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bThe current diagnosis of West Nile virus (WNV) infection is primarily based on serology, since molecular identification of WNV RNA is unreliable due to the short viremia and absence of detectable virus in cerebrospinal fluid (CSF). Recent studies have shown that WNV RNA can be detected in urine for a longer period and at higher concentrations than in plasma. In this study, we examined the presence of WNV RNA in serum, plasma, whole-blood, CSF, and urine samples obtained from patients diagnosed with acute WNV infection during an outbreak which occurred in Israel in 2015. Our results demonstrate that 33 of 38 WNV patients had detectable WNV RNA in whole blood at the time of diagnosis, a higher rate than in any of the other sample types tested. Overall, whole blood was superior to all other samples, with 86.8% sensitivity, 100% specificity, 100% positive predictive value, and 83.9% negative predictive value. Interestingly, WNV viral load in urine was higher than in whole blood, CSF, serum, and plasma despite the lower sensitivity than that of whole blood. This study establishes the utility of whole blood in the routine diagnosis of acute WNV infection and suggests that it may provide the highest sensitivity for WNV RNA detection in suspected cases.

TPA (12-O-tetradecanoylphorbol-13-acetate), a well-known activator of protein kinase C (PKC), can experimentally induce reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV) in certain latently infected cells. We selectively blocked the activity of PKC isoforms by using GF 109203X or rottlerin and demonstrated that this inhibition largely decreased lytic KSHV reactivation by TPA. Translocation of the PKC␦ isoform was evident shortly after TPA stimulation. Overexpression of the dominant-negative PKC␦ mutant supported an essential role for the PKC␦ isoform in virus reactivation, yet overexpression of PKC␦ alone was not sufficient to induce lytic reactivation of KSHV, suggesting that additional signaling molecules participate in this pathway.Kaposi's sarcoma (KS)-associated herpesvirus (KSHV), also known as human herpesvirus 8, is causally implicated in KS, primary effusion lymphoma (PEL; also known as body cavitybased lymphoma), and a subset of multicentric Castleman's disease (1,10,47,48). Like all other herpesviruses, primary infection with KSHV precedes lifelong latent infection, while virus reactivation may occur and lead to an increased risk for disease development (21). Only a few viral proteins are expressed during KSHV latency, whereas extensive KSHV genome expression and productive viral DNA replication characterize the lytic phase of virus infection (19,29,43,46). Detection of KSHV in peripheral blood mononuclear cells and KSHV seropositivity are strongly predictive of the development of KS, whereas active replication of KSHV in circulating lymphoid cells is likely responsible for the spread of virus to the endothelium and the onset of KS (8,51,62). Relatively little is presently known about the host and cellular factors that can affect and play a role in the intracellular signaling pathways of virus reactivation.Major tools for studying KSHV biology are latently infected B-cell lines, derived from patients with PEL, in which the virus undergoes spontaneous lytic reactivation in a small steady fraction of the cells (44, 46). Increased, but limited, virus reactivation is observed following exposure of these cell lines to a variety of stimuli such as interleukin-6 (IL-6) (9, 11, 52) and gamma interferon (9), hypoxic conditions (16), coinfection by another viral agent (27,36,57), and treatment with chemical reagents such as n-butyrate (37), ionomycin (9, 67), 5-azacytidine (12), and the potent protein kinase C (PKC) activator 12-O-tetradecanoylphorbol-13-acetate (TPA) (39, 44). In addition, ectopic expression of the KSHV lytic replication and transcription activator (KSHV/Rta), encoded by viral open reading frame (ORF) 50, is generally sufficient to disrupt virus latency and induce lytic virus reactivation (33, 61). Thus, it is likely that at least part of the effect of agents that activate the virus lytic cycle is through the transcriptional and posttranscriptional activation of this gene; yet, the upstream signaling cascades that influence the expression of KSHV/Rta have not been fully elucidated...

The Herpesviridae family consists of eight viruses, most of which infect a majority of the human population. One of the lessstudied members is human herpesvirus 6 (HHV-6) (Roseolovirus), which causes a mild, well-characterized childhood disease. Primary HHV-6 infection is followed by lifelong latency. Reactivation frequently occurs in immunocompromised patients, such as those suffering from HIV infection or cancer or following transplantation, and causes potentially life-threatening complications. In this study, we investigated the mechanisms that HHV-6 utilizes to remain undetected by natural killer (NK) cells, which are key participants in the innate immune response to infections. We revealed viral mechanisms which downregulate ligands for two powerful activating NK cell receptors: ULBP1, ULBP3, and MICB, which trigger NKG2D, and B7-H6, which activates NKp30. Accordingly, this downregulation impaired the ability of NK cells to recognize HHV-6-infected cells. Thus, we describe for the first time immune evasion mechanisms of HHV-6 that protect lytically infected cells from NK elimination. IMPORTANCEHuman herpesvirus 6 (HHV-6) latently infects a large portion of the human population and can reactivate in humans lacking a functional immune system, such as cancer or AIDS patients. Under these conditions, it can cause life-threatening diseases. To date, the actions and interplay of immune cells, and particularly cells of the innate immune system, during HHV-6 infection are poorly defined. In this study, we aimed to understand how cells undergoing lytic HHV-6 infection interact with natural killer (NK) cells, innate lymphocytes constituting the first line of defense against viral intruders. We show that HHV-6 suppresses the expression of surface proteins that alert the immune cells by triggering two major receptors on NK cells, NKG2D and NKp30. As a consequence, HHV-6 can replicate undetected by the innate immune system and potentially spread infection throughout the body. This study advances the understanding of HHV-6 biology and the measures it uses to successfully escape immune elimination. Human herpesvirus 6 (HHV-6) (Roseolovirus) was long neglected in research and medical diagnostics; however, in the past few years, it gained increasing attention. A variety of clinical complications were found to be associated with HHV-6 infection, especially concerning immunocompromised patients, in whom it has the ability to cause severe morbidity and mortality (1, 2). HHV-6 is subclassified into two distinct variants, HHV-6A and HHV-6B, which are considered independent viruses but share major genome sequence homologies and epidemiologies (3,4). Similarly to other members of the herpesvirus family, HHV-6 causes a relatively short and mild primary disease called roseola infantum, usually in children up to the age of 2 years, with a sudden rise of fever and rash as major symptoms (5). Following this initial infection, HHV-6 establishes lifelong latency in about 90% of all individuals examined (2). Reactivation frequentl...