Molecular cloning and physical mapping of the genome of simian herpes B virus and comparison of genome organization with that of herpes simplex virus type 1.

The molecular structure of the genome of simian herpes B virus (SHBV) was determined by restriction endonuclease mapping studies. Genomic DNA was cleaved with restriction endonucleases BamHI and SalI into 41 and 58 fragments, respectively. Most of these fragments were cloned into the plasmid vector pACYC184; uncloned fragments were identified following isolation from agarose gels. Terminal fragments were identified by exonuclease digestion and radioactive end-labelling, and linkage of fragments was deduced by a combination of single and double digest experiments and cross-blot hybridizations. The genome is larger than that of herpes simplex virus type 1 (HSV-1), being approximately 165 kilobase pairs. Like that of HSV-1, the SHBV genome is composed of a long and a short unique region each flanked by inverted repeat sequences, which allow the unique regions to invert relative to one another, resulting in four possible isomeric arrangements of the molecule. Genome locations of several SHBV genes were compared with their HSV-1 homologues.

Nucleotide sequence analysis of a homologue of herpes simplex virus type 1 gene US9 found in the genome of simian herpes B virus.

The 10K gene of simian herpes B virus (SHBV) has been located and the nucleotide sequence determined. Its relationship to homologous genes in other herpes-viruses has been examined. The SHBV 10K gene exhibits a closer relationship to its homologue in HSV-1 than to those in the other viruses studied. Nucleotide sequence identity of 61% was found between the HSV-1 and SHBV 10K genes, and 57% identity was found between the corresponding predicted protein sequences. A comparison of the amino acid sequences of the herpesvirus 10K proteins has revealed a number of conserved features. These are examined in relation to possible functions of the 10K proteins. Implications for evolutionary relationships between SHBV and other herpesviruses are discussed.

Comparison of Directigen FLU-A with viral isolation and direct immunofluorescence for the rapid detection and identification of influenza A virus.

Directigen FLU-A, an enzyme immunoassay membrane test, was compared prospectively to isolation in cell culture and direct immunofluorescence (IF) for the detection of influenza A virus. One hundred ninety specimens were evaluated by Directigen FLU-A and cell culture; 184 of these specimens were also tested by direct IF. The sensitivity of Directigen FLU-A compared to isolation in cell culture and direct IF was 100%. The specificities of Directigen FLU-A compared to isolation and direct IF were identical, 91.6%. Fourteen specimens that were positive by Directigen FLU-A did not yield virus in culture; two of the specimens, however, were positive by direct IF, and four other specimens were not specimens of choice for the test. A positive Directigen result had positive predictive values of 62.6 and 75.0% compared to isolation and direct IF, respectively; a positive Directigen result with an intensity reading of 2+ or greater, however, had positive predictive values of 85 and 100% compared to isolation and direct IF, respectively. In all comparisons, the negative predictive value was 100%. There was no evidence that cross-reactivity occurred with non-influenza A antigens. Directigen FLU-A should serve as a convenient screening test for influenza A and as a rapid test supported by isolation in cell culture during an influenza outbreak.

Comparison of directigen RSV with viral isolation and direct immunofluorescence for the identification of respiratory syncytial virus.

An enzyme immunoassay membrane test (Directigen RSV) for the detection of respiratory syncytial virus in clinical specimens was compared prospectively with isolation in cell culture and direct immunofluorescence (IF). A total of 315 nasopharyngeal wash specimens from pediatric patients were examined. Directigen RSV was 86.1% sensitive and 91.3% specific for specimens positive by isolation in cell culture and/or IF, with 88.6% agreement. The false-positive rate was 16%; 2 of 20 specimens giving false-positive reactions by Directigen RSV were true-positives by blocking assay. Twenty-seven specimens (8.5%) whose results were initially uninterpretable by Directigen RSV due to filtration difficulties were diluted and upon retesting produced acceptable results. Sixty-three viral isolates and/or IF identifications of virus antigens representing seven virus groups other than respiratory syncytial virus were also found; cross-reactions between Directigen RSV and other viruses were not observed. Directigen RSV will be useful as an immediate procedure and in facilities lacking a comprehensive virology laboratory.

Discrimination between twenty isolates of herpesvirus simiae (B virus) by restriction enzyme analysis of the viral genome.

Twenty isolates, obtained from adult breeding monkeys, were all identified as herpesvirus simiae (B virus) by neutralisation with polyclonal B virus antiserum. Subsequent analysis of restriction enzyme profiles produced by digestion of DNA from the isolates enabled discrimination to be made between them. In particular Cynomolgus monkey isolates could be distinguished from those of Rhesus animals. One isolate (isolate 9) could not be typed either as B virus or as the antigenically related herpesvirus SA8, despite neutralisation by B virus antiserum. Unlike herpes simplex virus, B virus isolates could not be divided into oral and genital types on the basis of restriction enzyme profiles.