Biology subjects

Pipini, D.

Publications and source records attributed to Pipini, D..

8 recordsLinked to original sources

bioRxiv2025

Synergistic non-neutralizing plasma antibodies to PfRH5 drive potent malaria parasite growth inhibition

An effective blood-stage vaccine is needed to protect against malaria pre-erythrocytic stage breakthrough. P. falciparum reticulocyte-binding protein homolog 5 (PfRH5) has emerged as a promising blood-stage vaccine antigen candidate, reducing parasite growth in humans during malaria challenge and showing field efficacy in children. Here, we characterize the human plasma IgG response to the RH5.1 vaccine candidate at monoclonal resolution, revealing that plasma repertoires are dominated by abundant, non-neutralizing antibodies. Using oligoclonal reconstitution experiments, in which defined pools of recombinant plasma mAbs are reassembled and functionally tested, we map how individual antibody interactions shape parasite growth inhibition activity. This approach allows us to discern which antibodies, within a polyclonal setting, act additively or synergistically, thereby revealing the emergent properties of anti-PfRH5 IgG. We further show that IgG lineages targeting linear epitopes lack neutralizing activity, while non-neutralizing IgG lineages that bind conformational epitopes can exhibit potent, interdependent synergy with each other and with neutralizing mAbs. These synergistic antibodies were identified in the plasma IgG compartments of five volunteers and highlight non-neutralizing PfRH5 epitopes that are critical for polyclonal-mediated growth inhibition. Our findings have broad implications for PfRH5 vaccine immunogen engineering and the role of non-neutralizing antibodies in infectious disease immunity.

immunology↗

bioRxiv2025

Evaluating the potential of cross-species neutralization of anti-PfCyRPA and anti-PfRIPR Monoclonal Antibodies

PfCyRPA and PfRIPR are promising next-generation malaria blood-stage vaccine candidate antigens that play an essential role in erythrocyte invasion of Plasmodium falciparum. CyRPA and RIPR orthologs are present in all human-infecting Plasmodium species, suggesting the potential for a cross-species vaccine. Using Growth Inhibition Assays (GIA), this study investigates seven anti-PfCyRPA and three anti-PfRIPR monoclonal antibodies targeting P. falciparum for their inhibitory activity against P. knowlesi, a non-falciparum species that contributes to a significant burden of zoonotic disease in South-East Asia, shares some biological features with Plasmodium vivax, and has a robust in vitro culture system. Despite their efficacy against P. falciparum and partially conserved epitopes, these antibodies exhibited minimal inhibition of P. knowlesi. Understanding the antigenic diversity and immune mechanisms across Plasmodium species is critical for advancing pan-species vaccine strategies.

immunology↗

bioRxiv2024

Copy number variants underlie the major selective sweeps in insecticide resistance genes in Anopheles arabiensis from Tanzania.

To keep ahead of the evolution of resistance to insecticides in mosquitoes, national malaria control programmes must make use of a range of insecticides, both old and new, while monitoring resistance mechanisms. Knowledge of the mechanisms of resistance remains limited in Anopheles arabiensis, which in many parts of Africa is of increasing importance because it is apparently less susceptible to many indoor control interventions. Furthermore, comparatively little is known in general about resistance to non-pyrethroid insecticides such as pirimiphos-methyl (PM), which are crucial for effective control in the context of resistance to pyrethroids. We performed a genome-wide association study to determine the molecular mechanisms of resistance to deltamethrin (commonly used in bednets) and PM, in An. arabiensis from two regions in Tanzania. Genomic regions of positive selection in these populations were largely driven by copy number variants (CNVs) in gene families involved in resistance to these two insecticides. We found evidence of a new gene cluster involved in resistance to PM, identifying a strong selective sweep tied to a CNV in the Coeae2g-Coeae6g cluster of carboxylesterase genes. Using complementary data from An. coluzzii in Ghana, we show that copy number at this locus is significantly associated with PM resistance. Similarly, for deltamethrin, resistance was strongly associated with a novel CNV allele in the Cyp6aa / Cyp6p cluster. Against this background of metabolic resistance, target site resistance was very rare or absent for both insecticides. Mutations in the pyrethroid target site Vgsc were at very low frequency in Tanzania, yet combining these samples with three An. arabiensis individuals from West Africa revealed a startling diversity of evolutionary origins of target site resistance, with up to 5 independent origins of Vgsc-995 mutations found within just 8 haplotypes. Thus, despite having been first recorded over 10 years ago, Vgsc resistance mutations in Tanzanian An. arabiensis have remained at stable low frequencies. Overall, our results provide a new copy number marker for monitoring resistance to PM in malaria mosquitoes, and reveal the complex picture of resistance patterns in An. arabiensis.

genomics↗

bioRxiv2023

Analysis of the Diverse Antigenic Landscape of the Malaria Invasion Protein RH5 Identifies a Potent Vaccine-Induced Human Public Antibody Clonotype

The highly conserved and essential Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) has emerged as the leading target for vaccines that seek to protect against the disease-causing blood-stage of malaria. However, the features of the human vaccine-induced antibody response that confer highly potent inhibition of malaria parasite invasion into red blood cells are not well defined. Here we characterize over 200 human IgG monoclonal antibodies induced by the most advanced PfRH5 vaccine. We define the antigenic landscape of this molecule, and establish epitope specificity, antibody association rate and intra-PfRH5 antibody interactions are key determinants of functional anti-parasitic potency. In addition, we identify a germline gene combination that results in an exceptionally potent class of antibody and demonstrate its prophylactic potential to protect against P. falciparum parasite challenge in vivo. This comprehensive dataset provides a framework to guide rational design of next-generation vaccines and prophylactic antibodies to protect against blood-stage malaria.

immunology↗

bioRxiv2023

Genome-wide association studies reveal novel loci associated with pyrethroid and organophosphate resistance in Anopheles gambiae s.l.

Resistance to insecticides in Anopheles mosquitoes threatens the effectiveness of the most widespread tools currently used to control malaria. The genetic underpinnings of resistance are still only partially understood, with much of the variance in resistance phenotype left unexplained. We performed a multi-country large scale genome-wide association study of resistance to two insecticides widely used in malaria control: deltamethrin and pirimiphos-methyl. Using a bioassay methodology designed to maximise the phenotypic difference between resistant and susceptible samples, we sequenced 969 phenotyped female An. gambiae and An. coluzzii from ten locations across four countries in West Africa (Benin, Cote dIvoire, Ghana and Togo), identifying single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) segregating in the populations. The patterns of resistance association were highly multiallelic and variable between populations, with different genomic regions contributing to resistance, as well as different mutations within a given region. While the strongest and most consistent association with deltamethrin resistance came from the region around Cyp6aa1, this resistance was based on a combination of several independent CNVs in An. coluzzii, and on a non-CNV bearing haplotype in An. gambiae. Further signals involved a range of cytochrome P450, mitochondrial, and immunity genes. Similarly, for pirimiphos-methyl, while the strongest signal came from the region of Ace1, more widespread signals included cytochrome P450s, glutathione S-transferases, and a subunit of the nAChR target site of neonicotinoid insecticides. The regions around Cyp9k1 and the Tep family of immune genes were associated with resistance to both insecticide classes, suggesting possible cross-resistance mechanisms. These locally-varying, multigenic and multiallelic patterns highlight the challenges involved in genomic monitoring and surveillance of resistance, and form the basis for improvement of methods used to detect and predict resistance. Based on simulations of resistance variants, we recommend that yet larger scale studies, exceeding 500 phenotyped samples per population, are required to better identify associated genomic regions.

genomics↗

bioRxiv2021

Identification of a rapidly-spreading triple mutant for high-level metabolic insecticide resistance in Anopheles gambiae provides a real-time molecular diagnostic for anti-malarial intervention deployment.

Insecticide resistance provides both an increasingly pressing threat to the control of vector-borne diseases and insights into the remarkable capacity of natural populations to show rapid evolutionary responses to contemporary selection. Malaria control remains heavily dependent on deployment of pyrethroid insecticides, primarily in long lasting insecticidal nets (LLINs), but resistance in the major malaria vectors has increased over the last 15 years in concert with dramatic expansion of LLIN distributions. Identifying genetic mechanisms underlying high-level resistance in mosquitoes, which may almost entirely overcome pyrethroid efficacy, is crucial for the development and deployment of potentially resistance-breaking tools. Using the Anopheles gambiae 1000 genomes (Ag1000g) data we identified a very recent selective sweep in mosquitoes from Uganda which localized to a cluster of cytochrome P450 genes, including some commonly implicated in resistance. Further interrogation revealed a haplotype involving a trio of mutations, a nonsynonymous point mutation in Cyp6p4 (I236M), an upstream insertion of a partial Zanzibar-like transposable element (TE) and a duplication of the Cyp6aa1 gene. The mutations appear to have originated recently in An. gambiae from the Kenya-Uganda border region around Lake Victoria, with stepwise replacement of the double-mutant (Zanzibar-like TE and Cyp6p4-236M) with the triple-mutant haplotype (including Cyp6aa1 duplication), which has spread into the Democratic Republic of Congo and Tanzania. The triple-mutant haplotype is strongly associated with increased expression of genes able to metabolise pyrethroids and is strongly predictive of resistance to pyrethroids most notably deltamethrin, a commonly-used LLIN insecticide. Importantly, there was increased mortality in mosquitoes carrying the triple-mutation when exposed to nets co-treated with the synergist piperonyl butoxide (PBO). Frequencies of the triple-mutant haplotype remain spatially variable within countries, suggesting an effective marker system to guide deployment decisions for limited supplies of PBO-pyrethroid co-treated LLINs across African countries. Duplications of the Cyp6aa1 gene are common in An. gambiae across Africa and, given the enzymes metabolic activity, are likely to be a useful diagnostic for high levels of pyrethroid resistance.

evolutionary biology↗

bioRxiv2020

Resistance to pirimiphos-methyl in West African Anopheles is spreading via duplication and introgression of the Ace1 locus

Vector population control using insecticides is a key element of current strategies to prevent malaria transmission in Africa. The introduction of effective insecticides, such as the organophosphate pirimiphos-methyl, is essential to overcome the recurrent emergence of resistance driven by the highly diverse Anopheles genomes. Here, we use a population genomic approach to investigate the basis of pirimiphos-methyl resistance in the major malaria vectors Anopheles gambiae and A. coluzzii. A combination of copy number variation and a single non-synonymous substitution in the acetylcholinesterase gene, Ace1, provides the key resistance diagnostic in an A. coluzzii population from Cote dIvoire that we used for sequence-based association mapping, with replication in other West African populations. The Ace1 and substitution and duplications occur on a unique resistance haplotype that evolved in A. gambiae and introgressed into A. coluzzii, and is now common in West Africa probably due to cross-resistance with previously used insecticides. Our findings highlight the phenotypic value of this complex resistance haplotype and clarify its evolutionary history, providing tools to understand the current and future effectiveness of pirimiphos-methyl based interventions.

genomics↗

bioRxiv2018

Rapid high throughput SYBR green assay for identifying the malaria vectors Anopheles arabiensis, Anopheles coluzzii and Anopheles gambiae s.s. Giles

The Anopheles gambiae sensu lato species complex consists of a number of cryptic species with different habitats and behaviours. These morphologically indistinct species are identified by chromosome banding and molecular diagnostic techniques which are still under improvement even though the current SINE method for identification between An. coluzzii and An. gambiae works reliably. This study describes a refinement of the SINE method to increase sensitivity and high throughput method for the identification of both species and An. arabiensis using amplicon dissociation characteristics.\n\nField collected samples, laboratory reared colonies and crossed specimens of the two species were used for the design of the protocol. An. gambiae, An. coluzzii, and hybrids of the two species were provided by the insectary of Vestergaard-NMIMR Vector Labs at the Noguchi Memorial Institute for Medical Research (Ghana) and An. arabiensis from Kenya. Samples were first characterised using conventional SINE PCR method, and further assayed using SYBR green, an intercalating fluorescent dye.\n\nThe three species and hybrids were clearly differentiated using the melting temperature of the dissociation curves, with derivative peaks at 72 Celsius for An. arabiensis, 75{degrees}C for An. gambiae and 86{degrees}C for An. coluzzii. The hybrids (An. gambiae / An. coluzzii) showed both peaks. This work is the first to describe a SYBR green real time PCR method for the characterization of An. arabiensis, An. gambiae and An. coluzzii and was purposely designed for basic melt-curve analysis (rather than high-resolution melt-curve) to allow it to be used on a wide range of real-time PCR machines.

molecular biology↗