Die Präcipitinreaktion des Tabakmosaikvirus mit Kaninchen- und Schweineantiserum

Abstract

When a definite amt. of an antiserum is treated with increasing amts. of the homologous antigen, there is an increase in the amt. of antibody in the precipitate as long as the antibody is present in excess. Tobacco mosaic (T.M.) virus differs from globular proteins in the rod-shape and size of its particles. Rabbit antibodies have a mol. wt. of 160,000 and pig antibodies, 930,000. A 5-month-old pig is injd. subcut. with 520 mg T.M. virus in 5 wks. in 5 doses. 10 days after the last injn., sterile blood is obtained by heart puncture and the serum stored at 0[degree]. A rabbit is injd. with 130 mg T.M. in 7 wks. in 5 doses. 5 mos. later, the rabbit is given 2 30-mg doses of the virus in 1 wk. 10 days after the last injn., blood is taken from the ear vein and the serum stored at 0[degree]. To 1 ml of the serum in a centrifuge tube are added varying amts. of T.M. virus and the vol. made up to 4 ml with 0.9% NaCl. After 36 hrs. at 0[degree], the tube is centrifugalized, the precipitate washed with NaCl soln., dissolved in a few drops of N NaOH and N detd. by the micro-Kjeldahl method. The antibody N is obtained by subtracting the added T.M. virus N from the total precipitate N. When pig antiserum is used, if the antibody is present in great excess, 55 mols. of pig antibody are bound to one T.M. virus mol., and in the equivalence zone, 28 mols. The corresponding values for the smaller rabbit antibodies are 600 and 300 mols. From the known dimensions of the T.M. virus and of the antibodies, it is calculated that when the antibodies are present in great excess, they completely cover the virus mol. The number of antibodies bound to the virus does not depend upon reactive positions on the virus mol. The thickening of the virus mol. due to the addition of the large pig antibodies can be detected by the electron microscope.