[Analysis of retinal vein motion in glaucoma patients]. / Analyse der Venenbewegungen in der Netzhaut von Glaukompatienten.

BACKGROUND: Analysis of retinal vein amplitude in eyes of glaucoma patients. PATIENTS AND METHODS: Motion of retinal veins was captured by Retinal Vessel Analyzer in duration of 30 seconds. Inferotemporal vein segments of 500 micrometers length in the immediate vicinity of, as well as away from the optic disc were chosen. Time behavior of the average segment diameter was analyzed by the self made software: dominating frequency (heart rate) was determined by Fourier analysis, and based on this an average pulse form was produced. Difference between the highest and lowest diameter point was the subject of analysis in 25 eyes of 25 glaucoma patients and 25 age-sex-matched healthy controls. RESULTS: Pulse amplitude of retinal veins in healthy eyes was higher than in glaucoma patients: in the optic disc vicinity the pulse amplitude relative to baseline was 2.6 ± 2.1% in control eyes and 1.4 ± 0.8% in glaucoma eyes (t-test, p = 0.009). Away from the disc, it was 1.7 ± 1.0% and 1.1 ± 0.5% respectively (p = 0.01). CONCLUSIONS: Retinal veins in glaucoma eyes demonstrate lower pulse amplitudes than healthy eyes, indicating disturbance in venous outflow and increased intraluminal venous pressure.

Species-specific field testing of Entamoeba spp. in an area of high endemicity.

Entamoeba histolytica has been separated in recent years into 2 morphologically identical species: the apathogenic E. dispar and the pathogenic E. histolytica, only the latter being pathogenic. Although various laboratory techniques allow discrimination between the 2 species there is a lack of field data about the suitability of available diagnostic tests for use in epidemiological studies and few epidemiological studies using species-specific diagnosis have been performed at community level in endemic areas, especially in sub-Saharan Africa. We conducted a repeated cross-sectional study of 967 schoolchildren in central Côte d'Ivoire to compare and evaluate light microscopy, 2 different antigen detection assays, and one polymerase chain reaction (PCR) assay. Microscopy and a non-specific antigen capture Entamoeba enzyme-linked immunosorbent assay (ELISA) were used for the primary screening of all children (time t0). The prevalence of the E. histolytica/E. dispar species complex at t0 was 18.8% by single microscopical examination and 31.4% using the non-specific ELISA. Approximately 2 months after the initial screening, fresh stool specimens were collected on 2 consecutive days (t1 and t2) from (i) all the children who were positive by microscopy at t0 (n = 182) and (ii) 155 randomly selected children who were negative at the primary screening. These samples were tested with a second antigen detection ELISA specific for E. histolytica (n = 238) and with a species-specific PCR assay (n = 193). The second and third examinations (t1 and t2) revealed an additional 43 infections with the species complex E. histolytica/E. dispar, so that the cumulative microscopical prevalence for t1 and t2 was 27.7%. The overall prevalence of E. histolytica by species-specific ELISA antigen detection was low (0.83%), while the prevalence of E. dispar was 15%. When analysing only microscopically positive samples by PCR (n = 129), the ratio E. histolytica: E. dispar was very low (1:46), suggesting that the vast majority of Entamoeba infections in this area were apathogenic. Both species-specific tests performed well but the ELISA was easier to use for large-scale field screening.

Humoral immune responses during a malaria vaccine trial in Tanzanian infants.

The development of a malaria vaccine is a priority for improved and sustained malaria control. Optimal use of a vaccine in Africa will only be achieved if it can be delivered through the Expanded Programme of Immunization (EPI). We have completed a trial of the peptide vaccine SPf66 in Tanzanian infants, given alongside the EPI vaccines. This paper describes the humoral responses to SPf66 and the EPI vaccines. A total of 1207 infants were recruited into a two-arm, double-blind, individually randomized placebo-controlled trial of SPf66. The objectives of the trial were to determine the safety, immunogenicity and efficacy of SPf66 and to assess interactions with EPI vaccines when three doses of SPf66 were delivered alongside the EPI vaccines. Cross-sectional surveys were carried out to asses seroconversion rates to the EPI vaccines and the antibody response to SPf66 (NANP)50 and Plasmodium falciparum lysates. Seroconversion rates to EPI vaccines were high and no statistically significant differences in prevalence or titres were found between SPf66 and placebo recipients. IgG antibodies against SPf66 (NANP)50 and whole P. falciparum lysate were present in high titres in mothers of recruited children at the time of birth. Vaccination with SPf66 stimulated a good anti-SPf66 IgG response which declined to preimmunization levels by 2 years of age and which was not associated with protection against clinical malaria. The vaccine induced no IgG antibodies against (NANP)50 or P. falciparum lysates. SPf66 stimulated a humoral immune response when given to very young infants and did not interfere with seroconversion to EPI vaccines. The response to SPf66 was qualitatively different from that seen in older children, in whom SPf66 has been shown to be moderately efficacious. This difference raises concerns about the difficulties of immunizing very young infants who need to be targeted by antimalarial vaccination programs.

Analysis of Plasmodium falciparum infections in a village community in Northern Nigeria: determination of msp2 genotypes and parasite-specific IgG responses.

The genetic diversity of P. falciparum and multiplicity of infection has been studied in a village in Northern Nigeria at the end of the rainy season, when transmission is high. We analysed blood samples from 104 individuals aged 5-70 years by polymerase chain reaction (PCR) amplifying the gene for the merozoite surface protein MSP2 followed by genotyping based on restriction fragment length polymorphism (RFLP). 94.2% of all samples were parasite positive by PCR and over 80% of those had multiple infections. The age distribution of the average number of parasite clones present in P. falciparum infections showed an initial increase, then reached a peak multiplicity in children 8-10 years of age, and afterwards decreased significantly with age. Mean multiplicity in those 8-10-year-old children was 5.4 clones per carrier. Peak multiplicity and parasite diversity in Nigerian individuals is compared to findings from other study sites in Africa and PNG. The prevalence of IgG antibodies against the circumsporozoite protein (CSP), an indicator for malaria exposure, was over 85% in all age groups showing a high exposure of villagers to P. falciparum. OD values in ELISA were positively correlated with age. There was no correlation between the level of IgG against CSP and the multiplicity of P. falciparum infections determined by PCR of msp2. These results imply that in highly endemic areas multiplicity of infection is not directly correlated with exposure to P. falciparum.

Immune responses to Plasmodium falciparum antigens during a malaria vaccine trial in Tanzanian children.

Among Tanzanian children living in an area of intense and perennial malaria transmission, prevalence of naturally acquired IgG antibodies that recognize SPf66, NANP, p190 and a 19 kDa fragment of the merozoite surface protein-1 (MSP-1) is high and increases with age. This possibly reflects the high level of natural exposure of the children to P. falciparum. The prevalences of IgG antibodies that recognize the three putative merozoite derived sequences contained in the malaria vaccine SPf66 (83.1, 55.1 and 35.1) is low but also show some age dependence. Three doses of the SPf66 vaccine induce a strong IgG antibody response against both the SPf66 construct, NANP and the three individual peptides. Vaccination with SPf66 did not result in an increase of anti19 kDa fragment antibodies. This reflects the specificity of the humoral immune response induced by the SPf66 construct. Among vaccinated children, antibody titres against SPf66 decreased over time following the third dose. However, 18 months after the third dose, SPf66 recipients still had significantly higher IgG titres and stimulation indices of peripheral blood mononuclear cells (PBMC) than placebo recipients. Within the vaccine group, there is a trend for increasing anti-SPf66 IgG titre to be associated with decreasing risk of clinical malaria but this was not statistically significant. Results also show the difficulties of establishing whether antibody responses are related to protection in field trials in endemic areas.

Thiabendazole vs. albendazole in treatment of toxocariasis: a clinical trial.

Between 1986 and 1988, 34 patients (age range six to 83 years) with visceral or ocular larva migrans were randomly assigned to a five-day treatment with thiabendazole 2 x 25 mg kg-1 day-1 (15 patients) or albendazole 2 x 5 mg kg-1 day-1 (19 patients). On the fifth treatment day, six patients (40%) in the thiabendazole group and 11 patients (58%) in the albendazole group showed excellent or good drug tolerability. Efficacy of treatment was assessed after 30 weeks (range six to 56 weeks). In the thiabendazole group, median eosinophilia remained at 14% and four patients (27%) were clinically cured. In the albendazole group, the median eosinophilia decreased from 10 to 3.5% and six patients (32%) were clinically cured. We recommend albendazole for treatment of visceral and ocular larva migrans with a minimum dose of 10 mg kg-1 daily for five days.