Testing of newly developed glycophospholipid antigen for the detection of P. falciparum malaria by laser light immunoassay in endemic and non-endemic areas.

A glycophospholipid (GPL) antigen isolated from Plasmodium falciparum culture supernatant has been tested for its antigenicity. Detection of malaria positive known blood samples and unknown field samples from endemic and non-endemic areas were compared. In this study laser light scattering immunoassay (LIA) was used for the detection of P. falciparum malaria. Test results of control (malaria negative samples from Surat) were compared with known positive samples and unknown malaria positive field samples. A positive correlation has been observed (97%) in falciparum positive samples from laboratory and unknown samples from endemic area (Haldwani) by LIA method using GPL antigen. From the results of the study it was found that GPL antigen has a better antigenic property and can detect almost all the cases of Pf malaria by LIA method.

Diagnosis of intestinal amebiasis using salivary IgA antibody detection.

Attempts were made to use soluble antigen extract of strain HK-9 of Entamoeba histolytica to detect salivary IgA antibodies in intestinal amebiasis patients by using ELISA. Total salivary samples of 109 individuals were divided into four groups. Group I comprised 32 patients whose stools were positive only for E. histolytica cysts and/or trophozoites. Group II comprised 12 individuals whose stools were positive for E. histolytica and other intestinal parasites. Group III comprised 36 individuals whose stools were negative for E. histolytica but contained other intestinal parasites such as E. coli, E. nana, Blastocystis hominis, Trichomonas hominis, Giardia lamblia, Opisthorchis viverrini, and hookworm. Group IV comprised 29 healthy individuals whose stools were free from any intestinal parasitic infections. Based on the mean optical density, OD + 2SD of the results from 29 parasitologically negative healthy individuals, the cut-off OD value for salivary IgA antibodies was 1.265. Therefore, the assays were positive in 14 out of 32 (43.75%) of group I and 2 out of 12 (16.6%) of group II. The assays were positive in 16 out of 36 (44.44%) for group III whereas 2 out of 29 (6.90%) for group IV were positive. The overall sensitivity and specificity of the assays were 36% and 72%, respectively. The false positive rate was 28% and the false negative rate was 64%. The predictive values of positive and negative results were 47% and 63%, respectively. The diagnostic accuracy of ELISA for the presence of salivary IgA antibodies was 58%.

Long term maintenance of Toxoplasma gondii (Rh strain) in Vero cell line and use of harvested antigens for immunodiagnosis.

Thirty in vitro serial passages of Toxoplasman gondii cultures in Vero cell line performed once in every five days had a mean increase in parasite count of 74.4 +/- 14.8 times from that of initial counts. Long term cultures in Vero cell line did not alter the virulence of the parasite. The good correlation (r = 0.99) between the IFA titer and ELISA OD values using the parasite antigens from in vitro sources indicates that long term maintenance of T. gondii in culture does not affect significantly the ability to recognize antibodies to surface and soluble antigens. The results also show that soluble antigens containing host cells can be directly used for immunodiagnostic purposes without purification. The in vitro maintenance of T. gondii is safer and cheaper when compared to the in vivo method.

Protein A-antibody mediated hemagglutination assay for serodiagnosis of amebic liver abscess.

A successful modification of the indirect hemagglutination test to demonstrate antibodies for serodiagnosis of amebic liver abscess has been described in the present study. In the modified test, the protein A-IMA, Staphylococcus aureus (Cowan's strain I) bearing protein A (SAPA) cells were used to enhance hemagglutination of sensitized red cells. Use of SAPA cells markedly enhanced sensitivity of the test and greatly increased the titers obtained with most of the sera. At a diagnostic antibody titer of 1:128 and above, the protein A-IHA could detect 72 (100%) of amebic liver abscess (ALA) cases. Amongst the controls, no false positive reaction was observed in non-amebic liver disease controls. However 1(2%) of sera demonstrated false positive reactions from healthy controls. The protein A-IHA was highly sensitive when compared with that of the indirect hemagglutination (IHA) for serodiagnosis of amebic liver abscess. The novel immunoassay is simple, inexpensive and requires little technical skill. It has the potential for wide application in serodiagnosis of amebic liver abscess.