Immunization with SARS coronavirus vaccines leads to pulmonary immunopathology on challenge with the SARS virus.
Level 5 - mechanism / opinion, no new human data
Preclinical animal challenge study with no human data
PubMed 22536382 · doi:10.1371/journal.pone.0035421
What was done
Four candidate SARS-CoV vaccines (a virus-like particle vaccine, two whole inactivated virus formulations, and a recombinant DNA-produced S protein vaccine), with or without alum adjuvant, were evaluated in Balb/c and C57BL/6 mice. Mice received intramuscular injections on days 0 and 28, followed by serum antibody testing or challenge with live SARS-CoV on day 56. Control groups received influenza vaccine, PBS, or prior live SARS-CoV. Two days post-challenge (day 58), lungs were harvested for viral load quantification and histopathologic assessment.
What was found
All vaccines elicited serum neutralizing antibodies, with higher doses and alum adjuvant significantly enhancing antibody titers. All four candidate vaccines and prior live SARS-CoV infection resulted in significant reductions in lung viral titers at day 2 post-challenge compared to controls. However, all SARS-CoV vaccinated mice uniformly developed Th2-type pulmonary immunopathology with prominent eosinophil infiltration upon viral challenge. While lung histopathologic changes occurred across all challenged groups including controls, prominent eosinophil infiltration was specific to the SARS-CoV vaccinated animals and absent in controls (influenza vaccine, PBS, or prior live virus). Specific numerical values for titers, viral load reductions, and animal counts were not reported in the abstract.
Why it matters
This study demonstrated that while candidate SARS-CoV vaccines can successfully stimulate neutralizing antibodies and reduce viral load, they can also prime the immune system for hypersensitivity-associated lung pathology upon subsequent viral exposure, highlighting a critical safety consideration for coronavirus vaccine development.
Limits
The study was conducted exclusively in mouse models, and findings may not directly translate to human clinical immune responses. Exact sample sizes per group, numerical antibody titers, viral clearance quantities, and statistical metrics were not provided in the abstract. Long-term follow-up beyond two days post-challenge was not evaluated.
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