To determine whether the vaccination protocols elicited T cell-mediated immune responses, we employed several methods of analyses

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To determine whether the vaccination protocols elicited T cell-mediated immune responses, we employed several methods of analyses. CSP, and recognized sporozoites expressing the alleles VK210 and VK247. The vaccine formulations described in this work should be useful for the further development of an anti-vaccine. INTRODUCTION Human malaria infection starts when an mosquito injects sporozoites of species into the skin of a person. KL1333 The sporozoites traverse the skin, enter the blood circulation, and infect hepatocytes. While sporozoites are in the skin or migrating to the liver, their infectivity can be abolished by antibodies against the circumsporozoite antigen (CSP). The neutralizing antibodies are predominantly, but not exclusively, directed against the immunodominant B epitopes in the CSP repeat domain (reviewed in reference 1). Multiple trials with experimental animals and more recently with humans provide a solid basis for Lepr the use of vaccines against CSP to prevent malaria. Thus far, the only vaccine against the deadly parasite tested in a phase III clinical trial is usually RTS,S, a fusion protein between portions of CSP and the hepatitis B surface antigen (S) that is administered in a powerful adjuvant system (AS), either an oil-in-water emulsion (AS02) or a liposomal suspension (AS01). These adjuvants contain monophosphoryl lipid A (a detoxified form of lipopolysaccharide [LPS]) and QS21 (purified saponin from reported protective efficacies of 32 to 50%. Protective immunity largely correlated with the serum levels of specific IgG antibodies against the repeats in the CSP antigen and, to a lesser extent, with the frequency of CD4+ T cells expressing two or more of the following cytokines: interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-), and gamma interferon (IFN-) (2). One of these formulations (RTS,S/AS01E) is currently being tested in a large phase III clinical trial of African children living in areas where malaria is usually endemic. The results reported from this trial indicate 49.5 or 30.1% protective efficacy during a 14-month period postvaccination in 5- to 17-month-old or 6- to 12-week-old African children, respectively (3, 4). These trials and previous human trials have established that immunodominant CSP is usually a worthwhile candidate antigen to be included in future vaccine formulations to combat malaria infections, including infections with is the most widespread malaria-causing species in the world and is the second most prevalent. It is estimated that more than 2.8 billion people are at risk of contracting infection (5). Nevertheless, only three clinical trials based on subunit vaccines have KL1333 KL1333 been completed (http://www.clinicaltrials.gov/). One complication of vaccine development is usually that, in contrast to CSP have been described. The two most common CSP alleles are VK210 and VK247 (6, 7). A third allelic form exists at a low frequency (8,C12). The main variation among these allelic forms is in the central repeat region of CSP, which is KL1333 a possible target of neutralizing antibodies. To generate a vaccine with universal coverage against malaria strains, we tested a prime-boost regimen using recombinant proteins and adenovirus vectors expressing epitopes from the three CSP alleles as antigens. We used two approaches to generate these vaccines. The first consisted of mixing recombinant proteins expressing the three CSP alleles to generate a vaccine. Additionally, we generated a single recombinant fusion protein called PvCSP-All-CS-epitopes that contains epitopes from the three CSP alleles. We primed animals with either a simian or a human recombinant replication-defective adenovirus vector expressing PvCSP-All-CS-epitopes in some experiments. In most of the experiments, recombinant antigens were administered in a formulation made up of the adjuvant poly(IC). We compared the immunogenicities of homologous (protein-protein) and heterologous KL1333 (adenovirus-protein) immunization regimens. We primarily measured the magnitude and longevity of the serum IgG responses to all of CSP and the CSP domains. In selected experiments, we also evaluated the cell-mediated immune response to CSP. MATERIALS AND METHODS Ethics statement. This study was carried out in strict accordance with the recommendations.