Toll-like receptor 8 agonist nanoparticles mimic immunomodulating effects of the live BCG vaccine and enhance neonatal innate and adaptive immune responses.
BACKGROUND
Newborns display distinct immune responses, leaving them vulnerable to infections and impairing immunization. Targeting newborn dendritic cells (DCs), which integrate vaccine signals into adaptive immune responses, might enable development of age-specific vaccine formulations to overcome suboptimal immunization.


OBJECTIVE
Small-molecule imidazoquinoline Toll-like receptor (TLR) 8 agonists robustly activate newborn DCs but can result in reactogenicity when delivered in soluble form. We used rational engineering and age- and species-specific modeling to construct and characterize polymer nanocarriers encapsulating a TLR8 agonist, allowing direct intracellular release after selective uptake by DCs.


METHODS
Chemically similar but morphologically distinct nanocarriers comprised of amphiphilic block copolymers were engineered for targeted uptake by murine DCs in vivo, and a range of TLR8 agonist-encapsulating polymersome formulations were then synthesized. Novel 96-well in vitro assays using neonatal human monocyte-derived DCs and humanized TLR8 mouse bone marrow-derived DCs enabled benchmarking of the TLR8 agonist-encapsulating polymersome formulations against conventional adjuvants and licensed vaccines, including live attenuated BCG vaccine. Immunogenicity of the TLR8 agonist adjuvanted antigen 85B (Ag85B)/peptide 25-loaded BCG-mimicking nanoparticle formulation was evaluated in vivo by using humanized TLR8 neonatal mice.


RESULTS
Although alum-adjuvanted vaccines induced modest costimulatory molecule expression, limited TH-polarizing cytokine production, and significant cell death, BCG induced a robust adult-like maturation profile of neonatal DCs. Remarkably, TLR8 agonist polymersomes induced not only newborn DC maturation profiles similar to those induced by BCG but also stronger IL-12p70 production. On subcutaneous injection to neonatal mice, the TLR8 agonist-adjuvanted Ag85B peptide 25 formulation was comparable with BCG in inducing Ag85B-specific CD4+T-cell numbers.


CONCLUSIONS
TLR8 agonist-encapsulating polymersomes hold substantial potential for early-life immunization against intracellular pathogens. Overall, our study represents a novel approach for rational design of early-life vaccines.
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass. Electronic address: david.dowling@childrens.harvard.edu.
David J
DJ
Dowling
Department of Biomedical Engineering, Northwestern University, Evanston, Ill. Electronic address: evan.scott@northwestern.edu.
Evan A
EA
Scott
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass; Division of Newborn Medicine, Floating Hospital for Children, Tufts Medical Center, Boston, Mass; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Annette
A
Scheid
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Ilana
I
Bergelson
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Sweta
S
Joshi
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass; Neonatal Intensive Care Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Carlo
C
Pietrasanta
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Spencer
S
Brightman
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Guzman
G
Sanchez-Schmitz
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass.
Simon D
SD
Van Haren
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass.
Jana
J
Ninković
Department of Biomedical Engineering, Northwestern University, Evanston, Ill.
Dina
D
Kats
Dynavax Technologies, Berkeley, Calif.
Cristiana
C
Guiducci
Institute of Bioengineering, School of Life Sciences and School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Alexandre
A
de Titta
Institute of Bioengineering, School of Life Sciences and School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Daniel K
DK
Bonner
Institute of Bioengineering, School of Life Sciences and School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Sachiko
S
Hirosue
Institute of Bioengineering, School of Life Sciences and School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; Institute for Molecular Engineering, University of Chicago, Chicago, Ill.
Melody A
MA
Swartz
Institute of Bioengineering, School of Life Sciences and School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; Institute for Molecular Engineering, University of Chicago, Chicago, Ill.
Jeffrey A
JA
Hubbell
Department of Medicine, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass; Harvard Medical School, Boston, Mass; Precision Vaccine Program, Division of Infectious Diseases, Boston Children's Hospital, Boston, Mass. Electronic address: ofer.levy@childrens.harvard.edu.
Ofer
O
Levy
D056704:Adaptive Immunity; D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D000831:Animals, Newborn; D001500:BCG Vaccine / Q000276:immunology*; D032701:Biomimetics; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology*; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D007113:Immunity, Innate; D056747:Immunomodulation; D007231:Infant, Newborn; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D009000:Monocytes / Q000276:immunology*; D053758:Nanoparticles / Q000008:administration & dosage* / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011804:Quinolines / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D051200:Toll-Like Receptor 8 / Q000819:agonists; D014611:Vaccination
D000276:Adjuvants, Immunologic; D001500:BCG Vaccine; D016207:Cytokines; D007093:Imidazoles; D011108:Polymers; D011804:Quinolines; C495349:TLR8 protein, human; D051200:Toll-Like Receptor 8; C037219:quinoline
BCG; Newborn; Toll-like receptor 8; dendritic cells; nanoparticle; polymersome; vaccine