Use of Sodium Polyanetholesulfonate-CaCl2 for Removal of Serum Nonspecific Inhibitors of Rubella Hemagglutination: Comparison with Other Polyanion-Divalent Cation Combinations

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By using trypsin-treated human type O cells as indicators, we compared the abilities of four polyanion-divalent cation combinations (heparin-MnCl2; high-and low-molecular-weight dextran sulfate-CaCl2; and sodium polyanetholesulfonate [SPS]-CaCl2) for removal of serum non-immunoglobulin (lipoprotein) inhibitors of rubella hemagglutination. The combination of SPS-CaCl2 was found to be the most effective, precipitating completely the pre-β and β-lipoproteins and reducing the α-lipoprotein levels by more than 50%. Hemagglutination patterns after this treatment were clear and stable, and, when normal sera were tested, hemagglutination-inhibition (HI) titers were comparable to those obtained after standard heparin-MnCl2 treatment. High-molecular-weight dextran sulfate-CaCl2 removed serum lipoproteins almost as effectively as SPS-CaCl2. However, problems of nonspecific agglutination and the heavy hemagglutination patterns resulting made this combination unacceptable for routine purposes. Neither low-molecular-weight dextran sulfate-CaCl2 nor heparin-MnCl2 removed the pre-β lipoproteins completely, and occasionally traces of β-lipoprotein also remained after treatment. The presence of pre-β lipoproteins in normal sera after treatment may be of no consequence in the HI test since we have found that the very-low-density lipoprotein fractions obtained by ultracentrifugal methods from normal sera (those corresponding to the pre-β fractions obtained by electrophoresis) had no HI activity. However, very-low-density lipoprotein fractions from all hyperlipemic sera tested had HI activity (titers ranging from 1:16 to 1:1,024) which, in the majority of cases, was not eliminated after heparin-MnCl2 treatment. In every case, treatment with SPS-CaCl2 removed this nonspecific activity completely. Since hyperlipemic sera may occasionally be encountered in routine rubella HI antibody testing, we recommend the use of SPS-CaCl2 rather than heparin-MnCl2 for pretreatment of sera.

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