Epidemiology of respiratory virus infections among infants and young children admitted to hospital in Oman.

The aim of this prospective study was to determine the epidemiology of respiratory viruses responsible for seasonal epidemics of influenza-like illness in infants and young children in Oman. All children ≤5 years of age consecutively admitted to Sultan Qaboos University Hospital in Oman over a 1-year period between December 2007 and December 2008 with acute respiratory infections were included. A multiplex polymerase chain reaction (PCR) for viral detection was performed on nasopharyngeal aspirates. Analyses were conducted using univariate statistical methods. Of the 259 infants and young children, at least one respiratory virus was detected in 130 samples (50%). The most prevalent viruses were respiratory syncytial virus (RSV; 43%; n = 56), adenovirus (15%; n = 20), and parainfluenza virus (PIV) (11%; n = 14). Dual or multiple viral infections were found in 23 cases (18%). The three most prominent symptoms of the cohort were fever (78%; n = 201), tachypnoea (77%; n = 200), and runny nose (61%; n = 158). The majority had bronchiolitis (39%; n = 101) while 37% (n = 96) had pneumonia. RSV was more likely to affect those that were young (4 months vs. 7.5 months; P = 0.002) and had tachypnoea (93% vs. 69%; P = 0.004), lower respiratory tract infections (91% vs. 80%; P = 0.039), and bronchiolitis (57% vs. 38%; P = 0.024). The study indicated that respiratory viruses are highly prevalent in children ≤5 years presenting with acute respiratory infections in Oman, of which RSV is the most prominent.

Identification of enterovirus 71 isolates from an outbreak of hand, foot and mouth disease (HFMD) with fatal cases of encephalomyelitis in Malaysia.

Thirteen enterovirus 71 (EV71) isolates were obtained from both fatal and non-fatal infections of patients seen in Peninsula Malaysia and in Sarawak during an outbreak of hand, foot and mouth disease (HFMD) in Malaysia in 1997, with incidences of fatal brainstem encephalomyelitis. The isolates were identified using immunofluorescence staining, neutralization assays, and partial sequencing of the 5' untranslated regions (UTR). Assessment of the potential genetic relationships of the isolates using the partial 5'UTR sequences suggested clustering of the isolates into at least two main clusters. Isolates from Peninsula Malaysia were found in both clusters whereas Sarawak-derived isolates clustered only in cluster II. Isolates derived from fatal infections, however, occurred in both clusters and no distinctive nucleotide sequences could be attributed to the fatal isolates. Examination of the nucleotide sequences revealed at least 13 nucleotide positions in all the isolates which differ completely from the previously reported EV71 5'UTR sequences. In addition, at least 11 nucleotide position differences within the 5'UTR were noted which differentiated cluster I from cluster II. Predicted secondary RNA structures drawn using the nucleotide sequences also suggested differences between isolates from the two clusters. These findings suggest the presence of at least two potentially virulent EV71 co-circulating in Malaysia during the 1997 HFMD outbreak.

The herpes simplex virus gene UL26 proteinase in the presence of the UL26.5 gene product promotes the formation of scaffold-like structures.

The herpes simplex virus type 1 (HSV-1) polypeptides encoded by genes UL26 and UL26.5 are thought to form a scaffold around which the capsid shell assembles. The UL26 gene specifies a proteinase that cleaves both itself and the UL26.5 gene product. To study the structure and function of the UL26 and UL26.5 gene products, the proteins were expressed in cells infected with recombinant baculoviruses containing the genes under the control of the polyhedrin promoter. Both polypeptides were made in large amounts, approaching the levels of polyhedrin protein expressed in wild-type baculovirus. The UL26 polypeptide behaved in a similar manner to the protein made in HSV-1-infected cells, cleaving itself rapidly into the capsid proteins VP21 and VP24 and converting the UL26.5 product more slowly into the capsid protein VP22a. The results of immunoblot analysis using antisera specific for the amino-terminal region of the UL26 polypeptide suggested that both the first and second ATGs in the UL26 open reading frame were recognized as translational start signals but the first ATG was the preferred initiation codon as is the case in HSV-1-infected cells. Electron microscopic examination of thin section preparations of cells infected with both the UL26.5- and UL26-recombinant baculoviruses revealed the presence of large numbers of small spherical particles, often arranged in a semi-crystalline array. These clusters of scaffold-like particles were not present in cells infected with UL26-recombinant baculovirus but were observed occasionally in UL26.5-recombinant baculovirus-infected cells. The results suggest that the proteinase, in the absence of other HSV capsid proteins, stimulates the formation of large numbers of scaffold-like particles present either as semi-crystalline arrays or as dispersed structures.

Processing of the herpes simplex virus assembly protein ICP35 near its carboxy terminal end requires the product of the whole of the UL26 reading frame.

The herpes simplex virus (HSV) type 1 assembly protein ICP35 consists of a family of polypeptides, ranging in molecular weight from about 45,000-39,000. The lower molecular weight forms of ICP35 are derived from the higher molecular weight species by slow post-translational modification. The reading frame of gene UL26 and the region within this gene which exhibited homology to the cytomegalovirus assembly protein, the analogous protein to ICP35, were expressed separately under immediate-early (IE) gene regulation in a HSV vector containing a temperature-sensitive mutation in the major transcriptional regulator Vmw175. Monoclonal antibody specific for ICP35 immunoprecipitated several polypeptides with molecular weights around 75,000 from extracts of cells infected with a recombinant expressing the IE gene UL26 at the nonpermissive temperature (NPT). These results suggested that the UL26 gene specified a protein distinct from ICP35 but which had some antigenic sites in common with ICP35. In extracts of cells infected at the NPT with a recombinant expressing only the carboxy terminal half of UL26 coding sequences, the monoclonal antibody immunoprecipitated large amounts of the high molecular weight forms of ICP35. The lower molecular weight processed forms of ICP35, however, were not detectable. When cells were coinfected with both recombinants ICP35 was processed to its lower molecular weight forms. This processing step, which occurred near the carboxy terminus of ICP35, was not dependent on capsid formation. The work, together with previous information on the processing of the CMV assembly protein, suggests that UL26 product may be a protease.

The herpes simplex virus UL33 gene product is required for the assembly of full capsids.

Phenotypic analysis of the herpes simplex virus type 1 temperature-sensitive DNA-positive mutant, ts1233, revealed that the mutant had a structural defect at the nonpermissive temperature (NPT). Cells infected with ts1233 at the NPT contained large numbers of intermediate capsids, lacking dense cores but possessing some internal structure. No full capsids or enveloped virus particles were detected. In contrast to the defect in another packaging-deficient mutant ts1201, the block in the formation of dense-cored, DNA-containing capsids in ts1233-infected cells at the NPT could not be reversed by transferring the cells to the permissive temperature in the presence of a protein synthesis inhibitor. Furthermore, the capsids produced by ts1233 at the NPT had more compact internal structures than those of the gene UL26 mutant ts1201. Southern blot analysis of viral DNA in ts1233-infected cells confirmed that the mutant DNA was not encapsidated at the NPT and showed that the unpackaged DNA was not cleaved into genome-length molecules. The ts1233 mutation was mapped by marker rescue to the vicinity of genes UL32 and UL33. Sequence analysis of the DNA in this region from the mutant and two independently isolated revertants for growth revealed that ts1233 had a single base-pair change at the amino-terminal end of UL33, resulting in the substitution of an isoleucine with an asparagine. The nucleotide sequence of the revertants in this part of the genome was identical to that of wild-type virus.