title: Live Attenuated Leishmania donovani Centrin Knock Out Parasites Generate Non-inferior Protective Immune Response in Aged Mice against Visceral Leishmaniasis.
abstract: Visceral leishmaniasis (VL) caused by the protozoan parasite Leishmania donovani causes severe disease. Age appears to be critical in determining the clinical outcome of VL and at present there is no effective vaccine available against VL for any age group. Previously, we showed that genetically modified live attenuated L. donovani parasites (LdCen-/-) induced a strong protective innate and adaptive immune response in young mice. In this study we analyzed LdCen-/- parasite mediated modulation of innate and adaptive immune response in aged mice (18 months) and compared to young (2 months) mice.
  
  
  
  Analysis of innate immune response in bone marrow derived dendritic cells (BMDCs) from both young and aged mice upon infection with LdCen-/- parasites, showed significant enhancement of innate effector responses, which consequently augmented CD4+ Th1 cell effector function compared to LdWT infected BMDCs in vitro. Similarly, parasitized splenic dendritic cells from LdCen-/- infected young and aged mice also revealed induction of proinflammatory cytokines (IL-12, IL-6, IFN-γ and TNF) and subsequent down regulation of anti-inflammatory cytokine (IL-10) genes compared to LdWT infected mice. We also evaluated in vivo protection of the LdCen-/- immunized young and aged mice against virulent L. donovani challenge. Immunization with LdCen-/- induced higher IgG2a antibodies, lymphoproliferative response, pro- and anti-inflammatory cytokine responses and stimulated splenocytes for heightened leishmanicidal activity associated with nitric oxide production in young and aged mice. Furthermore, upon virulent L. donovani challenge, LdCen-/- immunized mice from both age groups displayed multifunctional Th1-type CD4 and cytotoxic CD8 T cells correlating to a significantly reduced parasite burden in the spleen and liver compared to naïve mice. It is interesting to note that even though there was no difference in the LdCen-/- induced innate response in dendritic cells between aged and young mice; the adaptive response specifically in terms of T cell and B cell activation in aged animals was reduced compared to young mice which correlated with less protection in old mice compared to young mice.
  
  
  
  Taken together, LdCen-/- immunization induced a significant but diminished host protective response in aged mice after challenge with virulent L. donovani parasites compared to young mice.
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Parna
authors: P
authors: Bhattacharya
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Ranadhir
authors: R
authors: Dey
authors: Flow Cytometry Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
authors: Pradeep K
authors: PK
authors: Dagur
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Amritanshu B
authors: AB
authors: Joshi
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Nevien
authors: N
authors: Ismail
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Sreenivas
authors: S
authors: Gannavaram
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Alain
authors: A
authors: Debrabant
authors: Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, Silver Spring, Maryland, United States of America.
authors: Adovi D
authors: AD
authors: Akue
authors: Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, Silver Spring, Maryland, United States of America.
authors: Mark A
authors: MA
authors: KuKuruga
authors: Institute of Molecular Medicine, New Delhi, India.
authors: Angamuthu
authors: A
authors: Selvapandiyan
authors: Flow Cytometry Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
authors: John Philip
authors: JP
authors: McCoy
authors: Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
authors: Hira L
authors: HL
authors: Nakhasi
mesh_terms: D056704:Adaptive Immunity; D000375:Aging / Q000276:immunology*; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology; D005260:Female; D055786:Gene Knockout Techniques; D007113:Immunity, Innate; D007893:Leishmania donovani / Q000235:genetics / Q000276:immunology*; D054332:Leishmaniasis Vaccines / Q000627:therapeutic use*; D007898:Leishmaniasis, Visceral / Q000276:immunology* / Q000469:parasitology; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018417:Th1 Cells / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D016207:Cytokines; D054332:Leishmaniasis Vaccines