title: Identification of amino acid substitutions with compensational effects in the attachment protein of canine distemper virus.
abstract: The hemagglutinin (H) gene of canine distemper virus (CDV) encodes the receptor-binding protein. This protein, together with the fusion (F) protein, is pivotal for infectivity since it contributes to the fusion of the viral envelope with the host cell membrane. Of the two receptors currently known for CDV (nectin-4 and the signaling lymphocyte activation molecule [SLAM]), SLAM is considered the most relevant for host susceptibility. To investigate how evolution might have impacted the host-CDV interaction, we examined the functional properties of a series of missense single nucleotide polymorphisms (SNPs) naturally accumulating within the H-gene sequences during the transition between two distinct but related strains. The two strains, a wild-type strain and a consensus strain, were part of a single continental outbreak in European wildlife and occurred in distinct geographical areas 2 years apart. The deduced amino acid sequence of the two H genes differed at 5 residues. A panel of mutants carrying all the combinations of the SNPs was obtained by site-directed mutagenesis. The selected mutant, wild type, and consensus H proteins were functionally evaluated according to their surface expression, SLAM binding, fusion protein interaction, and cell fusion efficiencies. The results highlight that the most detrimental functional effects are associated with specific sets of SNPs. Strikingly, an efficient compensational system driven by additional SNPs appears to come into play, virtually neutralizing the negative functional effects. This system seems to contribute to the maintenance of the tightly regulated function of the H-gene-encoded attachment protein. Importance: To investigate how evolution might have impacted the host-canine distemper virus (CDV) interaction, we examined the functional properties of naturally occurring single nucleotide polymorphisms (SNPs) in the hemagglutinin gene of two related but distinct strains of CDV. The hemagglutinin gene encodes the attachment protein, which is pivotal for infection. Our results show that few SNPs have a relevant detrimental impact and they generally appear in specific combinations (molecular signatures). These drastic negative changes are neutralized by compensatory mutations, which contribute to maintenance of an overall constant bioactivity of the attachment protein. This compensational mechanism might reflect the reaction of the CDV machinery to the changes occurring in the virus following antigenic variations critical for virulence.
authors.affiliation: Centre for Fish and Wildlife Health (FIWI), Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Ursula
authors.initials: U
authors.lastname: Sattler
authors.affiliation: Division of Experimental and Clinical Research, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Khosravi
authors.affiliation: Division of Experimental and Clinical Research, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Mislay
authors.initials: M
authors.lastname: Avila
authors.affiliation: Institute of Veterinary Bacteriology (IVB), Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Paola
authors.initials: P
authors.lastname: Pilo
authors.affiliation: Crucell Holland BV, Leiden, The Netherlands.
authors.forename: Johannes P
authors.initials: JP
authors.lastname: Langedijk
authors.affiliation: Division of Experimental and Clinical Research, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Nadine
authors.initials: N
authors.lastname: Ader-Ebert
authors.affiliation: Division of Experimental and Clinical Research, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Alves
authors.affiliation: Division of Experimental and Clinical Research, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Plattet
authors.affiliation: Centre for Fish and Wildlife Health (FIWI), Vetsuisse Faculty, University of Bern, Bern, Switzerland Institute of Veterinary Bacteriology (IVB), Vetsuisse Faculty, University of Bern, Bern, Switzerland francesco.origgi@vetsuisse.unibe.ch.
authors.forename: Francesco C
authors.initials: FC
authors.lastname: Origgi
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000835:Animals, Wild; D015703:Antigens, CD / Q000378:metabolism; D004252:DNA Mutational Analysis; D004216:Distemper / Q000453:epidemiology / Q000821:virology; D004217:Distemper Virus, Canine / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology*; D005060:Europe / Q000453:epidemiology; D019143:Evolution, Molecular; D006389:Hemagglutinins, Viral / Q000235:genetics* / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism; D011991:Receptors, Virus / Q000378:metabolism; D000071177:Signaling Lymphocytic Activation Molecule Family Member 1; D013489:Suppression, Genetic; D014760:Viral Fusion Proteins / Q000378:metabolism; D053585:Virus Attachment
chemical_list: D015703:Antigens, CD; D006389:Hemagglutinins, Viral; D050505:Mutant Proteins; D011956:Receptors, Cell Surface; D011991:Receptors, Virus; D014760:Viral Fusion Proteins; C076619:F protein, Phocine distemper virus; D000071177:Signaling Lymphocytic Activation Molecule Family Member 1