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of TVS from a mean neointimal index (NI)=42.9 to 82.9 (Streblow et al. 2003).
RCMV infection failed to induce TVS in syngeneic cardiac grafts by the study end-
point of 120 days (mean, NI = 4.2 vs uninfected controls, mean, NI = 8.8). Assessment
of grafts at earlier times before CR has revealed an even more pronounced effect of
RCMV infection on TVS progress. RCMV infection significantly increased the
severity of TVS in heart allografts at days 28, 35 and 45 (mean, NI = 48, 70, and 82)
compared to uninfected recipients (mean, NI=31, 30 and 43). Graft hearts from
infected but not from uninfected recipients showed an early (days 7 and 14) presence
of endothelialitis (Streblow et al. 2003). In these animals, PCR identified RCMV
DNA in all submandibular glands (SMG) at days 7, 14, 21, 28, 35, and 45. In native
and graft hearts, RCMV DNA was highest at postoperation days 7 and 14, corre-
sponding to the time when endothelialitis is present within the graft vessels. After
this time, virus production is low but detectable throughout the development of TVS
(Streblow et al. 2003). However, RCMV was only detected in the blood until 14 days.
The presence of virus in the heart allografts at the later time points postinfection was
confirmed by immunostaining for RCMV-IE proteins. The number of RCMV-IE-
positive cells present in the allografts at days 21 and 28 was low; however, positive
cells are observed as single, infected cells or in small 10-30 infected cell foci. To
determine whether virus replication was necessary for RCMV-accelerated TVS, we
treated allograft recipients with ganciclovir (20 mg/kg/day for 45 days), which
increased the mean time to allograft CR from 45 to 75 days (
p
< 0.001) and decreased
TVS formation from a mean neointimal index of 80 to 65 (
p
< 0.001).
In the rat heart transplant model, using a bone marrow chimera model of toler-
ance induction, the recipient alloreactive immune response was shown to be
required for RCMV acceleration of graft loss (Orloff et al. 2002). These data sug-
gest that RCMV infection requires an allogeneic immune environment for the
acceleration of TVS. In this rat cardiac transplant CR model, chemokine expression
was increased in virus-infected recipient grafts compared to uninfected controls
(Streblow et al. 2003). RCMV-infected graft tissues also contained increased num-
bers of immune cell infiltrates including macrophages, CD4 and CD8 T cells, and
the presence of these cells paralleled the upregulation of chemokines. Similar find-
ings were observed in a rat CR small bowel and renal transplant models (Orloff
et al. 2002; Soule et al. 2006). Our results indicate that while not all allograft cells
are infected, viral replication is important to drive the acceleration of TVS. Taken
together, our findings suggest that the virus-mediated acceleration of TVS occurs
through altered regulation of inflammation and wound healing processes.
RCMV Induces Allograft AG and WH Genes During
the Acceleration of TVS
To determine the mechanisms by which RCMV accelerates the development of
allograft TVS, we analyzed the cellular RNA expression in allograft hearts with and
without CMV infection using DNA microarrays. For these experiments, Lewis
