New Rationale and Constraints for Developing a Multicomponent and Multieffector Vaccine for a Comple

1
New Rationale and Constraints for Developing a
Multi-component and Multi-effector Vaccine for a
Complex Parasite, the Tick

• Strategies
• Reverse Vaccinology
• Reverse Immunology
• Combination
• Reverse Immunogenomics

2
Some Concepts and Definitons

• OLD X NEW Strategies for Antigen Discovery and
  Vaccine Development
• OLD
• Candidate Purified Protein -gt Cloned Gene from
  genomic DNA/cDNA-gt Recombinant Antigen -gt in vivo
  tests/readouts/challenge -gt Failure -gt Back to 0
  with new protein
• NEW Reverse Vaccinology
• Genome (struct./funct.) -gt Screen with
  Bioinformatic Criteria -gt Several Recombinant
  Antigens -gt Immunization -gt in vivo
  Tests/Readouts and/or challenge-gt better POS
• OLD
• Candidate Antigen -gt Immunize Naïve Host -gt
  Challenge -gt Protection? -gt Failure -gt Back to 0
  with a new antigen
• NEW Reverse Immunology
• Large Repertoire of Antigens -gt Screen with
  Readouts that are Surrogates of Protection
  samples from immune hosts (exposed and
  resistant/convalescent)
• Readout - Surrogate of Protection
• in vitro/in vivo test performed on immune hosts
  (vaccinated convalescents infected resistant)
  that corresponds to a protective immune response
• To identify protective antigens
• To predict protection in immunized hosts in which
  challenges cannot be done
• Type of test depends on which immune effector
  response(s) mediates protection
• Antibodies? -gt serological readout assay
• CTLs? -gt cytotoxicity readout assay

3
Reverse Vaccinology The Genomic Approach is
Heuristicit listens to the tick before chosing
antigens
I never tell my guinea pigs what I believe,I
ask them to tell me what they know.A. Brown
4
Constraints for Developing an Anti-tick Vaccine
with Reverse Vaccinology

• 1
• The genome of the cattle tick is 10 x larger than
  the human genome
• So ... NO structural genome available
• Solution functional genomics of target tissue(s)
• But which target?
• Gut, Genés organ, hemocytes, saliva
• Making a choice is not very heuristic, but we can
  try to make an educated guess.....

5
Constraints for Developing an Anti-tick Vaccine
with Reverse Immunology

• 2
• Ticks have a complex life cycle
• Larvae, nymphs, males, females, embryos.
• Which phase to target? Target antigens common to
  all phases?
• 3
• Tick saliva, one of the possible targets of the
  immune response, mediates escape mechanisms and
  parasitism
• Difficult, but saliva contains important targets

6
Tick Saliva as a Target of Protective Immune
Responses

• Pharmacological and biological properties of
  salivary proteins that are secreted into the
  host
• Anti-coagulants
• Imunosupressors (facilitate transmission of
  pathogens)
• Anti-inflammatory molecules
• Vasodilators
• Cements, allergens and silk-, loricrin- and
  keratin-like proteins

7
Developing an Anti-tick VaccineRationale for
Choice of Target Tissue

• - Memory depends on persistance of the antigen
  (Zinkernagel)
• Exposure of vaccinated hosts to infested pastures
  ( secreted proteins in tick saliva) can boost
  memory
• Secreted salivary proteins are better targets
  than hidden antigens
• Study tick salivary glands with genomic and in
  silico approaches
• Bonus the study of tick saliva can tell us a lot
  about immune correlates of protection

8
Determining the Readouts for Screening Procedures

• - Bovines present contrasting, heritable
  phenotypes for tick infestations
• Resistance is mediated, at least in part, by
  adaptive immune responses
• Bovines constitute the ONLY model for determining
  correlates of protection/surrogates of immunity
  for readouts in the same host
• Immune responses of resistant hosts are harmful
  for both tick and host
• (cement protein acute phase
  response).

Zebuines Resistant lt 20 ticks/animal Resistant
cattle lose weight in tick-infested pastures
Taurines Susceptible gt100 ticks/animal