Developing a vaccine against congenital CMV infection: What have we learned from animal models? Where should we go next?

Congenital human CMV infection can lead to long-term neurodevelopmental sequelae, including mental retardation and sensorineural hearing loss. Unfortunately, CMVs are highly adapted to their specific species, precluding the evaluation of human CMV vaccines in animal models prior to clinical trials. Several species-specific CMVs have been characterized and developed in models of pathogenesis and vaccine-mediated protection against disease. These include the murine CMV, the porcine CMV, the Rhesus macaque CMV, the rat CMV and the Guinea pig CMV. Because of the propensity of the Guinea pig CMV to cross the placenta, infecting the fetus in utero, it has emerged as a model of particular interest in studying vaccine-mediated protection of the fetus. In this paper, a review of these various models, with particular emphasis on the value of the model in the testing and evaluation of vaccines against congenital CMV, is provided. Recent exciting developments and advances in these various models are summarized, and recommendations are offered for high-priority areas for future study.