Mapping of immunoreactive antigens of Francisella tularensis live vaccine strain.

Francisella tularensis subsp. holarctica is the common causal agent of tularemia in Europe. Besides clinical signs, the diagnosis of the disease mostly depends on serological tests. To date, there is a lack of information about the F. tularensis antigens that induce antibody response. Therefore, we have started comprehensive mapping of immunoreactive antigens using the attenuated live vaccine strain of F. tularensis LVS originating from the European virulent strain. For this purpose, the immunoreactivity of sera collected from patients suffering from tularemia, together with the control sera of patients with Lyme disease and healthy blood donors, were examined by means of one-dimensional and two-dimensional immunoblotting. Furthermore, whole cell bacterial lysates, isolated integral membrane proteins and basic proteins were exploited as antigens. By this approach more than 80 different immunorelevant antigens were detected. Most of them came from whole cell bacterial lysate and integral membrane proteins. Conversely, only a negligible reaction was found in the case of basic proteins. Forty-five spots were further selected for mass spectrometric analyses and 22 of them were annotated. Among the spots that provided characteristic reactions with sera from patients with tularemia, 60 kDa and 10 kDa chaperonins that occurred in several charge and mass variants, predominated.