Clinical and Diagnostic Laboratory Immunology, March 1998, p. 125-129, Vol. 5, No. 2
Department of Microbiology and
Immunology1 and
Department of
Medicine,2 Albert Einstein College of
Medicine, Bronx, New York 10461
Received 15 September 1997/Returned for modification 5 December
1997/Accepted 18 December 1997
Cryptococcus neoformans var. neoformans
strains have historically been divided into serotypes A and D on the
basis of reactivity with rabbit sera. Previously, we noted that two
murine immunoglobulin M monoclonal antibodies (MAbs) to
the capsular glucuronoxylomannan produced different indirect
immunofluorescence (IF) patterns, described as annular and punctate,
when bound to C. neoformans cells from different strains.
In this study, we examined the reactivity of these two MAbs, known as
12A1 and 13F1, with 20 C. neoformans var.
neoformans strains, of which 13 were serotype A and 7 were serotype D. For all strains, MAb binding was studied by IF and agglutination assays. In addition, we blindly tested the IF patterns of
22 C. neoformans var. neoformans strains. For
selected strains, MAb binding was studied by flow cytometry (FACScan)
and phagocytosis assays. The epitopes recognized by MAbs 12A1 and
13F1 were found in all of the strains. MAb 12A1
binding produced an annular IF pattern with all of the
strains, irrespective of the serotype classification. MAb 13F1 binding
produced annular binding with all of the serotype A strains and
punctate binding with 19 of 20 serotype D strains. In general, the
punctate IF pattern was associated with lower fluorescence intensity,
a requirement for higher antibody concentrations to produce
yeast cell agglutination, and lower opsonic efficacy.
Our results provide strong support for the existing classification of
two serological types for strains assigned to variety
neoformans and indicate qualitative and quantitative antigenic differences among serotype A and D strains.
1071-412X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
The Different Binding Patterns of Two Immunoglobulin M Monoclonal
Antibodies to Cryptococcus neoformans Serotype A and D
Strains Correlate with Serotype Classification and Differences
in Functional Assays
*
Corresponding author. Mailing address: 1300 Morris Park
Ave., Golding Rm. 701, Bronx, NY 10461. Phone: (718) 430-4259. Fax: (718) 430-8968. E-mail: casadeva{at}aecom.yu.edu.
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