Building of an animal model of pulmonary cryptococcosis infection and diagnostic value of cryptococcal antigenlateral flow assay, 1-3-beta-d-glucan test, Glactomannan test

Objective To build of an animal model of pulmonary cryptococcosis infection and assess the value of the cryptococcal antigen (Crag) lateral flow assay (LFA), 1-3-beta-d-glucan test (G-test), glactomannan test (GM-test) to pulmonary cryptococcosis. Methods Thirty-six adult New Zealand white rabbits were randomly divided into the three group: immunosuppressed group (n=20), immunocompetent group (n=10) and control group (n=6). The immunosuppressed and immunocompetent group inoculate soliquoid of cryptococcus neoformans via trachea by tracheal intubation.The control group injected the same dose of saline by the same way.In the immunosuppressive group, cytarabine was injected intravenously on the day of 1~5, then maintained immunosuppressive state one time every other day; On the fourth day, vancomycin and cephalosporin were given one time a day, and one time gentamicin was administered intravenously every other day to prevent bacterial infection.Immunocompetent group and control group animals didn′t inject any drug.Then, CT scan was performed at one week after inoculation or before execution.We draw venous blood from the fringe of ear for cryptococcal antigen lateral flow assay, G-test and GM-test before the rabbits killed.Getting lung from rabbits for tissue culture, tissue pathology and bronchoalveolar lavage fluid(BALF). Cryptococcal antigen concentration of BALF was detected by lateral flow assay. Results The positive rate of Chest CT was 75%(15/20) in immunosuppressed group and 20%(2/10) in immunocompetent group, meanwhile the immunosuppressed group showed a variety of manifestations, such as ground glass and porphyry shadow, thickening of the bronchobronchial bundles, and nodules, and the main presence of immunocompetent group was nodules.All immunosuppressed rabbits′ lung tissue culture showed presence of cryptococcus neoforman, while immunocompetent group showed two three of ten presence of cryptococcus neoforman.Pathological changes were detected in 80%(16/20) of immunosuppressed group, and in 30%(3/10) of immunocompetent group.Achievementratio of modeling in immunosuppressed group was 80% and in immunocompetent group was 30%.All tests in the control group were negative.The specificity of serum and BALF of the lateral flow assay were 100% and 82.35% respectively, meanwhile the sensitivity were 89.47% and 100%.It showed significant difference between the two groups.All of the results of G-test and GM-test were negative. Conclusions Immunosuppressed individuals are more susceptible to pulmonary cryptococcosis infection than those who are healthy individuals.The diagnostic value of lateral flow assay, both in serum and BALF, are very high both sensitivity and specificity in pulmonary cryptococcosis, especially when the two used together.G-test and GM-test are negative in pulmonary cryptococcosis. Key words: Cryptococcus; Pulmonary cryptococcosis; Animal model; Cryptococcal antigen lateral flow assay; 1-3-beta-d-glucan test; Glactomannan test