Delta inulin polysaccharide adjuvant enhances the ability of split-virion H5N1 vaccine to protect against lethal challenge in ferrets

Background

The reduced immunogenicity of the H5 hemagglutinin (HA), compared to seasonal HA serotypes, has stimulated searches for effective adjuvants to improve H5 vaccine efficacy. This study examined the immunogenicity and protective efficacy in ferrets immunized with a split-virion H5N1 vaccine combined with Advax™, a novel delta inulin-based polysaccharide adjuvant technology that has previously demonstrated ability to augment humoral and cellular immunity to co-administered antigens.

Methods

Ferrets were vaccinated twice 21 days apart with 7.5 μg or 22.5 μg of a split-virion preparation of A/Vietnam/1203/2004 with or without adjuvant. An additional group received just one immunization with 22.5 μg HA plus adjuvant. Serum antibodies were measured by hemagglutination inhibition and microneutralization assays. Vaccinated animals were challenged intranasally 21 days after the last immunization with 10⁶ EID₅₀ of the homologous strain. Morbidity was assessed by observed behavior, weight loss, temperature, cytopenias, histopathology, and viral load.

Results

No serum neutralization antibody was detected after two immunizations with unadjuvanted vaccine. Two immunizations with high or low dose adjuvanted vaccine stimulated high neutralizing antibody titers. Survival was 100% in all groups receiving adjuvanted-vaccine including the single dose group, compared to 67% survival with unadjuvanted vaccine, and 0% survival in saline or adjuvant-alone controls. Minimal morbidity was seen in all animals receiving adjuvanted vaccine, and was limited to rhinorrhea and mild thrombocytopenia, without fever, weight loss, or reduced activity. H5N1 virus was cleared from the nasal wash by day 4 post-challenge only in animals receiving adjuvanted vaccine which also prevented viral invasion of the brain in most animals.

Conclusions

In this initial study, Advax™ adjuvant formulations improved the protective efficacy of a split-virion H5N1vaccine as measured by significantly enhanced immunogenicity, survival, and reduced morbidity.     

Safety and immunogenicity of an inactivated whole virus Vero cell-derived Ross River virus vaccine: a randomized trial

Background

Ross River virus (RRV) is endemic in Australia and several South Pacific Islands. Approximately 5000 cases of RRV disease, which is characterized by debilitating polyarthritis, are recorded each year in Australia. This study describes the first clinical trial of a candidate RRV vaccine.

Methods

An inactivated whole-virus Vero cell-derived RRV vaccine was tested in 382 healthy, RRV-naïve adults in a phase 1/2 dose-escalation study at ten sites in Austria, Belgium and The Netherlands. Subjects were equally randomized to receive 1.25 μg, 2.5 μg, 5 μg, or 10 μg aluminum hydroxide-adjuvanted or non-adjuvanted RRV vaccine, with a second dose after three weeks and a booster at six months. Vaccine immunogenicity was determined by measurements of serum IgG and neutralizing antibody titers. Vaccine tolerability and safety were monitored over the entire study period.

Results

The optimal vaccine formulation was the adjuvanted 2.5 μg dose, as calculated using a repeated mixed model analysis of covariance comparing log-transformed RRV-specific IgG titers between different dose groups. Geometric means of RRV-specific serum antibodies measured 21 days after the third vaccination with the 2.5 μg adjuvanted formulation were 520.9 (90% CI 377.2-719.4) as determined by IgG ELISA and 119.9 (82.6-173.9) as determined by virus neutralization assay, resulting in seropositivity rates of 92.9% (82.6-98.0) and 92.7% (82.2-98.0), respectively. All vaccine formulations and doses were well tolerated after the first, second and third vaccination.

Conclusions

The adjuvanted, inactivated whole-virus Vero cell-derived Ross River virus vaccine is highly immunogenic in RRV-naïve adults and well tolerated at all dose levels.     

Randomized comparative study of the serum antihemagglutinin and antineuraminidase antibody responses to six licensed trivalent influenza vaccines

Background

Serum antibody to the hemagglutinin (HA) surface protein of influenza virus induced by influenza vaccination is a correlate of protection against influenza. The neuraminidase (NA) protein is also on the surface of the virus; antibody to it has been shown to impair virus release from infected cells and to reduce the intensity of influenza infections in animal models and in humans challenged with infectious virus. Recently we have shown that NA inhibiting antibody can independently contribute to immunity to naturally-occurring influenza immunity in the presence of antibody to the HA.

Purpose

The present study was conducted to evaluate induction of antibody to the NA and the HA by commercially available influenza vaccines.

Methods

Healthy young adults were vaccinated with one of five commercially available trivalent inactivated vaccines or live influenza vaccine. Frequencies of serum antibody and fold geometric mean titer (GMT) increases four weeks later were measured to each of the three vaccine viruses (A/H1N1, A/H3N2, B) in hemagglutination-inhibition (HAI) and neutralization (neut) assays. Frequency and fold GMT increase in neuraminidase-inhibition (NI) antibody titers were measured to the influenza A viruses (A/H1N1, A/H3N2).

Results

No significant reactogenicity occurred among the vaccinated subjects. The Fluvirin inactivated vaccine induced more anti-HA antibody responses and a higher fold GMT increase than the other inactivated vaccines but there were no major differences in response frequencies or fold GMT increase among the inactivated vaccines. Both the frequency of antibody increase and fold GMT increase were significantly lower for live vaccine than for any inactivated vaccine in HAI and neut assays for all three vaccine viruses. Afluria inactivated vaccine induced more N1 antibody and Fluarix induced more N2 antibody than the other vaccines but all inactivated vaccines induced serum NI antibody. The live vaccine failed to elicit any NI responses for the N2 NA of A/H3N2 virus and frequencies were low for the N1 of A/H1N1 virus.

Conclusions

Trivalent inactivated influenza vaccines with similar HA dosage induce similar serum anti-HA antibody responses in healthy adults. Current inactivated vaccines all induce serum anti-NA antibody to the N1 and N2 NA proteins but some are better than others for N1 or N2. The live vaccine, Flumist, was a poor inducer of either anti-HA or anti-NA serum antibody compared to inactivated vaccine in the healthy adults. In view of the capacity for contributing to immunity to influenza in humans, developing guidelines for NA content and induction of NA antibody is desirable.     

Evaluation of a virosomal H5N1 vaccine formulated with Matrix M™ adjuvant in a phase I clinical trial

The avian influenza H5 virus epizootic continues to cause zoonosis with human fatalities, highlighting the continued need for pandemic preparedness against this subtype. This study evaluated the tolerability and immunogenicity of a Matrix M™ adjuvanted virosomal H5N1 vaccine in a phase I clinical trial. Sixty healthy adults were vaccinated intramuscularly with two doses of influenza H5N1 (NIBRG-14) virosomal vaccine alone (30 μg haemagglutinin (HA)) or 1.5, 7.5 or 30 μg HA formulated with 50 μg Matrix M™ adjuvant. The antibody response was analysed by haemagglutination inhibition (HI), microneutralisation (MN) and single radial haemolysis (SRH) assays. The vaccine was well tolerated in all groups but injection site pain was more frequently observed in the Matrix M™ adjuvanted groups. The vaccine elicited homologous and heterologous H5N1-specific antibody responses and the Matrix M™ adjuvanted formulations met all the EU regulatory criteria. In conclusion, Matrix M™ adjuvant was well tolerated and augmented the antibody response allowing considerable dose sparing down to 1.5 μg HA.     

Intradermally-administered influenza virus vaccine is safe and immunogenic in healthy adults 18–64 years of age

Background

To increase vaccine acceptance, intradermal (ID) influenza vaccine (Fluzone^® Intradermal, Sanofi Pasteur Inc.) may be an attractive alternative to intramuscular (IM) vaccination due to smaller needle and volume injected.

Methods

A multicenter, randomized (2:1 ID vs IM vaccines) study, blinded for ID vaccine lots, was conducted among 4292 adults 18–64 years of age enrolled in October 2008. Three lots of investigational trivalent influenza vaccine containing 9 μg hemagglutinin (HA) per strain in 0.1 mL administered ID with a 30 gauge, 1.5 mm long needle were compared to standard dose vaccine (0.5 mL containing 15 μg HA/strain) given IM.

Results

The post-vaccination antibody geometric mean titers (GMT) for the ID vaccine were similar to the IM vaccine (H1N1: 193.2 vs. 178.3, H3N2: 246.7 vs. 230.7, and B: 102.5 vs. 126.9). Non-inferiority was met for the ID vaccine compared to IM vaccine as assessed by antibody GMT ratios (IM/ID) for all three virus strains (H1N1: 0.92, H3N2: 0.94, and B: 1.24). Seroconversion rates were non-inferior for H1N1 and H3N2, but not for B (ID vs. IM: H1N1: 61.2% vs. 60.5%, H3N2: 75.3% vs. 74.8%, and B: 46.2% vs. 54.2%). Seroprotection (HAI titer ≥1:40) rates were similar between groups (ID vs. IM, H1N1: 91.1% vs. 91.7%, H3N2: 90.7% vs. 91.4%, and B: 87.4% vs. 89.3%). Local injection site reactions overall were more common with ID than IM vaccine (ID vs. IM: 89.2% vs. 60.2%), but were usually grade 1 or 2 and transient. The frequencies of local injection site pain and systemic reactions were similar between vaccine groups, except more myalgia with IM vaccine.

Conclusions

The ID vaccine elicited immune responses comparable to IM vaccine except for the seroconversion rate to B virus. With the exception of pain, local injection site reactions were more common with the ID vaccine, but well-tolerated and of short duration.

Trial registration

ClinicalTrials.gov identifier: NCT00772109.     

An observer-blind,randomized, multi-center trial assessing long-term safety and immunogenicity of AS03-adjuvanted or unadjuvanted H1N1/2009 influenza vaccines in children 10–17 years of age

Background

Vaccination is an effective strategy to prevent influenza. This observer-blind, randomized study in children 10–17 years of age assessed whether the hemagglutination inhibition (HI) antibody responses elicited by H1N1/2009 vaccines adjuvanted with AS03 (an adjuvant system containing α-tocopherol and squalene in an oil-in-water emulsion) or without adjuvant, met the European regulatory immunogenicity criteria at Days 21 and 182.

Methods

Three hundred and ten healthy children were randomized (3:3:3:5) to receive one dose of 3.75 μg hemagglutinin (HA) AS03_A-adjuvanted vaccine, one or two doses of 1.9 μg HA AS03_B-adjuvanted vaccine, or one dose of 15 μg HA pandemic vaccine. All children received a booster dose of the allocated vaccine at Day 182. Serum samples were tested for HI antibody response at Days 21, 42, 182 and 189.

Results

All vaccination regimens elicited HI antibody responses that met the European regulatory criteria at Days 21 and 42. HI antibody responses fulfilling European regulatory criteria were still observed six months after the first vaccine dose in all study vaccines groups. Two doses of 1.9 μg HA AS03_B-adjuvanted vaccine elicited the strongest HI antibody response throughout the study. The non-adjuvanted 15 μg HA vaccine elicited a lower HI antibody response than the AS03-adjuvanted vaccines. At Day 189, the European regulatory criteria were met for all vaccines with baseline HI antibody titers as reference. An anamnestic response for all vaccines was suggested at Day 189, based on the rapid increase in HI antibody geometric mean titers (1.5–2.5-fold increase). Injection site reactogenicity was higher following the AS03-adjuvanted vaccines compared with the non-adjuvanted vaccine. No safety concerns were identified for any study vaccine.

Conclusion

All study vaccines elicited HI antibody responses that persisted at purported protective levels through six months after vaccination and fulfilled the European regulatory criteria.     

Safety and immunogenicity of adjuvanted inactivated split-virion and whole-virion influenza A (H5N1) vaccines in children: A phase I–II randomized trial

Objective

Highly pathogenic avian influenza A virus H5N1 has the potential to cause a pandemic. Many prototype pandemic influenza A (H5N1) vaccines had been developed and well evaluated in adults in recent years. However, data in children are limited. Herein we evaluate the safety and immunogenicity of adjuvanted split-virion and whole-virion H5N1 vaccines in children.

Methods

An open-labelled phase I trial was conducted in children aged 3–11 years to receive aluminum-adjuvated, split-virion H5N1 vaccine (5–30 μg) and in children aged 12–17 years to receive aluminum-adjuvated, whole-virion H5N1 vaccine (5–15 μg). Safety of the two formulations was assessed. Then a randomized phase II trial was conducted, in which 141 children aged 3–11 years received the split-virion vaccine (10 or 15 μg) and 280 children aged 12–17 years received the split-virion vaccine (10–30 μg) or the whole-virion vaccine (5 μg). Serum samples were collected for hemagglutination-inhibition (HI) assays.

Findings

5–15 μg adjuvated split-virion vaccines were well tolerated in children aged 3–11 years and 5–30 μg adjuvated split-virion vaccines and 5 μg adjuvated whole-virion vaccine were well tolerated in children aged 12–17 years. Most local and systemic reactions were mild or moderate. Before vaccination, all participants were immunologically naïve to H5N1 virus. Immune responses were induced after the first dose and significantly boosted after the second dose. In 3–11 years children, the 10 and 15 μg split-virion vaccine induced similar responses with 55% seroconversion and seroprotection (HI titer ≥1:40) rates. In 12–17 years children, the 30 μg split-virion vaccine induced the highest immune response with 71% seroconversion and seroprotection rates. The 5 μg whole-virion vaccine induced higher response than the 10 μg split-virion vaccine did.

Interpretation

The aluminum-adjuvanted, split-virion prototype pandemic influenza A (H5N1) vaccine showed good safety and immunogenicity in children and 30 μg dose induced immune response complying with European Union licensure criteria. [ClinicalTrials.gov identifiers: NCT00900588 and NCT00900991].     

Comparable humoral response after two doses of adjuvanted influenza A/H1N1pdm2009 vaccine or natural infection in allogeneic stem cell transplant recipients

Background

The present study evaluated immunogenicity and tolerance of two-dose influenza A/H1N1pdm09 vaccination in allogeneic hematopoietic stem cell transplantation (HSCT) recipients, and compared the vaccine-induced humoral response to that triggered by natural infection in another group of HSCT patients.

Methods

Adult allogeneic HSCT recipients vaccinated with two doses of influenza A/H1N1pdm09 vaccine, separated by 3 weeks, and patients with proven influenza A/H1N1pdm09 infection were included. Antibody responses were measured by hemagglutination-inhibition assay 1) on days 0, 21, 42 and 6 months after the first vaccine injection in vaccinated patients and 2) before pandemic and after influenza A/H1N1pdm09 infection, in patients presented natural infection.

Results

At baseline, 3% of 59 recipients of adjuvanted vaccine and 0% of 20 infected patients were seroprotected (antibody titer ≥ 1/40). Seroprotection rate observed 42 days after vaccination was not different from that observed after natural infection (66% and 60% respectively, p = 0.78). In vaccinated patients, seroprotection rate increased significantly from 54% to 66% between day 21 and 42 (p = 0.015). Moreover, after 6 months, seroprotection rate in 21 vaccinated patients was similar to that observed in 10 infected patients evaluated at least 76 days after infection (D76–217) (60% and 81% respectively, p = 0.2). In multivariate analysis, no immunosuppressive treatment or chronic graft-versus-host disease (GVHD) and longer time between transplantation and vaccination/infection were associated with a stronger humoral response. The adjuvanted vaccine was safe with low rate of GVHD worsening.

Conclusion

In HSCT recipients, two doses of influenza A/H1N1pdm09 adjuvanted vaccine were safe and induced a humoral response comparable to that triggered by natural infection in these patients.     

Immune response after one or two doses of pandemic influenza A (H1N1) monovalent,AS03-adjuvanted vaccine in HIV infected adults

Introduction

Continued research is needed to evaluate and improve the immunogenicity of influenza vaccines in HIV infected patients. We aimed to determine the antibody responses after one or two doses of the AS03-adjuvanted pandemic influenza A (H1N1) vaccine in HIV infected patients.

Method

Following the influenza season 2009/2010, 219 HIV infected patients were included and divided into three groups depending on whether they received none (n = 60), one (n = 31) or two (n = 128) doses of pandemic influenza A (H1N1) vaccine. At inclusion, antibody titers for all patients were analyzed and compared to pre-pandemic antibody titers analyzed from serum samples in a local storage facility.

Results

4–9 months after a single immunization, we found a seroprotection rate of 77.4% and seroconversion rate of 67.7%. After two immunizations the rates increased significantly to seroprotection rate of 97.7% and seroconversion rate of 86.7%.

Conclusion

A single dose of AS03-adjuvanted pandemic influenza A (H1N1) vaccine created an adequate immune response in HIV infected patients lasting as long as 4–9 months. Two doses improved the immunogenicity further.     

Effect of two injections of non-adjuvanted influenza A H1N1pdm2009 vaccine in renal transplant recipients: INSERM C09-32 TRANSFLUVAC trial

Background

Enhancing vaccine immunogenicity in kidney transplant recipients, particularly against influenza, is required since the immunosuppression used to prevent graft rejection limits vaccine immunogenicity. We therefore investigated the immunogenicity and safety of a double dose non-adjuvanted vaccination regimen against influenza H1N1pdm2009 in kidney transplant adult recipients.

Methods

A prospective single-arm study was conducted including 121 renal transplant recipients under triple immunosuppressive regimen. Patients received 2 injections (day 0, day 21) of an inactivated, non-adjuvanted H1N1pdm2009 vaccine. Immunogenicity (hemagglutination-inhibition [HI] antibodies and anti-hemagglutin [HA] specific T cells) was evaluated after one and two injections (day 21, day 42) and at 6 months (day 182).

Results

The seroprotection rate (HI antibody titer ≥ 1/40) was 19% at day 0 (n = 119), 53% at day 21 (n = 118), 60% at day 42 (n = 116) (p = 0.013; day 42 vs. day 21) and 56% at day 182 (n = 113). The seroconversion rate was 24% and 32%, the geometric mean fold rise was 3.7 and 4.6 after the first and second injections, respectively. T-cell immunity to the H1N1pdm2009 vaccine showed a two-fold increase from baseline, though not statistically significant, in H1N1pdm2009-HA-specific CD4+ and CD8+ T cells in 34% and 48% of cases, respectively. No rejection episodes related to vaccination were observed while the donor-specific antibodies and creatinine clearance remained unchanged throughout the study.

Conclusion

Administration of two doses of the non-adjuvanted influenza H1N1pdm2009 vaccine in renal transplant patients is safe and induces a significant seroprotection, not strong enough yet to meet European or US requirements for adults below 60 years, but comparable to seroprotection levels usually observed in the non immunosuppressed elderly population or conferred by a single dose of adjuvanted vaccine in solid organ transplant recipients. These results provide useful indications for future strategies required to improve immunogenicity of vaccines against influenza in transplanted patients.     

A cell culture-derived whole-virus H9N2 vaccine induces high titer antibodies against hemagglutinin and neuraminidase and protects mice from severe lung pathology and weight loss after challenge with a highly virulent H9N2 isolate

Background

Influenza viruses of subtype A/H9N2 are enzootic in poultry across Asia and the Middle East and are considered to have pandemic potential. The development of new vaccine manufacturing technologies is a cornerstone of influenza pandemic preparedness.

Methods

A non-adjuvanted whole-virus H9N2 vaccine was developed using Vero cell culture manufacturing technology. The induction of hemagglutination inhibition (HI) and virus-neutralizing antibodies was assessed in CD1 mice and guinea pigs. A highly sensitive enzyme-linked lectin assay was used to investigate the induction of antibodies capable of inhibiting the enzymatic activity of the H9N2 neuraminidase. Protective efficacy against virus replication in the lung after challenge with the homologous virus was evaluated in BALB/c mice by a TCID₅₀ assay, and prevention of virus replication in the lung and associated pathology were evaluated by histology and immunohistochemistry. To investigate the ability of the vaccine to prevent severe disease, BALB/c mice were challenged with a highly virulent mouse-adapted H9N2 isolate which was generated by multiple lung-to-lung passage of wild-type virus.

Results

The vaccine elicited high titers of functional H9N2-specific HA antibodies in both mice and guinea pigs, as determined by HI and virus neutralization assays. High titer H9N2-specific neuraminidase inhibiting (NAi) antibodies were also induced in both species. Vaccinated mice were protected from lung virus replication in a dose-dependent manner after challenge with the homologous H9N2 virus. Immunohistochemical analyses confirmed the lack of virus replication in the lung and an associated substantial reduction in lung pathology. Dose-dependent protection from severe weight loss was also provided after challenge with the highly virulent mouse-adapted H9N2 virus.

Conclusions

The induction of high titers of H9N2-specific HI, virus-neutralizing and NAi antibodies and dose-dependent protection from virus replication and severe disease in animal models suggest that the Vero cell culture-derived whole-virus vaccine will provide an effective intervention in the event of a H9N2 pandemic situation.     

A Phase I,randomized, open-label study to evaluate the safety and immunogenicity of an enterovirus 71 vaccine

Background

Large-scale outbreaks of enterovirus 71 (EV71) infections have occurred in Asia-Pacific regions. Severe complications include encephalitis and poliomyelitis-like paralysis, cardiopulmonary collapse, and death, necessitating an effective vaccine against EV71.

Methods

In this randomized Phase I study, we evaluated the safety and immunogenicity of an inactivated alum-adjuvanted EV71 whole-virus vaccine produced on Vero cell cultures. Sixty healthy volunteers aged 20–60 years received two doses of vaccine, administered 21 days apart. Each dose contained either 5 μg of EV71 antigen with 150 μg of adjuvant (Group A05) or 10 μg of EV71 antigen with 300 μg of adjuvant (Group B10). Serologic analysis was performed at baseline, day 21, and day 42.

Results

There were no serious adverse events. Mild injection site pain and myalgia were the most common adverse events with either vaccine formulation. The immunogenicity data showed that 90% of vaccine recipients have a 4-fold or greater increase in neutralization antibody titers (NT) after the first dose, without a further increase in NT after the second dose. The seroconversion rates on day 21 and day 42 were 86.7% and 93.1% respectively, in Group A05, and 92.9% and 96.3%, respectively, in Group B10. Thus, 5 μg and 10 μg of the EV71 vaccine can induce a remarkable immune response in healthy adults after only the first vaccination.

Conclusion

The 5 μg and 10 μg adjuvanted EV71 vaccines are generally safe and immunogenic in healthy adults. (ClinicalTrials.gov number, NCT01268787).     

Recombinant H5 hemagglutinin adjuvanted with nanoemulsion protects ferrets against pathogenic avian influenza virus challenge

Background

Highly pathogenic H5N1 influenza viruses remain a pandemic risk to the world population. Although vaccines are the best solution to prevent this threat, a more effective vaccine for H5 strains of influenza has yet to be developed. All existing vaccines target only serum antibody against influenza as the primary outcome, while mucosal immunity has not been addressed. To address these shortcomings we have used an effective mucosal adjuvant system to produce a prototype vaccine that provides antibody, cellular and mucosal immunity to multiple serotypes of H5.

Inactivated and adjuvanted whole-virion clade 2.3.4 H5N1 pre-pandemic influenza vaccine possesses broad protective efficacy against infection by heterologous clades of highly pathogenic H5N1 avian influenza virus in mice

In this study, we evaluated the immunogenicity and protective efficacy of a candidate attenuated H5N1 pre-pandemic influenza vaccine of clade 2.3.4, rgAnhui, which was reverse genetically generated from highly virulent A/Anhui/01/2005 (H5N1) wild-type virus. When a low-dose antigen (0.3 μg HA) vaccine was combined with aluminum hydroxide adjuvant, virus neutralization and anti-HA IgG antibodies induced in the sera of vaccinated mice showed similar levels as those in mice vaccinated with non-adjuvanted high-dose antigen (3 μg HA) vaccine. Serum antibodies had broad reactivity against highly pathogenic H5N1 viruses of both homologous and heterologous clades. All mice vaccinated with adjuvanted and non-adjuvanted rgAnhui vaccines at low and high antigen doses survived, without any significant weight loss, lethal challenge infection with homologous clade 2.3.4 viruses, including antigenic variant virus and heterologous clade 2.1.3. Mice vaccinated with low-dose antigen without adjuvant, however, exhibited 20% and 60% survival rates against clade 1 and clade 2.2 viruses, respectively; but, addition of adjuvant improved these rates to 80% and 100%, respectively. The data strongly suggest that aluminum hydroxide-adjuvanted rgAnhui vaccine can elicit broad cross-reactive and protective immunities against homologous and heterologous clades, and that the rgAnhui vaccine is a useful pre-pandemic H5N1 vaccine.     

Kinetic and HPV infection effects on cross-type neutralizing antibody and avidity responses induced by Cervarix

Background

We previously demonstrated that Cervarix^® elicits antibody responses against vaccine-related types for which clinical efficacy was demonstrated (HPV-31 and -45). Here, we evaluated the kinetics of neutralization titers and avidity of Cervarix^®-induced antibodies up to 36 months of follow-up in unexposed and HPV infected women.

Methods

A subset of women who participated in the Cost Rica HPV-16/18 Vaccine Trial had pre- and post-vaccination sera tested for antibody responses to HPV-16, -18, -31, -45, and -58 using a pseudovirion-based neutralization assay, and HPV-16 antibody avidity using an HPV-16 L1 VLP (virus-like particle)-based ELISA developed in our laboratory.

Results

In uninfected women, neutralizing antibody titers did not reach significance until after the 3rd dose for HPV-31 (month 12, p = 0.009) and HPV-45 (month 12, p = 0.003), but then persisted up to month 36 (HPV-31, p = 0.01; HPV-45, p = 0.002). Individuals infected with HPV-16 or HPV-31 at enrollment developed a significantly higher median antibody response to the corresponding HPV type after one dose, but there was not a difference between median titers after three doses compared to the HPV negative group. Median HPV-16 antibody avidity and titer increased over time up to month 12; however, the HPV-16 avidity did not correlate well with HPV-16 neutralizing antibody titers at each time point examined, except for month 6. The median avidity levels were higher in HPV-16 infected women at month 1 (p = 0.04) and lower in HPV-16 infected women at month 12 (p = 0.006) compared to the HPV negative women.

Conclusions

The persistence of cross-neutralization titers at month 36 suggests cross-reactive antibody responses are likely to persist long-term and are not influenced by infection status at enrollment. However, the weak correlation between avidity and neutralization titers emphasizes the need for examining avidity in efficacy studies to determine if high avidity antibodies play a critical role in protection against infection.     

A cell culture-derived whole-virus H5N1 vaccine induces long-lasting cross-clade protective immunity in mice which is augmented by a homologous or heterologous booster vaccination

Background

Preparation for an H5N1 influenza pandemic in humans could include priming the population in the pre-pandemic period with a vaccine produced from an existing H5N1 vaccine strain, with the possibility of boosting with a pandemic virus vaccine when it becomes available. We investigated the longevity of the immune response after one or two priming immunizations with a whole-virus H5N1 vaccine and the extent to which this can be boosted by later immunization with either a homologous or heterologous vaccine.

Methods

Mice received one or two priming immunizations with a Vero cell culture-derived, whole-virus clade 1 H5N1 vaccine formulated to contain either 750 ng or 30 ng hemagglutinin. Six months after the first priming immunization, mice received either a booster immunization with the same clade 1 vaccine or a heterologous clade 2.1 vaccine, or buffer. Humoral and cellular immune responses were evaluated before and at regular intervals after immunizations. Three weeks after booster immunization, mice were challenged with a lethal dose of wild-type H5N1 virus from clades 1, 2.1 or 2.2 and survival was monitored for 14 days.

Results

One or two priming immunizations with the 750 ng or 30 ng HA formulations, respectively, induced H5N1-neutralizing antibody titers which were maintained for ≥6 months and provided long-term cross-clade protection against wild-type virus challenge. Both humoral and cellular immune responses were substantially increased by a booster immunization after 6 months. The broadest protective immunity was provided by an immunization regimen consisting of one or two priming immunizations with a clade 1 vaccine and a boosting immunization with a clade 2.1 vaccine.

Conclusions

These data support the concept that pre-pandemic vaccination can provide robust and long-lasting H5N1 immunity which could be effectively boosted by immunization either with another pre-pandemic vaccine or with the pandemic strain 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).     

Decreased immune response to pneumococcal conjugate vaccine after 23-valent pneumococcal polysaccharide vaccine in children

Background

Pneumococcal polysaccharide vaccine (PPV) is used in children at high risk of IPD. PPV is generally not considered to induce immunologic memory, whereas pneumococcal conjugate vaccines (PCVs) elicit protective antibody responses in infants and induce immunologic memory. Little is known about the characteristics of immune responses to PCV in children who previously received PCV and PPV in series.

Objective

To characterize immune responses to 13-valent pneumococcal CRM₁₉₇ conjugate vaccine (PCV13; serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) in children vaccinated in infancy with 9-valent pneumococcal–meningococcal C-CRM₁₉₇ conjugate combination vaccine (PCV9-MnCC), followed by a toddler dose of PCV9-MnCC or 23-valent pneumococcal polysaccharide vaccine (PPV23).

Methods

Children (n = 89) who received PCV9-MnCC in infancy and PPV23 or PCV9-MnCC at age 12 months in a previous (2002–2003) study were vaccinated at age 7.5 years with PCV13; groups PPV23/PCV13 (n = 50) and PCV9/PCV13 (n = 39). Immunoglobulin (Ig)G antibodies, avidity, and opsonophagocytic activity (OPA) were measured before and at 1 and 4 weeks postvaccination.

Results

One week postvaccination, IgG levels increased significantly for all serotypes in both groups, and >97% of vaccinees achieved IgG ≥0.35 μg/ml 4 weeks after PCV13 vaccination. The PCV9/PCV13 group had higher IgG responses compared with the PPV23/PCV13 group. The upper limits of the 95% confidence intervals of the PPV23/PCV13:PCV9/PCV13 IgG geometric mean concentration ratios were <1.0 for serotypes 1, 4, 5, 9V, 18C, and 23F at 1 week. OPA and avidity results supported these findings.

Conclusions

PPV23 vaccination of toddlers may compromise subsequent responses to pneumococcal conjugate vaccines. The clinical relevance of this finding is unclear.     

Impact of pre-existing immunity on the induction of functional cross-reactive anti-hemagglutinin stalk antibodies following vaccination with an AS03 adjuvanted pandemic H1N1 vaccine

The 2009 pandemic H1N1 (A(H1N1)pdm09) virus had a highly divergent hemagglutinin (HA) compared to pre-2009 seasonal H1N1 strains. Most peoples were immunologically naïve to the A(H1N1)pdm09, although hospital workers were exposed early in the pandemic before pandemic vaccines became available. Here, we evaluated how pre-existing antibodies influence the induction of cross-functional HA stalk antibodies following A(H1N1)pdm09 vaccination.Fifty-six healthcare workers vaccinated with AS03 adjuvanted A(H1N1)pdm09 vaccine were chosen by their pre-vaccination priming status (primed HI titers ≥ 40 or unprimed < 40). We analyzed the HA head- and stalk-specific serum IgG subclasses at pre- and 21 days post-vaccination. We also assessed the functionality of the HA stalk-specific antibodies to neutralize virus and mediate antibody dependent cellular cytotoxicity (ADCC).Primed individuals had higher pre-existing HA head- and stalk-specific IgG1, as well as higher ADCC functionality of stalk antibodies. However, following vaccination with the adjuvanted pandemic vaccine, only the quantity of HA head specific IgG1 antibodies were significantly higher than in unprimed individuals. The priming status did not impact upon the cross-reactive HA stalk specific IgG antibodies or their ability to neutralize virus or induce ADCC post-vaccination. In conclusion, a single dose of AS03 adjuvanted pandemic vaccine elicited similar levels of functional antibodies in naïve and primed individuals. These findings are important for understanding the immunological factors that impact or modulate pandemic vaccine responses in humans.