Bacterial infection modulated by glucan: A search for the host defense potentiation mechanisms

Abstract

Interactions between bacteria and the host were studied from day 0 up to day 10 post-challenge in mice pretreated with soluble glucan (20 mg/kg i.p.) and challenged supralaryngeally with a virulent strain of Klebsiella pneumoniae. In the initial phase of infection, clearance of bacteria in the airways of glucan-treated mice was improved to an extent comparable with the vaccinated group but, in contrast to the immunized animals, subsequent regrowth of the bacterial inoculum was not prevented. The efficacy of defense, based during the entire course of infection mainly upon phagocytosis by neutrophils, markedly increased at intervals corresponding to the onset of humoral immune response. No evidence was obtained to indicate an enhanced involvement of alveolar macrophages in the phagocytosis of bacteria in glucan-stimulated mice. The results further support the notion that improvement of specific immune responsiveness rather than activation of nonspecific effector functions might be the most important expression of the host-defense-potentiating capacity of glucan and related stimulants of microbial origin.

An Extract of the Mushroom Agaricus blazei Murill Administered Orally Protects Against Systemic Streptococcus pneumoniae Infection in Mice

“…These in vivo effects were observed after parenteral injection of the polysaccharides but not confirmed in the S. pneumoniae model after oral administration. Because AbM [9,10], similarly to b-glucans [22,23], has antitumour effects, and b-glucans also have anti-infection effects [20,24,25], the aims of the present study were to examine whether AbM extract protects against systemic S. pneumoniae infection in a mouse model and to examine the effect of a water extract of AbM administered orally against infections with the moderately virulent S. pneumoniae serotype 6B. End points were peripheral bacteraemia and survival rate of the animals.…”

Mould extracts increase the allergic response to ovalbumin in mice

“…b-glucans are glucose polymers present as structural constituents in the cell wall of some bacteria, plants, yeast and fungi. The effects of b-glucans on the immune system include anti-tumour [13] and anti-infective [14][15][16] activities in animals. Furthermore, b-glucans have harmful effects on respiratory health.…”

Effect of glucan on murine lupus evolution and on host resistance toKlebsiella pneumoniae

“…Glucan as a nonspecific stimulant of the MPS enhances host resistance to infections and neoplasms (8,9,15,22,23). The use of immunostimulants is of controversial value in autoimmune diseases like lupus.…”

“…β-1,3 glucan is derived from the common yeast Saccharomyces cerevisiae cell wall (6) and influences the host defense mechanisms by means of MPS activation (7)(8)(9). Glucan increases the phagocytic function and macrophage proliferation (7,10), modifies the intravascular clearance and tissue distribution of soluble and particulate antigens (11), and induces the production of cytokines (12) and prostaglandins (13).…”