Differential timing of antibody‐mediated phagocytosis and cell‐free killing of invasive African Salmonella allows immune evasion. Issue 4 (20th January 2014)

• Record Type: Journal Article
• Authors: Siggins, Matthew K.; O'Shaughnessy, Colette M.; Pravin, John; Cunningham, Adam F.; Henderson, Ian R.; Drayson, Mark T.; MacLennan, Calman A.
• Is Part Of: European journal of immunology. Volume 44:Issue 4(2014:Apr.)
• Page Start: 1093
• Page End: 1098
• Publication Date: 2014-01-20
• Subjects: Immunology -- Periodicals; 616.079
• DOI: 10.1002/eji.201343529
• Languages: English
• ISSNs: 0014-2980

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Nontyphoidal <italic>Salmonellae</italic> commonly cause fatal bacteraemia in African children lacking anti‐<italic>Salmonella</italic> antibodies. These are facultative intracellular bacteria capable of cell‐free and intracellular survival within macrophages. To better understand the relationship between extracellular and intracellular infection in blood and general mechanisms of Ab‐related protection against <italic>Salmonella</italic>, we used human blood and sera to measure kinetics of Ab and complement deposition, serum‐mediated bactericidal killing and phagocytosis of invasive African <italic>Salmonella enterica</italic> serovar Typhimurium D23580. Binding of antibodies peaked by 30 s, but C3 deposition lagged behind, peaking after 2–4 min. C5b‐9 deposition was undetectable until between 2 and 6 min and peaked after 10 min, after which time an increase in serum‐mediated killing occurred. In contrast, intracellular, opsonized <italic>Salmonellae</italic> were readily detectable within 5 min. By 10 min, around half of monocytes and most neutrophils contained bacteria. The same kinetics of serum‐mediated killing and phagocytosis were observed with <italic>S. enterica</italic> Typhimurium laboratory strain SL1344, and the <italic>S. enterica</italic> Enteritidis African invasive isolate D24954 and laboratory strain PT4. The differential kinetics between cell‐free killing and phagocytosis of invasive nontyphoidal <italic>Salmonella</italic> allows these bacteria to escape the blood and establish intracellular infection before they are killed by the membrane attack complex.</p> </abstract>