Source 1primary paper2025MED
Toolkit/virus-neutralizing assay
virus-neutralizing assay
Also known as: virus-neutralizing, VN
Taxonomy: Technique Branch / Method. Workflows sit above the mechanism and technique branches rather than replacing them.
Summary
Blood samples were collected on day 21 to measure hemagglutination inhibition (HI) and virus-neutralizing (VN) antibody responses.
Usefulness & Problems
Why this is useful
The VN assay is used in this study to measure neutralizing antibody responses induced by the FPV VLP vaccine. It is reported as significantly higher in immunized cats than in controls.; measuring vaccine-induced neutralizing antibody responses
Source:
The VN assay is used in this study to measure neutralizing antibody responses induced by the FPV VLP vaccine. It is reported as significantly higher in immunized cats than in controls.
Source:
measuring vaccine-induced neutralizing antibody responses
Problem solved
It provides a functional antibody readout to complement HI measurements. This helps assess whether vaccination induces antibodies associated with virus neutralization.; providing an immunogenicity readout after vaccination
Source:
It provides a functional antibody readout to complement HI measurements. This helps assess whether vaccination induces antibodies associated with virus neutralization.
Source:
providing an immunogenicity readout after vaccination
Problem links
providing an immunogenicity readout after vaccination
LiteratureIt provides a functional antibody readout to complement HI measurements. This helps assess whether vaccination induces antibodies associated with virus neutralization.
Source:
It provides a functional antibody readout to complement HI measurements. This helps assess whether vaccination induces antibodies associated with virus neutralization.
Published Workflows
Objective: Produce FPV VP2-based virus-like particles using a recombinant baculovirus expression system and evaluate their immunogenicity and protective efficacy in cats.
Why it works: The workflow first generates and confirms assembled FPV VLPs, then tests whether those particles induce antibody responses and protect cats from virulent challenge. The paper frames this as a route to a safer and more efficient alternative to current vaccines.
VP2-based self-assembly into virus-like particlesinduction of HI and virus-neutralizing antibody responsesrecombinant baculovirus expression in Sf9 cellsprotein purification by ultrafiltration and SECparticle characterization by DLS and TEManimal immunization and virulent challenge
Stages
- 1.VLP production and purification(library_build)
This stage generates the FPV VP2 material needed to form the vaccine candidate before characterization and animal testing.
Selection: Expression of VP2 in Sf9 insect cells followed by purification of VP2 material.
- 2.Particle assembly confirmation(functional_characterization)
This stage verifies that the expressed and purified VP2 formed virus-like particles before proceeding to animal immunization.
Selection: Confirmation of VLP assembly by DLS and TEM.
- 3.Cat immunization and serologic readout(secondary_characterization)
This stage tests whether the VLP vaccine induces measurable antibody responses in the target animal species before challenge.
Selection: Comparison of HI and VN antibody responses between vaccinated and PBS control cats.
- 4.Virulent challenge validation(confirmatory_validation)
This stage confirms whether vaccination translates into protection against virulent FPV infection in cats.
Selection: Protection from clinical signs and maintenance of white blood cell counts after virulent FPV strain 708 challenge.
Steps
- 1.Express VP2 in Sf9 insect cells using recombinant baculovirusengineered vaccine material being produced
Generate FPV VP2 protein for VLP formation.
VP2 expression is required before purification, assembly confirmation, and animal testing can occur.
- 2.Purify VP2 material by ultrafiltration and SECvaccine material being purified
Obtain purified VP2/VLP material for downstream assembly confirmation and immunization.
Purification follows expression so that the material can be characterized and used as vaccine input.
- 3.Confirm VLP assembly by DLS and TEMvaccine construct being characterized
Verify that the purified VP2 material formed virus-like particles.
Assembly confirmation is performed before animal immunization to ensure the intended VLP product was generated.
- 4.Immunize cats with three VLP dose levels and collect day-21 blood samplesvaccine administered to animals
Test dose-dependent immunization in cats and prepare for serologic assessment.
Animal dosing must precede antibody measurement and challenge testing.
- 5.Measure HI and VN antibody responsesassays used to evaluate vaccine response
Assess immunogenicity of the FPV VLP vaccine before challenge.
Serologic testing follows immunization and provides a pre-challenge readout of vaccine-induced antibody responses.
- 6.Challenge the 15 bcg dose group with virulent FPV strain 708 and monitor disease outcomesvaccine previously administered to challenged animals
Determine whether vaccination protects cats from virulent FPV disease.
Challenge is performed after immunization and serologic assessment to test whether the vaccine confers functional protection.
Taxonomy & Function
Primary hierarchy
Technique Branch
Method: A concrete measurement method used to characterize an engineered system.
Mechanisms
virus neutralizationTechniques
Functional AssayTarget processes
No target processes tagged yet.
Implementation Constraints
cofactor dependency: cofactor requirement unknownencoding mode: genetically encodedimplementation constraint: context specific validationoperating role: sensor
The abstract supports the need for blood samples collected on day 21. It does not specify the neutralization protocol or reagents.; requires blood sampling from immunized animals
The abstract does not show whether VN titers predict cross-strain protection or durability. It also does not provide assay thresholds or benchmarking details.; abstract does not provide assay protocol details or titer values
Validation
Cell-freeBacteriaMammalianMouseHumanTherapeuticIndep. Replication
Observations
successLarge Animalapplication democat
serology
Inferred from claim c2 during normalization. Immunization with the FPV VLP vaccine produced significantly higher HI and VN antibody titers than PBS control in cats. Derived from claim c2. Quoted text: Immunized cats exhibited significantly higher HI and VN antibody titers compared to controls.
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Supporting Sources
Ranked Claims
PBS control cats developed severe symptoms and significant leukopenia after virulent FPV challenge, unlike vaccinated cats.
In contrast, control cats developed severe symptoms and experienced significant leukopenia.
An FPV VLP vaccine was produced using a recombinant baculovirus system expressing VP2 in Sf9 insect cells, and VLP assembly was confirmed by DLS and TEM.
Sf9 insect cells were infected with recombinant baculovirus to express VP2 protein. The VP2 protein was purified using ultrafiltration and size-exclusion chromatography (SEC). Dynamic light scattering (DLS) and transmission electron microscopy (TEM) confirmed the assembly of VLPs.
Immunization with the FPV VLP vaccine produced significantly higher HI and VN antibody titers than PBS control in cats.
Immunized cats exhibited significantly higher HI and VN antibody titers compared to controls.
The FPV VLP vaccine protected challenged cats from clinical disease and leukopenia after virulent FPV strain 708 challenge.
Cats in the 15 bcg dose group were challenged with virulent FPV strain 708 on day 21, and clinical signs and white blood cell counts were monitored for 10 days. After challenge, vaccinated cats showed no clinical signs of disease, and their white blood cell counts remained stable.
challenge monitoring duration 10 days
Approval Evidence
1 source1 linked approval claimfirst-pass slug virus-neutralizing-assay
Blood samples were collected on day 21 to measure hemagglutination inhibition (HI) and virus-neutralizing (VN) antibody responses.
Source:
immunogenicitysupports
Immunization with the FPV VLP vaccine produced significantly higher HI and VN antibody titers than PBS control in cats.
Immunized cats exhibited significantly higher HI and VN antibody titers compared to controls.
Source:
Comparisons
Source-stated alternatives
The study also uses HI as a parallel serologic assay.
Source:
The study also uses HI as a parallel serologic assay.
Source-backed strengths
explicitly used alongside HI to assess antibody responses
Source:
explicitly used alongside HI to assess antibody responses
Compared with Langendorff perfused heart electrical recordings
virus-neutralizing assay and Langendorff perfused heart electrical recordings address a similar problem space.
Shared frame: same top-level item type
Strengths here: looks easier to implement in practice.
Compared with native green gel system
virus-neutralizing assay and native green gel system address a similar problem space.
Shared frame: same top-level item type
Strengths here: looks easier to implement in practice.
virus-neutralizing assay and sub-picosecond pump-probe analysis of bacteriorhodopsin pigments address a similar problem space.
Shared frame: same top-level item type
Strengths here: looks easier to implement in practice.
Ranked Citations
- 1.