# CRYPTOCOCCAL POLYSACCHARIDE--INHIBITION OF PHAGOCYTOSIS

> **NIH NIH R01** · UNIVERSITY OF NEVADA RENO · 1992 · $191,058

## Abstract

Cryptococcosis is a serious infectious disease in the
immunocompromised patient.  It is the third most common serious
infectious complication of AIDS.  The capsule is arguably the
most important virulence factor produced by Cryptococcus
neoformans.  Our studies focus on the manner in which the capsule
influences phagocytosis of the yeast by human mononuclear
phagocytes.

Studies during the current grant period have shown that
incubation of encapsulated cryptococci in normal human serum
leads to deposition of large amounts of iC3b and smaller amounts
of IgG within and at the surface of the capsule.  iC3b and the
IgG in normal human serum act synergistically to mediate
phagocytosis of the yeast.  Conversely, phagocyte receptors for
iC3b (CR3) and IgG (FcR) are essential for optimal phagocytosis.
These studies have also shown that encapsulated isolates are not
all alike and differ with regard to their relative resistance to
phagocytosis.  An explanation of the cellular and molecular basis
for these differences is central to this proposal.

The overall hypothesis for this proposal is that phagocytosis of
encapsulated cryptococci is critically dependent on the opsonic
action of iC3b and IgG and their respective membrane receptors
(CR3 and FcR).  The proper functioning of these systems will
determine whether or not the yeast is ingested.  This hypothesis
will be pursued by the study of three specific aims.  The first
aim will characterize the anti-capsular antibody found in normal
human serum.  The second aim will examine activation and binding
of opsonic C3 fragments by the cryptococcal capsule.  The third
aim will examine the mechanism for inhibition of phagocytosis by
the cryptococcal capsule by comparing the properties of
phagocytosis-resistant and phagocytosis-sensitive encapsulated
isolates.

These studies will contribute to understanding the mechanism by
which capsules function as anti-phagocytic surface structures and
will facilitate an understanding of the pathogenesis of an
increasingly important opportunistic pathogen.

## Key facts

- **NIH application ID:** 3125684
- **Project number:** 5R01AI014209-14
- **Recipient organization:** UNIVERSITY OF NEVADA RENO
- **SAM.gov UEI:** WLDGTNCFFJZ3
- **Principal Investigator:** Thomas R Kozel
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1992
- **Award amount:** $191,058
- **Award type:** 5
- **Project period:** 1977-07-01 → 1994-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3125684

## Citation

> US National Institutes of Health, RePORTER application 3125684, CRYPTOCOCCAL POLYSACCHARIDE--INHIBITION OF PHAGOCYTOSIS (5R01AI014209-14). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3125684. Licensed CC0.

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