[Show abstract][Hide abstract] ABSTRACT: Plasmodium falciparum (P. falciparum) malaria remains a significant cause of mortality and morbidity throughout the world. Development of an effective vaccine would be a key intervention to reduce the considerable social and economic impact of malaria.
We conducted a Phase Ia, non-randomized, clinical trial in 24 healthy, malaria-naïve adults of the chimpanzee adenovirus 63 (ChAd63) and modified vaccinia virus Ankara (MVA) replication-deficient viral vectored vaccines encoding the circumsporozoite protein (CS) of P. falciparum.
ChAd63-MVA CS administered in a heterologous prime-boost regime was shown to be safe and immunogenic, inducing high-level T cell responses to CS. With a priming ChAd63 CS dose of 5×109 vp responses peaked at a mean of 1947 SFC/million PBMC (median 1524) measured by ELIspot 7 days after the MVA boost and showed a mixed CD4+/CD8+ phenotype. With a higher priming dose of ChAd63 CS dose 5×1010 vp T cell responses did not increase (mean 1659 SFC/million PBMC, median 1049). Serum IgG responses to CS were modest and peaked at day 14 post ChAd63 CS (median antibody concentration for all groups at day 14 of 1.3 µg/ml (range 0-11.9), but persisted throughout late follow-up (day 140 median antibody concentration groups 1B & 2B 0.9 µg/ml (range 0-4.7).
ChAd63-MVA is a safe and highly immunogenic delivery platform for the CS antigen in humans which warrants efficacy testing.
PLoS ONE 12/2014; 9(12):e115161. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The development of protective vaccines against many difficult infectious pathogens will necessitate the induction of effective antibody responses. Here we assess humoral immune responses against two antigens from the blood-stage merozoite of the Plasmodium falciparum human malaria parasite - MSP1 and AMA1. These antigens were delivered to healthy malaria-naïve adult volunteers in Phase Ia clinical trials using recombinant replication-deficient viral vectors - ChAd63 to prime the immune response and MVA to boost. In subsequent Phase IIa clinical trials, immunized volunteers underwent controlled human malaria infection (CHMI) with P. falciparum to assess vaccine efficacy, whereby all but one volunteer developed low-density blood-stage parasitemia. Here we assess serum antibody responses against both the MSP1 and AMA1 antigens following i) ChAd63-MVA immunization, ii) immunization and CHMI, and iii) primary malaria exposure in the context of CHMI in unimmunized control volunteers. Responses were also assessed in a cohort of naturally-immune Kenyan adults to provide comparison with those induced by a lifetime of natural malaria exposure. Serum antibody responses against MSP1 and AMA1 were characterized in terms of i) total IgG responses before and after CHMI, ii) responses to allelic variants of MSP1 and AMA1, iii) functional growth inhibitory activity (GIA), iv) IgG avidity, and v) isotype responses (IgG1-4, IgA and IgM). These data provide the first in-depth assessment of the quality of adenovirus-MVA vaccine-induced antibody responses in humans, along with assessment of how these responses are modulated by subsequent low-density parasite exposure. Notable differences were observed in qualitative aspects of the human antibody responses against these malaria antigens depending on the means of their induction and/or exposure of the host to the malaria parasite. Given the continued clinical development of viral vectored vaccines for malaria and a range of other diseases targets, these data should help to guide further immuno-monitoring studies of vaccine-induced human antibody responses.
PLoS ONE 09/2014; 9(9):e107903. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recent human studies support historical animal studies that suggested an association between peripheral blood monocyte:lymphocyte(ML) ratio and tuberculosis(TB) disease. To evaluate generalizability of this finding, we modelled the association between peripartum ML ratio and incident TB disease within 18 months postpartum amongst 1202 HIV-infected women in South Africa, Tanzania, Uganda and Zimbabwe. The ML ratio was associated with increased risk of TB disease independently to combination antiretroviral-therapy(cART), WHO stage or CD4 count(HRadjusted=1.22;95%CI 1.07-1.4;p=0.003 per 0.1 unit increase in ML ratio).
Journal of acquired immune deficiency syndromes (1999). 09/2014;
[Show abstract][Hide abstract] ABSTRACT: The development of effective vaccines against difficult disease targets will require the identification of new subunit vaccination strategies that can induce and maintain effective immune responses in humans. Here we report on a Phase Ia clinical trial using the AMA1 antigen from the blood-stage Plasmodium falciparum malaria parasite delivered either as recombinant protein formulated with Alhydrogel adjuvant with and without CPG 7909, or using recombinant vectored vaccines - chimpanzee adenovirus ChAd63 and the orthopoxvirus MVA. A variety of promising 'mixed-modality' regimens were tested. All volunteers were primed with ChAd63, and then subsequently boosted with MVA and/or protein-in-adjuvant using either an 8 or 16 week prime-boost interval. We report on the safety of these regimens, as well as the T cell, B cell and serum antibody responses. Notably, IgG antibody responses primed by ChAd63 were comparably boosted by AMA1 protein vaccine, irrespective of whether CPG 7909 was included in the Alhydrogel adjuvant. The ability to improve the potency of a relatively weak aluminium-based adjuvant in humans, by previously priming with an adenoviral vaccine vector encoding the same antigen, thus offers a novel vaccination strategy for difficult or neglected disease targets when access to more potent adjuvants is not possible.Molecular Therapy (2014); doi:10.1038/mt.2014.157.
[Show abstract][Hide abstract] ABSTRACT: Substantial effort has been placed in developing efficacious recombinant attenuated adenovirus-based vaccines. However induction of immunity to the vector is a significant obstacle to its repeated use. Here we demonstrate that skin-based delivery of an adenovirus-based malaria vaccine, HAdV5-PyMSP1 42 , to mice using silicon microneedles induces equivalent or enhanced antibody responses to the encoded antigen, however it results in decreased anti-vector responses, compared to intradermal delivery. Microneedle-mediated vaccine priming and resultant induction of low anti-vector antibody titres permitted repeated use of the same adenovirus vaccine vector. This resulted in significantly increased antigen-specific antibody responses in these mice compared to ID-treated mice. Boosting with a heterologous vaccine; MVA-PyMSP1 42 also resulted in significantly greater antibody responses in mice primed with HAdV5-PyMSP1 42 using MN compared to the ID route. The highest protection against blood-stage malaria challenge was observed when a heterologous route of immunization (MN/ID) was used. Therefore, microneedle-mediated immunization has potential to both overcome some of the logistic obstacles surrounding needle-and-syringe-based immunization as well as to facilitate the repeated use of the same adenovirus vaccine thereby potentially reducing manufacturing costs of multiple vaccines. This could have important benefits in the clinical ease of use of adenovirus-based immunization strategies. I mmunization is the most successful strategy to combat infectious diseases. The creation of an effective Plasmodium falciparum malaria vaccine has been a much sought after goal for the vaccine community, however development of an efficacious malaria vaccine has been clinically challenging 1 . Recombinant rep-lication-defective adenoviral vectored vaccines were initially developed as candidate vaccines for induction of T cell responses against HIV-1, liver-stage malaria parasites and other intercellular pathogens 2
[Show abstract][Hide abstract] ABSTRACT: The orthodox role of the invariant chain (CD74; Ii) is in antigen presentation to CD4+ T cells, but enhanced CD8+ T cells responses have been reported after vaccination with vectored viral vaccines encoding a fusion of Ii to the antigen of interest. In this study we assessed whether fusion of the malarial antigen, ME-TRAP, to Ii could increase the vaccine-induced CD8+ T cell response. Following single or heterologous prime-boost vaccination of mice with a recombinant chimpanzee adenovirus vector, ChAd63, or recombinant modified vaccinia virus Ankara (MVA), higher frequencies of antigen-specific CD4+ and CD8+ T cells were observed, with the largest increases observed following a ChAd63-MVA heterologous prime-boost regimen. Studies in non-human primates confirmed the ability of Ii-fusion to augment the T cell response, where a 4-fold increase was maintained up to 11 weeks after the MVA boost. Of the numerous different approaches explored to increase vectored vaccine induced immunogenicity over the years, fusion to the invariant chain showed a consistent enhancement in CD8+ T cell responses across different animal species and may therefore find application in the development of vaccines against human malaria and other diseases where high levels of cell-mediated immunity are required.
PLoS ONE 06/2014; 9(6):e100538. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nucleic acid testing (NAT) for malaria parasites is an increasingly recommended diagnostic endpoint in clinical trials of vaccine and drug candidates and is also important in surveillance of malaria control and elimination efforts. A variety of reported NAT assays have been described, yet no formal external quality assurance (EQA) program provides validation for the assays in use. Here, we report results of an EQA exercise for malaria NAT assays. Among five centers conducting controlled human malaria infection trials, all centers achieved 100% specificity and demonstrated limits of detection consistent with each laboratory's pre-stated expectations. Quantitative bias of reported results compared to expected results was generally <0.5 log10 parasites/mL except for one laboratory where the EQA effort identified likely reasons for a general quantitative shift. The within-laboratory variation for all assays was low at <10% coefficient of variation across a range of parasite densities. Based on this study, we propose to create a Molecular Malaria Quality Assessment program that fulfills the need for EQA of malaria NAT assays worldwide.
PLoS ONE 05/2014; 9(5):e97398. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: TLRs 7 and 8 are pattern recognition receptors controlling antiviral host defense or autoimmune diseases. Apart from foreign and host RNA, synthetic RNA oligoribonucleotides (ORN) or small molecules of the imidazoquinoline family activate TLR7 and 8 and are being developed as therapeutic agonists. The structure-function relationships for RNA ORN and imidazoquinoline sensing and consequent downstream signaling by human TLR7 and TLR8 are unknown. Proteome- and genome-wide analyses in primary human monocyte-derived dendritic cells here showed that TLR8 sensing of RNA ORN versus imidazoquinoline translates to ligand-specific differential phosphorylation and transcriptional events. In addition, TLR7 and 8 ectodomains were found to discriminate between RNA ORN and imidazoquinolines by overlapping and nonoverlapping recognition sites to which murine loss-of-function mutations and human naturally occurring hyporesponsive polymorphisms map. Our data suggest TLR7 and TLR8 can signal in two different "modes" depending on the class of ligand. Considering RNA ORN and imidazoquinolines have been regarded as functionally interchangeable, our study highlights important functional incongruities whose understanding will be important for developing TLR7 or 8 therapeutics with desirable effector and safety profiles for in vivo application.
The Journal of Immunology 05/2014; · 5.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The introduction of the serogroup C meningococcal (MenC) conjugate vaccination has successfully controlled the burden of disease associated with this serogroup in many countries. However, considerable inter-individual variation is observed in immune responses to MenC vaccine, and little is understood of the determinants of this variability. Previously, we reported an association between single nucleotide polymorphisms (SNPs) in TLR3 and CD44 and the persistence of MenC vaccine immunity. Here we further examine polymorphisms within these two candidate genes and immune responses to MenC vaccination. Specific-IgG concentrations and serum bactericidal assay (SBA) titres were measured one month after a primary course of MenC vaccination in 318 human infants. Tagging SNPs (TagSNPs) within TLR3 and CD44 were genotyped and regional imputations carried out to screen these genes for variations associated with immunological responses to MenC vaccination. This study reports an association between an exonic variant (rs3775290, P=0.025) in TLR3 and MenC IgG concentrations, as well as an association between three SNPs in CD44 (rs3794109, P=0.021; rs3794110, P=0.022; rs112762, P=0.049) and MenC SBA titres. These data support our previous findings of an association between SNPs in TLR3 and CD44, and present novel findings implicating exonic variants in these genes with MenC vaccine responses.
[Show abstract][Hide abstract] ABSTRACT: Prior to a chimpanzee adenovirus-based (ChAd63) malaria vaccine trial, sera were collected to assess ChAd63 specific neutralizing antibody titers in Banfora (Burkina Faso). The low neutralizing antibody titers reported in both adults and children (median titer 139.1 and 35.0 respectively) is encouraging for the potential use of ChAd63 as a malaria vaccine vector.
Clinical and vaccine Immunology: CVI 04/2014; · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: T cells play a central role in the immune response to many of the world's major infectious diseases. In this study we investigated the tumour necrosis factor receptor superfamily costimulatory molecule, 4-1BBL (CD137L, TNFSF9), for its ability to increase T cell immunogenicity induced by a variety of recombinant vectored vaccines. To efficiently test this hypothesis, we assessed a number of promoters and developed a stable bi-cistronic vector expressing both the antigen and adjuvant. Co-expression of 4-1BBL, together with our model antigen TIP, was shown to increase the frequency of murine antigen-specific IFN-γ secreting CD8+ T cells in three vector platforms examined. Enhancement of the response was not limited by co-expression with the antigen, as an increase in CD8+ immunogenicity was also observed by co-administration of two vectors each expressing only the antigen or adjuvant. However, when this regimen was tested in non-human primates using a clinical malaria vaccine candidate, no adjuvant effect of 4-1BBL was observed limiting its potential use as a single adjuvant for translation into a clinical vaccine.
PLoS ONE 01/2014; 9(8):e105520. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adenoviruses are potent vectors for inducing and boosting cellular immunity to encoded recombinant antigens. However, the widespread seroprevalence of neutralizing antibodies to common human adenovirus serotypes limits their use. Simian adenoviruses do not suffer from the same drawbacks. We have constructed a replication-deficient chimpanzee adenovirus-vectored vaccine expressing the conserved influenza antigens, nucleoprotein and matrix protein 1. Here we report safety and T-cell immunogenicity following vaccination with this novel recombinant simian adenovirus, ChAdOx1 NP+M1, in a first in human dose escalation study using a 3+3 study design, followed by boosting with MVA expressing the same antigens in some volunteers. We demonstrate ChAdOx1 NP+M1 to be safe and immunogenic. ChAdOx1 is a promising vaccine vector that could be used to deliver vaccine antigens where strong cellular immune responses are required for protection.Molecular Therapy (2013); doi:10.1038/mt.2013.284.
[Show abstract][Hide abstract] ABSTRACT: Acquisition of non-sterilizing natural immunity to Plasmodium falciparum malaria has been shown in low transmission areas following multiple exposures. However conflicting data from endemic areas suggest the parasite may interfere with the induction of effective B cell responses. To-date, the impact of blood-stage parasite exposure on antigen-specific B cells has not been reported following controlled human malaria infection (CHMI). Here we analysed human B cell responses in a series of Phase I/IIa clinical trials, which include CHMI, using candidate viral vectored vaccines encoding two blood-stage antigens - merozoite surface protein 1 (MSP1) and apical membrane antigen 1 (AMA1). Previously vaccinated volunteers show boosting of pre-existing antigen-specific memory B cell (mBC) responses following CHMI. In contrast unvaccinated malaria-naïve control volunteers developed a mBC response against MSP1 but not AMA1. Serum IgG correlated with the mBC response after booster vaccination but this relationship was less well maintained following CHMI. A significant reduction in peripheral MSP1-specific mBC was observed at the point of diagnosis of blood-stage infection. This was coincident with a reduction in peripheral blood B cell subsets expressing CXCR3 and elevated serum levels of IFN-γ and CXCL9, suggesting migration away from the periphery. These CHMI data confirm that mBC and antibody responses can be induced and boosted by blood-stage parasite exposure, in support of epidemiological studies on low-level parasite exposure. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Induction of antigen-specific CD8(+) T cells offers the prospect of immunization against many infectious diseases, but no subunit vaccine has induced CD8(+) T cells that correlate with efficacy in humans. Here we demonstrate that a replication-deficient chimpanzee adenovirus vector followed by a modified vaccinia virus Ankara booster induces exceptionally high frequency T-cell responses (median >2400 SFC/10(6) peripheral blood mononuclear cells) to the liver-stage Plasmodium falciparum malaria antigen ME-TRAP. It induces sterile protective efficacy against heterologous strain sporozoites in three vaccinees (3/14, 21%), and delays time to patency through substantial reduction of liver-stage parasite burden in five more (5/14, 36%), P=0.008 compared with controls. The frequency of monofunctional interferon-γ-producing CD8(+) T cells, but not antibodies, correlates with sterile protection and delay in time to patency (Pcorrected=0.005). Vaccine-induced CD8(+) T cells provide protection against human malaria, suggesting that a major limitation of previous vaccination approaches has been the insufficient magnitude of induced T cells.
[Show abstract][Hide abstract] ABSTRACT: Virus diversity and escape from immune responses are the biggest challenges to the development of an effective vaccine against HIV-1. We hypothesized that T-cell vaccines targeting the most conserved regions of the HIV-1 proteome, which are common to most variants and bear fitness costs when mutated, will generate effectors that efficiently recognize and kill virus-infected cells early enough after transmission to potentially impact on HIV-1 replication and will do so more efficiently than whole protein-based T-cell vaccines. Here, we describe the first-ever administration of conserved immunogen vaccines vectored using prime-boost regimens of DNA, simian adenovirus and modified vaccinia virus Ankara to uninfected UK volunteers. The vaccine induced high levels of effector T cells that recognized virus-infected autologous CD4(+) cells and inhibited HIV-1 replication by up to 5.79 log10. The virus inhibition was mediated by both Gag- and Pol- specific effector CD8(+) T cells targeting epitopes that are typically subdominant in natural infection. These results provide proof of concept for using a vaccine to target T cells at conserved epitopes, showing that these T cells can control HIV-1 replication in vitro.Molecular Therapy (2013); doi:10.1038/mt.2013.248.
[Show abstract][Hide abstract] ABSTRACT: Background. Eight decades ago, the ratio of monocytes and lymphocytes was noted to affect outcomes of mycobacterial infection in rabbits. Recent transcriptomic studies support a role for relative proportions of myeloid and lymphoid transcripts in TB outcomes. The ratio of peripheral blood monocytes: lymphocytes (ML ratio) is known to be governed by haematopoeitic stem cells(HSC) with distinct biases.Methods. The predictive value of the baseline ML ratio was modeled in two prospective cohorts of adults starting cART in South Africa (primary n=1862 and replication n=345). Incident TB was diagnosed with clinical, radiographic and microbiologic methods per contemporary guidelines. Kaplan-Meier survival analyses and Cox proportional hazards modeling were conducted.Results. The incidence rate of TB differed significantly by baseline ML ratio: 32.61(95%CI 15.38-61.54); 16.36(95% CI 12.39-21.23), and 51.80(95% CI 23.10-101.71) per 1000 patient-years for ML ratio<5(th) percentile; 5-95(th) centile; and >95(th) centile respectively(p=0.007). Neither monocyte nor lymphocyte counts alone were associated with TB. Adjusting for sex, WHO stage, CD4+ T-cell counts and previous TB, hazards of disease were significantly higher for patients with ML ratio <5(th) or >95(th) percentile(adjusted HR 2.47;95%CI 1.39-4.40;p=0.002).Conclusions. The ML ratio may be a useful, readily available tool to stratify risk of TB disease and suggests involvement of HSC bias in TB pathogenesis.
The Journal of Infectious Diseases 09/2013; · 5.85 Impact Factor