Mark W. Brunvand

Relationship of Reconstituted Adaptive and Innate Cytomegalovirus (CMV)-Specific Immune Responses with CMV Viremia in Hematopoietic Stem Cell Transplant Recipients

BACKGROUND Cytomegalovirus (CMV) is a major cause of morbidity in transplant recipients. An immunologic predictor of protection against CMV reactivation or disease is highly desirable. METHODS Thirty-eight allogeneic hematopoietic stem cell transplant recipients at risk of CMV disease were prospectively monitored using whole blood CMV-DNA polymerase chain reaction assay, lymphocyte proliferation assay (LPA), interferon gamma enzyme-linked immunospot assay (ELISPOT), and flow cytometric enumeration of CMV-specific CD69+interferon (IFN)gamma+CD4, CD8, natural killer cells, and gammadelta T cells. RESULTS Twenty-one subjects developed > or =1 episode of CMV viremia and 4 developed disease during 360 days of follow-up. Among CMV-seropositive recipients, positive CMV-LPA before transplantation correlated with higher risk of developing viremia after transplantation (P = .02). In contrast, after transplantation, reconstitution of CMV-LPA was significantly associated with absence of CMV viremia over 360 days of follow-up (P = .04) and with faster clearance of viremia during individual episodes of CMV reactivation (P = .03). Reconstitution of CMV-specific natural killer cells was also associated with absence of CMV viremia over 360 days of study (P = .04) but not with faster clearance of viremia. CMV-specific CD4, CD8, gammadelta T cells, and ELISPOT values were not significantly different in viremic subjects, compared with the corresponding values in nonviremic subjects, at any time point. CONCLUSIONS To our knowledge, this is the first study to prospectively compare multiple measures of innate and adaptive immune responses in hematopoietic stem cell transplant recipients with CMV viremia. The strongest immune correlates with protection against CMV viremia in hematopoietic stem cell transplant recipients are reconstitution of CMV-specific T cell memory responses (LPA) and recovery of natural killer cell function. In contrast, positive CMV-LPA before transplantation may be a marker of high risk of CMV reactivation after transplantation.

Octamer proteins inhibit IL-4 gene transcription in normal human CD4 T cells

The balance of Th1 (eg, interleukin-2 (IL-2)) and Th2 (eg, IL-4) cytokines produced by CD4 T cells markedly influences the outcome of the adaptive immune response. Although octamer transcription factor proteins increase IL-2 transcription in T cells, their role in IL-4 gene transcription remains controversial. We have previously shown and now confirm that the proximal octamer binding site of the human IL-4 promoter, which separates the two most proximal NFAT binding sites, is bound prior to, but not after, activation in vivo. Since these two NFAT sites are essential for optimal IL-4 promoter activity, this suggested that prior engagement by octamer proteins might prevent adjacent NFAT binding and inhibit IL-4 gene transcription. In support of this hypothesis, here we show that NFAT proteins are unable to bind to a combined octamer/NFAT site unless the octamer proteins are competed away. Moreover, activity of an IL-4 reporter gene mutated in the proximal octamer binding site is increased compared to the wild-type promoter in human peripheral blood CD4 T cells. In addition, over-expression of either Oct-1 or Oct-2 decreased wild-type IL-4 promoter activity, while increasing IL-2 promoter activity. No decrease in promoter activity was seen when Oct-1 or Oct-2 was over-expressed with the octamer-mutant IL-4 reporter gene. Thus, octamer proteins are candidates to promote a Th1 rather than Th2 pattern of cytokine gene expression by activated CD4 T cells.