Type Of Pathogen

HHV-6, HHV-7, and human cytomegalovirus (HCMV) are the three known human members of the Betaherpes-viridae subgroup of herpesviruses and HHV-6 and HHV-7 form the Roseolavirus genus.[1,2] Genetic, immunologic, and biological differences support the existence of distinct strains of HHV-6: HHV-6A and HHV-6B. The viruses contain an envelope, icosahedral capsid, and linear double-stranded DNA.

HHV-6A, HHV-6B, and HHV-7 have a similar genomic structure (Fig. 1). The central portion contains the unique (U) segment flanked at either end by duplicated sequences (DR). The number of kilobase pairs (kbp) encoded within the left end of each DR segments termed the het or heterogeneous region is variable and accounts for much of the variability in size between strains. The DR termini contain an analog of human telomeric repeats, a repetitive GGGTTA sequence. At either end of DR are homologs of the herpesvirus cleavage and packing signals, pac-1 andpac-2. HHV-6A strain U1102 is 159 kbp, HHV-6B strain Z29 or HST is 162 kbp, and HHV-7 strains JI and RK are 145 and 153 kbp, respectively.1-3-7-1 The majority of genes are common to all Betaherpesviridae. HHV-6B contains 115-119 potential open reading frames (ORF) (97 unique genes), HHV-6A contains 113 ORF (85 unique genes), and HHV-7 contains 101 ORF (84 unique genes). All HHV-7 genes except one have direct HHV-6A counterparts and all genes except two in HHV-6A have HHV-7 counterparts. Of the 97 unique genes in HHV-6B, it is estimated that 88 have HHV-6A counterparts and 82 have HHV-7 counterparts. Genomic differences are encoded mainly in DR and U86-100. Overall nucleotide sequence identity between HHV-6A and HHV-6B is 90%.

HHV-6A strains show greatest variability and HHV-7 strains show least with differences mainly involving the telomeric reiterations.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

Get My Free Ebook


Post a comment