Safety and Efficacy of Immunization with a Late-Liver-Stage Attenuated Malaria Parasite.

Background: Currently licensed and approved malaria subunit vaccines provide modest, short-lived protection against malaria. Immunization with live-attenuated malaria parasites is an alternative vaccination strategy that has potential to improve protection.

Methods: We conducted a double-blind, controlled clinical trial to evaluate the safety, side-effect profile, and efficacy of immunization, by means of mosquito bites, with a second-generation genetically attenuated parasite (GA2) - a single knockout NF54 parasite (sporozoite form) with extended development into the liver stage.

Resistance of Anopheles gambiae s.s. against commonly used insecticides and implication of cytochrome P450 monooxygenase in resistance to pyrethroids in Lambaréné (Gabon).

Background: Insecticides are a crucial component of vector control. However, resistance constitute a threat on their efficacy and the gains obtained over the years through malaria vector control. In Gabon, little data on phenotypic insecticide resistance in Anopheles vectors are published, compromising the rational implementation of resistance management strategies.

The effect of Plasmodium falciparum exposure and maternal anti-circumsporozoite protein antibodies on responses to RTS,S/AS01 vaccination in infants and children: an ancillary observational immunological study to a phase 3, randomised clinical trial.

Background: The RTS,S/AS01 malaria vaccine showed lower antibody response and protective efficacy in infants aged 6-12 weeks compared with children aged 5-17 months (for whom this vaccine is recommended). We aimed to study the effect of previous Plasmodium falciparum exposure on the antibody responses to RTS,S/AS01 vaccination in infants and children, and the mediating effect of baseline (including maternal) anti-circumsporozoite protein (CSP) antibodies.

Methods: In this observational study, we included children and infants from six African countries (Burkina Faso, Gabon, Ghana, Kenya, Mozambique, and Tanzania) enrolled in the MAL067 immunology ancillary study of the RTS,S/AS01 phase 3 clinical trial from March 27, 2009, to Jan 21, 2011.

Slow clearance of histidine-rich protein-2 in Gabonese with uncomplicated malaria.

Unlabelled: Malaria rapid diagnostic tests (RDTs), which detect (Pf)-specific histidine-rich protein-2 (HRP2), have increasing importance for the diagnosis and control of malaria, especially also in regions where routine diagnosis by microscopy is not available. HRP2-based RDTs have a similar sensitivity to expert microscopy, but their reported low specificity can lead to high false positivity rates, particularly in high-endemic areas. Despite the widespread use of RDTs, models investigating the dynamics of HRP2 clearance following Pf treatment focus rather on short-term clearance of the protein.

Reported healthcare-seeking of loiasis patients and estimation of the associated monetary burden in Gabon: Data from a cross-sectional survey.

Background: Loiasis is a disease of relevance in endemic populations and there has been advocacy for its inclusion on the World Health Organization's neglected tropical diseases list. As loiasis-related healthcare-seeking behaviors and related costs are unknown, we aimed to evaluate these aspects in a population residing in an endemic region in Gabon.

Methods: Data were collected during a community-based, cross-sectional study assessing the disease burden due to loiasis.

Genetic diversity of in sub-Saharan Africa: a two-marker genotyping approach for molecular epidemiological studies.

Introduction: is the most common non-falciparum species in sub-Saharan Africa. Despite this, data on its genetic diversity is scarce. Therefore, we aimed to establish a genotyping approach based on size polymorphic regions that can be easily applied in molecular epidemiological studies.

Machine learning prediction of malaria vaccine efficacy based on antibody profiles.

Immunization through repeated direct venous inoculation of Plasmodium falciparum (Pf) sporozoites (PfSPZ) under chloroquine chemoprophylaxis, using the PfSPZ Chemoprophylaxis Vaccine (PfSPZ-CVac), induces high-level protection against controlled human malaria infection (CHMI). Humoral and cellular immunity contribute to vaccine efficacy but only limited information about the implicated Pf-specific antigens is available. Here, we examined Pf-specific antibody profiles, measured by protein arrays representing the full Pf proteome, of 40 placebo- and PfSPZ-immunized malaria-naïve volunteers from an earlier published PfSPZ-CVac dose-escalation trial.

Eosinophils, basophils and myeloid-derived suppressor cells in chronic Loa loa infection and its treatment in an endemic setting.

Background: Chronic infection by Loa loa remains an unsolved immunological paradox. Despite harboring subcutaneously migrating adult worms and often high densities of microfilariae, most patients experience only relatively mild symptoms, yet microfilaricidal treatment can trigger life-threatening inflammation. Here, we investigated innate cell populations hypothesized to play a role in these two faces of the disease, in an endemic population in Gabon.

Immune responses associated with protection induced by chemoattenuated PfSPZ vaccine in malaria-naive Europeans.

Vaccination of malaria-naive volunteers with a high dose of Plasmodium falciparum sporozoites chemoattenuated by chloroquine (CQ) (PfSPZ-CVac [CQ]) has previously demonstrated full protection against controlled human malaria infection (CHMI). However, lower doses of PfSPZ-CVac [CQ] resulted in incomplete protection. This provides the opportunity to understand the immune mechanisms needed for better vaccine-induced protection by comparing individuals who were protected with those not protected.

Dynamics of Plasmodium species and genotype diversity in adults with asymptomatic infection in Gabon.

Objectives: We investigated the diversity and dynamics of Plasmodium infection in serially collected samples from asymptomatic participants of a clinical trial assessing the efficacy and safety of ivermectin in Gabon. We checked whether the baseline sample reflected the P. falciparum genotype and Plasmodium species diversity seen over 7 days of follow-up.

Analysis of diagnostic test outcomes in a large loiasis cohort from an endemic region: Serological tests are often false negative in hyper-microfilaremic infections.

Background: The parasitic disease loiasis is associated with significant morbidity and mortality. Individuals with hyper-microfilaremia (greater than 20,000 microfilariae per mL of blood) may suffer from serious treatment-related or spontaneous adverse events. Diagnosing loiasis remains complex and primarily relies on direct parasite detection.

Anopheles gambiae s.s. resistance to pyrethroids and DDT in semi-urban and rural areas of the Moyen-Ogooué Province, Gabon.

Background: Pyrethroids are the main insecticides used in vector control for malaria. However, their extensive use in the impregnation of long-lasting insecticidal nets (LLINs) and indoor residual spraying has led to the development of resistance, threatening its success as a tool for malaria control. Baseline data prior to large scale distribution of LLINs are important for the implementation of efficient strategies.

Efficacy and safety of ivermectin for the treatment of Plasmodium falciparum infections in asymptomatic male and female Gabonese adults - a pilot randomized, double-blind, placebo-controlled single-centre phase Ib/IIa clinical trial.

Background: Ivermectin's mosquitocidal effect and in vitro activity against Plasmodium falciparum asexual stages are known. Its in vivo blood-schizonticidal efficacy is unknown. Ivermectin's tolerability and efficacy against P.

Comparative analysis of spike-specific IgG Fc glycoprofiles elicited by adenoviral, mRNA, and protein-based SARS-CoV-2 vaccines.

IgG antibodies are important mediators of vaccine-induced immunity through complement- and Fc receptor-dependent effector functions. Both are influenced by the composition of the conserved -linked glycan located in the IgG Fc domain. Here, we compared the anti-Spike (S) IgG1 Fc glycosylation profiles in response to mRNA, adenoviral, and protein-based COVID-19 vaccines by mass spectrometry (MS).

Sporozoite immunization: innovative translational science to support the fight against malaria.

Introduction: Malaria, a devastating febrile illness caused by protozoan parasites, sickened 247,000,000 people in 2021 and killed 619,000, mostly children and pregnant women in sub-Saharan Africa. A highly effective vaccine is urgently needed, especially for (Pf), the deadliest human malaria parasite.

Areas Covered: Sporozoites (SPZ), the parasite stage transmitted by mosquitoes to humans, are the only vaccine immunogen achieving >90% efficacy against Pf infection.

HHV-6 infections in hospitalized young children of Gabon.

Purpose: Fever is a common cause for hospitalization among the pediatric population. The spectrum of causative agents is diverse. Human herpesvirus 6 (HHV-6) is a ubiquitous virus that often causes hospitalization of children in western countries.

Prostration and the prognosis of death in African children with severe malaria.

Objectives: Malaria is still one of the main reasons for hospitalization in children living in sub-Saharan Africa. Rapid risk stratification at admission is essential for optimal medical care and improved prognosis. Whereas coma, deep breathing, and, to a lesser degree, severe anemia are established predictors of malaria-related death, the value of assessing prostration for risk stratification is less certain.

The exception that proves the rule: Virulence gene expression at the onset of Plasmodium falciparum blood stage infections.

Controlled human malaria infections (CHMI) are a valuable tool to study parasite gene expression in vivo under defined conditions. In previous studies, virulence gene expression was analyzed in samples from volunteers infected with the Plasmodium falciparum (Pf) NF54 isolate, which is of African origin. Here, we provide an in-depth investigation of parasite virulence gene expression in malaria-naïve European volunteers undergoing CHMI with the genetically distinct Pf 7G8 clone, originating in Brazil.

Molecular and functional properties of human Plasmodium falciparum CSP C-terminus antibodies.

Human monoclonal antibodies (mAbs) against the central repeat and junction domain of Plasmodium falciparum circumsporozoite protein (PfCSP) have been studied extensively to guide malaria vaccine design compared to antibodies against the PfCSP C terminus. Here, we describe the molecular characteristics and protective potential of 73 germline and mutated human mAbs against the highly immunogenic PfCSP C-terminal domain. Two mAbs recognized linear epitopes in the C-terminal linker with sequence similarity to repeat and junction motifs, whereas all others targeted conformational epitopes in the α-thrombospondin repeat (α-TSR) domain.

First-in-human use of a modular capsid virus-like vaccine platform: an open-label, non-randomised, phase 1 clinical trial of the SARS-CoV-2 vaccine ABNCoV2.

Background: Capsid virus-like particles (cVLP) have proven safe and immunogenic and can be a versatile platform to counter pandemics. We aimed to clinically test a modular cVLP COVID-19 vaccine in individuals who were naive to SARS-CoV-2.

Methods: In this phase 1, single-centre, dose-escalation, adjuvant-selection, open-label clinical trial, we recruited participants at the Radboud University Medical Center in Nijmegen, Netherlands, and sequentially assigned them to seven groups.

Increased levels of anti-PfCSP antibodies in post-pubertal females versus males immunized with PfSPZ Vaccine does not translate into increased protective efficacy.

Background: While prior research has shown differences in the risk of malaria infection and sickness between males and females, little is known about sex differences in vaccine-induced immunity to malaria. Identifying such differences could elucidate important aspects of malaria biology and facilitate development of improved approaches to malaria vaccination.

Methods: Using a standardized enzyme-linked immunosorbent assay, IgG antibodies to the major surface protein on (Pf) sporozoites (SPZ), the Pf circumsporozoite protein (PfCSP), were measured before and two weeks after administration of a PfSPZ-based malaria vaccine (PfSPZ Vaccine) to 5-month to 61-year-olds in 11 clinical trials in Germany, the US and five countries in Africa, to determine if there were differences in vaccine elicited antibody response between males and females and if these differences were associated with differential protection against naturally transmitted Pf malaria (Africa) or controlled human malaria infection (Germany, the US and Africa).