[Is there a future for vaccines against gastrointestinal helminths?]

Vaccines against gastro-intestinal helminths have a large market potential, but they also generally have a narrow range of activity. This is a major drawback in the competition with the broad-spectrum anthelmintics and there is still a long way to go before molecular (recombinant) vaccines will appear on the market. Major problems are the induction of protective gut-mucosal immunity with subunit vaccines and the differences in genetic background within host populations, which largely determine the efficacy of vaccination. As yet the changes for vaccines against blood- and tissue parasites, comprising a number of veterinary important protozoa, seem to be better.

Chemotaxis of the peritoneal cells and the detection of a chemo-attractant in the effluent from peritoneal dialysis patients

The migration of peritoneal cells from 25 continuous ambulatory peritoneal dialysis patients and eight healthy women undergoing laparoscopy were studied. Peritoneal cells of continuous ambulatory peritoneal dialysis patients migrated to commonly used chemoattractants, like N-formyl-methionyl-leucyl-phenyl-alanine-methyl- ester and casein, but they also migrated to high concentrations of recombinant interleukin-1 alpha and to endotoxin (lipopolysaccharide). In the peritoneal effluent from continuous ambulatory peritoneal dialysis patients a rather heat stable chemoattractant was found with a molecular weight of 40-200 kDa with an optimal activity at approximately 125 kDa. The chemoattractant is a protein and is not complement factor 5a or interleukin-1 and was only found in peritoneal effluent from continuous ambulatory peritoneal dialysis patients, but not in peritoneal fluid from healthy women undergoing laparoscopy. Therefore, peritoneal dialysis might induce the generation of a chemoattractant. The optimal chemotactic response of peritoneal cells from continuous ambulatory peritoneal dialysis patients to N-formyl-methionyl-leucyl-phenyl-alanine-methyl- ester in medium could be enhanced by replacing the medium by peritoneal effluent. So the chemotaxis of peritoneal cells to the factor in the peritoneal effluent is caused by another mechanism, which might involve different cell surface receptor populations, than the chemotactic response to N-formyl-methionyl-leucyl-phenyl-alanine-methyl-ester.

HLA-DR expression on human peritoneal macrophages in vivo and in vitro

Qualitative, semi-quantitative (immuno-electronmicroscopy), and quantitative (radioimmunoassay) measurements were made of the in vivo and in vitro expression of HLA-DR on continuous ambulatory peritoneal dialysis (CAPD) patients' peritoneal macrophages (M phi) and on healthy persons' blood monocytes (MO). In vivo, great variation is seen in both the qualitative and (semi-) quantitative expression of HLA-DR in peritoneal M phi. After culturing for 5 to 20 h, CAPD patients' M phi with low to intermediate numbers of HLA-DR molecules per cell (25-80 x 10(3] showed a two- to threefold enhancement of HLA-DR expression. This enhancement was determined for the total peritoneal cell (PC) population and for the adherent subpopulation of peritoneal M phi and blood MO. CAPD patients whose cells initially had high numbers of HLA-DR molecules (80-110 x 10(3] showed no or only slight enhancement of HLA-DR expression when cultured.

Most CD4+ T cells from human immunodeficiency virus-1 infected patients can undergo prolonged clonal expansion

We have addressed the capacity of HIV-1 infection to alter the growth of primary CD4+ T cells, but at the clonal level. Single T cells were expanded in the presence of PHA, IL-2, and small numbers of accessory dendritic cells. We report two new findings. First, T cells from seropositive individuals, even those with AIDS and markedly reduced CD4+ counts, exhibit a normal cloning efficiency, and proliferative capacity. This result is in contrast to two prior reports of a low cloning efficiency in CD4+ T cells from HIV-1-infected patients. Second, when we added high doses of exogenous HIV-1 to T cell clones from control subjects, we observed infection but not cytotoxicity or loss of CD4+ cells, following addition of virus stocks at days 0, 3, and/or 7 of clonal growth. The same HIV-1 isolates markedly reduced CD4+ T cells in bulk mononuclear cultures. When tested at day 11, HIV-1 mRNA was expressed in some cells of exogenously infected clones by in situ hybridization; when tested at day 18, several clones could transactivate a TAT-sensitive cell line. These findings suggest that the loss of CD4+ T cells in infected individuals is not the inevitable result of the activation of latent infection, or spread of a productive infection, during clonal growth.

Isolation and partial characterisation of a potentially pathogenic cysteine proteinase from adult Dictyocaulus viviparus

Dictyocaulus viviparus adult worms feed on pulmonary tissues and cause significant pathology in the bovine host. In this report, acidic extracts of these organisms were examined for cysteine proteinase activity. A soluble thiol-dependent proteinase with native molecular weight of approximately 25 kDa was isolated and partially purified. This enzyme had maximal activity at acidic pH and showed inhibitor susceptibilities similar to the vertebrate acidic cysteine proteinases. When stored at 4 degrees C, it was stable at pH 5.0 for at least 10 days and at pH 7.0 for at least 24 h. The D. viviparus cysteine proteinase was capable of degrading type I collagen and hemoglobin. It is suggested that this enzyme may be involved in the nutrition of this parasite and/or have the potential to contribute to bronchial pathology in cattle.

Peritoneal dialysis fluid induces change of mononuclear phagocyte proportions

Peritoneal macrophages from uninfected continuous ambulatory peritoneal dialysis (CAPD) patients in general show two different, endogenous peroxidase activity (PA) patterns: exudate and negative. This suggests, in accordance with the animal model, that these macrophages are changed proportionately in CAPD patients. This chronic change may be caused by mechanical stimulation alone (massage) or the composition of the dialysis fluid used. Therefore in the rat model both physiological saline and commercial dialysis fluid were intraperitoneally (i.p.) administrated. Our results on the PA-pattern of peritoneal macrophages do indicate that a single i.p. administration of commercial dialysis fluid induced an acute exudate, especially when compared with the minor saline effect. These results are confirmed by the percentage of macrophages positive for a differentiation antigen recognized by the monoclonal antibody ED2. In addition the percentage of Fc-receptor positive peritoneal cells is more enhanced after i.p. injection of dialysis fluid when compared with the saline effect. These findings strongly suggest that the dialysis fluid used in peritoneal dialysis patients is the inducer of exudate peritoneal macrophages in these patients.

Distinct subpopulations of elicited human macrophages in peritoneal dialysis patients and women undergoing laparoscopy: a study on peroxidatic activity

The endogenous peroxidatic activity (PA) pattern of peritoneal macrophages from 24 continuous ambulatory peritoneal dialysis (CAPD) patients and from five healthy women undergoing laparoscopy was studied. In general, the macrophages showed two different PA patterns in vivo: exudate and negative macrophages. However, two of 24 CAPD patients showed resident macrophages, the first described in vivo in man. Since, in general, the examined human peritoneal macrophages are exudate and PA-negative, this suggests, in accordance with the animal model system, that a chronic sterile inflammation exists in the peritoneal cavity of CAPD patients and healthy women undergoing laparoscopy. After 2 hr culture, blood monocytes and peritoneal macrophages transformed into cells with the characteristics of exudate-resident and resident macrophages, so isolation procedures that include short periods of culture can change the developmental stage of human monocytes and macrophages.

Use of ELISA to assess lungworm infection in calves

The enzyme-linked immunosorbent assay (ELISA) technique was applied to the detection of lungworm infections in calves. In experimentally infected animals different responses to larval and adult worm antigens were observed. The response to adult worm antigens was delayed in vaccinated animals when infection occurred by the gradual uptake of infective larvae from contaminated pasture. A serological survey in The Netherlands demonstrated a high incidence of lungworm infection in both vaccinated and unvaccinated herds. There was a good correlation between anti-adult worm and anti-larval ELISA-titres. ELISA appeared to be a useful technique for assessing the level of lungworm infection in a herd.

The fieldmaster 101 PR automatic visual field screener--technical evaluation and clinical results

The perimetric concept and the technical construction of the Fieldmaster 101 PR were evaluated. 64 eyes of patients and 10 normal subjects were examined. We conclude that the Fieldmaster is a well-engineered instrument, using an inefficient test strategy. The presentation of visual field results could be improved. Clinical results of the patient examinations are presented.

A case of Acanthamoeba keratitis in The Netherlands

A severe kerato-iritis of the right eye of a 36-year-old healthy man constituted a diagnostic and therapeutic problem. More than seven months after the onset of his complaints a cornea transplantation was carried out because a large abscess had developed in the stroma of the cornea and perforation was feared. Amoebae, belonging to the free-living genus Acanthamoeba, were found in the excised corneal disc. Similar infections have been described earlier in the USA, in England and in Germany. The case described here is the first well documented one in the Netherlands. The case history and identification of the amoeba are described. Data from the literature on epidemiology, pathogenicity and treatment are discussed.

A seroepidemiological study of amebiasis in Surinam by the enzyme-linked immunosorbent assay (ELISA)

Sera from nine populations in Surinam, South America, were screened for antibodies against Entamoeba histolytica by the enzyme-linked immunosorbent assay (ELISA) technique and a precipitin test (gel diffusion or counterimmunoelectrophoresis). In two small surveys in 1974 and 1978, a high rate of clinically significant ELISA titers was found in a rather isolated group of Amerindians living near the Brazilian border, predominately in the youngest age groups. Amerindians living near the coast showed a low level of seropositivity. Low levels were also found in Bush Negro villages in the interior of Surinam and in Hindustani school children from the savannah area. A high frequency of ELISA titers greater than or equal to 320, indicating a high rate of invasive amebiasis, was detected in persons in a mental institution in Paramaribo. It is concluded that the ELISA, which is much more sensitive than the precipitin tests, is a useful screening test for assessing the prevalence of invasive amebiasis on an epidemiological scale.

Virulence of bacteria-associated, Crithidia-associated, and axenic Entamoeba histolytica: experimental hamster liver infections with strains from patients and carriers

Experimental infections of the hamster liver were carried out with five strains from patients with clinical amoebiasis and ten strains from asymptomatic carriers. Inocula of comparatively small size (12000-36000 amoebae) were injected under the liver capsule. 1. The virulence of the patient strains varied from 21-96% (see article) and declined sharply within 7-15 weeks after elimination of the associated bacterial flora. The virulence of the carrier strains varied from 0-100%, probably fluctuating with changes in the concomitant bacterial flora (Table 1). 2. The interrelation between size of inoculum, period of bacteria-free growth, and virulence was demonstrated with a Crithidia-associated patient strains (Table 2). 3. A patient strain showed a faster decrease of virulence during axenic than in Crithidia-associated cultivation (Table 3). 4. Two successive passages through hamster liver resulted in a marked increase of virulence of two bacteria-free strains, lasting for several months (Table 4). 5. A significant enhancement of virulence of Crithidia-associated and axenic amoebae by reassociation with a mixed bacterial flora during two weeks, followed by elimination of the bacteria, was demonstrated with two strains. The restored virulence was lost again within a few weeks (Table 5). 6. The virulence of an attenuated patient strain did not become manifest by adding large numbers of dead amoebae to the inoculum (Table 6). 7. The pathology of the different lesions caused in the hamster liver by the amoebae is described, including one of a granulomatous type, frequently found after inoculation with bacteria-free amoebae. 8. In an attempt to explain the occurrence of strains differing in pathogenicity an hypothesis is put forward based on the idea of selection of virulence and avirulent amoebae.

Monoxenic and axenic cultivation of carrier and patient strains of Entamoeba histolytica

All of five strains of Entamoeba histolytica, isolated from symptomatic cases of amoebiasis, could be adapted to axenic growth on the TP-S-1 medium of Diamond (1968). Four axenic strains were started from amoeba-Crithidia cultures; one could be axenized directly after isolation from a case of cutaneous amoebiasis. Attempts to monoxenize, resp. axenize strains, isolated from Dutch, asymptomatic carriers, were less successful. Only three out of ten strains could be submitted to bacteria-free growth. These three strains, however, originated probably from a recent case of intestinal amoebiasis. The results, suggesting that highly virulent strains can be easier cultivated bacteria-free than those with low or no virulence, are further discussed. The yield of axenic amoebae per tube fluctuates largely depending on many factors such as the strain, the number of transfers (i.e. degree of establishment), the quality of Panmede liver digest and serum in the TP-S-1 medium, and the care of manipulating the cultures. For optimal growth, a more acid medium was required in an amoeba-Crithidia culture than in an axenic culture. Multinucleated, giant amoebae were frequently observed in axenic cultures.