The acidic ribosomal proteins of the protozoan parasites have been described as prominent antigens during human disease. We present here data showing the molecular cloning and protective efficacy of P1 gene of Leishmania donovani as DNA vaccine. The PCR amplified complete ORF cloned in either pQE or pVAX vector was used either as peptide or DNA vaccine against experimentally induced visceral leishmaniasis in hamsters. The recombinant protein rLdP1 was given along with Freund's adjuvant and the plasmid DNA vaccine, pVAX-P1 was used alone either as single dose or double dose (prime and boost) in different groups of hamsters which were subsequently challenged with a virulent dose of 1×10(7) L. donovani (MHOM/IN/DD8/1968 strain) promastigotes by intra-cardiac route. While the recombinant protein rLdP1 or DNA vaccine pVAX-P1 in single dose format were not found to be protective, DNA vaccine in a prime-boost mode was able to induce protection with reduced mortality, a significant (75.68%) decrease in splenic parasite burden and increased expression of Th1 type cytokines in immunized hamsters. Histopathology of livers and spleens from these animals showed formation of mature granulomas with compact arrangement of lymphocytes and histiocytes, indicating its protective potential as vaccine candidate.
"We evaluated the impact of parasite load in two compartments (spleen and liver) after infection by L. infantum strains. The development of molecular approaches to quantify the parasite load in the spleen and liver from experimentally infected hamsters is extremely relevant because this animal model has been used to evaluated potential drugs and candidate vaccines against VL , , , , , , , , . The LDU index, as described by Stauber , has the disadvantage of low sensitivity for detecting amastigotes by optical microscopy. "
[Show abstract][Hide abstract] ABSTRACT: To develop and test new therapeutics and immune prophylaxis strategies for visceral leishmaniasis (VL), understanding tissue parasitism evolution after experimental infection with Leishmania infantum is important. Experimental infection in a hamster model (Mesocricetus auratus) reproduces several typical aspects of canine and human VL that are closely related to the inoculum's route. We quantified the parasitism in the liver and spleen of hamsters experimentally infected by various routes (intradermal, intraperitoneal, and intracardiac [IC]) and different strains of L. infantum (MHOM/BR/74/PP75 and Wild) and compared two different methodologies to evaluate tissue parasitism (Leishman Donovan units [LDU] and real-time qPCR). In addition, the quantification of specific total-IgG in the serum of uninfected and infected hamsters was determined by ELISA. The animals were followed for 1, 3, 6 and 9 months post-infection for survival analysis. We found that infection with the Wild strain by the IC route resulted in higher mortality. Positive antibody (IgG) responses were detected with higher peaks at 6 and 9 months in the IC group inoculated with PP75 strain. However, in animals infected with the Wild strain the IgG levels were elevated in all infected groups during all the time evaluated. We also observed by LDU analysis that the IC route lead to higher parasitism in the liver and spleen with both strains. Furthermore, qPCR showed higher sensitivity for identifying animals with low parasitic burden. In conclusion, qPCR can be useful for assessing parasitism in the spleen and liver of a hamster model infected with L. infantum independent of the route of infection, and this technique may become an essential tool for assessing parasite density in the hamster model after experimental treatment or immunization with potential vaccine candidates.
PLoS ONE 10/2012; 7(10):e47907. DOI:10.1371/journal.pone.0047907 · 3.23 Impact Factor
"In addition, DNA vaccines mimic the protective effects of live vaccines without the potential danger of disease development, they are relatively easy and cheap to produce and unlike protein or live-attenuated vaccines , does not require the maintenance of " cold chain " sequence (Gurunathan et al., 2000b). Several experimental studies have shown that DNA vaccines confer strong protection against cutaneous (Doroud et al., 2011a,b) and visceral (Fragaki et al., 2001; Tewary et al., 2004; Saldarriaga et al., 2006; Masih et al., 2011; Mazumder et al., 2011) leishmaniases. However, although DNA vaccination is considered a promising technology, it still remains an experimental practice because no development of such vaccines for use in humans has been reported so far. "
[Show abstract][Hide abstract] ABSTRACT: Although a great deal of knowledge has been gained from studies on the immunobiology of leishmaniasis, there is still no universally acceptable, safe, and effective vaccine against the disease. This strongly suggests that we still do not completely understand the factors that control and/or regulate the development and sustenance of anti-Leishmania immunity, particularly those associated with secondary (memory) immunity. Such an understanding is critically important for designing safe, effective, and universally acceptable vaccine against the disease. Here we review the literature on the correlate of protective anti-Leishmania immunity and vaccination strategies against leishmaniasis with a bias emphasis on experimental cutaneous leishmaniasis.
Frontiers in Immunology 05/2012; 3:128. DOI:10.3389/fimmu.2012.00128
"An interesting prophylactic measure to limit the epidemiology of leishmaniasis is the development of vaccines. The immunogens used to formulate vaccine candidates can be classified according to their method of formulation: live parasites, the classic model of leishmanization ; first generation vaccines that use crude parasite antigens [8,9]; second generation vaccines that use fractionated, purified or recombinant antigens ; and third generation vaccines that use genetic material as the immunogen . "
[Show abstract][Hide abstract] ABSTRACT: Leishmania (Viannia) shawi parasite was first characterized in 1989. Recently the protective effects of soluble leishmanial antigen (SLA) from L. (V.) shawi promastigotes were demonstrated using BALB/c mice, the susceptibility model for this parasite. In order to identify protective fractions, SLA was fractionated by reverse phase HPLC and five antigenic fractions were obtained.
F1 fraction was purified from L. (V.) shawi parasite extract by reverse phase HPLC. BALB/c mice were immunized once a week for two consecutive weeks by subcutaneous routes in the rump, using 25 μg of F1. After 1 and 16 weeks of last immunization, groups were challenged in the footpad with L. (V.) shawi promastigotes. After 2 months, those same mice were sacrificed and parasite burden, cellular and humoral immune responses were evaluated.
The F1 fraction induced a high degree of protection associated with an increase in IFN-γ, a decrease in IL-4, increased cell proliferation and activation of CD8+T lymphocytes. Long-term protection was acquired in F1-immunized mice, associated with increased CD4+ central memory T lymphocytes and activation of both CD4+ and CD8+ T cells. In addition, F1-immunized groups showed an increase in IgG2a levels.
The inductor capability of antigens to generate memory lymphocytes that can proliferate and secrete beneficial cytokines upon infection could be an important factor in the development of vaccine candidates against American Tegumentary Leishmaniasis.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.