Recombinant Mycobacterium bovis BCG expressing pertussis toxin subunit S1 induces protection against an intracerebral challenge with live Bordetella pertussis in mice

The recent development of acellular pertussis vaccines has been a significant improvement in the conventional whole-cell diphtheria-pertussis-tetanus toxoid vaccines, but high production costs will limit its widespread use in developing countries. Since Mycobacterium bovis BCG vaccination against tuberculosis is used in most developing countries, a recombinant BCG-pertussis vaccine could be a more viable alternative. We have constructed recombinant BCG (rBCG) strains expressing the genetically detoxified S1 subunit of pertussis toxin 9K/129G (S1PT) in fusion with either the beta-lactamase signal sequence or the whole beta-lactamase protein, under control of the upregulated M. fortuitum beta-lactamase promoter, pBlaF*. Expression levels were higher in the fusion with the whole beta-lactamase protein, and both were localized to the mycobacterial cell wall. The expression vectors were relatively stable in vivo, since at two months 85% of the BCG recovered from the spleens of vaccinated mice maintained kanamycin resistance. Spleen cells from rBCG-S1PT-vaccinated mice showed elevated gamma interferon (IFN-gamma) and low interleukin-4 (IL-4) production, as well as increased proliferation, upon pertussis toxin (PT) stimulation, characterizing a strong antigen-specific Th1-dominant cellular response. The rBCG-S1PT strains induced a low humoral response against PT after 2 months. Mice immunized with rBCG-S1PT strains displayed high-level protection against an intracerebral challenge with live Bordetella pertussis, which correlated with the induction of a PT-specific cellular immune response, reinforcing the importance of cell-mediated immunity in the protection against B. pertussis infection. Our results suggest that rBCG-expressing pertussis antigens could constitute an effective, low-cost combined vaccine against tuberculosis and pertussis.

An improved whole cell pertussis vaccine with reduced content of endotoxin

An improved whole cell pertussis vaccine, designated as Plow, which is low in endotoxicity due to a chemical extraction of lipo-oligosaccharide (LOS) from the outer membrane, was evaluated for safety, immunogenicity and potency, comparatively to a traditional whole cell pertussis vaccine. Current whole cell pertussis vaccines are effective but contain large quantities of endotoxin and consequently display local and systemic adverse reactions after administration. Endotoxin is highly inflammatory and contributes considerably to the reactogenicity as well as the potency of these vaccines. In contrast, acellular pertussis vaccines hardly contain endotoxin and are significantly less reactogenic, but their elevated costs limit their global use, especially in developing countries. In this paper, bulk products of Plow and a traditional whole cell vaccine, formulated as plain monocomponents or combined with diphtheria and tetanus toxoids (DTPlow or DTP, respectively) were compared by in vitro and in vivo assays. Chemical extraction of LOS resulted in a significant decrease in endotoxin content (20%) and a striking decline in endotoxin related toxicity (up to 97%), depending on the used in vitro or in vivo test. The LOS extraction did not affect the integrity of the product and, more importantly, did not affect the potency and/or stability of DTPlow. Moreover, hardly any differences in antibody and T-cell responses were observed. The development of Plow is a significant improvement regarding the endotoxicity of whole cell pertussis vaccines and therefore a promising and affordable alternative to currently available whole cell or acellular pertussis vaccines for developing countries.

Blocking FGF2 with a new specific monoclonal antibody impairs angiogenesis and experimental metastatic melanoma, suggesting a potential role in adjuvant settings

Compelling evidence suggests that fibroblast growth factor 2 (FGF2), overexpressed in melanomas, plays an important role in tumor growth, angiogenesis and metastasis. In this study, we evaluated the therapeutic use of a new anti-FGF2 monoclonal antibody (mAb), 3F12E7, using for that the B16-F10 melanoma model. The FGF2 neutralizing effect of this antibody was certified by in vitro assays, which allowed the further track of its possible in vivo application. 3F12E7 mAb could be retained in B16-F10 tumors, as shown by antibody low-pH elution and nuclear medicine studies, and also led to reduction in number and size of metastatic foci in lungs, when treatment starts one day after intravenous injection of B16-F10 cells. Such data were accompanied by decreased CD34(+) tumor vascular density and impaired subcutaneous tumor outgrowth. Treatments starting one week after melanoma cell intravenous injection did not reduce tumor burden, remaining the therapeutic effectiveness restricted to early-adopted regimens. Altogether, the presented anti-FGF2 3F12E7 mAb stands as a promising agent to treat metastatic melanoma tumors in adjuvant settings.

Production of H5N1 (NIBRG-14) inactivated whole virus and split virion influenza vaccines and analysis of immunogenicity in mice using different adjuvant formulations

Consecutive lots of H5N1 (A/Vietnam/1194/2004 - NIBRG-14) split virion and whole virus vaccines were produced in a pilot-scale laboratory. The average yields of vaccine doses (15 microg HA) per egg were 0.57 doses for H5N1 split virion vaccine and 1.12 for H5N1 whole virus vaccine, compared to 2.09 doses for the seasonal H3N2 split virion vaccine. H5N1 split virion vaccine lots complied with WHO protein content criteria, while some lots of the H5N1 whole virus vaccine showed protein content per dose higher than the limit established. All lots of both vaccines showed ovalbumin (OVA) concentration below the recommended limit. Dose sparing strategies using adjuvant formulations using aluminum hydroxide (Al(OH)(3)) and monophosphoryl lipid A (MPLA) from Bordetella pertussis were tested in mice. Both 3.75 microg HA and 7.5 microg HA of H5N1 split virion vaccine with Al(OH)(3) or Al(OH)(3) plus MPLA in aqueous suspension showed higher hemagglutination-inhibition (HAI) titers when compared to the same vaccine dose without any adjuvant. Immunization with the H5N1 inactivated whole virus vaccine was also performed using 3.75 microg HA and HAI titers were higher than those induced by the split virion vaccine. Moreover, the use of Al(OH)(3) with MPLA as an emulsion induced a further increase in HAI titers.

Neonatal immunization with a single dose of recombinant BCG expressing subunit S1 from pertussis toxin induces complete protection against Bordetella pertussis intracerebral challenge

The currently used pertussis vaccines are highly efficacious; however, neonates are susceptible to whooping cough up to the sixth month. In agreement, DTP-immunized neonate mice were not protected against intracerebral challenge with Bordetella pertussis. Neonate mice immunized with either DTP or a recombinant-BCG strain expressing the genetically detoxified S1 subunit of pertussis toxin do not show a humoral immune response against PT. On the other hand, rBCG-Pertussis induces higher PT-specific IFN-gamma production and an increase in both IFN-gamma(+) and TNF-alpha(+)-CD4(+)-T cells than the whole cell pertussis vaccine and confers protection against a lethal intracerebral challenge with B. pertussis.

Vitamins as influenza vaccine adjuvant components

A number of adjuvant formulations were assayed in mice immunized with 3.75 µg of A/California/7/2009 (H1N1) pdm09 influenza vaccine with vitamins A, D and/or E in emulsions or B2 and/or B9 combined with Bordetella pertussis MPLA and/or alum as adjuvants. Squalene was used as positive control, as well as MPLA with alum. The immune response was evaluated by a panel of tests, including a hemagglutination inhibition (HAI) test, ELISA for IgG, IgG1, and IgG2a and IFN-γ, IL-2, IL-6 and IL-10 quantification in splenocyte culture supernatant after stimulus with influenza antigen. Immunological memory was evaluated using a 1/10 dose booster 60 days after the first immunization followed by assessment of the response by HAI, IgG ELISA, and determination of the antibody affinity index. The highest increases in HAI, IgG1 and IgG2a titers were obtained with the adjuvant combinations containing vitamin E, or the hydrophilic combinations containing MPLA and alum or B2 and alum. The IgG1/IgG2a ratio indicates that the response to the combination of B2 with alum would have more Th2 character than the combination of MPLA with alum. In an assay to investigate the memory response, a significant increase in HAI titer was observed with a booster vaccine dose at 60 days after immunization with vaccines containing MPLA with alum or B2 with alum. Overall, of the 27 adjuvant combinations, MPLA with alum and B2 with alum were the most promising adjuvants to be evaluated in humans.

Adjuvant and immunogenic activities of the 73kDa N-terminal alpha-domain of BrkA autotransporter and Cpn60/60kDa chaperonin of Bordetella pertussis

A soluble fraction obtained from Bordetella pertussis was evaluated as adjuvant for the pertussis component of the Diphtheria-Pertussis-Tetanus (DPT) vaccine. High levels of antibodies were induced, and a 78% protection rate of mice challenged with live B. pertussis was observed. Two proteins were identified as the 73 kDa N-terminal alpha-domain of BrkA autotransporter protein and the Cpn60/60 kDa chaperonin. Both stimulated antibodies against pertussis and induced a 42% protection rate against the challenge. IgG1 and IgG2a were stimulated suggesting that the immune response could be modulated to produce Th1 or Th2.

Passive acquisition of protective antibodies reactive with Bordetella pertussis in newborns via placental transfer and breast-feeding

Although acquisition of anti-pertussis antibodies by the newborn via placental transfer has been demonstrated, a subsequent recrudescence of pertussis infection is often observed, particularly in infants. The present study investigated the passive transfer of anti-pertussis IgG and IgA antibodies to term newborns and their ability to neutralize bacterial pathogenicity in an in vivo experimental model using mice intracerebrally challenged with viable Bordetella pertussis. Forty paired samples of maternal/umbilical cord sera and colostrum were obtained. Anti-pertussis antibodies were analysed by immunoenzymatic assay and by Immunoblotting. Antibody neutralizing ability was assessed through intracerebral B. pertussis challenges in mice. Anti-pertussis IgG titres were equivalent in both maternal and newborn sera (medians = 1:225 and 1:265), with a transfer rate of 118%. The colostrum samples had variable specific IgA titres (median = 1:74). The immunoblotting assays demonstrated identical recognition profiles of paired maternal and newborn serum pools but different bacterial recognition intensities by colostrum pools. In the animal model, significant differences were always observed when the serum and colostrum samples and pools were compared with the positive control (P < 0.05). Unlike samples with lower anti-pertussis titres, samples with high titres showed protective capacities above 50%. Pertussis-absorbed serum and colostrum pools protected 30% of mice and purified IgG antibodies protected 65%. Both pooled and single-sample protective abilities were correlated with antibody titres (P < 0.01). Our data demonstrated the effectiveness of anti-pertussis antibodies in bacterial pathogenesis neutralization, emphasizing the importance of placental transfer and breast-feeding in protecting infants against respiratory infections caused by Bordetella pertussis.

Human Recombinant Fab Fragment Neutralizes Shiga Toxin Type 2 Cytotoxic Effects in vitro and in vivo

Shiga toxin (Stx) producing Escherichia coli (STEC) is responsible for causing hemolytic uremic syndrome (HUS), a life-threatening thrombotic microangiopathy characterized by thrombocytopenia, hemolytic anemia, and acute renal failure after bacterially induced hemorrhagic diarrhea. Until now, there has been neither an effective treatment nor method of prevention for the deleterious effects caused by Stx intoxication. Antibodies are well recognized as affinity components of therapeutic drugs; thus, a previously obtained recombinant human FabC11:Stx2 fragment was used to neutralize Stx2 in vitro in a Vero cell viability assay. Herein, we demonstrated that this fragment neutralized, in a dose-dependent manner, the cytotoxic effects of Stx2 on human glomerular endothelial cells, on human proximal tubular epithelial cells, and prevented the morphological alterations induced by Stx2. FabC11:Stx2 protected mice from a lethal dose of Stx2 by toxin-antibody pre-incubation. Altogether, our results show the ability of a new encouraging molecule to prevent Stx-intoxication symptoms during STEC infection.

Conformational stability and antibody response to the 18kDa heat-shock protein formulated into different vehicles

Protein stability is one of the most important obstacles for successful formulation in the development of new-generation vaccines. Here, the 18kDa heat-shock protein (18kDa-hsp) was chemically modified though conjugation with bovine serum albumin or by esterification with N-hydroxysuccinimide ester of palmitic acid. The biologically active conformation of the protein was preserved after chemical modification. The immune responses to the recombinant 18kDa-hsp from Mycobacterium leprae were studied in different presentations: free, copolymerized with bovine serum albumin in aggregates (18kDa-hsp-BSA), and either surface linked to liposomes or entrapped into liposomes. Measuring the antibody production of immunized genetically selected mice has compared the adjuvant effects of liposomes and proteic copolymer. Among the two liposome preparations, the strongest response was obtained with the surface-exposed antigen-liposomes. The copolymer 18kDa-hsp-BSA conferred a high titer of antibody in injected mice, and persisted 70 d after immunization. This approach should prove very useful for designing more effective vaccines by using 18kDa-hsp as carrier protein.

Poly-lactide-co-glycolide microparticle sizes: a rational factorial design and surface response analysis

Microsphere size is a primary determinant of solute release velocity. We present here a rational way for producing PLGA microspheres with different and controlled sizes. The following process variables were studied: Stirring velocity during the second emulsion step, dispersed and continuous phases volume ratio, and poly(vinyl alcohol) concentration in the continuous phase. A full factorial experimental design 2(3) with triplicate at the central point was used to determine the influence of variables on PLGA microsphere mean size. The stirring velocity and poly(vinyl alcohol) concentration were the main variables at 0.95 significance level. An influence of PVA and stirring velocity on microspheres size is observed, there is no correlation for DP/CP volume ratio on size of microspheres. By combining the two variables--the stirring velocity and poly(vinyl alcohol) concentration, the surface response was analyzed. The increase of poly(vinyl alcohol) concentration with concomitant increase on stirring velocity produced microspheres with the lower sized. In contrast the lower poly(vinyl alcohol) concentration and the lower stirring velocity used produced the higher microspheres sized. Uniformly spherical and smooth microspheres (4-15 microm of diameter) were obtained. No significant difference was observed on Ponca S loading within the experimental region. Our results open the possibility of formulating PLGA microspheres with custom sizes performing a minimum of experiments as required for specific applications.

Pneumococcal Surface Protein A does not affect the immune responses to a combined diphtheria tetanus and pertussis vaccine in mice

The Pneumococcal Surface Protein A (PspA) is a promising candidate for the composition of a protein vaccine against Streptococcus pneumoniae. We have previously shown that the whole cell Bordetella pertussis vaccine (wP) is a good adjuvant to PspA, inducing protective responses against pneumococcal infection in mice. In Brazil, wP is administered to children, formulated with diphtheria and tetanus toxoids (DTPw) and aluminum hydroxide (alum) as adjuvant. A single subcutaneous dose of PspA5-DTPlow (a formulation containing PspA from clade 5 and a new generation DTPw, containing low levels of B. pertussis LPS and Alum) induced high levels of systemic anti-PspA5 antibodies in mice and conferred protection against respiratory lethal challenges with two different pneumococcal strains. Here we evaluate the mucosal immune responses against PspA5 as well as the immune responses against the DTP antigens in mice vaccinated with PspA5-DTPlow. Subcutaneous immunization of mice with PspA5-DTPlow induced high levels of anti-PspA5 IgG in the airways but no IgA. In addition, no differences in the influx of cells to the respiratory mucosa, after the challenge, were observed in vaccinated mice, when compared with control mice. The levels of circulating anti-pertussis, -tetanus and -diphtheria antibodies were equivalent in mice vaccinated with DTPlow or PspA5-DTPlow. Antibodies induced by DTPlow or PspA5-DTPlow showed similar ability to neutralize the cytotoxic effects of the diphtheria toxin on Vero cells. Furthermore, combination with PspA5 did not affect protection against B. pertussis and tetanus toxin challenges in mice. Our results support the proposal for a combined PspA-DTP vaccine.

Large unilamellar vesicles as trehalose-stabilised vehicles for vaccines: storage time and in vivo studies

Liposomes, as a pharmaceutical formulation must display a long shelf life. The recombinant heat-shock protein from Mycobacterium leprae (18-kDa hsp) or its N-acylated derivative, when entrapped within or externally associated with large unilamellar vesicles, acts as a T-epitope source. Freeze-fracture electron microscopy shows unequivocally that trehalose avoids aggregation and fusion of these vesicles. Formulations containing trehalose retained up to 98% of the entrapped protein. The highest antibody level is obtained with formulations containing trehalose. The adjuvant effect depends on the liposomal membrane integrity.

Heat shock protein micro-encapsulation as a double tool for the improvement of new generation vaccines

The modern vaccinology encompasses the recombinant DNA technology, protein and carbohydrate chemistry to obtain safe molecularly defined vaccines. Nevertheless most of the vaccines are poorly immunogenic because a large number of antigens are membrane proteins and consequently they are not present in their active conformation in the vaccine. Others are not as potent because they contain only B epitopes and therefore, cannot stimulate cellular memory. We have been studying the characteristics of the recombinant heat shock protein 18kDa-hsp from Mycobacterium leprae as an alternative carrier protein with a T epitope source to enhance the activity of these second generation vaccines. Here we proved that the 18kDa-hsp acted as carrier, without masking the activity of the carried antigen, with similar immune stimulatory effect when compared with ODN1668. Supramolecular aggregates of 18kDa-hsp and Mice serum albumin (MSA) were obtained using glutaraldehyde as cross linker. The Neisseria meningitides serogroup C polysaccharide (PSC, a B epitope) and the carrier protein 18kDa-hsp were co-encapsulated within Soybean phosphatidylcholine liposomes (SPC: Cho : alpha-Toc, 22 : 5 : 0.18 molar ratio, respectively). These liposomes were prepared in MPB buffer (20 mM phosphate, 295 mM mannitol pH 7.2) in the presence or absence of the ODN1668, TCCATGACGTTCCTGATGCT. When mice were injected with 18kDa-hsp-MSA no antibody against the MSA was observed. This means that the 18kDa-hsp acted as carrier, without masking the carried protein immune activity. Stable liposomes of 150 nm were obtained using mannitol as a cryoprotector. Genetically selected mice when injected with liposomes containing PSC and 18kDa-hsp displayed an antibody titer of 12. In contrast, in those mice injected with free PSC there was no response. The 18kDa-hsp adjuvant effect on the PSC liposomal formulation was comparable to that observed when ODN1668 was co-encapsulated with PSC. Confirming our expectations we observed that the formulation containing 18kDa-hsp conferred a memory response to the carried antigen--the Neisseria meningitidis serogroup C polysaccharide.

Comparative analysis of the intracerebral mouse protection test and serological method for potency assays of pertussis component in DTP vaccine

The aim of this study was to compare the PSPT standardized in-house as an alternative to MPT for potency assays of pertussis component. Statistical analyses have showed similar pertussis potency values when PSPT was compared to MPT. Significant correlation between the potency results obtained by in vivo and in vitro assays was also been observed. Results by PSPT have demonstrated reproducibility and accuracy for potency pertussis control and this approach has been considered promising for use at least during the steps of production.

The Deleterious Effects of Shiga Toxin Type 2 Are Neutralized In Vitro by FabF8:Stx2 Recombinant Monoclonal Antibody

Hemolytic Uremic Syndrome (HUS) associated with Shiga-toxigenic Escherichia coli (STEC) infections is the principal cause of acute renal injury in pediatric age groups. Shiga toxin type 2 (Stx2) has in vitro cytotoxic effects on kidney cells, including human glomerular endothelial (HGEC) and Vero cells. Neither a licensed vaccine nor effective therapy for HUS is available for humans. Recombinant antibodies against Stx2, produced in bacteria, appeared as the utmost tool to prevent HUS. Therefore, in this work, a recombinant FabF8:Stx2 was selected from a human Fab antibody library by phage display, characterized, and analyzed for its ability to neutralize the Stx activity from different STEC-Stx2 and Stx1/Stx2 producing strains in a gold standard Vero cell assay, and the Stx2 cytotoxic effects on primary cultures of HGEC. This recombinant Fab showed a dissociation constant of 13.8 nM and a half maximum effective concentration (EC₅₀) of 160 ng/mL to Stx2. Additionally, FabF8:Stx2 neutralized, in different percentages, the cytotoxic effects of Stx2 and Stx1/2 from different STEC strains on Vero cells. Moreover, it significantly prevented the deleterious effects of Stx2 in a dose-dependent manner (up to 83%) in HGEC and protected this cell up to 90% from apoptosis and necrosis. Therefore, this novel and simple anti-Stx2 biomolecule will allow further investigation as a new therapeutic option that could improve STEC and HUS patient outcomes.

ELISA and modified toxin-binding inhibition test for quality control of the clostridial vaccine processes

This study aimed to assess and standardize the ELISA and modified ToBI test in vitro methods in order to verify the potency of epsilon toxicoid in comparison with the in vivo TCP method. The following epsilon toxoids were used: NIBSC standard from batches 375/07, 532/08, 551/08, 373/07 and 378/07. These were evaluated using a TCP test, ELISA and ToBI tests. The results indicate that the correlation ratio between the dilutions of standard NIBSC toxicoid and absorbance values of 89.44% obtained with the ELISA method support the use of the curve to evaluate epsilon toxoids. However, it was observed that the absorbance values were similar for all toxoids, thus presenting no significant difference between higher and lower concentration toxoids. For the ToBI test, the correlation ratio of 96.76, obtained in the curve pattern, demonstrates the effectiveness of the curve to be used in the epsilon toxoid evaluation. The correlation ratio between the titration degrees of toxoids obtained through TCP and ToBI tests was higher than 90%. It is concluded that the type of ELISA test used does present discriminative power for toxoids with different concentrations, which does not support the use of this technique for such a purpose. The ToBI test can be used as a screening method for it is sensitive and effective to detect epsilon toxicoid produced by C. perfringens type D.

Correlation between ToBI test and in vivo titration for diphtheria and tetanus

Alternatives to animal testing for quality control of biologicals have been a goal since 1959. Instituto Butantan has been developing such methods for quality control of biologicals for human use (vaccines and hyperimmune equine sera) for the last 13 years. In this paper we compare the modified ToBI test and the in vivo seroneutralization test to assess immunogenicity of diphtheria and tetanus vaccines and hyperimmune sera. Data from the last 10 years were statistically analyzed to compare the results for in vivo and in vitro titrations (diphtheria, n = 525 and tetanus, n = 455). The agreement between the tests depended on the serum titer range. For both diphtheria and tetanus components, the correlation and concordance coefficient was higher as the serum titer increased. Overall, the in vitro/in vivo titer ratio did not vary systematically over the range of measurements. These results indicate that although the in vitro ToBI test is not completely able to replace the in vivo serum titration, it is a useful tool to guide the tests during the production process, which can reduce the number of animals used for lot release.