Protein p126: a parasitophorous vacuole antigen associated with the release of Plasmodium falciparum merozoites

The p126 protein is synthesized by P. falciparum between the 32nd and the 36th hour of the erythrocytic cycle, and is localized in the parasitophorous vacuole. It is processed when schizonts rupture and the major fragments (50, 47 and 18 kDa), which are released into culture supernatant, have been characterized using monoclonal antibodies. The 47 kDa fragment has been mapped at the N-terminus of the molecule. The portion of the protein p126 gene coding for this fragment contains 3 introns and is characterized by a sequence coding for 6 repeats of 8 aminoacids and by repeats of TCA/T-AGT coding for a polyserine sequence of 37 serines in a row for the FCR-3 strain. The 50 kDa fragment is also found in culture supernatant when merozoites are released from mature schizonts. The incubation of mature schizonts with leupeptin inhibits the release of merozoites and, in this case, a 56 kDa intermediate product is found. In those conditions, merozoites were observed free in the erythrocyte cytoplasm, the membrane of the parasitophorous vacuole being destroyed. The 50 kDa fragment can be obtained from the 56 kDa fragment by treatment with trypsin (a protease inhibited by leupeptin). Our results suggest that the processing of the 56 kDa fragment: 1) is protease-dependent, and could depend on a trypsin-like activity; 2) cannot occur after the release of merozoites because of the protease inhibitors contained in the serum; 3) does not occur before the release of merozoites, since no processed products of the protein p126 are observed in unruptured schizonts.(ABSTRACT TRUNCATED AT 250 WORDS)

The stereoselectivity of four hepatic glutathione S-transferases purified from a marine elasmobranch (Raja erinacea) with several K-region polycyclic arene oxide substrates

Product analysis by HPLC demonstrated that three hepatic cytosolic glutathione S-transferases of little skate (E-2, E-3 and E-4) were highly stereoselective, if not stereospecific, for thiol reaction at the R-configured oxirane carbons of four K-region arene oxides; pyrene 4,5-oxide, (+/-)-benz[a]anthracene 5,6-oxide, (+/-)-benzo[a]pyrene 4,5-oxide and phenanthrene 9,10-oxide. A fourth transferase, E-5, exhibited no stereopreference with pyrene 4,5-oxide or phenanthrene 9,10-oxide. Immunological and electrophoretic evidence has shown that the three enzymes exhibiting stereospecificity have a common subunit which is absent from enzyme E-5. The high stereoselectivity of the three enzymes E-2, E-3, and E-4 was accompanied by effective catalysis of the reaction of GSH with these K-region epoxides; for example, the calculated turnover number for E-4 with benzo[a]pyrene 4,5-oxide was 550.

Immunochemical analysis of a major antigen of Plasmodium falciparum (P126) among ten geographic isolates

Protein P126, a parasitophorous vacuole major antigen of Plasmodium falciparum and precursor of 3 major exoantigens (50, 47, and 18 Kd in strain FCR-3) has been studied in 10 culture-adapted isolates originating from various endemic areas. Two monoclonal antibodies (specific for 50 and 47 Kd exoantigens, respectively) were used to immunoprecipitate culture supernatants and parasitized erythrocytes in each case. It was observed that all the parasite isolates reacted with both monoclonal antibodies, indicating the ubiquity of the epitopes analyzed. Further, two of the exoantigens (the 50 and 18 Kd of FCR-3) were found to have a stable molecular mass in all the isolates tested, whereas, the other one (47 Kd in FCR-3) was found to have a variable molecular mass, from 47 to 50 Kd. The molecular mass of the precursor varied from 126 Kd to 128 Kd. No correlation was found between geographic origin and antigenic size.

Fine needle aspiration cytology in a case of hepatoblastoma

The cytologic features of a case of hepatoblastoma diagnosed by fine needle aspiration (FNA) in an 18-month-old female infant are described. A mass detected in the left lobe of the liver on routine examination was subjected to FNA. The distinctive cytologic findings included malignant cells in small clusters and in acinar arrangements. Some of the acinar structures had bile plugs. Fat vacuoles were present within the cytoplasm of some of the malignant cells. Immature hematopoietic cells were also present.

Interactions of protein calorie malnutrition, malaria infection and immune responses

The course of parasitaemia and certain immune responses in protein or calorie-deficient albino rats infected with Plasmodium berghei (NICD) were studied. Wide variations observed in the course of parasitaemia in protein-deficient animals were (a) prolonged prepatent period, short patent period with low parasitaemia (50% of animals), (b) short prepatent period and an inability to resolve the infection (14% of animals) and (c) no patent parasitaemia at any stage of observation (23.5% of animals). The calorie-deficient animals had significantly lower parasitaemia (P less than 0.05) compared with well fed animals. Protein deficiency resulted in depression of T-dependent immune responses in uninfected as well as P. berghei-infected animals. The outcome of the parasitaemia in protein- as well as calorie-deficient animals seems to be the combined result of deficiencies of certain essential nutrients, proteins and calories in the diet as well as the immune responses of the host.

Variable virulence of isolates of Giardia lamblia in mice

Groups of inbred mice were inoculated intraoesophageally with Giardia lamblia cysts isolated from the stools of 15 patients with various clinical conditions: symptomatic diarrhoeic, symptomatic non-diarrhoeic and asymptomatic cyst carriers. The virulence of these isolates was studied in terms of two-hour cyst excretion rate and trophozoite counts in the duodenum. The basic pattern of the cyst excretion was similar in all the groups: cysts appeared in the stools by Day 3 +/- 1, reaching a maximum by Day 11 +/- 2. There was then a gradual decline until Day 23 +/- 2, with a low output until Day 31 post-inoculation. However, statistically significantly higher numbers of cysts were excreted by animals which had received cysts isolated from symptomatic diarrhoeic patients than by mice which received cysts from symptomatic non-diarrhoeic or asymptomatic cases. Identical results were obtained with the trophozoite counts. Haemagglutinating (HA) antibodies appeared after Day 11 post-inoculation in each group regardless of different cyst isolates, and the HA titre increased until Day 31 post-inoculation. The results indicate that variable symptomatology in patients could be due to variation in the virulence of the parasite.