Monoclonal antibodies for diagnosis and prophylaxis of invasive Aspergillosis

Abstract

Aspergillus fumigatus is a saprophytic fungus that is the primary etiologic agent causing invasive aspergillosis (IA), a deadly mold disease that affects patients with severely compromised immune systems. Two major clinical challenges are timely and accurate diagnosis, and adequate therapeutic agents.;Early diagnosis of IA is associated with improved patient outcome. We sought to develop a monoclonal antibody-based (MAb) diagnostic platform for more sensitive early detection assays. Our work focused on exploiting the lack of study of protein antigens as biomarkers. We used a bottom-up protein-profiling strategy to analyze blood and lung fluids from mice with IA and fungal asthma for proteins unique to IA. We were unable to identify A. fumigatus proteins in mice, and subsequently began working with human BALF as part of an ongoing prospective study. We have identified and confirmed at least six A. fumigatus proteins in a patient with probable IA. Currently these proteins are being evaluated as potential biomarkers for IA.;Treatment or prophylaxis with currently available antifungal agents is often inadequate, as mortality remains high despite therapeutic intervention. A. fumigatus germination in the absence of host immunity is required for establishing invasive disease. Therefore, we used vaccination with whole A. fumtigatus conidia to make a germination-inhibitory IgM, MAb 318. MAb 318 prophylaxis of neutropenic mice administered as repeated intranasal injection prior to lethal challenge, resulted in 60% survival and reduced lung fungal burden. In vitro studies showed that MAb 318 binding to conidia resulted in delayed germination with severely stunted hyphae, and also altered the interaction between alveolar macrophages and conidia. MAb 318 binds to mycelial catalase and two aldehyde dehydrogenases, the latter are 79% identical, but MAb 318 maintained the capacity to inhibit germination in both single and double mutants. We also discovered that these proteins do not compete for MAb 318 binding, and that at least one protein, Aid has binding characteristics similar to the bacterial superantigen protein A. The mechanism underlying MAb 318 protection in mice and in vitro inhibition of germination remains unclear, more exploration is required.