Showing papers on "Immunogenicity published in 2003"

CpG DNA as a vaccine adjuvant

Abstract: Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs trigger cells that express Toll-like receptor 9 (including human plasmacytoid dendritic cells and B cells) to mount an innate immune response characterized by the production of Th1 and proinflammatory cytokines. When used as vaccine adjuvants, CpG ODNs improve the function of professional antigen-presenting cells and boost the generation of humoral and cellular vaccine-specific immune responses. These effects are optimized by maintaining ODNs and vaccine in close proximity. The adjuvant properties of CpG ODNs are observed when administered either systemically or mucosally, and persist in immunocompromised hosts. Preclinical studies indicate that CpG ODNs improve the activity of vaccines targeting infectious diseases and cancer. Clinical trials demonstrate that CpG ODNs have a good safety profile and increase the immunogenicity of coadministered vaccines.

Recombinant BCG exporting ESAT-6 confers enhanced protection against tuberculosis.

Abstract: The live tuberculosis vaccines Mycobacterium bovis BCG (bacille Calmette-Guerin) and Mycobacterium microti both lack the potent, secreted T-cell antigens ESAT-6 (6-kDa early secretory antigenic target) and CFP-10 (10-kDa culture filtrate protein). This is a result of independent deletions in the region of deletion-1 (RD1) locus, which is intact in virulent members of the Mycobacterium tuberculosis complex. To increase their immunogenicity and protective capacity, we complemented both vaccines with different constructs containing the esxA and esxB genes, which encode ESAT-6 and CFP-10 respectively, as well as a variable number of flanking genes. Only reintroduction of the complete locus, comprising at least 11 genes, led to full secretion of the antigens and resulted in specific ESAT-6-dependent immune responses; this suggests that the flanking genes encode a secretory apparatus. Mice and guinea pigs vaccinated with the recombinant strain BCG::RD1-2F9 were better protected against challenge with M. tuberculosis, showing less severe pathology and reduced dissemination of the pathogen, as compared with control animals immunized with BCG alone.

Enhanced T-cell immunogenicity of plasmid DNA vaccines boosted by recombinant modified vaccinia virus Ankara in humans.

Abstract: In animals, effective immune responses against malignancies and against several infectious pathogens, including malaria, are mediated by T cells. Here we show that a heterologous prime-boost vaccination regime of DNA either intramuscularly or epidermally, followed by intradermal recombinant modified vaccinia virus Ankara (MVA), induces high frequencies of interferon (IFN)-gamma-secreting, antigen-specific T-cell responses in humans to a pre-erythrocytic malaria antigen, thrombospondin-related adhesion protein (TRAP). These responses are five- to tenfold higher than the T-cell responses induced by the DNA vaccine or recombinant MVA vaccine alone, and produce partial protection manifest as delayed parasitemia after sporozoite challenge with a different strain of Plasmodium falciparum. Such heterologous prime-boost immunization approaches may provide a basis for preventative and therapeutic vaccination in humans.

Comparative immunogenicity in rhesus monkeys of DNA plasmid, recombinant vaccinia virus, and replication-defective adenovirus vectors expressing a human immunodeficiency virus type 1 gag gene

Abstract: Cellular immune responses, particularly those associated with CD3 CD8 cytotoxic T lymphocytes (CTL), play a primary role in controlling viral infection, including persistent infection with human immunodeficiency virus type 1 (HIV-1). Accordingly, recent HIV-1 vaccine research efforts have focused on establishing the optimal means of eliciting such antiviral CTL immune responses. We evaluated several DNA vaccine formulations, a modified vaccinia virus Ankara vector, and a replication-defective adenovirus serotype 5 (Ad5) vector, each expressing the same codon-optimized HIV-1 gag gene for immunogenicity in rhesus monkeys. The DNA vaccines were formulated with and without one of two chemical adjuvants (aluminum phosphate and CRL1005). The Ad5-gag vector was the most effective in eliciting anti-Gag CTL. The vaccine produced both CD4 and CD8 T-cell responses, with the latter consistently being the dominant component. To determine the effect of existing antiadenovirus immunity on Ad5-gag-induced immune responses, monkeys were exposed to adenovirus subtype 5 that did not encode antigen prior to immunization with Ad5-gag. The resulting anti-Gag T-cell responses were attenuated but not abolished. Regimens that involved priming with different DNA vaccine formulations followed by boosting with the adenovirus vector were also compared. Of the formulations tested, the DNA-CRL1005 vaccine primed T-cell responses most effectively and provided the best overall immune responses after boosting with Ad5-gag. These results are suggestive of an immunization strategy for humans that are centered on use of the adenovirus vector and in which existing adenovirus immunity may be overcome by combined immunization with adjuvanted DNA and adenovirus vector boosting.

Enhanced Immunogenicity and Protective Efficacy Against Mycobacterium tuberculosis of Bacille Calmette-Guérin Vaccine Using Mucosal Administration and Boosting with a Recombinant Modified Vaccinia Virus Ankara

Abstract: Heterologous prime-boost immunization strategies can evoke powerful T cell immune responses and may be of value in developing an improved tuberculosis vaccine. We show that recombinant modified vaccinia virus Ankara, expressing Mycobacterium tuberculosis Ag 85A (M.85A), strongly boosts bacille Calmette-Guerin (BCG)-induced Ag 85A specific CD4(+) and CD8(+) T cell responses in mice. A comparison of intranasal (i.n.) and parenteral immunization of BCG showed that while both routes elicited comparable T cell responses in the spleen, only i.n. delivery elicited specific T cell responses in the lung lymph nodes, and these responses were further boosted by i.n. delivery of M.85A. Following aerosol challenge with M. tuberculosis, i.n. boosting of BCG with either BCG or M.85A afforded unprecedented levels of protection in both the lungs (2.5 log) and spleens (1.5 log) compared with naive controls. Protection in the lung correlated with the induction of Ag 85A-specific, IFN-gamma-secreting T cells in lung lymph nodes. These findings support further evaluation of mucosally targeted prime-boost vaccination approaches for tuberculosis.

Immunoreactivity in mammals of two typical plant glyco-epitopes, core α(1,3)-fucose and core xylose

Abstract: The presence of nonmammalian core alpha(1,3)-fucose and core xylose glyco-epitopes on glycans N-linked to therapeutic glycoproteins produced in plants has raised the question of their immunogenicity in human therapy. We address this question by studying the distribution of these N-glycans in pea, rice, and maize (which are the crops intended for the production of therapeutic proteins) and by reinvestigating their immunogenicity in rodents. We found that immunization with a model glycoprotein, horseradish peroxidase, elicits in C57BL/6 mice and rats the production of antibodies (Abs) specific for core alpha(1,3)-fucose and core xylose epitopes. Furthermore, we demonstrated that about 50% of nonallergic blood donors contains in their sera Abs specific for core xylose, whereas 25% have Abs against core alpha(1,3)-fucose. These Abs probably result from sensitization to environmental antigens. Although the immunological significance of these data is too speculative at the moment, the presence of such Abs might introduce some limitations to the use of plant-derived biopharmaceutical glycoproteins, such as an accelerated clearance during human therapy.

Recombinant hepatitis B vaccine (Engerix-B): a review of its immunogenicity and protective efficacy against hepatitis B.

Abstract: Engerix-B® (Hep-B[Eng]) is a noninfectious recombinant DNA vaccine containing hepatitis B surface antigen (HBsAg). It is produced from genetically engineered yeast (Saccharomyces cerevisiae). Intramuscular Hep-B(Eng) [0-, 1-, 6-month schedule] has excellent immunogenicity in healthy neonates and infants, children, adolescents and adults, with seroprotection rates of 85–100% seen ≈1 month after the final dose of vaccine; seroprotection was defined as an antibody against HBsAg (anti-HBs) titre of ≥10 IU/L. The use of alternative Hep-B(Eng) immunisation schedules (e.g. a 0-, 1-, 2-, 12-month schedule in neonates and infants, 0-, 12-, 24-month or two-dose schedules in children and adolescents, and accelerated schedules in adults) have also been associated with high rates of seroprotection. Seroprotection rates were generally similar with Hep-B(Eng) and the recombinant vaccine Recombivax HB® (Hep-B[Rax]) or plasma-derived vaccines (PDVs)≈=1 month after the final dose (although anti-HBs geometric mean titres were significantly higher with Hep-B[Eng] than with Hep-B[Rax]). One month after the final dose, adults had significantly higher seroprotection rates with the recombinant triple-antigen vaccine Bio-Hep-B® (Hep-B[Bio]) than with Hep-B(Eng), although seroprotection rates in healthy infants were similar with Hep-B(Eng) and Hep-B(Bio). Hep-B(Eng) had excellent immunogenicity in several groups considered at high risk of acquiring hepatitis B (e.g. neonates born to hepatitis B carrier mothers and healthcare workers). The immunogenicity of Hep-B(Eng) was reduced in patients with conditions associated with impaired immune function (e.g. patients undergoing haemodialysis or being treated for malignancy), although it had good immunogenicity in patients with diabetes mellitus. Hep-B(Eng) had excellent protective efficacy against HBsAg carriage in healthy infants and children, and in neonates born to hepatitis B carrier mothers (protective efficacy of 95–99%). Hep-B(Eng) also demonstrated good protective efficacy in a number of other high-risk groups. Hep-B(Eng) is generally well tolerated with a tolerability profile similar to that of Hep-B(Rax), Hep-B(Bio) and PDVs. In conclusion, Hep-B(Eng) is a well established, highly immunogenic hepatitis B vaccine with good tolerability and excellent protective efficacy; it offers flexibility through a variety of immunisation schedules. In addition, it appears that Hep-B(Eng) confers immunity for at least 10 years. Hep-B(Eng) has an important role in mass vaccination campaigns against hepatitis B, as well as in groups considered at high risk of acquiring hepatitis B.

MF59-adjuvanted vaccines: increased immunogenicity with an optimal safety profile.

Abstract: The need to enhance the immunogenicity of purified subunit antigens has prompted the development of several new adjuvants. However, many of these new molecules have demonstrated a reactogenicity profile that is not suitable for their inclusion in vaccines for human use. In this context, the adjuvant emulsion MF59 has been developed, tested in combination with different antigens in several animal models and subsequently evaluated in humans. Clinical trials with several MF59-adjuvanted vaccines have been performed in different age groups (from newborns to the elderly) and have shown an increased immunogenicity of coadministered antigens, associated with a high level of safety and tolerability. MF59 has been the first adjuvant to be licensed for human use after alum and, as part of an enhanced influenza vaccine for the elderly, is now available in the marketplace of several countries worldwide.

Cellular Immune Responses to Human Papillomavirus (HPV)-16 L1 in Healthy Volunteers Immunized with Recombinant HPV-16 L1 Virus-Like Particles

Abstract: The causal association between papillomavirus (HPV) infection and cervical cancer has been demonstrated; the development of a prophylactic vaccine to protect against HPV infection may therefore reduce the incidence of this cancer worldwide Noninfectious HPV-like particles (VLPs), composed of the L1 major capsid protein, are current candidate vaccines for prevention of HPV infection and cervical neoplasia Although neutralizing antibodies have a pivotal role in the prevention of initial infection, cellular immune responses to HPV antigens may have an important role in viral clearance A phase II trial was conducted to further evaluate the immunogenicity of a recombinant HPV-16 L1 VLP vaccine administered intramuscularly, without adjuvant, at 0, 1, and 6 months Cell-mediated immune responses (lymphoproliferation and cytokine production) to HPV-16 L1 VLPs were evaluated in peripheral blood mononuclear cells (PBMCs) from 43 individuals receiving the L1 VLP vaccine and from 10 individuals receiving placebo Vaccination resulted, at months 2 and 7 (ie, 1 month after the second immunization and 1 month after third immunization, respectively), in increases in T cell-proliferative response to HPV-16 L1 VLPs (P<001) In addition, significant increases in cytokine (interferon-gamma, interleukin [IL]-5 and IL-10) responses to L1 VLPs were observed after vaccination (P<001) The strongest cytokine responses at month 7 were observed in individuals with high antibody titers at month 2, suggesting that neutralizing antibodies generated by initial vaccination may augment T cell responses to subsequent booster vaccinations No significant increases in lymphoproliferative or cytokine responses to L1 VLPs were observed in individuals receiving placebo In summary, the HPV-16 L1 vaccine induces not only robust B cell responses but also L1-specific T cell responses detectable by proliferation of both CD4+ and CD8+ T cells and in vitro production of both Th1- and Th2-type cytokines Future efficacy studies are needed to evaluate whether and/or how VLP vaccines confer protection against genital HPV infection and associated disease

Protection against Group A Streptococcus by Immunization with J8-Diphtheria Toxoid: Contribution of J8- and Diphtheria Toxoid-Specific Antibodies to Protection

Abstract: A conformationally constrained, minimally conserved peptide from the M protein of group A streptococcus (GAS) has been defined. It consists of 12 amino acids from the C-repeat region within a non-M protein helix-forming sequence and is referred to as "J8." Here, we investigate the immunogenicity of a J8-diphtheria toxoid (DT) conjugate adjuvanted with the human-compatible adjuvants, SBAS2 and alum, and demonstrate that it is capable of inducing opsonic antibodies and can protect outbred mice from virulent challenge. In a range of experiments, protection correlated with the titer of J8-specific antibodies and not with the induction of J8-specific T cells. However, DT-specific antibodies (as well as J8-specific antibodies) were shown to stain the surface of fixed GAS and to be capable of opsonizing live organisms. DT may be an ideal carrier protein for J8 and other GAS peptides for GAS vaccines.

An alphavirus replicon particle chimera derived from venezuelan equine encephalitis and sindbis viruses is a potent gene-based vaccine delivery vector.

Abstract: Alphavirus vectors are being developed as gene-based vaccines for infectious and malignant diseases (38, 42, 45). Alphavirus vectors are known as replicons due to the self-amplification of the vector RNA, which occurs in the cytoplasm of the infected cell. Replicons contain the nonstructural protein genes encoding the viral replicase, the 5′- and 3′-end cis-active replication sequences, and the native subgenomic promoter, which directs expression of the encoded heterologous gene(s). While replicons lack the genes encoding virion structural proteins necessary for packaging and cell-to-cell spread of infectious particles, they may be packaged into virus-like particles by providing the structural proteins in trans, using transient RNA cotransfection systems (2, 29) or stable replicon packaging cell lines (36). Alternatively, the replicon RNA can be introduced into cells as plasmid DNA (10, 18). Alphavirus replicon particle vectors have been developed using Sindbis virus (SIN) (2, 61), Venezuelan equine encephalitis virus (VEE) (40), and Semliki Forest virus (29). Each has been shown to induce robust cellular, humoral, and mucosal immune responses specific for the replicon-expressed antigen in several animal models (38, 42, 45). A number of features make alphavirus replicon vectors attractive for gene-based vaccines, including high-level expression of the heterologous gene (61), vector amplification through double-stranded RNA intermediates, which stimulates aspects of innate immunity, such as activation of the interferon (IFN) cascade (27), induction of apoptosis in some cell types (28) which may enhance immunogenicity via antigen cross-priming (62), and the overall lack of preexisting immunity in the human population. In addition, alphavirus replicon particles can be used for delivery of antigen to antigen-presenting cells, such as dendritic cells, the most potent antigen-presenting cell population (15, 31). On the basis of their biological niche, each alphavirus has unique properties, which may be either desirable or undesirable in terms of function, potency, and safety when applied to recombinant vector systems. For example, VEE has a natural lymphotropism (31) that may be ideal for vaccine use, and VEE replicon particles have been shown to induce potent and protective immune responses in primates (6, 19). The pathogenesis of wild-type VEE in humans (20), however, raises safety concerns, some of which have been addressed by identifying and incorporating specific attenuating mutations in the envelope glycoproteins of the replicon particles (40). However, despite these precautions, production of VEE replicon particles must be conducted at biosafety level III, and only after completion of testing for contaminating replication-competent virus can the particles be used at biosafety level II. In contrast, since SIN is not associated with serious human disease (20, 52), SIN-derived replicon particles largely obviate these concerns. In addition, particular engineered SIN variants target lymphoid cells (15), and stable replicon packaging cell lines have been developed (36), which may simplify large-scale production for human testing of vaccine candidates. However, although SIN vectors induce potent immune responses in murine models (38, 42, 46), little is known about whether this translates to robust immune responses in primates. Since the relative potencies of the different alphavirus vectors have not been characterized yet, we performed initial comparative immunogenicity studies for SIN and VEE replicon particles in this work. Also, we explored the feasibility of combining genetic components from each parent virus toward a goal of developing a chimeric alphavirus replicon particle with optimal potency and safety. For these studies, we generated a panel of SIN, VEE, and chimera replicon particles expressing a human immunodeficiency virus (HIV) p55gag antigen or green fluorescent protein (GFP) reporter. On the basis of in vitro and in vivo studies, we report here the identification of a novel VEE/SIN replicon particle chimera that combines selected desirable qualities of SIN and VEE, which should have utility as a potent gene-based vaccine delivery platform.

Immunogenicity of therapeutic proteins

Abstract: The use of proteins for medical applications has revolutionized therapies of many diseases/disorders that were often incurable with small-molecule medicines. However, since the first use of proteins as medicines, their immunogenicity has been a major problem. Over the years the quality and safety of therapeutic protein products have improved dramatically. Nevertheless, even the protein medicines of the newest generation may still cause adverse immunological events, posing a safety risk for patients and/or compromising their efficacy. Immunogenicity of therapeutic proteins is a complex, multifactorial phenomenon. In this chapter we summarize the current knowledge about immune mechanisms underlying the immunogenicity of therapeutic proteins and discuss influencing factors and clinical consequences of protein immunogenicity as well as strategies for immunogenicity assessment and mitigation.

Oral Immunogenicity of Human Papillomavirus-Like Particles Expressed in Potato

Abstract: Human papillomavirus-like particles (HPV VLPs) have shown considerable promise as a parenteral vaccine for the prevention of cervical cancer and its precursor lesions. Parenteral vaccines are expensive to produce and deliver, however, and therefore are not optimal for use in resource-poor settings, where most cervical HPV disease occurs. Transgenic plants expressing recombinant vaccine immunogens offer an attractive and potentially inexpensive alternative to vaccination by injection. For example, edible plants can be grown locally and can be distributed easily without special training or equipment. To assess the feasibility of an HPV VLP-based edible vaccine, in this study we synthesized a plant codon-optimized version of the HPV type 11 (HPV11) L1 major capsid protein coding sequence and introduced it into tobacco and potato. We show that full-length L1 protein is expressed and localized in plant cell nuclei and that expression of L1 in plants is enhanced by removal of the carboxy-terminal nuclear localization signal sequence. We also show that plant-expressed L1 self-assembles into VLPs with immunological properties comparable to those of native HPV virions. Importantly, ingestion of transgenic L1 potato was associated with activation of an anti-VLP immune response in mice that was qualitatively similar to that induced by VLP parenteral administration, and this response was enhanced significantly by subsequent oral boosting with purified insect cell-derived VLPs. Thus, papillomavirus L1 protein can be expressed in transgenic plants to form immunologically functional VLPs, and ingestion of such material can activate potentially protective humoral immune responses.

Purification, Characterization, and Immunogenicity of a Soluble Trimeric Envelope Protein Containing a Partial Deletion of the V2 Loop Derived from SF162, an R5-Tropic Human Immunodeficiency Virus Type 1 Isolate

Abstract: The envelope (Env) glycoprotein of human immunodeficiency virus type 1 (HIV-1) is the major target of neutralizing antibody responses and is likely to be a critical component of an effective vaccine against AIDS. Although monomeric HIV envelope subunit vaccines (gp120) have induced high-titer antibody responses and neutralizing antibodies against laboratory-adapted HIV-1 strains, they have failed to induce neutralizing antibodies against diverse heterologous primary HIV isolates. Most probably, the reason for this failure is that the antigenic structure(s) of these previously used immunogens does not mimic that of the functional HIV envelope, which is a trimer, and thus these immunogens do not elicit high titers of relevant functional antibodies. We recently reported that an Env glycoprotein immunogen (o-gp140SF162V2) containing a partial deletion in the second variable loop (V2) derived from the R5-tropic HIV-1 isolate SF162, when used in a DNA priming-protein boosting vaccine regimen in rhesus macaques, induced neutralizing antibodies against heterologous subtype B primary isolates as well as protection to the vaccinated animals upon challenge with pathogenic SHIVSF162P4 virus. Here we describe the purification of this protein to homogeneity, its characterization as trimer, and its ability to induce primary isolate-neutralizing responses in rhesus macaques. Optimal mutations in the primary and secondary protease cleavage sites of the env gene were identified that resulted in the stable secretion of a trimeric Env glycoprotein in mammalian cell cultures. We determined the molecular mass and hydrodynamic radius (Rh) using a triple detector analysis (TDA) system. The molecular mass of the oligomer was found to be 324 kDa, close to the expected Mw of a HIV envelope trimer protein (330 kDa), and the hydrodynamic radius was 7.27 nm. Negative staining electron microscopy of o-gp140SF162V2 showed that it is a trimer with considerable structural flexibility and supported the data obtained by TDA. The structural integrity of the purified trimeric protein was also confirmed by determinations of its ability to bind the HIV receptor, CD4, and its ability to bind a panel of well-characterized neutralizing monoclonal antibodies. No deleterious effect of V2 loop deletion was observed on the structure and conformation of the protein, and several critical neutralization epitopes were preserved and well exposed on the purified o-gp140SF162V2 protein. In an intranasal priming and intramuscular boosting regimen, this protein induced high titers of functional antibodies, which neutralized the vaccine strain, i.e., SF162. These results highlight a potential role for the trimeric o-gp140SF162V2 Env immunogen in a successful HIV vaccine. AIDS continues to be a major health problem throughout the world, with approximately 40 million cases and 4 million deaths having been recorded so far. In certain parts of the world, nearly 30% of the total population is infected with human immunodeficiency virus (HIV). An estimated 40,000 to 80,000 primary infections occur each year in the United States alone. The situation is deteriorating as a result of rapid emergence of drug resistance against most of the effective antivirals. Therefore, there is an urgent need for an effective anti-HIV vaccine that may be used alone for protection or in conjunction with effective antivirals for treatment. HIV Env glycoprotein is the major target of neutralizing antibody responses and thus will be an important component

Identification of vaccinia virus epitope-specific HLA-A*0201-restricted T cells and comparative analysis of smallpox vaccines.

Abstract: Despite worldwide eradication of naturally occurring variola virus, smallpox remains a potential threat to both civilian and military populations. New, safe smallpox vaccines are being developed, and there is an urgent need for methods to evaluate vaccine efficacy after immunization. Here we report the identification of an immunodominant HLA-A*0201-restricted epitope that is recognized by cytotoxic CD8+ T cells and conserved among Orthopoxvirus species including variola virus. This finding has permitted analysis and monitoring of epitope-specific T cell responses after immunization and demonstration of the identified T cell specificity in an A*0201-positive human donor. Vaccination of transgenic mice allowed us to compare the immunogenicity of several vaccinia viruses including highly attenuated, replication-deficient modified vaccinia virus Ankara (MVA). MVA vaccines elicited levels of CD8+ T cell responses that were comparable to those induced by the replication-competent vaccinia virus strains. Finally, we demonstrate that MVA vaccination is fully protective against a lethal respiratory challenge with virulent vaccinia virus strain Western Reserve. Our data provide a basis to rationally estimate immunogenicity of safe, second-generation poxvirus vaccines and suggest that MVA may be a suitable candidate.

Role of alpha/beta interferons in the attenuation and immunogenicity of recombinant bovine respiratory syncytial viruses lacking NS proteins.

Abstract: Alpha/beta interferons (IFN-α/β) are not only a powerful first line of defense against pathogens but also have potent immunomodulatory activities. Many viruses have developed mechanisms of subverting the IFN system to enhance their virulence. Previous studies have demonstrated that the nonstructural (NS) genes of bovine respiratory syncytial virus (BRSV) counteract the antiviral effects of IFN-α/β. Here we demonstrate that, in contrast to wild-type BRSVs, recombinant BRSVs (rBRSVs) lacking the NS proteins, and those lacking NS2 in particular, are strong inducers of IFN-α/β in bovine nasal fibroblasts and bronchoalveolar macrophages. Furthermore, whereas the NS deletion mutants replicated to wild-type rBRSV levels in cells lacking a functional IFN-α/β system, their replication was severely attenuated in IFN-competent cells and in young calves. These results suggest that the NS proteins block the induction of IFN-α/β gene expression and thereby increase the virulence of BRSV. Despite their poor replication in the respiratory tract of young calves, prior infection with virus lacking either the NS1 or the NS2 protein induced serum antibodies and protection against challenge with virulent BRSV. The greater level of protection induced by the NS2, than by the NS1, deletion mutant, was associated with higher BRSV-specific antibody titers and greater priming of BRSV-specific, IFN-γ-producing CD4+ T cells. Since there were no detectable differences in the ability of these mutants to replicate in the bovine respiratory tract, the greater immunogenicity of the NS2 deletion mutant may be associated with the greater ability of this virus to induce IFN-α/β.

Immunization with hepatitis C virus-like particles protects mice from recombinant hepatitis C virus-vaccinia infection

Abstract: We have recently demonstrated that immunization with hepatitis C virus-like particles (HCV-LPs) generated in insect cells can elicit both humoral and cellular immune responses in BALB/c mice. Here, we evaluate the immunogenicity of HCV-LPs in HLA2.1 transgenic (AAD) mice in comparison to DNA immunization. HCV-LP immunization elicited a significantly stronger humoral immune response than DNA immunization. HCV-LP-immunized mice also developed stronger HCV-specific cellular immune responses than DNA-immunized mice as determined by using quantitative enzyme-linked immunospot (ELISpot) assay and intracellular cytokine staining. In BALB/c mice, immunization with HCV-LPs resulted in a >5 log10 reduction in vaccinia titer when challenged with a recombinant vaccinia expressing the HCV structural proteins (vvHCV.S), as compared to 1 log10 decrease in DNA immunization. In HLA2.1 transgenic mice, a 1-2 log10 reduction resulted from HCV-LP immunization, whereas no reduction was seen from DNA immunization. Adoptive transfer of lymphocytes from HCV-LP-immunized mice to naive mice provided protection against vvHCV.S challenge, and this transferred immunity can be abrogated by either CD4 or CD8 depletion. Our results suggest that HCV-LPs can induce humoral and cellular immune responses that are protective in a surrogate HCV challenge model and that a strong cellular immunity provided by both CD4 and CD8 effector lymphocytes may be important for protection from HCV infection.

A molecularly cloned Schwarz strain of measles virus vaccine induces strong immune responses in macaques and transgenic mice.

Abstract: Live attenuated RNA viruses make highly efficient vaccines. Among them, measles virus (MV) vaccine has been given to a very large number of children and has been shown to be highly efficacious and safe. Therefore, this vaccine might be a very promising vector to immunize children against both measles and other infectious agents, such as human immunodeficiency virus. A vector was previously derived from the Edmonston B strain of MV, a vaccine strain abandoned 25 years ago. Sequence analysis revealed that the genome of this vector diverges from Edmonston B by 10 amino acid substitutions not related to any Edmonston subgroup. Here we describe an infectious cDNA for the Schwarz/Moraten strain, a widely used MV vaccine. This cDNA was constructed from a batch of commercial vaccine. The extremities of the cDNA were engineered in order to maximize virus yield during rescue. A previously described helper cell-based rescue system was adapted by cocultivating transfected cells on primary chicken embryo fibroblasts, the cells used to produce the Schwarz/Moraten vaccine. After two passages the sequence of the rescued virus was identical to that of the cDNA and of the published Schwarz/Moraten sequence. Two additional transcription units were introduced in the cDNA for cloning foreign genetic material. The immunogenicity of rescued virus was studied in macaques and in mice transgenic for the CD46 MV receptor. Antibody titers and T-cell responses (ELISpot) in animals inoculated with low doses of rescued virus were identical to those obtained with commercial Schwarz MV vaccine. In contrast, the immunogenicity of the previously described Edmonston B strain-derived MV clone was much lower. This new molecular clone will allow for the production of MV vaccine without having to rely on seed stocks. The additional transcription units allow expressing heterologous antigens, thereby providing polyvalent vaccines based on an approved, safe, and efficient MV vaccine strain that is used worldwide.

Naturally occurring B-cell responses to breast cancer.

Abstract: As demonstrated by the effectiveness of trastuzumab, antibodies against breast cancer antigens are a potentially potent mechanism of tumor control. While trastuzumab is administered exogenously, its efficacy suggests that induction of very high titer antibody responses in vivo might also be therapeutic. Both naturally occurring and vaccine-induced antibody responses to some breast cancer antigens are associated with improved survival in some cases. However, the improvement in survival associated with antibody responses to breast cancer is modest, and tumor regression is not known to be associated with the natural antitumor antibody response, indicating a need for improved understanding of the natural antitumor antibody response. Naturally occurring B-cell responses in the form of serum antibody, tumor reactive lymph node B cells, and tumor-infiltrating B cells have been described, and a variety of breast tumor-associated antigens have been identified based on reactivity of patient antibodies. This review discusses current knowledge of humoral immunity to breast cancer with regard to specific antigens and the basis for their immunogenicity, and the contexts (tumor, lymph node, serum) in which responses are observed. With few exceptions, "tumor-associated antigens" identified with naturally occurring antibodies may be overexpressed on tumor but are in fact nonspecific autoantigens. This suggests that while overexpression or aberrant processing can increase immunogenicity in some cases, the immunogenicity of many or even most tumor-associated antigens is a function of expression in tumor or the result of ancillary tumor factors.

Immunogenicity of therapeutic monoclonal antibodies.

Abstract: There are currently 13 monoclonal antibodies or antibody constructs approved for therapeutic use in the US and at least another 400 products are in clinical testing or undergoing regulatory review. Despite widespread use and development of therapeutic monoclonal antibodies, limited information exists regarding the incidence and consequence of immune antibodies generated against many of these products. In this review, analytical methodology and recent data on the immunogenicity of approved therapeutic monoclonal antibodies will be presented. The implications of these findings in relation to potential concerns for repeated or chronic treatment with these powerful and specific therapeutic agents will be discussed.

A plant signal peptide–hepatitis B surface antigen fusion protein with enhanced stability and immunogenicity expressed in plant cells

Abstract: The use of transgenic plants to express orally immunogenic protein antigens is an emerging strategy for vaccine biomanufacturing and delivery. This concept has particular suitability for developing countries. One factor that has limited the development of this technology is the relatively modest levels of accumulation of some antigenic proteins in plant tissues. We used fusion protein design to improve expression of the hepatitis B surface antigen (HBsAg) by attempting to mimic the process of HBsAg targeting to the endoplasmic reticulum of human liver cells during hepatitis B virus infection. We created a gene encoding a recombinant HBsAg modified to contain a plant signal peptide fused to its amino terminus. The signal peptide from soybean vegetative storage protein vspA (VSPαS) directed endoplasmic reticulum targeting of HBsAg in plant cells, but was not cleaved and resulted in enhanced VSPαS-HBsAg fusion accumulation. This product was more stable and presented the protective “a” antigenic determinant to significantly higher levels than unmodified native HBsAg expressed in plant cells. It also showed a greater extent of intermolecular disulfide bond formation and formation of virus-like particles. Moreover, VSPαS-HBsAg stimulated higher levels of serum IgG than native HBsAg when injected into mice. We conclude that HBsAg tolerates a polypeptide fusion at the amino terminus and that VSPαS-HBsAg is an improved antigen for plant-based expression of a subunit vaccine for hepatitis B virus.

Group B streptococcal conjugate vaccines

Abstract: Linkage of bacterial capsular polysaccharides to proteins to create conjugate vaccines has had a dramatic impact on the health of children. Although unconjugated polysaccharides are poorly immunogenic in infants and some older children and adults, their covalent coupling with proteins stimulates T cell dependent antigenic recognition that profoundly enhances immunogenicity. In the decade since the introduction and widespread use of Haemophilus influenzae type b polysaccharide conjugate vaccines in the United States, invasive H influenzae infections have become a rarity in childhood. Similarly, the conjugation of polysaccharides of Streptococcus pneumoniae to a derivative of diphtheria toxoid and the addition of pneumococcal conjugate vaccine to infant immunisation schedules carries with it promise for a similar decline in the incidence of invasive pneumococcal disease in paediatric patients.

A new MF59-adjuvanted influenza vaccine enhances the immune response in the elderly with chronic diseases: results from an immunogenicity meta-analysis.

Abstract: Background: The elderly are at a higher risk of morbidity and mortality associated with influenza infection than younger adults, but get less protection from conventional vaccination Objective: We conducted a meta-analysis of all available data from clinical trials in the elderly on a recently introduced MF59-adjuvanted influenza vaccine to determine its immunogenicity and safety in subjects with underlying chronic disease who are at highest risk of influenza infection Methods: Data on immunogenicity and safety from 3,600 subjects immunized with either the MF59-adjuvanted or conventional comparator influenza vaccine in 13 clinical trials were analyzed by disease history Geometric mean haemagglutination inhibition titres (GMTs) and differences between the vaccine groups were compared using two-way analysis of variance Differences between vaccine groups in the percentages with post-immunization reactions were assessed using chi-squared test and Fischer’s exact test Results: At 28 days the adjuvanted:comparator GMT ratio for the A/H3N2 antigen was 118 in healthy elderly subjects and 143 in elderly subjects with chronic disease (p = 0004) The respective GMT ratios were 117 versus 137 for the B antigen (p = 0065) and 110 versus 117 for the A/H1N1 antigen (p = 041) Although post-immunization reactions were more common in the group receiving the adjuvanted vaccine, these were predominantly mild and transient, and none were serious Conclusions: The MF59-adjuvanted influenza vaccine is more immunogenic in elderly subjects than conventional non-adjuvanted influenza vaccines and especially so in those with chronic disease Therefore, since its safety profile is clinically acceptable, this adjuvanted vaccine represents an excellent option for influenza immunization of elderly subjects at highest risk of complications

Immunomic analysis of human sarcoma

Abstract: The screening of cDNA expression libraries from human tumors with serum antibody (SEREX) has proven to be a powerful method for identifying the repertoire of tumor antigens recognized by the immune system of cancer patients, referred to as the cancer immunome. In this regard, cancer/testis (CT) antigens are of particular interest because of their immunogenicity and restricted expression patterns. Synoivial sarcomas are striking with regard to CT antigen expression, with >80% of specimens homogeneously expressing NY-ESO-1 and MAGE-A3. In the present study, 54 sarcoma patients were tested for serum antibodies to NY-ESO-1, SSX2, MAGE-A1, MAGE-A3, MAGE-A4, MAGE-A10, CT7, and CT10. Two patients had detectable antibodies to CT antigens, and this seroreactivity was restricted to NY-ESO-1. Thus, although highly expressed in sarcoma, CT antigens do not induce frequent humoral immune responses in sarcoma patients. Sera from these two patients were used to immunoscreen cDNA libraries from two synovial sarcoma cell lines and normal testis, resulting in the identification of 113 distinct antigens. Thirty-nine antigens were previously identified by SEREX analysis of other tumor types, and 23/39 antigens (59%) had a serological profile that was not restricted to cancer patients, indicating that only a proportion of SEREX-defined antigens are cancer-related. A novel CT antigen, NY-SAR-35, mapping to chromosome Xq28 was identified among the cancer-related antigens, and encodes a putative extracellular protein. In addition to testis-restricted expression, NY-SAR-35 mRNA was expressed in sarcoma, melanoma, esophageal cancer, lung cancer and breast cancer. NY-SAR-35 is therefore a potential target for cancer vaccines and monoclonal antibody-based immunotherapies.