Efficacy of the combination of voriconazole and caspofungin in experimental pulmonary aspergillosis by different Aspergillus species.

OBJECTIVES: Invasive pulmonary aspergillosis (IPA) caused by Aspergillus fumigatus, Aspergillus flavus, or Aspergillus niger is associated with high mortality. We evaluated the efficacy and compared the therapeutic effect differences of voriconazole (VRC) in combination with caspofungin (CAS) in transiently neutropenic rats infected by A. fumigatus, A. flavus, or A. niger. METHODS: Treatment groups consisted of VRC (10 mg/kg q12 h) monotherapy, CAS (1 mg/kg/day) monotherapy, combination of VRC (10 mg/kg q12 h) + CAS (1 mg/kg/day), and no drug for 10 consecutive days. The efficacy and the difference in the treatments were evaluated through prolongation of survival, reduction in serum galactomannan levels and residual fungal burden, and histological studies. RESULTS: For all the strains, the combination of VRC and CAS led to significant prolongation in survival (P < 0.05) and reduction in residual fungal burden (P < 0.05) compared with CAS alone, and decrease in serum galactomannan levels (P < 0.05) compared with either agent alone. The survival in the combined therapy groups was significantly improved compared to VRC monotherapy for the strains of A. flavus and A. niger (P < 0.05), but no significant difference for the strains of A. fumigatus (P > 0.05). CONCLUSIONS: Combination of VRC and CAS was synergistic in IPA by A. flavus and A. niger, but small efficacy benefits in IPA by A. fumigatus.

Therapy of murine pulmonary aspergillosis with antibody-alliinase conjugates and alliin.

Aspergillus fumigatus is an opportunistic fungal pathogen responsible for invasive aspergillosis in immunocompromised individuals. The high morbidity and mortality rates as well as the poor efficacy of antifungal agents remain major clinical concerns. Allicin (diallyl-dithiosulfinate), which is produced by the garlic enzyme alliinase from the harmless substrate alliin, has been shown to have wide-range antifungal specificity. A monoclonal antibody (MAb) against A. fumigatus was produced and chemically ligated to the enzyme alliinase. The purified antibody-alliinase conjugate bound to conidia and hyphae of A. fumigatus at nanomolar concentrations. In the presence of alliin, the conjugate produced cytotoxic allicin molecules, which killed the fungus. In vivo testing of the therapeutical potential of the conjugate was carried out in immunosuppressed mice infected intranasally with conidia of A. fumigatus. Intratracheal (i.t.) instillation of the conjugate and alliin (four treatments) resulted in 80 to 85% animal survival (36 days), with almost complete fungal clearance. Repetitive intratracheal administration of the conjugate and alliin was also effective when treatments were initiated at a more advanced stage of infection (50 h). The fungi were killed specifically without causing damage to the lung tissue or overt discomfort to the animals. Intratracheal instillation of the conjugate without alliin or of the unconjugated monoclonal antibody significantly delayed the death of the infected mice, but only 20% of the animals survived. A limitation of this study is that the demonstration was achieved in a constrained setting. Other routes of drug delivery will be investigated for the treatment of pulmonary and extrapulmonary aspergillosis.