Protective immunity against the protozoan Leishmania chagasi is induced by subclinical cutaneous infection with virulent but not avirulent organisms.

Avirulent Organisms Cutaneous Infection with Virulent But Not Is Induced by Subclinical Leishmania chagasi Protective Immunity Against the Protozoan

Antigenic Differences between Matt Hemolytic Streptococci and Their Glossy Variants

The matt and the glossy forms of four strains of hemolytic streptococci were used to immunize rabbits. Precipitin tests showed that rabbit sera prepared against matt organisms, whether virulent or avirulent for mice, contained type-specific antibody while sera prepared against completely degraded glossy organisms contained no type-specific antibody. Type-specific antibody was removed from the s...

An avirulent lipophosphoglycan-deficient Leishmania major clone induces CD4+ T cells which protect susceptible BALB/c mice against infection with virulent L. major.

An avirulent clone of Leishmania major was used to immunize susceptible BALB/c mice against challenge with virulent L. major. By using the immunized animals as a source of cells, CD4+ parasite-specific T-cell lines could be generated in vitro which, when adoptively transferred to naive BALB/c recipients, conferred marked protection against challenge with virulent L. major. Compared with CD4+ pa...

Acid phosphatase activity of virulent and avirulent clones of Leishmania donovani promastigotes.

Virulent and avirulent clones of Leishmania donovani promastigotes were examined for their acid phosphatase activity. The acid phosphatase activity of whole-cell lysates of virulent clones was 1.5 to 2.0 times higher than that of avirulent clones. Pellet fractions (260,000 x g, 30 min) from sonicated promastigotes of a virulent clone and an avirulent clone contained 60 and 40% of the total enzy...

Killed but metabolically active Leishmania infantum as a novel whole-cell vaccine for visceral leishmaniasis.

There are currently no effective vaccines for visceral leishmaniasis, the second most deadly parasitic infection in the world. Here, we describe a novel whole-cell vaccine approach using Leishmania infantum chagasi promastigotes treated with the psoralen compound amotosalen (S-59) and low doses of UV A radiation. This treatment generates permanent, covalent DNA cross-links within parasites and ...