Chapter 117 - Varicella-zoster Virus Infection of T cells and Skin in the SCID-hu Mouse Model

Abstract

This chapter presents a severe combined immunodeficiency-human (SCID-hu) mouse model of varicella-zoster virus (VZV) infection of T cells and skin. This model provides a new system for analyzing the relationships between viral gene expression and human cell tropism, by using naturally arising VZV variants and recombinant VZV strains that carry directed mutations. In this model, the male homozygous CB-17 scid/scid mice are bred, maintained, and implanted with human fetal tissues. When the mice are 8 weeks old, co-implants of human fetal thymus and liver tissue from 18–23 week fetuses are introduced under the kidney capsule as a conjoint implant by using an 18 G trocar. The thymus/liver implants develop for 6–8 weeks before use and human skin is introduced subcutaneously as full-thickness dermal grafts and is allowed to engraft for 3–5 weeks before use. Due to the impaired immunity of SCID-hu mice, the bedding, food, and water are sterilized by autoclaving before use. In addition, SCID-hu mice receive trimethoprim sulfamethoxazole in the drinking water for 3 days of each week to prevent opportunistic infection by Pneumocystis carinii and other parasites. The thymus/liver tissue under the kidney capsule or subcutaneous skin tissue implanted in SCID-hu mice is surgically exposed, then VZV-infected cells are injected into the implant to initiate virus replication in the human tissue. The mice remain free of disease during the course of the experiment. The extent of VZV infection is determined by the titration of infected T cells in an infectious focus assay and by FACS analysis using VZV-specific antibodies and conjugates to T-cell markers such as CD3, CD4, and CD8.