Indirect Fluorescent Antibody Test Titers Research Articles

In vitro inhibition of intracellular growth of Plasmodium falciparum by immune sera.

Beginning at the ring stage, synchronized cultures of Plasmodium falciparum were grown in suspension for 22-32 hours. Intracellular growth was assayed by measuring cellular uptake and incorporation into protein of 35S-methionine. Low concentrations (2%) of serum from immune humans and Aotus monkeys were found to inhibit the uptake of the 35S-methionine. The amount of inhibition for a given serum was often inversely related to its indirect fluorescent antibody test titer. Inhibition occurred during the trophozoite stage and was not obtained with a clone lacking the erythrocyte modifications referred to as knobs. Thus, a sensitive new assay is described which allows detection of factors in immune primate sera which can affect maturation of P. falciparum within the erythrocyte. These serum factors are likely to be antibodies which react with antigens expressed at the trophozoite stage on the surface of K+-infected erythrocytes.

The Duffy Blood Group and Resistance to Plasmodium Vivax in Honduras *

To test the hypothesis that the Duffy blood group negative genotype is a factor in resistance to Plasmodium vivax, we determined the Duffy blood group, the malaria antibodies, and the slide-demonstrated infection rates with P. vivax and P. falciparum of 420 persons living in Nueva Armenia, Honduras. In all, 247 persons were Duffy negative. Demonstrated infections with P. falciparum were almost equally distributed between Duffy-positive (5,8%) and Duffy-negative (4.9%) persons. Similarly, Duffy-positive (25.6%) and Duffy-negative (28.2%) persons had equal proportions of indirect fluorescent antibody test titers suggestive of past or present P. falciparum infection. In contrast, all 14 P. vivax infections were found in Duffy-negative persons. There was no evidence suggesting that Duffy-positive and Duffy-negative persons had different exposures to malaria. The Duffy negative genotype FyFy appears to be a factor in resistance to P. vivax.

The effect of medication with metichlorpindol and methylbenzoquate on the development of antibodies as measured by the fluorescent antibody (IFA)_test against Eimeria tenella and Eimeria maxima

Abstract The development of antibodies as measured by the indirect fluorescent antibody (IFA)_ test was studied in groups of birds infected with Eimeria tenella or E. maxima and fed diets containing methylzoquate (MBQ) and/or meticlorpindol (MCP). The drugs suppressed both the E. tenella and E. maxima infections, the extent depending on the concentrations in the feed. The IFA test titres in both the E. tenella and E. maxima infections were related to the oocyst production. Effective suppression of the infection resulted in on or minimal IFA response. Since both drugs used inhibit the sporozoites, it is concluded that development of the parasite is necessary to stimulate the host to produce circulating fluorescent antibodies.