title: Introducing point and deletion mutations into the P/C gene of human parainfluenza virus type 1 (HPIV1) by reverse genetics generates attenuated and efficacious vaccine candidates.
abstract: The P/C gene of human parainfluenza virus type 1 (HPIV1) encodes a nested set of related accessory C proteins, C'/C/Y1/Y2, which have been shown in other paramyxoviruses to have a role in evasion of the type I interferon (IFN) response following virus infection. We previously demonstrated that a set of two amino acid substitutions, CR84G/HNT553A, and a separate amino acid substitution, CF170S, are independently attenuating for HPIV1 in African green monkeys (AGMs). However, in each case the attenuation (att) phenotype is vulnerable to reversion by a single nucleotide change back to wild type. Using reverse genetics, recombinant HPIV1 (rHPIV1) vaccine candidates were generated that were designed for increased genetic and phenotypic stability by: (i) creating a two-amino acid deletion and substitution at the site of the CF170S mutation, yielding CDelta170; (ii) introducing a six amino acid deletion in the N-terminal region of C, CDelta10-15; and (iii) combining these stable deletion mutations with the att CR84G/HNT553A mutation. The resulting rHPIV1 vaccine candidates were evaluated for attenuation in hamsters and AGMs and for immunogenicity and protective efficacy in AGMs. The CDelta10-15 mutation was attenuating in hamsters but not in AGMs, and likely will be of limited value for an HPIV1 vaccine. Conversely, the CR84G/HNT553A mutation set was attenuating in AGMs but not in hamsters. Thus, these two mutations demonstrated reciprocal host range phenotypes involving different regions of C. The CDelta170 mutation conferred a significant level of attenuation in hamsters and AGMs that closely resembled that of CF170S and will be of particular utility for vaccine development because it involves a deletion of six nucleotides rendering it highly refractory to reversion. The combination of the CR84G/HNT553A mutation set and the CDelta170 deletion mutation yielded a virus, rCR84G/Delta170 HNT553A, that exhibited a satisfactory level of attenuation in hamsters and AGMs and was immunogenic and highly protective against HPIV1 wt challenge. This virus will be evaluated clinically as a live intranasal HPIV1 vaccine, one that can be further attenuated as necessary by the introduction of additional stabilized att mutations previously developed in the L protein.
authors.affiliation: Laboratory of Infectious Diseases, Respiratory Viruses Section, National Institute of Allergy and Infectious Diseases, National Institute of Health, Department of Health and Human Services, Bethesda, MD 20892-8007, USA. EBartlett@niaid.nih.gov
authors.forename: Emmalene J
authors.initials: EJ
authors.lastname: Bartlett
authors.forename: Emerito
authors.initials: E
authors.lastname: Amaro-Carambot
authors.forename: Sonja R
authors.initials: SR
authors.lastname: Surman
authors.forename: Peter L
authors.initials: PL
authors.lastname: Collins
authors.forename: Brian R
authors.initials: BR
authors.lastname: Murphy
authors.forename: Mario H
authors.initials: MH
authors.lastname: Skiadopoulos
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D006801:Humans; D022241:Parainfluenza Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D010222:Parainfluenza Virus 1, Human / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D017354:Point Mutation; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*
chemical_list: D022241:Parainfluenza Vaccines; D014613:Vaccines, Attenuated