Nurith Mador

The latency-associated gene of herpes simplex virus type 1 (HSV-1) interferes with superinfection by HSV-1

During herpes simplex virus type 1 (HSV-1) lifelong latency in human peripheral sensory ganglia (PSG), only the viral latency-associated transcript (LAT) gene is expressed. This raises the possibility that this gene is involved in establishment of latency of the virus, its maintenance, or reactivation. Here we present data that indicate yet another independent function of the LAT gene: interference with HSV-1 superinfection of latently infected neurons. Neuronal cells stably expressing the LATs are protected from infection with HSV-1, but not from infection by other RNA and DNA viruses, including HSV-2. These unexpected findings may explain the observation that human PSG are latently infected with just a single strain of HSV-1, despite repeated exposure during life to multiple viral strains. Thus, the LATs may protect the latent HSV-1 reservoir from cytopathic superinfections, and at the same time the host is protected at the viral entry site from HSV-1 insults that may eventually cause viral encephalitis.

Emergence of oseltamivir-resistant influenza A/H3N2 virus with altered hemagglutination pattern in a hematopoietic stem cell transplant recipient

BACKGROUND Persistent influenza virus replication during antiviral therapy in patients undergoing hematopoietic stem cell transplantation (HSCT) could promote the emergence of antiviral drug resistance. OBJECTIVES To follow the viral genotypic and drug susceptibility changes in a patient who developed progressive influenza A/H3N2 pneumonia despite oseltamivir therapy after haploidentical HSCT. STUDY DESIGN Direct genotypic analysis of the neuraminidase (NA) and hemagglutinin (HA) genes in successive bronchoalveolar lavage specimens was employed in combination with hemagglutination and NA enzymatic activity assays of the corresponding viral isolates. RESULTS The emergence of NA oseltamivir-resistance mutation R292K was detected by 12 days of oseltamivir treatment with 44,286-fold increase in oseltamivir IC50. Resurgence of wild type viral population was identified by 7 days after cessation of oseltamivir. Sequential HA mutations R228S and A138S were identified and associated with a shift in the HA receptor binding pattern reflected by loss of the ability to agglutinate chicken erythrocytes. CONCLUSIONS These rapid evolutionary changes warrant close virologic monitoring of immunocompromised patients treated for influenza infection, and raise concern about the efficacy of mono-drug therapy for influenza-associated disease in HSCT recipients.

Early-Onset Guillain-Barré Syndrome Associated with Reactivation of Epstein-Barr Virus Infection after Nonmyeloablative Stem Cell Transplantation

We report a case of early-onset acute Guillain-Barre syndrome associated with reactivation of Epstein-Barr virus (EBV) infection after nonmyeloablative stem cell transplantation (NST). Reactivation of EBV infection preceded disease onset, and the virus load increased concomitantly with disease progression (doubling time, 2.7 days). This case raises concern about the expanding scope of manifestations associated with reactivation of EBV infection after NST.

Transgenic Mouse with the Herpes Simplex Virus Type 1 Latency-Associated Gene: Expression and Function of the Transgene

ABSTRACT During herpes simplex virus type 1 (HSV-1) latent infection in human peripheral sensory ganglia, the major viral gene transcribed is the latency-associated transcript (LAT) gene. In order to facilitate the study of this gene, we generated a transgenic mouse that contains the DNA fragment that transcribes the LAT RNAs (2.0 kb and its 1.5-kb spliced transcript) under control of the cytomegalovirus promoter. The tissue distribution of these transcripts and their effects upon HSV-1 replication, latency, and reactivation in the transgenic-mouse model were examined. Different steady-state amounts of both transcripts were found in various tissues. While the highest levels of the 2.0-kb RNA were detected in heart and skeletal muscle, the 1.5-kb transcript was found at elevated levels in the brain and at much higher levels in the trigeminal ganglia (TG). Replication of both the wild-type and a LAT-negative mutant virus was suppressed in primary embryonic fibroblasts obtained from LAT-expressing transgenic mice compared to that in cells obtained from normal mice. HSV-1 DNA amounts in latently infected TG of transgenic mice were similar to those in normal mice. Reactivation of latent HSV-1 LAT-negative mutants by explant cocultivation of TG from transgenic mice was more efficient than reactivation from normal-mouse TG. Considering our present and previous results, we propose that the significantly higher steady-state level of the 1.5-kb RNA in the TG may link this transcript to latency functions and that by inhibition of virus replication, the LAT gene may protect ganglion cells and thereby increase the probability of reactivation.

A Summer Outbreak of Influenza A Virus Infection among Young Children

In the summer of 2003 in Jerusalem, Israel, 23 children were hospitalized with influenza A virus (A/Fujian/411/02-like virus) infection. The majority were neonates and infants. Clinical manifestations included neonatal fever, bronchitis, bronchiolitis, and pneumonia, and outcomes were favorable. Continued surveillance between epidemic seasons could allow early recognition of influenza strains that will appear in the following influenza season.

Tissue specific distribution of the herpes simplex virus type 1 latency-associated transcripts on polyribosomes during latent infection

Transcription of herpes simplex virus type 1 (HSV-1) during latency produces two abundant latency-associated transcripts (LATs). We have recently shown, that during HSV-1 latency in mice trigeminal ganglia (TG) LATs are bound to polyribosomes (J Virol, 1997, 71, 2897-2904). In order to study the possible role of this binding in the latency process, we now extend the polyribosomal analysis to brainstem tissues of latently infected mice, that unlike TG do not support viral reactivation. We report here that the relative amounts of the LATs associated with polyribosomes in the brainstems of mice are significantly lower than those present in TG. We therefore show that binding of the 1.5 and 2.0 kilobases LATs to polyribosomes is tissue specific and hypothesize that this association may have a role in the reactivation function of HSV-1.

Variant mouse lymphoma cells with modified response to interferon demonstrate enhanced immunogenicity

Abstract We have previously developed an experimental model for the xenogenization of malignant lymphoma. From highly tumorigenic S49 mouse lymphoma cells that proliferate in suspension culture (designated T-25), we selected variant clones that grew as an adherent monolayer (designated T-25-Adh) and were non-tumorigenic in syngeneic mice. Furthermore, priming of syngeneic hosts with T-25-Adh cells protected them against subsequent challenges with the tumorigenic T-25 cells. Several lines of evidence have indicated that antigens of an endogenous mouse mammary tumor virus (MMTV) are involved in the immunogenicity of T-25-Adh cells. Since interferon (IFN) is known to affect retroviral assembly and maturation on the cell membrane, we have studied the effects of IFN on endogenous MMTV-related structures, as well as on the immunogenicity of T-25-Adh cells. We observed that mouse α and β interferons affect the morphogenesis of intracellular MMTV-related precursors in the immunogenic T-25-Adh cells, but not in tumorigenic T-25 cells. From T-25-Adh cells we selected variants that were either high responders or low responders to the above-mentioned interferon effect. The high-response variants were significantly more protective against tumorigenic T-25 cells than the low-response variants. Involvement of MMTV-related antigens in the immune response of the host to T-25-Adh cells was further suggested by immunoelectron-microscopical analysis, demonstrating that antisera from mice, immunized with T-25-Adh cells, interacted specifically with cell-surface MMTV budding particles. These findings indicate a novel method for xenogenization of lymphoma cells by IFN. Since endogenous retroviruses are present in all tissues of the mouse, this approach might be applicable to a wide variety of tumors.