The lack of correlation between parasitaemia and anaemia in severe malaria indicates that factors in addition to schizont rupture or erythrophagocytosis contribute to anaemia. We asked whether malaria toxin (MT) from Plasmodium berghei or P. chabaudi might impair erythropoiesis. Daily intraperitoneal injection of MT into C57BL/6 mice induced a transient reduction of RBC values by 25–30% after about 2 weeks, followed by increased haematopoiesis in the spleen as compared to mice receiving uninfected RBC preparations. There was a 3 (P. berghei) to 8-fold (P. chabaudi) increase of total proliferative activity in the spleen. Flow cytometric analyses showed that this was accompanied by some differentiation of TER-119 positive erythroid cells and of Gr-1 positive myeloid cells. Erythroid and myeloid progenitor cell-derived colony assays confirmed these results and revealed an increase in the number of CFU-E ([les ]200-fold), BFU-E ([les ]10-fold) and CFU-GM ([les ]20-fold) in the spleen of MT treated mice, as compared to controls.

The ability of deproteinated malaria exoantigens from Plasmodium falciparum (Pf-MT) and P. berghei ANKA (PbA-MT) to activate murine haematopoietic cells was analysed in vitro. Malaria toxins (MT) of both plasmodium species induced cell proliferation and the production of IFN-γ in overnight and long-term (5 days) spleen and bone marrow cultures and a reduction of the number of TNF-α spot forming cells (SFC). When added to cells of malaria-experienced animals, MT decreased the number of IL-4 SPC and increased the number of IL-5 SPC. However, the same proliferative and IFN-γ induction properties as in naive cells were observed. Simultaneous addition of IL-2 and PbA-MT to spleen cells inhibited the proliferation but increased the IFN-γ production usually induced by IL-2. Flow cytometric analysis revealed that the addition of MT triggered an expansion of CD3+ and GR1+ cell populations. Our results suggest that malaria toxins of different species can induce an immediate and strong proliferation and a TH1-type cytokine release by murine cells, independently of previous in vivo priming.

Using surface immunofluorescence isolate-specific antigens were detected on the membrane of erythrocytes infected with Babesia parasites. In addition, the strains reacted differently with Plasmagel in that the European isolate (B.c. canis) could be purified on Plasmagel effectively, whereas infected erythrocytes of the South-African isolate (B.c. rossi) could not. Experimental infection of dogs with Babesia canis isolates from geographically different areas revealed different pathology. The European isolate obtained from France exhibited transient parasitaemia, usually below 1%, associated with low PCV values and congestion of internal organs. Clinical disease was correlated with an effect on the coagulation system, and not with peripheral parasitaemia. Infection of dogs with South-African-derived isolate induced high parasitaemia usually much higher than 1%, which required chemotherapeutic treatment. In these animals clinical disease was correlated with peripheral parasitaemia and not with parameters of the coagulation system. The results show that the etiology of disease caused by these isolates of B.c. canis and B.c. rossi is different. This might have implications for the development of vaccines against these infections.

We have previously reported that the mechanisms of neuromyopathic damage induced by Trypanosoma cruzi are mediated by T cells and are parasite-strain dependent. In the present study our aim was to determine whether the humoral response against muscle and nervous system is also parasite-strain dependent. Of the sera from mice infected with RA and CA-I T. cruzi strains, 93% reacted against antigens of the nervous system (sciatic nerve, spinal cord and brain). No differences in the ability to recognize heart antigens were found between RA (48%) and CA-I (63%) antisera. Reactivity against skeletal muscle was only relevant in anti-CA-I sera at 270 days post-infection. Each of the antisera assayed in Western blots developed a particular antigenic pattern, but 3 antigens in the nervous system of molecular weight 48, 60 and 70 kDa were detected by 42, 28 and 23% of the sera, respectively. On the other hand, deposits of IgG were observed at the interstitial matrix in sciatic nerve and as endomisial and sarcolemmal patterns in skeletal muscle by IFAT for both RA and CA-I antisera. Absorption of sera with parasite antigens did not abolish the autoreactivity. Our results suggest that major serum autoreactivity from T. cruzi-infected mice is not parasite-strain dependent and does not arise from molecular mimicry.

The in vitro development of the pentastomid Porocephalus crotali from the infective, seventh (VII) instar, dissected from the tissues of rat intermediate hosts, to the adult male (X) and female (XI) instars, normally resident in the lung of rattlesnake definitive hosts, is described. The culture medium comprised washed human blood cells, resuspended in bovine serum (50[ratio ]50, v/v), with 20% minimum essential medium and antibiotics. Two batches of approximately 100 pentastomids, maintained at a density of 2 worms/ml, were cultured in 500 ml bottles in an atmosphere of 5% CO2 in air at 28°C. Culture bottles were rotated slowly on a Rollacell system and the medium was replenished every 2–3 days. Growth was monitored at various intervals by weighing worms, measuring cast cuticles with attached moulted hooks recovered from the medium, and by dissecting worms for measurements of various organ systems. Three moults separated the infective and adult male instar, whereas 4 moults were necessary in the case of females. In both cultures natural mortality was about 10% over a 160-day period, by which time 33–51% of females and 62–70% of males had reached the terminal instar. Some males attained full sexual maturity with seminal vesicles loaded with viable sperm: such males were indistinguishable from males recovered from naturally infected rattlesnakes. However, females never achieved full size, even after 200 days, and although copulation did not occur in vitro, some females became patent.

Characterization of surface coat (SC) proteins including carbohydrate-binding proteins and glycoproteins of the plant-parasitic nematode Meloidogyne javanica 2nd-stage juvenile (J2) is reported. Extraction of surface proteins with sodiumdodecyl sulfate (SDS) and separation by denaturing polyacrylamide gel electrophoresis (SDS–PAGE) results with bandsat 6, 9, 14, 22, 26, 31, 46, 49, 58, 66, 80, 205 and 250 kDa. On Western blots, the neoglycoprotein, fucosylated-,mannosylated- and glucosylated-bovine serum albumin, reacted with the 14, 22, 26, 58 and 66 kDa bands. The lectins,Concanavalin A and wheat-germ agglutinin (WGA) labelled surface protein bands of 6, 9, 14, 31, 58 and 66 kDa; WGAalso labelled the 22 and 26 kDa bands. Biotin reagents were used to specifically trace surface proteins on live J2.SDS–PAGE of biotinylated J2 extracts revealed only 2 specific biotin-protein bands at 46 and 49 kDa. The labile andtransitory nature of Meloidogyne javanica SC was demonstrated by the dynamics of human red blood cells (HRBC)adherence to J2 of different ages. HRBC adherence was also used to demonstrate the SC recovery of detergent-treatedJ2, which was further exhibited in the SDS–PAGE profiles.

Echinococcus multilocularis, a vulpine intestinal tapeworm, is the causative agent of alveolar echinococosis in humans, one of the most severe and lethal parasitic infections in man. To date, there is very little knowledge about the genetical polymorphism of this parasite. To assess sequence polymorphism, we analysed a sample of 33 E. multilocularis isolates from Europe, North America and Asia by PCR-SSCP followed by nucleotide sequencing. This assessment was performed comparatively to sheep, cattle and pig E. granulosus strains. Coding (nuclear antigen B and mitochondrial NADH dehydrogenase genes) and non-coding (introns of actin and homeobox-containing genes) regions of the parasite genome were chosen as targets. Since the estimated nucleotide diversity among genotypes of E. multilocularis were, in general, 10 times lower than among the recognized different strains of E. granulosus, we suggest that the conventional classification of the former species in 2 separated strains (European and North American) should be reviewed.

The interaction between Heligmosomoides polygyrus superantigen and human peripheral blood mononuclear cells (PBMC) was evaluated. Parasite homogenate and excretory–secretory proteins from both L4 larvae and adult worms were examined for their ability to stimulate, and be presented by, human cells. Proliferation assays using PBMC from 3 human volunteers indicated that naïve cells were stimulated by H. polygyrus superantigen. Antigen presenting cells (APC) from a number of human donors were able to successfully present H. polygyrus superantigen to mouse T cell hybridomas. However, this ability varied according to the source of the superantigen, and human APC, in contrast to APC from mice, could only present the superantigen contained within parasite homogenate. Also, in contrast to the situation with mice, human APC could present H. polygyrus superantigen to stimulate mouse T cells expressing not only TCR Vβ8.1, but also TCR Vβ7. Therefore, H. polygyrus superantigen can successfully stimulate, and be presented by, human PBMC of different MHC haplotypes, although the cellular mechanisms appear to be different from those observed in the mouse.

Infection with Toxocara canis is a common world-wide human helminthiasis, which rarely elicits central nervous system (CNS) impairment. A case-control study to investigate this discrepancy was carried out, in which the cases were 27 adult neurological inpatients for whom a definite aetiological diagnosis was lacking, and for whom positive immunodiagnosis of toxocariasis had been obtained, both in cerebrospinal fluid (CSF) and in serum. Two control groups were used. Controls were adult inpatients with other neurological diseases who had no evidence of T. canis infection of the CNS. Multivariate logistic regression analysis did not reveal any positive relation between case status and clinical signs. A significant association was observed between case status and an elevated CSF cell count. Rural residence, ownership of dogs, and dementia were shown to be risk factors for toxocaral infection of CNS. These results suggest that migration of T. canis larvae in the human brain does not frequently induce a recognizable neurological syndrome but is correlated with the association of several risk factors including exposure to dogs, a status possibly responsible for repeated low-dose infections.

A trickle infection experiment was undertaken to study in detail the population dynamics of Oesophagostomum dentatum in pigs. Three groups of 32 pigs were inoculated via the feed twice weekly with 100 (Group A), 1000 (Group B) or 10000 (Group C) O. dentatum infective larvae (L3). Five pigs from each group were killed 2, 4, 8, 12, 16, and 20 weeks after the first inoculation (p.i.) to determine their worm burdens. Weekly faecal egg counts were determined. At slaughter, worms were counted, differentiated according to sex and developmental stage, and their length measured. Faecal egg counts ranked with dose rate until week 15, but later were more variable. The proportion of the total number of L3 administered which were recovered at slaughter inversely ranked with dose rate. In group C it decreased over time, whereas in groups A and B there was no consistent pattern. Worm fecundities (epg/female) in groups A and B were higher than in group C. The lengths of the female worms increased over time, whereas the lengths of the male worms remained approximately constant from week 8. The study suggests reduced establishment of incoming larvae and lower fecundity of the female worms at high dose levels.

The anthelmintic ivermectin has a number of effects on nematodes which result in changes in behaviour, particularly locomotion, including paralysis and an inhibition of feeding. This paper describes the application of an in vitro pharmacological approach to further delineate the action of ivermectin on feeding behaviour. Contraction of Ascaris suum pharyngeal muscle was monitored using a modified pressure transducer system which detects changes in intrapharyngeal pressure and therefore contraction of the radial muscle of the pharynx. The pharynx did not contract spontaneously. However, serotonin (5-HT, 100 μm) stimulated rhythmic contractions and relaxations (pumping) at a frequency of 0·5 Hz. γ-Aminobutyric acid (GABA) and glutamic acid inhibited the pumping elicited by 5-HT. The duration of inhibition was concentration dependent (1–1000 μm) with a threshold of 1 μm and 10 μm respectively (n=8). Ivermectin also inhibited pharyngeal pumping (1–1000 nM). At lower concentrations, ivermectin (1–10 pM) potentiated the GABA and glutamate inhibition, so that inhibition occurred at concentrations which were below threshold in the absence of ivermectin. These data provide evidence that the pharynx is a site for the action of ivermectin. Thus interruption of pharyngeal processes such as, feeding, regulation of hydrostatic pressure and secretion may provide a new site of anthelmintic action.