New strategies for Leptospira vaccine development based on LPS removal

PLoS One. 2020 Mar 27;15(3):e0230460. doi: 10.1371/journal.pone.0230460. eCollection 2020.

Abstract

Pathogenic spirochetes from genus Leptospira are etiologic agents of leptospirosis. Cellular vaccines against Leptospira infection often elicit mainly response against the LPS antigen of the serovars present in the formulation. There is no suitable protein candidate capable of replacing whole-cell vaccines, thus requiring new approaches on vaccine development to improve leptospirosis prevention. Our goal was to develop a whole-cell vaccine sorovar-independent based on LPS removal and conservation of protein antigens exposure, to evaluate the protective capacity of monovalent or bivalent vaccines against homologous and heterologous virulent Leptospira in hamster. Leptospire were subjected to heat inactivation, or to LPS extraction with butanol and in some cases further inactivation with formaldehyde. Hamsters were immunized and challenged with homologous or heterologous virulent serovars, blood and organs were collected from the survivors for bacterial quantification, chemokine evaluation, and analysis of sera antibody reactivity and cross-reactivity by Western blot. Immunization with either heated or low LPS vaccines with serovar Copenhageni or Canicola resulted in 100% protection of the animals challenged with homologous virulent bacteria. Notably, different from the whole-cell vaccine, the low LPS vaccines produced with serovar Canicola provided only partial protection in heterologous challenge with the virulent Copenhageni serovar. Immunization with bivalent formulation results in 100% protection of immunized animals challenged with virulent serovar Canicola. All vaccines produced were able to eliminate bacteria from the kidney of challenged animals. All the vaccines raised antibodies capable to recognize antigens of serovars not present in the vaccine formulation. Transcripts of IFNγ, CXCL16, CCL5, CXCL10, CXCR6, and CCR5, increased in all immunized animals. Conclusion: Our results showed that bivalent vaccines with reduced LPS may be an interesting strategy for protection against heterologous virulent serovars. Besides the desirable multivalent protection, the low LPS vaccines are specially promising due to the expected lower reatogenicity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Bacterial / immunology
  • Bacterial Vaccines* / chemistry
  • Bacterial Vaccines* / immunology
  • Cricetinae
  • Leptospira / chemistry
  • Leptospira / immunology*
  • Leptospirosis / immunology*
  • Leptospirosis / prevention & control
  • Lipopolysaccharides / chemistry*
  • Vaccination*

Substances

  • Antibodies, Bacterial
  • Bacterial Vaccines
  • Lipopolysaccharides

Grants and funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq (JBS grant 473035/2013–8), Fundação de Amparo a Pesquisa do Estado de São Paulo-FAPESP and Fundação Butantan (Brazil). PLDS and IG received scholarships from Instituto Butantan-Secretaria da Saúde do Estado de São Paulo. NMA and BFS received scholarships from CNPq.