Vaccination-induced neutralizing antibodies in immunocompetent hosts correlate with protection against rickettsiae

Authors

• Loka Reddy Velatooru, John Sealy School of Medicine
• Jessica Plante, John Sealy School of Medicine
• Chen Yi Chu, John Sealy School of Medicine
• Garrett Cutchin, John Sealy School of Medicine
• Bing Zhu, John Sealy School of Medicine
• Nicole Burkhardt, University of Minnesota Twin Cities
• Carsen Roach, John Sealy School of Medicine
• Yingzi Cong, John Sealy School of Medicine
• Shahid Karim, University of Southern MississippiFollow
• Yong Fang Kuo, The University of Texas Medical Branch at Galveston
• David H. Walker, John Sealy School of MedicineFollow
• Ulrike Munderloh, University of Minnesota Twin Cities
• Rong Fang, John Sealy School of Medicine

Document Type

Article

Publication Date

12-1-2025

School

Biological, Environmental, and Earth Sciences

Abstract

We previously demonstrated that a single-dose immunization with a live-attenuated Rickettsia parkeri mutant 3A2 confers complete protection against murine spotted fever rickettsioses. In this study, we investigated whether vaccination-elicited serum antibodies serve as immune correlates of protection against rickettsiae. Immunization of immunocompetent C3H/HeN mice with 3A2 induced a robust and durable level of IgG antibody response, predominantly comprising IgG2a, IgG3, and IgG2b subclasses, and was associated with a significant expansion of CD19⁺ CD45R⁺ IgD^low plasma cells. Compared to mock controls, passive transfer of immune sera from 3A2-immunized mice protected C3H-SCID mice from R. parkeri challenge via multiple inoculation routes, including i.v., i.d. and i.d. plus tick saliva. Strikingly, serum antibodies of 3A2-immunized mice significantly reduced the number of R. parkeri plaques in vitro, indicating direct neutralizing activity. Collectively, our findings demonstrate that vaccination-induced serum IgG antibodies correlate with protection against rickettsial infection and possess direct neutralizing effects on rickettsiae.

Publication Title

Npj Vaccines

Volume

10

Issue

1

Recommended Citation

Velatooru, L., Plante, J., Chu, C., Cutchin, G., Zhu, B., Burkhardt, N., Roach, C., Cong, Y., Karim, S., Kuo, Y., Walker, D., Munderloh, U., Fang, R. (2025). Vaccination-induced neutralizing antibodies in immunocompetent hosts correlate with protection against rickettsiae. Npj Vaccines, 10(1).
Available at: https://aquila.usm.edu/fac_pubs/22275