NAD(P)H-dependent production of oxygen reactive species by the salivary glands of the mosquito Anopheles albimanus

Disruption of the Plasmodium berghei 2-Cys peroxiredoxin TPx-1 gene hinders the sporozoite development in the vector mosquito

To investigate the physiologic role of cytosolic 2-Cys peroxiredoxin of Plasmodium berghei (PbTPx-1), we infected the vector mosquito Anopheles stephensi with a parasite carrying a targeted knockout of pbtpx-1 (Prx-KO). The number of Prx-KO midgut oocysts at 14-15 days post-feeding (pf) was comparable to that of the parent strain (WT); however, the numbers of sporozoites that formed in midgut oocysts and accumulated in the salivary gland of Prx-KO-infected mosquitoes by 21 days pf were decreased to 10-20% and 3-10%, respectively, of those values in WT-infected mosquitoes. A higher frequency of DNA strand breaks was detected in Prx-KO oocysts than in WT oocysts. Sporozoites carrying the targeted disruption had reduced infectivity in mice; however, the knockout did not affect the ability of the sporozoite to reach the liver parenchyma and initiate exo-erythrocytic form (EEF) development. TPx-1 may be involved in development during exponentially multiplying stages, such as sporozoites and EEF.

Antihemostatic Molecules from Saliva of Blood-Feeding Arthropods

The ability to feed on vertebrate blood has evolved many times in various arthropod clades. Each time this trait evolves, novel solutions to the problem posed by vertebrate hemostasis are generated. Consequently, saliva of blood-feeding arthropods has proven to be a rich source of antihemostatic molecules. Vasodilators include nitrophorins (nitric oxide storage and transport heme proteins), a variety of peptides that mimic endogenous vasodilatory neuropeptides, and proteins that catabolize or sequester endogenous vasoconstrictors. A variety of platelet aggregation inhibitors antagonize platelet responses to wound-generated signals, including ADP, thrombin, and collagen. Anticoagulants disrupt elements of both the intrinsic and extrinsic pathways. Molecular approaches (termed 'sialomics') to characterize the full inventory of mRNAs transcribed in salivary glands have revealed a surprising level of complexity within a single species. Multiple salivary proteins may be directed against each component of hemostasis, resulting in both redundancy and in some cases cooperative interactions between antihemostatic proteins, as in the case of the Rhodnius prolixus apyrase (which hydrolyzes ADP) and Rhodnius platelet aggregation inhibitor 1 (which sequesters ADP). The complexity and redundancy of saliva ensures an efficient blood meal for the arthropod, but it also provides a diverse array of novel antihemostatic molecules for the pharmacologist.

The enzymatic component of Drosophila melanogaster chorion is the Pxd peroxidase

In the present study, we demonstrate the isolation and characterization of the Pxd cDNA clone, which codes for the Drosophila melanogaster chorion peroxidase. This specific peroxidase is involved in the chorion hardening process, through protein crosslinking mediated by the formation of di- and tri-tyrosine bonds. The Pxd gene product has been identified in crude protein extracts from adult flies as three immunoreacting, with the anti-rAePO polyclonal antibody, bands of 77, 67 and 55 kDa, while in larvae and purified chorions as a unique 55 kDa band. Moreover, the mature form of the Pxd recombinant protein was specifically recognized by the anti-rAePO antibody as a 77 kDa band, while in the presence of H2O2 was able to convert tyrosine residues to di-tyrosine moieties. Northern blotting analysis of total RNA preparations revealed distinct molecular weight patterns of the Pxd RNA transcripts among adult flies, ovaries and larvae. The in situ hybridization clearly shows that the Pxd mRNA is specifically expressed in follicle cells during the late stages of oogenesis 11-14, while the reverse transcription reactions dictate the stage-specific developmental regulation of the Pxd gene. The immunolocalization approach, using the anti-rAePO polyclonal antibody, has revealed that the Pxd peroxidase is selectively localized in the chorion structures and particularly in the endochorion and innermost chorionic layer (ICL).

Infectivity of Plasmodium berghei sporozoites delivered by intravenous inoculation versus mosquito bite: implications for sporozoite vaccine trials

Plasmodium berghei sporozoites delivered by mosquito bite were more infectious to outbred CD-1 mice than were sporozoites delivered by intravenous inoculation. The route of challenge also affected vaccine efficacy. In view of these findings and the fact that mosquito bites are the natural mode of sporozoite delivery, infectious mosquito bites should be considered the challenge protocol of choice for sporozoite vaccine efficacy trials.