Abstract
Human Parainfluenza Virus-3 (HPIV3) causes severe respiratory illness in immunocompromised patients and lacks approved anti-viral therapies. A phase I study of adoptively transferred virus-specific T-cells (VSTs) targeting HPIV3 following bone marrow transplantation is underway (NCT03180216). We sought to identify immunodominant epitopes within HPIV3 Matrix protein and their cross-reactivity against related viral proteins. VSTs were generated from peripheral blood of healthy donors by ex-vivo expansion after stimulation with a 15-mer peptide library encompassing HPIV3 matrix protein. Epitope mapping was performed using IFN-γ ELIspot with combinatorial peptide pools. Flow cytometry was used to characterize products with intracellular cytokine staining. In 10 VST products tested, we discovered 12 novel immunodominant epitopes. All products recognized an epitope at the C-terminus. On IFN-γ ELISpot, individual peptides eliciting activity demonstrated mean IFN-γ spot forming units per well (SFU)/1x105 cells of 115.5 (range 24.5–247.5). VST products were polyfunctional, releasing IFN-γ and TNF-α in response to identified epitopes, which were primarily HLA Class II restricted. Peptides from Human Parainfluenza Virus-1 corresponding to the HPIV3 epitopes showed cross-reactivity for HPIV1 in 11 of 12 tested epitopes (mean cross reactivity index: 1.19). Characterization of HPIV3 epitopes may enable development of third-party VSTs to treat immune suppressed patients with HPIV infection.
Highlights
Viral infections remain a major cause of morbidity and mortality in patients following hematopoietic stem cell transplantation (HSCT)
All 10 products showed specificity for Human Parainfluenza Virus-3 (HPIV3) Matrix protein (Average IFN-g spot forming units per well (SFU) 319.8/1x105 cells) versus actin, an irrelevant antigen used as negative control. (SFU 0.5/ 1x105 cells) (Figure 1B) In silico testing (Immune Epitope Database, IEDB.org) predicted that all 10 peptides would have MHC class II restricted responses primarily mediated through HLA-DRB1 alleles (Table 1), and when stimulated with Matrix peptides, all products demonstrated a CD4+ response
Human parainfluenza virus infections in immunocompromised patients remain a significant cause of morbidity and mortality and lack specific anti-viral treatment
Summary
Viral infections remain a major cause of morbidity and mortality in patients following hematopoietic stem cell transplantation (HSCT). Respiratory viruses, including human parainfluenza virus, can cause significant pulmonary disease and pneumonias in immunocompromised patients [1]. Human parainfluenza virus 3 (HPIV3) is the most common serotype and is detected in 90% of infected patients. For patients with primary immunodeficiency disorders (PIDD) or patients post-transplant, HPIV3 can cause fatal pneumonia in up to 45% of infected patients [2, 3]. Ribavirin and intravenous gamma globulin have been largely ineffective in lowering mortality, and currently, there are no effective anti-viral therapies nor approved vaccines for parainfluenza infections. Treatment remains primarily symptom-based [4]
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