Abstract Detection of Aspergillus Antigens in Experimental Invasive Aspergillosis using a Biotin-Avidin Linked Sandwich ELISA (BALISA)

^*Author for Correspondence.
Dept. Medical Microbiology & Immunology, Faculty of Medicine, UKM
Jalan Yaacob Latiff, 56000 Kuala Lumpur, Malaysia.
Tel: 603-91702208; Fax: 603-91737336
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Key words: Antigen detection, experimental invasive aspergillosis, sandwich ELISA

Abstract.
A biotin-avidin amplified sandwich ELISA utilizing polyclonal antibodies to water soluble (WS) mycelial antigens of Aspergillus fumigatus was used to detect antigens in sera of rabbits with experimental invasive aspergillosis. Tricolor rabbits were more susceptible to infection than NZW rabbits as evidenced by a faster progression of infection and greater isolation rates of A. fumigatus from organ culture. Antigenemia was detected in all 11 Tricolor rabbits inoculated with 1 x 10⁶ and 1 x 10⁷ conidia. However, antigenemia was detected in only 0%, 50% and 75% of NZW rabbits inoculated with 1 x 10⁶, 1 x 10⁷ and 1 x 10⁸ conidia, respectively. Tricolor rabbits demonstrated antigenemia in 75% (18 of 24) of sera, whilst only 36% (5 of 14) of sera of NZW rabbits tested positive. The overall sensitivity and specificity of antigen detection in Tricolor and NZW rabbits were 84.2% (16 of 19 rabbits) and 85.7% (12 of 14) respectively. The protein rich Concanavalin A unbound fraction of WS antigens demonstrated immunoreactivity with the BALISA. Immunoblot studies using the capture antibody demonstrated 3 strongly immunoreactive regions of 38-46kD, 66-68kD and 73-85kD for WS antigens. The results of partial characterization of WS antigens, suggests that the antigens detected are protein in nature.