Immune response genes in the post-Q-fever fatigue syndrome, Q fever endocarditis and uncomplicated acute primary Q fever

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Abstract
Background: The influence of immune response gene variations on the development of chronic complications of Q fever is presently unclear. Aim: To compare the frequencies of allelic polymorphisms in immune response genes in different Q fever patient groups. Design: Genetic association study. Methods: We measured the frequencies of immune response gene variants in: (i) an expanded group of 31 post-Q-fever fatigue patients (QFS); (ii) 22 Q fever endocarditis patients (QFE); and (iii) 22 patients who made an uncomplicated recovery from their initial attack of primary acute Q fever, comparing them with various standard control panels from the general population. Results: There were significant differences between the three Q fever groups. QFS patients differed from both QFE and uncomplicated patients and controls in the frequency of carriage of HLA-DRB1*11 and of the 2/2 genotype of the interferon-γ intron1 microsatellite. Carriage of the HLA DRB1*11 allele was associated with reduced interferon-γ and IL-2 responses from PBMC stimulated with ligand in short-term culture. QFE showed differences in the IL-10 promoter microsatellites R and G and had higher frequencies of the TNF-α receptor II 196R polymorphism. Q fever patients who had made an uncomplicated recovery differed from those with QFS or QFE, but were not significantly different in allelic frequencies to the control panels. Discussion: These immunogenetic differences support the concept of different immune states in chronic Q fever, determined by genetic variations in host immune responses, rather than by solely properties of Coxiella burnetii.

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