Safety,reactogenicity and immunogenicity of a novel pneumococcal protein-based vaccine in adults: A phase I/II randomized clinical study

Background

New vaccines containing highly conserved Streptococcus pneumoniae proteins such as pneumolysin toxoid (dPly) and histidine-triad protein D (PhtD) are being developed to provide broader protection against pneumococcal disease. This study evaluated the safety, reactogenicity and immunogenicity of different pneumococcal protein-containing formulations in adults.

Methods

In a phase I double-blind study (www.clinicaltrials.gov: NCT00707798), healthy adults (18–40 years) were randomized (1:2:2:2:2:2:2) to receive two doses of one of six investigational vaccine formulations 2 months apart, or a single dose of the control 23-valent pneumococcal polysaccharide vaccine (23PPV; Pneumovax23™, Sanofi Pasteur MSD) followed by placebo. The investigational formulations contained dPly alone (10 or 30 μg), or both dPly and PhtD (10 or 30 μg each) alone or combined with the polysaccharide conjugates of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV; Synflorix™, GlaxoSmithKline Vaccines). Two groups primed with a formulation containing dPly and PhtD (10 or 30 μg each) continued to the follow-up phase II study (NCT00896064), in which they received a booster dose at 5–9 months after primary vaccination.

Results

Of 156 enrolled and vaccinated adults, 146 completed the primary immunization and 43 adults received a booster dose. During primary and booster vaccination, for any formulation, ≤8.9% of doses were followed by grade 3 solicited local or general adverse events. No fever >39.5 °C (oral temperature) was reported. Unsolicited adverse events considered causally related to vaccination were reported following ≤33.3% of investigational vaccine doses. No serious adverse events were reported for adults receiving investigational vaccine formulations. Formulations containing dPly with or without PhtD were immunogenic for these antigens; polysaccharide conjugate-containing formulations were also immunogenic for those 10 polysaccharides.

Conclusion

Investigational vaccine formulations containing dPly and PhtD were well tolerated and immunogenic when administered to healthy adults as standalone protein vaccine or combined with PHiD-CV conjugates.     

Adjuvant system AS02V enhances humoral and cellular immune responses to pneumococcal protein PhtD vaccine in healthy young and older adults: Randomised,controlled trials

BackgroundThe protection elicited by polysaccharide pneumococcal vaccines against community-acquired pneumonia in older adults remains debatable. Alternative vaccine targets include well-conserved pneumococcal protein antigens, such as pneumococcal histidine triad protein D (PhtD).ObjectiveTo evaluate humoral and cellular immune responses and safety/reactogenicity following immunisation with PhtD vaccine with or without adjuvant (alum or AS02_V) in older (≥65 years) and young (18–45 years) healthy adults.MethodsTwo phase I/II, single-blind, parallel-group studies were conducted in 150 older and 147 young adults. Participants were randomised to receive 2 doses (months 0 and 2) of PhtD 30 μg, PhtD 10 μg plus alum, PhtD 30 μg plus alum, PhtD 10 μg plus AS02_V or PhtD 30 μg plus AS02_V, or the 23-valent polysaccharide pneumococcal vaccine (23PPV) at month 0 with placebo (saline solution) at month 2. Safety/reactogenicity was assessed. PhtD-specific antibody, T cell and memory B cell responses were evaluated.ResultsSolicited adverse events were more common in young participants and with adjuvanted vaccines. No vaccine-related serious adverse events were reported. Although anti-PhtD geometric mean antibody concentrations (GMCs) were consistently lower in the older adult cohort than in young adults, GMCs in the older cohort following PhtD 30 μg plus AS02_V were comparable to those induced by plain PhtD or PhtD 30 μg plus alum in the young cohort. Compared with alum adjuvant, AS02_V adjuvant system was associated with an increased frequency of PhtD-specific CD4 cells in both cohorts and a significantly higher specific memory B cell response in the older cohort, similar to responses obtained in the young cohort.ConclusionThe improved immune response to PhtD vaccine containing the AS02_V adjuvant system in comparison to alum suggests that the reduced immune response to vaccines in older adults can be partially restored to the response level observed in young adults. ClinicalTrials.gov identifiers: NCT00307528/NCT01767402.     

Safety and immunogenicity of an investigational vaccine containing two common pneumococcal proteins in toddlers: A phase II randomized clinical trial

Background

To provide broader protection against pneumococcal disease, new vaccines containing conserved Streptococcus pneumoniae proteins are being developed. This study assessed the safety, reactogenicity and immunogenicity of four formulations containing pneumococcal proteins pneumolysin toxoid (dPly) and histidine triad protein (PhtD) in toddlers.

Methods

In this phase II, multicenter, observer-blind study (www.clinicaltrials.gov: NCT00985751) conducted in the Czech Republic, toddlers (12–23 months) were randomized (1:1:1:1:1) to receive one of four investigational vaccine formulations (10 or 30 μg each of dPly and PhtD, alone or in combination with polysaccharide conjugates from the pneumococcal non-typeable Haemophilus influenzae protein-D conjugate vaccine [PHiD-CV]), or the licensed PHiD-CV, in a 2-dose primary series plus booster at study months 0, 2 and 6. Solicited local and general symptoms were recorded within seven days post-vaccination, unsolicited symptoms within 31 days post-vaccination, and serious adverse events (SAEs) during the entire study period. Antibody concentrations against the vaccine components were measured pre-vaccination, one month post-dose 2, pre- and one month post-booster.

Results

257 toddlers were enrolled and vaccinated. Percentages of solicited local and general symptoms following the different investigational formulations were generally within the same ranges as for PHiD-CV. After each dose, grade 3 fever (>40.0 °C, rectal measurement) was reported for maximum one toddler in each group with no differences between investigational formulations and PHiD-CV during primary vaccination. 23 SAEs were reported for 17 toddlers, with distribution balanced between all groups except the group receiving 30 μg dPly/PhtD with PHiD-CV-conjugates (no SAEs reported). None of the SAEs were considered to be vaccine-related.For all pneumococcal protein-containing formulations, anti-PhtD and anti-Ply antibody geometric mean concentrations increased from pre-vaccination to post-dose 2 and from pre- to post-booster vaccination.

Conclusion

All investigational vaccine formulations were well-tolerated and immunogenic when administered to toddlers as a 2-dose primary vaccination followed by a booster dose.     

Efficacy,safety and immunogenicity of a pneumococcal protein-based vaccine co-administered with 13-valent pneumococcal conjugate vaccine against acute otitis media in young children: A phase IIb randomized study

BackgroundNative American populations experience a substantial burden of pneumococcal disease despite use of highly effective pneumococcal conjugate vaccines (PCVs). Protein-based pneumococcal vaccines may extend protection beyond the serotype-specific protection elicited by PCVs.MethodsIn this phase IIb, double-blind, controlled trial, 6–12 weeks-old Native American infants randomized 1:1, received either a protein-based pneumococcal vaccine (dPly/PhtD) containing pneumolysin toxoid (dPly, 10 µg) and pneumococcal histidine triad protein D (PhtD, 10 µg) or placebo, administered along with 13-valent PCV (PCV13) at ages 2, 4, 6 and 12–15 months. Other pediatric vaccines were given per the routine immunization schedule. We assessed vaccine efficacy (VE) against acute otitis media (AOM) and acute lower respiratory tract infection (ALRI) endpoints. Immunogenicity, reactogenicity and unsolicited adverse events were assessed in a sub-cohort and serious adverse events were assessed in all children.Results1803 infants were randomized (900 dPly/PhtD; 903 Control). VE against all episodes of American Academy of Pediatrics (AAP)-defined AOM was 3.8% (95% confidence interval: −11.4, 16.9). Point estimates of VE against other AOM outcomes ranged between 2.9% (−9.5, 14.0) and 5.2% (−8.0, 16.8). Point estimates of VE against ALRI outcomes ranged between −4.4% (−39.2, 21.8) and 2.0% (−18.3, 18.8). Point estimates of VE tended to be higher against first than all episodes but the confidence intervals included zero. dPly/PhtD vaccine was immunogenic and had an acceptable reactogenicity and safety profile after primary and booster vaccination in Native American infants.ConclusionsThe dPly/PhtD vaccine was immunogenic and well tolerated, however, incremental efficacy in preventing AAP-AOM over PCV13 was not demonstrated.Clinical trials registrationNCT01545375 (www.clinicaltrials.gov)     

Vaccination with a Streptococcus pneumoniae trivalent recombinant PcpA,PhtD and PlyD1 protein vaccine candidate protects against lethal pneumonia in an infant murine model

Streptococcus pneumoniae infections continue to cause significant worldwide morbidity and mortality despite the availability of efficacious serotype-dependent vaccines. The need to incorporate emergent strains expressing additional serotypes into pneumococcal polysaccharide conjugate vaccines has led to an identified need for a pneumococcal protein-based vaccine effective against a broad scope of serotypes. A vaccine consisting of several conserved proteins with different functions during pathogenesis would be preferred. Here, we investigated the efficacy of a trivalent recombinant protein vaccine containing pneumococcal choline-binding protein A (PcpA), pneumococcal histidine triad D (PhtD), and genetically detoxified pneumolysin (PlyD1) in an infant mouse model. We found the trivalent vaccine conferred protection from lethal pneumonia challenges using serotypes 6A and 3. The observed protection with trivalent PcpA, PhtD, and PlyD1 vaccine in infant mice supports the ongoing study of this candidate vaccine in human infant clinical trials.     

Response to conjugate pneumococcal and Haemophilus influenzae type b vaccines in asplenic patients

We determined the immunogenicity of conjugated Haemophilus influenzae type b and pneumococcal vaccines by quantitative analysis of the antibody response in asplenic patients. To that end, we vaccinated 92 patients with a conjugated Hib vaccine and 54 received two doses of conjugated pneumococcal vaccine (PCV7), followed at six months by a plain polysaccharide pneumococcal vaccine (PPV23). Antibody concentrations were measured before and three weeks after vaccination. After one dose of pneumococcal conjugate vaccine, 46% of the patients reached the antibody threshold of ≥1.0 μg/mL for all 7 tested vaccine serotypes. This percentage rose to 54% after the second dose of PCV7 and did not increase further after PPV23. Over 90% of patients had antibody concentrations ≥1.0 μg/mL for at least 5 out of the 7 conjugated pneumococcal serotypes after 2 doses of PCV7. For serotypes, included in the PPV23 vaccine only, 25% (PPS3)-100% (PPS19A) of the patients reached antibody concentrations ≥1.0 μg/mL after one dose of PPV23. For Hib, 97% of the patients reached the threshold concentration of ≥1.0 μg/mL after one dose of vaccine. It can be concluded that the majority of asplenic patients had a sufficient response to conjugated vaccines against Streptococcus pneumoniae and Hib, reflected by a ≥1.0 μg/mL antibody response. Inclusion of conjugated pneumococcal polysaccharide vaccines might be of additional value in the vaccination schedule for asplenic patients because of their high immunogenicity.     

Immunogenicity of pneumococcal conjugate vaccine formulations containing pneumococcal proteins,and immunogenicity and reactogenicity of co-administered routine vaccines – A phase II,randomised, observer-blind study in Gambian infants

Background

Two conserved pneumococcal proteins, pneumolysin toxoid (dPly) and pneumococcal histidine triad protein D (PhtD), combined with 10 polysaccharide conjugates from the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) in two investigational pneumococcal vaccine (PHiD-CV/dPly/PhtD) formulations were immunogenic and well-tolerated when administered to Gambian children. Here, we report immunogenicity of the polysaccharide conjugates, and immunogenicity and reactogenicity of co-administered routine vaccines.

Pneumococcal carriage and acute otitis media induce serum antibodies to pneumococcal surface proteins CbpA and PhtD in children

We assessed the development and role of serum anti-CbpA and -PhtD in early childhood in relation to pneumococcal exposure. Serum IgG concentrations to CbpA and PhtD were measured with enzyme immunoassay in serum samples collected at the ages of 6, 12, 18, and 24 months from 50 healthy children and from 50 adults. Furthermore, antibodies to CbpA, PhtD and the C-terminal fragment of PhtD (PhtD C) were measured in serum samples collected at 12 (N = 286) and 18 months (N = 259) to evaluate the risk of subsequent pneumococcal acute otitis media (AOM) in relation to antibody concentrations. The increase in anti-CbpA and -PhtD concentrations was related to prior pneumococcal exposure. At 12 and 18 months, in the risk model of pneumococcal AOM adjusted for prior pneumococcal AOM, higher concentrations of anti-CbpA, but not anti-PhtD, were associated with a lowered risk of subsequent pneumococcal AOM. In conclusion, pneumococcal exposure induces the development of serum anti-CbpA and -PhtD in early childhood. Anti-CbpA antibodies may play a role in the prevention of subsequent pneumococcal AOM during the second year of life.     

Immunization with PhtD truncated fragments reduces nasopharyngeal colonization by Streptococcus pneumoniae

Despite the undeniable success of polysaccharide vaccines against Streptococcus pneumoniae infections, there is a consensus on the scientific field that this approach should be revised in order to overpass the problems related with these formulations, such as serotype replacement and high production costs. The study of conserved pneumococcal proteins or its truncated fragments has emerged as a serotype independent alternative. In this work, we have characterized the immune response elicited by systemic immunization of mice with the Histidine triad protein D (PhtD) and its’ amino and carboxyl terminal fragments. The proteins were shown to be immunogenic and protective against pneumococcal colonization, with increased IL-17 production, and induction of antibodies able to limit pneumococcal adhesion to human respiratory cells. Antiserum against PhtD_Nter, but not C_ter or PhtD, promoted an increase in bacterial phagocytosis in vitro. Interestingly, antibodies against the PhtD_Nter displayed cross-reactivity with two other pneumococcal proteins, PspA and PspC, due to sequence similarities in the proline rich region of the molecules. On a whole, our results support the inclusion of PhtD, and more specifically, its N-terminal fragment, in a multicomponent serotype independent vaccine.     

Safety and immunogenicity of pneumococcal protein vaccine candidates: Monovalent choline-binding protein A (PcpA) vaccine and bivalent PcpA–pneumococcal histidine triad protein D vaccine

Background

Pneumococcal vaccines based on protein antigens may provide expanded protection against Streptococcus pneumoniae.

Objective

To evaluate safety and immunogenicity in adults of pneumococcal vaccine candidates comprising S. pneumoniae pneumococcal histidine triad protein D (PhtD) and pneumococcal choline-binding protein A (PcpA) in monovalent and bivalent formulations.

Methods

This was a phase I, randomized, observer-blinded, placebo-controlled, step-wise dose-escalation study. Following a pilot safety study in which participants received one intramuscular injection of either aluminum hydroxide (AH)–adjuvanted PcpA (25 μg) or PhtD–PcpA (10 μg each), participants in the main study received AH–adjuvanted PcpA (25 μg), AH–adjuvanted PhtD–PcpA (10, 25, or 50 μg each), unadjuvanted PhtD–PcpA (25 μg each), or placebo as 2 injections 30 days apart. Assignment of successive dose cohorts was made after blinded safety reviews after each dose level. Safety endpoints included rates of solicited injection site and systemic reactions, unsolicited adverse events (AEs), serious AEs (SAEs), and safety laboratory tests. Immunogenicity endpoints included levels of anti-PhtD and anti-PcpA antibodies (ELISA).

Results

Six adults 18–50 years of age were included in the pilot study and 125 in the main study. No obvious increases in solicited reactions or unsolicited AEs were reported with escalating doses (adjuvanted vaccine) after either injection, or with repeated administration. Adjuvanted vaccine candidates were associated with a higher incidence of solicited reactions (particularly injection site reactions) than unadjuvanted vaccine candidates. However, no SAE or discontinuation due to an AE occurred. Geometric mean concentrations of anti-PhtD IgG and anti-PcpA IgG increased significantly after injection 2 compared with injection 1 at each dose level. No enhancement of immune responses was shown with adjuvanted vaccine candidates compared with the unadjuvanted vaccine candidate. In the dose-escalating comparison, a plateau effect at the 25 μg dose was observed as measured by geometric mean concentrations and by fold increases.

Conclusions

Promising safety profiles and immunogenicity of these monovalent and bivalent protein vaccine candidates were demonstrated in an adult population (ClinicalTrials.gov registry no. NCT01444339).     

Safety and immunogenicity of a pneumococcal histidine triad protein D vaccine candidate in adults

Background

Pneumococcal vaccines based on conserved protein antigens have the potential to offer expanded protection against Streptococcus pneumoniae.

Objective

To explore safety and immunogenicity of a recombinant protein vaccine candidate against S. pneumoniae composed of adjuvanted pneumococcal histidine triad protein D (PhtD).

Methods

This phase I, exploratory, open-label, single-center clinical study enrolled adults (18–50 years). Participants in a pilot safety cohort received a single intramuscular injection of 6 μg. Following safety review, 3 dose cohorts were enrolled (6, 25, and 100 μg); participants received 2 injections administered approximately 30 days apart. Assignment of the second injection and successive dose cohorts were made after blinded safety reviews after each injection at each dose level. Safety endpoints included rates of solicited injection site and systemic reactions, unsolicited adverse events, serious adverse events, and safety laboratory tests. Immunogenicity endpoints included levels of anti-PhtD antibodies as measured by ELISA.

Results

Sixty-three participants were enrolled and received the pilot safety dose (n = 3) or at least 1 dose of PhtD vaccine candidate at 6 μg (n = 20), 25 μg (n = 20), or 100 μg (n = 20). No safety concerns were identified. No vaccine-related serious adverse event was reported. The most common solicited injection site reaction was pain and most common solicited systemic reactions were myalgia and headache; most reactions were mild and transient. Observed geometric mean concentrations (95% CI) were 200.99 ELISA units (148.46, 272.10), 352.07 (193.49, 640.63), and 699.15 (405.49, 1205.48) post-injection 1 in the 6, 25, and 100 μg dose cohorts, respectively, and 378.25 (275.56, 519.21), 837.32 (539.29, 1300.04), and 1568.62 (1082.92, 2272.16) post-injection 2.

Conclusions

All dose levels were safe and immunogenic. The frequency of solicited reactions was highest at the 100 μg dose. Administration of a second injection significantly increased the levels of anti-PhtD antibodies (ClinicalTrials.gov registry no. NCT01444001).     

Protective role of PhtD and its amino and carboxyl fragments against pneumococcal sepsis

The implementation of polysaccharide-based vaccines has massively reduced the incidence of invasive pneumococcal diseases. However, there is great concern regarding serotype replacement and the increase in antibiotic resistant strains expressing non-vaccine capsular types. In addition, conjugate vaccines have high production costs, a limiting factor for their implementation in mass immunization programs in developing countries. These limitations have prompted the development of novel vaccine strategies for prevention of Streptococcus pneumoniae infections. The use of conserved pneumococcal antigens such as recombinant proteins or protein fragments presents an interesting serotype-independent alternative. Pht is a family of surface-exposed proteins which have been evaluated as potential vaccine candidates with encouraging results. The present work investigated the immune responses elicited by subcutaneous immunization of mice with the polyhistidine triad protein D (PhtD) and its amino and carboxyl terminal fragments. The proteins were immunogenic and protective against pneumococcal sepsis in mice. Antibodies raised against PhtD increased complement C3b deposition on the pneumococcal surface, mainly mediated by the alternative pathway. Sera from mice immunized with PhtD and PhtD_Cter promoted an increase in bacterial uptake by mouse phagocytes. The interaction of PhtD with the complement system regulator factor H was investigated in silico and in vitro by ELISA and western blot, confirming PhtD as a factor-H binding protein. Our results support the inclusion of PhtD and more specifically, its C-terminal fragment in a multicomponent serotype independent vaccine and suggests a role for the complement system in PhtD-mediated protection.     

Recombinant Liver Stage Antigen-1 (LSA-1) formulated with AS01 or AS02 is safe,elicits high titer antibody and induces IFN-γ/IL-2 CD4+ T cells but does not protect against experimental Plasmodium falciparum infection

Plasmodium falciparum Liver Stage Antigen 1 (LSA-1) is a pre-erythrocytic stage antigen. Our LSA-1 vaccine candidate is a recombinant protein with full-length C- and N-terminal flanking domains and two of the 17 amino acid repeats from the central repeat region termed “LSA-NRC.” We describe the first Phase I/II study of this recombinant LSA-NRC protein formulated with either the AS01 or AS02 adjuvant system. We conducted an open-label Phase I/II study. Thirty-six healthy malaria-naïve adults received one of four formulations by intra-deltoid injection on a 0 and 1 month schedule; low dose (LD) LSA-NRC/AS01:10 μg LSA-NRC/0.5 ml AS01 (n = 5), high dose (HD) LSA-NRC/AS01: 50 μg LSA-NRC/0.5 ml AS01 (n = 13); LD LSA-NRC/AS02: 10 μg LSA-NRC/0.5 ml AS02 (n = 5) and HD LSA-NRC/AS02: 50 μg LSA-NRC/0.5 ml AS02 (n = 13). Two weeks post-second immunization, the high dose vaccinees and 6 non-immunized infectivity controls underwent experimental malaria sporozoite challenge.     

Intranasal immunization with a mixture of PspA and a Toll-like receptor agonist induces specific antibodies and enhances bacterial clearance in the airways of mice

To develop an effective nasal vaccine for Streptococcus pneumoniae, the effects of a panel of Toll-like receptor (TLR) agonists in combination with pneumococcal surface protein A (PspA) on induction of PspA-specific antibodies and bacterial clearance were compared in mice. Mice were nasally immunized with 10 μg of TLR agonist (TLR 2–4 and 9) and 2.5 μg of PspA once per week for 3 weeks. Significantly increased levels of PspA-specific immunoglobulin G (IgG) and IgA in the airways and PspA-specific IgG in plasma were found in mice administered PspA plus each TLR agonist, compared with mice administered PspA alone. In a sub-lethal pneumonia model using a serotype 3 pneumococcal strain, bacterial density in the lungs of mice was significantly reduced in mice administered PspA plus each TLR agonist, compared with mice administered either PspA alone or phosphate-buffered saline alone 3 h after bacterial challenge. Similarly, enhanced bacterial clearance was found in the nasopharynx of mice administered PspA plus each TLR agonist 1 day after infection with a serotype 19F strain. Our data suggest that PspA-specific antibody induced by nasal immunization with PspA plus TLR agonist is capable of reducing the bacterial load in both the nasopharynx and lungs after challenge with pneumococci with different serotypes. Despite the skewed Th1/Th2 immune responses, the effects of nasal immunization with PspA plus each TLR agonist on bacterial clearances from the lungs 3 h after infection and from nasopharynx 1 day after infection in mice were equivalent.     

Immunogenicity and safety of pneumococcal conjugate polysaccharide and free polysaccharide vaccines alone or combined in HIV-infected adults in Brazil

Background

Streptococcus pneumoniae is a leading cause of hospitalization in HIV-infected adults therefore pneumococcal vaccine is recommended. The ideal antipneumococcal vaccine and effective vaccination regimen remain controversial and needs further evaluation.

Methods

To assess the efficacy of pneumococcal vaccines alone and combined, a randomized, blinded clinical trial was conducted in Brazil with 331 HIV-patients aged 18–60, with CD4-T cell count ≥200 cells/mm³. Two interventions 60 days apart were done in three schedules: 23-valent pneumococcal polysaccharide vaccine (PPV23)/placebo; 7-valent pneumococcal conjugate vaccine (PCV7)/placebo; and PCV7 plus PPV23. Safety and reactogenicity were evaluated, and immunogenicity was assessed by an IgG enzyme-linked immunosorbent assay to S. pneumoniae serotypes 6B, 9V and 14, performed at baseline, 60 and 180 days after first intervention. Comparison of immunogenicity was based on geometric mean concentration (GMC), percentages of individuals with serotype-specific IgG ≥ 0.35 μg/mL and ≥1.0 μg/mL and proportion of individuals with ≥4-fold increase in specific antibody concentrations for each serotype.

Results

Demographic and HIV conditions were similar, and both vaccines were well tolerated across vaccine groups. Significant increase in IgG-antibodies was observed to all serotypes evaluated. A greater proportion of PCV7 recipients reached and sustained IgG antibody concentrations at least four times as high as those at baseline, for serotypes 6B and 9V. A PPV23 dose after PCV7 did not enhance immunogenicity.

Conclusions

In this first trial conducted with HIV-infected immunologically stable adults in South America, both PPV23 and PCV7 were safe and immunogenic. Evidence suggesting PCV7 was more immunogenic than PPV23, as it elicited higher and persistent ≥4-fold increase of antibodies for 6B and 9V serotypes in a greater proportion of HIV-patients is noteworthy. Despite current recommendation of schedules combining PCV7 and PPV23, there is little evidence to support this practice and we did not observe benefits in this combination.     

Cell-mediated immunity elicited by the blood stage malaria vaccine apical membrane antigen 1 in Malian adults: Results of a Phase I randomized trial

The development of a safe and effective malaria vaccine is impeded by the complexity of the Plasmodium life cycle. A vaccine that elicits both cell-mediated and humoral immune responses might be needed for protection against this multistage parasitic infection. Apical membrane antigen 1 (AMA-1) plays a key role in erythrocytic invasion but is also expressed in sporozoites and in late stage liver schizonts, where it may provide a target of protective cell-mediated immunity (CMI). A Phase 1 trial of a vaccine consisting of recombinant AMA-1 protein and the Adjuvant system AS02A was conducted in 60 Malian adults aged 18–55 years who were randomized to receive either half-dose (25 μg/0.25 ml) or full dose (50 μg/0.5 ml) FMP2.1/AS02A or a control rabies vaccine. Interleukin 5 (IL-5) and interferon-γ (IFN-γ) production as evaluated by ELISpot and lymphocyte proliferation were measured after in vitro AMA-1 stimulation of peripheral blood mononuclear cells (PBMCs) collected on Days 0 and 90. Post-FMP2.1/AS02A immunization mean stimulation indices were significantly elevated as were the number of IL-5 spot forming cells (SFC)/10⁶ PBMC, but no difference was noted in INF-γ production between the AMA-1/AS02A vaccinated group and the rabies group. These results provide evidence that complex immune responses can be induced by this vaccination strategy and add further impetus for the continuing clinical evaluation of this vaccine.     

Immunogenicity and safety of AS03-adjuvanted H1N1 pandemic vaccines in children and adolescents

Vaccines with acceptable efficacy profile against the H1N1 A/California/7/2009 virus are needed for use in children. The two studies presented here evaluated the immunogenicity and the reactogenicity/safety of A/H1N1/2009 vaccines containing either 3.75 μg haemagglutinin antigen (HA) and AS03_A-adjuvant (3.75 μg HA/AS03_A study) (N = 210 [53, 57 and 100 in the 3-5, 6-9 and 10-17 years age strata, respectively]) or 1.9 μg HA and AS03_B-adjuvant (1.9 μg HA/AS03_B study) (N = 244 [61, 65 and 118 in the 3-5, 6-9 and 10-17 years age strata, respectively]), given as two-dose series. Although the haemagglutination inhibition antibody titres were higher in the 3.75 μg HA/AS03_A study, both vaccine dosages were highly immunogenic and exceeded regulatory acceptance criteria after the first and the second doses. Seroprotection rates reached 100% and seroconversion rates ranged from 98.2% to 99.1% after each dose of both vaccine dosages. Geometric mean titres increased from 456.5 to 1538.5 and from 297.9 to 1106.7 between the first and the second doses in the 3.75 μg HA/AS03_A study and the 1.9 μg HA/AS03_B study, respectively. Despite an observed slight increase of the reactogenicity following the second dose in the 3.75 μg HA/AS03_A study, the vaccines safety profiles were considered clinically acceptable. In conclusion, both dosages of the AS03-adjuvanted A/H1N1/2009 pandemic influenza vaccines were highly immunogenic and well-tolerated in children and adolescents.     

Glycoprotein B (gB) vaccines adjuvanted with AS01 or AS02 protect female guinea pigs against cytomegalovirus (CMV) viremia and offspring mortality in a CMV-challenge model

The transmission of cytomegalovirus (CMV) from mother to fetus can give rise to severe neurodevelopment defects in newborns. One strategy to prevent these congenital defects is prophylactic vaccination in young women. A candidate vaccine antigen is glycoprotein B (gB). This antigen is abundant on the virion surface and is a major target of neutralization responses in human infections. Here, we have evaluated in a challenge model of congenital guinea pig CMV (GPCMV) infection, GPCMV-gB vaccines formulated with the clinically relevant Adjuvant Systems AS01_B and AS02_V, or with Freund's adjuvant (FA). Fifty-two GPCMV-seronegative female guinea pigs were administered three vaccine doses before being mated. GPCMV-challenge was performed at Day 45 of pregnancy (of an estimated 65 day gestation). Pup mortality rates in the gB/AS01_B, gB/AS02_V, and gB/FA groups were 24% (8/34), 10% (4/39) and 36% (12/33), respectively, and in the unvaccinated control group was 65% (37/57). Hence, efficacies against pup mortality were estimated at 64%, 84% and 44% for gB/AS01_B (p < 0.001), gB/AS02_V (p < 0.001) and gB/FA (p = 0.014), respectively. Efficacies against GPCMV viremia (i.e. DNAemia, detected by PCR) were estimated at 88%, 68% and 25% for the same vaccines, respectively, but were only significant for gB/AS01_B (p < 0.001), and gB/AS02_V (p = 0.002). In dams with viremia, viral load was approximately 6-fold lower with vaccination than without. All vaccines were highly immunogenic after two and three doses. In light of these results and of other results of AS01-adjuvanted vaccines in clinical development, vaccine immunogenicity was further explored using human CMV-derived gB antigen adjuvanted with either AS01_B or the related formulation AS01_E. Both adjuvanted vaccines were highly immunogenic after two doses, in contrast to the lower immunogenicity of the unadjuvanted vaccine. In conclusion, the protective efficacy and immunogenicity of adjuvanted vaccines in this guinea pig model are supportive of investigating gB/AS01 and gB/AS02 in the clinic.     

Chronic helminth infections impair pneumococcal vaccine responses

Pneumonia is the leading killer of children and disproportionately affects developing countries. Vaccination campaigns against Streptococcus pneumoniae, the leading cause of pneumonia, have recently been launched with a new conjugate vaccine in Africa. Using a mouse model, we assessed the potential role that the high burden of helminth infections in the countries targeted for vaccine might have on vaccine effectiveness. Mice vaccinated with either commercial conjugate or purified polysaccharide vaccines had impaired antibody responses if they were chronically infected with Taenia crassiceps. This translated to increased susceptibility to pneumococcal pneumonia and high mortality compared to helminth-negative vaccinated animals, which were fully protected from disease and death. Antibodies taken from Taenia-infected, vaccinated mice were unable to effectively opsonize S. pneumoniae for killing by alveolar macrophages, and did not protect against pneumococcal challenge when adoptively transferred into naïve animals. These data may have implications for vaccination programs in countries endemic with helminths.     

The immune enhancement of a novel soy lecithin/β-glucans based adjuvant on native Neospora caninum tachyzoite extract vaccine in mice

Efficient, cost-effective and safe Th1-immunity-inducing vaccine formulations are paramount for achieving protection against Neospora caninum. In this study, a new adjuvant (Providean-AVEC^®) was used in the development of a N. caninum vaccine and evaluated in a mouse model. Soluble N. caninum tachyzoite native protein extract (sNcAg) was selected as vaccine antigen based on its capacity to activate production of pro-inflammatory cytokines on dendritic cells. Vaccines containing 4 and 0.4 μg of sNcAg, and Providean-AVEC^®, ISCOM-Matrix or aluminum hydroxide (Alum) were tested in BALB/c mice. While mice vaccinated with 4 μg of sNcAg + Providean-AVEC^® developed specific antibodies shortly after the first dose, the rest of the high antigen payload formulations only induced seroconversion after the booster. Mice immunized with the high payload ISCOM vaccine (4 μg sNcAg) or with either low or high payload Providean-AVEC^® formulations (0.4 μg and 4 μg sNcAg, respectively) elicited higher IgG2a than IgG1 serum levels, and IFN-γ anamnestic responses with a Th1-cytokine biased profile. These animals had no histological signs of cerebral lesions and parasite burden assessed by quantitative real-time PCR was not detected. Vaccine preparations including Providean-AVEC^® as adjuvant limited N. canimum multiplication even with only a tenth of antigen payload compared to vaccines containing other adjuvants. Using adjuvants to specifically activate dendritic cells, combined with a careful antigen selection can enhance cellular responses to inert N. caninum vaccines.