Virulence plasmid of Aeromonas hydrophila induces macrophage apoptosis and helps in developing systemic infection in mice.
Pathogenic Aeromonas hydrophila Strain AO1 bears a 21kb plasmid encoding several virulence determinants. Infection studies revealed that this isolate induced cytotoxicity in BALB/c mice splenic macrophages involving reactive oxygen species generation. DNA gel, Hoechst 33342, annexin-V and TUNEL assay documented macrophage death induced by 21kb plasmid bearing isolates to be apoptotic in nature. Apoptosis induced by the plasmid bearing isolates involved initiator caspase-8 and caspase-9 and executed by effector caspase-3. ELISA revealed the wild-type isolate as weak inducer of pro-inflammatory cytokine IL-1beta. Oral infection with wild-type isolates caused systemic infection in BALB/c mice. With plasmid curing the isolate looses several virulence attributes including cytotoxic potential. The cured isolate induced significant amounts of IL-1beta from infected macrophages, disseminated into Peyer's patches, spleen and liver but never attained the bacterial loads recorded with wild-type isolates and were rapidly cleared. Transformation of 21kb plasmid helped the cured bacteria regain wild-type virulence attributes, apoptotic potential and ability to cause systemic infection in mice. Thus the 21kb plasmid is a virulence factor in mice. It helps in suppressing the production of pro-inflammatory cytokine IL-1beta and induced apoptosis of host macrophages enabling A. hydrophila to evade host immune responses and establish systemic infection in mice.
Majumdar
Tanmay
T
Immunobiology Laboratory, School of Life Sciences, Visva-Bharati University, Santiniketan 731 235, India.
Chattopadhyay
Pritam
P
Saha
Dhira Rani
DR
Sau
Subrato
S
Mazumder
Shibnath
S
D016980:Aeromonas hydrophila / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D000818:Animals; D017209:Apoptosis; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology*; D008264:Macrophages / Q000382:microbiology* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids; D017382:Reactive Oxygen Species / Q000378:metabolism; D014774:Virulence / Q000235:genetics
D017382:Reactive Oxygen Species