摘要:

Chimeric human rhinoviruses (HRVs) have the potential to serve as vaccines against a wide variety of diseases. Such vaccines can be developed optimally by generating libraries of chimeric HRVs displaying immunogens from dangerous pathogens or tumor cells in many different conformations. Extremely large numbers of conformationally defined presentations of foreign epitopes can be produced efficiently by flanking transplanted epitopes with linkers, or adapters, of small segments of randomized amino acids. In addition, the individual residues of the immunogenic sequences can be encoded in proportion to their prevalence in databases, generating composite immunogens that function as mimotopes. The diversity of sequences and conformations improves the likelihood of generating immunologically valuable vaccine candidates. Chimeric viruses thus generated can be propagated and purified to select for viruses whose growth and physical stability are like those of wild-type HRV. Viruses containing a foreign epitope in antigenically relevant conformations can then be captured by immunoselection with neutralizing antibodies directed against the foreign pathogen. Using this approach, we have been able to generate HRV chimeras that present V3 loop sequences of the human immunodeficiency virus type 1 (HIV-1) in immunologically relevant conformations. Antisera directed against such chimeras can neutralize multiple strains of HIV-1 in cell culture, suggesting that the HRV14:HIV-1 chimeras may be presenting their V3 loop sequences in manners that mimic those of multiple strains of HIV. Immunologically interesting chimeras can be examined using X-ray crystallography to yield detailed information about the structures of chimeras with immunogenic epitopes. This information may lead to a greater understanding of key functional and structural elements of immunogenicity. The chimeric HRV system allows one to present virtually any protein epitope or mimitope thereof, identify viruses with immunological characteristics that mimic those of the foreign pathogen, and examine the structures of these immunogenic sequences at the atomic level.

ISSN:0300-5526    

DOI:10.1159/000150477

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Epitopes from human rhinovirus 14 (HRV-14) and human immunodeficiency virus type (HIV-1) have been expressed on the surface of particles of the plant virus, cowpea mosaic virus (CPMV). The chimaeras retain their ability to grow in plants and large quantities of virions can be easily purified. Immunological studies have shown that purified particles have the antigenic properties of the insert, and, in the case of the HIV-1 chimaera, can elicit the production of neutralising antibodies in mice. The chimaera containing the epitope from HRV-14 has been crystallised and the crystals shown to diffract to atomic resolution.

ISSN:0300-5526    

DOI:10.1159/000150478

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Presentation of subunit vaccines in a highly ordered aggregate form can result in enhanced immune responses. Coat protein (CP) monomers of a potyvirus (Johnsongrass mosaic virus) when produced in heterologous host expression systems (Escherichia coli, yeast and insect cells) self-polymerized to produce potyvirus-like particles (PVLPs). The N- and C-terminal regions of potyvirus CP are surface-exposed and are not required for assembly. Hybrid CP monomers containing short peptides fused to their N- and/or C-termini, or large target antigens fused to the N-terminus or replacing most of the N- or C-terminal exposed regions retained the ability to assemble into hybrid PVLPs. Such chimeric PVLPs were highly immunogenic in mice and rabbits even in the absence of any adjuvant. Potyvirus CP is highly versatile in accommodating peptides or large antigens and is able to present antigens exposed on the surface of virus-like particles. This, combined with the efficiency of high level bacterial and insect cell expression systems, makes PVLPs an attractive non-pathogenic and non-replicative vaccine carrier.

ISSN:0300-5526    

DOI:10.1159/000150479

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Data from long-term non-progressing human immunodeficiency virus (HIV)- infected individuals and populations at high risk suggest that an early cytolytic T cell response rather than the humoral immune response might be involved in controlling disease progression. These observations may be used as a guide to the type of response that a vaccine should induce. To clarify the role of different arms of the immune system in conferring protection, the candidate vaccine should allow a regulated, selective induction of different immune responses. Based on a better understanding of the molecular mechanisms regulating the morphogenesis of HIV, we developed an autologous, non-replicating and safe antigen delivery system. This system takes advantage of molecular characteristics of the HIV group-specific antigens (gag) to self-assemble to highly immunogenic virus-like particles (VLP). The immunogenicity of the gag-derived VLP was expanded either by replacing defined domains by selected HIV-1 cytotoxic T lymphocyte (CTL) epitopes (type 1 VLP) or by stable anchoring derivatives of the HIV-1 envelope protein on the surface of the VLP (type 2 VLP). In complete absence of adjuvants, type 1 and type 2 VLP stimulated CD8+ CTL in BALB/c mice, which specifically recognised HIV sequences. In contrast to type 1 VLP, generating an HIV-specific CTL response in the absence of e«v-specific antibodies, type 2 VLP induced both arms of the immune system including reasonable levels of neutralising antibodies. Initial studies performed in rhesus macaques confirmed these results. Thus, depending on the type and formulation of the VLP, the proposed antigen delivery system allows either the induction of a CTL response (1) in the absence and (2) the presence of an envelope-specific antibody response. A comparison of these approaches in appropriate animal models might contribute to further define the correlates of protection

ISSN:0300-5526    

DOI:10.1159/000150480

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

The hepatitis B virus (HBV) core gene codes for two partially colinear antigens: a secreted antigen (HBeAg) and the particulate core antigen (HBcAg), which assembles to form subviral particles and in virions contains the viral genome and polymerase. In this review we summarize data on the immune recognition of HBc/eA and recent progress in the use of HBcAg as a carrier moiety for heterologous epitopes. During HBV infection, HBcAg and HBeAg are important targets of antiviral immunity. HBcAg and HBeAg are serologically distinct but share all characterized T-cell epitopes. The particulate HBcAg can elicit T-cell-independent as well as T-cell-dependent antibody responses, HBeAg is a strictly T-cell-dependent antigen. Neonatal tolerance to maternally derived circulating HBeAg may facilitate chronic HBV infection after vertical transmission of HBV. In a murine transgenic model, HBc/eAg-specific Thl cells were more readily anergized, whereas Th2 cells more easily escaped tolerization. In human HBV infection, acute adult HBV infection with subsequent virus elimination was characterized by Thl-like α-HBV serum IgG subtype distribution, whereas a Th2-like distribution of IgG subtypes was observed during chronic infection. During chronic infection, core gene mutants which abolish HBeAg synthesis were frequently observed. To exploit the unusual immunogenicity of particulate HBcAg as a vaccine carrier moiety, insertion sites for foreign epitopes were defined in recombinant expression systems. While fusion of epitopes to the N-terminus required a linker sequence for surface accessibility, both fusion to the N-terminus and to the C-terminus was compatible with particle assembly and preserved the native antigenicity and immunogenicity of HBcAg. Epitope insertion at an immunodominant internal site of HBcAg reduced the HBcAg immunogenicity and antigenicity and most drastically enhanced the immunogenicity of the inserted foreign epitopes. This internal site of HBcAg was used to express circumsporozoite antigen (CS) repeat epitopes of two rodent malaria parasites and of Plasmodiumfalciparum. Purified hybrid HBcAg-CS proteins were particulate and displayed CS antigenicity as well as reduced native HBc antigenicity. Immunization of several mouse strains with HBcAg-CS hybrid particles resulted in high-titered serum anti-CS antibodies representing all murine IgG isotypes and protected BALB/c mice against plasmodial challenge. Immunization of mice with HBcAg or HBcAg-CS particles formulated on alum, complete Freund’s or incomplete Freund’s adjuvant resulted in equivalent anti-CS and anti-HBc serum antibody titers. Preexisting immunity to HBcAg did not significantly alter the immunogenicity of hybrid HBcAg particles suggesting that carrier-specific immune suppression does not limit the use of hybrid HBcAg with internal insertions. Immunization with HBcAg-CS particles universally primed HBcAg-specific T cells and in addition CS-specific T cells were if the insert contained a CS-specific T-cell site for the corresponding murine MHC class II haplotype. The internal amino acid position in HBcAg is therefore permissive for the inclusion of heterologous T-helper as well as B-cell epit

ISSN:0300-5526    

DOI:10.1159/000150481

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

H-2d mice generated a major histocompatibility complex (MHC) class I (Ld)-restricted T-cell response of defined restriction and epitope specificity to the hepatitis B virus small surface antigen (HBsAg). Here, we compare different vaccination techniques that prime in vivo class I-restricted, murine cytotoxic T lymphocyte (CTL) precursors and specific serum antibody responses. CTL were efficiently primed by the injection of low doses of recombinant native HBsAg particles without adjuvants, by the injection of low doses of denatured HBsAg monomers without adjuvants, by infection with recombinant vaccinia virus carrying a HBsAg-encoding gene, or by intramuscular transfer of plas-mid DNA encoding HBsAg under appropriate promoter control. The observation that the injection of 100 ng to 1 µg of native HBsAg ‘virus-like particles’ (VLP) without adjuvants is an exogenous antigen preparation that efficiently primes class I-restricted CTL responses was unexpected. It reveals a novel aspect of the immunogenicity of VLP for T c

ISSN:0300-5526    

DOI:10.1159/000150482

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Occasionally, a major change in vaccine methodology comes along. Such would appear to be the case with the advent of DNA-mediated immunization, colloquially known as DNA vaccines. This represents a radical new way to deliver antigens; it involves the direct introduction of a plasmid DNA encoding an antigenic protein which is then expressed within cells of the organism. This leads to surprisingly strong immune responses, involving both the humoral and cellular arms of the immune system. DNA-mediated immunization to a single antigen can provide protection against infection by a pathogen. Here, a guide is provided comprising twelve steps to help design and carry out DNA-mediated immunization. This approach to immunization will greatly facilitate studies of immunophysiological responses to antigens of pathogenic organisms. An Internet site (URL: http://www.genweb.com/Dnavax/dnav ax.html) has been created to help promote this potentially revolutionary approach to vaccination in the service of public health.

ISSN:0300-5526    

DOI:10.1159/000150483

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Chimaera was a monster in ancient Greek mythology combining elements from different animal species in its body. Modern molecular biology enabled the generation of harmless but useful chimaeras consisting of elements from different nonrelated viruses. The objective is that the resulting chimaeras form highly immunogenic virus-like particles (VLPs). Such chimaeric VLPs can be used as highly efficient carriers for sequential and conformational B cell epitopes and T cell epitopes. Most VLPs are readily produced in heterologous hosts and are easy to purify. This article deals with various systems of VLPs described in this topical issue of Intervirology and makes comparisons with chimaeric replication-competent viruses, recombinant virus vectors expressing foreign proteins, and DNA vaccines.

ISSN:0300-5526    

DOI:10.1159/000150484

出版商:S. Karger AG    

年代:1996

数据来源: Karger

ISSN:0300-5526    

DOI:10.1159/000150485

出版商:S. Karger AG    

年代:1996

数据来源: Karger

ISSN:0300-5526    

DOI:10.1159/000150486

出版商:S. Karger AG    

年代:1996

数据来源: Karger