Pitfalls in anti-influenza T cell detection by Elispot using thimerosal containing pandemic H1N1 vaccine as antigen.

Monitoring T cells in combination with humoral response may be of value to predict clinical protection and cross-protective immunity after influenza vaccination. Elispot technique which measures cytokine produced after antigen-specific T cell stimulation is used routinely to detect and characterize anti-viral T cells. We found that the preservative thimerosal present in most H1N1 pandemic vaccines, induced in vitro abortive activation of T cells followed by cell death leading to false-positive results with the Elispot technique. The size of the spots, usually not measured in routine analysis, appears to be a discriminative criterion to detect this bias. Multi-dose vials of vaccine containing thimerosal remain important for vaccine delivery and our results alert about false-positive results of Elispot to monitor the clinical efficacy of these vaccines. We showed that this finding extends for other T cell monitoring techniques based on cytokine production such as ELISA. Although measuring in vitro immune response using the whole vaccine used for human immunization directly reflects in vivo global host response to the vaccine, the present study strongly supports the use of individual vaccine components for immune monitoring due to the presence of contaminants, such as thimerosal, leading to a bias in interpretation of the results.

[Pneumococcal endocarditis in native valves. Three original observations in the adult]. / Endocardites à pneumocoque sur valves natives. Trois observations originales chez l'adulte.

The authors report three observations of acute pneumococcal endocarditis located in the aorta in one case, and mitral in the two other cases, admitted over a period of 4 years. Two of the three patients required surgical correction, with no surgical complications. Follow-up revealed a rare complication of infectious endocarditis linked to rupture of the head of the two anterior mitral pillars associated with an abscess. The severity of pneumococcal endocarditis is emphasised, concurring with the data from the literature. The role of echocardiography in pneumococcal septicaemia is clear; transthoracic examination is justified in every case of septicaemia, and transoesophageal echography complements this examination in case of diagnostic doubt or cardiovascular complication.