Truncation of Plasmodium berghei merozoite surface protein 8 does not affect in vivo blood-stage development

Abstract

Merozoite surface protein 8 (MSP8) has shown promise as a vaccine candidate in the Plasmodium yoelii rodent malaria model and has a proposed role in merozoite invasion of erythrocytes. However, the temporal expression and localisation of MSP8 are unusual for a merozoite antigen. Moreover, in Plasmodium falciparum the MSP8 gene could be disrupted with no apparent effect on invitro growth. To address the invivo function of full-length MSP8, we truncated MSP8 in the rodent parasite Plasmodium berghei. PbDeltaMSP8 disruptant parasites displayed a normal blood-stage growth rate but no increase in reticulocyte preference, a phenomenon observed in P. yoelii MSP8 vaccinated mice. Expression levels of erythrocyte surface antigens were similar in P. berghei wild-type and PbDeltaMSP8-infected erythrocytes, suggesting that a parasitophorous vacuole function for MSP8 does not involve global trafficking of such antigens. These data demonstrate that a full-length membrane-associated form of PbMSP8 is not essential for blood-stage growth.

An in silico down-scaling approach uncovers novel constituents of the Plasmodium-containing vacuole

“…PV4 (PBANKA_1349200) harbours in its carboxy-terminal portion the key signatures of a merozoite surface protein 7-like protein. Its localisation throughout blood infection, however, suggests functions predominantly in the PV, as previously shown for another proposed merozoite surface protein, MSP8 36 , 37 . Interestingly, inactivation of MSP8 had no effect on blood stage growth or protein export of P. berghei either 37 .…”

“…Its localisation throughout blood infection, however, suggests functions predominantly in the PV, as previously shown for another proposed merozoite surface protein, MSP8 36 , 37 . Interestingly, inactivation of MSP8 had no effect on blood stage growth or protein export of P. berghei either 37 . Surprisingly, we observed a significant portion of PV4 in the erythrocyte cytoplasm during the ring and young trophozoite stages, despite the lack of any discernable targeting information.…”

Evidence of purifying selection on merozoite surface protein 8 (MSP8) and 10 (MSP10) in Plasmodium spp.

“…In contrast to other MSP proteins (including MSP10), Pf MSP8 is expressed predominantly during the first half of the P. falciparum erythrocytic cycle (8 to 16 h after invasion), and only the smaller C-terminal Pf MSP8 is maintained until schizogony and appears to localize to the food vacuole. The absence of the Pf MSP8 protein on the surface of invading merozoites suggests that Pf MSP8 may not play a role in the parasite-red blood cell interactions during invasion in the case of P. falciparum (Black et al, 2005, Drew et al, 2005, Koning-Ward et al, 2008). Importantly, as both the MSP1 and MSP8 EGF-like domains are present in the ring stages, it is still possible that at this time they perform the same (or related) role in the establishment and functioning of the parasitophorous vacuole (Black et al, 2005, Drew et al, 2005, Koning-Ward et al, 2008).…”

Disruption of plasmepsin-4 and merozoites surface protein-7 genes in Plasmodium berghei induces combined virulence-attenuated phenotype

“…The infection caused by Plasmodium berghei in rodents partially mimics human malaria and is regarded as a valuable in vivo model to study parasite induced pathology and the development of protective immunity. In P. berghei , similarly to what has been observed for P. falciparum, disruption of important blood-stage transcribed genes is very difficult to accomplish22232425. Only a small number of blood-stage genes, including msp7 and pm4 , have been disrupted in both P. berghei and P. falciparum allowing the analysis of how impairment of in vitro growth translates into a virulence change of rodent malaria in vivo 23262728.…”