Autoantibody profiles in the sera of patients with Q fever: characterization of antigens by immunofluorescence, immunoblot and sequence analysis

Abstract

Recent reports have shown that some of the immunological aspects of Q fever, a rickettsiosis caused by Coxiella burnetii, could be related to self-antigen responses. The aim of this study was to determine the specificity of the autoantibody response of patients with acute and chronic Coxiella infections. Smooth muscle and cardiac muscle-specific autoantibodies were observed in significant percentages in acutely or chronically affected Q fever patients when compared to healthy volunteers. Moreover, the incidence of cardiac muscle-specific autoantibody was significantly higher among chronically ill patients compared to acutely ill patients. Moreover, a band of 50 kD of a HeLa extract was detected in most of the sera of individuals with chronic infections and previous sequence analysis suggests that this antigen presents a high degree of homology with the human actin elongation factor 1 alpha. Further research would be necessary to confirm if antibodies to human cytoskeletal proteins could be of clinical importance in chronically infected Q fever patients.

Figure 1

Fibrillar indirect immunofluorescence stain with obtained with sera of Q fever patients using monkey cardiac muscle sections. Magnification × 400.

Figure 2

IgG antibodies detected in sera of Q fever patients against partially purified HeLa cell antigens by Western blot analysis. Incubated with sera from acute (number. 1,5,6,10,15,20,24) and chronic (number: 2,7,10,11,15,22,27,28,31,32) Q fever patients. Results obtained with representative sera from each group are depicted. Location of the 50 kD bands are indicated.

Figure 3

Sequence alignement of a fraction of the chromatogram of the 50 kD HeLa protein trypsin digestion and human elongation factor 1alpha.