Therapeutic immunization with radio-attenuated Leishmania parasites through i.m. route revealed protection against the experimental murine visceral leishmaniasis.

After our promising results from prophylactic and therapeutic study (i.p. route) with the radio-attenuated Leishmania donovani parasites against experimental murine visceral leishmaniasis, we prompted to check their therapeutic efficacy through i.m route. BALB/c mice were infected with highly virulent L. donovani parasites. After 75 days, mice were treated with gamma (γ)-irradiated parasites. A second therapeutic immunization was given after 15 days of first immunization. The protection against kala-azar was estimated with the reduction of Leishman-Donovan unit from spleen and liver that scored up to 80% and 93%, respectively, while a twofold increase in nitric oxide (NO) and reactive oxygen species (ROS) productions has been observed in the immunized groups of animals. These groups of mice also showed disease regression by skewing Th2 cytokines (IL-10) towards Th1 cytokine (IFN-γ) bias along with the increased generation of NO and ROS, while the infected control group of mice without such treatment surrendered to the disease. Establishment of Th1 ambience in the treated groups has also been supported from the measured antileishmanial antibody IgG subsets (IgG2a and IgG1) with higher anti-soluble Leishmania antigen-specific IgG2a titer. As seen in our previous studies, doses of attenuation by γ-radiation should be taken into serious consideration. Attenuation of parasites at 50 Gy of absorbed dose of gamma rays has not worked well. Thus, therapeutic use of L. donovani parasites radio-attenuated at particular doses can be exploited as a promising vaccine agent. Absence of any adjuvant may increase its acceptability as vaccine candidate further.

Atomic force microscopic studies on erythrocytes from an evolutionary perspective.

We examined atomic force microscopy (AFM) and lateral force microscopy (LFM) images of human, avian, reptilian, amphibian, and piscine erythrocytes to determine whether the general pattern of erythrocyte membrane architecture has been largely conserved in the course of phylogenetic evolution or relatively minor modifications have taken place. The general pattern of the cell surface structure is indeed very similar among the phyla examined. The surface features include a number of blebs or globular structures and hole-like depressions. Such features are particularly clear in fish (Heteropneustes sp.), in which globular blebs are arranged in tiers around the depressions. The same pattern is found in the other phyla, although the sizes of the blebs and depressions vary. The depressions are approximately 340 and approximately 100 nm in diameter in chickens and fish, respectively, and are smaller in other phyla. The images of human erythrocytes presented here show holes more clearly than the images obtained by Zhang et al. (Scanning Electron Microsc., 1995; 9:981-989), who showed for the first time the highly uneven surface of these cells. The globules range in size from approximately 50-150 nm in diameter. These nanostructures have a width of approximately 333-1,000 atoms, assuming that the average dimension of an atom is 1.5 A. The size range of the holes is approximately 40-432 nm (equivalent to a width of approximately 266-2880 atoms). LFM images, which take into account the lateral component of the force, represent the variation of surface friction (roughness) on the erythrocyte surface. This is very clear in the toad images, which show well-ordered strata that have not been revealed in ordinary AFM images.