A Plasmodium Parasite with Complete Late Liver Stage Arrest Protects against Preerythrocytic and Erythrocytic Stage Infection in Mice

Abstract

Genetically attenuated malaria parasites (GAP) that arrest during liver stage development are powerful immunogens and afford complete and durable protection against sporozoite infection. Late liver stage-arresting GAP provide superior protection against sporozoite challenge in mice compared to early live stage-arresting attenuated parasites. However, very few late liver stage-arresting GAP have been generated to date. Therefore, identification of additional loci that are critical for late liver stage development and can be used to generate novel late liver stage-arresting GAPs is of importance. We further explored genetic attenuation in by combining two gene deletions, and (), that each cause late liver stage arrest with various degrees of infrequent breakthrough to blood stage infection. The dual gene deletion resulted in a synthetic lethal phenotype that caused complete attenuation in a highly susceptible mouse strain. arrested late in liver stage development and did not persist in livers beyond 3 days after infection. Immunization with this GAP elicited robust protective antibody responses in outbred and inbred mice against sporozoites, liver stages, and blood stages as well as eliciting protective liver-resident T cells. The immunization afforded protection against both sporozoite challenge and blood stage challenge. These findings provide evidence that completely attenuated late liver stage-arresting GAP are achievable via the synthetic lethal approach and might enable a path forward for the creation of a completely attenuated late liver stage-arresting GAP.

Designer Parasites: Genetically Engineered Plasmodium as Vaccines To Prevent Malaria Infection

“…Based on late liver-stage transcriptome data, additional genes have been explored to generate new LARC GAPs (56)(57)(58)(59). We have recently generated a novel LARC GAP, the P. yoelii lisp2 2 /mei2 2 LARC that completely arrests late in liver development and elicits durable sterile protection in immunized mice (60). However, to date, no LARC has been generated in P. falciparum.…”

Strains used in whole organism Plasmodium falciparum vaccine trials differ in genome structure, sequence, and immunogenic potential

“…To compare subpopulations identified in our Southeast Asia/Oceania admixture analysis with previously described ancestral, resistant, and admixed subpopulations from Cambodia [64], the above non-synonymous SNP set was used before pruning for LD (n = 11,943) and was compared to a non-synonymous SNP dataset (n = 21,257) from 167 samples used by Dwivedi et al [65] to describe eight Cambodian subpopulations, in an analysis that included a subset of samples used by Miotto et al [64] (who first characterized the population structure in Cambodia). There were 5881 shared non-synonymous SNPs between the two datasets, 1649 of which were observed in NF135.C10.…”

“…To determine the likely position of each non-reference contig on the 3D7 reference genome, MUMmer's show-tiling program was used with relaxed settings (-g 100000 -v 50 -i 50) to align contigs to 3D7 chromosomes (top). 3D7 nuclear chromosomes [1][2][3][4][5][6][7][8][9][10][11][12][13][14] are shown in gray, arranged from smallest to largest, along with organelle genomes (M = mitochondrion, A = apicoplast). Contigs from each PfSPZ assembly (NF54: black, 7G8: green, NF166.C8: orange, NF135.C10: hot pink) are shown aligned to their best 3D7 match.…”

“…Of these vaccine candidates, Sanaria® PfSPZ vaccine, based on radiationattenuated sporozoites, has progressed furthest in clinical trial testing [3][4][5][6][7][8][9]. Other whole-organism vaccine candidates, including chemoattenuated (Sanaria® PfSPZ-CVac), transgenic, and genetically attenuated sporozoites, are in earlier stages of development [10][11][12].…”

The transportome of the malaria parasite

“…Gene‐knockout lines that arrest during the late maturation of the liver‐stage parasite are possible candidates for a malaria vaccine as they can elicit a potent neutralising immune response in animal malaria models without establishing a blood‐stage infection (Vaughan & Kappe, ; Goswami, Minkah & Kappe, ). There is, therefore, much interest in generating genetically‐attenuated P. falciparum lines that arrest in the late liver stage (Vaughan et al ., ) and a transporter gene which produced this phenotype when disrupted is the multidrug‐resistance‐associated protein 2 ( mrp2 ; Table S2). P. falciparum and P. berghei parasites lacking mrp2 infect hepatocytes and grow and replicate normally for 30–40 h, after which development becomes abnormal and the infected cells fail to produce mature merozoites (Rijpma et al ., ).…”