Autoimmune Pulmonary Alveolar Proteinosis Following Pulmonary Aspergillosis

The ouroboros of autoimmunity

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

Opportunistic Infection Associated with Elevated GM-CSF Autoantibodies: A Case Series and Review of the Literature

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to play a key role in enhancing multiple immune functions that affect response to infectious pathogens including antigen presentation, complement- and antibody-mediated phagocytosis, microbicidal activity, and neutrophil chemotaxis. Reduced GM-CSF activity and immune response provides a mechanism for increased infection risk associated with autoimmune pulmonary alveolar proteinosis (aPAP) and other disorders involving the presence of GM-CSF autoantibodies. We present a case series of five patients with persistent or unusual pulmonary and central nervous system opportunistic infections (Cryptococcus gattii, Flavobacterium, Nocardia) and elevated GM-CSF autoantibody levels, as well as 27 cases identified on systematic review of the literature.

Human autoantibodies underlying infectious diseases

The vast interindividual clinical variability observed in any microbial infection-ranging from silent infection to lethal disease-is increasingly being explained by human genetic and immunological determinants. Autoantibodies neutralizing specific cytokines underlie the same infectious diseases as inborn errors of the corresponding cytokine or response pathway. Autoantibodies against type I IFNs underlie COVID-19 pneumonia and adverse reactions to the live attenuated yellow fever virus vaccine. Autoantibodies against type II IFN underlie severe disease caused by environmental or tuberculous mycobacteria, and other intra-macrophagic microbes. Autoantibodies against IL-17A/F and IL-6 are less common and underlie mucocutaneous candidiasis and staphylococcal diseases, respectively. Inborn errors of and autoantibodies against GM-CSF underlie pulmonary alveolar proteinosis; associated infections are less well characterized. In individual patients, autoantibodies against cytokines preexist infection with the pathogen concerned and underlie the infectious disease. Human antibody-driven autoimmunity can interfere with cytokines that are essential for protective immunity to specific infectious agents but that are otherwise redundant, thereby underlying specific infectious diseases.

Fungal immunology in clinical practice: Magical realism or practical reality?

Invasive fungal infections (IFIs) occur predominantly in immunocompromised individuals but can also be seen in previously well persons. The human innate immune system recognizes key components of the fungal cell wall as foreign resulting in a myriad of signaling cascades. This triggers release of antifungal molecules as well as adaptive immune responses, which kill or at least contain the invading fungi. However, these defences may fail in hosts with primary or secondary immunodeficiencies resulting in IFIs. Knowledge of a patient's immune status enables the clinician to predict the fungal infections most likely to occur. Moreover, the occurrence of an opportunistic mycosis in a patient without known immunocompromise usually should prompt a search for an occult immune defect. A rapidly expanding number of primary and secondary immunodeficiencies associated with mycoses has been identified. An investigative approach to determining the nature of these immunodeficiencies is suggested to help guide clinicians encountering patients with IFI. Finally, promising adjunctive immunotherapy measures are currently being investigated in IFI.

Temporary remission of autoimmune pulmonary alveolar proteinosis after infectious episodes

Pulmonary alveolar proteinosis (PAP) is a rare disease of unknown aetiology. Although resolution occurs in about 30% of autoimmune PAP (APAP) cases, its pathogenesis is not yet sufficiently understood. Two APAP cases at our institute showed remission following infectious episodes. Case 1: a 40-year-old female APAP patient suffered from herpes encephalitis and was treated with an antiviral drug. Her symptoms and radiological results resolved within two months of her recovery from the encephalitis. Case 2: A 53-year-old male current-smoker APAP patient was admitted for pneumonia. After treatment with antibiotics, his radiological results and symptoms improved. He experienced a similar resolution of APAP after another infectious episode two years later. Remission of APAP may occur following viral or bacterial infection. We hypothesise that remission of APAP is triggered by the induction of granulocyte-macrophage colony-stimulating factor (GM-CSF) following viral or bacterial infection. Further studies of APAP remission, and especially of the effects of GM-CSF induction, are needed. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 85-90).