SOME IMMUNOLOGICAL REACTIONS OF TRIPANOSONA GAMBIESSE ISOLATES

Abstract

Serological characteristics and the protective effect of humeral antibodies (serum) were examined in rabbits (a) infected with Trypanosoma gambiense, (b) immunized with killed Trypanosoma gambiense, (c) immunized with complete Freund’s adjuvant incorporated Trypanosoma gambiense. A few experiments using infected and immunized maker were also carried out. It was observed that parasite agglutinating antibody appers in infected rabbits before seven days after infection rising to its highest peak on the 28th day, thereafter a decrease in agglutination titro is marked. There seen to be a slight delay in the appearance of detectable parasite agglutinating antibody in rabbits immunized with Trypanosomes incorporated complete Freund’s adjuvant, trypanosomes incorporated incomplete Freund's adjuvant as well as Trypanosomes killed by freezing and thawing. Rabbits immunized with trypanosomes incorporated with complete Freund’s adjuvant gave a somewhat lower titre of parasite agglutinating antibody during the period of experimentation; however, the titre in all cases reached its maximum peak around the 28th day. In all cases there appears to be two peaks in the increasing level of the heterophile antibody titro, with the first peck appearing on the 14th day and a second park evident on the 35th day. Infected rabbits show a markedly higher titro of heterophile antibody than remaining groups. The increasing levels of globulins seem to confirm the increasing synthesis of synthesis of gamma globulin during the course of infection as well as immunization. However, this increase of Globulin levels is not directly related to the level of agglutinating, heterophile as well as protective antibody titros. There is definite protective effect conferred in mice through the humeral transfer of antibodies starting from the 2Ist day and reaching its peak around the 28th day, thereafter shows a decreasing value. There is no direct relationship between parasite agglutinating antibody titro of serum and the protective effect of such serum. It was observed that sera from very early response (14 days or less) with high aglutination titre have no protective affect. Though sera from the peak agglutination response conferred better protection oven after dilution, yet sera collected 35 days after immunization or infection possessing lower agglutination response have marked protective effect. Direct agglutination test using virulent Trypanosoma gambiense reveal in monkey infections that once the animal survives the first infection, the surviving animal shows long lasting immunity against re-infection. In an immuned animal there is generally a high level of parasites agglutinating antibody, which is mainly 195, and which possesses neutralizing effect. Serum from immuned animal is protective against infection to normal animals (rats and mice in particular). The agglutinating antibody in not strain specific and therefore shows cross reactivity with at least one other strain from different geographical area. The agglutination reaction is non-lytic and irreversible. The agglutinating reaction is specifically directed against the organisms and not the host red blood cells. Immobilization of the parasites does not seem to occur in the presence of antiserum prepared against the parasites. The known antigenic variation does not seem to occur with regard to the antigenic factor(s) responsible for the stimulation of the production of agglutinating antibody. Pregnancy in an immuned Rhesus monkey appears to decrease the protective effect of anti-serum obtained from such monkey but does not affect the agglutination titre in Trpanosoma Gambiense Serological observation indicated that antibodies produced in rabbits against Trpanosoma Gambiense did not protect Mice against experimental infection with Trpanosoma brucei. After six months storage at 10° c a drop in the agglutination titre of rabbit anti-sera to Trpanosoma Gambiense, was observed. The drop in agglutination titre was very significant particularly in the case of sera from rabbits immunized with Trypanosomes in incomplete Fround’s adjuvant. However, the protective effects of these antisera did not seem to have been affected by storage. Macroglobulins fractionated with sophadex G. 200 gave some protection to mice passively immunized with such fractions. The degree of protection seem to be the same irrespective of the mode of immunization. However, the fractions containing 75 immunoglobulins mainly gave similar marked proctection to mice passively immunized with antisera from rabbits immunized with trypanomes in complete Fround’s adjuvant as well as mice passively immunized with antisera from rabbits immunized with trypanosomes in incomplete Fround’s adjuvant, at the same time, 75 immuglobulin fractions of sera from rabbits infected with live trypanosomes completely protected all iv

MSerog,obulins frc.ctionsted with sephadex C. gavo pc= protoctiat to nico passively irmlimizod with such frnctions. The do c7= of protection seem to be tho oa=o irrespective of the =do of ir-uni..etion. 2ouover, Cul fractions containing 7S 1.2=noglobulins nninly gsvc sinner carked protection to nico passively inrunizod 4th antisorn fron rabbits iLvunizad with tripanasones in Con Zeta Froundls adjuvemt o well as nice passively innunized with antisora Iron rabbits inrunicc4 with trypanoemos in Incoupinto Froundls adjuvant, at the eano tine, 7S iumnoglobtain frlotiono of Dora Iron rabbits infected with live tryprutosonco conplotoly rirritcetod all tho nice pansivoly innunized 4th such 1'1-notions, The earlier findinco nhov nazi:0d protective offoct of antieorn fron infected group of rabbits oven when ouch sera wore diluted at rkn moll as 1/32, for this =anon the protoctivo offocto of the norm fractions wore retested after la dilution. It wro obsorvod that tho nacroglobulin fractions in thoso groups tested, lost V