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Cryptococcus neoformans: paradigm for the role of antibody immunity against fungi?
1Division of Infectious Diseases, Albert Einstein College of Medicine, Bronx, New York, USA.
Abstract:
Cryptococcus neoformans is an encapsulated fungus that is a frequent cause of life-threatening infections in patients with AIDS. C. neoformans has many similarities with encapsulated bacteria such as S. pneumoniae and H. influenzae for which antibody immunity is important in protection. However the role of antibody immunity in protection against C. neoformans has been controversial. Experiments with polyclonal sera have produced conflicting evidence for and against the importance of antibody immunity in host defense. Experiments with monoclonal antibodies (mAb) to the C. neoformans capsular polysaccharide (CPS) have revealed the existence of protective, non-protective and disease-enhancing mAbs, suggesting that the divergent results obtained with polyclonal preparations may be a result of relative proportion of protective and non-protective antibodies in immune sera. Administration of protective mAbs can prolong survival, decrease organ fungal burden, and reduce serum polysaccharide antigen. In vitro experiments suggests that protective mAbs modify the course of infection by enhancing effector cell function against C. neoformans. Addition of mAb to antifungal drugs enhances their efficacy against C. neoformans in vivo and in vitro. Human-mouse chimeric antibodies with activity against C. neoformans have been constructed. A highly immunogenic capsular polysaccharide-protein vaccine has been synthesized that elicits protective antibodies in mice. Antibody immunity elicited by conjugate vaccines or provided by passive administration may be useful in the prevention treatment of human cryptococcal infections.
Insights
Antibody immunity plays a crucial role in combating Cryptococcus neoformans infections, particularly in AIDS patients. Protective monoclonal antibodies (mAbs) and vaccines show promise for preventing and treating cryptococcal disease.
Area of Science:
- Mycology
- Immunology
- Infectious Diseases
Background:
- Cryptococcus neoformans causes life-threatening infections, especially in AIDS patients.
- Antibody immunity is vital for bacterial infections but its role in cryptococcal infections is debated.
- Previous studies with polyclonal sera yielded conflicting results on antibody protection.
Purpose of the Study:
- To investigate the role of antibody immunity in protection against Cryptococcus neoformans.
- To clarify the conflicting evidence regarding antibody's role in host defense.
- To explore therapeutic and prophylactic strategies involving antibodies.
Main Methods:
- Experiments using monoclonal antibodies (mAbs) against C. neoformans capsular polysaccharide (CPS).
- Administration of protective mAbs in vivo and in vitro studies.
- Development and testing of a capsular polysaccharide-protein conjugate vaccine in mice.
Main Results:
- Monoclonal antibodies showed varied effects: protective, non-protective, and disease-enhancing.
- Protective mAbs prolonged survival, reduced fungal burden, and decreased serum antigen.
- Antibody-antifungal drug combinations enhanced efficacy; a novel vaccine elicited protective antibodies in mice.
Conclusions:
- The efficacy of antibody immunity depends on the specific antibodies involved.
- Protective mAbs can enhance effector cell function against C. neoformans.
- Antibody-based strategies, including vaccines and passive immunotherapy, hold potential for cryptococcal infection management.