Pathogenesis, Lethality, and Immunizing Effect of Experimental Cutaneous Cryptococcosis

Abstract

Mice were subcutaneously inoculated with small numbers of virulent Cryptococcus neoformans and divided into groups. Numbers of viable yeasts at the site were estimated at weekly intervals for 5 weeks on the basis of cultures of minced tissue excised from sacrificed animals. Organisms multiplied at the site for at least 4 weeks and were still detectable after the 5th week, although in reduced numbers. Agglutinins appeared within a week, but these antibodies were not detectable during the 2nd through the 5th week. Cryptococcal polysaccharide began to appear in the sera at 3 weeks, persisting through the duration of 5 weeks. All animals appeared healthy, but a few sickened after many months and died of systemic cryptococcosis. All of these events were observed in many separate experiments. The immunizing capacity of a cutaneous lesion was tested by challenging some of the above animals with viable C. neoformans after various intervals of time, either subcutaneously at a site distant from that of the vaccination or intravenously. Although we were unable to demonstrate reduced multiplication of yeasts in the brains, lungs, and spleens of intravenously challenged animals, it was possible to show that multiplication was inhibited at the site of subcutaneous challenge. It was noted also that vaccinated animals lived longer after lethal intravenous challenge than did nonvaccinated animals. The latter protection was observed, however, only when challenge followed vaccination by 3 weeks or longer, and it was effective only against a relatively low challenge dose. Mice were protected against a higher dose if they had previously received killed cryptococci, alternating subcutaneous and intraperitoneal inoculations, one of which contained a microbial adjuvant. No protection was observed in animals that were subcutaneously vaccinated with inert materials such as chitin, latex spheres, or even cryptococcal cell walls themselves.

Monoclonal antibodies to Cryptococcus neoformans capsular polysaccharide modify the course of intravenous infection in mice

“…(59) infection, and variation is also apparent in the data reported by other investigators (18,56,67). The variation may reflect the fact that some mice limit the spread of infection, possibly by developing an effective cell-mediated response (18,37,56) or escaping from immunologic paralysis and producing an antibody response (5). Individual variation within lots of inbred mice is an important consideration in the design of antibody protection experiments because it increases the difficulty of demonstrating statistically significant differences between groups.…”

Cryptococcal culture filtrate antigen for detection of delayed-type hypersensitivity in cryptococcosis

“…FIG. 3. Guinea pig skin test results using as antigens the XM50, PM30, and UMO residues and the UM 0 filtrate obtained according to procedure 2 (Fig.…”

Cellular Immunity in a Cutaneous Model of Cryptococcosis

“…The temporal development of DH in mice infected with C. neoformans has been followed successfully by others (5,20) and unsuccessfully in at least one investigation (8). In this last investigation, mice were infected subcutaneously and were footpad tested with the antigen of Murphy et al (27) or of Atkinson and Bennett (1).…”

“…In recent years, there has been a flurry of interest in cryptococcosis, especially with respect to the development of model animal systems in which immune responses, including resistance to reinfection and the production of antibody and cell-mediated responses, can be demonstrated in vivo or in vitro. In the development of the various models, some individuals have stimulated their animals with extracellular products (16,17,28); others have used nonviable (1, 2, 13) or viable (3,8,(18)(19)(20)27) cells administered by various routes with or without adjuvant; and still others have immunized with avirulent mutants and challenged with virulent wild-type strains (9,10). We recently published our contribution to this area in the form of a murine model of cryptococcosis involving the inoculation of viable cryptococci cutaneously followed by intravenous challenge and subsequent organ culture to assess potential protective responses (25).…”