Extensive cross-reactivity of adenovirus-specific cytotoxic T cells.

Although adenovirus is a major source of morbidity for immunocompromised individuals and a popular vector for gene therapy, little is known about the cellular immune responses it evokes in humans. Initial trials using adenovirus vectors have been disappointing, probably owing both to a preexisting immune response to Ad2 and Ad5, the most commonly used vector backbones, and to a response to the transgene. The former problem might be overcome by switching from the common type C adenoviruses, of which Ad2 and Ad5 are members, to other less common serotypes. Evidence for the feasibility of this approach has been provided by a rat model system. However, its success in humans depends on there being no immunological cross-reactivity between groups at the humoral or cellular level. Here, we examine the cross-reactivity of the cellular immune response to adenovirus in a human system, and find that human cytotoxic T lymphocytes (CTLs) prepared in vitro against an adenovirus from two of the six subgroups can lyse cells infected with adenoviruses from the other subgroups. Hence, the proposed use of adenovirus vectors from uncommon subgroups to evade memory immune response to subgroup C adenoviruses may not be successful. However, this same cross-reactivity indicates that adoptive transfer of CTLs generated in vitro against one adenovirus serotype may protect immunocompromised patients from infections by adenoviruses of all serotypes.

Adenovirus-pulsed dendritic cells stimulate human virus-specific T-cell responses in vitro.

Adenovirus infections cause significant morbidity and mortality in immunocompromised patients, yet little is known about the immune response to adenovirus infections. We established a system for the generation of a cytotoxic immune response to adenovirus in vitro. Cytotoxic T cells (CTLs) were derived from normal donors by using peripheral blood dendritic cells as antigen-presenting cells. The CTLs were found to contain a mixture of effector cells that recognized virus peptides in the context of both class I and class II antigens. Endogenous viral gene expression was not required to sensitize cells to lysis by adenovirus-specific CTLs. CTLs raised against subgroup C adenovirus type 5 can lyse cells infected with subgroup B adenovirus type 11, indicating that viruses of different subgroups have epitopes in common. This system holds promise for defining the human immune response to adenovirus, including characterization of the viral protein(s) against which the response is generated, and the identity of the effector cells. Such studies are in progress.

Theophylline induced differentiation provides direct evidence for the deregulation of c-myc in Burkitt's lymphoma and suggests participation of immunoglobulin enhancer sequences.

Most of the evidence that supports the hypothesis that the c-myc gene is abnormally regulated in Burkitt's lymphoma (BL) is indirect. The putative abnormal expression of c-myc is likely, at least in part, to be a consequence of the usurpation of its regulatory sequences by immunoglobulin enhancer elements, which are invariably juxtaposed to c-myc by the translocations associated with this tumor (C. M. Croce, J. Erikson, A. Ar-Rushdi, D. Aden, and K. Nishikura, Proc. Natl. Acad. Sci. USA, 81: 3170-3174, 1984). We have developed a differentiation induction model system to examine this issue more directly. In a variety of non-BL cell lines, differentiation induction results in the down-regulation of c-myc (G. P. Studzinski, A. K. Bhandal, and Z. S. Brelvi, Proc. Soc. Exp. Biol. Med., 179: 288-295, 1985; Y. Matsui, R. Takahasi, K. Minara, T. Nakagawa, T. Koizumi, Y. Nakao, T. Sugiyama, and T. Fugita, Cancer Res., 49: 1366-1371, 1985; T. Mitchell, E. Sariban, and D. Kufe, Mol. Pharmacol., 30: 398-402, 1986; Z. S. Brelvi, and G. P. Studzinski, J. Cell. Physiol., 128: 171-179, 1986). Since BL is of B-cell origin, differentiation is associated with persistent or increased expression of immunoglobulin genes. Therefore, if c-myc and c-mu are coregulated in BL via immunoglobulin enhancer sequences, persistent or increased expression of the c-myc gene, rather than down-regulation, should occur in differentiated BL cells. Differentiation was induced in four BL cell lines with theophylline (7 x 10(-3) M), and mRNA was examined by Northern blot analysis. In all four BL lines studied (JD38, AG876, KK124, and Daudi), there was persistent or increased expression of both c-mu and c-myc genes (detected with a third exon c-myc probe), in contrast to the decreased expression of the c-myc gene observed in the three Epstein-Barr virus transformed lines studied (A3317, TC84, and CB34). In the BL cell line, JD38, the c-myc gene is truncated (the second and third exons are translocated to chromosome 14 while the first exon remains on chromosome 8). In this line, we demonstrated that theophylline induced differentiation results in down-regulation of the first exon while the level of expression of the translocated second and third exons remains unchanged or increases.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of a novel surface antigen MKW in childhood acute leukemia has prognostic significance.

A monoclonal antibody (MoAB) has been developed which reacts with a previously unidentified hematopoietic cell surface protein called MKW. This MoAB (anti-MKW) does not cluster with antibodies in any of the known cluster groups of differentiation. Blast cell expression of MKW was studied in 196 consecutively diagnosed children with acute lymphoblastic leukemia (ALL), 69 children with previously untreated acute myeloblastic leukemia (AML) and four children with secondary AML. MKW expression, clinical, laboratory and cytogenetic features at diagnosis, and treatment response and duration were examined for significant correlations. MKW was expressed on blasts from 12.8% of children with ALL and 24.6% of children with de novo AML. The expression of MKW appears to be more common in patients with secondary AML (three of four) than de novo AML (17 of 69). In patients with AML, the expression of MKW was correlated with an elevated initial leukocyte count (p = 0.0005) and poorer disease-free survival (p = 0.04). In patients with ALL, the expression of MKW was associated with a lower hemoglobin level (p less than 0.05) and a lower complete remission rate (p = 0.02). At a median follow-up of 4.6 years ALL patients with greater than or equal to 50% MKW+ blasts had a poorer event-free survival (EFS) than both MKW+ patients with 25-49% positive blasts (p = 0.03) and MKW+ patients (p = 0.0001). The disease-free survival was also poorer for ALL patients with greater than or equal to 50% MKW+ blasts (p = 0.02). In Cox regression analysis, the expression of MKW had an independent prognostic significance in children with ALL. As MKW is a unique cell surface antigen and its expression has prognostic significance in acute leukemias in children, further study in a larger series of patients is warranted.