Household survey of hepatitis B vaccine coverage among Brazilian children

We conducted a multi-stage household cluster survey to calculate hepatitis B vaccine coverage among children 18-30 months of age in 27 Brazilian cities. Hepatitis B vaccine is administered at birth, 1 month and 6 months of age by Brazil`s national immunization program. Among 17,749 children surveyed, 40.2% received a birth dose within one day of birth, 94.8% received at least one dose of hepatitis B vaccine, and 86.7% completed the three-dose series by 12 months of age. Increased coverage with the birth dose and administration of hepatitis B in combination with diphtheria-tetanus-pertussis-Haemophilus influenzae type b antigens could improve protection against hepatitis B. (C) 2009 Elsevier Ltd. All rights reserved.

Population-Based Multicentric Survey of Hepatitis B Infection and Risk Factor Differences among Three Regions in Brazil

This multicentric population-based study in Brazil is the first national effort to estimate the prevalence of hepatitis B (HBV) and risk factors in the capital cities of the Northeast. Central-West, and Federal Districts (2004-2005). Random multistage cluster sampling was used to select persons 13-69 years of age. Markers for HBV were tested by enzyme-linked immunosorbent assay. The HBV genotypes were determined by sequencing hepatitis B surface antigen (HBsAg). Multivariate analyses and simple catalytic model were performed. Overall. 7,881 persons were inculded < 70% were not vaccinated. Positivity for HBsAg was less than 1% among non-vaccinated persons and genotypes A, D, and F co-circulated. The incidence of infection increased with age with similar force of infection in all regions. Males and persons having initiated sexual activity were associated with HBV infection in the two settings: healthcare jobs and prior hospitalization were risk factors in the Federal District. Our survey classified these regions as areas with HBV endemicity and highlighted the risk factors differences among the settings.

Prevalence of hepatitis B and C serological markers among first-time blood donors in Brazil: A multi-center serosurvey

Little data are available on the seroprevalence of, and risk factors for hepatitis B and C viruses (HBV and HCV) infection in Latin American countries. A multi-center serosurvey was conducted among 3,598 first-time blood donors (65% men) from Sao Paulo, Salvador and Manaus in Brazil. The gender-specific seroprevalences of antibodies against hepatitis B core antigen (anti-HBc) and of the hepatitis B surface antigen (HBsAg) in anti-HBc-positive sera were measured, and risk factors analyzed by gender. The gender-specific seroprevalences of antibodies against HCV (anti-HCV) were measured, but risk factors for HCV were not determined. Anti-HBc and HBsAg seroprevalences were not significantly different in men [101/2,341 (4.31%) and 4/2,229 (0.18%), respectively] and women [65/1,237 (5.25%) and 8/ 1,169 (0.68%), respectively], whereas the seroprevalence of anti-HCV was higher in women (12/1,238 [0.97%] vs. 9/2,353 [0.38%]; odds ratio [OR] = 2.49; 95% confidence interval [Cl]: 1.0-6.0). No significant difference for HBV infection was found across the three study sites or by ethnic group. The seroprevalence of anti-HBc increased with age, but decreased with education level in both genders. Lifetime number of sexual partners was associated with anti-HBc prevalence among men (OR = 1.95; 95% Cl: 1.2-3.1), but not women. The seroprevalence of HBV and HCV was low among Brazilian blood donors, and exposure increased with age in both genders.

Boosting systemic and secreted antibody responses in mice orally immunized with recombinant Bacillus subtilis strains following parenteral priming with a DNA vaccine encoding the enterotoxigenic Escherichia coli (ETEC) CFA/I fimbriae B subunit

Recombinant Bacillus subtilis strains, either spores or vegetative cells, may be employed as safe and low cost orally delivered live vaccine vehicles. In this study, we report the use of an orally delivered B. subtilis vaccine strain to boost systemic and secreted antibody responses in mice i.m. primed with a DNA vaccine encoding the structural subunit (CfaB) of the CFA/I fimbriae encoded by enterotoxigenic Escherichia coli (ETEC), an important etiological agent of diarrhea among travelers and children living in endemic regions. DBA/2 female mice submitted to the prime-boost immunization regimen developed synergic serum (IgG) and mucosal (IgA) antibody responses to the target CfaB antigen. Moreover, in contrast to mice immunized only with one vaccine formulation, sera harvested from prime-boosted vaccinated individuals inhibited adhesion of ETEC cells to human red blood cells. Additionally, vaccinated dams conferred full passive protection to suckling newborn mice challenged with a virulent ETEC strain. Taken together the present results further demonstrate the potential use of recombinant B. subtilis strains as an alternative live vaccine vehicle. (C) 2008 Elsevier Ltd. All rights reserved.

A DNA Vaccine Encoding the Enterohemorragic Escherichia coli Shiga-Like Toxin 2 A(2) and B Subunits Confers Protective Immunity to Shiga Toxin Challenge in the Murine Model

Production of verocytotoxin or Shiga-like toxin (Stx), particularly Stx2, is the basis of hemolytic uremic syndrome, a frequently lethal outcome for subjects infected with Stx2-producing enterohemorrhagic Escherichia coli (EHEC) strains. The toxin is formed by a single A subunit, which promotes protein synthesis inhibition in eukaryotic cells, and five B subunits, which bind to globotriaosylceramide at the surface of host cells. Host enzymes cleave the A subunit into the A(1) peptide, endowed with N-glycosidase activity to the 28S rRNA, and the A(2) peptide, which confers stability to the B pentamer. We report the construction of a DNA vaccine (pStx2 Delta AB) that expresses a nontoxic Stx2 mutated form consisting of the last 32 amino acids of the A(2) sequence and the complete B subunit as two nonfused polypeptides. Immunization trials carried out with the DNA vaccine in BALB/c mice, alone or in combination with another DNA vaccine encoding granulocyte-macrophage colony-stimulating factor, resulted in systemic Stx-specific antibody responses targeting both A and B subunits of the native Stx2. Moreover, anti-Stx2 antibodies raised in mice immunized with pStx2 Delta AB showed toxin neutralization activity in vitro and, more importantly, conferred partial protection to Stx2 challenge in vivo. The present vector represents the second DNA vaccine so far reported to induce protective immunity to Stx2 and may contribute, either alone or in combination with other procedures, to the development of prophylactic or therapeutic interventions aiming to ameliorate EHEC infection-associated sequelae.

Economic Impact of a Rotavirus Vaccine in Brazil

The study was done to evaluate the cost-effectiveness of a national rotavirus vaccination programme in Brazilian children from the healthcare system perspective. A hypothetical annual birth-cohort was followed for a five-year period. Published and national administrative data were incorporated into a model to quantify the consequences of vaccination versus no vaccination. Main outcome measures included the reduction in disease burden, lives saved, and disability-adjusted life-years (DALYs) averted. A rotavirus vaccination programme in Brazil would prevent an estimated 1,804 deaths associated with gastroenteritis due to rotavirus, 91,127 hospitalizations, and 550,198 outpatient visits. Vaccination is likely to reduce 76% of the overall healthcare burden of rotavirus-associated gastroenteritis in Brazil. At a vaccine price of US$ 7-8 per dose, the cost-effectiveness ratio would be US$ 643 per DALY averted. Rotavirus vaccination can reduce the burden of gastroenteritis due to rotavirus at a reasonable cost-effectiveness ratio.

Immune Responses and Therapeutic Antitumor Effects of an Experimental DNA Vaccine Encoding Human Papillomavirus Type 16 Oncoproteins Genetically Fused to Herpesvirus Glycoprotein D

Recombinant adenovirus or DNA vaccines encoding herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) genetically fused to human papillomavirus type 16 (HPV-16) oncoproteins (E5, E6, and E7) induce antigen-specific CD8(+) T-cell responses and confer preventive resistance to transplantable murine tumor cells (TC-1 cells). In the present report, we characterized some previously uncovered aspects concerning the induction of CD8(+) T-cell responses and the therapeutic anticancer effects achieved in C57BL/6 mice immunized with pgD-E7E6E5 previously challenged with TC-1 cells. Concerning the characterization of the immune responses elicited in mice vaccinated with pgD-E7E6E5, we determined the effect of the CD4(+) T-cell requirement, longevity, and dose-dependent activation on the E7-specific CD8(+) T-cell responses. In addition, we determined the priming/boosting properties of pgD-E7E6E5 when used in combination with a recombinant serotype 68 adenovirus (AdC68) vector encoding the same chimeric antigen. Mice challenged with TC-1 cells and then immunized with three doses of pgD-E7E6E5 elicited CD8(+) T-cell responses, measured by intracellular gamma interferon (IFN-gamma) and CD107a accumulation, to the three HPV-16 oncoproteins and displayed in vivo antigen-specific cytolytic activity, as demonstrated with carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled target cells pulsed with oligopeptides corresponding to the H-2D(b)-restricted immunodominant epitopes of the E7, E6, or E5 oncoprotein. Up to 70% of the mice challenged with 5 x 10(5) TC-1 cells and immunized with pgD-E7E6E5 controlled tumor development even after 3 days of tumor cell challenge. In addition, coadministration of pgD-E7E6E5 with DNA vectors encoding pGM-CSF or interleukin-12 (IL-12) enhanced the therapeutic antitumor effects for all mice challenged with TC-1 cells. In conclusion, the present results expand our previous knowledge on the immune modulation properties of the pgD-E7E6E5 vector and demonstrate, for the first time, the strong antitumor effects of the DNA vaccine, raising promising perspectives regarding the development of immunotherapeutic reagents for the control of HPV-16-associated tumors.

Salmonella enterica Serovar Typhimurium Vaccine Strains Expressing a Nontoxic Shiga-Like Toxin 2 Derivative Induce Partial Protective Immunity to the Toxin Expressed by Enterohemorrhagic Escherichia coli

Shiga-like toxin 2 (Stx2)-producing enterohemorrhagic Escherichia coli (referred to as EHEC or STEC) strains are the primary etiologic agents of hemolytic-uremic syndrome (HUS), which leads to renal failure and high mortality rates. Expression of Stx2 is the most relevant virulence-associated factor of EHEC strains, and toxin neutralization by antigen-specific serum antibodies represents the main target for both preventive and therapeutic anti-HUS approaches. In the present report, we describe two Salmonella enterica serovar Typhimurium aroA vaccine strains expressing a nontoxic plasmid-encoded derivative of Stx2 (Stx2 Delta AB) containing the complete nontoxic A2 subunit and the receptor binding B subunit. The two S. Typhimurium strains differ in the expression of flagellin, the structural subunit of the flagellar shaft, which exerts strong adjuvant effects. The vaccine strains expressed Stx2 Delta AB, either cell bound or secreted into the extracellular environment, and showed enhanced mouse gut colonization and high plasmid stability under both in vitro and in vivo conditions. Oral immunization of mice with three doses of the S. Typhimurium vaccine strains elicited serum anti-Stx2B (IgG) antibodies that neutralized the toxic effects of the native toxin under in vitro conditions (Vero cells) and conferred partial protection under in vivo conditions. No significant differences with respect to gut colonization or the induction of antigen-specific antibody responses were detected in mice vaccinated with flagellated versus nonflagellated bacterial strains. The present results indicate that expression of Stx2 Delta AB by attenuated S. Typhimurium strains is an alternative vaccine approach for HUS control, but additional improvements in the immunogenicity of Stx2 toxoids are still required.

Distinctive Immunomodulatory and Inflammatory Properties of the Escherichia coli Type II Heat-Labile Enterotoxin LT-IIa and Its B Pentamer following Intradermal Administration

The type I and type II heat-labile enterotoxins (LT-I and LT-II) are strong mucosal adjuvants when they are coadministered with soluble antigens. Nonetheless, data on the parenteral adjuvant activities of LT-II are still limited. Particularly, no previous study has evaluated the adjuvant effects and induced inflammatory reactions of LT-II holotoxins or their B pentameric subunits after delivery via the intradermal (i.d.) route to mice. In the present report, the adjuvant and local skin inflammatory effects of LT-IIa and its B subunit pentamer (LT-IIaB(5)) were determined. When coadministered with ovalbumin (OVA), LT-IIa and, to a lesser extent, LT-IIaB(5) exhibited serum IgG adjuvant effects. In addition, LT-IIa but not LT-IIaB(5) induced T cell-specific anti-OVA responses, particularly in respect to induction of antigen-specific cytotoxic CD8(+) T cell responses. LT-IIa and LT-IIaB(5) induced differential tissue permeability and local inflammatory reactions after i.d. injection. Of particular interest was the reduced or complete lack of local reactions, such as edema and tissue induration, in mice i.d. inoculated with LT-IIa and LT-IIaB(5), respectively, compared with mice immunized with LT-I. In conclusion, the present results show that LT-IIa and, to a lesser extent, LT-IIaB(5) exert adjuvant effects when they are delivered via the i.d. route. In addition, the low inflammatory effects of LT-IIa and LT-IIaB(5) in comparison to those of LT-I support the usefulness of LT-IIa and LT-IIaB(5) as parenterally delivered vaccine adjuvants.

Evolutionary dynamics of the immunodominant repeats of the Plasmodium vivax malaria-vaccine candidate circumsporozoite protein (CSP)

The circumsporozoite protein (CSP) of Plasmodium vivax, a major target for malaria vaccine development, has immunodominant B-cell epitopes mapped to central nonapeptide repeat arrays. To determine whether rearrangements of repeat motifs during mitotic DNA replication of parasites create significant CSP diversity under conditions of low effective meiotic recombination rates, we examined csp alleles from sympatric P. vivax isolates systematically sampled from an area of low malaria endemicity in Brazil over a period of 14 months. Nine unique csp types, comprising six different nona peptide repeats, were observed in 45 isolates analyzed. Identical or nearly identical repeats predominated in most arrays, consistent with their recent expansion. We found strong linkage disequilibrium at sites across the chromosome 8 segment flanking the csp locus, consistent with rare meiotic recombination in this region. We conclude that CSP repeat diversity may not be severely constrained by rare meiotic recombination in areas of low malaria endemicity. New repeat variants may be readily created by nonhomologous recombination even when meiotic recombination is rare, with potential implications for CSP-based vaccine development. (C) 2010 Elsevier B.V. All rights reserved.

CD8(+) T cell adjuvant effects of Salmonella FliCd flagellin in live vaccine vectors or as purified protein

Salmonella flagellin, the flagellum structural subunit, has received particular interest as a vaccine adjuvant conferring enhanced immunogenity to soluble proteins or peptides, both for activation of antibody and cellular immune responses. In the present study, we evaluated the Salmonella enterica FliCd flagellin as a T cell vaccine adjuvant using as model the 9-mer (SYVPSAEQI) synthetic H2(d)-restricted CD8(+) T cell-specific epitope (CS(280-288)) derived from the Plasmodium yoelii circumsporozoite (G) protein. The FliCd adjuvant effects were determined under two different conditions: (i) as recombinant flagella, expressed by orally delivered live S. Dublin vaccine strains expressing the target CS(280-288) peptide fused at the central hypervariable domain, and (ii) as purified protein in acellular vaccines in which flagellin was administered to mice either as a recombinant protein fused or admixed with the target CS(280-288) peptide. The results showed that CS(280-288)-specific cytotoxic CD8(+) T cells were primed when BALB/c mice were orally inoculated with the expressing the CS280-288 epitope S. Dublin vaccine strain. In contrast, mice immunized with purified FliCd admixed with the CS280-288 peptide and, to a lesser extent, fused with the target peptide developed specific cytotoxic CD8(+) T cell responses without the need of a heterologous booster immunization. The CD8(+) T cell adjuvant effects of flagellin, either fused or not with the target peptide, correlated with the in vivo activation of CD11c(+) dendritic cells. Taken together, the present results demonstrate that Salmonella flagellins are flexible adjuvant and induce adaptative immune responses when administered by different routes or vaccine formulations. (C) 2009 Elsevier Ltd. All rights reserved.

A vaccine against S. pyogenes: Design and experimental immune response

Streptococcus pyogenes causes severe invasive infections: the post-streptococcal sequelae of acute rheumatic fever (RF) and rheumatic heart disease (RHD), acute glomerulonephritis, and uncomplicated pharyngitis and pyoderma. Efforts to produce a vaccine against S. pyogenes began several decades ago, and different models have been proposed. Here, we describe the methodology used in the development of a new vaccine model, consisting of both T and B protective epitopes constructed as synthetic peptides and recombinant proteins. Two adjuvants were tested in an experimental inbred mouse model: a classical Freund`s adjuvant and a new adjuvant (AFCo1) that induces mucosal immune responses and is obtained by calcium precipitation of a proteoliposome derived from the outer membrane of Neisseria meningitides B. The StreptInCor vaccine epitope co-administrated with AFCo1 adjuvant induced mucosal (IgA) and systemic (IgG) antibodies as preferential Th1-mediated immune responses. No autoimmune reactions were observed, suggesting that the vaccine epitope is safe. (c) 2009 Elsevier Inc. All rights reserved.