The avirulence of the cultivated PF strain of Trypanosoma cruzi: V - the evaluation of parasitologic tests after vaccination of different animal species

1972

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Immunosuppression bp immunotolerance was obtained in mice by inoculat ing Trypanosoma cruzi avirulent PF strain in high doses to mice. Direct and indirect laboratory tests loere used to demoiistrate the above statements.Since our first works on avirulence of the T. cruzi PF strain we were surprised to find some vaccinated animals with po sitive blood cultures and only rarely with positive parasitemias (11,13, 14) .Although we couldn't define precisely the real nature of the fact, by then, we had already concluded th a t the observed parasites should be the same inoculated as vaccine. These trypanosomes did not in fect young mice.Among the various circumstances in which the fact happened, one specially called our attention -the relationship between it and the number of parasites inoculated as vaccine.For this reason we decided to verify if the phenomenon could be reproduced and explained as due to immunological tole rance. MATERIAL AND METHODSNinety three albino mice weighing lOg each were divided in three groups -the first group with 34 animals, the second one with 35 and the third with 25.The first group was vaccinated, subcutaneously, with 107 living trypanosomes of the PF strain from a culture 19 days old in Warren medium.The second group was vaccinated with 101 1 parasites just the same and by the same route.The third group was held as control. Eight and fifteen days after vaccination a peripheral blood search was performed for trypanosomes in the vaccinated mice On the fifteenth day, from each vac cinated group, 10 animals were selected at random and bled to death. From the lirst "* U S P . F a c u ld a d e d e M e d ic in a . R ib e irã o P r ê to . S . P a u lo . B ra s ii.

Section: Dicussion and Conclusionmentioning

confidence: 87%

Section: Direct and Indirect Laboratory Tests Loere Used To Demoiistrmentioning

confidence: 99%

“…

Immunosuppression bp immunotolerance was obtained in mice by inoculat ing Trypanosoma cruzi avirulent PF strain in high doses to mice.

Among the various circumstances in which the fact happened, one specially called our attention -the relationship between it and the number of parasites inoculated as vaccine.

For this reason we decided to verify if the phenomenon could be reproduced and explained as due to immunological tole rance.

MATERIAL AND METHODS

Ninety three albino mice weighing lOg each were divided in three groups -the first group with 34 animals, the second one with 35 and the third with 25.

The first group was vaccinated, subcutaneously, with 107 living trypanosomes of the PF strain from a culture 19 days old in Warren medium.

The second group was vaccinated with 101 1 parasites just the same and by the same route.

The third group was held as control.

…”

mentioning

confidence: 99%

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The avirulence of the cultivated P F strain of T. cruzi: VI. introduced immunotolerance in mice by a veryhigh inoculum

1972

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The vaccination of human beings with a live avirulent strain of Trypanosoma cruzi: a new series of volunteers

1973

F ive h u m a n v o lu n te e rs w ere v a c c in a te d w ith a live a v ir u le n t str a in o f T ryp a n o s o m a cru zi a n ã fo llo w e d -u p fo r one year. E x c e p t fo r a fe w cases o f q u e s tio nab le re su lts p re se n te d b y o n ly one L a b o ra to ry , ali th e o th e r clin ica i, p a ra sitological a n ã serological te s ts re m a in e d n e g a tiv e d u rin g th a t perioá.T h ro u g h se v e ra l e x p e rim e n ts (2-9) a n a v iru le n t s tr a i n of T ry p a n o so m a cru zi h a s b ee n s tu d ie d t h a t is su p p o se d to be a m ut a n t o f th e v iru le n t Y s tr a in , a n d fo r th is re a s o n n a m e d i t P F s tr a in (10).I n 1971 a p rev io u s n o te c o n c e rn in g th e fir s t tw o h u m a n b e in g s v a c c in a te d w ith su c h a v iru le n t try p a n o so m e w a s publis.hed (11). L a te r th e tw o -y e a r fo llo w -u p on th e sa m e v o lu n te e rs w as d e sc rib e d (12).I t w ill be p re s e n te d in th is p a p e r a few m o re a r g u m e n ts c o n firm in g th e n o n p ath o g e n ic ity of t h a t s tr a in , d e sc rib in g th e o n e -y e a r fo llo w -u p of a n ew se rie s of h u m a n b ein g s in je c te d w ith th e P F t r y p a n o so m e . M A TERIAL AND M ETHODSF ive a d u lt m a les, co n v icts a t th e P riso n of R ib eirão P re to , p re s e n te d th e m se lv es as v o lu n te e rs to be v a c c in a te d . A fte r th e leg al p ro ce d u re s, c lin ic a i a n d la b o ra to r ia l e x am in a tio n s o n th e five p a tie n ts w ere c a rrie d o u t.T h e c o m p le m e n t fix a tio n te s t (C F T ), th e im m u n o flu o re sc e n c e te s t (IF T ) a n d th e e le c tro c a rd io g ra m (ECG) w ere p e rfo rm e d b efo re th e v a c c in a tio n . Five d ay s la te r e a c h v o lu n te e r received by s u b c u ta n e o u s ro u te 0.2ml o f a su sp e nsio n of th e P F try p a n o so m e h a rv e s te d in W a rre n m é d iu m fo r 18 d a y s. T h e cu ltu re m e d iu m w as c e n trifu g e d a t 1.500 r.p.m . a n d th e s e d im e n t w a sh e d se v eral tim e s i.n salin e s o lu tio n . T h e f in a l su sp e n sio n h a d a lm o s t 75% of m obile p a r a s ite s w ith a to ta l o f 10° fla g e lla te s p e r m l w ith a b o u t 4% of m e ta c y c lic tr y p o m a s tig o te s . T h is sa m e v a c cin e w as in je c te d , su b c u ta n e o u sly in 15, 20 d a y -o ld m ic e. * A ssociate P ro fesso r, D e p a rta m e n to de G e n é tic a e M a te m á tic a A plicada à B iologia, F a c u ld a d e de M edi c in a . U S P . 14100 R ib e irã o P re to , E st. S . P au lo , B rasil. S u b m itte d to p u b lic a tio n o n 11.22.1972.

Trypanosoma cruzi: avirulence of the PF strain to Callithrix marmosets

1981

H u m b e rto M e n e ze s'* C a llith rix jacchus geoffroy marmosets (H um boldt 1812) were injected once subcutaneously with 10.000 parasites/g b o d y weight and follow ed for a period o f six months. The PF strain o f Trypanosoma cruzi was used. Follow -up was done through blood cultures, xenodiagnosis, serological tests, and E C G . A sm all num ber o f norm aI animais served as control. IN T R O D U C T IO NBlanchard1, Laveran6 , Brumpt2, Mayer and Rocha Lim a9, and recently, other investigators have reported that animais which survived a virulent infection with Trypanosoma cruzi became resistant to a subsequent challenge with this parasite.Different procedures have been utilized over the years by several investigators searching for protection against further virulent T. cruzi infections: injection of low-virulence parasites (Norman and Kagan22; Kagan and Norman5 ; Marr and Pike8 ; Seah and Marsden2 6); injection of killed parasites (Soltys28; Neal and John son21); of flagellate fractions (Segura, Cura, Paulone, Vasquez and Cerisola27); of mole cular fractions of cells from immunized hosts (Lemos and Menezes7); and of subcellular fractions of related parasites (Grymberg, NeriGuimarães, Castro and Oliveira Lim a4 ).Injection of low-virulence parasites (Pizzi and Prager24) or of a virulent strain, immediately followed by treatment (P izzi25) seems to be the most effective technique so far employed to obtain efficient protection. These observations have been confirmed by immunological techniques, which demonstrate that the infected animais develop antibodies and immunologically competent cells against the flagellates. A problem posed by this technique is the danger of infection with the low-virulence protozoa, which, although low virulent, coulci induce patent parasitemia in the injected ani mais. An additional problem is the mandatory treatment of ali animais injeted with a virulent strain.Injection of parasitic fractions or other molecular derivatives of the infected animais opens a promissing new field in trypanosomiasis research, but will not be discussed here. My discussion will be limited ío the avirulence of a strain of T. cruzi i.e. a trypanosoma unable to induce disease or parasitemia, or to produce positive serological tests when injected in a suitabie dose and by an adequate route. In 1968, I described such a parasite (Menezes10) as a probable misture of mutants of the y strain, reported by Pereira da Silva an Nussenzweig23 (as being highly virulent to mice. In a In 1970 (Menezes12), I described the first examples of animais injected with a very high dose of parasites which, although they presented positive blood cultures, gave negative results when inoculated into baby mice in culture form. The study presented here was carried out on C a llith rix jacchus g e o ffro y marmosets, and concerns the tests performed before vaccination and throughout the six month period following injection of the avirulent strain. M A T E R IA L S A N D M ETHO D S AnimaisSixteen C a llith rix jacchus g e o ffro y m ...