dioides, given the differences in pathogenesis and pathophysiology between the two diseases.
Another potential antigen that has been isolated from the soluble fraction of C. immitis is HPPD, an enzyme that is involved in the degradation of aromatic amino acids and the production of pigments. The gene for HPPD is highly conserved from bacteria to humans, and that of coccidioides is about 50 percent identical to the human gene. Researchers have sequenced and cloned the gene and demonstrated that HPPD can evoke a proliferative response in mice immunized with coccidioides. At present, however, there are no data on the protective efficacy of either of these antigens.
Problems in Developing Fungal Vaccines. As with other vaccines, an important question is whom to vaccinate. Clinicians don’t know at what age these diseases are acquired. Another important question is when to vaccinate. Because cell-mediated immunity is primary, the timing of interdiction is crucial.
In response to questions from the audience, Dr. Deepe added the following:
Spherulin, the spherule-based vaccine against coccidioides that was developed 10 or so years ago, does not contain hsp 60. There are questions about its efficacy and side effects, but extensive animal studies have been done and the results of randomized clinical trials were published about 12 months ago.
One of the differences between the two pathogens is the importance of neutrophils in the histopathology of Coccidioides immitis. By the time there are symptoms and biopsies for histoplasmosis, however, there is no sign of neutrophils.
Incidence and Burden. Group A streptococcus bacteria cause a wide array of clinical syndromes, ranging from the uncomplicated streptococcal pharyngitis (a very common infection among young children) and streptococcal pyoderma at one extreme, to necrotizing fasciitis, “flesh-eating” pyomyositis, and the newly described streptococcal toxic shock syndrome at the other. The resurgence of serious Group A streptococcal infections has provided a new impetus for the development of vaccines, but the major driving force over the years has been the acute rheumatic fever and chronic rheumatic carditis that can follow Group A infection, causing significant morbidity and mortality.
The past 10 years have seen a significant change in the epidemiology of Group A streptococcal infections in the United States and Europe. In certain U.S. cities, for example, the incidence of rheumatic fever has jumped from 1 per