Interleukin 2 and gamma interferon production, interleukin 2 receptor expression, and DNA synthesis induced by tularemia antigen in vitro after natural infection or vaccination

Abstract

The T-cell response induced by Francisella tularensis antigen in sensitized subjects was characterized in vitro by measuring DNA synthesis in whole-blood and mononuclear cell cultures, interleukin 2 (IL-2) and gamma interferon (IFN-gamma) production, and IL-2 receptor expression. Correlations between these variables were estimated. The strengths of the responses were compared in 21 subjects naturally infected 2 years ago, 6 subjects vaccinated 5 to 6 years ago, and 13 control subjects with no history of infection or vaccination. Subjects with a history of natural infection synthesized more DNA in both whole-blood and mononuclear cell cultures, secreted more IL-2 and IFN-gamma, and expressed more IL-2 receptors than control subjects did. All these responses differed highly significantly (P less than 0.001) from those of the control subjects. The vaccinees exhibited somewhat lower responses than the naturally immunized subjects did, but the vaccinees could be distinguished from the control subjects by their DNA synthesis, receptor expression, and IFN-gamma production (P less than 0.01 to 0.001). The vaccinees showed a lower response, in terms of DNA synthesis and IL-2 secretion (P less than 0.05), than the infected group did but responded in a manner similar to that of this group, with respect to receptor positivity and IFN-gamma secretion (P greater than 0.10). The correlations between all the T-cell functions were good, with highly significant correlations (P less than 0.001) between whole-blood DNA synthesis and IL-2 and IFN-gamma secretion and between the two lymphokines (P less than 0.001). The results not only increase our knowledge of the T-cell response to tularemia antigen but also give an alternative approach to DNA synthesis measurement for the quantitation of T-cell responses. The results for the low-responding sensitized subjects seem to indicate that the parameters were comparable in sensitivity.

Francisella tularensis-induced in vitro gamma interferon, tumor necrosis factor alpha, and interleukin 2 responses appear within 2 weeks of tularemia vaccination in human beings

“…Most of the individual responses were nevertheless clearly distinguishable from the initial ones. The approach used here differs from our earlier studies (8,9) with regard to the state of immunity. In earlier studies, the immunity was established as to its nature, i.e., memory immunity, while here we measured developing parameters.…”

“…Cellmediated immunity therefore confers protection against the microbe, as has been shown clearly in animal experiments (for a review, see reference 22). The in vitro T-cell responses observed in connection with human natural or vaccineinduced immunity include, in addition to positive T-cell proliferation, specific secretion of the lymphokines interleukin 2 (IL-2) and gamma interferon (IFN-y), expression of IL-2 receptor-positive cells, and the possibility of generating F. tularensis-specific T-cell clones (8,9,21).…”

“…Measurement of DNA synthesis. DNA synthesis was determined by using both mononuclear cell (MC) and wholeblood (WB) cultures (8). RPMI 1640 supplemented with 5% fetal calf serum was used as the culture medium.…”

“…IL-2 was quantified by using an IL-2-dependent mouse cytotoxic T-cell line (8). A total of 5,000 cytotoxic T-cell line cells in a 100-pl volume were cultured for 48 h with 100-pI aliquots of supernatant dilutions of 1:1 and 1:2.…”

Identification and characterization of capsule and/or O-antigen mutants of Francisella tularensis Schu S4

“…Murine vaccination studies using LVS have shown that protection is dependent upon the production of CD4 + and CD8 + T cells (70,223,232) and this same response has been shown to be important in protective immunity to M. tuberculosis and Brucella melitensis, other intracellular pathogens (32,100). In addition, this same type response occurs in humans but it is more difficult to determine correlates of protection (99,197). In conclusion, the goal of a live attenuated vaccine for Francisella is to stimulate an antibody, CD4 + , and CD8 + T cell responses without causing too much inflammation so that the T cell response is not overwhelmed.…”