Comparison of the effects of acylation and amidation on the antimicrobial and antiviral properties of lactoferrin

AIMS

To compare amidation and acylation of lactoferrin (LF) from bovine milk, as a means of enhancing its antimicrobial and antiviral properties.

METHODS AND RESULTS

LF was chemically modified by amidation with a 1-ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC) in the presence of ammonium ions or by acylation with either succinic or acetic anhydride. In the test systems used, amidation substantially enhanced the activity of LF against Pseudomonas fluorescens in comparison with native LF. However, increasing the net negative charge of LF by acylation had no effect on the activity of LF against P. fluorescens, and abrogated the antimicrobial activity of LF against Bacillus subtilis and Saccharomyces cerevisiae. Increasing the net negative charges of LF by acylation eliminated its antimicrobial and antiviral effects against poliovirus and feline calicivirus (nonenveloped viruses).

CONCLUSIONS

The addition of positive charges to LF via amidation enhanced antimicrobial properties in contrast to increasing the negative charges by acylation, which abolished both the antimicrobial and antiviral properties of LF.

SIGNIFICANCE AND IMPACT OF THE STUDY

The effects of charge alteration of LF determined in this study provides a basis for further development of LF formulations with enhanced antimicrobial effectiveness for use in food process hygiene, veterinary and health-care applications.

A single chain Fv antibody displayed on phage surface recognises conformational group-specific epitope of bluetongue virus

A single chain fragment variable (scFv) antibody gene was isolated from hybridoma cell line secreting monoclonal antibody (MAb) 20E9 that recognises bluetongue virus (BTV) VP7. DNA fragments encoding variable regions of heavy and light chains were amplified by RT-PCR and library of scFv was constructed in phage vector. Two scFv clones that were selected showed specific reactivity with conformational epitope VP7. The N-terminal 22 amino acid residues of 20E9 light chain were identical to that deduced from scFv DNA sequence. An in-frame TAG stop codon was found in the coding sequence and its potential role in regulating the expression and stability of scFv in phage is discussed.

The exceptionally large genome of Hendra virus: support for creation of a new genus within the family Paramyxoviridae

An outbreak of acute respiratory disease in Hendra, a suburb of Brisbane, Australia, in September 1994 resulted in the deaths of 14 racing horses and a horse trainer. The causative agent was a new member of the family Paramyxoviridae. The virus was originally called Equine morbillivirus but was renamed Hendra virus (HeV) when molecular characterization highlighted differences between it and members of the genus Morbillivirus. Less than 5 years later, the closely related Nipah virus (NiV) emerged in Malaysia, spread rapidly through the pig population, and caused the deaths of over 100 people. We report the characterization of the HeV L gene and protein, the genome termini, and gene boundary sequences, thus completing the HeV genome sequence. In the highly conserved region of the L protein, the HeV sequence GDNE differs from the GDNQ found in almost all other nonsegmented negative-strand (NNS) RNA viruses. HeV has an absolutely conserved intergenic trinucleotide sequence, 3'-GAA-5', and highly conserved transcription initiation and termination sequences similar to those of respiroviruses and morbilliviruses. The large genome size (18,234 nucleotides), the unique complementary genome terminal sequences of HeV, and the limited homology with other members of the Paramyxoviridae suggest that HeV, together with NiV, should be classified in a new genus in this family. The large genome of HeV also fills a gap in the spectrum of genome sizes observed with NNS RNA virus genomes. As such, it provides a further piece in the puzzle of NNS RNA virus evolution.

Sequence analysis of the Hendra virus nucleoprotein gene: comparison with other members of the subfamily Paramyxovirinae

The nucleoprotein (N) gene of Hendra virus (HeV), an unclassified member of subfamily Paramyxovirinae in the family Paramyxoviridae previously known as equine morbillivirus, was cloned and sequenced. The majority of the deduced amino acid sequence was further confirmed by direct sequencing of peptide fragments of the N protein derived from purified virions. The 3' untranslated sequence of the HeV N gene mRNA was 568 nt and was much longer than that observed in other Paramyxovirinae. The N protein was 532 amino acids in length with a molecular mass of 58.5 kDa. Although the HeV N protein had a slightly higher amino acid sequence identity to those of the genus Morbillivirus than to those of other Paramyxovirinae genera, the level of identity was much lower than that observed within the morbilliviruses. Our results indicated that HeV could not confidently be classified as a member of the genus Morbillivirus, Paramyxovirus or Rubulavirus and suggest that the virus be classified in a new genus within the Paramyxovirinae.

A novel P/V/C gene in a new member of the Paramyxoviridae family, which causes lethal infection in humans, horses, and other animals

In 1994, a new member of the family Paramyxoviridae isolated from fatal cases of respiratory disease in horses and humans was shown to be distantly related to morbilliviruses and provisionally called equine morbillivirus (K. Murray et al., Science 268:94-97, 1995). To facilitate characterization and classification, the virus was purified, viral proteins were identified, and the P/V/C gene was cloned and sequenced. The coding strategy of the gene is similar to that of Sendai and measles viruses, members of the Paramyxovirus and Morbillivirus genera, respectively, in the subfamily Paramyxovirinae. The P/V/C gene contains four open reading frames, three of which, P, C, and V, have Paramyxovirinae counterparts. The P and C proteins are larger and smaller, respectively, than are cognate proteins in members of the subfamily, and the V protein is made as a result of a single G insertion during transcription. The P/V/C gene has two unique features. (i) A fourth open reading frame is located between those of the C and V proteins and potentially encodes a small basic protein similar to those found in some members of the Rhabdoviridae and Filoviridae families. (ii) There is also a long untranslated 3' sequence, a feature common in Filoviridae members. Sequence comparisons confirm that although the virus is a member of the Paramyxovirinae subfamily, it displays only low levels of homology with paramyxoviruses and morbilliviruses and negligible homologies with rubulaviruses.