The development of a new generation of pertussis vaccine

The results of the weight gain test on mice have shown that acellular pertussis vaccine is less toxic than the pertussis component of adsorbed diphtheria-pertussis-tetanus (DPT) vaccine due to a lower content of endotoxin in the acellular vaccine; but the leukocytosis-promoting and histamine-sensitizing activities of JNIH-6 and adsorbed DPT vaccines are indicative of incomplete inactivation of Bordetella pertussis toxin. The content of incompletely inactivated B. pertussis toxin is practically the same in both preparations, constituting 1/100-1/200 of the calculated initial activity. For this reason, the use of the new pertussis vaccine also involves a risk of development of serious postvaccinal reactions and/or complications caused by this toxin. Search for the optimum method of inactivation of B. pertussis main toxin should be continued. As shown by the enzyme immunoassay, acellular pertussis vaccine used in the same immunizing dose as adsorbed DPT vaccine induces a more intensive immune response to hemagglutinin and B. pertussis toxin. This is due to higher residual toxicity of the corpuscular component of adsorbed DPT vaccine. Induction of antibodies to B. pertussis toxin has been shown to decrease in response to injection of acellular pertussis vaccine containing a certain residual amount of incompletely inactivated B. pertussis toxin.     

Immunomodulation activity of new vaccines for pertussis prophylaxis--acellular pertussis vaccine and adsorbed DPT vaccine with acellular component

The immunomodulating activity of acellular pertussis vaccine (APV) and adsorbed DPT vaccine with acellular pertussis component (DPTA vaccine) was studied. The study revealed that only large doses of APV, 10 immunizing doses (ID), suppressed humoral and cell-mediated response to sheep red blood cells (SRBC). 1 ID produced no influence on the formation of antibody producing cells, but increased the development of delayed hypersensitivity (DH) to SRBC. The modulation of cell-mediated immune response, induced by APV, returned to normal after the injection of purified staphylococcal toxoid, used as immunomodulator, in doses of 0.15 BU per mouse and 1.5 BU per mouse. DPTA vaccine containing 1 ID, as well as 10 ID, produced no immunomodulating effect. This was established by the evaluation of humoral response to SRBC in CBA mice and the study of the formation of DH to SRBC in BALB/c mice. As indicated by the total of the presented data, the inclusion of APV into DPTA vaccine enhanced the immunological safety of its pertussis component.     

The characteristics of the development of immunity with a primary immunization complex using adsorbed DTP vaccine

The intensity of immunity, depending on immune response variants characterized by the definite composition of the T and B lymphocyte subpopulation in peripheral blood, was studied in 70 practically healthy young children after the primary complex of immunization with adsorbed DPT vaccine. The most stable immune reaction was shown to appear in children with the hyperergic and normoergic variants of immune response to diphtheria and tetanus toxoids, while the reaction to pertussis antigen was essentially weaker both after the second vaccination and after the first revaccination. In children with the hypoergic variant of immune response to all components of adsorbed DPT vaccine the resulting immune reaction was 2.5-3 times weaker than in children of other groups.     

Comparative study of the immunoglobulins and specific antibodies in the blood of rabbits immunized with ADTP vaccine and ADT-anatoxin with normal and reduced antigen contents

Adsorbed DPT vaccine and adsorbed DT toxoids with normal and reduced antigen content were used for the immunization of rabbits. The levels of IgM and IgG and the dynamics of antibodies to diphtheria and tetanus toxins and to Bordetella pertussis in the blood sera of the animals were studied in the postvaccinal period (on days 15 and 34). This study revealed that the reduction of the antigen content of adsorbed DT toxoid to 5 Lf of diphtheria toxoid and 5 binding units of tetanus toxoid did not decrease the capacity of the preparation for increasing the levels of IgG and IgM, antibodies to diphtheria and tetanus toxins in the sera of the rabbits. The reduced content of these toxoids in adsorbed DPT vaccine did not affect its capacity for inducing the enhanced synthesis of IgG, antibodies to diphtheria and tetanus toxins, while the production of IgM and IgA remained unchanged. At the same time an increase in the titers of antibodies to B. pertussis in the animals was less pronounced than that observed after the injection of commercial adsorbed DPT vaccine. Additional investigations are necessary in order to establish the protective potency of the pertussis component in adsorbed DPT vaccine with the reduced content of toxoids and to find out the optimum antigenic composition for this preparation.     

The effect of histamine on the rosette-forming ability of T-lymphocytes upon immunization with DPT vaccine and its components

The influence exerted by histamine on the capacity of T-lymphocytes for spontaneous rosette formation in intact animals and in animals immunized with adsorbed DPT vaccine and its components has been studied. Histamine at a concentration of 10(-3) M has been found to produce an inhibitory effect on the capacity of lymphocytes in the blood and spleen of guinea pigs immunized with adsorbed DPT vaccine and its components for spontaneous rosette formation. This effect of histamine has proved to be even more pronounced after the immunization of the animals with adsorbed DPT vaccine and Bordetella pertussis suspension, which is probably due to their sensitizing action.     

Evaluation of postvaccinal pertussis immunity by using immunoenzyme analysis

The effectiveness of adsorbed DPT vaccine manufactured in the USSR, evaluated by its capacity of inducing the formation of the main classes of immunoglobulins and by the duration of immune response to the acellular complex of protective antigens (pertussis toxin and agglutinogen-2), was studied with the use of modified EIA. Out of 273 children immunized with adsorbed DPT vaccine in the course of this study, 87.2% had IgG-antibodies, 14.1% had IgA-antibodies and 3.2% of the children had IgM-antibodies. The level of immunity in children having received the full course of immunization with adsorbed DPT vaccine was significantly higher in comparison with children given only the primary course of immunization and nonimmunized children of the same age. Antipertussis immunity was found to decrease two years after the completion of the course of immunization with adsorbed DPT vaccine and in children over 5-6 years of age. Adsorbed DPT vaccine prevented the disease, but not infection. The level of postinfection immunity was higher than that of postvaccinal immunity.     

Comparative immunologic effectiveness of variants of the DTP vaccine

The immunological effectiveness of two batches of adsorbed DPT vaccine, the batch with the normal content of antigens (control) and the batch with the content of diphtheria and tetanus toxoids reduced to 20 Lf/ml and 5 BU/ml respectively (test batch), has been studied under the conditions of controlled trial. As a result, the reduction of the antigenic content of adsorbed DPT vaccine has been found to exert no negative influence on the immunological effectiveness of the diphtheria, tetanus, and pertussis components of this preparation under the conditions of the new immunization schedule.     

Effect of histamine on the rosette-forming capacity of T-lymphocytes in immunization with ADPT vaccine and its components

The results obtained in the study of the influence of histamine on the capacity of T-lymphocytes of guinea pigs immunized with DPT-vaccine and its components for spontaneous rosette formation are presented. Histamine at a concentration of 10(-3) M has been found to inhibit the capacity of blood and splenic lymphocytes of guinea pigs immunized with adsorbed DPT vaccine for spontaneous rosette formation. The inhibitory effect is more pronounced after the immunization of the animals with adsorbed DPT vaccine and Bordetella pertussis suspension.     

Prophylaxis of pertussis: development and use of acellular pertussis vaccine

Modern data substantiating the expediency of the use of acellular pertussis vaccine were analyzed. Serious postvaccinal complications caused by the action of the corpuscular pertussis component of adsorbed DPT vaccine served as the basis for the development of acellular pertussis vaccine (APV). During the period of 1990-1996 as many as 8 international field trials of the effectiveness of APV were carried out. The results of these trials and studies were evaluated in accordance with the unified programs and criteria. The vaccines under test differed by the composition of Bordetella pertussis purified antigens they contained, the methods of their purification and the detoxification of pertussis toxin. All tested APV, with the exception SKB-2, possessed pronounced prophylactic activity.     

Limited controlled trial of the reactogenic properties of ADTP vaccines containing stab cultures as the pertussis component

The reactogenic properties of adsorbed DPT vaccine containing Bordetella pertussis cultures, grown by submerged cultivation, as the pertussis component were studied. The study revealed that the vaccine was low-reactogenic: no severe postvaccinal reactions were recorded in immunized children. The frequency and intensity of febrile and local reactions in children immunized with adsorbed DPT vaccine under trial and the commercial preparation commonly used in the USSR were identical, but considerably less pronounced than in children immunized with foreign vaccines having similar composition.     

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.     

Isolation of hemolytic cultures of Bordetella pertussis intended for the production of acellular pertussis preparations and the characterization of their biological properties

The heterogeneity of the population of B. pertussis laboratory strains with respect to the capacity of individual clones to lyse erythrocytes has been established. The complete or partial reduction of the antigens under study in nonhemolytic bacteria has been shown. The use of hemolytic cultures for the preparation of acellular pertussis vaccine makes it possible to increase the content of B. pertussis toxin in these vaccines.     

Antipertussis immunity studied by immunoenzyme analysis

The levels of antibodies to disintegrated Bordetella pertussis and its individual fractions (protein and polysaccharide) in children immunized with different batches of adsorbed DPT vaccine have been determined with the use of EIA techniques. The background level of antibodies in the control groups has been determined, and in immunized children the levels of antibodies to disintegrated B. pertussis and its protein fraction have been shown to considerably exceed the levels of antibodies to lipopolysaccharide.     

Evaluation of the reactogenicity and immunogenic potency of combined vaccine "Bubo-Kok" in the immunization of children against diphtheria, tetanus, pertussis and viral hepatitis B

Combined vaccine "Bubo-Kok" is characterized by safety and high immunological activity. The number of postvaccinal reactions in children aged 1 and 2 years, immunized with vaccine "Bubo-Kok", was not statistically different from those in groups of children immunized with adsorbed DPT vaccine, as well with such vaccine in combination with vaccine against hepatitis B. After the completion of the primary course of immunization 100% of children had protective antibody titers against diphtheria, tetanus and hepatitis B. Antibody titers against pertussis, equal to or exceeding protective titers, were found in more than 70% of immunized children. The immunogenic potency of vaccine "Bubo-Kok" with respect to all its components was not inferior to that of adsorbed DPT vaccine and vaccine against hepatitis B, when introduced simultaneously in different areas of the body. Vaccine "Bubo-Kok" successfully passed state trials and was recommended for registration.     

Experience of the People's Republic of Bulgaria in controlling diphtheria, tetanus and whooping cough

The analysis of the morbidity and mortality rates in diphtheria, tetanus and pertussis in Bulgaria after the introduction of the compulsory mass immunization of children with combined DPT vaccine is presented. These data indicate that morbidity in diphtheria, tetanus and pertussis has sharply decreased. Favorable results with respect to these three diseases are the consequence of the complete coverage of the child population by immunization with the vaccine whose quality has been steadily improving for the last 20 years. A higher purity of toxoids has been achieved, and at present it exceeds the latest WHO requirements. Pertussis vaccine is produced with the use of strains whose serological characteristics correspond to those of the pertussis strains circulating in the country. The study of the reactogenicity of DPT vaccine, carried out over the period of 20 years, has shown that the vaccine has low reactogenicity.     

Evaluation of the stability of pertussis vaccine OCO-3 standard

The evaluation of the immunogenic activity and residual toxicity of the National Standard of pertussis vaccine (OCO-3) was carried out. As shown by observations lasting for a period of 25 years, the preparation possesses stable immunogenicity and its toxicity remained unchanged, which makes it possible to use OCO-3 for the routine control of the pertussis component of commercial lots of adsorbed DPT vaccine.     

The evaluation of the mutagenic activity of pertussis vaccinal preparations]

Two vaccine preparations obtained from Bordetella pertussis, whole-cell vaccine constituting one of the components of adsorbed DPT vaccine and acellular vaccine, were tested for mutagenicity. The doses of the preparations covered the range 1-100 ED50. Ames' test and the metaphase analysis of marrow cells of C57BL/6J mice were used. The acellular preparation was also tested on thymectomized mice, taking into consideration chromosomal aberrations in marrow metaphases. Whole-cell and acellular pertussis vaccines did not induce mutations in Salmonella typhimurium and chromosomal aberrations in mouse marrow cells.     

Effect of duration of the intervals between immunization with DPT vaccine on the serological indices in children

The influence of the interval between injections of adsorbed DPT vaccine on the effectiveness of immunization has been studied. The intensity of antibody formation to the pertussis component has been found to decrease 2.7-3.7 times if the interval between the injections constituting the course of primary immunization is prolonged for more than 6 months. The interval between the course of primary immunization and the first booster injection, which lasts 1.5-2 years in accordance with the currently accepted immunization schedule, is unreasonably long. Immunological characteristics in respect to pertussis have been found to decrease 8-45 times as early as 16 months after the first booster injection. Most of the vaccines catching pertussis at that time had the moderately severe form of this infection.     

Comparative quantitation for the protein content of diphtheria and tetanus toxoids by DC protein assay and Kjeldahl method.

DPT, a combination vaccine against diphtheria, tetanus and pertussis is available since many years and still continued in the national immunisation schedule of many countries. Although highly potent, reactions to DPT vaccine are well known, mainly attributed to the factors like Pertussis component, aluminum adjuvant and lower purity of tetanus and diphtheria toxoids. The latter most important aspect has become a matter of concern, specially for the preparation of next generation combination vaccines with more number of antigens in combination with DPT.Purity of toxoid is expressed as Lf (Limes flocculation) per mg of protein nitrogen. The Kjeldahl method (KM) of protein nitrogen estimation suggested by WHO and British Pharmacopoeia is time consuming and less specific. Need has been felt to explore an alternative method which is quick and more specific for toxoid protein determination. DC (detergent compatible) protein assay, an improved Lowry's method, has been found to be much more advantageous than Kjeldahl method.     

Reactogenic properties of a DTP vaccine with a reduced antigen dosage

The reactogenic properties of batches of adsorbed DPT vaccine with the normal content of antigens and with the content of diphtheria and tetanus toxoids reduced, respectively, to 10 Lf and 5 BU per immunization dose have been studied under the conditions of a controlled epidemiological trial. The reduced antigenic content of adsorbed DPT vaccine decreased the number of vaccinal reactions 1.8 times, as well as the intensity of their manifestations.