Evaluation of the immunological activity and safety of group B meningococcal vaccine prepared from a natural complex of specific polysaccharide and outer membrane proteins

Immunological activity and safety of group B meningococcal vaccine prepared from a natural complex of specific polysaccharide and outer membrane proteins were under study. The immunological safety of the vaccine was evaluated by the absence of antibodies to denaturated and native DNA (d-DNA and n-DNA). As shown with the use of the enzyme immunoassay (EIA), the administration of the vaccine did not induce antibody formation to d-DNA and n-DNA during the observation period. The titer of bactericidal antibodies in the immune bacteriolysis assay (IBA) to the vaccine strain B:2b:P1.2 after immunization increased four-fold and greater in 80% of the vaccinated persons. The significant increase of bactericidal antibodies to heterologous strains B:2a:P1.2 and B:15:P1.7 was registered in 20-30% of the vaccinees, respectively. A month after the repeated vaccination an increase in specific IgG antibodies to the complex antigen was found to occur according to EIA results. The use of RIB made it possible to evaluate the preventive activity of group B meningococcal vaccine as a whole and to suppose that the vaccine induced mainly type-specific response.     

Comparative study of the antigenic activity and allergic transformation of the body in human revaccination with different doses of a chemical brucellosis vaccine

The study of different doses of chemical brucellosis vaccine (0.5 mg, 0.75 mg and 1 mg), used for the booster immunization of persons who had received primary immunization with chemical and live brucellosis vaccines, revealed that the characteristics of its antigenic potency were somewhat higher after primary immunization with the live vaccine. When used for booster immunization, the tested doses showed no differences in their antigenic potency irrespective of prior immunizations received by the immunized persons. In booster immunization chemical brucellosis vaccine was found to have poorly pronounced allergenic properties irrespective of its booster dose with the tendency towards greater sensitization to brucellosis allergen in persons primarily immunized with the live vaccine. When considering the possibility of using brucellosis chemical vaccine in medical practice, the complex evaluation of the characteristics showing its reactogenicity and antigenic potency, as well as the allergic transformation of the body induced by the injection of the vaccine, was carried out, which made it possible to recommend 1 mg of the vaccine as the optimal booster dose.     

A one dose experimental cholera vaccine

The number of cholera vaccine doses required for immunity is a constraint during epidemic cholera. Protective immunity following one dose of multiple Vibrio cholerae (Vc) colonization factors (Inaba LPS El Tor, TcpA, TcpF, and CBP-A) has not been directly tested even though individual Vc colonization factors are the protective antigens. Inaba LPS consistently induced vibriocidal and protective antibodies at low doses. A LPS booster, regardless of dose, induced highly protective secondary sera. Vc protein immunogens emulsified in adjuvant were variably immunogenic. CBP-A was proficient at inducing high IgG serum titers compared with TcpA or TcpF. After one immunization, TcpA or TcpF antisera protected only when the toxin co-regulated pilus operon of the challenge Vc was induced by AKI culture conditions. CBP-A was not consistently able to induce protection independent of the challenge Vc culture conditions. These results reveal the need to understand how best to leverage the 'right' Vc immunogens to obtain durable immunity after one dose of a cholera subunit vaccine. The dominance of the protective anti-LPS antibody response over other Vc antigen antibody response needs to be controlled to find other protective antigens that can add to anti-LPS antibody-based immunity.     

Transition in the Character of Immunological Memory in Mice after Immunization

The immunological memory in antibody response of mice to bovine serum albumin was investigated at the level of IgM and IgG antibody-forming cells. The antigen at a dose much lower than required for eliciting a detectable level of the primary antibody response could latently activate the immune machinery to an extent adequate for specific recall, whereas higher doses of antigen were effective in evoking strong anamnestic response. The potentiality to develop the anamnestic response was found even in the latent phase of the primary antibody response and was maintained for more than 2 months. The immunological memory acquired in an early phase after the primary immunization mainly involved IgM antibody response and late memory concerned IgG response.     

Isotypic characteristics of serum and secretory O antibodies and local immunological memory in the parenteral immunization of guinea pigs with a ribosomal Shigella vaccine

Guinea pigs were immunized subcutaneously with ribosomal vaccine prepared from S. sonnei and their systemic and local humoral response was studied by means of ELISA techniques with the use of monospecific antisera to guinea pig IgA and IgG. Injection of the ribosomal vaccine leads to a significant rise in the levels of IgA O-antibodies in tears, IgG and IgA O-antibodies in the serum. The presence of IgA O-antibodies in tears was seemingly the result of their local synthesis rather than the seepage of serum IgA. The stimulation of the local and systemic anti-O response was more pronounced after parenteral immunization with the ribosomal vaccine than after immunization with the corresponding dose of lipopolysaccharide (LPS). Parenteral immunization with the ribosomal vaccine induced the development of both systemic and local memory. The priming effect produced by relatively small doses of this vaccine (40 micrograms), administered parenterally, was similar to the effect of prolonged and intensive stimulation ensured by 10-day feeding with LPS (the total dose being 5,000 micrograms).     

A comparative evaluation of the immunological efficacy of ADPT vaccine and ADT-M anatoxin in the immunization of children against diphtheria and tetanus

Comparative study of the immunological effectiveness of adsorbed diphtheria-pertussis-tetanus (DPT) vaccine and adsorbed diphtheria-tetanus toxoid with reduced antigen content (adsorbed DT toxoid R) in the immunization of children, carried out in accordance with the vaccination schedule, was made. Immune response to the injection of adsorbed DPT vaccine was higher than after immunization with adsorbed DT toxoid R, as evidenced by antibody titers. It was probably due to differences in the number of injections constituting the course of immunization: it consisted of 3 injections and 1 booster injection for adsorbed DPT vaccine and 2 injections and 1 booster injection for adsorbed DT toxoid R. Immunization with adsorbed DPT vaccine produced immunity which was retained for a longer period. These results are indicative of the expediency of the primary immunization of children with adsorbed DT toxoid R introduced in three injections in order to ensure more stable and prolonged postvaccinal (mainly antidiphtheria) immunity.     

Concentration and avidity of anti-tetanus antibodies in mother-infant pairs: Relation to immunization time

Abstract The concentration and avidity of anti-tetanus antibodies in two groups of mother-infant pairs were compared. Mothers immunized during pregnancy and their newbons (group A) had significantly higher antibody concentrations than mothers immunized at least a year before their last pregnancy and their newborns (group B) as measured by an indirect enzyme immunoassay (EIA) procedure. Antibody avidity of samples was measured by an inhibition EIA technique and urea denaturation test. Although antibody avidity was higher in group B, the differences were not significant. These findings may represent a secondary antibody response to a protein antigen, when considering that all mothers in both groups had received a primary tetanus vaccination during childhood. In mothers with a history of primary tetanus immunization, a single booster dose of tetanus toxoid during pregnancy is enough to induce protective levels of antibodies with reasonably high avidity in both mother and newborn.     

Reaginic antibody formation in the mouse. X. Possible role of suppressor T cells in transient IgE antibody responses.

The kinetics of IgE antibody response to alum-absorbed dinitrophenyl derivatives of ovalbumin (DNP-OA) was dependent on the dose of immunogen. A persistent IgE antibody response was obtained when high responder BDF1 mice were immunized with a minimum (0.05 microgram) dose. An increase of the immunogen to 10 microgram depressed IgE antibody responses but enhanced IgG antibody responses of both hapten and carrier specificities. Determination of T helper cell activity and B memory cells after immunization with different doses of antigen indicated that minimum immunogen was favorable for developing helper activity, whereas 1 to 10 microgram immunogen were more favorable than a 0.05-microgram dose for developing both IgE and IgG B memory cells. Nevertheless, neither helper T cells nor B memory cells in the spleen explains a transient IgE antibody response to a high (10 microgram) dose of DNP-OA. Evidence was obtained that immunization with 10 microgram OA induced generation of antigen-specific suppressor T cells, which were not detectable after immunization with 0.05 microgram OA. Transfer of suppressor T cells to DNP-OA-primed mice depressed both anti-hapten and anti-carrier IgE antibody responses. The results suggested strongly that suppressor T cells are involved in a transient IgE antibody response to a high-dose immunogen.     

Protective immunity to vaccinia virus induced by vaccination with multiple recombinant outer membrane proteins of intracellular and extracellular virions

Infectious intracellular and extracellular forms of vaccinia virus have different outer membrane proteins, presenting multiple targets to the immune system. We investigated the immunogenicity of soluble forms of L1, an outer membrane protein of the intracellular mature virus, and of A33 and B5, outer membrane proteins of the extracellular enveloped virus. The recombinant proteins, in 10-microg amounts mixed with a Ribi- or saponin-type adjuvant, were administered subcutaneously to mice. Antibody titers to each protein rose sharply after the first and second boosts, reaching levels that surpassed those induced by percutaneous immunization with live vaccinia virus. Immunoglobulin G1 (IgG1) antibody predominated after the protein immunizations, indicative of a T-helper cell type 2 response, whereas live vaccinia virus induced mainly IgG2a, indicative of a T-helper cell type 1 response. Mice immunized with any one of the recombinant proteins survived an intranasal challenge with 5 times the 50% lethal dose of the pathogenic WR strain of vaccinia virus. Measurements of weight loss indicated that the A33 immunization most effectively prevented disease. The superiority of protein combinations was demonstrated when the challenge virus dose was increased 20-fold. The best protection was obtained with a vaccine made by combining recombinant proteins of the outer membranes of intracellular and extracellular virus. Indeed, mice immunized with A33 plus B5 plus L1 or with A33 plus L1 were better protected than mice immunized with live vaccinia virus. Three immunizations with the three-protein combination were necessary and sufficient for complete protection. These studies suggest the feasibility of a multiprotein smallpox vaccine.     

Screening of protective antigens of Japanese encephalitis virus by DNA immunization: a comparative study with conventional viral vaccines

In this study, we evaluated the relative role of the structural and nonstructural proteins of the Japanese encephalitis virus (JEV) in inducing protective immunities and compared the results with those induced by the inactivated JEV vaccine. Several inbred and outbred mouse strains immunized with a plasmid (pE) encoding the JEV envelope protein elicited a high level of protection against a lethal JEV challenge similar to that achieved by the inactivated vaccine, whereas all the other genes tested, including those encoding the capsid protein and the nonstructural proteins NS1-2A, NS3, and NS5, were ineffective. Moreover, plasmid pE delivered by intramuscular or gene gun injections produced much stronger and longer-lasting JEV envelope-specific antibody responses than immunization of mice with the inactivated JEV vaccine did. Interestingly, intramuscular immunization of plasmid pE generated high-avidity antienvelope antibodies predominated by the immunoglobulin G2a (IgG2a) isotype similar to a sublethal live virus immunization, while gene gun DNA immunization and inactivated JEV vaccination produced antienvelope antibodies of significantly lower avidity accompanied by a higher IgG1-to-IgG2a ratio. Taken together, these results demonstrate that the JEV envelope protein represents the most critical antigen in providing protective immunity.     

FetA Antibodies Induced by an Outer Membrane Vesicle Vaccine Derived from a Serogroup B Meningococcal Isolate with Constitutive FetA Expression

Invasive meningococcal disease causes over 3500 cases each year in Europe, with particularly high incidence among young children. Among serogroup B meningococci, which cause most of the cases, high diversity in the outer membrane proteins (OMPs) is observed in endemic situations; however, comprehensive molecular epidemiological data are available for the diversity and distribution of the OMPs PorA and FetA and these can be used to rationally design a vaccine with high coverage of the case isolates. The aim of this study was to determine whether outer membrane vesicles (OMVs) derived from an isolate with constitutive FetA expression (MenPF-1 vaccine) could be used to induce antibodies against both the PorA and FetA antigens. The immunogenicity of various dose levels and number of doses was evaluated in mice and rabbits, and IgG antibody responses tested against OMVs and recombinant PorA and FetA proteins. A panel of four isogenic mutants was generated and used to evaluate the relative ability of the vaccine to induce serum bactericidal activity (SBA) against FetA and PorA. Sera from mice were tested in SBA against the four target strains. Results demonstrated that the MenPF-1 OMVs were immunogenic against PorA and FetA in both animal models. Furthermore, the murine antibodies induced were bactericidal against isogenic mutant strains, suggesting that antibodies to both PorA and FetA were functional. The data presented indicate that the MenPF-1 vaccine is a suitable formulation for presenting PorA and FetA OMPs in order to induce bactericidal antibodies, and that proceeding to a Phase I clinical trial with this vaccine candidate is justified.     

Humoral immune responses to a single allele PfAMA1 vaccine in healthy malaria-naïve adults

Plasmodium falciparum: apical membrane antigen 1 (AMA1) is a candidate malaria vaccine antigen expressed on merozoites and sporozoites. The polymorphic nature of AMA1 may compromise vaccine induced protection. The humoral response induced by two dosages (10 and 50 μg) of a single allele AMA1 antigen (FVO) formulated with Alhydrogel, Montanide ISA 720 or AS02 was investigated in 47 malaria-na?ve adult volunteers. Volunteers were vaccinated 3 times at 4 weekly intervals and serum samples obtained four weeks after the third immunization were analysed for (i) Antibody responses to various allelic variants, (ii) Domain specificity, (iii) Avidity, (iv) IgG subclass levels, by ELISA and (v) functionality of antibody responses by Growth Inhibition Assay (GIA). About half of the antibodies induced by vaccination cross reacted with heterologous AMA1 alleles. The choice of adjuvant determined the magnitude of the antibody response, but had only a marginal influence on specificity, avidity, domain recognition or subclass responses. The highest antibody responses were observed for AMA1 formulated with AS02. The Growth Inhibition Assay activity of the antibodies was proportional to the amount of antigen specific IgG and the functional capacity of the antibodies was similar for heterologous AMA1-expressing laboratory strains. Trial registration: ClinicalTrials.gov NCT00730782.     

Intranasal HIV-1-gp160-DNA/gp41 peptide prime-boost immunization regimen in mice results in long-term HIV-1 neutralizing humoral mucosal and systemic immunity

An intranasal DNA vaccine prime followed by a gp41 peptide booster immunization was compared with gp41 peptide and control immunizations. Serum HIV-1-specific IgG and IgA as well as IgA in feces and vaginal and lung secretions were detected after immunizations. Long-term humoral immunity was studied for up to 12 mo after the booster immunization by testing the presence of HIV-1 gp41- and CCR5-specific Abs and IgG/IgA-secreting B lymphocytes in spleen and regional lymph nodes in immunized mice. A long-term IgA-specific response in the intestines, vagina, and lungs was obtained in addition to a systemic immune response. Mice immunized only with gp41 peptides and L3 adjuvant developed a long-term gp41-specific serum IgG response systemically, although over a shorter period (1-9 mo), and long-term mucosal gp41-specific IgA immunity. HIV-1-neutralizing serum Abs were induced that were still present 12 mo after booster immunization. HIV-1 SF2-neutralizing fecal and lung IgA was detectable only in the DNA-primed mouse groups. Intranasal DNA prime followed by one peptide/L3 adjuvant booster immunization, but not a peptide prime followed by a DNA booster, was able to induce B cell memory and HIV-1-neutralizing Abs for at least half of a mouse's life span.     

Immunogenicity and Safety in Adults of a New Chromatographically Purified Vero-cell Rabies Vaccine (CPRV): a Randomized, Double-blind Trial with Purified Vero-cell Rabies Vaccine (PVRV)

Recent improvements in chromatographic purification procedures have made it possible to develop a new chromatographically purified rabies vaccine (CPRV) by further purifying the current rabies vaccine prepared from Vero-cell culture (Verorab; Pasteur Mérieux Connaught). The immunogenicity and safety of primary immunization, followed by a booster at one year, with CPRV was compared to that of the purified Vero cell vaccine (PVRV) in a randomized, double-blind study carried out at four veterinary schools in France. A total of 330 healthy, male and female, first-year veterinary students, aged at least 18 years and who required pre-exposure rabies prophylaxis, were enrolled in this study. Included subjects were randomly assigned either CPRV (n = 163) or PVRV (n = 167) to be given as a primary immunization series of three intramuscular injections (D0, D7, D28), followed by a booster after 1 year (D365). Blood samples for serological analysis were taken at D0 (before first injection), D28, D42, D180, D365 (before booster) and D379. All subjects developed a strong immune response to the primary series, and at D42, all subjects had seroconverted for rabies neutralizing antibody (serum titre > or = 0.5 IU/ml). The rabies virus-neutralizing antibody GMT value at D42 in the CPRV group (23.0 IU/ml) was non-inferior to that in the PVRV group (29.6 IU/ml), according to a one-sided non-inferiority test. While antibody titres tended to decrease over the period of follow-up, at D365 (before booster), 97.5% subjects in the CPRV group and 98.8% of subjects in the PVRV group remained seroconverted. After booster, although the rabies antibody GMT value in the CPRV group was lower than that in the PVRV group, all subjects in both groups were seroconverted, and the difference is probably not clinically important. The incidence of local and systemic reactions tended to decrease with each dose during the primary immunization series, followed by a slight increase after booster (significant time-effect in an exploratory logistic regression analysis). Although mild or moderate local reactions tended to be more frequent after injection with CPRV compared to PVRV, systemic reactions were reported less often (significant group-effects in exploratory logistic regression analyses). One serious adverse event possibly related to vaccine occurred during this study (severe asthenia after the third dose of PVRV). This comparative study in healthy young adults demonstrates that the new chromatographically purified rabies vaccine is as immunogenic as PVRV, and seems to be associated with fewer systemic reactions.     

Comparison of the Immune Responses Induced by Chimeric Alphavirus-Vectored and Formalin-Inactivated Alum-Precipitated Measles Vaccines in Mice

A variety of vaccine platforms are under study for development of new vaccines for measles. Problems with past measles vaccines are incompletely understood and underscore the need to understand the types of immune responses induced by different types of vaccines. Detailed immune response evaluation is most easily performed in mice. Although mice are not susceptible to infection with wild type or vaccine strains of measles virus, they can be used for comparative evaluation of the immune responses to measles vaccines of other types. In this study we compared the immune responses in mice to a new protective alphavirus replicon particle vaccine expressing the measles virus hemagglutinin (VEE/SIN-H) with a non-protective formalin-inactivated, alum-precipitated measles vaccine (FI-MV). MV-specific IgG levels were similar, but VEE/SIN-H antibody was high avidity IgG2a with neutralizing activity while FI-MV antibody was low-avidity IgG1 without neutralizing activity. FI-MV antibody was primarily against the nucleoprotein with no priming to H. Germinal centers appeared, peaked and resolved later for FI-MV. Lymph node MV antibody-secreting cells were more numerous after FI-MV than VEE/SIN-H, but were similar in the bone marrow. VEE/SIN-H-induced T cells produced IFN-γ and IL-4 both spontaneously ex vivo and after stimulation, while FI-MV-induced T cells produced IL-4 only after stimulation. In summary, VEE/SIN-H induced a balanced T cell response and high avidity neutralizing IgG2a while FI-MV induced a type 2 T cell response, abundant plasmablasts, late germinal centers and low avidity non-neutralizing IgG1 against the nucleoprotein.     

Age affects quantity but not quality of antibody responses after vaccination with an inactivated flavivirus vaccine against tick-borne encephalitis

The impairment of immune functions in the elderly (immunosenescence) results in post-vaccination antibody titers that are significantly lower than in young individuals. It is, however, a controversial question whether also the quality of antibodies declines with age. In this study, we have therefore investigated the age-dependence of functional characteristics of antibody responses induced by vaccination with an inactivated flavivirus vaccine against tick-borne encephalitis (TBE). For this purpose, we quantified TBE virus-specific IgG and neutralizing antibody titers in post-vaccination sera from groups of young and elderly healthy adults and determined antibody avidities and NT/ELISA titer ratios (functional activity). In contrast to the quantitative impairment of antibody production in the elderly, we found no age-related differences in the avidity and functional activity of antibodies induced by vaccination, which also appeared to be independent of the age at primary immunization. There was no correlation between antibody avidity and NT/ELISA ratios suggesting that additional factors affect the quality of polyclonal responses, independent of age. Our work indicates that healthy elderly people are able to produce antibodies in response to vaccination with similar avidity and functional activity as young individuals, albeit at lower titers.     

Nonionic block polymer surfactants enhance the avidity of antibodies in polyclonal antisera against Streptococcus pneumoniae type 3 in normal and Xid mice

Avidities of antibody (sub)classes in polyclonal antisera against Streptococcus pneumoniae type 3 (S3) can be (semi) quantitatively determined with a specific inhibition ELISA. A hexasaccharide was isolated from the hydrolyzed S3 capsular polysaccharide and coupled to a protein-carrier. Mixtures containing these conjugates and nonionic block polymer (NBP) surfactants were used for immunization. After various immunizations of these conjugates without NBP the anti-S3 specific antibodies of IgM and IgG2a isotype decreased in both antibody level and avidity. The adjuvants NBP 1501 and L121 not only enhanced the hexasaccharide-protein induced IgM and IgG antibody levels but also clearly increased the avidity of the two antibody (sub)classes IgM and IgG2a. This effect was observed in normal (data not shown) and X-linked immunodefective mice. A maturation of the IgG antibody response was realized by the second immunization with hexasaccharide-protein conjugate whereas the third immunization showed no further increase in antibody level and avidity.     

Mucosal inoculation of Lactobacillus expressing hCGbeta induces an anti-hCGbeta antibody response in mice of different strains

To show that an anti-human chorionic gonadotrophin-beta (hCGbeta) antibody response can be induced by inoculating Lb. expressing hCGbeta through different mucosal pathways in mice of two strains, female BALB/c and C57BL/6 mice were immunized via vaginal, oral or nasal routes with 10(8), 10(9), and 10(10)Lb.hCGbeta (a recombinant Lactobacillus expressing hCGbeta). The mice were immunized twice with a booster in study week 3. An indirect ELISA was used to determine anti-hCGbeta IgG and IgA antibodies in vaginal lavage and serum, obtained from the 2nd to 8th week after the primary immunization. Flow cytometry was used to analyze the lymphocyte proliferation from these tissues, 1 week after the primary immunization. The hCGbeta antigen-specific antibody-secreting cells of spleen, uterus, and vagina were evaluated by enzyme-linked immunospot assay (ELISpot), 2 weeks after the booster. The analysis showed that 10(9) and 10(10)Lb.hCGbeta inoculations induced similar anti-hCGbeta antibody responses, while the three mucosal pathways induced similar antibody responses. The antiserum obtained after boosters with 10(9) and 10(10)Lb. hCGbeta was able to neutralize more than 100 ng/ml hCG antigen, both in BALB/c and C57BL/6 mice. The highest antibody titer induced by vaginal mucosal immunization was stronger than that obtained via the other mucosal pathways. The B cells in the vagina appeared to proliferate after vaginal immunization (P<0.05). The numbers of anti-hCGbeta IgG and IgA antibody-secreting cells in the uterus and vagina were greater than in the spleen. Therefore, the vaginal mucosal route appears to be a better immunization pathway to induce higher anti-hCGbeta antibody levels in the reproductive tract.     

A consideration to immune doses of staphlococcal enterotoxin B to rabbits

Immune doses of staphylococcal enterotoxin B to rabbits were studied by comparing the efficiency of various immunization schedules. It was experienced that even two subcutaneous injections each with such a small dose as 10 mug of enterotoxin B, the primary one with Freund's complete adjuvant and a booster one without adjuvant, could stimulate a rabbit to develop the antibody to a satisfactorily high titer determined by agar gel diffusion and passive hemagglutination.     

Antibody Response and Protection Induced by Immunization with Smooth and Rough Strains in Experimental Salmonellosis

The antibody response of mice to a smooth strain of Salmonella typhimurium was shown previously to be extremely rapid and potent. As measured by the complement-mediated bactericidal reaction, it was also found to be highly specific as well as reproducible. Experiments which studied the effects of antigen type (live or heat-killed), antigen dose, and the route of immunization indicated that the most rapid and highest antibody response was achieved with live, smooth organisms injected by the intraperitoneal route. Living vaccines of rough strains of either S. typhimurium or S. enteritidis induced antibodies directed against the corresponding smooth organisms. The response to the rough strains was apparently due to antibody production rather than to the simple release of preformed natural antibody. The duration of protection conferred by the rough strain vaccines was closely correlated with the endotoxic content of the immunizing strain. Smooth heat-killed vaccines and a rough live vaccine protected against homologous but not heterologous challenge. In contrast, immunization with a smooth live vaccine protected mice against both homologous and heterologous challenge infections. Protection was not due to a local effect in the peritoneal cavity, since mice were also protected against subcutaneous challenge. The secondary antibody response, induced in immunized animals by the virulent challenge infection, was demonstrated to be rapid and potent, and hence a factor to be considered in protection.