Disruption of Parasitehmgb2Gene Attenuates Plasmodium berghei ANKA Pathogenicity

Abstract

h Eukaryotic high-mobility-group-box (HMGB) proteins are nuclear factors involved in chromatin remodeling and transcription regulation. When released into the extracellular milieu, HMGB1 acts as a proinflammatory cytokine that plays a central role in the pathogenesis of several immune-mediated inflammatory diseases. We found that the Plasmodium genome encodes two genuine HMGB factors, Plasmodium HMGB1 and HMGB2, that encompass, like their human counterparts, a proinflammatory domain. Given that these proteins are released from parasitized red blood cells, we then hypothesized that Plasmodium HMGB might contribute to the pathogenesis of experimental cerebral malaria (ECM), a lethal neuroinflammatory syndrome that develops in C57BL/6 (susceptible) mice infected with Plasmodium berghei ANKA and that in many aspects resembles human cerebral malaria elicited by P. falciparum infection. The pathogenesis of experimental cerebral malaria was suppressed in C57BL/6 mice infected with P. berghei ANKA lacking the hmgb2 gene (⌬hmgb2 ANKA), an effect associated with a reduction of histological brain lesions and with lower expression levels of several proinflammatory genes. The incidence of ECM in pbhmgb2-deficient mice was restored by the administration of recombinant PbHMGB2. Protection from experimental cerebral malaria in ⌬hmgb2 ANKA-infected mice was associated with reduced sequestration in the brain of CD4؉ and CD8 ؉ T cells, including CD8 ؉ granzyme B ؉ and CD8 ؉ IFN-␥ ؉ cells, and, to some extent, neutrophils. This was consistent with a reduced parasite sequestration in the brain, lungs, and spleen, though to a lesser extent than in wild-type P. berghei ANKA-infected mice. In summary, Plasmodium HMGB2 acts as an alarmin that contributes to the pathogenesis of cerebral malaria.

DNA aptamers for the recognition of HMGB1 from Plasmodium falciparum

“…exploit the natural regulatory network of the human HMGB1 by exporting HMGB1 Pf , although, to our knowledge, experimental evidence is still lacking. Deletion of the HMGB2 homolog from Plasmodium resulted in attenuated pathogenicity in mouse models [51], indicating an involvement on severe inflammatory responses. Altogether, HMGB1 and HMGB2 appear to be involved in the inflammatory response of the host, making the HMGB family a candidate for directed inhibitory drugs.…”

A genetically hmgb2 attenuated blood stage P. berghei induces crossed-long live protection

“…Two highly pathogen parasites were used: P. berghei ANKA (PbANKA MRA-867) that kills C57Bl/6 within 7-10 days of experimental cerebral malaria (ECM) and P. berghei NK65 (PbNK65 MRA-268) that kills C57Bl/6 within 25-30 days of hyperparasitaemia and anaemia. The disruption of the hmgb2 gene in PbNK65 background was performed with 5' and 3' gene targeting KO vector designed and produced as detailed for PbANKA [18]. Wild type PbNK65 blood stages parasites were transfected using standard transfection methods [21].…”

“…In all experiments, RBCs infected with P. berghei NK65 or its knockout counterpart Δhmgb2 PbNK65 were used to infect 5 to 10-week-old C57BL/6 mice as previously reported [18].…”

“…We reported that two Plasmodium HMGB behave as chromatin remodelling proteins [17] and as a late pro-inflammatory factor leading to experimental cerebral malaria (ECM) onset in a murine model. Actually, in contrast to WT PbANKA parasite that triggers mouse death within 7-8 days, mice infected with hmgb2-deleted parasite (Δhmgb2 PbANKA) showed an increased survival concomitantly (60%) with a decrease of parasite sequestration and haemorrhagic foci in the brain [18,19]. In addition, the antibodies raised against the HMGB protein triggered protection pathogenic parasite infection [20].…”

Histamine releasing factor and elongation factor 1 alpha secreted via malaria parasites extracellular vesicles promote immune evasion by inhibiting specific T cell responses

“…Error bars, SEM. Data are representative of three independent experiments with five mice per group; * P < 0.0095, **0.0167 < P < 0.0242, ***0.0317 < P < 0.0424, Mann-Whitney test gene, we prepared EVs from various Plasmodium parasites including two mutants for PbANKA EF-1α genes (Janse et al, 2003;line 115, eEF-1abΔ and line 118, eEF-1aa) that indeed showed no protein products as assessed by western blotting ( Figure S2b) and a PbANKA mutant where the gene encoding for the high mobility group 2 (HMGB2) protein was deleted (PbANKA hmgb2Δ), and the disruption of this gene was found previously to attenuate PbANKA pathogenicity (Briquet et al, 2015). As shown in Figure S4A, similar to hrfΔ parasites, EVs from the two lines, line 115 eEF-1ab and line 118 ΔeEF-1aa, were no longer able to inhibit the DTH response.…”