Biomedical Engineering Reference
In-Depth Information
respiratory distress syndrome, is comparable to the mechanism of tumor
cell metastasis. h e sulfated derivatives of chitosan also exhibit antiviral
ef ects. Many plant viral pathogens are inhibited by chitosan [140, 141].
6.7
Chitosan as Adjuvant
h is immunostimulating activity along with the structural similarities
between chitin derivatives and glucans, an immunoadjuvant class of natu-
ral polysaccharides, led several scientists to study the adjuvant capabilities
of chitosan.
Nishimura,
et al.
, formulated various chitin derivatives with antigen
and incomplete Freund's adjuvant (IFA) to measure adaptive immune
responses in guinea pigs and mice [142]. 30 and 70 % deacetylated chi-
tins were active adjuvants for the circulating-antibody formation to bac-
terial a-amylase and for the induction of delayed type hypersensitivity
to azobenzenearsonate-N-acetyl-L-tyrosine. 70 % deacetylated chitin
enhanced the helper T-cell functions, the generation of alloreactive cyto-
toxic T-lymphocytes, and the activity of natural killer cells in mice. Other
derivatives of chitin as carboxymethyl-, hydroxyethyl and dihydroxypro-
pyl-chitin showed weaker or no adjuvant activity compared with 70 %
deacetylated chitin.
In other studies, this chitin derivative induced protection against the
Sendai virus, when it was nasally administered prior to virus infection.
Macrophages might have played an important role in the induction of this
protection [143]. Marcinkiewicz,
et al.
, found that intraperitoneal admin-
istration of a water insoluble chitosan suspension enhanced humoral
responses, but not cell-mediated immune responses in mice [144].
Subcutaneous administrations of chitosan suspensions were found to be
inef ective. Seferian and Martinez found that chitosan particles, formu-
lated in an emulsion with antigen, squalene and Pluronic L121, gave a
prolonged, high antigen-specii c antibody titer and sensitised animals for
antigen-specii c delayed hypersensitivity responses, following an intraperi-
toneal injection [145]. Chitosan particles alone of ered no enhancement of
an adaptive immune response.
Zaharof ,
et al.
, explored chitosan solution as an adjuvant for subcutaneous
vaccination of mice with a model protein antigen. Chitosan enhanced anti-
gen specii c antibody titers over i ve-fold and antigen-specii c splenic CD4
+
proliferation over six-fold. Strong increases in antibody titers, together with
robust delayed hypersensitivity responses, revealed that chitosan induced
both humoral and cell-mediated immune responses. When compared with
