The high mortality rates of patients with invasive aspergillosis despite antifungal therapy and the dependence of clinical response on host immune status make the development of immunotherapy desirable. Though the antibody response to A. fumigatus is not believed to be important in naturally occurring immunity, the possibility that protective antibodies can be identified remains. Germination of inhaled conidia is a key step in the establishment of invasive aspergillosis. To block this process, BALB/c mice were immunized intraperitoneally with 10 7 heat-killed conidia of A. fumigatus strain 293 every two weeks for five doses and conidia surface binding antibody titers were measured by ELISA. Germination assays were performed by incubating 10 6 conidia in wells of 96-well tissue culture plates in medium containing 10% NCTC, 1% non-essential amino acids and 1% penicillin/streptomycin at 37°C with 10% CO2 for 8 h. After the fifth immunization, mice had conidia surface binding antibody titers that ranged from 1:6400-1:52,600. Most of the antibody measured was of the IgM class, though lower amounts of IgG subclasses were detectable. While pre-immune serum from five of six mice significantly enhanced the rate of germination, immune serum from three of four mice significantly reduced it. The inhibition of germination was abrogated by heating of immune serum at 37°C for 30 min, demonstrating dependence upon a heat labile serum factor. Ability of immune serum to inhibit germination was restored by the addition of fresh BALB/c serum, as well as by the addition of serum from A/JCr mice, which do not secrete C5, indicating that neither C5 nor terminal complement components are likely to be involved in the mechanism of inhibition. Conclusion: immunization with conidia induces the development of an antibody response that, in conjunction with a heat-labile serum factor, inhibits germination.
Full conference title:
The 15 th Congress of the International Society for Human and Animal Mycology
- ISHAM 15th (2003)