Vaccinia virus complement control protein increases early bacterial clearance during experimental peritonitis.
BACKGROUND
Complement is one of the first immunological pathways activated in peritonitis. It functions to initiate and augment the innate immune response. Complement activation has also been shown to contribute to multiple organ failure after sepsis. Vaccinia virus complement control protein (VCP) is an immunomodulatory protein encoded by vaccinia virus and binds complement components C3b and C4b of the complement cascade to inhibit both the classical and alternative pathways of complement activation. This study investigates the effect of complement inhibition by recombinant (r) VCP on bacterial clearance after cecal ligation and puncture (CLP).


METHODS
Swiss Webster mice were intravenously given either 20 mg/kg rVCP in 0.2 mL of normal saline, or 0.2 mL of normal saline alone, at the time of CLP. After 4 and 18 h, samples of peritoneal washout, blood, liver, and lung were collected for bacteriology, myeloperoxidase (MPO) assay for neutrophil accumulation, differential cell counts, and interleukin (IL)12 ELISA. Statistical analysis was by Mann-Whitney U test for bacteriology, and analysis of variance (ANOVA) for MPO and IL-12 concentrations.


RESULTS
Aerobic and anaerobic bacterial levels were significantly lower at 4 h after treatment with rVCP (p < 0.05) in peritoneal lavage, blood, and liver compared with controls. There were no differences in bacterial levels at 18 h. There were no differences in myeloperoxidase concentrations or in the differential cell counts between the groups at either 4 or 18 h after CLP. IL-12 concentrations in serum or peritoneal washout were also not different.


CONCLUSIONS
rVCP enhances early bacterial clearance in mice after CLP, although not through neutrophil recruitment, as MPO concentrations and cell counts were not different. rVCP may, however, increase neutrophil function potentially by prevention of accumulation of complement factors that inhibit leukocytes. Further studies will be needed to elucidate this pathway.
Scott
Melanie J
MJ
Departments of Surgery, and Microbiology & Immunology, University of Louisville School of Medicine, and the Veterans Affairs Medical Center, Louisville, Kentucky 40292, USA.
Burch
Phillip T
PT
Jha
Puroshottam
P
Peyton
James C
JC
Kotwal
Girish J
GJ
Cheadle
William G
WG
D000818:Animals; D001769:Blood / Q000382:microbiology; D015169:Colony Count, Microbial; D003169:Complement Inactivator Proteins / Q000494:pharmacology*; D003165:Complement System Proteins / Q000502:physiology*; D004195:Disease Models, Animal; D018664:Interleukin-12 / Q000276:immunology; D007958:Leukocyte Count; D008099:Liver / Q000276:immunology / Q000382:microbiology; D008168:Lung / Q000276:immunology / Q000382:microbiology; D008297:Male; D051379:Mice; D010537:Peritoneum / Q000276:immunology / Q000382:microbiology; D010538:Peritonitis / Q000276:immunology* / Q000382:microbiology*; D009195:Peroxidase / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D014764:Viral Proteins / Q000276:immunology / Q000494:pharmacology*
D003169:Complement Inactivator Proteins; D011994:Recombinant Proteins; D014764:Viral Proteins; C066459:complement-control protein, Vaccinia virus; D018664:Interleukin-12; D003165:Complement System Proteins; D009195:Peroxidase