ABSTRACT
Comparative genomic analysis of a wild-type strain of the ovine pathogen Chlamydia abortus and its nitrosoguanidine-induced, temperature-sensitive, virulence-attenuated live vaccine derivative identified 22 single nucleotide polymorphisms unique to the mutant, including nine nonsynonymous mutations, one leading to a truncation of pmpG, which encodes a polymorphic membrane protein, and two intergenic mutations potentially affecting promoter sequences. Other nonsynonymous mutations mapped to a pmpG pseudogene and to predicted coding sequences encoding a putative lipoprotein, a sigma-54-dependent response regulator, a PhoH-like protein, a putative export protein, two tRNA synthetases, and a putative serine hydroxymethyltransferase. One of the intergenic mutations putatively affects transcription of two divergent genes encoding pyruvate kinase and a putative SOS response nuclease, respectively. These observations suggest that the temperature-sensitive phenotype and associated virulence attenuation of the vaccine strain result from disrupted metabolic activity due to altered pyruvate kinase expression and/or alteration in the function of one or more membrane proteins, most notably PmpG and a putative lipoprotein.
Subject(s)
Bacterial Proteins/metabolism , Bacterial Vaccines/immunology , Chlamydophila psittaci/genetics , Chlamydophila psittaci/immunology , Genome, Bacterial , Cephalosporins/chemistry , Chlamydophila psittaci/metabolism , Glycine Hydroxymethyltransferase/chemistry , Glycine Hydroxymethyltransferase/genetics , Membrane Proteins/metabolism , Methionine-tRNA Ligase/chemistry , Methionine-tRNA Ligase/genetics , Mutation , Polymorphism, Single Nucleotide , Vaccines, Attenuated/immunology , VirulenceABSTRACT
The efficacy of a live 1B vaccine against three strains of Chlamydophila abortus, AB16, LLG and POS, was assessed in pregnant mice in terms of the reduction in the levels of infection recorded in their placentas, fetuses and spleens. The vaccine was more effective against the AB16 strain than against the LLG and POS strains, suggesting that there are antigenic differences between the three strains.
Subject(s)
Abortion, Veterinary , Bacterial Vaccines/immunology , Chlamydophila Infections/veterinary , Chlamydophila/immunology , Pregnancy Complications, Infectious/veterinary , Abortion, Veterinary/microbiology , Abortion, Veterinary/prevention & control , Animals , Chlamydophila Infections/complications , Chlamydophila Infections/prevention & control , Female , Fetus/microbiology , Mice , Placenta/microbiology , Pregnancy , Pregnancy Complications, Infectious/microbiology , Pregnancy Complications, Infectious/prevention & control , Spleen/microbiology , Vaccination/veterinaryABSTRACT
The efficacy of Chlamydophila abortus vaccine strain 1B in protecting against two selected Chlamydophila pecorum strains, isolated from an aborted goat (M14) in Morocco and a ewe (AB10) in France, was investigated in a mouse model, by comparing the reduction in number of bacteria in the placentas of vaccinated mice challenged intraperitoneally at 11 days of pregnancy with the reference C. abortus (AB7) and C. pecorum (M14, or AB10) strains, to those of unvaccinated mice. Vaccine 1B was shown to provide effective protection against the field strains of C. pecorum, since it significantly reduced the placental Chlamydophila colonisation. The two C. pecorum strains were not sufficiently abortifacient in mice to use reduction in abortion as a criterion of protection.
