JID 1992; 166 (September) Characterization of Human Herpesvirus 6 Strains Isolated from Patients with Exanthem Subitum with or without Cutaneous Rash Correspondence 689 Colleagues-Human herpesvirus 6 (HHV-6) was recently iden- tified as the etiologic agent of exanthem subitum, a common infant disease characterized by high fever and a cutaneous rash [1]. The disease also may occur with convulsions or without skin eruption [2]. Independent studies in different laboratories [3, 4] have sug- gested the existence of two distinct HHV-6 groups, typified by strains OS and Z29. OS-like strains are isolated from patients with AIDS or lymphoproliferative diseases, whereas strains simi- lar to Z29 are mainly associated with exanthem subitum. The two groups differ in restriction site polymorphism, in vitro growth properties, and reactivity to monoclonal antibodies. Au- bin et al. [5], using polymerase chain reaction (peR) and restric- tion mapping of the amplified sequences, described two distinct patterns within the Z29-like isolates. In an attempt to clarify the association of exanthem subitum with the different HHV -6 groups, we characterized 9 HHV-6 strains isolated from patients with exanthem subitum in Mo- dena, Italy, from September 1990 to February 1991. Only 2 patients had cutaneous rash, and 5 had convulsions. Virus iso- lates were obtained from pharyngeal swabs or blood specimens by cocultivation with cord blood mononuclear cells. The iso- lates were identified as HHV -6 on the basis of electron micros- copy, reactivity with monoclonal antibodies, and DNA hybrid- ization to HHV-6-specific probes. DNA from virus isolates was characterized by PCR and restriction site analysis as described by Aubin et al. [5]. For comparison, the viral prototypes OS (group A) and Z29 (group B) [4] were also included in the analy- ses. All 9 isolates yielded the Z29-like profile; figure 1 shows the pattern of two isolates in comparison with OS prototype. The two patterns within group B were equally represented (5 and 4 isolates). It was not possible to associate either of the two group B patterns with specific clinical symptoms (e.g., presence or ab- sence of respiratory or intestinal symptoms, cutaneous rash, convulsions). These HHV-6 strains, yielding either one of the two group B patterns, were isolated from cases occurring in the same geo- graphic district and during the same seasonal period, and ex- Reprints or correspondence: Dr. Enzo Cassai, Institute of Microbiology. Via Borsari 46, 44100 Ferrara. Italy. The Journal of Infectious Diseases 1992;166:689 © 1992 by The University of Chicago. All rights reserved. 0022-1899/92/6603-0048$01.00 Figure 1. Ethidium bromide staining of polymerase chain reaction (PCR) products. Aliquots of PCR products were digested with restriction endonu- c1eases(HindIII, Taqi, HinfI, and Bglll) and subjected to electrophoresis on 5% polyacrylamide gels. Molecular weight marker (mw) is I23-bp ladder. Lanes 1: patterns of HHV-6 strain GS (group A). Lanes 2 and 3: two pat- terns detected in exanthem subitum strains (group B). anthem subitum was associated with Z29-like strains. In addi- tion, PCR was useful for the characterization and distinction of HHV -6 strains. Dario Di Luca, Prisco Mirandola, Paola Secchiero, Claudio Cermelli, Arrigo Aleotti, Pasqualina Bovenzi, Marinella Portolani, and Enzo Cassai Istituto di Microbiologia and Centro di Microscopia Elettronica. Universitti di Ferrara. and Istituto di Igiene, Universiui di Modena, Italy References I. Yamanishi K, Okuno T. Shiraki K, et al. Identification of human herpes- virus 6 as a causal agent for exanthem subitum. Lancet 1988;1: 1065-7. 2. Portolani M, Cermelli C, Pietrosemoli P, et al. Isolation of HHV-6-re- lated virus from children affected by infectious syndrome. Arch Virol 1990; II 0: 143-9. 3. Schirmer EC, Wyatt LS, Yamanishi K, Rodriguez WJ, Frenkel N. Differ- entiation between two distinct classes of viruses now classified as hu- man herpesvirus 6. Proc Natl Acad Sci USA 1991;88:5922-6. 4. Ablashi DV, Balachandran N. Josephs SF. et al. Genomic polymor- phism, growth properties and immunologic variations in human her- pesvirus 6 isolates. Virology 1991;184:545-52. 5. Aubin JT. Collandre H. Candotti D. et al. Several groups among human herpesvirus 6 strains can be distinguished by Southern blotting and polymerase chain reaction. J Clin MicrobioI1991;29:367-72. Downloaded from https://academic.oup.com/jid/article/166/3/689/971555 by guest on 27 October 2023