Study of allergic reactions in the body after experimental smallpox vaccination

Experiments on guinea pigs demonstrated a mixed cellular-humoral character of allergy in smallpox vaccination. The ratio of cellular and humoral components depended on the site of the vaccina application. Skin manifestations in smallpox vaccination (hyperemia, infiltration, papula) were due to the multiplication of the virus proper, increased sensitivity of the surrounding tissues to the live vibrio, and specific immunological reconstruction. The skin of the sensitized animal after the anaphylactic shock in response to the intracardiac injection of the challenging dose of the vaccine virus acquired areactivity to its subsequent application.     

Vaccine regulations in Croatia

In this paper legal prerequisites for vaccine licensure in Croatia are discussed. The Croatian legislation concerning vaccine licensing, marketing authorisation and utilization is reviewed. The procedures for including a vaccine into the Mandatory Childhood Vaccination Programme are also discussed with focus on Human papillomavirus (HPV) vaccines. Non-obligatory vaccination recommendations are given when according to professional opinion; vaccination is beneficial for the vaccinee. There is little doubt that HPV vaccines should be recommended for preadolescent girls in Croatia. However, reaching a decision on its possible introduction into the Childhood Vaccination Programme will require careful consideration of the larger picture and a comparison of the cost-effectiveness of a mandatory vaccination against other competing public health priorities.     

Clonal vaccinia virus grown in cell culture as a new smallpox vaccine

Although the smallpox virus was eradicated over 20 years ago, its potential release through bioterrorism has generated renewed interest in vaccination. To develop a modern smallpox vaccine, we have adapted vaccinia virus that was derived from the existing Dryvax vaccine for growth in a human diploid cell line. We characterized six cloned and one uncloned vaccine candidates. One clone, designated ACAM1000, was chosen for development based on its comparability to Dryvax when tested in mice, rabbits and monkeys for virulence and immunogenicity. By most measures, ACAM1000 was less virulent than Dryvax. We compared ACAM1000 and Dryvax in a randomized, double-blind human clinical study. The vaccines were equivalent in their ability to produce major cutaneous reactions ('takes') and to induce neutralizing antibody and cell-mediated immunity against vaccinia virus.     

Comparative study of smallpox vaccines from strains B-51, EM-63 and L-IVP in a controlled epidemiologic trial. I. Reactogenic characteristics of the smallpox vaccines]

A comparative study of smallpox vaccines prepared from the l-ivp zm-63 and b-51 strains was carried out under conditions of controlled epidemiological trial. Children subject to planned vaccination were scarified with commercial batches of the preparations under study (with the same infectious activity). As a result of investigations it was found that in the group of those scarified with the vaccine from zm-63 strain strong local and catarrhal reactions and some disturbances of general condition were more frequent than in those scarified with preparations from the l-ivp and b-51 strain. Along with this, the temperature elevation of various intensity showed no statistically significant difference in the groups a vaccinated with the vaccines compared. Integral analysis of signs characterising different manifestations of reactigenic properties of the vaccines compared led to the conclusion that preparations made of zm-6 strain had greater reactogenic properties.     

A mouse-based assay for the pre-clinical neurovirulence assessment of vaccinia virus-based smallpox vaccines

Post-vaccinal encephalitis, although relatively uncommon, is a known adverse event associated with many live, attenuated smallpox vaccines. Although smallpox vaccination ceased globally in 1980, vaccine manufacture has resumed in response to concerns over the possible use of smallpox virus as an agent of bioterrorism. To better support the production of safer smallpox vaccines, we previously reported the development of a mouse model in which a relatively attenuated vaccine strain (Dryvax^®) could be discerned from a more virulent laboratory strain (WR). Here we have further tested the performance of this assay by evaluating the neurovirulence of several vaccinia virus-based smallpox vaccines spanning a known range in neurovirulence for humans. Our data indicate that testing of 10–100 pfu of virus in mice following intracranial inoculation reliably assesses the virus's neurovirulence potential for humans.     

New approaches in vaccine development for parasitic infections

Vaccines have had a tremendous impact on the control of infectious diseases. Not only are vaccines potentially the least expensive mechanism to combat infectious diseases, under optimal conditions, widespread vaccination can result in disease eradication - as in the case of smallpox. Despite this great potential, vaccines have had little impact on human parasitic infections. The reasons for this are many - these eukaryotic pathogens are genetically and biologically complex organisms, some with elaborate life cycles and well-honed immune evasion mechanisms. Additionally, our understanding of the mechanisms of immune control of many parasitic infections -- of what constitutes an effective immune response and of how to induce high-quality immunological memory -- is not fully developed. This review attempts to highlight recent advances that could impact vaccine discovery and development in parasitic infections and proposes areas where future studies may lead to breakthroughs in vaccines for the agents of parasitic diseases. There are several other recent reviews highlighting the results of vaccine trials, specifically in the malaria field.     

Comparative study of the smallpox vaccines from B-51, EM-63 and L-IVP in a controlled epidemiological experiment. II. The characteristiics of the immunogenicity of the smallpox vaccines]

Immunogenicity of smallpox vaccines prepared of EM-63, L-IVP, and B-51 strains was studied under conditions of strict controlled epidemiological trial. Skin reactions to revaccination and vaccines antigenic activity indices were detemined in the persons vaccinated. Changes in the virus-neutralizing and antibodies suppressing hemagglutination was the same in persons vaccinated with any of the preparations tested. The maximal virus-neutralizing antibodies level was determined 1 month after the vaccination and persisted without any essential changes for one year. The titre of hemagglutination inhibiting antibodies also reached the maximum in one month, but diminished gradually by the end of one year after the vaccination. There were found no significant differences in the antigenic activity of the vaccines. The vaccines studied also displayed no difference in the number and character of skin reactions to revaccination. In comparing the antibodies level and the character of skin reactions to revaccination it was found that the titres of hemagglutination inhibiting antibodies and virus-neutralizing antibodies of 1:40 and over were in the great majority of cases determined in the blood sera of the vaccinated persons with the immediate and negative reactions to revaccination, i. e. in those with intensive postvaccinal immunity.     

An attenuated LC16m8 smallpox vaccine: analysis of full-genome sequence and induction of immune protection

The potential threat of smallpox bioterrorism has made urgent the development of lower-virulence vaccinia virus vaccines. An attenuated LC16m8 (m8) vaccine was developed in 1975 from the Lister strain used in the World Health Organization smallpox eradication program but was not used against endemic smallpox. Today, no vaccines can be tested with variola virus for efficacy in humans, and the mechanisms of immune protection against the major intracellular mature virion (IMV) and minor extracellular enveloped virion (EEV) populations of poxviruses are poorly understood. Here, we determined the full-genome sequences of the m8, parental LC16mO (mO), and grandparental Lister (LO) strains and analyzed their evolutionary relationships. Sequence data and PCR analysis indicated that m8 was a progeny of LO and that m8 preserved almost all of the open reading frames of vaccinia virus except for the disrupted EEV envelope gene B5R. In accordance with this genomic background, m8 induced 100% protection against a highly pathogenic vaccinia WR virus in mice by a single vaccination, despite the lack of anti-B5R and anti-EEV antibodies. The immunogenicity and priming efficacy with the m8 vaccine consisting mainly of IMV were as high as those with the intact-EEV parental mO and grandparental LO vaccines. Thus, mice vaccinated with 10(7) PFU of m8 produced low levels of anti-B5R antibodies after WR challenge, probably because of quick clearance of B5R-expressing WR EEV by strong immunity induced by the vaccination. These results suggest that priming with m8 IMV provides efficient protection despite undetectable levels of immunity against EEV.     

Design and development of oral drugs for the prophylaxis and treatment of smallpox infection

Smallpox was eradicated by the World Health Organization (WHO) vaccination campaign in the 1970s and the variola virus was restricted to repositories in the United States and Russia. Recently, however, concerns have arisen about the possible existence of variola outside these sites and the potential for using the virus as a weapon of bioterror. The world population now has little residual immunity to smallpox and supplies of the smallpox vaccine are being reconstituted. Large numbers of individuals with various skin diseases or immunosuppression owing to AIDS or organ transplantation medications, or who are pregnant or have heart disease might not be ideal candidates for vaccination with the current live vaccines. It would be useful to have an orally active drug that could be self-administered in case of an outbreak of smallpox.     

The smallpox vaccine: a multidimensional model of choice

Following September 11, 2001, the U.S. government increased its efforts to prepare for future attacks, including those using dangerous biological agents such as smallpox. The smallpox vaccination program called for vaccinating military personnel and smallpox response teams, including healthcare workers and other first responders. The program of vaccinating healthcare workers was largely unsuccessful; few individuals volunteered to be vaccinated, highlighting the importance of understanding the factors that influence choice regarding this complex medical decision. This study examined stated choice and how it was associated with risk perceptions, knowledge, psychological distress, and general vaccine beliefs using a five-dimensional choice model. The model used multivariable modeling strategies in a sample of 256 undergraduate, graduate, and medical students. Sixty-three percent of the sample stated that they would elect to receive the smallpox vaccination. Multiple factors were related to stated choice in multivariable models, including perceived risk/worry, general vaccine beliefs, decisional conflict, and gender. However, the models were more successful at predicting acceptance of the vaccination than vaccine refusal. Although support was obtained for a multidimensional model of choice, several questions were raised by our results, including (a) whether refusal of smallpox vaccination can be more effectively characterized, possibly with additional questions; (b) whether the model translates to actual vaccination behavior; and (c) whether the model describes choice in more at-risk samples (e.g., first responders, healthcare workers). A multidimensional modeling approach should facilitate these and other studies of choice.     

Veterinary and human vaccine evaluation methods

Despite the universal importance of vaccines, approaches to human and veterinary vaccine evaluation differ markedly. For human vaccines, vaccine efficacy is the proportion of vaccinated individuals protected by the vaccine against a defined outcome under ideal conditions, whereas for veterinary vaccines the term is used for a range of measures of vaccine protection. The evaluation of vaccine effectiveness, vaccine protection assessed under routine programme conditions, is largely limited to human vaccines. Challenge studies under controlled conditions and sero-conversion studies are widely used when evaluating veterinary vaccines, whereas human vaccines are generally evaluated in terms of protection against natural challenge assessed in trials or post-marketing observational studies. Although challenge studies provide a standardized platform on which to compare different vaccines, they do not capture the variation that occurs under field conditions. Field studies of vaccine effectiveness are needed to assess the performance of a vaccination programme. However, if vaccination is performed without central co-ordination, as is often the case for veterinary vaccines, evaluation will be limited. This paper reviews approaches to veterinary vaccine evaluation in comparison to evaluation methods used for human vaccines. Foot-and-mouth disease has been used to illustrate the veterinary approach. Recommendations are made for standardization of terminology and for rigorous evaluation of veterinary vaccines.     

Development of smallpox vaccine candidates with integrated interleukin-15 that demonstrate superior immunogenicity, efficacy, and safety in mice

The potential use of variola virus, the etiological agent of smallpox, as a bioterror agent has heightened the interest in the reinitiation of smallpox vaccination. However, the currently licensed Dryvax vaccine, despite its documented efficacy in eradicating smallpox, is not optimal for the vaccination of contemporary populations with large numbers of individuals with immunodeficiencies because of severe adverse effects that can occur in such individuals. Therefore, the development of safer smallpox vaccines that can match the immunogenicity and efficacy of Dryvax for the vaccination of contemporary populations remains a priority. Using the Wyeth strain of vaccinia virus derived from the Dryvax vaccine, we generated a recombinant Wyeth interleukin-15 (IL-15) with integrated IL-15, a cytokine with potent immunostimulatory functions. The integration of IL-15 into the Wyeth strain resulted in a >1,000-fold reduction in lethality of vaccinated athymic nude mice and induced severalfold-higher cellular and humoral immune responses in wild-type mice that persisted longer than those induced by the parental Wyeth strain. The superior efficacy of Wyeth IL-15 was further demonstrated by the ability of vaccinated mice to fully survive a lethal intranasal challenge of virulent vaccinia virus even 10 months after vaccination, whereas all mice vaccinated with parental Wyeth strain succumbed. By integrating IL-15 into modified vaccinia virus Ankara (MVA), a virus currently under consideration as a substitute for the Dryvax vaccine, we developed a second vaccine candidate (MVA IL-15) with greater immunogenicity and efficacy than Dryvax. Thus, Wyeth IL-15 and MVA IL-15 viruses hold promise as more-efficacious and safe alternatives to the Dryvax vaccine.     

Quantification of antibody responses against multiple antigens of the two infectious forms of Vaccinia virus provides a benchmark for smallpox vaccination

Smallpox was eradicated without an adequate understanding of how vaccination induced protection. In response to possible bioterrorism with smallpox, the UK government vaccinated approximately 300 health care workers with vaccinia virus (VACV) strain Lister. Antibody responses were analyzed using ELISA for multiple surface antigens of the extracellular enveloped virus (EEV) and the intracellular mature virus (IMV), plaque reduction neutralization and a fluorescence-based flow cytometric neutralization assay. Antibody depletion experiments showed that the EEV surface protein B5 is the only target responsible for EEV neutralization in vaccinated humans, whereas multiple IMV surface proteins, including A27 and H3, are targets for IMV-neutralizing antibodies. These data suggest that it would be unwise to exclude the B5 protein from a future smallpox vaccine. Repeated vaccination provided significantly higher B5-specific and thus EEV-neutralizing antibody responses. These data provide a benchmark against which new, safer smallpox vaccines and residual immunity can be compared.     

Reactions after pertussis vaccine: a manufacturer's experiences and difficulties since 1964

Pertussis vaccines vary in quality, safety, and efficacy according to the production strains of Bordetella pertussis, the method of manufacture, and quality control procedures. It is therefore not justifiable to combine information on the incidence, nature, and severity of reactions after all manufacturers'' pertussis vaccines as if they were a single product. Attempts were made to collect information on all suspected cases of severe reactions that occurred after administration of about 15 million doses of Wellcome pertussis vaccines in the United Kingdom and Northern Ireland from 1964 to mid-1977. Altogether six deaths, six neurological reactions with sequelae, and 17 convulsions without sequelae were reported, but some were clearly not attributable to the vaccine, while, in other cases, the available information was inadequate for assessing the role of vaccination. Neurological disorders, similar to those reported in a few children after pertussis vaccination, occur unexpectedly in apparently healthy infants at the recommended age for immunisation, so chance association between vaccination and these events can be expected in some children. The Joint Committee on Vaccination and Immunisation has made several recommendations aimed at reducing severe reactions after pertussis vaccination. These include replacing plain vaccine with aluminium-adsorbed vaccine, but there is no clear evidence that the aluminium-adsorbed vaccine produces fewer reactions than the plain.There are difficulties enough in deciding the cause of events that occur after vaccination, since these reactions often occur naturally in children of vaccination age. The task is made even harder by the assumption that various manufacturers'' vaccines are the same and the lack of information available to manufacturers about cases in which their vaccine has been implicated. Information on vaccines administered is entered on immunisation records cards; it should be used and referred to if reactions occur.     

Role of whole-cell pertussis vaccine in severe local reactions to the preschool (fifth) dose of diphtheria-pertussis-tetanus vaccine.

OBJECTIVE: To estimate the contribution of whole-cell pertussis vaccine to severe local reactions after the preschool (fifth) dose of adsorbed diphtheria toxoid-pertussis vaccine-tetanus toxoid (DPT) vaccine. DESIGN: Double-blind randomized controlled trial. SETTING: Urban community. PARTICIPANTS: Volunteer sample of 200 healthy children 4 to 6 years old who were eligible for the fifth dose of DPT vaccine. INTERVENTIONS: Children received, in both arms, either diphtheria toxoid-tetanus toxoid (DT) and monovalent pertussis vaccines (group A, 99 children) or DPT and meningococcal vaccines (group B, 101 children). All were licensed products from single lots. The children were assessed 24 hours later by a trained observer. Serum samples obtained before vaccination were tested for antibodies to tetanus and diphtheria toxins and five pertussis antigens by means of enzyme-linked immunosorbent assay. MAIN OUTCOME MEASURES: Rates of severe local reactions (an area of redness or swelling or both of 50 mm or greater) 24 hours after vaccination. Relation between serum antibody levels before vaccination and rates of severe local reactions to corresponding vaccines. RESULTS: All of the subjects were followed up 24 hours after vaccination. Severe redness was present in 38% given DPT vaccine, 29% given intramuscular pertussis vaccine and 9% given DT vaccine (p < or = 0.002, three-way comparison). Severe swelling was common after vaccination with all three products. After intramuscular pertussis vaccination a relation was evident between the prevaccination levels of antibody to whole-cell pertussis bacteria and the rates of redness (p < 0.02) but not between the prevaccination subcellular antibody levels and the rates of redness. CONCLUSION: That pertussis vaccine resembled the DPT vaccine in causing severe redness suggests that it is the principal cause of such reactions after DPT vaccination. The DT vaccine was also reactogenic; thus, cumulative sensitization to one or more of its constituents may be a factor.     

Viral vaccines and their manufacturing cell substrates: New trends and designs in modern vaccinology

Vaccination is one of the most effective interventions in global health. The worldwide vaccination programs significantly reduced the number of deaths caused by infectious agents. A successful example was the eradication of smallpox in 1979 after two centuries of vaccination campaigns. Since the first variolation administrations until today, the knowledge on immunology has increased substantially. This knowledge combined with the introduction of cell culture and DNA recombinant technologies revolutionized vaccine design. This review will focus on vaccines against human viral pathogens, recent developments on vaccine design and cell substrates used for their manufacture. While the production of attenuated and inactivated vaccines requires the use of the respective permissible cell substrates, the production of recombinant antigens, virus‐like particles, vectored vaccines and chimeric vaccines requires the use – and often the development – of specific cell lines. Indeed, the development of novel modern viral vaccine designs combined with, the stringent safety requirements for manufacture, and the better understanding on animal cell metabolism and physiology are increasing the awareness on the importance of cell line development and engineering areas. A new era of modern vaccinology is arriving, offering an extensive toolbox to materialize novel and creative ideas in vaccine design and its manufacture.     

DNA疫苗安全性的策略探究

DNA疫苗安全性问题主要来自DNA疫苗元件和疫苗工程菌,包括DNA疫苗与宿主基因组整合、接种后诱导宿主产生免疫耐受和自身免疫疾病、抗性基因的转移问题、疫苗中内毒素和抗生素及其他有害物质残留问题、宿主菌体内DNA复制与纯化过程中基因稳定性问题。本文针对这些问题进行策略上的探讨,为进一步开发安全的DNA疫苗提供帮助。     

Results of the research on the preparation and testing of live oral smallpox vaccine in tablet form]

The authors sum up the results of decade of investigations on the elaboration and trial of live oral smallpox vaccine in tablet form. A conclusion was made that due to mild reactogenic properties, satisfactory immunogenicity and weak allergy producing properties, the mentioned preparation, along with a possibility of express and mass use, can posses future prospects under conditions of final smallpox eradication.     

Modified vaccinia virus Ankara protects macaques against respiratory challenge with monkeypox virus

The use of classical smallpox vaccines based on vaccinia virus (VV) is associated with severe complications in both naive and immune individuals. Modified vaccinia virus Ankara (MVA), a highly attenuated replication-deficient strain of VV, has been proven to be safe in humans and immunocompromised animals, and its efficacy against smallpox is currently being addressed. Here we directly compare the efficacies of MVA alone and in combination with classical VV-based vaccines in a cynomolgus macaque monkeypox model. The MVA-based smallpox vaccine protected macaques against a lethal respiratory challenge with monkeypox virus and is therefore an important candidate for the protection of humans against smallpox.     

Evaluation of the vaccinal process in skin-scarification and oral immunization of rabbits with live smallpox vaccines

On the basis of comparative experimental evaluation of specific features in the course of the vaccinal process after the immunization of laboratory animals with live smallpox vaccines, intended for oral use (in tablets) and for skin scarification was proposed. In experiments on rabbits, made with the use of virological and immunological methods, the counteraction of the elements constituting the vaccinal process was analyzed, the integral evaluation of its course was given, the greater safety of the oral preparation in comparison with the traditional vaccine for immunization by skin-scarification method were established. The conclusion was made that oral immunization was the safest immunization method under modern conditions and promising one for using live vaccines with population immunity being at a low level or absent.