Galactomannan and (1→3)-β-D-glucan are useful
biomarkers of
invasive pulmonary aspergillosis (IPA). However, the effects of immunosuppression on levels of
galactomannan or (1→3)-β-D-glucan in IPA are not well understood or quantified. We therefore studied the simultaneous levels of
galactomannan and (1→3)-β-D-glucan in two rabbit models of experimental IPA: (1) AraC-induced
neutropenia in untreated (UC-AraC) and
liposomal amphotericin B-treated (LAMB-AraC) rabbits; and (2) nonneutropenic
cyclosporine-
methylprednisolone immunosuppression in untreated (UC-CsA+M) and LAMB-treated (LAMB-CsA+M) rabbits. Simultaneous levels of
galactomannan and (1→3)-β-D-glucan were determined in bronchoalveolar lavage (BAL) fluid and serial serum specimens and correlated with pulmonary host response. Serum
galactomannan index (GMI) and (1→3)-β-D-glucan concentration-time-curves were higher in UC-AraC vs. UC-CsA+M (Mann-Whitney U-test, P < .05). Serum
galactomannan and (1→3)-β-D-glucan in treatment groups demonstrated therapeutic responses with similarly lower levels in comparison to UC (P < .01) in both models. Host differences did not affect BAL fluid GMI or (1→3)-β-D-glucan but did affect
galactomannan and (1→3)-β-D-glucan levels in serum. The higher serum GMI and (1→3)-β-D-glucan concentration-time-curves in UC-AraC correlated with extensive pulmonary infiltration by angioinvasive hyphae and minimal
inflammation, while the lower concentration-time-curves in UC-CsA+M were associated with shorter and fewer hyphae in lung tissue and an intensive neutrophil response to Aspergillus hyphae. Thus, serum levels of
galactomannan and (1→3)-β-D-glucan in IPA depended upon immunosuppression, which also affected severity of
infection and hyphal morphology, while BAL fluid
galactomannan and (1→3)-β-D-glucan were sensitive
biomarkers not affected by host response.