Primaquine is used to eradicate the hepatic or hypnozoite form of Plasmodium vivax that may lead to relapse of infection. Host genetic factors may play a role in the activity of primaquine therapy.

Plasmodium vivax (Pv) forms non-replicating liver stages called hypnozoites, which activate after primary infection, and cause relapses of symptomatic blood-stage malaria. We hypothesize that hypnozoites must actively suppress schizogony to maintain a quiescent state. Differential transcriptome prospecting identifies two hypnozoite-expressed transcripts encoding putative RNA-binding proteins. We assess the functional role of the two encoded proteins in Plasmodium yoelii (Py), a rodent malaria parasite that naturally does not form hypnozoites. Strikingly, individual expression of each protein in Py liver stages blocks liver stage schizogony, with parasites remaining small and uninucleate. A screen of RNA sequences that interact with the putative RNA-binding domains of these proteins shows enrichment of distinct, highly specific motifs, indicating that they might block schizogony by binding RNAs containing these motifs. Our findings provide the unprecedented functional evidence for one p

Plasmodium vivax parasites can lie dormant in the liver as hypnozoites, activating weeks to months after sporozoite inoculation to cause relapsing ...

INTRODUCTION: Plasmodium cynomolgi is one of the few malaria parasite species that forms dormant liver stages known as hypnozoites and is therefore a suitable model for Plasmodium vivax, the causative agent of recurrent malaria. Very little is known about the biology and pharmacology of liver stage dormancy, which hampers the search for compounds with anti-hypnozoite activity.

Malaria scientists identify two candidate proteins that could maintain the P. vivax malaria parasite in a dormant hypnozoite form in the liver. These findings enhance our knowledge of malaria parasite persistence in the liver, an underexplored area important for developing new treatments.

BACKGROUND: Plasmodium vivax presents a significant obstacle to malaria elimination due to its capacity to form dormant liver-stage hypnozoites that can cause relapses. Universal radical cure, which administers hypnozoite-targeting treatment to patients with P. falciparum malaria living in co-endemic areas, has potential to reduce P. vivax relapses. However, its implementation is hindered by the lack of a diagnostic tool for detecting hypnozoite-carriage.

CONCLUSION: A large majority of white Moors are Duffy-positive and susceptible to P. vivax infection, but most are eligible for anti-hypnozoite therapy with primaquine at the standard dose. About 15.4% of individuals with black African ancestry were affected by G6PD A- deficiency, independently of their Duffy receptor status. This population requires G6PD screening before primaquine therapy in rare cases of P. vivax infection. These results provide important clues about the feasibility to...

by Erica M. Pasini, Hassan Hakimi, Nattawat Chaiyawong, Onny Klop, Anne-Marie Zeeman, Ivonne Nieuwenhuis, Nicole van der Werff, Kumiko Kihara, Kenjiro Kami, Clemens H. M. Kocken, Osamu Kaneko #Plasmodium vivax malaria control and elimination is complicated by the presence of dormant liver stages, known as hypnozoites, that can reactivate weeks, months or years after infection giving rise to clinical and transmissible vivax malaria, without exposure to new infectious mosquito bites. Hypnozoite infection remains without symptoms and there are no diagnostic tools available to identify hypnozoite carriers. Such diagnostic tools are invaluable for precise mapping of the scale of the infection problem and for identifying individuals that would qualify for targeted drug treatment, to wipe out this hidden reservoir of malaria parasites. Targeted treatment would have considerable benefits as it would prevent the exposure of individuals without hypnozoites to the considerable side-effects of drugs such as Primaquine, which has a relatively high toxicity to people deficient in glucose-6-phosphate dehydrogenase. Here we present a Proof-of-Concept study aimed at identifying diagnostic markers for malaria hypnozoite infection, by combining in vitro #Plasmodium cynomolgi hypnozoite cultures (an accessible proxy to P. vivax with nearly identical biology) with sensitive metabolomics. Specific hypnozoite-related metabolites have been identified in the supernatant of hypnozoite-enriched in vitro liver stage cultures. This suggests that, following in vivo validation of such metabolites in the P. cynomolgi/rhesus monkey model and subsequent in P. vivax-infected individuals, a rapid diagnostic test for hypnozoite infection may be developed.

by Erica M. Pasini, Hassan Hakimi, Nattawat Chaiyawong, Onny Klop, Anne-Marie Zeeman, Ivonne Nieuwenhuis, Nicole van der Werff, Kumiko Kihara, Kenjiro Kami, Clemens H. M. Kocken, Osamu Kaneko #Plasmodium vivax malaria control and elimination is complicated by the presence of dormant liver stages, known as hypnozoites, that can reactivate weeks, months or years after infection giving rise to clinical and transmissible vivax malaria, without exposure to new infectious mosquito bites. Hypnozoite infection remains without symptoms and there are no diagnostic tools available to identify hypnozoite carriers. Such diagnostic tools are invaluable for precise mapping of the scale of the infection problem and for identifying individuals that would qualify for targeted drug treatment, to wipe out this hidden reservoir of malaria parasites. Targeted treatment would have considerable benefits as it would prevent the exposure of individuals without hypnozoites to the considerable side-effects of drugs such as Primaquine, which has a relatively high toxicity to people deficient in glucose-6-phosphate dehydrogenase. Here we present a Proof-of-Concept study aimed at identifying diagnostic markers for malaria hypnozoite infection, by combining in vitro #Plasmodium cynomolgi hypnozoite cultures (an accessible proxy to P. vivax with nearly identical biology) with sensitive metabolomics. Specific hypnozoite-related metabolites have been identified in the supernatant of hypnozoite-enriched in vitro liver stage cultures. This suggests that, following in vivo validation of such metabolites in the P. cynomolgi/rhesus monkey model and subsequent in P. vivax-infected individuals, a rapid diagnostic test for hypnozoite infection may be developed.

Radical cure of Plasmodium vivax malaria must include elimination of quiescent 'hypnozoite' forms in the liver; however, the only FDA-approved treatments are contraindicated in many vulnerable populations. To identify new drugs and drug targets for hypnozoites, we screened the Repurposing, Focused Rescue, and Accelerated Medchem (ReFRAME) library and a collection of epigenetic inhibitors against P. vivax liver stages. From both libraries, we identified inhibitors targeting epigenetics pathways...

Background: Plasmodium vivax poses a major obstacle to malaria elimination because it can lie dormant in the liver for weeks or months before reactivating and causing a relapse of infection. These dormant forms (hypnozoites) cannot be detected using standard diagnostics, but recent P. vivax exposure and by proxy, hypnozoite carriage, can be inferred using antibody-based tests (serological markers). In this study, we examined how genetic variation in P. vivax affects the utility of these antibody markers, and whether redesigned antigens could improve performance. Methods: We analysed global P. vivax genetic data to assess variation in leading serological markers. Based on this, we produced new antigen versions (haplotypes) that better reflect global sequence diversity, compared to the commonly used reference strain (Sal-1). Antibody responses against these new constructs were then tested using samples from well-characterised cohorts in Brazil and Thailand. Antibody levels were assessed in relation to how recently participants had a qPCR-detectable blood-stage P. vivax infection. We compared the ability of the haplotypes and reference constructs to correctly identify individuals infected within the prior 9-months. Findings: Extensive genetic diversity was identified in two P. vivax antigens, DBPII and MSP5. Several antigens had large numbers of circulating haplotypes globally, with the percentage with similar sequence identity to the reference Sal-1 ranging from 0.4% (MSP5) to 99% (S16). Two antigens exhibited strong differences in immunogenicity by region and construct (RBP2a and DBPII). However, for most proteins (5 out of 8), these differences had little impact on the accuracy of identifying recent exposure. In cases where performance was affected (e.g. RBP2a), this could be overcome by adding multiple antigens into the classification model. Interpretation: Even highly diverse antigens can be effective serological exposure markers. Our findings highlight the importance of testing the impact of genetic diversity when designing serological tests and suggest practical strategies, such as using a mix of antigens, to ensure consistent performance across regions.

Background: Plasmodium vivax poses a major obstacle to malaria elimination because it can lie dormant in the liver for weeks or months before reactivating and causing a relapse of infection. These dormant forms (hypnozoites) cannot be detected using standard diagnostics, but recent P. vivax exposure and by proxy, hypnozoite carriage, can be inferred using antibody-based tests (serological markers). In this study, we examined how genetic variation in P. vivax affects the utility of these antibody markers, and whether redesigned antigens could improve performance. Methods: We analysed global P. vivax genetic data to assess variation in leading serological markers. Based on this, we produced new antigen versions (haplotypes) that better reflect global sequence diversity, compared to the commonly used reference strain (Sal-1). Antibody responses against these new constructs were then tested using samples from well-characterised cohorts in Brazil and Thailand. Antibody levels were assessed in relation to how recently participants had a qPCR-detectable blood-stage P. vivax infection. We compared the ability of the haplotypes and reference constructs to correctly identify individuals infected within the prior 9-months. Findings: Extensive genetic diversity was identified in two P. vivax antigens, DBPII and MSP5. Several antigens had large numbers of circulating haplotypes globally, with the percentage with similar sequence identity to the reference Sal-1 ranging from 0.4% (MSP5) to 99% (S16). Two antigens exhibited strong differences in immunogenicity by region and construct (RBP2a and DBPII). However, for most proteins (5 out of 8), these differences had little impact on the accuracy of identifying recent exposure. In cases where performance was affected (e.g. RBP2a), this could be overcome by adding multiple antigens into the classification model. Interpretation: Even highly diverse antigens can be effective serological exposure markers. Our findings highlight the importance of testing the impact of genetic diversity when designing serological tests and suggest practical strategies, such as using a mix of antigens, to ensure consistent performance across regions.

Read new paper, Modeling the within-host dynamics of Plasmodium vivax hypnozoite activation: An analysis of the SPf66 vaccine trial, which used data from the most detailed cohort study ever conducted…

Dormancy enables relapsing malaria parasites, such as Plasmodium vivax and cynomolgi, to survive unfavorable conditions. It is enabled by hypnozoites, parasites remaining quiescent inside hepatocytes before reactivating and establishing blood-stage infection. We integrate omics approaches to explore

The Plasmodium vivax lifecycle encompasses a dormant liver-stage known as 'hypnozoite' which serves as silent reservoirs of malaria, reactivation of which results in recurring episodes of relapse with varying periodicity. This contributes to continuous transmission of malaria unamenable to control m

In a groundbreaking study set to redefine our understanding of malaria pathology, researchers have identified two RNA-binding proteins expressed specifically during the hypnozoite stage of Plasmodium

Nature Communications, Published online: 30 May 2026; doi:10.1038/s41467-026-73666-0Malaria scientists identify two candidate proteins that could maintain the P. vivax malaria parasite in a dormant hypnozoite form in the liver. These findings enhance our knowledge of malaria parasite persistence in the liver, an underexplored area important for developing new treatments.

Nature Communications, Published online: 30 May 2026; doi:10.1038/s41467-026-73666-0Malaria scientists identify two candidate proteins that could maintain the P. vivax malaria parasite in a dormant hypnozoite form in the liver. These findings enhance our knowledge of malaria parasite persistence in the liver, an underexplored area important for developing new treatments.