Regulated delayed expression of rfaH in an attenuated Salmonella enterica serovar typhimurium vaccine enhances immunogenicity of outer membrane proteins and a heterologous antigen

Qingke Kong, Qing Liu, Kenneth L. Roland, Roy Curtiss

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

RfaH is a transcriptional antiterminator that reduces the polarity of long operons encoding secreted and surface-associated cell components of Salmonella enterica serovar Typhimurium, including O antigen and lipopolysaccharide core sugars. A ΔrfaH mutant strain is attenuated in mice (50% lethal dose [LD50], >108 CFU). To examine the potential for using rfaH in conjunction with other attenuating mutations, we designed a series of strains in which we replaced the native rfaH promoter with the tightly regulated arabinose-dependent araC PBAD promoter so that rfaH expression was dependent on exogenously supplied arabinose provided during in vitro growth. Following colonization of host lymphoid tissues, where arabinose was not available, the PBAD promoter was no longer active and rfaH was not expressed. In the absence of RfaH, O antigen and core sugars were not synthesized. We constructed three mutant strains that expressed different levels of RfaH by altering the ribosome-binding sequence and start codon. One mutation, ΔPrfaH178, was introduced into the attenuated vaccine strain χ9241 (ΔpabA ΔpabB ΔasdA) expressing the pneumococcal surface protein PspA from an Asd+ balanced-lethal plasmid. Mice immunized with this strain and boosted 4 weeks later induced higher levels of serum immunoglobulin G specific for PspA and for outer membrane proteins from other enteric bacteria than either an isogenic ΔrfaH derivative or the isogenic RfaH+ parent. Eight weeks after primary oral immunization, mice were challenged with 200 LD50 of virulent Streptococcus pneumoniae WU2. Immunization with ΔPrfaH178 mutant strains led to increased levels of protection compared to that of the parent χ9241 and of a ΔrfaH derivative of χ9241.

Original languageEnglish (US)
Pages (from-to)5572-5582
Number of pages11
JournalInfection and Immunity
Volume77
Issue number12
DOIs
StatePublished - Dec 2009

Fingerprint

Heterophile Antigens
Arabinose
Salmonella enterica
Lethal Dose 50
O Antigens
Membrane Proteins
Immunization
Attenuated Vaccines
Mutation
Initiator Codon
Lymphoid Tissue
Enterobacteriaceae
Cellular Structures
Operon
Streptococcus pneumoniae
Ribosomes
Lipopolysaccharides
Plasmids
Immunoglobulin G
Growth

ASJC Scopus subject areas

  • Immunology
  • Microbiology
  • Parasitology
  • Infectious Diseases

Cite this

Regulated delayed expression of rfaH in an attenuated Salmonella enterica serovar typhimurium vaccine enhances immunogenicity of outer membrane proteins and a heterologous antigen. / Kong, Qingke; Liu, Qing; Roland, Kenneth L.; Curtiss, Roy.

In: Infection and Immunity, Vol. 77, No. 12, 12.2009, p. 5572-5582.

Research output: Contribution to journalArticle

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