It remains unclear why vaccines targeting prominent microbial virulence factors often fail in clinical trials. Because microbial virulence depends on interaction with the host immune system, we investigated how changes in host immune function alter vaccine efficacy. Using a vaccine against Staphylococcus aureus α-toxin (Hla), which targets host metalloprotease ADAM10 on myeloid cells, we show that Hla virulence is reduced in aged mice due to diminished ADAM10 activity and impaired myeloid cell function. Depletion of myeloid cells with cyclophosphamide in young mice similarly reduced toxin virulence. Immunization against Hla conferred strong protection against S. aureus infection in young but not aged mice. These findings indicate that pathogenic functions of microbial factors characterized in immunocompetent young animals may not predict virulence or vaccine efficacy in immunocompromised hosts. These findings underscore the need to account for host immune status in the development and evaluation of vaccines targeting microbial virulence factors.
Xin Du, Ching Wen Tseng, Elisabet Bjånes, Hunter Gage, Jaclyn Swan, Chih-Ming Tsai, Irshad A. Hajam, Cesia Gonzalez, Brian Lin, Victor Nizet, George Y. Liu
Usage data is cumulative from June 2026 through June 2026.
| Usage | JCI | PMC |
|---|---|---|
| Text version | 305 | 0 |
| 88 | 0 | |
| Figure | 142 | 0 |
| Supplemental data | 52 | 0 |
| Citation downloads | 46 | 0 |
| Totals | 633 | 0 |
| Total Views | 633 | |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.