Effect of O-acetylation on the antigenicity and glycoconjugate immunogenicity of the Streptococcus pneumoniae serotype 7F capsular polysaccharide.

Streptococcus pneumoniae is a bacterial pathogen causing diseases as severe as pneumonia, sepsis and meningitis. Commercial pneumococcal conjugate vaccines contain the 7F serotype, which is epidemiologically relevant and highly invasive. This serotype contains an O-acetyl group at the internal L-rhamnose of its polysaccharide repeating unit. Herein we report on the role of the O-acetyl moiety of 7F polysaccharide in both antigen recognition and the induction of a protective antibody response against 7F. Fully and partially de-O-acetylated 7F polysaccharides were chemically prepared and compared with the O-acetylated counterpart in their antigenicity and immunogenicity of their tetanus toxoid glycoconjugates. These comparative studies showed a slight but consistent decrease in the antigenicity for the fully de-O-acetylated polysaccharide, but not for the partly de-O-acetylated variant. The glycoconjugates derived from the O-acetylated and the fully de-O-acetylated polysaccharides had similar sizes and polysaccharide-to-protein ratio, and all proved both to be immunogenic and induce opsonophagocytic responses in mice. Nevertheless, the immune response elicited by the O-acetylated glycoconjugate was better in both quantity and quality, proving that the O-acetyl group is not strictly necessary but also not irrelevant for the antigenicity and immunogenicity of the 7F serotype polysaccharide and its glycoconjugates.

SARS-CoV-2 RBD-Tetanus Toxoid Conjugate Vaccine Induces a Strong Neutralizing Immunity in Preclinical Studies.

Controlling the global COVID-19 pandemic depends, among other measures, on developing preventive vaccines at an unprecedented pace. Vaccines approved for use and those in development intend to elicit neutralizing antibodies to block viral sites binding to the host's cellular receptors. Virus infection is mediated by the spike glycoprotein trimer on the virion surface via its receptor binding domain (RBD). Antibody response to this domain is an important outcome of immunization and correlates well with viral neutralization. Here, we show that macromolecular constructs with recombinant RBD conjugated to tetanus toxoid (TT) induce a potent immune response in laboratory animals. Some advantages of immunization with RBD-TT conjugates include a predominant IgG immune response due to affinity maturation and long-term specific B-memory cells. These result demonstrate the potential of the conjugate COVID-19 vaccine candidates and enable their advance to clinical evaluation under the name SOBERANA02, paving the way for other antiviral conjugate vaccines.

Repeat-Dose Toxicity Study Using the AFPL1-Conjugate Nicotine Vaccine in Male Sprague Dawley Rats.

Tobacco smoking is the cause of 20% of Canadian deaths per year. Nicotine vaccines present a promising alternative to traditional smoking cessation products, but to date, no vaccine has been able to move through all phases of clinical trials. We have previously demonstrated that the AFPL1-conjugate nicotine vaccine does not induce systemic or immunotoxicity in a mouse model and that a heterologous vaccination approach is more advantageous than the homologous routes to inducing mucosal and systemic anti-nicotine antibodies. The purpose of this study was to confirm the safety profile of the vaccine in a repeat-dose toxicity study. The heterologous vaccination strategy was again used, and Sprague Dawley rats were administered a dose five times greater than in our previous studies. Physiological conditions, food and water consumption, body temperature, injection site inflammation, relative weights of organs, histopathology, and blood chemistry and hematology were evaluated during the course of the vaccination period to determine the safety of the vaccine. The AFPL1-conjugate nicotine vaccine did not induce clinically relevant changes or induce symptoms that would be associated with toxicity, making it a promising candidate for future investigations.

Una vacuna de vesículas de membrana externa de Vibrio cholerae es aún una promesa: Caracterización proteómica / Outer membrane vesicle vaccine from Vibrio cholerae is still a promise: Proteomic characterization

Las epidemias de cólera afectan a un gran número de países africanos, asiáticos y del Caribe. Los cambios climatológicos y las constantes migraciones hacen que esta enfermedad se extienda, por lo que resulta necesario disponer de vacunas protectoras. En el presente trabajo se caracterizó una nueva vacuna de vesículas de membrana externa (VMEs) obtenidas de Vibrio cholerae O1 biotipo El Tor serotipo Ogawa cepa C7258, en el Instituto Finlay de vacunas (Cuba), a través de métodos proteómicos. Se identificaron 53 proteínas presentes en las VME (4 proteínas por banda electroforética) separadas por electroforesis unidimensional (1D) y digeridas con tripsina. Los fragmentos obtenidos fueron separados por cromatografía líquida de alta resolución (HPLC) acoplada a espectrometría de masa, secuenciados e identificados mediante bases de datos de proteínas Swiss-Prot y TrEMBL. El patrón proteico obtenido presentó algunas de las proteínas (12 proteínas citoplasmáticas y 5 proteínas de membrana externa) sugeridas dentro del proteoma de buena calidad para candidatos vacunales. Se estudiaron las mejores condiciones para la separación de las proteínas a través de electroforesis bidimensional. Las VME evaluadas cuentan con una composición fundamentada en proteínas necesarias para garantizar una respuesta inmune que proteja contra Vibrio cholerae O1 biotipo El Tor serotipo Ogawa.

Cholera epidemics affect a large number of African, Asian and Caribbean countries. The climate changes and the constant migrations cause this disease to spread, making it is necessary to obtain protective vaccines. In the present work, a new vaccine of outer membrane vesicles (OMV) from V. cholerae O1 El Tor biotype Ogawa serotype strain C7258 at Finlay Institute of vaccines (Cuba) was characterized by proteomic methods. A total of 53 proteins present in the OMV (approximate ratio of 4 proteins by electrophoresis band) were identified, separated by one dimension electrophoresis and digested by tripsin method. The fragments were separated by high performance liquid chromatography (HPLC) coupled to mass spectrometry, sequenced and identified, using Swiss-Prot and TrEMBL protein databases. The pattern showed some proteins (12 cytoplasmic proteins and 5 outer membrane proteins) suggested within the highest quality proteome for vaccine candidate. The best conditions for proteins separation by two dimension electrophoresis were studied. The OMV composition was based on proteins described to the immunity response and protection against V. cholerae O1 El Tor biotype Ogawa serotype.

As epidemias de cólera afetam um grande número de países africanos, asiáticos e caribenhos. As mudanças climáticas e as constantes migrações fazem com que esta doença se espalhe, portanto é necessário ter vacinas protectoras. No presente trabalho, uma nova vacina de vesículas de membrana externa (VMEs) obtidas de Vibrio cholerae 01 biotipo El Tor sorotipo Ogawa cepa C7258, no Instituto de Vacinas Finlay (Cuba), através de métodos proteômicos. Foram identificadas 53 proteínas presentes nas VME (4 proteínas por banda eletroforética) separadas por eletroforese unidimensional (1D) e digeridas com tripsina. Os fragmentos obtidos foram separados por cromatografia de alta resolução (HPLC) acoplada a espectrometria de massa, sequenciados e identificados usando bancos de dados de proteínas Swiss-Prot e TrEMBL. O padrão proteico obtido apresentou algumas das proteínas (12 proteínas citoplasmáticas e 5 proteínas de membrana externa) sugeridas dentro do proteoma de boa qualidade para candidatos vacinais. As melhores condições para a separação de proteínas através de eletroforese bidimensional foram estudadas. As VME avaliados possuem uma composição baseada em proteínas necessárias para garantir uma resposta imune que proteja contra Vibrio cholerae O1 biotipo El Tor sorotipo Ogawa.

Mucosal and systemic immune responses induced by a single time vaccination strategy in mice.

Vaccination is considered by the World Health Organization as the most cost-effective strategy for controlling infectious diseases. In spite of great successes with vaccines, many infectious diseases are still leading killers, because of the inadequate coverage of many vaccines. Several factors have been responsible: number of doses, high vaccine reactogenicity, vaccine costs, vaccination policy, among others. Contradictorily, few vaccines are of single dose and even less of mucosal administration. However, more common infections occur via mucosa, where secretory immunoglobulin A plays an essential role. As an alternative, we proposed a novel protocol of vaccination called Single Time Vaccination Strategy (SinTimVaS) by immunizing 2 priming doses at the same time: one by mucosal route and the other by parenteral route. Here, the mucosal and systemic responses induced by Finlay adjuvants (AF Proteoliposome 1 and AF Cochleate 1) implementing SinTimVaS in BALB/c mice were evaluated. One intranasal dose of AF Cochleate 1 and an intramuscular dose of AF Proteoliposome 1 adsorbed onto aluminum hydroxide, with bovine serum albumin or tetanus toxoid as model antigens, administrated at the same time, induced potent specific mucosal and systemic immune responses. Also, we demonstrated that SinTimVaS using other mucosal routes like oral and sublingual, in combination with the subcutaneous route elicits immune responses. SinTimVaS, as a new immunization strategy, could increase vaccination coverage and reduce time-cost vaccines campaigns, adding the benefits of immune response in mucosa.

Combined meningococcal serogroup A and W135 outer-membrane vesicles activate cell-mediated immunity and long-term memory responses against non-covalent capsular polysaccharide A.

Outer-membrane vesicles (OMVs) have inherent adjuvant properties, and many vaccines use OMV as vaccine components. Utilizing the adjuvant properties of OMV could lead to the formulation of vaccines that are less expensive and potentially more immunogenic than covalently conjugated polysaccharide vaccines. We evaluated the adjuvant effect in Balb/c mice of combinations of OMV from Neisseria meningitidis serogroup A and W135 as compared to that of the non-covalently conjugated capsular polysaccharide A. Both antigens were adsorbed onto aluminum hydroxide. The mice were given a booster dose of plain polysaccharide A to stimulate an immunologic memory response. Subclasses determination and cytokine assays demonstrated the capacity of OMV to induce a IgG2a/IgG2b isotype profile and IFN-γ production, suggesting the induction of a Th1 pattern immune response. Lymphoproliferative responses to OMVs were high, with affinity maturation of antibodies observed. Bactericidal titers after the booster dose were also observed. Memory B cells and long-term memory T cells were also detected. The results of this study indicate that combined meningococcal serogroup A and W135 OMV can activate cell-mediated immunity and induce a long-term memory response.

A proteoliposome formulation derived from Bordetella pertussis induces protection in two murine challenge models.

Whooping cough remains a health problem despite high vaccination coverage. It has been recommended that development of new strategies provide long-lasting immunity. The aim of this work was to evaluate the potential of proteoliposomes (PL) extracted from Bordetella pertussis as a vaccine candidate against whooping cough. The size of the B. pertussis PL was estimated to be 96.7 ± 50.9 nm by Scanning Correlation Spectroscopy and the polydispersity index was 0.268. Western blots using monoclonal antibodies revealed the presence of pertussis toxin, pertactin, and fimbriae 3. The Limulus Amebocyte Lisate (LAL) assay showed endotoxin levels lower than those reported for whole cell pertussis licensed vaccines, while the Pyrogen Test indicated 75 ng/mL/Kg. The PL showed high protection capacity in mouse challenge models. There was 89.7% survival in the intracerebral challenge and total reduction of the number of CFU in the intranasal challenge. No significant differences (p > 0.05) were observed between mice immunized with B. pertussis PL and the Cuban DTwP vaccine, whichever challenge model used. These results encouraged us to continue the development of the B. pertussis PL as a component of a new combined vaccine formulated with tetanus and diphtheria toxoids or as a booster dose for adolescents and adults.

A novel method to screen genomic libraries that combines genomic immunization with the prime-boost strategy.

We employed a prime-boost regimen in combination with the expression library immunization protocol to improve the protective effectiveness of a genomic library used as immunogen. To demonstrate the feasibility of this novel strategy, we used as a prime a serogroup B Neisseria meningitidis random genomic library constructed in a eukaryotic expression vector. Mice immunized with different fractions of this library and boosted with a single dose of meningococcal outer membrane vesicles elicited higher bactericidal antibody titers compared with mice primed with the empty vector. After the boost, passive administration of sera from mice primed with two of these fractions significantly reduced the number of viable bacteria in the blood of infant rats challenged with live N. meningitidis. The method proposed could be applied to the identification of subimmunogenic antigens during vaccine candidate screening by employing expression library immunization.

Identification by genomic immunization of a pool of DNA vaccine candidates that confer protective immunity in mice against Neisseria meningitidis serogroup B.

We have shown previously that expression library immunization is viable alternative approach to induce protective immunity against Neisseria meningitidis serogroup B. In this study we report that few rounds of library screening allow identification of protective pools of defined antigens. A previously reported protective meningococcal library (L8, with 600 clones) was screened and two sub-libraries of 95 clones each were selected based on the induction of bactericidal and protective antibodies in BALB/c mice. After sequence analysis of each clone within these sub-libraries, we identified a pool of 20 individual antigens that induced protective immune responses in mice against N. meningitidis infection, and the observed protection was associated with the induction of bactericidal antibodies. Our studies demonstrate for the first time that ELI combined with sequence analysis is a powerful and efficient tool for identification of candidate antigens for use in a meningococcal vaccine.

Adjuvant properties of lipopolysaccharide from Neisseria meningitidis serogroup B detoxified and conjugated with tetanus toxoid.

We evaluated the adjuvant properties and toxicity of purified Neisseria meningitidis serogroup B lipopolysaccharide (LPS) conjugated with tetanus toxoid (TT) using a new method of conjugation to obtain amine groups in the polysaccharide structure. The endotoxic activity of treated LPS was reduced 2400 times as determined by Limulus amoebocyte assay and no mortality was observed in Balb/c mice inoculated with detoxified LPS versus 100% mortality in native LPS inoculated mice. The conjugated LPS-TT elicited in mice higher anti-TT IgG2a and IgG1 than unconjugated TT. In addition, high levels of anti-LPS IgG and IgG subclasses were detected in sera. These results evidence the adjuvant activity of detoxified LPS and may suggest that the conjugation to TT changes the LPS immune response from thymus-independent to thymus-dependent.

The effect of the administration of human gamma globulins in a model of BCG infection in mice.

The effect of the administration of a commercial preparation of human gamma globulins has been evaluated in a mouse model of intranasal infection with BCG. First, we demonstrated the passage of specific antibodies to saliva and lung lavage following the intranasal or intraperitoneal administration to mice of human gamma globulins. This treatment of mice inhibited BCG colonization of the lungs (p < 0.01). A similar inhibitory effect was observed after infection of mice with gamma globulin opsonized BCG organisms (p < 0.01). These results are relevant for the development of new strategies for the control and treatment of tuberculosis.