Avivah Zuckerman

Current status of the immunology of blood and tissue protozoa. I. Leishmania

Abstract This study reviews recent (1969–1973) advances in our knowledge of the immunology of cutaneous, mucocutaneous, and visceral leishmaniasis, with special emphasis on immunodiagnosis, on host (human and animal analog) reactions to leishmania, on new approaches to the molecular taxonomy of leishmania, and on the seroepidemiology of leishmanial disease.

Current status of the immunology of blood and tissue protozoa

Abstract Literature dealing with the immunology and immunopathology of infections with Plasmodium spp. in avian, rodent, and primate hosts is reviewed for the period between 1969 and 1974. A considerable amount of current work is with three of the chief target organs in the immunopathology of malaria, namely the erythron, the spleen, and the kidney. Serodiagnosis was developed as an epidemiological tool during this period. Work has focused also on the relapse problem, particularly in conjunction with the emergence of antigenic variants in response to the production of nonsterilizing amounts of anti-plasmodial antibody. Antigenic analysis of plasmodia, actively studied during the review period, is still fragmentary and incomplete. In particular, protection-inducing antigens still need to be isolated and characterized. Progress has been made in attempts at vaccination against various plasmodial stages but, although promising, advances are still rudimentary. Humoral and cell-mediated contributions to the development of functional protection against malaria have been studied. Antibody alone can neutralize small plasmodial inocula both in vitro and in vivo, and the merozoite is suspected as the stage vulnerable to this neutralization. While humoral protection is therefore not in doubt, it is widely believed that cell-mediated reactions fortify the humoral response via a helper-cell function. However, a total consensus on this view has not yet been reached.

Dissemination of leishmanias to the organs of Syrian hamsters following intrasplenic inoculation of promastigotes

Abstract Four strains of leishmanial promastigotes were inoculated intrasplenically into male Syrian hamsters ( Mesocricetus auratus ). The dissemination of the parasites as amastigotes to various organs was followed at closely spaced intervals for 3.5 mo. An Israeli strain of Leishmania tropica and a strain isolated in Israel from a gerbil ( Meriones shawi ) displayed practically identical distribution patterns. Migration was outward from the spleen to the body surface, where intense multiplication of the amastigotes occurred, primarily in the ear pinnae and in the extremities of the limbs. A cryptic visceral infection persisted in the spleen, and most of the internal organs studied also developed cryptic infections. The bone marrow became rather heavily infected, and the epididymis, exceptionally heavily infected. An Indian strain of L. donovani led to a severe visceral infection in the spleen, liver, and bone marrow; and to mild to cryptic infections in most of the other visceral organs studied. However, no invasion of the genitalia occurred, nor did the body surface become infected. An Ethiopian strain of diffuse cutaneous leishmaniasis (DCL) was noninfective to Syrian hamsters, following either the intrasplenic or the intradermal inoculation of promastigotes.

Antigenic Structure of Plasmodium vinckei

An erythrocyte-free preparation of the erythrocytic stages of Plasmodium vinckei was made from infected mouse blood and disintegrated in a Hughes press. Rabbit antisera yielded a series of precipitation arcs against plasmodial extract when examined by immunoelectrophoresis. No arcs developed when uninfected mouse erythrocytes or stromata were tested against the same antiserum.

Current status of the immunology of blood and tissue protozoa. II. Plasmodium.

Abstract Literature dealing with the immunology and immunopathology of infections with Plasmodium spp. in avian, rodent, and primate hosts is reviewed for the period between 1969 and 1974. A considerable amount of current work is with three of the chief target organs in the immunopathology of malaria, namely the erythron, the spleen, and the kidney. Serodiagnosis was developed as an epidemiological tool during this period. Work has focused also on the relapse problem, particularly in conjunction with the emergence of antigenic variants in response to the production of nonsterilizing amounts of anti-plasmodial antibody. Antigenic analysis of plasmodia, actively studied during the review period, is still fragmentary and incomplete. In particular, protection-inducing antigens still need to be isolated and characterized. Progress has been made in attempts at vaccination against various plasmodial stages but, although promising, advances are still rudimentary. Humoral and cell-mediated contributions to the development of functional protection against malaria have been studied. Antibody alone can neutralize small plasmodial inocula both in vitro and in vivo, and the merozoite is suspected as the stage vulnerable to this neutralization. While humoral protection is therefore not in doubt, it is widely believed that cell-mediated reactions fortify the humoral response via a helper-cell function. However, a total consensus on this view has not yet been reached.

Active immunization of rats with a cell-free extract of the erythrocytic parasites of Plasmodium berghei.

Abstract Weanling rats were vaccinated with a nonliving product prepared by grinding erythrocytic forms of Plasmodium berghei , liberated from their red-cell hosts by treatment with saponin. Vaccinated and control rats were then exposed to viable P. berghei . Infections in vaccinated rats were milder than in controls in that the prepatent period was lengthened, the patent period was curtailed, the peak parasitemias and cumulative parasite counts were reduced, and the mortality rates fell. The relation of these results to the vaccination of other hosts to their homologous plasmodia is discussed.

Antiplasmodial precipitins demonstrated by double diffusion in agar gel in the serum of rats infected with Plasmodium berghei

Abstract Among single serum samples collected from 111 rats during primary infection with Plasmodium berghei , 61 (55%) contained precipitin. Twenty-one were positive before parasitemia crisis, and 40 after crisis. There were fewer positives among the serums of younger rats than in mature rats. A series of 8 hyperimmunizations raised the percentage of positive tests from 55 to 75%. Vaccination with a cell-free plasmodial product before challenge with viable parasites raised the percentage of positive tests to 100%. The kinetics of production of precipitin was studied in a series of closely spaced observations on 46 infected rats throughout infection and into latency. In all but one rat with a fulminating fatal infection, precipitin appeared in the serum some days after inoculation, and remained demonstrable for extended periods, with occasional negative observations. Precipitin was regularly observed during latency. The precipitin was antiplasmodial, and no antierythrocytic precipitin was demonstrated. Furthermore, the species-specificity of at least part of the precipitin was attested by the fact that absorption with a cell-free extract of Plasmodium vinckei failed to remove all of the precipitin from anti berghei rat serum; whereas absorption with a similar preparation of P. berghei removed it all.

PROPAGATION OF PARASITIC PROTOZOA IN TISSUE CULTURE AND AVIAN EMBRYOS

The general area to be discussed in the present review has recently been covered by Pipkin and Jensen (1958) and by Pipkin (1960) for the plasmodia and for protozoa other than the plasmodia, respectively. They anticipated the extension of knowledge in this sector along several promising lines, namely, in phase contrast microscopy of monolayer cultures with the aid of time lapse cinematography; in the electron microscopy of protozoa in tissue culture; in the study of the nutritional requirements of protozoa with the aid of defined media; and in the study of the biology of protozoa with the aid of perfusion chambers and of other techniques. Since their reviews, research along established lines has advanced steadily. In addition, many of the projected new lines of study, as well as others in the same field, have actually been initiated and actively carried forward. These facts perhaps justify another review of the field within less than a decade. Only material not discussed in the Pipkin reviews will be dealt with in the present study. Bibliographical information on earlier ideas referred to here as general background is to be found in the Pipkin reviews.

Standardization and quality control of Leishmania tropica vaccine

Abstract The production and properties of Leishmania tropica vaccine have been described. It has been pointed out that the use of this vaccine is not without inherent hazards and great care should be taken in its preparation. A set of requirements for the production and testing of the vaccine based on those of the Ministry of Health in Israel and the U.S. Department of Health is suggested.

Plasmodium berghei: precipitins in rats infected with attenuated strain, made hyperimmune to virulent strain, or vaccinated with extract of virulent strain.

Abstract A virulent strain of Plasmodium berghei was passaged alternately through rats and tissue culture. The strain retained its virulence for rats and mice through the third serial passage through tissue culture. Peak parasitemias in rats were somewhat lower after the fourth passage through tissue culture and parasites were attenuated for rats, but not for mice, after the fifth passage. Attenuation for rats was complete after the sixth passage while mice receiving an inoculum of the same material developed infections comparable to those in control mice inoculated with the parent stain passaged only through mice and not through culture. A precipitin appeared in the sera of rats inoculated with the attenuated strain. On double diffusion in gel this precipitin gave a reaction of identity with one of those observed in the serum of rats hyperimmune to the parent strain of plasmodium. No precipitins were observed in rats inoculated with tissue culture strains before attenuation became apparent.