Plasmodium yoelii: Antibody and the maintenance of immunity in BALB/c mice

Subpatent persistence of parasitemia was detected for up to 7 weeks after infection of BALB/c mice with Plasmodium yoelii. Serum taken from recovered mice maintained parasitemias in recipient mice at a subpatent level when transferred repeatedly at 2-day intervals. Single doses of serum from convalescent donors delayed the course of infection in recipients. Small doses of transferred hyperimmune serum had the same effect, whereas large doses (>0.5 ml) totally suppressed parasitemia. Only a single secondary challenge of recovered mice was required in order to produce a maximally protective hyperimmune serum. Mice completely protected from a primary challenge with P. yoelii by transfer of hyperimmune serum were not at all resistant to a second challenge given some weeks later. After transfer of hyperimmune serum into mice with established P. yoelii infection, parasitemia fell to subpatent levels within 48 hr. During the first 21 hr after serum transfer, a progressive reduction in the proportion of ring forms present in blood smears was observed.     

Plasmodium berghei: Architectural analysis by freeze-fracturing of the intraoocyst sporozoite's pellicular system

The technique of freeze-fracturing has been used to study the architecture of the pellicular complex of the intraoocyst sporozoite of Plasmodium berghei. The sporozoite is surrounded by three plasma membranes and a layer of subpellicular microtubules. During freeze-fracturing, each of the three membranes can split along its hydrophobic interior to yield a total of six fracture faces. The most obvious feature of each fracture face is the presence of globular intramembranous particles on the surface. The six fracture faces differ from one another in arrangement, size, and density of these intramembranous particles. Two of the fracture faces exhibit a unique arrangement of particles in well-organized parallel rows along the long axis of the sporozoite. This arrangement has not been reported in either the erythrocytic or the exoerythrocytic forms of Plasmodium spp. Another unique feature in the sporozoite revealed through freeze-fracturing is a single suture line that traverses the long axis of the inner two membranes of the parasite.     

Plasmodium berghei: effect of antithymocyte serum on induction of immunity in the mouse.

Swiss mice, immunized against the malaria parasite Plasmodium berghei, were treated with antithymocyte serum (ATS) at various times before and after challenge with the homologous parasite. Strong sensitivity to ATS treatment was observed at the end of the sensitization period, and especially if administered close in time to the challenge inoculum. Sensitivity to ATS treatment was reduced again within a period of 1 to 2 days after challenge. When a breakthrough of parasitemia after ATS treatment was prevented by chemoprophylaxis, a recovery from the state of immunodepression and reestablishment of immunity occurred within a period of 1 to 2 weeks.     

Plasmodium berghei: diet and drug dosage regimens influencing selection of drug-resistant parasites in mice

Two different diets for the host and three drug dosage regimens were used to select lines resistant to sulfadoxine and pyrimethamine from the parent strain of the rodent malaria parasite Plasmodium berghei [the N (K173) strain]. A higher yield of resistance was obtained when a high parasitemia was present at the beginning of the drug pressure schedule. The development of resistance to the association of sulfadoxine plus pyrimethamine was accelerated by a relatively high para-aminobenzoic acid (PABA) content diet. Reproducibility was satisfactory when one of the dosage regimens was applied independently by two different technicians at different times.     

Plasmodium berghei: uptake of clindamycin and its metabolites by mouse erythrocytes with clindamycin-sensitive and clindamycin-resistant parasites.

Tritiated Clindamycin was used to compare the uptake of Clindamycin in plasma and red cells of mice infected with clindamycin-sensitive or clindamycin-resistant Plasmodium berghei and in uninfected mice. Red cells infected with either sensitive or resistant parasites have a higher concentration of [³H]clindamycin and its active metabolites 1 hr after drug administration than uninfected red blood cells. There was no significant difference in uptake of Clindamycin by red blood cells parasitized by sensitive or resistant parasites. Levels of Clindamycin and its metabolites were consistently higher in red cells than in plasma, both in infected and uninfected mice, but the drug was readily removed by washing red cells with phosphate buffered saline in either case. It is concluded that resistance to Clindamycin is not due to an impaired uptake of the drug by the parasitized red cell as has been shown for chloroquine resistance in P. falciparum and P. berghei.     

Plasmodium berghei: modification of sialic acid on red cells from infected mouse blood

The surface membrane glycoproteins of normal mouse erythrocytes can be labeled by oxidation with either periodate or galactose oxidase in the presence of neuraminidase, followed by reduction with NaB³H₄. Without neuraminidase there is little galactose oxidase-catalyzed labeling of protein. Analysis of labeled proteins by SDS-polyacrylamide gel electrophoresis showed that both methods labeled the same set of glycoproteins. Plasmodium berghei infection dramatically reduced the sialoglycoprotein labeling of red blood cells from infected blood using the periodate/NaB³H₄ method. Provided neuraminidase was present, labeling by the galactose oxidase method gave identical results to normal erythrocytes. We conclude that the glycoprotein sialic acid of uninfected as well as infected red cells is modified during infection such that it is refractory to periodate oxidation. Acylation of the exocyclic hydroxyls of sialic acid is suggested to account for this. Lectin binding and cell agglutination experiments using Limulin, soybean and wheatgerm lectins, and concanavalin A confirmed and extended these observations. The possible implications of these results with regard to anemia induced by malaria are briefly discussed.     

Plasmodium yoelii: blood oxygen and brain function in the infected mouse

The carriage of oxygen by the blood and the in vivo response of the brain were investigated in mice infected with a lethal strain of Plasmodium yoelii. All mice with parasitaemia exceeding 70% were severely anaemic (Hb 3.5 +/- 1.8 g/dl; mean +/- 1 SD), acidotic (blood pH 7.04 +/- 0.06) and hypoglycaemic (blood glucose 0.6 +/- 0.76 mumol/ml). The oxyhaemoglobin dissociation curve (ODC) of blood from heavily infected mice was shifted right as compared to controls, but the increase in p50 was less than expected from the accompanying acidosis. The reduced shift right was due to a decrease in the 2,3-DPG/Hb ratio in infected animals (0.72 +/- 0.12, n = 17 vs 1.10 +/- 0.09, n = 12 in controls). Despite the severity of terminal infection, the cerebral pH and the relative steady-state concentrations of PCr, ATP and Pi measured in vivo by nuclear magnetic resonance (31P NMR) were normal. Alterations in brain energy status and pH cannot account for cerebral signs or death in this proposed mouse model of cerebral malaria.     

Plasmodium berghei: Electron spin resonance and lipid analysis of infected mouse erythrocyte membranes

Red blood cells from mice infected with Plasmodium berghei and from uninfected mice were labeled with stable, free radical derivatives of stearic acid. Electron spin resonance spectra of these samples showed that the degree of molecular order in these membranes decreased, and the rate of motion of the probe increased, with increasing levels of parasitemia. Parasitemia increased the ratio of unsaturated to saturated 18-carbon fatty acids, and decreased the percentage of arachidonic acid and of cholesterol. The effects of parasitemia on the membrane properties correlated with decreases in cholesterol/fatty acid ratios.     

Eimeria nieschulzi and Trichinella spiralis: Analysis of concurrent infection in the rat

The effects of concurrent primary infection of the rat with Eimeria nieschulzi and Trichinella spiralis on the number of oocysts of E. nieschulzi shed by the host and on the number, distribution, and fecundity of adult T. spiralis were analyzed. When rats were initially infected with E. nieschulzi followed 9 days later by infection with T. spiralis there occurred a significant decrease in the total numbers of adult worms in the small intestine, a significant shift in the position of these worms along the length of the small gut, a decrease in the fecundity of adult female worms, and a decrease in muscle parasitism when compared with rats infected with T. spiralis alone. When rats were initially infected with T. spiralis, followed 9 days later by infection with E. nieschulzi, there occurred a significant decrease in the numbers of oocysts shed over 24 hr on Days 7, 9, and 11 postinfection below that seen with rats infected only with Eimeria. These changes are discussed in terms of the enteropathophysiologic lesions and enteric inflammation known to occur during infections with these two parasites.     

Nematospiroides dubius: arrested development of larvae in immune mice.

When immune NIH mice were killed 10 days after a challenge infection with Nematospiroides dubius, approximately 10% of the inoculated larvae were recovered from the intestinal lumen, irrespective of the dose administered. When such mice were treated with cortisone from Day 10 for a period of 8 to 14 days and were subsequently killed for worm counts, it was found that they had significantly more worms than the immune control mice killed on Day 10. During the week following the beginning of treatment with cortisone there was little change in the low worm burdens in immune mice. However, 9 to 11 days after this treatment worm counts indicated that worms were accumulating in the intestinal lumen, and concurrently eggs were recorded in the feces of the mice. These observations indicated that a period of 9 to 11 days was required after the initiation of cortisone treatment on Day 10 for the worms in immune mice to complete their development to the adult lumen-dwelling stage. It is suggested that the larvae in the challenge infection became arrested early in their development in the intestinal wall and that growth resumed only after cortisone treatment. When treatment with cortisone was initiated later after challenge, it was still effective in reactivating arrested worms, but the lower worm recoveries in these mice indicated that the arrested larvae were being slowly rejected by the host. In subsequent experiments it was established that the arrested larvae of N. dubius were insusceptible to the activity of pyrantel embonate, an anthelmintic which is 99% effective against adult worms in the intestinal lumen. The mechanism whereby the larvae of N. dubius became arrested in immune mice and subsequently resumed their development after cortisone treatment is discussed.     

Plasmodium berghei: a mouse model for the "sudden death" and "malarial lung" syndromes

A mouse model for the "sudden death" and "malarial lung" syndromes is described. Mice of the C3H/z strain succumb suddenly approximately 7 days after an infection with Plasmodium berghei becomes patent, at a time when parasitemia is still moderate (6 to 8%). Death could be shown to be due to anaphylactoid shock, probably induced by soluble immune complexes. Increased vascular permeability caused transudation and leakage of serum proteins into the interstitium and the alveoli. The lungs were found to be edematous, with a fine granular precipitate in the alveoli and adherent to the vascular walls. The precipitates reacted with antiglobulins G and M, and could be shown to also contain malaria antigens and C3/4. A dramatic drop in hematocrit was recorded several hours before death, indicating the sudden release of malaria antigens. The myocardium of animals that had died very suddenly showed a patchy loss of phosphorylase activity. This loss of activity was much more extensive, and sometimes almost total, when there had been an agonal period of several (1 to 3) hours before death. In these cases the irreversibility of the myocardial damage was also indicated by the loss of activity of the dehydrogenases, as well as by typical inflammatory reactions of granulocytic and histiocytic infiltrations. The hearts thus presented a typical picture of the acute and peracute shock syndromes. In acute shock cardiac insufficiency develops so suddenly that death ensues before irreversible damage has occurred, and cardiac insufficiency can only be demonstrated by the most sensitive of enzyme histochemical means. In the present case shock was induced by the anaphylactoid activity of immune complexes with the lung as target organ. The described syndrome appears analogous to human "malarial lung."     

Plasmodium falciparum: comparative analysis of antigens from continuous in vitro cultured and in vivo derived malarial parasites

A comparison of metabolically labeled proteins from continuous in vitro and in vivo derived Plasmodium falciparum revealed both similarities and differences. Metabolic labeling of synchronized cultures showed that the uptake of label increased as the parasites matured from the ring to the schizont stage in both cultures. Also, in both continuous in vitro and in vivo derived cultures, prominent high-molecular-weight proteins were synthesized during the late developmental stages. However, the continuous in vitro cultured parasites incorporated twice as much of the label at each stage as did the in vivo derived parasites. Immunoprecipitation with serum samples from vaccinated Aotus trivirgatus griseimembra monkeys revealed major differences involving protein antigens that migrated in the molecular weight regions of b (Mr = 152,000), c (Mr = 143,000), j (Mr = 82,700), and n (Mr = 57,400). These antigens were more readily detected in the continuous in vitro cultured schizonts than in the in vivo derived schizonts.     

Heligmosomoides polygyrus: inoculum size and glucose, ion, and gas fluxes in the small intestine of mice

Female CDI mice were inoculated with 10, 50, 100, 250, or 500 larvae of Heligmosomoides polygyrus. At Days 7, 9, and 12 after infection, the anterior third of the small intestine was perfused using an in vivo technique. The distribution of worms in the mouse intestine was determined after 7, 9, and 12 days. All worms that were recovered were from the proximal half of the small intestine. When compared to uninfected controls, there was a significant increase (+56%) in glucose absorption of the small intestine at Day 7 after infection with inocula of 50 and 100 larvae; at Day 9, glucose absorption was significantly increased with a 10-larvae inoculum. A decrease in glucose absorption occurred at Days 7 and 9 after infection with a 500-larvae inoculum. Net water absorption was significantly increased (+183%) with the 50- and 100-larvae inocula at Day 7, but was significantly reduced at Day 9 after infection with the 50-, 100-, 250-, and 500-larvae inocula. Both Cl- and Na+ absorption were significantly increased with the 50-, 100-, and 250-larvae inocula at Day 7 after infection; at 9 and 12 days, there was significant net secretion of both ions. In control mice, there was net secretion of K+, while with the 50-, 100-, and 250-larvae inocula on Day 7 there was significant net absorption of K+ ions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasmodium chabaudi: relationship between the occurrence of recrudescent parasitaemias in mice and the effective levels of acquired immunity

In NIH inbred mice infected with the $\text{A}\text{S}$ strain of Plasmodium chabaudi the erythrocytic infection shows an acute primary parasitaemia which becomes subpatent after about 2 weeks. A period (7–10 days) of subpatency follows before a short-lasting patent recrudescence appears. The appearance of the recrudescent parasitaemia was examined in relation to (1) the level of antiplasmodial antibody detected by the indirect fluorescent antibody (IFA) test, (2) the antiparasite activity of the serum measured by the passive protection test, and (3) the ability of the mice to control and eliminate a large intravenous challenge infection. In the period between the primary parasitaemia becoming subpatent and the onset of the recrudescence there was a slight drop in the IFA levels, and a steep decline in passive protective levels and in the ability of the mice to control a large intravenous challenge infection. It is suggested that a decline in the effector arm in the immune response contributes to emergence of the recrudescent parasitaemias.     

Plasmodium yoelii: comparison of indirect immunofluorescence and radioimmunoassay for detecting monoclonal antibodies to malaria

The techniques of indirect immunofluorescence (IFA) and radioimmunoassay (RIA) were compared for efficiency in detecting antimalarial monoclonal antibodies in culture supernatants following lymphocyte hybridization. Culture supernatants from 479 wells were examined. Approximately 9% of the wells were found to contain antibodies to Plasmodium yoelii by IFA and 13% by RIA analysis. However, only 4.6% of the wells were positive by both IFA and RIA techniques. In general, stage-specific hybrids were more easily detected in IFA than RIA tests, whereas monoclonal antibodies binding to non-stage-specific antigens were more readily detected by RIA than IFA analysis. Selected monoclonal antibodies of the IgG and IgM classes were purified by protein A and molecular-weight-exclusion chromatography, respectively. The minimal amount of monoclonal antibody required to give a positive IFA reaction ranged from 1.6 to 100 μg antibody/ml (0.03-2 μg antibody/test), but only 0.1 to 100/μ.g antibody/ml (1 ng-2 μg antibody/test) was needed to produce a positive RIA reaction. Use of an isotype-specific RIA for screening for antimalarial antibodies resulted in the detection of additional hybridomas missed by standard IFA and RIA tests. Thus, it is important to use several serologic methods if maximal efficiency in detecting antimalarial monoclonal antibodies is to be achieved.     

Plasmodium berghei: T cell-dependent autoimmunity

Plasmodium berghei infection in euthymic mice induced the formation of smooth muscle autoantibodies (SMA) persisting in cured immune mice. Antinuclear antibodies (ANA) were found in challenged hyperimmune mice, but not in acutely infected mice. The autoantibodies were not detected in infected and cured athymic, nude mice, and are therefore T-cell dependent. No evidence for other autoantibodies was obtained. Parallel studies on deposited immune complexes in renal glomeruli served as control for any absence of autoantibodies.