Gammaherpesviruses such as Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus are important human pathogens that establish long-term latent infections. Understanding of the initiation and maintenance of latent infections has important implications for the prevention and treatment of gammaherpesvirusrelated diseases. Although much is known about gammaherpesvirus pathogenesis, it is unclear how the infectious dose of a virus influences its ability to establish latent infection. To examine the relationship between the infectious dose and gammaherpesvirus latency, we inoculated wild-type mice with 0.01 to 10 6 PFU of murine gammaherpesvirus 68 (␥HV68) and quantitatively measured latency and acute-phase replication. Surprisingly, during latency, the frequencies of ex vivo reactivation were similar over a 10 7 -fold range of doses for i.p. infection and over a 10 4 -fold range of doses for intranasal infection. Further, the frequencies of cells harboring viral genome during latency did not differ substantially over similar dose ranges. Although the kinetics of acute-phase replication were delayed at small doses of virus, the peak titer did not differ significantly between mice infected with a large dose of virus and those infected with a small dose of virus. The results presented here indicate that any initiation of infection leads to substantial acute-phase replication and subsequent establishment of a maximal level of latency. Thus, infections with doses as small as 0.1 PFU of ␥HV68 result in stable levels of acute-phase replication and latent infection. These results demonstrate that the equilibrium level of establishment of gammaherpesvirus latency is independent of the infectious dose and route of infection.Gammaherpesviruses such as Epstein-Barr virus (EBV) are ubiquitous and efficiently establish long-term latent infections. Although the frequency of cells positive for EBV genome during latency differs significantly among individuals (11), it is stable over time. It is unknown whether this reflects differences in infecting doses, variations between viruses, or variations between hosts regardless of the dose. In addition, it is unclear how acute-phase replication of gammaherpesviruses relates to the level of latency. For example, data demonstrating that vaccinations reduce acute-phase replication but do not alter long-term latency (13,19) suggest that efficient acute infection is not a mandatory step for establishment of latency by a gammaherpesvirus. For alphaherpesviruses such as herpes simplex virus type 1 (HSV-1), establishment of latency correlates with the ability to initiate acute-phase replication (9). A detailed analysis demonstrated that the virus efficiently establishes a stable level of latency once acute-phase replication occurs above a threshold level (9,17,18). In contrast, for the betaherpesvirus cytomegalovirus (CMV), the extent of acutephase replication determines the load of latent viral genome (14,15). To determine how the infectious dose of a gammaherpesvirus relates to the effic...

Early mortality in acute promyelocytic leukemia has been reported to occur in less than 10% of patients treated in clinical trials. This study reports the incidence and clinical features of acute promyelocytic leukemia patients treated at Stanford Hospital, CA, USA since March 1997, focusing on early mortality. We show that the risk of early death in acute promyelocytic leukemia patients is higher than previously reported. In a cohort of 70 patients who received induction therapy at Stanford Hospital, 19% and 26% died within seven and 30 days of admission, respectively. High early mortality was not limited to our institution as evaluation of the Surveillance, Epidemiology and End Results Database demonstrated that 30-day mortality for acute promyelocytic leukemia averaged 20% from 1977-2007 and did not improve significantly over this interval. Our findings show that early death is now the greatest contributor to treatment failure in this otherwise highly curable form of leukemia. The National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database is a compilation of cancer registries that covered more than a quarter of the U.S. population. 16Using the SEER*Stat 6.6.2 software package and the SEER 17 database, 30-day death rates and 3-year survival data were obtained for APL patients aged 15 years and older. Relapse cases and cases diagnosed only at autopsy were excluded.

BCR–ABL1+ precursor B-cell acute lymphoblastic leukemia (BCR–ABL1+ B-ALL) is an aggressive hematopoietic neoplasm characterized by a block in differentiation due in part to the somatic loss of transcription factors required for B-cell development. We hypothesized that overcoming this differentiation block by forcing cells to reprogram to the myeloid lineage would reduce the leukemogenicity of these cells. We found that primary human BCR–ABL1+ B-ALL cells could be induced to reprogram into macrophage-like cells by exposure to myeloid differentiation-promoting cytokines in vitro or by transient expression of the myeloid transcription factor C/EBPα or PU.1. The resultant cells were clonally related to the primary leukemic blasts but resembled normal macrophages in appearance, immunophenotype, gene expression, and function. Most importantly, these macrophage-like cells were unable to establish disease in xenograft hosts, indicating that lineage reprogramming eliminates the leukemogenicity of BCR–ABL1+ B-ALL cells, and suggesting a previously unidentified therapeutic strategy for this disease. Finally, we determined that myeloid reprogramming may occur to some degree in human patients by identifying primary CD14+ monocytes/macrophages in BCR–ABL1+ B-ALL patient samples that possess the BCR–ABL1+ translocation and clonally recombined VDJ regions.

The fundamental question of whether a primed immune system is capable of preventing latent gammaherpesvirus infection remains unanswered. Recent studies showing that vaccination can reduce acute replication and short-term latency but cannot alter long-term latency further call into question the possibility of achieving sterilizing immunity against gammaherpesviruses. Using the murine gammaherpesvirus 68 (␥HV68) system, we demonstrate that it is possible to effectively vaccinate against long-term latency. By immunizing mice with a ␥HV68 mutant virus that is deficient in its ability to reactivate from latency, we reduced latent infection of wild-type challenge virus to a level below the limit of detection. Establishment of latency was inhibited by vaccination regardless of whether mice were challenged intraperitoneally or intranasally. Passive transfer of antibody from vaccinated mice could partially reconstitute the effect, demonstrating that antibody is an important component of vaccination. These results demonstrate the potential of a memory immune response against gammaherpesviruses to alter long-term latency and suggest that limiting long-term latent infection in a clinically relevant situation is an attainable goal.The human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus pose significant health risks worldwide, including the induction of cancer and lymphoproliferative diseases. Although acute gammaherpesvirus infection is rapidly cleared by a strong immune response, the establishment of latent infection in hematopoietic cells allows these viruses to successfully evade the host immune response and maintain lifelong infection. Therefore, one of the great challenges in the field is prevention of latent infection. However, despite concerted efforts to understand gammaherpesvirus pathogenesis and immunity, a convincing strategy to prevent long-term latency has not yet been realized.Due to the strict host restrictions of the human gammaherpesviruses, strategies for vaccinating against human gammaherpesviruses have been difficult to study. Therefore, several groups have used murine gammaherpesvirus 68 (␥HV68) infection of mice to examine whether protection against gammaherpesvirus latency can be achieved by single-protein vaccine approaches (reviewed in references 7 and 41). Although the physiology of gammaherpesvirus infection is not completely understood, it appears that latency has multiple forms in vivo, with early forms transitioning to stable long-term latency (2, 37). Several previous vaccination studies have demonstrated effective reduction in both acute infection and the early forms of latency. Vaccination against the lytic cycle protein peptide epitopes ORF6 487-495 /D b and ORF61 425-531 /K b induces strong CD8 T-cell responses and significantly reduces acute infection and early latency (3,16,25). Vaccination against the cell membrane and virus particle antigen gp150 induces neutralizing antibody and reduces acute infection and the early stages of latency (16,27)....