Identification of karyopherin β as an immunogenic antigen of the malaria parasite using immune mice and human sera

A differential immunoscreening of the λgt11 Plasmodium falciparum genomic expression library was carried out using anti-P. yoelii sera (convalescent-phase mouse sera) and immune sera collected from healthy adults, to identify novel cross-reactive and possibly protective antigens of the parasite. One clone, with an insert size of 1132 bp that reacted strongly with both the sera was selected. The insert was found to be a part of the P. falciparum karyopherin β (PfKβ) homologue. RT-PCR and Northern blot analysis confirmed the expression of PfKβ in the blood stages of the parasite. The ~110 kDa protein was localized in the cytoplasm at the ring and trophozoite, and in the parasitophorous vacuole at the schizont stage. Two large fragments of PfKβ representing the N- and C-terminal halves were expressed in E. coli. The recombinant proteins were highly immunogenic in mice, and also found to be the target for immune response in natural infections of Plasmodium spp. Anti-sera against the protein showed a low level of anti-parasitic activity. Immunization with recombinant PfKβ fragments was only partially protective against a heterologous challenge infection in mice. Our results show that the parasite releases a highly immunogenic, cytoplasmic protein into the host which may not contribute to the development of protective immunity

KAF156 is an antimalarial clinical candidate with potential for use in prophylaxis, treatment, and prevention of disease transmission

Renewed global efforts toward malaria eradication have highlighted the need for novel antimalarial agents with activity against multiple stages of the parasite life cycle. We have previously reported the discovery of a novel class of antimalarial compounds in the imidazolopiperazine series that have activity in the prevention and treatment of blood stage infection in a mouse model of malaria. Consistent with the previously reported activity profile of this series, the clinical candidate KAF156 shows blood schizonticidal activity with 50% inhibitory concentrations of 6 to 17.4 nM against P. falciparum drug-sensitive and drug-resistant strains, as well as potent therapeutic activity in a mouse models of malaria with 50, 90, and 99% effective doses of 0.6, 0.9, and 1.4 mg/kg, respectively. When administered prophylactically in a sporozoite challenge mouse model, KAF156 is completely protective as a single oral dose of 10 mg/kg. Finally, KAF156 displays potent Plasmodium transmission blocking activities both in vitro and in vivo. Collectively, our data suggest that KAF156, currently under evaluation in clinical trials, has the potential to treat, prevent, and block the transmission of malaria

Human Leptospirosis Caused by a New, Antigenically Unique Leptospira Associated with a Rattus Species Reservoir in the Peruvian Amazon

As part of a prospective study of leptospirosis and biodiversity of Leptospira in the Peruvian Amazon, a new Leptospira species was isolated from humans with acute febrile illness. Field trapping identified this leptospire in peridomestic rats (Rattus norvegicus, six isolates; R. rattus, two isolates) obtained in urban, peri-urban, and rural areas of the Iquitos region. Novelty of this species was proven by serological typing, 16S ribosomal RNA gene sequencing, pulsed-field gel electrophoresis, and DNA-DNA hybridization analysis. We have named this species “Leptospira licerasiae” serovar Varillal, and have determined that it is phylogenetically related to, but genetically distinct from, other intermediate Leptospira such as L. fainei and L. inadai. The type strain is serovar Varillal strain VAR 010T, which has been deposited into internationally accessible culture collections. By microscopic agglutination test, “Leptospira licerasiae” serovar Varillal was antigenically distinct from all known serogroups of Leptospira except for low level cross-reaction with rabbit anti–L. fainei serovar Hurstbridge at a titer of 1∶100. LipL32, although not detectable by PCR, was detectable in “Leptospira licerasiae” serovar Varillal by both Southern blot hybridization and Western immunoblot, although on immunoblot, the predicted protein was significantly smaller (27 kDa) than that of L. interrogans and L. kirschneri (32 kDa). Isolation was rare from humans (2/45 Leptospira isolates from 881 febrile patients sampled), but high titers of MAT antibodies against “Leptospira licerasiae” serovar Varillal were common (30%) among patients fulfilling serological criteria for acute leptospirosis in the Iquitos region, and uncommon (7%) elsewhere in Peru. This new leptospiral species reflects Amazonian biodiversity and has evolved to become an important cause of leptospirosis in the Peruvian Amazon

Bi-allelic ACBD6 variants lead to a neurodevelopmental syndrome with progressive and complex movement disorders

The acyl-CoA-binding domain-containing protein 6 (ACBD6) is ubiquitously expressed, plays a role in the acylation of lipids and proteins, and regulates the N-myristoylation of proteins via N-myristoyltransferase enzymes (NMTs). However, its precise function in cells is still unclear, as is the consequence of ACBD6 defects on human pathophysiology. Utilizing exome sequencing and extensive international data sharing efforts, we identified 45 affected individuals from 28 unrelated families (consanguinity 93%) with bi-allelic pathogenic, predominantly loss-of-function (18/20) variants in ACBD6. We generated zebrafish and Xenopus tropicalis acbd6 knockouts by CRISPR/Cas9 and characterized the role of ACBD6 on protein N-myristoylation with YnMyr chemical proteomics in the model organisms and human cells, with the latter also being subjected further to ACBD6 peroxisomal localization studies. The affected individuals (23 males and 22 females), with ages ranging from 1 to 50 years old, typically present with a complex and progressive disease involving moderate-to-severe global developmental delay/intellectual disability (100%) with significant expressive language impairment (98%), movement disorders (97%), facial dysmorphism (95%), and mild cerebellar ataxia (85%) associated with gait impairment (94%), limb spasticity/hypertonia (76%), oculomotor (71%) and behavioural abnormalities (65%), overweight (59%), microcephaly (39%) and epilepsy (33%). The most conspicuous and common movement disorder was dystonia (94%), frequently leading to early-onset progressive postural deformities (97%), limb dystonia (55%), and cervical dystonia (31%). A jerky tremor in the upper limbs (63%), a mild head tremor (59%), parkinsonism/hypokinesia developing with advancing age (32%), and simple motor and vocal tics were among other frequent movement disorders. Midline brain malformations including corpus callosum abnormalities (70%), hypoplasia/agenesis of the anterior commissure (66%), short midbrain and small inferior cerebellar vermis (38% each), as well as hypertrophy of the clava (24%) were common neuroimaging findings. acbd6-deficient zebrafish and Xenopus models effectively recapitulated many clinical phenotypes reported in patients including movement disorders, progressive neuromotor impairment, seizures, microcephaly, craniofacial dysmorphism, and midbrain defects accompanied by developmental delay with increased mortality over time. Unlike ACBD5, ACBD6 did not show a peroxisomal localisation and ACBD6-deficiency was not associated with altered peroxisomal parameters in patient fibroblasts. Significant differences in YnMyr-labelling were observed for 68 co- and 18 post-translationally N-myristoylated proteins in patient-derived fibroblasts. N-Myristoylation was similarly affected in acbd6-deficient zebrafish and Xenopus tropicalis models, including Fus, Marcks, and Chchd-related proteins implicated in neurological diseases. The present study provides evidence that bi-allelic pathogenic variants in ACBD6 lead to a distinct neurodevelopmental syndrome accompanied by complex and progressive cognitive and movement disorders

Cloning and characterization of Plasmodium falciparum homologs of nuclear import factors, karyopherin alpha and karyopherin beta

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Identification of karyopherin β as an immunogenic antigen of the malaria parasite using immune mice and human sera

SUMMARY A differential immunoscreening of the λ gt11 Plasmodium falciparum genomic expression library was carried out using anti-P. yoelii sera (convalescent