Semin Immunol 1997 Oct;9(5):269-270

Introduction: Emerging vaccine strategies.

Barber B

[Record supplied by publisher]

No abstractCopyright 1997 Academic Press Limited Copyright 1997Academic Press Limited

PMID: 9367918

Semin Immunol 1997 Oct;9(5):293-301

The immunotargeting approach to adjuvant-independent subunit vaccine design.

Barber BH

Recently there has been considerable interest in exploring adjuvant-independent approaches to the enhancement of immunogenicity. One strategy which has emerged in response to this need is the immunotargeting approach to subunit vaccine design. Immunotargeting involves the conjugation of non-self antigens to monoclonal antibodies specific for cell surface determinants (e.g. class II MHC) on antigen presenting cells in vivo. Saline injections of these immunoconjugates have been shown to promote significant IgG responses to the delivered antigens in a number of different animal model studies. Oral and nasal immunizations in mice with anti-class II MHC immunoconjugates induce both secretory IgA and systemic IgG responses. Recombinant anticlass II MHC antibodies with defined B-cell and T-cell epitopes incorporated into their primary sequence have recently been used to induce epitope specific antibody responses in macaques. Thus the potential now exists for the rational design of adjuvant-independent human vaccine candidates based on a recombinant immunotargeting anti-body framework.

The dominant role of bone marrow-derived cells in CTL induction following plasmid DNA immunization at different sites.

Iwasaki A, Torres CA, Ohashi PS, Robinson HL, Barber BH

Although plasmid DNA immunization provides an effective means of inducing CTL responses to an expressed Ag, the mechanism by which CTL precursors are activated remains to be established. Insights could be gained by identifying the cells responsible for Ag presentation when DNA is introduced into different tissue sites. By immunizing parent into F1 bone marrow chimeric mice with an influenza nucleoprotein-expressing plasmid, we have demonstrated that the key cells in this presentation process for both gene gun-mediated epidermal injection and needle intramuscular injection of plasmid DNA are bone marrow derived. Furthermore, as assessed by intramuscular injection, coexpression of nucleoprotein with the costimulatory molecule B7-2, or the cytokines granulocyte-macrophage CSF and IL-12, did not convert nonhemopoietic cells into APCs. Thus, for two distinctly different modes of DNA immunization, in one case with or without coexpressed immunostimulatory factors, the APCs were consistently found to be of hemopoietic origin.

PMID: 9200432, UI: 97343905

Murine antibody responses to the verotoxin 1 B subunit: demonstration of major histocompatibility complex dependence and an immunodominant epitope involving phenylalanine 30.

Bast DJ, Sandhu J, Hozumi N, Barber B, Brunton J

Structurally conserved verotoxin 1 (VT1) mutant derivatives, showing reduced receptor binding and cytotoxicity, may serve as natural toxoids to protect against VT-mediated disease. In this study, the antibody responses to the wild-type VT1 B subunit, a B-subunit mutant (Phe30Ala B), and the corresponding holotoxin (Phe30Ala HT) were examined in three inbred mouse strains. BALB/c (H-2d) and CBA (H-2k) mice produced strong antibody responses to both wild-type and mutant B subunits. VT1 B-raised sera reacted more strongly with VT1 B than with Phe30Ala B in enzyme-linked immunosorbent assays, while Phe30Ala B-raised sera reacted equally with VT1 B and Phe30Ala B. C57BL/6 (H-2b) and congenic BALB/c (BALB x B [H-2b]) mice produced no detectable antibody response to either VT1 B or Phe30Ala B. However, an anti-VT1 B antibody response was detected in H-2b mice immunized with biologically active Phe30Ala HT. Based on these observations, we conclude that the VT1 B subunit possesses a B-cell immunodominant epitope formed partly by phenylalanine 30 and that the B-subunit antibody response is dependent on the H-2 haplotype of the mouse strain. Our results also support a potential role for the A subunit in providing the T-cell help necessary to overcome a deficient B-subunit antibody response in H-2b mice.

PMID: 9199476, UI: 97342779

Enhanced CTL responses mediated by plasmid DNA immunogens encoding costimulatory molecules and cytokines.

Iwasaki A, Stiernholm BJ, Chan AK, Berinstein NL, Barber BH

In the course of examining epitope-specific CTL responses to intramuscular plasmid DNA immunization with influenza nucleoprotein (NP)-expressing vectors, a nonimmunogenic mutant NP (NP(o)) was identified. The coding region of NP(o) differed from the wild-type A/PR/8/34 NP sequence (designated NP(v)) by three amino acid alterations in the carboxyl-terminal portion of the molecule remote from the H-2K(d) epitope (147-155) being monitored. Correction of these mutations restored the immunogenicity of the native sequence, indicating that sequence alterations remote from the CTL epitope in question can profoundly influence its immunogenicity. In an effort to identify general, nonstructural means of enhancing the CTL response to weak plasmid DNA immunogens, vectors were constructed expressing NP(o) in tandem with the costimulatory molecules B7-1 or B7-2. Co-linear expression of NP(o) with B7-2, but not B7-1, significantly increased the NP epitope-specific CTL response. In addition, coinjection of these NP(o) plasmids with granulocyte-macrophage CSF- and/or IL-12-expressing vectors also restored near native NP-specific CTL responses. Thus, the coexpression of certain costimulatory molecules and/or cytokines, in concert with a non-self gene delivered as an intramuscular plasmid DNA immunogen, can significantly enhance Ag-specific CTL responses.

PMID: 9144471, UI: 97289566

AIDS Res Hum Retroviruses 1997 Apr 10;13(6):449-460

Recombinant antibodies with conformationally constrained HIV type 1 epitope inserts elicit glycoprotein 160-specific antibody responses in vivo.

Cook J, Barber BH

Although neutralizing epitopes have been identified on the HIV-1 gp120/gp41 envelope complex, efforts to exploit this information through the construction of synthetic peptide vaccines have been largely unsuccessful. Unfortunately, synthetic peptides tend to be poorly immunogenic, and most often lack the conformational characteristics of the corresponding epitope in the native protein. In an effort to circumvent these difficulties, we have utilized an anti-class II MHC antibody as a molecular scaffold for the construction of two conformationally constrained neutralizing HIV-1 epitopes. Previously we demonstrated that anti-class II MHC antibodies can function as vectors for the induction of adjuvant-independent antibody responses to incorporated epitopes. In this instance, one epitope, IHIGPGRAFYT, is the crown of the V3 loop from gp120, and the other, ELDKWAS, is a neutralizing epitope from gp41. The insertion of these epitopes into a specific loop region of the immunoglobulin heavy chain FR3 was found to preserve the anti-class II MHC-binding activity of these recombinant antibodies, and the inserts were recognized by epitope specific monoclonal antibodies. When utilized as immunogens, each of these epitope insertion antibodies was able to induce high-titer anti-HIV-1 gp160 responses in guinea pigs. These responses were conformation specific in that the anti-gp160 binding was not inhibited by the synthetic peptide corresponding to the epitope in question. These data demonstrate the potential to construct conformationally constrained HIV-1 epitope immunogens, and thus establish an alternative approach to the design of an effective HIV-1 subunit vaccine.

PMID: 9100986, UI: 97255639

J Immunol 1997 Apr 1;158(7):3081-3089

Role of IL-12 and 4-1BB ligand in cytokine production by CD28+ and CD28- T cells.

Chu NR, DeBenedette MA, Stiernholm BJ, Barber BH, Watts TH

The costimulatory receptor CD28 is important in the development of both Th1 and Th2 responses. To further assess the requirement for CD28 in the development of Th1 and Th2 responses, we analyzed the ability of T cells from wild-type or CD28- mice to secrete cytokines in MLRs with B lymphomas. We find that in the absence of added IL-12, B lymphomas expressing the alternate costimulatory ligand 4-1BBL can support the production of IL-2 and IL-4 but little detectable IFN-gamma by allogeneic CD28+ and CD28- T cells. IL-4 production by CD28+ or CD28- T cells responding to B7(low) B lymphomas was abrogated by blocking 4-1BB ligand-4-1BB interaction. When APC express high levels of B7 family molecules as well as 4-1BBL, soluble 4-1BB inhibits IL-4 production by CD28- but not by CD28+ cells. Addition of IL-12 to the CD28- MLRs results in increased production of IFN-gamma and decreased amounts of IL-2 and IL-4. Thus, both Th1 and Th2 responses can develop in the complete absence of a signal through the CD28 molecule. CD28+ and CD28- T cells differed, however, with respect to the effect of IL-12 on IL-4 production. IL-12 severely curtailed the amount of IL-4 produced in the CD28- T cell cultures but had a less profound effect on the level of IL-4 produced in the CD28+ cultures, suggesting that a strong signal through the CD28 molecule prevents down-regulation of IL-4 production by IL-12.

PMID: 9120260, UI: 97240747

J Immunol 1997 Jan 15;158(2):685-692

Presentation of an influenza nucleoprotein epitope incorporated into the H-2Db signal sequence requires the transporter-associated with antigen presentation.

Uger RA, Barber BH

In an effort to optimize the formation of peptide-specific CTL target structures in the context of plasmid DNA immunization, a strategy was developed to couple the biosynthesis of a class I heavy chain with its optimal binding epitope. Specifically, a cDNA expression vector was constructed with the influenza nucleoprotein epitope NP366-74 incorporated into the signal sequence of its restriction element H-2Db. Transporter associated with Ag presentation-expressing murine cell lines P815 (H-2d) and BW5147 (H-2k) transfected with this modified heavy chain expressed normal levels of plasmid-encoded Db at the cell surface, and were lysed by NP366-74-specific CTL. These results indicate that the modified signal sequence was successfully delivered to the endoplasmic reticulum, and the epitope within it processed for T cell recognition. In contrast, T2 cells, which lack the TAP transporter, when transfected with the same vector were not lysed by NP366-74 CTL, and exhibited an Ag-processing-defective phenotype. Thus, these data, which indicate TAP-dependent presentation of an optimal CTL epitope located in a signal sequence, challenge the effectiveness of Ag processing in the endoplasmic reticulum.

PMID: 8992984, UI: 97146037