Organization and Expression Strategy of the Ambisense Genome of Densonucleosis Virus of Galleria mellonella

ABSTRACT The expression strategy of parvoviruses of the Densovirus genus has as yet not been reported. Clones were obtained from the densonucleosis virus of Galleria mellonella (GmDNV) that yielded infectious virus upon transfection into LD652 cells. Its genome was found to be the longest (6,039 nucleotides [nt]), with the largest inverted terminal repeats (ITRs) (550 nt) among all parvoviruses. The distal 136 nt could be folded into hairpins with flop or flip sequence orientations. In contrast to vertebrate parvoviruses, the gene cassettes for the nonstructural (NS) and structural (VP) proteins were found on the 5′ halves of the opposite strands. The transcripts for both cassettes started 23 nt downstream of the ITRs. The TATA boxes, as well as all upstream promoter elements, were localized in the ITRs and, therefore, identical for the NS and VP transcripts. These transcripts overlapped for 60 nt at the 3′ ends (antisense RNAs) at 50 m.u. The NS cassette consisted of three genes of which NS2 was contained completely within NS1 but from a different reading frame. Most of the NS transcripts were spliced to remove the upstream NS3, allowing leaky scanning translation of NS1 and NS2, similar to the genes of RNA-6 of influenza B virus. NS3 could be translated from the unspliced transcript. The VP transcript was not spliced and generated four VPs by a leaky scanning mechanism. The 5′-untranslated region of the VP transcript was only 5 nt long. Despite the transcription and translation strategies being radically different from those of vertebrate parvoviruses, the capsid was found to have phospholipase A2 activity, a feature thus far unique for parvoviruses.

Download Full-text

Sequence of RNA segment 7 of the influenza B virus genome: Partial amino acid homology between the membrane proteins (M1) of Influenza A and B viruses and conservation of a second open reading frame

Virology ◽

10.1016/0042-6822(82)90150-7 ◽

1982 ◽

Vol 116 (2) ◽

pp. 581-588 ◽

Cited By ~ 54

Author(s):

Dalius J. Briedis ◽

Robert A. Lamb ◽

Purnell W. Choppin

Keyword(s):

Amino Acid ◽

Membrane Proteins ◽

Influenza A ◽

Virus Genome ◽

Open Reading Frame ◽

Influenza B Virus ◽

Influenza B ◽

Amino Acid Homology ◽

Reading Frame ◽

B Virus

Download Full-text

Influenza B Virus Requires BM2 Protein for Replication

Journal of Virology ◽

10.1128/jvi.78.11.5576-5583.2004 ◽

2004 ◽

Vol 78 (11) ◽

pp. 5576-5583 ◽

Cited By ~ 25

Author(s):

Masato Hatta ◽

Hideo Goto ◽

Yoshihiro Kawaoka

Keyword(s):

Reverse Genetics ◽

Mdck Cells ◽

Open Reading Frame ◽

Initiation Codon ◽

Influenza B Virus ◽

Influenza B ◽

M Gene ◽

Reading Frame ◽

Sialidase Activity ◽

B Virus

ABSTRACT The BM2 protein of influenza B virus functions as an ion channel, which is suggested to be important for virus uncoating in endosomes of virus-infected cells. Because direct support for this function is lacking, whether BM2 plays an essential role in the viral life cycle remains unknown. We therefore attempted to generate BM2 knockout viruses by reverse genetics. Mutant viruses possessing M segments with the mutated initiation codon of BM2 protein at the stop-start pentanucleotide were viable and still expressed BM2. The introduction of multiple stop codons and a one-nucleotide deletion downstream of the stop-start pentanucleotide, in addition to disablement of the BM2 initiation codon, failed to generate viable mutant viruses, but the mutant M segments still expressed proteins that reacted with the BM2 peptide antiserum. To completely abolish BM2 expression, we generated a mutant M gene whose BM2 open reading frame was deleted. Although this mutant was not able to replicate in normal MDCK cells, it did replicate in a cell line that we established which constitutively expresses BM2. Furthermore, a virus possessing the mutant M gene lacking the BM2 open reading frame and a mutant NA gene containing the BM2 open reading frame instead of the NA open reading frame underwent multiple cycles of replication in MDCK cells, with exogenous sialidase used to supplement the deleted viral sialidase activity. These findings demonstrate that the BM2 protein is essential for influenza B virus replication.

Download Full-text

Cytoplasmic Domain of Influenza B Virus BM2 Protein Plays Critical Roles in Production of Infectious Virus

Journal of Virology ◽

10.1128/jvi.01752-07 ◽

2007 ◽

Vol 82 (2) ◽

pp. 728-739 ◽

Cited By ~ 22

Author(s):

Masaki Imai ◽

Kazunori Kawasaki ◽

Takato Odagiri

Keyword(s):

Amino Acid ◽

Infectious Virus ◽

Cytoplasmic Domain ◽

Wild Type Virus ◽

Influenza B Virus ◽

Influenza B ◽

Amino Acid Residues ◽

Wild Type ◽

Knockout Mutants ◽

B Virus

ABSTRACT Influenza B virus BM2 is a type III integral membrane protein that displays H+ ion channel activity. Analysis of BM2 knockout mutants has suggested that this protein is a necessary component for the capture of M1-viral ribonucleoprotein (vRNP) complex at the plasma membrane and for incorporation of vRNP complex into the virion during the assembly process. BM2 comprises 109 amino acid residues and possesses a longer cytoplasmic domain than the other 3 integral membrane proteins (hemagglutinin, neuraminidase, and NB). To explore whether the cytoplasmic domain of BM2 is important for infectious virus production, a series of BM2 deletion mutants lacking three to nine amino acid residues at the carboxyl terminus, BM2Δ107-109, BM2Δ104-109, and BM2Δ101-109, was generated by reverse genetics. Intracellular transport and incorporation into virions were indistinguishable between truncated BM2 proteins and wild-type BM2. The BM2Δ107-109 mutant produced levels of infectious virus similar to those of wild-type virus and displayed a spherical shape. However, the BM2Δ104-109 and BM2Δ101-109 mutants produced viruses containing dramatically reduced vRNP complex, as with BM2 knockout mutants, and formed enlarged, irregularly shaped virions. Moreover, gradient separation of membranes indicated that membrane association of M1 from mutants was greatly affected by carboxyl-terminal truncations of BM2. Studies of alanine substitution mutants further suggested that amino acid sequences in the 98-109 region are variable while those in the 86-97 region are a prerequisite for innate BM2 function. These results indicate that the cytoplasmic domain of the BM2 protein is required for firm association of the M1 protein with lipid membranes, vRNP complex incorporation into virions, and virion morphology.

Download Full-text

Recurring Influenza B Virus Infections in Seals

Emerging Infectious Diseases ◽

10.3201/eid1903.120965 ◽

2013 ◽

Vol 19 (3) ◽

pp. 511-512 ◽

Cited By ~ 53

Author(s):

Rogier Bodewes ◽

Danny Morick ◽

Gerrie de Mutsert ◽

Nynke Osinga ◽

Theo Bestebroer ◽

...

Keyword(s):

Influenza B Virus ◽

Influenza B ◽

Virus Infections ◽

B Virus

Download Full-text

Molecular Epidemiology and Phylogenetic Analyses of Influenza B Virus in Thailand during 2010 to 2014

PLoS ONE ◽

10.1371/journal.pone.0116302 ◽

2015 ◽

Vol 10 (1) ◽

pp. e0116302 ◽

Cited By ~ 31

Author(s):

Nipaporn Tewawong ◽

Kamol Suwannakarn ◽

Slinporn Prachayangprecha ◽

Sumeth Korkong ◽

Preeyaporn Vichiwattana ◽

...

Keyword(s):

Molecular Epidemiology ◽

Phylogenetic Analyses ◽

Influenza B Virus ◽

Influenza B ◽

B Virus

Download Full-text

Mutation E48K in PB1 Polymerase Subunit Improves Stability of a Candidate Live Attenuated Influenza B Virus Vaccine

Vaccines ◽

10.3390/vaccines9070800 ◽

2021 ◽

Vol 9 (7) ◽

pp. 800

Author(s):

Jongsuk Mo ◽

Stivalis Cardenas-Garcia ◽

Jefferson J. S. Santos ◽

Lucas M. Ferreri ◽

C. Joaquín Cáceres ◽

...

Keyword(s):

Vaccine Candidate ◽

The Elderly ◽

Potential Interaction ◽

Respiratory Pathogen ◽

Influenza B Virus ◽

Influenza B ◽

Epitope Tag ◽

Live Attenuated Vaccine ◽

B Virus ◽

Homologous Challenge

Influenza B virus (IBV) is a major respiratory pathogen of humans, particularly in the elderly and children, and vaccines are the most effective way to control it. In previous work, incorporation of two mutations (E580G, S660A) along with the addition of an HA epitope tag in the PB1 segment of B/Brisbane/60/2008 (B/Bris) resulted in an attenuated strain that was safe and effective as a live attenuated vaccine. A third attempted mutation (K391E) in PB1 was not always stable. Interestingly, viruses that maintained the K391E mutation were associated with the mutation E48K. To explore the contribution of the E48K mutation to stability of the K391E mutation, a vaccine candidate was generated by inserting both mutations, along with attenuating mutations E580G and S660A, in PB1 of B/Bris (B/Bris PB1att 4M). Serial passages of the B/Bris PB1att 4M vaccine candidate in eggs and MDCK indicated high stability. In silico structural analysis revealed a potential interaction between amino acids at positions 48 and 391. In mice, B/Bris PB1att 4M was safe and provided complete protection against homologous challenge. These results confirm the compensatory effect of mutation E48K to stabilize the K391E mutation, resulting in a safer, yet still protective, IBV LAIV vaccine.

Download Full-text