Recent developments in animal models for human herpesvirus 6A and 6B

• New animal models were recently established in mice and non-human primates.
• Pathological changes are seen in CNS of marmosets and CD46-transgenic mice.
• Acute-phase symptoms with robust viral replication are seen in macaques.
• Various human thymocyte subpopulations are altered in humanized mice.

Progress in the identification of suitable animal models for human herpesvirus (HHV)-6A and HHV-6B infections has been slow. Recently, new models have been established, mainly for HHV-6A, which reproduce some pathological features seen in humans. Neuroinflammatory signs were observed in infected marmosets and CD46-transgenic mice; although viral replication was not prominent, persistence of viral DNA and specific immunologic responses were detected, suggesting an immune-mediated pathogenic mechanism. Pig-tailed macaques showed robust viral replication concomitant with acute-phase symptoms, and provided a model to study the effects of HHV-6A on AIDS progression. In humanized mice, viral replication was less evident, but infection led to T-cell alterations. Altogether, these recent developments have opened new perspectives for studying the pathogenic role of HHV-6A in humans.

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