Correlation of TB activity with antibody titer using anti-Pfs25 sera from rabbits and anti-Pvs25 sera from rhesus monkeys. Rabbits were immunized with Pfs25 and the antisera were tested in mosquito membrane feeding assays with P. falciparum parasites and A. stephensi mosquitoes as described in legend to Figure 3. Rhesus monkeys were immunized with Pvs25 as described in legend to Figure 5 and the antiserum was diluted with a pool of normal human AB+ serum as 1:2 or 1:8 dilutions. The diluted monkey sera were tested in membrane feeding assays using parasites derived from vivax-infected patients in Thailand and A. dirus mosquitoes. Antibody units in the sera were determined by standardized ELISA. (a): Rabbit data (open circles) and individual monkey data (closed circles) are shown. There is a significant correlation between antibody units and % inhibition of oocyst density per mosquito in rabbit and in monkey sera (the Spearman Rank Correlations are 0.934 and 0.616, respectively). Lines represent regression of monkey result by use of a hyperbolic equation. Four points of rabbit data, which showed more than 30,000 antibody units and 100% inhibition of oocysts, are not shown in this figure. (b):The values of the test sera were grouped as shown. Average percent oocyst inhibition for rabbit sera (blank bars) or monkey sera (hatched bars) in each ELISA range + SD are shown.