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U.S. Department of Health and Human Services

Vaccines, Blood & Biologics

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Working towards keeping stored platelets free of bacteria

 

Scientists at the US Food and Drug Administration (FDA) have demonstrated in animal studies a proof-of-concept approach that might reduce the bacterial burden of room temperature stored human platelets. Platelets are used to treat patients for a variety of disorders, including excessive bleeding from wounds and immune system dysfunction.  
 
The FDA scientists showed that treating platelet concentrates with molecules called antimicrobial peptides (AMPs) eliminates bacterial contamination of these cells.  AMPs are small protein-like molecules that kill bacteria, viruses, fungi, and protozoa. A wide variety of organisms, including humans, produce AMPs. Platelet concentrates are platelets that are stored in plastic bags after much of the plasma (liquid part of blood) in which they normally are suspended in the bloodstream has been removed.
 
Platelets are collected under conditions intended to maintain the sterility of the platelets, but in rare circumstances, collections contain contaminating microbes. 
  
The FDA findings are important because platelets cannot be refrigerated (a method often used to reduce bacterial growth) because cool temperatures cause changes in the cells that make the body quickly dispose of them following transfusion. Therefore, these cells must be stored at room temperature, which enables bacteria that are already present to multiply. 

 
FDA scientists previously showed that certain AMPs killed bacteria that are commonly found to contaminate stored platelet concentrates (platelets stored in bags after much of the plasma in which they normally are suspended in the bloodstream has been removed). There are no known studies showing whether treatment of human platelet concentrates with AMPs reduces the survivability of platelets in the body following transfusion or whether the AMPs generate any antibodies in an animal model. Therefore, the current study sought to evaluate a few selected AMPs for their potential antibody response in rabbits and to investigate the effect of the same AMPs on recovery and survival of human platelets transfused into mice.
 
The FDA scientists synthesized six selected AMPs and studied the effect of these peptides in animal models. The study found in rabbits that the AMPs did not trigger a significant production of antibodies that would attack these molecules and block their antimicrobial action; nor did AMPs degrade the quality of human platelets following transfusion into mice. 

 
The results of the study suggest that carefully screened and selected AMPs should be further investigated for possible use in reducing bacterial levels in stored human platelets. The goal is to improve public health by ensuring there are adequate supplies of safe and effective platelets.
 
Title
“Preclinical safety evaluation of human platelets treated with antimicrobial peptides in severe combined immunodeficient mice”
 
Transfusion 2013 Jun 30. doi: 10.1111/trf.12318. [Epub ahead of print]           
 
Authors
Marta Bosch-Marcé, Ketha V.K. Mohan, Monique P. Gelderman, Patricia L. Ryan,
Estelle Russek-Cohen, and Chintamani D. Atreya