Enhanced efficacy and immunogenicity of 78kDa antigen formulated in various adjuvants against murine visceral leishmaniasis.

Leishmania infection causes localized cutaneous to severe visceral disease in humans and animals. Current control measures, based on antimonial compounds, are not effective because of resistance in Leishmania. Vaccination would be a feasible alternative, but as yet no vaccine to protect humans against infection has been commercialized. Parasite antigens that preferentially stimulate the induction of significant protection through Th1 response presents a rational approach for a vaccine against leishmaniasis. With this view in mind, we investigated the potential of 78kDa antigen of Leishmania donovani alone and along with different adjuvants against murine visceral leishmaniasis. Various adjuvants used along with 78kDa antigen include monophosphoryl lipid A (MPL-A), liposomal encapsulation, recombinant IL-12, autoclaved Leishmania antigen (ALD) and Freund's adjuvant (FCA). BALB/c mice were immunized subcutaneously thrice with respective vaccine formulation. Challenge infection was given intracardially after 2 weeks of second booster. A significant decrease in parasite burden was seen in vaccinees over the infected controls on all post challenge days and was found that maximum protection was provided by 78kDa+rIL-12 vaccine and it was highly immunogenic as depicted by the reduction in parasite load (71-94.8%), reduction in infection rate of peritoneal macrophages (92.9-98%), enhanced DTH response (6.5-10.5 fold), increase in IgG2a anti-leishmanial antibody production (3-3.7 fold) and up-regulation of IFN-gamma (3.7-6.5 fold) and IL-2 levels (7.7-12.3 fold), which demonstrate the generation of protective Th1 type of immune response. Comparable results were also observed in 78kDa+MPL-A and liposome-encapsulated 78kDa vaccines with 56.5-92% and 62.9-93.4% reduction in parasite load respectively. Significant results have also been obtained with 78kDa antigen+ALD, 78kDa antigen+FCA and 78kDa antigen alone group but the protective efficacy was reduced as compared to the other vaccine groups. The present study indicates that the three vaccine formulations i.e. 78kDa antigen+rIL-12, liposome-encapsulated 78kDa antigen and 78kDa antigen+MPL-A, are highly efficacious and effective vaccine candidates against visceral leishmaniasis.

Nagill R ，Kaur S 《-》

Evaluation of the immunoprophylactic potential of a killed vaccine candidate in combination with different adjuvants against murine visceral leishmaniasis.

Despite a large number of field trials, till date no prophylactic antileishmanial vaccine exists for human use. Killed antigen formulations offer the advantage of being safe but they have limited immunogenicity. Recent research has documented that efforts to develop effective Leishmania vaccine have been limited due to the lack of an appropriate adjuvant. Addition of adjuvants to vaccines boosts and directs the immunogenicity of antigens. So, the present study was done to evaluate the effectiveness of four adjuvants i.e. alum, saponin, cationic liposomes and monophosphoryl lipid-A in combination with Autoclaved Leishmania donovani (ALD) antigen against murine visceral leishmaniasis (VL). BALB/c mice were immunized thrice with respective vaccine formulation. Two weeks after last booster, challenge infection was given. Mice were sacrificed 15 days after last immunization and on 30, 60 and 90 post infection/challenge days. A considerable protective efficacy was shown by all vaccine formulations. It was evident from significant reduction in parasite load, profound delayed type hypersensitivity responses (DTH), increased IgG2a titres and high levels of Th1 cytokines (IFN-γ, IL-12) as compared to the infected controls. However, level of protection varied with the type of adjuvant used. Maximum protection was achieved with the use of liposome encapsulated ALD antigen and it was closely followed by group immunized with ALD+MPL-A. Significant results were also obtained with ALD+saponin, ALD+alum and ALD antigen (alone) but the protective efficacy was reduced as compared to other immunized groups. The present study reveals greater efficacy of two vaccine formulations i.e. ALD+liposome and ALD+MPL-A against murine VL.

Thakur A ，Kaur H ，Kaur S 《-》

Studies on the protective efficacy and immunogenicity of Hsp70 and Hsp83 based vaccine formulations in Leishmania donovani infected BALB/c mice.

Visceral leishmaniasis, a chronic systemic infection, is the major cause of morbidity and mortality in many parts of world. The current drugs for the treatment of leishmaniasis are toxic, expensive, difficult to administer and becoming ineffective due to the emergence of drug resistance. In the absence of effective treatment, vaccination remains the only hope for control of the disease. We have evaluated the protective efficacy of two heat shock proteins (Hsp70 and Hsp83) in combination with two different adjuvants (MPLA and ALD) in Leishmania donovani infected inbred BALB/c mice. The proteins were isolated by SDS-PAGE and the mice were immunized subcutaneously with Hsp70+Hsp83, Hsp70+Hsp83+ALD and Hsp70+Hsp83+MPLA. These were challenged with 10(7) promastigotes of L. donovani. The animals were sacrificed on 30, 60 and 90 days post challenge for the assessment of parasite load and generation of cellular and humoral immune responses. The vaccines induced a strong protective response against experimental visceral leishmaniasis as shown by reduced parasite load in liver of all immunized groups as compared to the infected controls. The vaccines also led to the augmentation of DTH responses, increased levels of IgG2a, IFN-γ and IL-2. Both the adjuvants raised significantly the level of protection imparted by the proteins but MPLA was more effective in comparison to ALD.

Kaur J ，Kaur T ，Kaur S 《-》

Induction of cellular and humoral responses by autoclaved and heat-killed antigen of Leishmania donovani in experimental visceral leishmaniasis.

Nagill R ，Mahajan R ，Sharma M ，Kaur S ... -  《-》

A mixed Th1/Th2 response elicited by a liposomal formulation of Leishmania vaccine instructs Th1 responses and resistance to Leishmania donovani in susceptible BALB/c mice.

Mazumdar T ，Anam K ，Ali N 《VACCINE》