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Background: Overcoming antigenic diversity is a key challenge in the development of effective Plasmodium falciparum malaria vaccines. Strategies that promote the generation of antibodies targeting conserved epitopes of vaccine antigens may provide protection against diverse parasites strains. Understanding differences between vaccine-induced and naturally acquired immunity is important to achieving this goal. Methods: We analyzed antibodies generated in a phase 1 human vaccine trial, MSP2-C1, which included 2 allelic forms of MSP2, an abundant vaccine antigen on the merozoite surface. Vaccine-induced responses were assessed for functional activity against multiple parasite strains, and cross-reactivity of antibodies was determined using competition ELISA and epitope mapping approaches. Results: Vaccination induced cytophilic antibody responses with strain-transcending opsonic phagocytosis and complement-fixing function. In contrast to antibodies acquired via natural infection, vaccine-induced antibodies were directed towards conserved epitopes at the C-terminus of MSP2, whereas naturally acquired antibodies mainly targeted polymorphic epitopes. Functional activity of C-terminal–targeted antibodies was confirmed using monoclonal antibodies that promoted opsonic phagocytosis against multiple parasite strains. Conclusion: Vaccination generated markedly different responses to polymorphic antigens than naturally acquired immunity and targeted conserved functional epitopes. Induction of antibodies targeting conserved regions of malaria antigens provides a promising vaccine strategy to overcome antigenic diversity for developing effective malaria vaccines.

Significance Malaria still kills hundreds of thousands of children each year. Malaria vaccine development is complicated by high levels of parasite genetic diversity, which makes single target vaccines vulnerable to the development of variant-specific immunity. To overcome this hurdle, we systematically screened a panel of 29 blood-stage antigens from the most deadly human malaria parasite, Plasmodium falciparum. We identified several targets that were able to inhibit erythrocyte invasion in two genetically diverse strains. Testing these targets in combination identified several pairs that blocked invasion more effectively in combination than in isolation. Video microscopy and studies of natural immune responses to malaria in patients suggest that targeting multiple steps in invasion is more likely to produce a synergistic vaccine response., A highly effective vaccine would be a valuable weapon in the drive toward malaria elimination. No such vaccine currently exists, and only a handful of the hundreds of potential candidates in the parasite genome have been evaluated. In this study, we systematically evaluated 29 antigens likely to be involved in erythrocyte invasion, an essential developmental stage during which the malaria parasite is vulnerable to antibody-mediated inhibition. Testing antigens alone and in combination identified several strain-transcending targets that had synergistic combinatorial effects in vitro, while studies in an endemic population revealed that combinations of the same antigens were associated with protection from febrile malaria. Video microscopy established that the most effective combinations targeted multiple discrete stages of invasion, suggesting a mechanistic explanation for synergy. Overall, this study both identifies specific antigen combinations for high-priority clinical testing and establishes a generalizable approach that is more likely to produce effective vaccines.

The development of effective malaria vaccines and immune biomarkers of malaria is a high priority for malaria control and elimination. Ags expressed by merozoites of Plasmodium falciparum are likely to be important targets of human immunity and are promising vaccine candidates, but very few Ags have been studied. We developed an approach to assess Ab responses to a comprehensive repertoire of merozoite proteins and investigate whether they are targets of protective Abs. We expressed 91 recombinant proteins, located on the merozoite surface or within invasion organelles, and screened them for quality and reactivity to human Abs. Subsequently, Abs to 46 proteins were studied in a longitudinal cohort of 206 Papua New Guinean children to define Ab acquisition and associations with protective immunity. Ab responses were higher among older children and those with active parasitemia. High-level Ab responses to rhoptry and microneme proteins that function in erythrocyte invasion were identified as being most strongly associated with protective immunity compared with other Ags. Additionally, Abs to new or understudied Ags were more strongly associated with protection than were Abs to current vaccine candidates that have progressed to phase 1 or 2 vaccine trials. Combinations of Ab responses were identified that were more strongly associated with protective immunity than responses to their single-Ag components. This study identifies Ags that are likely to be key targets of protective human immunity and facilitates the prioritization of Ags for further evaluation as vaccine candidates and/or for use as biomarkers of immunity in malaria surveillance and control.

BACKGROUND: Metastatic germ cell tumors remain potentially curable when treated with salvage chemotherapy at first relapse. In the present phase I/II study, we sought to improve on the response rate and duration of the TIP (paclitaxel, ifosfamide, cisplatin) regimen by adding gemcitabine (Gem-TIP).MATERIALS AND METHODS: Twenty patients were recruited after failure of first-line cisplatin-containing chemotherapy. The primary objectives were to determine the maximum tolerated dose of gemcitabine when combined with TIP and to establish the dose intensity of the TIP drugs in this combination. The secondary objectives were the response rates, failure-free survival, and overall survival.RESULTS: The maximum tolerated dose of gemcitabine was 1200 mg/m2. The mean relative dose intensity was 95% (95% confidence interval [CI], 90.2%-99.2%) for gemcitabine, 96% (95% CI, 92.9%-98.7%) for paclitaxel, 92% (95% CI, 84.5%-98.8%) for ifosfamide, and 94% (95% CI, 89.3%-99.0%) for cisplatin. The overall complete response rate was 50%; another 30% of the patients achieved a partial response. The 1-year failure-free survival and overall survival rates were 68% (95% CI, 43%-84%) and 89.5% (95% CI, 64%-97%), respectively.CONCLUSION: Gemcitabine can be added to TIP chemotherapy at the full dose, with manageable toxicity and no detrimental effect on the dose intensity of the TIP drugs. The response rate and duration were improved compared with those reported from the Medical Research Council TIP trial; further evaluation is warranted.

Background: Platinum etoposide doublet chemotherapy remains the standard of care for SCLC; newer combination regimens have failed to improve outcome. A subgroup of patients with apparently better long-term survival present with autoimmune paraneoplastic syndromes. These reflect cross reactivity of anti-tumour immune responses with self-antigens, most frequently neuronal antigens, and suggest that SCLC is susceptible to immune control. Our study examines for the first time, whether addition of the immune stimulating anti-CTLA4 antibody Ipilimumab to carboplatin/etoposide chemotherapy can increase anti-tumour activity and whether this might come at the cost of extra immune related neurological toxicity. Methods: This phase II study examines the efficacy and toxicity of Ipilimumab (10 mg/kg) together with Carboplatin (AUC=6) and Etoposide (120 mg/m2 IV day1, 100mg BD PO days 2 and 3) chemotherapy in previously untreated patients with extensive stage (ES) SCLC. Ipilimumab was introduced in responding patients at cycles 3-6 with planned 3-monthly maintenance Ipilimumab. Primary end point is progression free survival at 1 year; secondary endpoints include 1 year overall survival and Immune related progression free survival (irPFS). Results: 39 of a planned 40 patients have entered the study with a median age of 58 yrs (range 47-84); 64% are male. Patients received at least one cycle of Ipilimumab. In 61.1% [95% CI: 44.9-75..2] >grade 3 adverse events were seen, assessed by the investigators as possibly ipilimumab related in 41.7% [95% CI: 27.1, 57.8]. Two patients (6%) had ipilimumab related neurological events, of these one was fatal, presenting like an anti-Hu syndrome. Both events occurred in patients with positive baseline anti-neuronal antibodies. Conclusions: Our multi centre study has demonstrates for the first time that chemo-immunotherapy with ICE is deliverable in ES SCLC, but with an appreciable burden of immune related toxicity. Two significant neurological immune mediated events were seen, one fatal. The data reinforce the view that SCLC is immunogenic and that immunological visibility of the tumour can link to anti neuronal immune events. Disclosure: C. Ottensmeier: Funding for this study was by an educational grant from BMS and Cancer Research UK. The trial uses the BMS proprietary compound Ipilimumab; J. Cave: Conference attendance support from BMS; M. Wheater: Conference attendance support from BMS; C. Mulatero: I have undertaken consultancy/advisory work for BMS (ipilimumab) and for Pfizer (although not about tremelimumab), and have received honoraria to attend meetings from BMS; V. Potter: I have received honoraria and consultancy fees from Roche, GSK and Lilly, but nothing from BMS; S. Danson: I sat on an advisory board and received travel expenses for a meeting from BMS - this was about 4 years ago; R. Griffiths: I have received honoraria and consultancy fees from Pfizer, Pierre-Fabre, GSK and Novartis, but nil from BMS. All other authors have declared no conflicts of interest.

4560 Background: Cure is possible for patients with relapsed germ cell tumours using further intensive cisplatin based combination chemotherapy. The Medical Research Council TIP trial reported a co...

Background: In a previous Phase 1/2b malaria vaccine trial testing the 3D7 isoform of the malaria vaccine candidate Merozoite surface protein 2 (MSP2), parasite densities in children were reduced by 62%. However, breakthrough parasitemias were disproportionately of the alternate dimorphic form of MSP2, the FC27 genotype. We therefore undertook a dose-escalating, double-blinded, placebo-controlled Phase 1 trial in healthy, malaria-naive adults of MSP2-C1, a vaccine containing recombinant forms of the two families of msp2 alleles, 3D7 and FC27 (EcMSP2-3D7 and EcMSP2-FC27), formulated in equal amounts with Montanide® ISA 720 as a water-in-oil emulsion. Methodology/Principal Findings: The trial was designed to include three dose cohorts (10, 40, and 80 μg), each with twelve subjects receiving the vaccine and three control subjects receiving Montanide® ISA 720 adjuvant emulsion alone, in a schedule of three doses at 12-week intervals. Due to unexpected local reactogenicity and concern regarding vaccine stability, the trial was terminated after the second immunisation of the cohort receiving the 40 μg dose; no subjects received the 80 μg dose. Immunization induced significant IgG responses to both isoforms of MSP2 in the 10 μg and 40 μg dose cohorts, with antibody levels by ELISA higher in the 40 μg cohort. Vaccine-induced antibodies recognised native protein by Western blots of parasite protein extracts and by immunofluorescence microscopy. Although the induced anti-MSP2 antibodies did not directly inhibit parasite growth in vitro, IgG from the majority of individuals tested caused significant antibody-dependent cellular inhibition (ADCI) of parasite growth. Conclusions/Significance: As the majority of subjects vaccinated with MSP2-C1 developed an antibody responses to both forms of MSP2, and that these antibodies mediated ADCI provide further support for MSP2 as a malaria vaccine candidate. However, in view of the reactogenicity of this formulation, further clinical development of MSP2-C1 will require formulation of MSP2 in an alternative adjuvant. Trial Registration: Australian New Zealand Clinical Trials Registry 12607000552482.