Figure 3. PRRSV infection of porcine alveolar macrophages and porcine alveolar macrophage recognition of human erythrocytes share two common inhibitors: human erythrocyte glycoproteins (hEGP) and an anti-porcine sialoadhesin monoclonal antibody (pSn mAb).

A. At a range of 500 to 0 µg/ml, hEGP was tested as a potential inhibitor of PRRSV infection of porcine alveolar macrophages. Inhibition was measured using immunofluorescence. Viral antigen-positive cells and total cells were counted with an Olympus light microscope and the percentage of infected cells calculated. Three microscope fields and a minimum of 100 cells per field were counted for each experimental condition. B–D. Potential inhibitors were evaluated using the ⁵¹Chromium rosetting assay. Samples were prepared in triplicate. Data is representative of three independent experiments.. The means are shown. The standard error is calculated; however, for some samples it is very small and obscured by the bar. Human and porcine erythrocytes in the absence of a potential inhibitor served as positive and negative controls (gray bars). B. hEGP was tested as a potential inhibitor of alveolar macrophage recognition of human erythrocytes at a range from 500 to 7.8 µg/ml. hEGP was prepared in RPMI medium. The negative control used in this experiment was pEGP, porcine erythrocyte glycoproteins. C. Inhibition of porcine alveolar macrophage recognition of human erythrocytes by pSn mAb was tested. A serial dilution of the pSn mAb ranging from 1:10 – 1:10,000 was prepared in RPMI medium and incubated with porcine alveolar macrophages. Mouse IgG was used as an isotype control. D. Inhibition of Kupffer cell recognition of human erythrocytes by pSn mAb was tested. pSn mAb was incubated with porcine Kupffer cells at a range of dilutions from 1:10 to 1:10,000. Mouse IgG was used as an isotype control.