Recovery of antigen-specific T cell responses from dogs infected with Leishmania (L.) infantum by use of vaccine associated TLR-agonist adjuvant. Issue 44 (17th October 2016)

• Record Type: Journal Article
• Authors: Schaut, Robert G.; Grinnage-Pulley, Tara L.; Esch, Kevin J.; Toepp, Angela J.; Duthie, Malcolm S.; Howard, Randall F.; Reed, Steven G.; Petersen, Christine A.
• Is Part Of: Vaccine. Volume 34:Issue 44(2016)
• Page Start: 5225
• Page End: 5234
• Publication Date: 2016-10-17
• Subjects: VL visceral leishmaniasis -- IFNγ interferon gamma -- Th1 T helper 1 -- TLR toll like receptor -- IFAT immunofluorescence anti-Leishmania antibody testing -- IDRI Infectious Disease Research Institute -- Con A concanavalin A -- TNFα tumor necrosis factor alpha; Leishmania (L.) infantum -- Toll-like receptor agonist -- Adjuvants -- CD4+ T cells -- Cytokines; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2016.09.016
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: Vaccine-specific T cell responses limited during clinical VL. TLR agonists recovered T cell effector functions in cells from Leishmania -infected dogs. Rational vaccine selection to improve antigen-fatigued responses crucial for endemic areas. Abstract: Visceral leishmaniasis (VL), caused by infection with the obligate intracellular protozoan parasite Leishmania infantum, is a fatal disease of dogs and humans. Protection against VL requires a T helper 1 (Th1) skewed CD4 + T response, but despite this knowledge, there are currently no approved-to-market vaccines for humans and only three veterinary-use vaccines globally. As VL progresses from asymptomatic to symptomatic, L. infantum –specific interferon gamma (IFNγ) driven-Th1 responses become dampened and a state of immune exhaustion established. T cell exhaustion and other immunoregulatory processes, starting during asymptomatic disease, are likely to hinder vaccine-induced responses if vaccine is administered to infected, but asymptomatic and seronegative, individuals. In this study we evaluated how immune exhaustion, shown previously by our group to worsen in concert with VL progression, effected the capacity of vaccine candidate antigen/toll-like receptor (TLR) agonist combinations to promote protective CD4 + T cell responses during progressive VL. In conjunction with Th1 responses, we also evaluated concomitant stimulation of immune-balanced IL-10 regulatory cytokine production by these vaccine products in progressive VL canine T cells. Vaccine antigen L111f in combination with TLR agonists significantly recovered CD4 + T cell IFNγ intracellular production in T cells from asymptomatic VL dogs. Vaccine antigen NS with TLR agonists significantly recovered CD4 + T cell production in both endemic control and VL dogs. Combinations of TLR agonists and vaccine antigens overcame L. infantum induced cellular exhaustion, allowing robust Th1 CD4 + T cell responses from symptomatic dogs that previously had dampened responses to antigen alone. Antigen-agonist adjuvants can be utilized to promote more robust vaccine responses from infected hosts in endemic areas where vaccination of asymptomatic, L. infantum -infected animals is likely.