An ongoing public health challenge is to develop vaccines that are effective against infectious diseases that have global relevance. Vaccines against serotypes of group B Streptococcus (GBS) that are prevalent in the United States and Europe are not optimally efficacious against serotypes common to other parts of the world. New technologies and innovative approaches are being used to identify GBS antigens that overcome serotype-specificity and that could form the basis of a globally effective vaccine against this opportunistic pathogen. This Review highlights efforts towards this goal and describes a template that can be followed to develop vaccines against other bacterial pathogens.

Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.

Plasmodium falciparum-derived cysteine protease falcipain-2 cleaves host erythrocyte hemoglobin at acidic pH and specific components of the membrane skeleton at neutral pH. Analysis of stage-specific expression of these 2 proteolytic activities of falcipain-2 shows that hemoglobinhydrolyzing activity is maximum in early trophozoites and declines rapidly at late stages, whereas the membrane skeletal protein hydrolyzing activity is markedly increased at the late trophozoite and schizont stages. Among the erythrocyte membrane skeletal proteins, ankyrin and protein 4.1 are cleaved by native and recombinant falcipain-2 near their C-termini. To identify the precise peptide sequence at the hydrolysis site of protein 4.1, we used a recombinant construct of protein 4.1 as substrate followed by MALDI-MS analysis of the cleaved product. We show that falcipain-2-mediated cleavage of protein 4.1 occurs immediately after lysine 437, which lies within a region of the spectrinactin-binding domain critical for erythrocyte membrane stability. A 16-mer peptide containing the cleavage site completely inhibited the enzyme activity and blocked falcipain-2-induced fragmentation of erythrocyte ghosts. Based on these results, we propose that falcipain-2 cleaves hemoglobin in the acidic food vacuole at the early trophozoite stage, whereas it cleaves specific components of the red cell skeleton at the late trophozoite and schizont stages. It is the proteolysis of skeletal proteins that causes membrane instability, which, in turn, facilitates parasite release in vivo. IntroductionPlasmodium falciparum causes the most severe form of human malaria and is becoming increasingly resistant to available antimalarial drugs. New chemotherapy-based approaches to fight the disease are therefore urgently needed. Parasite proteases that are involved in P falciparum development appear to be good targets. Mounting evidence suggests that cysteine proteases are involved in host cell rupture and release of merozoites. In the presence of such inhibitors, merozoites mature normally but are unable to escape from host erythrocytes. [1][2][3][4] The cluster of merozoites inside a red blood cell (RBC) is enclosed within 2 membranes: an inner parasitophorous vacuole membrane (PVM) and an outer RBC membrane. The rupture of these 2 membranes apparently releases the merozoites for another round of RBC invasion. In a recent study by Salmon et al,5 the authors propose a 2-step process for parasite release from the host erythrocyte: an initial exit of merozoites enclosed within the PVM followed by a rapid escape from the PVM by a proteolysisdependent mechanism. This study suggests that the RBC membrane is lost independently of the PVM. In another report, Winograd et al 6 used videomicroscopy to study the release of merozoites and concluded that an aperture is made through the PVM and RBC membranes to allow merozoites to exit in an orderly fashion. Merozoites were released together with the residual body containing hemozoin, leaving behind the red cell membrane and some...

Falcipain-2 (FP-2) is a dual-function protease that cleaves hemoglobin at the early trophozoite stage and erythrocyte membrane ankyrin and protein 4.1 at the late stages of parasite development. FP-2-mediated cleavage of ankyrin and protein 4.1 is postulated to cause membrane instability facilitating parasite release in vivo. To test this hypothesis, here we have determined the precise peptide sequence at the hydrolysis site of ankyrin to develop specific inhibitor(s) of FP-2. Mass spectrometric analysis of the hydrolysis products showed that FP-2-mediated cleavage of ankyrin occurred immediately after arginine 1,210. A 10-mer peptide (ankyrin peptide, AnkP) containing the cleavage site completely inhibited the FP-2 enzyme activity in vitro and abolished all of the known functions of FP-2. To determine the effect of this peptide on the growth and development of P. falciparum, the peptide was delivered into intact parasite-infected red blood cells (RBCs) via the Antennapedia homeoprotein internalization domain. Growth and maturation of trophozoites and schizonts was markedly inhibited in the presence of the fused AnkP peptide. <10% of new ring-stage parasites were detected compared with the control sample. Together, our results identify a specific peptide derived from the spectrin-binding domain of ankyrin that blocks late-stage malaria parasite development in RBCs. Confocal microscopy with FP-2-specific antibodies demonstrated the proximity of the enzyme in apposition with the RBC membrane, further corroborating the proposed function of FP-2 in the cleavage of RBC skeletal proteins.Plasmodium falciparum causes the most severe form of human malaria and is responsible for nearly all malaria-induced mortality. Clinical manifestations of malaria are caused by the intraerythrocytic life cycle of P. falciparum. The parasite undergoes distinct morphologic changes during its 48-h life cycle inside human red blood cells (RBCs) 1 (1). After invasion into RBCs, the parasites mature from ring stage to trophozoites and then to schizonts. Mature segmented schizonts finally rupture the host erythrocytes releasing merozoites, which rapidly invade other erythrocytes to reinitiate the cycle. The mechanism of merozoite release from host RBCs is largely unknown. The cluster of merozoites inside a red blood cell is enclosed within two membranes: an inner parasitophorous vacuole membrane (PVM) and an outer RBC membrane. The rupture of these two membranes precedes the release of merozoites for subsequent round of RBC invasion. Several studies have shown that the merozoite release is susceptible to protease inhibitors. In the presence of such inhibitors, merozoites mature normally but are unable to escape from RBCs (2-4). Furthermore, a number of plasmodial proteases have been isolated and are shown to have activities against known RBC membrane skeletal proteins (5), although a functional role of these proteases in the rupture of the RBC membrane during merozoite escape has not been established.The issue of malaria parasite release fro...