Strains of Epstein-Barr virus (EBV) with deletions of the small RNA (EBER) genes were made by homologous recombination using the EBV P3HR-1 strain, which has undergone deletion of the essential transforming gene that encodes the EBV nuclear antigen, EBNA-2, and a DNA fragment that was wild type at the EBNA-2 locus but from which the EBER genes had been deleted. Even though the EBER and EBNA-2 genes are separated by 40 kilobases, selection for transforming P3HR-1 recombinants that required a restored EBNA-2 gene resulted in 20% cotransfer of the EBER deletion. EBER-deleted recombinants transformed primary B lymphocytes into lymphoblastoid cell lines (LCLs), which were indistinguishable form LCLs transformed by wild-type EBV in their proliferation, in latency-associated EBV gene expression, and in their permissiveness for EBV replication cycle gene expression. EBER-deleted virus from infected LCL clones could infect and growth-transform primary B lymphocytes. These procedures should be applicable to the construction of other EBV recombinants within 40 kilobases of the EBNA-2 gene. The EBER-deleted EBV recombinants should be useful in further evaluating the role of EBERs in EBV infection.

Epidemic transmission of Zika virus (ZIKV) has rapidly occurred in the Americas, with most cases limited to mild or asymptomatic disease.^1,2 To date, nine deaths from ZIKV infection that were unrelated to the Guillain–Barré syndrome have been confirmed in adults.¹ Here, we report a rapidly progressive, fatal ZIKV infection acquired outside the United States and secondary local transmission in the absence of known risk factors for ZIKV infection.

Patients with cancer are at increased risk for developing infectious complications during the course of their disease and treatment. The following sections of the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Prevention and Treatment of Cancer-Related Infections provide an overview of the risk factors for infectious complications, recommendations for infectious risk categorization, and strategies for prevention of infections in high-risk patient populations with cancer. Individualized risk evaluation for infections and incorporation of preventative measures are essential components of the overall spectrum of cancer care, and may contribute to optimizing treatment outcomes for patients. Patients with cancer are at increased risk for developing infectious complications during the course of their disease and treatment. The following sections of the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Prevention and Treatment of Cancer-Related Infections provide an overview of the risk factors for infectious complications, recommendations for infectious risk categorization, and strategies for prevention of infections in high-risk patient populations with cancer. Individualized risk evaluation for infections and incorporation of preventative measures are essential components of the overall spectrum of cancer care, and may contribute to optimizing treatment outcomes for patients.

Kaposi's sarcoma-associated herpesvirus (KSHV) is a human herpesvirus that causes Kaposi's sarcoma and is associated with the development of lymphoproliferative diseases. KSHV reactivation from latency and virion production is dependent on efficient transcription of over eighty lytic cycle genes and viral DNA replication. CTCF and cohesin, cellular proteins that cooperatively regulate gene expression and mediate long-range DNA interactions, have been shown to bind at specific sites in herpesvirus genomes. CTCF and cohesin regulate KSHV gene expression during latency and may also control lytic reactivation, although their role in lytic gene expression remains incompletely characterized. Here, we analyze the dynamic changes in CTCF and cohesin binding that occur during the process of KSHV viral reactivation and virion production by high resolution chromatin immunoprecipitation and deep sequencing (ChIP-Seq) and show that both proteins dissociate from viral genomes in kinetically and spatially distinct patterns. By utilizing siRNAs to specifically deplete CTCF and Rad21, a cohesin component, we demonstrate that both proteins are potent restriction factors for KSHV replication, with cohesin knockdown leading to hundred-fold increases in viral yield. High-throughput RNA sequencing was used to characterize the transcriptional effects of CTCF and cohesin depletion, and demonstrated that both proteins have complex and global effects on KSHV lytic transcription. Specifically, both proteins act as positive factors for viral transcription initially but subsequently inhibit KSHV lytic transcription, such that their net effect is to limit KSHV RNA accumulation. Cohesin is a more potent inhibitor of KSHV transcription than CTCF but both proteins are also required for efficient transcription of a subset of KSHV genes. These data reveal novel effects of CTCF and cohesin on transcription from a relatively small genome that resemble their effects on the cellular genome by acting as gene-specific activators of some promoters, but differ in acting as global negative regulators of transcription. Kaposi's sarcoma-associated herpesvirus (KSHV) is a human virus that causes Kaposi's sarcoma and lymphoma. KSHV establishes a lifelong infection in B lymphocytes, and persists in a latent form as circular DNA molecules. Reactivation and replication yield infectious virions, allowing transmission and maintenance of latent infection. The cellular mechanisms controlling reactivation remain incompletely characterized. Host proteins that regulate RNA transcription play an important role in controlling viral reactivation. In this study, we used high-throughput techniques to analyze the binding of two cellular proteins, CTCF and Rad21, to the KSHV genome as the virus reactivated to produce infectious virions. We found that these proteins dissociate from the latent genome when reactivation occurs. We also found that depleting cells of these proteins increases virus production as much as a hundredfold. Depleting the cell of CTCF or Rad21 caused complex changes in the synthesis of RNAs by KSHV, with the amounts of most KSHV RNAs increasing greatly. We also showed that Rad21 and CTCF are needed for the virus to synthesize RNAs efficiently. Our study provides new insights into how the cell uses CTCF and Rad21 to limit KSHV's ability to synthesize RNA and reactivate from latency to produce infectious virus.

The ORF57 gene of Kaposi9s sarcoma-associated herpesvirus (KSHV) encodes a nuclear protein expressed during the lytic phase of KSHV replication. An ORF57 homolog is present in all known human herpesviruses and many animal herpesviruses. Many of these proteins have been demonstrated to have essential transcriptional and posttranscriptional regulatory functions. ORF57 enhances expression of reporter genes posttranscriptionally in vitro and may synergize with transcription factors to enhance gene transcription. However, the biologic role of ORF57 in KSHV replication has not been established. In this study, we demonstrate that ORF57 is essential for productive KSHV lytic replication by constructing a recombinant KSHV in which ORF57 expression has been specifically inactivated. The ORF57-null KSHV recombinant was unable to produce virion progeny or fully express several other lytic KSHV genes except when ORF57 was provided in trans. The Epstein-Barr virus (EBV) homolog of ORF57, SM, was unable to rescue lytic KSHV virion production, although EBV SM does enhance KSHV lytic gene expression from the ORF57-null mutant. Conversely, ORF57 did not rescue an SM-null recombinant EBV, indicating the existence of virus-specific functions for the ORF57 family of genes.

Epstein-Barr virus (EBV) SM protein is an essential nuclear protein produced during the lytic cycle of EBV replication. SM is an RNA-binding protein with multiple mechanisms of action. SM enhances the expression of EBV genes by stabilizing mRNA and facilitating nuclear export. SM also influences splicing of both EBV and cellular pre-mRNAs. SM modulates splice site selection of the host cell STAT1 pre-mRNA, directing utilization of a novel 5′ splice site that is used only in the presence of SM. SM activates splicing in the manner of SR proteins but does not contain the canonical RS domains typical of cellular splicing factors. Affinity purification and mass spectrometry of SM complexes from SM-transfected cells led to the identification of the cellular SR splicing factor SRp20 as an SM-interacting protein. The regions of SM and SRp20 required for interaction were mapped by in vitro and in vivo assays. The SRp20 interaction was shown to be important for the effects of SM on alternative splicing by the use of STAT1 splicing assays. Overexpression of SRp20 enhanced SM-mediated alternative splicing and knockdown of SRp20 inhibited the SM effect on splicing. These data suggest a model whereby SM, a viral protein, recruits and co-opts the function of cellular SRp20 in alternative splicing.