGE proteins. In contrast, the promoters and first exons of the 12 MAGE genes show considerable variability, suggesting that the existence of this gene family enables the same function to be expressed under different transcriptional controls. The expression of each MAGE gene was evaluated by reverse transcription and polymerase chain reaction amplification. Six genes of the MAGE family including MAGE-1 were found to be expressed at a high level in a number of tumors of various histological types. None was expressed in a large panel of healthy tissues, with the exception of testis and placenta.

Influenza virus-infected dendritic cells stimulate strong proliferative and cytolytic responses from human CD8+ T cells

Antigen-specific, CD8+, cytolytic T lymphocytes (CTLs) could potentially provide resistance to several infectious and malignant diseases. However, the cellular requirements for the generation of specific CTLs in human lymphocyte cultures are not well defined, and repetitive stimulation with antigen is often required. We find that strong CD8+ CTL responses to influenza virus can be generated from freshly isolated blood T cells, as long as dendritic cells are used as antigen presenting cells (APCs). Small numbers of dendritic cells (APC:T cell ratio of 1:50-1:100) induce these CTL responses from most donors in 7 d of culture, but monocytes are weak or inactive. Whereas both dendritic cells and monocytes are infected with influenza virus, the former serve as effective APCs for the induction of CD8+ T cells while the latter act as targets for the CTLs that are induced. The strong CD8+ response to influenza virus-infected dendritic cells is accompanied by extensive proliferation of the CD8+ T cells, but the response can develop in the apparent absence of CD4+ helpers or exogenous lymphokines. CD4+ influenza virus-specific CTLs can also be induced by dendritic cells, but the cultures initially must be depleted of CD8+ cells. These findings should make it possible to use dendritic cells to generate human, antigen-specific, CD8+ CTLs to other targets. The results illustrate the principle that efficient T cell-mediated responses develop in two stages: an afferent limb in which dendritic cells are specialized APCs and an efferent limb in which the primed T cells carry out an immune response to many types of presenting cells.

Interaction of in vitro- and in vivo-generated cytotoxic T cells with SV40 T antigen: analysis with synthetic peptides

Virus-specific cytotoxic T cells recognize antigens in the form of peptides (8 or 9 amino acids long) bound to MHC class-I molecules. Exposure of unprimed murine splenocytes to synthetic peptides of viral antigens elicits primary CTL in vitro. The fine specificity of such CTL as well as the correlation between binding affinity of peptides to class-I molecules and CTL induction was analysed using synthetic peptides corresponding to overlapping and distinct amino-acid residues in SV40 T antigen (Tag) Db-restricted T-cell epitopes I, II-III, and V. The peptides induced cross-reactive CD8+ primary CTL in splenocytes of naive C57 BL/6 mice. This reactivity was seen regardless of the peptides allelic anchor motifs or their abilities to stabilize empty class-I molecules. However, none of the primary CTL and CTL lines lysed Tag-expressing cells. In contrast, CTL generated in vivo by immunizing mice with Tag-expressing cells recognized endogenously processed Tag as well as synthetic peptides. The peptides recognized by these CTL depended on the intracellular concentration of Tag antigen in the immunizing cells. The reactivity of these CTL was peptide specific as shown by a functional peptide competition assay. Moreover, three peptides bound to and were recognized in the context of both Kb and Db molecules. These results have revealed a flexible disposition of MHC class-I molecules with regard to peptide binding and also reflected lack of correlation between binding affinity to class-I molecules and the capacity of peptides to induce primary CTL or to serve as potential targets. The significance of these findings in relation to identifying major T-cell epitopes using allele specific peptide motif and in vitro maintained CTL clones is discussed.

Human gene MAGE-3 codes for an antigen recognized on a melanoma by autologous cytolytic T lymphocytes

Human melanoma cell line MZ2-MEL expresses several antigens recognized by autologous cytolytic T lymphocyte (CTL) clones. We reported previously the identification of a gene, named MAGE-1, that codes for one of these antigens named MZ2-E. We show here that antigen MZ2-D, which is present on the same tumor, is encoded by another member of the MAGE gene family named MAGE-3. Like MAGE-1, MAGE-3 is composed of three exons and the large open reading frame is entirely located in the third exon. Its sequence shows 73% identity with MAGE-1. Like MZ2-E, antigen MZ2-D is presented by HLA-A1. The antigenic peptide of MZ2-D is a nonapeptide that is encoded by the sequence of MAGE-3 that is homologous to the MAGE-1 sequence coding for the MZ2-E peptide. Competition experiments using single Ala-substituted peptides indicated that amino acid residues Asp in position 3 and Tyr in position 9 were essential for binding of the MAGE-1 peptide to HLA-A1. Gene MAGE-3 is expressed in many tumors of several types, such as melanoma, head and neck squamous cell carcinoma, lung carcinoma and breast carcinoma, but not in normal tissues except for testes. It is expressed in a larger proportion of melanoma samples than MAGE-1. MAGE-3 encoded antigens may therefore have a wide applicability for specific immunotherapy of melanoma patients.

More efficient peptide binding to MHC class II molecules during cathepsin B digestion of Ii than after Ii release

The binding of a T cell-presented peptide to MHC class II alpha,beta chains occurs as a concurrent process with the release of the associated invariant chain (Ii) by cathepsin B. Ii was digested by cathepsin B from solubilized, MHC class II alpha,beta,Ii complexes in the presence of N-hydroxysuccinimidyl-4-azidobenzoate-conjugated, 125I-labeled, influenza virus matrix (18-29) peptide. The peptide was crosslinked where it became bound. This HLA-DR1-restricted peptide bound about three times more efficiently to class II alpha,beta chains of DR1-positive B cells when present during cathepsin B digestion of Ii than when added afterward, also at pH 5.0. Binding was competed by similarly DR-restricted peptides. Cathepsin D cleaved Ii but did not enhance peptide binding. However, a trace level of cathepsin D, added to the assay for peptide binding in the presence of cathepsin B, further enhanced peptide binding about three times. These experiments support an hypothesis for the staged release of Ii fragments by cathepsin D and cathepsin B, catalyzing at one point the insertion of a peptide into the antigen binding site formed by class II alpha and beta chains.

Rubella virus-specific cytotoxic T-lymphocyte responses: identification of the capsid as a target of major histocompatibility complex class I-restricted lysis and definition of two epitopes

The role of major histocompatibility complex (MHC) class I-restricted CD8+ cytotoxic T lymphocytes in immunity to rubella virus (RV) infection is unknown. Lymphocytes of RV-immune individuals were prestimulated on an RV-infected MHC class I-matched (or partially matched) fibroblast monolayer which generated CD8+ lymphoblasts capable of lysing RV-infected fibroblast targets in a class I-restricted manner. Using an infectious Sindbis virus (SV) vector which expressed the RV capsid protein (SV/RubC), lymphocytes from 17 of 22 RV-immune individuals prestimulated on RV-infected fibroblast monolayers lysed SV/RubC-infected fibroblast targets. A sequence within the amino terminus of the capsid protein that was previously shown to contain immunodominant class II-restricted T-cell epitopes was evaluated for class I-restricted epitopes. Fibroblast targets pulsed with synthetic peptides representing subsequences within C1 to C29 (subscripts indicate amino acid positions) were lysed effectively when the targets and effectors matched at multiple class I alleles. By limiting the number of matching class I alleles, an A2-restricted epitope was identified within C9 to C22 and an epitope that could be presented by multiple class I molecules was identified within C11 to C29. A sequence such as C1 to C29 which contains both MHC class I- and MHC class II-restricted epitopes recognized by a heterologous human population may serve as a component of an effective synthetic vaccine.

A sequence pattern for peptides presented to cytotoxic T lymphocytes by HLA B8 revealed by analysis of epitopes and eluted peptides

HLA B8-restricted cytotoxic T lymphocytes (CTL) specific for influenza A virus were generated and shown to recognize the nucleoprotein (NP). The dominant epitope was mapped using recombinant vaccinia viruses that expressed fragments of the NP and then synthetic peptides based on the NP amino acid sequence. The peptide 380-393 was first identified and further refined; it was shown that the glutamic acid at position 380 was essential for recognition by CTL and that the nonamer 380-388 was the optimum peptide. Six HLA B8-positive influenza immune donors that we have tested respond to this peptide as part of their influenza-specific CTL response. The amino acid sequence of the peptide epitope was compared to six other known virus peptides known to be restricted by HLA B8 and a sequence homology was identified, which predicted nonamer and octamer epitope sequences. Probable anchor residues were identified at peptide residues 3 (lysine/arginine), 5 (lysine/arginine) and 9 (leucine/isoleucine). Support for this pattern came from sequencing peptides eluted from purified HLA B8 molecules, where lysines were predominant at positions 3 and 5. One of the predicted epitope peptides was made and shown to be recognized by specific CTL. These and the two others were shown to compete with NP 380-388 for binding to HLA B8. A model was made of the HLA B8 molecule and negatively charged pockets predicted, which could accommodate the positively charged side chains of the peptide anchor residues.

Unfolded HLA class I alpha chains and their use in an assay of HLA class-I-peptide binding

Unfolded HLA class I alpha chains were isolated from B-cell lysates by alkaline denaturation and subsequent gel filtration and used for the detection of HLA class-I-peptide binding. Binding to specific peptides in the presence of excess beta 2-microglobulin induced the unfolded alpha chains to refold and acquire a conformation that is specific to folded alpha chains. This conformational change was measured by a specific RIA that involves inhibition of the binding of 125I-labeled HLA-A2 alpha/beta dimers and rabbit anti-HLA-B7 serum absorbed with beta 2-microglobulin. This assay procedure does not require labeling of either test peptides or test class I proteins and does not seem to have specificity degeneracy. It is applicable to the detection of peptide binding by all HLA class I allelic proteins. Evaluation of the assay conditions and HLA allelic specificity of the peptide binding defined by the use of synthetic peptides are described here, including the technical details, specificity, and reproducibility.

Adsorption and helical coiling of amphipathic peptides on lipid vesicles leads to negligible protection from cathepsin B or cathepsin D

The processing of antigenic peptides for presentation by MHC molecules to T cells, may depend upon the function of a second, consensus sequence in or near the T cell-presented epitope. One such processing-regulating sequence appears to be composed of amino acids Leu, Ile, Val, Phe, and Met recurring in a fashion to form a longitudinal, hydrophobic strip when the excised peptide is coiled as an alpha-helix. Such a hydrophobic strip-of-helix may: (a) scavenge peptides from lumens onto lipid membranes of digestion vesicles, (b) stabilize peptides there as protease-resistant helices, (c) specify recognition by the antigenic peptide-binding sites of chaperonin proteins, transmembranal transporters, or MHC molecules. By circular dichroism and electron paramagnetic resonance, we demonstrated that peptides with recurrent hydrophobic residues potentially forming longitudinal strips adsorbed to, and partially coiled as helices on, di-O-hexadecyl, D-L-alpha-phosphatidylcholine (DHPC) vesicles. Cathepsin B or cathepsin D cleavages of three such peptides were identified. With either enzyme, it made no significant difference whether a peptide substrate was in solution or bound to vesicles in terms of efficiency and specificity of peptide bond cleavages. We conclude that protease resistance, per se, of membrane-adsorbed, helically coiled peptides is not a major factor in the selection for T cell presentation of epitopes in peptides which have a motif with a longitudinal hydrophobic strip.

Different rates of HLA class I molecule assembly which are determined by amino acid sequence in the alpha 2 domain

Assembly of HLA class I molecules was studied using pulse-chase labeling of B-lymphoblastoid cell lines with 35S-methionine, immunoprecipitation with antibodies detecting free or beta 2-microglobulin-associated heavy chain and isoelectric focusing. Marked differences between the products of different class I alleles were noted. HLA-B51 assembled very inefficiently, with considerable free heavy chain still detected in an unsialated form after a four hour chase. The closely related molecule HLA-B35 was in contrast rapidly assembled, all newly synthesized heavy chain being detected in a beta 2m-associated sialated form within 30 minutes. Analysis of naturally occurring variants related to HLA-B35 and HLA-B51 localized the region determining assembly efficiency to the alpha 2 domain, in which these molecules differ at eight amino acid residues. The effect was not due to a linked dominant gene, as both patterns of assembly were observed in a single cell line.

Epstein-Barr virus-associated primary B-cell lymphoproliferative disorder of the cerebellum in an immune competent man

BACKGROUND

The role of the Epstein-Barr virus (EBV) in lymphoproliferative lesions has been widely accepted. Most of these lesions occur in patients who have deficiencies in their immune status. Lymphomatoid granulomatosis (LG) is a lymphoproliferative disorder originally characterized as an angiocentric, necrotizing, pleomorphic infiltrate of mononuclear cells. The etiology of LG is unknown. It was originally hypothesized that LG may represent an unusual lymphoid response to an infective organism, possibly EBV.

METHODS

Tissues from a previously healthy 60-year-old, healthy white man with primary cerebellar lymphomatoid granulomatosis were examined for the presence of EBV by nucleic acid hybridization.

RESULTS

The original LG lesion was a polyclonal B-cell proliferation that contained detectable amounts of EBV. Peripheral blood leukocytes were negative for EBV by the same assay. After an 18-month remission, a tumor reappeared near the site of the primary lesion, which had the histologic appearance of a lymphoma. The cells showed restricted clonality and contained a similar amount of EBV-related DNA as the original lesion. Peripheral blood leukocytes at the time of recurrence were negative for EBV. The patient died approximately 2 months after the recurrent tumor was detected.

CONCLUSIONS

This case demonstrated the development of a primary cerebellar B-cell lymphoproliferative disorder, histologically identical to lymphomatoid granulomatosis, that transformed into a lymphoma. The original tumor and the subsequent lymphoma contained, on average, several copies of EBV-related DNA per cell. Despite an extensive survey of the patient, no immune deficit was detected. Interpretation of the literature with the results of this case suggest that this instance of primary cerebellar LG arose as a consequence of an unusual EBV-associated B-cell lymphoproliferation. It is suggested that EBV may be a significant factor in the initiation of the abnormal proliferations of T-cells or B-cells reported in this disorder.

Identification of target antigens for the human cytotoxic T cell response to Epstein-Barr virus (EBV): implications for the immune control of EBV-positive malignancies

Epstein-Barr virus (EBV), a human herpes virus with oncogenic potential, persists in B lymphoid tissues and is controlled by virus-specific cytotoxic T lymphocyte (CTL) surveillance. On reactivation in vitro, these CTLs recognize EBV-transformed lymphoblastoid cell lines (LCLs) in an HLA class I antigen-restricted fashion, but the viral antigens providing target epitopes for such recognition remain largely undefined. Here we have tested EBV-induced polyclonal CTL preparations from 16 virus-immune donors on appropriate fibroblast targets in which the eight EBV latent proteins normally found in LCLs (Epstein-Barr nuclear antigen [EBNA] 1, 2, 3A, 3B, 3C, leader protein [LP], and latent membrane protein [LMP] 1 and 2) have been expressed individually from recombinant vaccinia virus vectors. Most donors gave multicomponent responses with two or more separate reactivities against different viral antigens. Although precise target antigen choice was clearly influenced by the donor's HLA class I type, a subset of latent proteins, namely EBNA 3A, 3B, and 3C, provided the dominant targets on a range of HLA backgrounds; thus, 15 of 16 donors gave CTL responses that contained reactivities to one or more proteins of this subset. Examples of responses to other latent proteins, namely LMP 2 and EBNA 2, were detected through specific HLA determinants, but we did not observe reactivities to EBNA 1, EBNA LP, or LMP 1. The bulk polyclonal CTL response in one donor, and components of that response in others, did not map to any of the known latent proteins, suggesting that other viral target antigens remain to be identified. This work has important implications for CTL control over EBV-positive malignancies where virus gene expression is often limited to specific subsets of latent proteins.

Genetic modulation of antigen presentation by HLA-B27 molecules

In studies of antigenic peptide presentation, we have found a healthy volunteer whose lymphoblastoid cells were unable to present three different virus-derived epitopes to cytotoxic T lymphocytes (CTL) despite expressing the correct restricting HLA-B27 molecules on the cell surface. B cell lines were established from other members of the donor's family, including individuals suffering from ankylosing spondylitis and related diseases, and were tested for their ability to function as target cells in the same assay. None of the eight B cell lines that expressed HLA-B27 presented a known peptide epitope to CTL. However, cells from a family member that expressed HLA-B8 could present an epitope peptide restricted by that molecule. The B27 molecule in this family proved to be the B2702 subtype on isoelectric focusing gels, appearing in exactly the same position as B2702 from other cell lines that did present the peptide. To exclude mutations resulting in noncharged amino acid substitutions, cDNA coding for B2702 was cloned from the proband's cell line and sequenced. No coding changes were found. The cloned cDNA was transfected into HLA-A- and B-negative HMy/C1R cells, and the B2702 molecules generated in this environment rendered these cells, after incubation with peptide, susceptible to lysis by peptide-specific CTL. These data are compatible with the presence of a factor(s), possibly HLA linked, interfering with antigen presentation by otherwise normal B2702 molecules in this family.

Carboxyl-terminal and central regions of human immunodeficiency virus-1 NEF recognized by cytotoxic T lymphocytes from lymphoid organs. An in vitro limiting dilution analysis

Cytotoxic T lymphocytes (CTL) specific for human immunodeficiency virus (HIV) proteins have been analyzed in lymphoid organs from seropositive patients. Indeed, an active HIV replication coexists with a major CD8+ lymphocytic infiltration in these organs. We have shown in a previous report that HIV-seropositive patients lungs were infiltrated by HIV specific CD8+ lymphocytes. In the present report, we show that HIV-specific CTL responses can also be detected in lymph nodes and spleens, and were mainly directed against the ENV, GAG, and NEF HIV-1 proteins. The primary NEF-specific CTL responses were further characterized by epitope mapping. Determination of epitope-specific CTL frequencies were performed by limiting dilution analysis. Our results indicated that, in addition to the central region of NEF (AA66-148), a new immunodominant region is recognized by CTL. This region corresponds to the carboxyl-terminal domain of NEF (amino acids 182-206). AA182-206 is recognized in association with at least two common human histocompatibility leukocyte antigen (HLA) molecules (HLA-A1 and B8), with clonal frequencies of one CTL per 10(-5) to 10(-6) splenic lymphocytes. Our data indicate that lymphoid organs may represent a major reservoir for in vivo activated HIV-specific CTL. Furthermore, the carboxyl-terminal domain of NEF was found to be conserved among several HIV strains. Therefore, our finding is of interest for further HIV vaccines development.

Human autologous tumor-specific T cells in malignant melanoma

T cell lines and clones with autologous tumor-specific activity have been developed in malignant melanoma by stimulating peripheral blood lymphocytes (PBL), lymph node lymphocytes or tumor-infiltrating lymphocytes (TIL) with autologous melanoma cells in the presence of recombinant interleukin 2 (rIL2). T-cell lines and clones have been developed with specific cytotoxicity and/or proliferative responses for autologous melanoma targets but not for allogeneic melanoma tumor cells, autologous normal cells or natural killer (NK)-sensitive targets. The concentration of rIL2 is critical for the generation of autologous tumor-specific T-cell lines, with low rIL2 concentrations (up to 800 IU/ml) facilitating the growth of T-cell lines with tumor-specific activity. The alpha beta T-cell receptor (TCR) and the CD3 antigen are involved in specific cytotoxicity and/or proliferative responses of these T-cell lines and clones. An oligoclonal pattern of beta-chain TCR gene rearrangements was observed on T-cell lines and clones with autologous tumor-specific cytotoxicity, suggesting that they are comprised of T cells that have undergone a clonal expansion in response to particular antigen. Autologous tumor-specific cytotoxic T cells are HLA-restricted and recognize on the melanoma tumor cells HLA Class I or possibly Class II antigens plus a tumor-specific determinant. TIL from patients with metastatic melanoma have unique characteristics in comparison with PBL and lymph node lymphocytes and they appear to contain substantial proportions of T cells that have been locally sensitized to autologous tumor cells. Single stimulation of TIL with autologous tumor cells in the presence of rIL2 is sufficient for the generation of T cell lines with autologous tumor-specific activity, whereas, multiple stimulation of PBL and lymph node lymphocytes was required to achieve the same purpose. TIL-derived T cell lines have been expanded in rIL2 in vitro by at least 1,500-fold without losing their activity. Approximately, 40% of the patients exhibited complete or partial responses to adoptive immunotherapy with melanoma TIL and rIL2.

Peptide binding to empty HLA-B27 molecules of viable human cells

Intracellular binding of antigenic peptides by polymorphic class I major histocompatibility complex molecules creates the ligands recognized by receptors of CD8+ T cells. Previously described in vitro assays of peptide binding to class I molecules have been limited by either the low proportion of accessible binding sites or the lack of allelic specificity. Here we describe a system in which the human class I molecule HLA-B27 binds considerable amounts of an influenza peptide with precise allelic discrimination. Binding requires viable cells, is stimulated by gamma-interferon and is inhibited by brefeldin A. Our results are consistent with the presence of fairly stable 'empty' HLA-B27 molecules at the cell surface. By contrast, analysis of the binding of a second influenza peptide indicates that empty HLA-Aw68 molecules are relatively short-lived. We speculate that HLA-B27 might bind extracellular peptides in vivo and that this property could underlie its association with autoimmune disease.

Binding of radioiodinated influenza virus peptides to class I MHC molecules and to other cellular proteins as analyzed by gel filtration and photoaffinity labeling

In order to determine how T cell-presented peptides associate with the antigen binding sites (desetopes) of class I major histocompatibility complex (MHC) molecules and how they might be scavenged from an endogenous processing pathway for transfer to those molecules, we characterized the binding of two synthetic peptides restricted by HLA-B37 or HLA-A2 to class I MHC molecules and to cellular proteins of histotyped cell lines, by gel filtration and photo-affinity labeling techniques. In gel filtration binding studies, each peptide associated with immunopurified class I MHC molecules from cells with its restricting, histotype, but little was bound to class I MHC molecules from cells without the restricting histotype and none was bound to bovine serum albumin. After crosslinkage of a radioiodinated photoreactive derivative of influenza virus nucleoprotein peptide NP(336-355Y) and immunoprecipitations with antibodies to class I MHC molecules, that peptide was found to bind to immunopurified class I MHC molecules from HLA-B37+ but not HLA-B37- cells. Binding of the [125I]NP peptide increased from 6 to 12 hr of incubation and was competed by unlabeled, NP peptide but not by HLA-A2-restricted, influenza virus matrix MA(57-73). The principal microsomal membrane proteins binding [125I]NP were about 65, 45 and 33 kD.

Correlation between CD8 dependency and determinant density using peptide-induced, Ld-restricted cytotoxic T lymphocytes

We have taken advantage of some unique properties of H-2Ld to investigate the determinant density requirements for cytotoxic T lymphocyte (CTL) priming versus effector function and to correlate the determinant density requirements with CD8 dependency. In a previous study (Lie, W.-R., N. B. Myers, J. Gorka, R. J. Rubocki, J. M. Connolly, and T. H. Hansen. 1990. Nature [Lond.]. 344:439), we demonstrated that culturing normal cells with peptides known to be restricted by H-2Ld led to a two- to fourfold increase in surface Ld expression. In the present study, we demonstrate the generation of Ld-restricted, peptide-specific in vitro primary CTL by culturing spleen cells with murine cytomegalovirus or tum- peptide at concentrations previously shown to result in maximum induction of Ld expression. Target cells can be sensitized for recognition by these CTL with lower dose of peptide than are required for the primary sensitization. This demonstrates differences in the determinant density requirements for priming versus effector function. The in vitro primary CTL generated with peptide can weakly lyse target cells that express the determinant endogenously, and CTL lines and clones capable of strong lysis of endogenous expressors are easily obtained. In both cases, target cells treated with exogenous peptide are lysed better than target cells expressing antigen endogenously. This suggested that there are differences in the determinant density of peptide-fed versus endogenous targets. This interpretation was substantiated when it was observed that the level of lysis of target cells expressing endogenous determinants correlated inversely with the amount of peptide required to sensitize targets for recognition by various tum- -specific CTL clones. Furthermore, simultaneous titration of both the peptide used to treat target cells and the antibody to CD8 revealed that the various CTL clones analyzed displayed widely disparate CD8 dependencies. In each case, the CD8 dependency correlated inversely with the determinant density requirement. Therefore, CD8 dependency of CTL is relative, but shows an absolute and quantitative correlation with their dependency on determinant density. These findings suggest that under physiologic conditions, where only low determinant densities are likely to be encountered, all CTL clones will show at least partial CD8 dependency.

The comparative frequency of human T cells responding to a native antigen and a synthetic peptide derived from Streptococcus mutans

The frequency of human peripheral blood T cells responding to a 21-residue synthetic peptide (SP 21) derived from the sequence of a 3.8-kDa streptococcal antigen was estimated by limiting dilution analysis and compared with the frequency of cells responding to the native, cross-reactive 185-kDa streptococcal antigen. Frequency estimates were made by measuring both [3H]thymidine incorporation and IL 2 production in the same cell cultures. The results provided frequency estimates for SP 21-reactive cells of between 1:42 147 and 1:306 110, with a mean of 1:160 617 by [3H]thymidine incorporation, and 1:139 893 to 1:241 315 (mean 1:165 315) using the IL 2 assay. With the native 185-kDa streptococcal antigen, frequency estimates were between 1:38 393 and 1:86 142 (mean 1:169 934) according to the proliferative response and 1:22 462 and 1:100 400 (mean 1:61 189) by the IL 2 assay.

Clearance of a persistent paramyxovirus infection is mediated by cellular immune responses but not by serum-neutralizing antibody

Infection of the lungs of immunodeficient mice with the paramyxovirus simian virus 5 (SV5) was prolonged compared with the time course of infection in immunocompetent mice. Although there was a significant increase in both viral RNA and proteins, little infectious virus was produced. Adoptive transfer of immune lymphocytes (isolated from the spleens of mice previously infected with SV5) but not of nonimmune lymphocytes increased the speed of clearance of virus from the lungs of immunodeficient mice. In contrast, passive transfer of a pool of neutralizing monoclonal antibodies specific for the HN and F glycoproteins of SV5 did not have a significant effect on the speed of clearance of virus. Furthermore, no significant increase in the rate of virus clearance was observed upon adoptive transfer of purified immune B lymphocytes to SV5-infected immunodeficient mice despite production by the mice of high titers of neutralizing antibodies. Evidence is presented that CD8+ effector cells are primarily responsible for the clearance observed. The general significance of these results with respect to immune clearance of persistent virus infections is discussed.

Selective and non-selective loss of immunoregulatory molecules (HLA-A,B,C antigens and LFA-3) in transitional cell carcinoma

The expression of the major histocompatibility complex (MHC) class I and II antigens and lymphocyte function-associated antigen-3 (LFA-3) was investigated using immunohistochemical staining of bladder tissue sections from 18 patients with transitional cell carcinoma (TCC) and two normal bladder specimens. The expressions of HLA-A,B,C antigens varied greatly between different tumours. Complete loss was observed in one of 18 cases. Moderate to strong expression of HLA-A,B,C antigens was observed in 10 of 18 cases with the remaining seven cases showing either weak expression or expression on only a proportion of the tumour cells. Selective loss of HLA-Bw6 was seen in one of 18 cases. In many cases heterogenous and often focal expression of HLA-D products was seen. In one case tumour cells not expressing HLA-DR antigens were adjacent to strongly HLA-DR expressing non-neoplastic bladder epithelium, indicating a lack of inducible HLA-DR in the tumour cells. LFA-3 was undetectable in two of 18 cases with the remaining 16 cases showing moderate to strong expression of the molecule. These findings indicate that a substantial proportion of bladder tumours have one or more of a wide range of different alterations in the expressions of immunoregulatory molecules that could contribute to escape from immune surveillance.

In vitro human cytotoxic T cell responses against influenza A virus can be induced and selected by synthetic peptides

Studies on human anti-influenza cytolytic activities have demonstrated that cytotoxic T lymphocytes (CTL) from HLA-B37 individuals react preferentially with the peptide corresponding to residues 335-349 of the nucleoprotein, whereas CTL from HLA-A2 donors recognize peptide 57-68 from the viral matrix as a dominant epitope. We studied the secondary CTL response, obtained from peripheral blood mononuclear cells, of an HLA-A2+,B37+ individual stimulated either by infectious virus or by synthetic peptides. Only an HLA-B37-restricted response was detected after stimulation by the whole virus, showing an immunodominance of this activity over that restricted by HLA-A2. Moreover, human cytotoxic cell lines were successfully obtained after stimulation of peripheral blood mononuclear cells with synthetic peptides. Under these conditions, it was possible to selectively reveal the existence of an HLA-A2-restricted activity directed against the matrix peptide. These results demonstrate that, at least in vitro, it is possible to stimulate a latent repertoire by using synthetic peptides. Nevertheless, we could not induce a response against the matrix or the nucleoprotein peptides in HLA-A2- or B37- individuals, suggesting that a finer selection of synthetic peptides would be necessary for their possible utilization to induce CTL during vaccination.

HLA-B37 and HLA-A2.1 molecules bind largely nonoverlapping sets of peptides

T-cell recognition of peptides that are bound and presented by class I major histocompatibility complex molecules is highly specific. At present it is unclear what role class I peptide binding plays relative to T-cell receptor specificity in determination of immune recognition. A previous study from our group demonstrated that the HLA-A2.1 molecule could bind to 25% of the members of a panel of unrelated synthetic peptides as assessed by a functional peptide competition assay. To determine the peptide-binding specificity of another HLA class I molecule, we have examined the capacity of this panel of peptides to compete for the presentation of influenza virus nucleoprotein peptide NP-(335-350) by HLA-B37 to NP-peptide-specific HLA-B37-restricted cytotoxic T-lymphocyte lines. Forty-two percent of peptides tested were capable of inhibiting NP-(335-350) presentation by HLA-B37. Remarkably, none of these HLA-B37-binding peptides belong to the subset that was previously shown to bind to the HLA-A2.1 molecule. Only the NP-(335-350) peptide was capable of binding to both HLA-A2.1 and HLA-B37. These findings demonstrate that the peptide-binding specificities of HLA-B37 and HLA-A2.1 are largely nonoverlapping and suggest that, from the universe of peptides, individual HLA class I molecules can bind to clearly distinct subsets of these peptides.

The 22,000-kilodalton protein of respiratory syncytial virus is a major target for Kd-restricted cytotoxic T lymphocytes from mice primed by infection

Recombinant vaccinia viruses containing the 22-kilodalton protein (matrixlike or 22K protein) or phosphoprotein gene from respiratory syncytial virus were constructed. These recombinant viruses expressed proteins which were immunoprecipitated by appropriate respiratory syncytial virus antibodies and comigrated with authentic proteins produced by respiratory syncytial virus infection. The new recombinant viruses (and others previously described containing the attachment glycoprotein, fusion, or nucleoprotein genes of respiratory syncytial virus) were used to infect target cells for cultured polyclonal cytotoxic T lymphocytes generated from the spleens of BALB/c or DBA/2 mice primed by intranasal infection with respiratory syncytial virus. Respiratory syncytial virus-specific cytotoxic T lymphocytes (CTL) showed strong Kd (but not Dd)-restricted recognition of the 22K protein. As previously reported, the fusion protein and nucleoprotein were both seen by CTL, but recognition of these proteins was comparatively weak. There was no detectable recognition of other respiratory syncytial virus proteins tested (including phosphoprotein). 22K protein-specific splenic memory CTL persisted for at least 11 months after infection of BALB/c mice. Priming BALB/c mice with recombinant vaccinia virus containing the 22K protein gene induced respiratory syncytial virus-specific memory CTL at lower levels than that previously reported following infection with a similar recombinant containing the fusion protein gene. These data identify the 22K protein as a major target antigen for respiratory syncytial virus-specific CTL from H-2d mice primed by respiratory syncytial virus infection.

Isolation and identification of a polypeptide in the Hsp 70 family that binds substance P

During the course of an attempt to purify the substance P (SP) receptor from horse salivary glands by substance P-affinity chromatography, a polypeptide of Mr = 78,000 was isolated. The first fifteen amino acid residues at the amino terminus were determined and, unexpectedly, were found to be identical with the amino terminus of a glucose-regulated protein (GRP) of the same molecular weight, a protein that has been identified as a member of the heat shock protein family. This finding raises the intriguing possibility that SP may interact in vivo with GRPs and other members of the heat shock protein family and play a role in modulating their biological activities.

Recruitment of alloreactive cytotoxic T lymphocytes by an antigenic peptide

To investigate the requirements for induction of cytotoxic T lymphocytes (CTL) by peptides we chose the 16-residue nucleoprotein peptide (NPP; 365-380) from the influenza virus A/NT/60/68 as model substrate that is recognized in conjunction with major histocompatibility complex H-2d. Here we present that CTL can be raised from naive animals by repeated in vitro stimulation with high concentrations of peptide. The frequency of this response can be boosted by immunization of the animals with NPP-conjugated to ovalbumin as a carrier. However, in contrast to NPP-specific CTL lines raised from virus-primed animals none of the peptide-induced CTL lines were able to lyse virus-infected targets. Although they did not show an apparent difference in fine specificity of the peptide recognized, their affinity to the target cells was 100-fold lower than that of CTL from virus-primed animals as estimated from the peptide concentration needed to achieve significant lysis. In addition, the activity of peptide-induced CTL was very sensitive to blocking by anti-CD8 antibodies as compared to virus-specific CTL. Furthermore, all peptide-induced CTL showed a high second reactivity for allogeneic H-2k targets. Therefore, it is argued that high epitope density achieved by high peptide concentrations can in vitro recruit lymphocytes of another specificity. For the tested peptide the reactive T lymphocytes showed high alloreactivity.