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PubMed1990

New approaches in viral vaccine development.

With the exception of the vaccine against hepatitis B the principles involved in the production of the viral vaccines in use today have not changed since Jenner (1) first developed the vaccine which was so important in the control and eventual eradication of smallpox in 1977. All have relied on the presentation of the live attenuated or inactivated virus to the host, either orally or by injection, so that it elicited the formation of antibody and primed memory cells for a rapid response to the subsequent invasion of the virus. With the discovery that protective immunity could be obtained with isolated individual proteins from virus particles and the development of methods for the expression of these proteins, both in vivo and in vitro, there is now considerable promise that immunity can be induced without the need to use the disease agent itself. Moreover, the molecular basis of the immune response is now beginning to be understood, thus allowing a more rational approach to the design of vaccines for individual diseases.

Administration, Oral↗

PubMedDate not supplied

Derivation, safety and efficacy of a Marek's disease vaccine developed from an Australian isolate of very virulent Marek's disease virus.

OBJECTIVE: To develop a serotype 1 Marek's disease (MD) vaccine from a very virulent MDV (vvMDV) pathotype and demonstrate safety and efficacy against early challenge with very virulent field strains in the presence of maternal antibody. STUDY DESIGN: Strain BH 16 was isolated and attenuated by serial cell culture passage. One of two cloned passages was selected for vaccine development following early laboratory-scale protection trials in commercial birds. Comparative protection trials were carded out on the BH 16 vaccine and on a CVI 988 Rispens vaccine using commercial and SPF chickens. Challenge viruses used were either a low passage strain BH 16 virus, the Woodlands No. 1 strain or MPF 57 strain of MDV. The BH 16 vaccine was back-passaged in SPF chickens six times and virus recovered from the final passage and the original vaccine virus were tested for safety. The immunosuppressive potential of the BH 16 and Rispens vaccines was also assessed in parallel. RESULTS: The BH 16 and Rispens vaccines induced comparable levels of protection when used as monovalent or multivalent vaccines, although protection achieved with the monovalent vaccines was lower. No gross tumour formation was evident in any birds receiving the BH 16 vaccine or bird-passaged virus, although microscopic lesions were present in 2/12 birds that received the bird-passaged virus. In tests for immunosuppression, there was no histological evidence of damage to either the bursa of Fabricius or the thymus. CONCLUSION: The BH 16 vaccine was shown to be safe and at least as protective as the Rispens vaccine against three highly virulent MD challenge viruses.

Animals↗

PubMed1993

Induction and assessment of immunity at enteromucosal surfaces in humans: implications for vaccine development.

It is now almost axiomatic that vaccines against enteric infections must be able to stimulate the gut lymphoid tissue to be efficacious and that this goal is usually better achieved by administering immunogens orally rather than parenterally. On the basis of the notion of a common mucosal immunologic system that provides immune reactivity not only at the site of antigen deposition but also at remote mucosal sites, there is much interest in developing oral vaccines against infections in the respiratory and urogenital tracts. Recent studies indicate that oral administration of small amounts of protein antigens that are chemically or genetically linked to intestinal binding carrier molecules (such as the B subunit of cholera toxin) can evoke vigorous mucosal and extramucosal immune responses. The apparent compartmentalization of systemic and mucosal immune responses may explain not only why parenteral vaccines are just partly effective in protecting against mucosal pathogens but also why currently employed immunoanalytical methods do not provide accurate information regarding mucosal immune status. Following the developments of oral vaccines against infections due to Vibrio cholerae and enterotoxigenic Escherichia coli, two archetypes of enteropathogens, we have devoted extensive efforts to gaining insight into the humoral and cellular events involved in the development of protective immunity in the human intestinal tract. We have developed preparative and analytical methods for studying vaccine-induced intestinal and extraintestinal immune responses in humans. These include techniques for collecting intestinal fluid and lymphoid cells as well as procedures to quantitate secretory antibodies and lymphokines secreted by activated intestinal immunocytes. These developments should serve the dual purpose of facilitating analyses of human mucosal immune responses in general and assessing the immunogenicity of enteric vaccines in particular.

Administration, Oral↗

PubMed2000

HIV vaccine development at Duke University Medical Center.

With the AIDS epidemic continuing to spread throughout the world, development of a safe, practical, and effective HIV vaccine is a national priority. HIV vaccine research efforts are currently targeted towards design of HIV immunogens that induce both cellular and humoral immunity. This brief review summarizes ongoing work at the Duke University School of Medicine on HIV vaccine development.

AIDS Vaccines↗

PubMed2005

Helicobacter pylori vaccine development: facing the challenge.

An effective vaccine would be a desirable way to control Helicobacter pylori-induced gastric disease. Initial studies in animal models demonstrated the feasibility of immunization and led to high hopes for a human vaccine. In the mouse model immunological approaches have to date not brought a satisfactory explanation for the mechanisms of protection against this largely luminal pathogen. Recently, transcriptome studies have identified new factors. It is now proposed that non-classical immune mediators may be the key to vaccine-induced protection. Human trials of H. pylori vaccines are going ahead but although at least some formulations are clearly immunogenic, their effectiveness remains untested. The recent development of a human challenge model has now opened up new prospects for testing candidate vaccines and this will undoubtedly have a great impact in the near future. Future priorities for H. pylori vaccine development must be a better understanding of the protective mechanisms and the identification of biomarkers which can be used as reliable predictors of efficacy in humans. Despite some important advances in recent years, important issues must be resolved before an H. pylori vaccine will become a reality.

Adjuvants, Immunologic↗

PubMed2004

The development of effector and memory T cells in cutaneous leishmaniasis: the implications for vaccine development.

Leishmania major infections induce the development of a CD4(+) T-helper 1 (Th1) response that not only controls the primary infection but also results in life-long immunity to reinfection. How that immunity is maintained is unknown, although because of the existence of infection-induced immunity, there has been an assumption that the development of a vaccine against leishmaniasis would be relatively easy. This has turned out not to be the case. One problem has been the finding that a large part of the immunity induced by a primary infection depends upon the presence of persistent parasites. Nevertheless, there are ample situations where immunologic memory persists without the continued presence of antigen, providing the prospect that a non-live vaccine for leishmaniasis can be developed. To do so will require an understanding of the events involved in the development of an effective protective T-cell response and, more importantly, an understanding of how to maintain that response. Here, we review work from our laboratory, describing how Th1 cells develop in L. major-infected mice, the nature of the memory T cells that provide protection to reinfection, and how that information may be utilized in the development of vaccines.

Animals↗

PubMed1997

Current status of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) vaccine development: memorandum from a joint WHO/NIAID meeting.

A Joint WHO/National Institute of Allergy and Infectious Diseases (NIAID) meeting on the current status of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) vaccine development was held in Bethesda, MD, from 30 September to 1 October 1996. The meeting summarized the worldwide impact of RSV and PIV3; presented the current status of development of RSV and PIV3 vaccines; and examined the applications of recombinant DNA technology to the development and characterization of vaccines and to the understanding of viral pathogenesis.

Adult↗

PubMed1989

Strategies for developing vaccines against acquired immunodeficiency syndrome.

There exists an abundance of literature on the prospects for developing vaccines against the etiologic viral agent of acquired immunodeficiency syndrome (AIDS). Excellent reviews from a variety of investigators are available on this subject. It is our intention to review the literature relative to potential strategies for developing a successful AIDS vaccine and to impart some of our concerns on the different types of vaccine that are being tested. We have also focused on some vaccine strategies that have not received much attention in previous review articles. Finally, the role of animal models in assessing vaccine safety and efficacy against AIDS has been briefly described.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Influence of intron and exon splicing enhancers on mammalian cell expression of a truncated spike protein of SARS-CoV and its implication for subunit vaccine development.

The spike (S) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) is important for vaccine development. A truncated S protein of the TW1 strain, STR2 (88 kDa), carrying three S fragments (S74-253, S294-739, and S1129-1255) was investigated to study the influences of intron and exon splicing enhancers to improve STR2 protein expression in mammalian cells. Our results showed that STR2 protein expression with the use of an 138 base-pair intron addition increased by 1.9-, 2.5-, and 4.1-fold in Vero E6, QBI-293A cells, and CHO/dhFr- cells (dihydrofolate reductase [dhfr] gene deficient CHO cells), respectively. Using the exon splicing enhancers, including a bidirectional splicing enhancer (BSE) or an exon splicing enhancer derived from the EDA alternative exon of the fibronectin gene (EDA ESE), were also found to increase STR2 protein expression in CHO/dhFr- cells by 1.7- and 2.6-fold. Nevertheless, combination of the intron and the exon splicing enhancers resulted in suppressing the intron-enhancing e STR2 protein expression in in CHO/dhFr- cells. Our studies also demonstrated the STR2 protein was mainly as the Endo H-sensitive glycoprotein (115 kDa) expressed in Vero E6, QBI-293A, and CHO/dhFr- cells. However, only a minor form of the Endo H-resistant glycoproteins ( approximately 130 kDa) was detected in CHO/dhFr- cells. Taken together, our results indicated that intron had a better enhancing effect on STR2 protein expression than exon splicing enhancers, and the expression of approximately 130 kDa STR2 glycoprotein was enhanced by the intron addition into the expression vector construct. Results of the present study can provide an optimal strategy to enhance SARS-CoV S protein expression in mammalian cells and may contribute to the development of SARS-CoV subunit vaccine.

Animals↗

PubMed1995

Molecular basis for vaccine development against anaplasmosis and babesiosis.

Immunization of livestock against the erythroparasitic pathogens Anaplasma marginale, Babesia bigemina, and Babesia bovis with safe and effective killed vaccines is not yet feasible on a practical basis. However, the immune protection afforded by recovery from natural infection and premunition indicates that microbial epitopes capable of inducing immunity exist and that the bovine immune system can be primed appropriately. Induction of protection by immunization with killed parasite fractions, enriched for polypeptides with surface exposed epitopes, supports a focus on surface epitopes, including apical complex organellar epitopes in Babesia, for vaccine development. Cloning, sequencing, and expression of genes encoding these key surface polypeptides has allowed examination of polypeptide function and detailed analysis of epitope conservation in light of genetic polymorphism. In this paper, the characterization of these polypeptides at the epitope level and their roles in inducing protective immunity are reviewed. Definition of these epitopes, in combination with improved understanding of immune mechanisms, provides the basis for development of effective recombinant vaccines against anaplasmosis and babesiosis.

Anaplasma↗

PubMed2002

FIV vaccine development and its importance to veterinary and human medicine: a review FIV vaccine 2002 update and review.

Feline immunodeficiency virus (FIV) is a natural infection of domestic cats that results in acquired immunodeficiency syndrome resembling human immunodeficiency virus (HIV) infection in humans. The worldwide prevalence of FIV infection in domestic cats has been reported to range from 1 to 28%. Hence, an effective FIV vaccine will have an important impact on veterinary medicine in addition to being used as a small animal AIDS model for humans. Since the discovery of FIV reported in 1987, FIV vaccine research has pursued both molecular and conventional vaccine approaches toward the development of a commercial product. Published FIV vaccine trial results from 1998 to the present have been compiled to update the veterinary clinical and research communities on the immunologic and experimental efficacy status of these vaccines. A brief report is included on the outcome of the 10 years of collaborative work between industry and academia which led to recent USDA approval of the first animal lentivirus vaccine, the dual-subtype FIV vaccine. The immunogenicity and efficacy of the experimental prototype, dual-subtype FIV vaccine and the efficacy of the currently approved commercial, dual-subtype FIV vaccine (Fel-O-Vax FIV) are discussed. Potential cross-reactivity complications between commercial FIV diagnostic tests, Idexx Snap Combo Test and Western blot assays, and sera from previously vaccinated cats are also discussed. Finally, recommendations are made for unbiased critical testing of new FIV vaccines, the currently USDA approved vaccine, and future vaccines in development.

AIDS Vaccines↗

PubMed2002

How the research-based industry approaches vaccine development and establishes priorities.

Over the past two decades, progress in immunology, molecular biology and genomics as well as some technological breakthroughs in computer science has opened the way to the development of prophylactic vaccines against most acute infectious diseases. Therapeutic vaccines against chronic infections, allergic conditions, auto-immune diseases and cancer have also come into the realm of possibility. It is estimated that wordwide there are about 400 vaccine projects in R&D laboratories of academic institutions, research institutes and vaccine manufacturers. Most of these projects will not yield a licensed vaccine for routine or even targeted immunisation. This is mostly not because of scientific barriers but due to financial and politicoeconomic obstades that make their development feasible only by the handful of major research-based vaccine manufacturers that nowadays all form part of large global pharmaceutical corporations. Such enterprises have to be profitable to survive and priority setting, when it comes to R&D projects, has to take into account potential return on all investments, particularly as it currently costs between 200 and 500 million US dollars to bring a new vaccine from the concept stage to market. Factors that influence the decision to embark upon an R&D project on a new vaccine include the medical need for the vaccine, gauged by the global burden of the targeted disease, potential and probable market size - judged on volume (number of doses required) and value (total sales) -, probability of success and expertise of the company in the field (both R&D and marketing) as well as the likelihood of competitors taking a large part of the market. Moral imperatives such as the urgent need for vaccines against HIV/AIDS, malaria and an improved vaccine against tuberculosis to save the several millions of lives claimed each year by these diseases also play a role. However, for such investments to be sustainable other sources of financing than the commercial market will be required.

Cost of Illness↗

PubMed2003

Characterization and selection of HIV-1 subtype C isolates for use in vaccine development.

HIV-1 genetic diversity among circulating strains presents a major challenge for HIV-1 vaccine development, particularly for developing countries where less sequence information is available. To identify representative viruses for inclusion in candidate vaccines targeted for South Africa, we applied an efficient sequence survey strategy to samples from recently and chronically infected persons residing in potential vaccine trial sites. All 111 sequences were subtype C, including 30 partial gag, 26 partial pol, 27 V2-V3 env, and 28 V5-partial gp41 sequences. Of the 10 viruses cultured from recently infected individuals, 9 were R5 and 1 was R5X4. Two isolates, Du151 and Du422, collected within 2 months of infection, were selected as vaccine strains on the basis of their amino acid similarity to a derived South African consensus sequence The selection of recently transmitted R5 isolates for vaccine design may provide an advantage in a subtype C R5-dominant epidemic. The full-length Du422 gag and Du151 pol and env genes were cloned into the Venezuelan equine encephalitis (VEE) replicon particle (VRP) expression system. Du422 Gag protein expressed from the VRP accumulated to a high level and was immunogenic as demonstrated by cytotoxic T lymphocyte responses in mice vaccinated with gag-VRPs. Optimization of codon use for VRP expression in human cells did not enhance expression of the gag gene. The cloned Du151 env gene encoded a functional protein as demonstrated by fusion of VRP-infected cells with cells expressing CD4 and CCR5. Genes identified in this study have been incorporated into the VEE VRP candidate vaccines targeted for clinical trial in South Africa.

AIDS Vaccines↗

PubMed2004

Pneumococcal vaccine development.

A 7-valent pneumococcal conjugate vaccine has demonstrated an impact on pneumococcal bacteremia in the immunized pediatric population, extending to nonimmunized adults via herd immunity. A considerable reduction of all-cause pediatric pneumonia has also been found. The impact on all-cause pediatric otitis is limited, but postlicensure data suggests stronger reductions. Higher valency conjugate vaccines are now under development (11V or more). Licensed 23-valent pneumococcal polysaccharide vaccines have been available since 1983 with a demonstrated impact on adult pneumococcal bacteremia. The burden of adult nonbacteremic pneumococcal pneumonia has remained high and efforts to develop improved adult pneumococcal vaccines have been initiated that include conjugates and pneumococcal proteins.

Adult↗

PubMed1998

Malaria vaccine development: current status.

The development of an effective malaria vaccine represents one of the most important approaches that would provide a cost-effective intervention for addition to currently available malaria control strategies. Here, Howard Engers and Tore Godal review recent advances. Over the past decade there has been considerable progress in the understanding of immune mechanisms involved in conferring protection to malaria and in the identification of vaccine candidate antigens and their genes. Several new vaccines have entered Phase I/II trials recently, new adjuvants have been developed for human use and new approaches, such as DNA vaccines and structural modification of antigens to circumvent some of the strategies the parasite uses to avoid the immune response, are being applied. Thus, from the TDR perspective, global malaria vaccine development is entering a crucial period with unprecedented opportunities.

Journal Article↗

PubMedDate not supplied

Synthetic peptide vaccine development: measurement of polyclonal antibody affinity and cross-reactivity using a new peptide capture and release system for surface plasmon resonance spectroscopy.

A method has been developed for measurement of antibody affinity and cross-reactivity by surface plasmon resonance spectroscopy using the EK-coil heterodimeric coiled-coil peptide capture system. This system allows for reversible capture of synthetic peptide ligands on a biosensor chip surface, with the advantage that multiple antibody-antigen interactions can be analyzed using a single biosensor chip. This method has proven useful in the development of a synthetic peptide anti-Pseudomonas aeruginosa (PA) vaccine. Synthetic peptide ligands corresponding to the receptor binding domains of pilin from four strains of PA were conjugated to the E-coil strand of the heterodimeric coiled-coil domain and individually captured on the biosensor chip through dimerization with the immobilized K-coil strand. Polyclonal rabbit IgG raised against pilin epitopes was injected over the sensor chip surface for kinetic analysis of the antigen-antibody interaction. The kinetic rate constants, k(on) and k(off), and equilibrium association and dissociation constants, KA and KD, were calculated. Antibody affinities ranged from 1.14 x 10(-9) to 1.60 x 10(-5) M. The results suggest that the carrier protein and adjuvant used during immunization make a dramatic difference in antibody affinity and cross-reactivity. Antibodies raised against the PA strain K pilin epitope conjugated to keyhole limpet haemocyanin using Freund's adjuvant system were more broadly cross-reactive than antibodies raised against the same epitope conjugated to tetanus toxoid using Adjuvax adjuvant. The method described here is useful for detailed characterization of the interaction of polyclonal antibodies with a panel of synthetic peptide ligands with the objective of obtaining high affinity and cross-reactive antibodies in vaccine development.

Amino Acid Sequence↗

PubMed1998

Maturation of immune responses to lentivirus infection: implications for AIDS vaccine development.

The evaluation of attenuated vaccines in the simian immunodeficiency virus and equine infectious anemia virus animal models has demonstrated the ability of this immunization strategy to elicit broad and enduring immune protection from virus exposure. The development of protective immunity by these attenuated virus vaccines, however, has been shown to be time dependent and to be associated with a complex and lengthy maturation of immune responses over the first 6 to 8 months postinoculation. During this time period, envelope-specific antibody responses undergo an evolution in quantitative and qualitative properties that is similar, but distinct for each lentivirus system. The completed maturation of immune responses is then characterized by relatively steady-state antibody responses that are maintained indefinitely. The accomplishment of optimum vaccine protection is associated with achievement of a fully mature immune response, whereas nonprotective or enhancing vaccine immunity appears to be associated with immature immune responses elicited by ineffective vaccines. These observations indicate that the development of an effective acquired immunodeficiency syndrome (AIDS) vaccine will require immunization strategies that can achieve the necessary maturation of immune responses to human immunodeficiency virus type 1 (HIV-1) antigens in the minimum amount of time. Therefore, AIDS vaccine strategies based on attenuated live virus vaccines or on DNA immunization procedures, perhaps in conjunction with cytokine or secondary costimulatory molecules to accelerate immune maturation, may be best suited to accomplish the goal of an effective and practical AIDS vaccine for worldwide use.

AIDS Vaccines↗

PubMed2002

Lymphoid activation: a confounding factor in AIDS vaccine development?

In a previous vaccination trial, inoculation of env gene DNA failed to elicit a detectable antibody response, yet accelerated virus dissemination in most immunized cats following challenge with feline immunodeficiency virus. This result raised the possibility that cell-mediated immune responses had given rise to immune-mediated enhancement of infection. Since high-level replication of immunodeficiency viruses in lymphocytes requires cellular activation, antigen-specific responses or non-specific polyclonal activation may have increased the frequency of optimal target cells. In the present DNA vaccination trial, although designed so as to minimize non-specific polyclonal activation, immune-mediated enhancement was nonetheless observed in certain immunized cats. Moreover, rapid virus dissemination in vivo was associated with the presence of T-helper responses prior to challenge, and was linked to increased susceptibility of lymphocytes to ex vivo infection. Immune activation may thus be a confounding factor in vaccination against lentivirus infection, diminishing vaccine efficacy and giving rise to immune-mediated enhancement.

Animals↗