Toxoplasma Hemagglutination and Dye Test Antibodies in Experimentally Infected Rats

Abstract

Rats infected with different strains of Toxoplasma gondii showed different serological responses as measured by the Sabin-Feldman dye test and the hemagglutination test for toxoplasmosis. Hemagglutination antibodies appeared earlier and persisted longer in rats infected with the virulent RH strain toxoplasma than in rats infected with less virulent strains. The hemagglutination test for toxoplasmosis (Jacobs and Lunde, 1957) has given us such good results on human sera, correlating well with the dye test (Lunde and Jacobs, 1958), that we have recently adopted it as the procedure to be used in the diagnosis of routine specimens submitted to our laboratory. Some investigators have had equally good results (Knierim et al., 1960; Lewis and Kessel, 1961) while others have reported discrepancies. A discussion of their findings has been presented elsewhere (Lunde et al., 1963). In our hands, the hemagglutination (HA) test is an adequate tool for diagnosis of human toxoplasmosis. We have also explored its usefulness for serological study of the infection in animals, and the present paper reports some of our findings in rats. MATERIALS AND METHODS The procedure for the dye test was that described by Frenkel and Jacobs (1958). The hemagglutination test was performed as originally reported except for the following modifications: The tannic acid concentration was 1 : 80,000, and one volume of tanned erythrocytes was sensitized with one volume of antigen which had been previously diluted in pH 6.4 buffered saline to its optimal dilution. The optimal dilution is that giving the highest HA titer with known positive sera and complete absence of hemagglutination of sensitized cells with negative sera. The toxoplasma strains used were the wellknown RH; CH, isolated by Dr. H. R. Seibold, then of the U. S. Department of Agriculture, from a chinchilla; and our strain 113-CE (Jacobs and Received for publication 31 May 1963. * Laboratory of Parasitic Diseases. Melton, 1954). The LB strain, of human origin, was isolated in this laboratory in 1957 from an adult case of lymphadenitis and chorioretinitis (Kayhoe et al., 1957). The rats used were 200to 250-g specimens of the Osborne-Mendel or Sprague-Dawley strains, obtained from the Animal Production Section, NIH. Details of infections and bleedings will be more conveniently presented below. RESULTS AND DISCUSSION Ten rats were inoculated intraperitoneally with 10,000 RH strain T. gondii, and an additional ten rats with the same number of parasites of strain 113-CE. They were bled from the orbital sinus at various intervals after infection, and HA and dye tests were performed on the sera. The results are shown in Table I. The dye test became positive in 5 days in rats infected with both strains of the parasite, although it reached higher levels on days 5 and 9 in the RH-infected rats. Two weeks after infection the dye tests (DT) leveled off at approximately the same titers. Ten months postinfection the dye test titers of the 113-CE rats were somewhat lower than the RH rats. In the RH-infected rats the HA test became posi ive in 3 weeks while the sera of 113-CEinfected rats were not positive until 10 weeks after inoculation. After the appearance of HA titers they persisted for up to 9 months in the RH-infected animals but for little more than 1 month in the 113-CE-infected rats. Some of the latter never showed a positive HA test although the dye test was positive on the same serum specimens. Eleven months after these rats were infected, 932 This content downloaded from 157.55.39.35 on Thu, 01 Sep 2016 05:46:37 UTC All use subject to http://about.jstor.org/terms LUNDE AND JACOBS-TOXOPLASMA ANTIBODIES IV m ,iM o o0 o I0 0o O O QO CCO I C ecl cD c i0t0 tm1~43 C It>C, I)1fm In o o o LO -oM oqt Cq cl: in in ciO r) ci in~ 0 aS eci CiCO |ci 0 0 10 0 c ( ? m n > o oolooc0 o locim coi'^co i-D ^ t ! 000000 10 m01 N1 Ci 0 CM 0 0 0 o00 C CO CD 0 0 OC C OD C 't oCo C Tp CT 0 s> 0 OC]C Ci '? OS O(1?(1-C11 O 00 O0 -iV)O M n I0,00ocV)a))0~ o qci ci13 If 000000 0000 *^ *^ C1^ ^ ^' .t '^ i^ -IOIMOCM 000000r00 to Cr T IlIt Id d4 1 C CM CiM i C 05 0ooo 0 0o0 0^o 0000 01CO o o C C O CO CO0 0 0