Complementary measurement of nontyphoidal specific IgG and IgA antibodies in oral fluid and serum.

Objectives: Immuno-epidemiological studies of orally acquired, enteric pathogens such as nontyphoidal (NTS) often focus on serological measures of immunity, ignoring potentially relevant oral mucosal responses. In this study we sought to assess the levels and detectability of both oral fluid and serum IgG and IgA to NTS antigens, in endemic and non-endemic populations.

Methods: IgG and IgA antibodies specific for Typhimurium and Enteritidis O antigen and phase 1 flagellin were assessed using Enzyme Linked Immunosorbent Assay (ELISA).

Induction of Functional Specific Antibodies, IgG-Secreting Plasmablasts and Memory B Cells Following BCG Vaccination.

Tuberculosis (TB) is a major global health problem and the only currently-licensed vaccine, BCG, is inadequate. Many TB vaccine candidates are designed to be given as a boost to BCG; an understanding of the BCG-induced immune response is therefore critical, and the opportunity to relate this to circumstances where BCG does confer protection may direct the design of more efficacious vaccines. While the T cell response to BCG vaccination has been well-characterized, there is a paucity of literature on the humoral response.

Poor CD4 T Cell Immunogenicity Limits Humoral Immunity to Transmission-Blocking Candidate Pfs25 in Humans.

transmission-blocking vaccines (TBVs) targeting the Pfs25 antigen have shown promise in mice but the same efficacy has never been achieved in humans. We have previously published pre-clinical data related to a TBV candidate Pfs25-IMX313 encoded in viral vectors which was very promising and hence progressed to human clinical trials. The results from the clinical trial of this vaccine were very modest.

Safety and Immunogenicity of ChAd63/MVA Pfs25-IMX313 in a Phase I First-in-Human Trial.

Background: Transmission blocking vaccines targeting the sexual-stages of the malaria parasite could play a major role to achieve elimination and eradication of malaria. The Pfs25 protein (Pfs25) is the most clinically advanced candidate sexual-stage antigen. IMX313, a complement inhibitor C4b-binding protein that forms heptamers with the antigen fused to it, improve antibody responses.

Protein/AS01 vaccination elicits stronger, more Th2-skewed antigen-specific human T follicular helper cell responses than heterologous viral vectors.

Interactions between B cells and CD4 T follicular helper (Tfh) cells are key determinants of humoral responses. Using samples from clinical trials performed with the malaria vaccine candidate antigen merozoite protein (PfRH5), we compare the frequency, phenotype, and gene expression profiles of PfRH5-specific circulating Tfh (cTfh) cells elicited by two leading human vaccine delivery platforms: heterologous viral vector prime boost and protein with AS01 adjuvant. We demonstrate that the protein/AS01 platform induces a higher-magnitude antigen-specific cTfh cell response and that this correlates with peak anti-PfRH5 IgG concentrations, frequency of PfRH5-specific memory B cells, and antibody functionality.

Evaluation of a standardised Vi poly-l-lysine ELISA for serology of Vi capsular polysaccharide antibodies.

Typhoid vaccines based on protein-conjugated capsular Vi polysaccharide (TCVs) prevent typhoid in infants and young children. Analysis of the serum anti-Vi IgG response following immunisation against typhoid confirms the immunogenicity of TCVs and forms an important part of the pathway to licensing. Comparative studies could expedite the licencing process, and the availability of a standardised ELISA method alongside the 1st International Standard (IS) 16/138 for anti-typhoid capsular Vi polysaccharide IgG (human) will facilitate this process.

Structural basis for inhibition of Plasmodium vivax invasion by a broadly neutralizing vaccine-induced human antibody.

The most widespread form of malaria is caused by Plasmodium vivax. To replicate, this parasite must invade immature red blood cells through a process requiring interaction of the P. vivax Duffy binding protein (PvDBP) with its human receptor, the Duffy antigen receptor for chemokines.

Therapeutic Monoclonal Antibodies for Ebola Virus Infection Derived from Vaccinated Humans.

We describe therapeutic monoclonal antibodies isolated from human volunteers vaccinated with recombinant adenovirus expressing Ebola virus glycoprotein (EBOV GP) and boosted with modified vaccinia virus Ankara. Among 82 antibodies isolated from peripheral blood B cells, almost half neutralized GP pseudotyped influenza virus. The antibody response was diverse in gene usage and epitope recognition.

Changes in Serological Immunology Measures in UK and Kenyan Adults Post-controlled Human Malaria Infection.

The timing of infection is closely determined in controlled human malaria infection (CHMI) studies, and as such they provide a unique opportunity to dissect changes in immunological responses before and after a single infection. The first Kenyan Challenge Study (KCS) (Pan African Clinical Trial Registry: PACTR20121100033272) was performed in 2013 with the aim of establishing the CHMI model in Kenya. This study used aseptic, cryopreserved, attenuated sporozoites administered by needle and syringe (PfSPZ Challenge) and was the first to evaluate parasite dynamics post-CHMI in individuals with varying degrees of prior exposure to malaria.

Demonstration of the Blood-Stage Plasmodium falciparum Controlled Human Malaria Infection Model to Assess Efficacy of the P. falciparum Apical Membrane Antigen 1 Vaccine, FMP2.1/AS01.

Background: Models of controlled human malaria infection (CHMI) initiated by mosquito bite have been widely used to assess efficacy of preerythrocytic vaccine candidates in small proof-of-concept phase 2a clinical trials. Efficacy testing of blood-stage malaria parasite vaccines, however, has generally relied on larger-scale phase 2b field trials in malaria-endemic populations. We report the use of a blood-stage P.

Preclinical Assessment of Viral Vectored and Protein Vaccines Targeting the Duffy-Binding Protein Region II of Plasmodium Vivax.

Malaria vaccine development has largely focused on Plasmodium falciparum; however, a reawakening to the importance of Plasmodium vivax has spurred efforts to develop vaccines against this difficult to treat and at times severe form of relapsing malaria, which constitutes a significant proportion of human malaria cases worldwide. The almost complete dependence of P. vivax red blood cell invasion on the interaction of the P.

Increased sample volume and use of quantitative reverse-transcription PCR can improve prediction of liver-to-blood inoculum size in controlled human malaria infection studies.

Background: Controlled human malaria infection (CHMI) studies increasingly rely on nucleic acid test (NAT) methods to detect and quantify parasites in the blood of infected participants. The lower limits of detection and quantification vary amongst the assays used throughout the world, which may affect the ability of mathematical models to accurately estimate the liver-to-blood inoculum (LBI) values that are used to judge the efficacy of pre-erythrocytic vaccine and drug candidates.

Methods: Samples were collected around the time of onset of pre-patent parasitaemia from subjects who enrolled in two different CHMI clinical trials.

Evaluating controlled human malaria infection in Kenyan adults with varying degrees of prior exposure to Plasmodium falciparum using sporozoites administered by intramuscular injection.

Background: Controlled human malaria infection (CHMI) studies are a vital tool to accelerate vaccine and drug development. As CHMI trials are performed in a controlled environment, they allow unprecedented, detailed evaluation of parasite growth dynamics (PGD) and immunological responses. However, CHMI studies have not been routinely performed in malaria-endemic countries or used to investigate mechanisms of naturally-acquired immunity (NAI) to Plasmodium falciparum.

Assessment of humoral immune responses to blood-stage malaria antigens following ChAd63-MVA immunization, controlled human malaria infection and natural exposure.

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.

Combining viral vectored and protein-in-adjuvant vaccines against the blood-stage malaria antigen AMA1: report on a phase 1a clinical trial.

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 1a 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.

Analysis of human B-cell responses following ChAd63-MVA MSP1 and AMA1 immunization and controlled malaria infection.

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 that 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).

Protective CD8+ T-cell immunity to human malaria induced by chimpanzee adenovirus-MVA immunisation.

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.

Assessment of immune interference, antagonism, and diversion following human immunization with biallelic blood-stage malaria viral-vectored vaccines and controlled malaria infection.

Overcoming antigenic variation is one of the major challenges in the development of an effective vaccine against Plasmodium falciparum, a causative agent of human malaria. Inclusion of multiple Ag variants in subunit vaccine candidates is one strategy that has aimed to overcome this problem for the leading blood-stage malaria vaccine targets, that is, merozoite surface protein 1 (MSP1) and apical membrane Ag 1 (AMA1). However, previous studies, utilizing malaria Ags, have concluded that inclusion of multiple allelic variants, encoding altered peptide ligands, in such a vaccine may be detrimental to both the priming and in vivo restimulation of Ag-experienced T cells.

ChAd63-MVA-vectored blood-stage malaria vaccines targeting MSP1 and AMA1: assessment of efficacy against mosquito bite challenge in humans.

The induction of cellular immunity, in conjunction with antibodies, may be essential for vaccines to protect against blood-stage infection with the human malaria parasite Plasmodium falciparum. We have shown that prime-boost delivery of P. falciparum blood-stage antigens by chimpanzee adenovirus 63 (ChAd63) followed by the attenuated orthopoxvirus MVA is safe and immunogenic in healthy adults.

Phase Ia clinical evaluation of the safety and immunogenicity of the Plasmodium falciparum blood-stage antigen AMA1 in ChAd63 and MVA vaccine vectors.

Background: Traditionally, vaccine development against the blood-stage of Plasmodium falciparum infection has focused on recombinant protein-adjuvant formulations in order to induce high-titer growth-inhibitory antibody responses. However, to date no such vaccine encoding a blood-stage antigen(s) alone has induced significant protective efficacy against erythrocytic-stage infection in a pre-specified primary endpoint of a Phase IIa/b clinical trial designed to assess vaccine efficacy. Cell-mediated responses, acting in conjunction with functional antibodies, may be necessary for immunity against blood-stage P.

Clinical assessment of a recombinant simian adenovirus ChAd63: a potent new vaccine vector.

Background: Vaccine development in human Plasmodium falciparum malaria has been hampered by the exceptionally high levels of CD8(+) T cells required for efficacy. Use of potently immunogenic human adenoviruses as vaccine vectors could overcome this problem, but these are limited by preexisting immunity to human adenoviruses.

Methods: From 2007 to 2010, we undertook a phase I dose and route finding study of a new malaria vaccine, a replication-incompetent chimpanzee adenovirus 63 (ChAd63) encoding the preerythrocytic insert multiple epitope thrombospondin-related adhesion protein (ME-TRAP; n = 54 vaccinees) administered alone (n = 28) or with a modified vaccinia virus Ankara (MVA) ME-TRAP booster immunization 8 weeks later (n = 26).

Phase Ia clinical evaluation of the Plasmodium falciparum blood-stage antigen MSP1 in ChAd63 and MVA vaccine vectors.

Efficacy trials of antibody-inducing protein-in-adjuvant vaccines targeting the blood-stage Plasmodium falciparum malaria parasite have so far shown disappointing results. The induction of cell-mediated responses in conjunction with antibody responses is thought to be one alternative strategy that could achieve protective efficacy in humans. Here, we prepared chimpanzee adenovirus 63 (ChAd63) and modified vaccinia virus Ankara (MVA) replication-deficient vectors encoding the well-studied P.