Showing papers on "Virus published in 1999"

Replication of Subgenomic Hepatitis C Virus RNAs in a Hepatoma Cell Line

Abstract: An estimated 170 million persons worldwide are infected with hepatitis C virus (HCV), a major cause of chronic liver disease. Despite increasing knowledge of genome structure and individual viral proteins, studies on virus replication and pathogenesis have been hampered by the lack of reliable and efficient cell culture systems. A full-length consensus genome was cloned from viral RNA isolated from an infected human liver and used to construct subgenomic selectable replicons. Upon transfection into a human hepatoma cell line, these RNAs were found to replicate to high levels, permitting metabolic radiolabeling of viral RNA and proteins. This work defines the structure of HCV replicons functional in cell culture and provides the basis for a long-sought cellular system that should allow detailed molecular studies of HCV and the development of antiviral drugs.

Control of Viremia in Simian Immunodeficiency Virus Infection by CD8+ Lymphocytes

Abstract: Clinical evidence suggests that cellular immunity is involved in controlling human immunodeficiency virus-1 (HIV-1) replication. An animal model of acquired immune deficiency syndrome (AIDS), the simian immunodeficiency virus (SIV)-infected rhesus monkey, was used to show that virus replication is not controlled in monkeys depleted of CD8+ lymphocytes during primary SIV infection. Eliminating CD8+ lymphocytes from monkeys during chronic SIV infection resulted in a rapid and marked increase in viremia that was again suppressed coincident with the reappearance of SIV-specific CD8+ T cells. These results confirm the importance of cell-mediated immunity in controlling HIV-1 infection and support the exploration of vaccination approaches for preventing infection that will elicit these immune responses.

Generation of influenza A viruses entirely from cloned cDNAs

Abstract: We describe a new reverse-genetics system that allows one to efficiently generate influenza A viruses entirely from cloned cDNAs. Human embryonic kidney cells (293T) were transfected with eight plasmids, each encoding a viral RNA of the A/WSN/33 (H1N1) or A/PR/8/34 (H1N1) virus, flanked by the human RNA polymerase I promoter and the mouse RNA polymerase I terminator—together with plasmids encoding viral nucleoprotein and the PB2, PB1, and PA viral polymerases. This strategy yielded >1 × 103 plaque-forming units (pfu) of virus per ml of supernatant at 48 hr posttransfection. The addition of plasmids expressing all of the remaining viral structural proteins led to a substantial increase in virus production, 3 × 104–5 × 107 pfu/ml. We also used reverse genetics to generate a reassortant virus containing the PB1 gene of the A/PR/8/34 virus, with all other genes representing A/WSN/33. Additional viruses produced by this method had mutations in the PA gene or possessed a foreign epitope in the head of the neuraminidase protein. This efficient system, which does not require helper virus infection, should be useful in viral mutagenesis studies and in the production of vaccines and gene therapy vectors.

Viral Clearance Without Destruction of Infected Cells During Acute HBV Infection

Abstract: Viral clearance during hepatitis B virus (HBV) infection has been thought to reflect the destruction of infected hepatocytes by CD8 + T lymphocytes. However, in this study, HBV DNA was shown to largely disappear from the liver and the blood of acutely infected chimpanzees long before the peak of T cell infiltration and most of the liver disease. These results demonstrate that noncytopathic antiviral mechanisms contribute to viral clearance during acute viral hepatitis by purging HBV replicative intermediates from the cytoplasm and covalently closed circular viral DNA from the nucleus of infected cells.

Shorter Survival in Advanced Human Immunodeficiency Virus Type 1 Infection Is More Closely Associated with T Lymphocyte Activation than with Plasma Virus Burden or Virus Chemokine Coreceptor Usage

Abstract: To define predictors of survival time in late human immunodeficiency virus type 1 (HIV-1) disease, long- and short-duration survivors were studied after their CD4+ T cells fell to

Hepatitis C virus and other Flaviviridae viruses enter cells via low density lipoprotein receptor

Abstract: Endocytosis of the Flaviviridae viruses, hepatitis C virus, GB virus C/hepatitis G virus, and bovine viral diarrheal virus (BVDV) was shown to be mediated by low density lipoprotein (LDL) receptors on cultured cells by several lines of evidence: by the demonstration that endocytosis of these virus correlated with LDL receptor activity, by complete inhibition of detectable endocytosis by anti-LDL receptor antibody, by inhibition with anti-apolipoprotein E and -apolipoprotein B antibodies, by chemical methods abrogating lipoprotein/LDL receptor interactions, and by inhibition with the endocytosis inhibitor phenylarsine oxide. Confirmatory evidence was provided by the lack of detectable LDL receptor on cells known to be resistant to BVDV infection. Endocytosis via the LDL receptor was shown to be mediated by complexing of the virus to very low density lipoprotein or LDL but not high density lipoprotein. Studies using LDL receptor-deficient cells or a cytolytic BVDV system indicated that the LDL receptor may be the main but not exclusive means of cell entry of these viruses. Studies on other types of viruses indicated that this mechanism may not be exclusive to Flaviviridae but may be used by viruses that associate with lipoprotein in the blood. These findings provide evidence that the family of LDL receptors may serve as viral receptors.

Generation of bovine respiratory syncytial virus (BRSV) from cDNA: BRSV NS2 is not essential for virus replication in tissue culture, and the human RSV leader region acts as a functional BRSV genome promoter.

Abstract: In order to generate recombinant bovine respiratory syncytial virus (BRSV), the genome of BRSV strain A51908, variant ATue51908, was cloned as cDNA. We provide here the sequence of the BRSV genome ends and of the entire L gene. This completes the sequence of the BRSV genome, which comprises a total of 15,140 nucleotides. To establish a vaccinia virus-free recovery system, a BHK-derived cell line stably expressing T7 RNA polymerase was generated (BSR T7/5). Recombinant BRSV was reproducibly recovered from cDNA constructs after T7 RNA polymerase-driven expression of antigenome sense RNA and of BRSV N, P, M2, and L proteins from transfected plasmids. Chimeric viruses in which the BRSV leader region was replaced by the human respiratory syncytial virus (HRSV) leader region replicated in cell culture as efficiently as their nonchimeric counterparts, demonstrating that all cis-acting sequences of the HRSV promoter are faithfully recognized by the BRSV polymerase complex. In addition, we report the successful recovery of a BRSV mutant lacking the complete NS2 gene, which encodes a nonstructural protein of unknown function. The NS2-deficient BRSV replicated autonomously and could be passaged, demonstrating that NS2 is not essential for virus replication in cell culture. However, growth of the mutant was considerably slower than and final infectious titers were reduced by a factor of at least 10 compared to wild-type BRSV, indicating that NS2 provides a supporting factor required for full replication capacity.

Sexual transmission and propagation of SIV and HIV in resting and activated CD4+ T cells.

Abstract: In sexual transmission of simian immunodeficiency virus, and early and later stages of human immunodeficiency virus-type 1 (HIV-1) infection, both viruses were found to replicate predominantly in CD4(+) T cells at the portal of entry and in lymphoid tissues. Infection was propagated not only in activated and proliferating T cells but also, surprisingly, in resting T cells. The infected proliferating cells correspond to the short-lived population that produces the bulk of HIV-1. Most of the HIV-1-infected resting T cells persisted after antiretroviral therapy. Latently and chronically infected cells that may be derived from this population pose challenges to eradicating infection and developing an effective vaccine.

Rescue of Influenza A Virus from Recombinant DNA

Abstract: We have rescued influenza A virus by transfection of 12 plasmids into Vero cells. The eight individual negative-sense genomic viral RNAs were transcribed from plasmids containing human RNA polymerase I promoter and hepatitis delta virus ribozyme sequences. The three influenza virus polymerase proteins and the nucleoprotein were expressed from protein expression plasmids. This plasmid-based reverse genetics technique facilitates the generation of recombinant influenza viruses containing specific mutations in their genes.

Quantifying residual HIV-1 replication in patients receiving combination antiretroviral therapy.

Abstract: Background In patients infected with human immunodeficiency virus type 1 (HIV-1), combination antiretroviral therapy can result in sustained suppression of plasma levels of the virus. However, replication-competent virus can still be recovered from latently infected resting memory CD4 lymphocytes; this finding raises serious doubts about whether antiviral treatment can eradicate HIV-1. Methods We looked for evidence of residual HIV-1 replication in eight patients who began treatment soon after infection and in whom plasma levels of HIV-1 RNA were undetectable after two to three years of antiretroviral therapy. We examined whether there had been changes over time in HIV-1 proviral sequences in peripheral-blood mononuclear cells, which would indicate residual viral replication. We also performed in situ hybridization studies on tissues from one patient to identify cells actively expressing HIV-1 RNA. We estimated the rate of decrease of latent, replication-competent HIV-1 in resting CD4 lymphocytes on the b...

A universal influenza A vaccine based on the extracellular domain of the M2 protein.

Abstract: The antigenic variation of influenza virus represents a major health problem. However, the extracellular domain of the minor, virus-coded M2 protein is nearly invariant in all influenza A strains. We genetically fused this M2 domain to the hepatitis B virus core (HBc) protein to create fusion gene coding for M2HBc; this gene was efficiently expressed in Escherichia coli. Intraperitoneal or intranasal administration of purified M2HBc particles to mice provided 90-100% protection against a lethal virus challenge. The protection was mediated by antibodies, as it was transferable by serum. The enhanced immunogenicity of the M2 extracellular domain exposed on HBc particles allows broad-spectrum, long-lasting protection against influenza A infections.

Immune responses to adenovirus and adeno-associated virus in humans.

Abstract: Vectors based on human adenovirus (Ad) and adeno-associated virus (AAV) are being evaluated for human gene therapy. The response of the host to the vector, in terms of antigen-specific immunity, will play a substantial role in clinical outcome. We have surveyed cohorts of normal subjects and cystic fibrosis patients for pre-existing immunity to these viruses, caused by naturally acquired infections. A number of humoral and cellular assays to adenovirus serotype 5 (Ad5) and adeno-associated virus serotype 2 (AAV2) were performed from serum and peripheral blood mononuclear cells. Virtually all subjects had Ig to Ad5 although only 55% of these antibodies neutralized virus (NAB). Approximately two of three patients demonstrated CD4+ T cells that proliferated to Ad antigens of which most were of the TH1 subset, based on cytokine secretion. A substantially different pattern of immune responses was observed to AAV2. Although virtually all patients had Ig to AAV2, most of these antibodies were not neutralizing (32% NAB) and only 5% of patients had peripheral blood lymphocytes that proliferated in response to AAV2 antigens. These studies demonstrate marked heterogeneity in pre-existing immunity to Ad5 and AAV2 in human populations. The impact of these findings on outcome following gene therapy will require further study.

αVβ5 integrin: a co-receptor for adeno-associated virus type 2 infection

Abstract: Understanding the primary steps of viral entry can have important implications for strategies to prevent infection of known viral pathogens as well as determining parameters for efficient gene delivery using viral vectors. Recently, a two-step process for viral infection involving attachment of virus to a primary receptor (coxsackievirus adenovirus receptor and heparan sulfate proteoglycan) and subsequent mediation of virus entry by a co-receptor (αV integrins and HVEM) has been determined for both adenovirus and HSV, respectively 1, 2, 3, 4 . Heparan sulfate proteoglycan serves as a primary attachment receptor for adeno-associated virus type 2 (AAV-2)( ref. 5 ). Here we determined that αVβ5 integrin plays a part in efficient AAV infection. Experiments using the chelating agent EDTA to disrupt integrin function resulted in a corresponding decrease in AAV infection, consistent with the possibility that integrin mediates infection. Viral overlay experiments on purified plasma membrane proteins as well as immunoprecipitated integrin β5 subunit demonstrated that AAV directly associates with the β5 subunit of αVβ5 integrin. Genetically defined cells expressing αVβ5 integrin showed increased susceptibility to AAV infection, demonstrating a biological role of this integrin in AAV infection. Finally, viral binding and internalization studies indicate that αVβ5 integrin is not a primary attachment receptor for AAV-2, but is instead involved in facilitating virus internalization. This study supports the idea that αVβ5 integrin serves as a co-receptor for AAV-2 virions, and should have a substantial effect on the use of AAV vectors in human gene therapy.

Molecular characterization of H9N2 influenza viruses: Were they the donors of the “internal” genes of H5N1 viruses in Hong Kong?

Abstract: The origin of the H5N1 influenza viruses that killed six of eighteen infected humans in 1997 and were highly pathogenic in chickens has not been resolved. These H5N1 viruses transmitted directly to humans from infected poultry. In the poultry markets in Hong Kong, both H5N1 and H9N2 influenza viruses were cocirculating, raising the possibility of genetic reassortment. Here we analyze the antigenic and genetic features of H9N2 influenza viruses with different epidemiological backgrounds. The results suggest that the H9N2 influenza viruses of domestic ducks have become established in the domestic poultry of Asia. Phylogenetic and antigenic analyses of the H9N2 viruses isolated from Hong Kong markets suggest three distinct sublineages. Among the chicken H9N2 viruses, six of the gene segments were apparently derived from an earlier chicken H9N2 virus isolated in China, whereas the PB1 and PB2 genes are closely related to those of the H5N1 viruses and a quail H9N2 virus—A/quail/Hong Kong/G1/97 (Qa/HK/G1/97)—suggesting that many of the 1997 chicken H9 isolates in the markets were reassortants. The similarity of the internal genes of Qa/HK/G1/97 virus to those of the H5N1 influenza viruses suggests that the quail virus may have been the internal gene donor. Our findings indicate that the human and poultry H5N1 influenza viruses in Hong Kong in 1997 were reassortants that obtained internal gene segments from Qa/HK/G1/97. However, we cannot be certain whether the replicate complex of H5N1 originated from Qa/HK/G1/97 or whether the reverse transfer occurred; the available evidence supports the former proposal.

The Surface Glycoproteins of H5 Influenza Viruses Isolated from Humans, Chickens, and Wild Aquatic Birds Have Distinguishable Properties

Abstract: In 1997, 18 confirmed cases of human influenza arising from multiple independent transmissions of H5N1 viruses from infected chickens were reported from Hong Kong. To identify possible phenotypic changes in the hemagglutinin (HA) and neuraminidase (NA) of the H5 viruses during interspecies transfer, we compared the receptor-binding properties and NA activities of the human and chicken H5N1 isolates from Hong Kong and of H5N3 and H5N1 viruses from wild aquatic birds. All H5N1 viruses, including the human isolate bound to Sia2-3Gal-containing receptors but not to Sia2-6Gal-containing receptors. This finding formally demonstrates for the first time that receptor specificity of avian influenza viruses may not restrict initial avian-to-human transmission. The H5N1 chicken viruses differed from H5 viruses of wild aquatic birds by a 19-amino-acid deletion in the stalk of the NA and the presence of a carbohydrate at the globular head of the HA. We found that a deletion in the NA decreased its ability to release the virus from cells, whereas carbohydrate at the HA head decreased the affinity of the virus for cell receptors. Comparison of amino acid sequences from GenBank of the HAs and NAs from different avian species revealed that additional glycosylation of the HA and a shortened NA stalk are characteristic features of the H5 and H7 chicken viruses. This finding indicates that changes in both HA and NA may be required for the adaptation of influenza viruses from wild aquatic birds to domestic chickens and raises the possibility that chickens may be a possible intermediate host in zoonotic transmission.

Neutralizing antibody directed against the HIV-1 envelope glycoprotein can completely block HIV-1/SIV chimeric virus infections of macaque monkeys.

Abstract: Virus–specific antibodies protect individuals against a wide variety of viral infections1–7. To assess whether human immunodeficiency virus type 1 (HIV–1) envelope–specific antibodies confer resistance against primate lentivirus infections, we purified immunoglobulin (IgG) from chimpanzees infected with several different HIV–1 isolates, and used this for passive immunization of pig–tailed macaques. These monkeys were subsequently challenged intravenously with a chimeric simian–human immunodeficiency virus (SHIV) bearing an envelope glycoprotein derived form HIV–1DH12, a dual–tropic primary virus isolate. Here we show that anti–SHIV neutralizing activity, determined in vitro using an assay measuring loss of infectivity, is the absolute requirement for antibody–mediated protection in vivo. Using an assay that measures 100% neutralization, the titer in plasma for complete protection of the SHIV–challenged macaques was in the range of 1:5–1:8. The HIV–1–specific neutralizing antibodies studied are able to bind to native gp120 present on infectious virus particles. Administration of non–neutralizing anti–HIV IgG neither inhibited nor enhanced a subsequent SHIV infection.

Quantitative Analysis of Epstein-Barr Virus Load by Using a Real-Time PCR Assay

Abstract: To measure the virus load in patients with symptomatic Epstein-Barr virus (EBV) infections, we used a real-time PCR assay to quantify the amount of EBV DNA in blood. The real-time PCR assay could detect from 2 to over 10(7) copies of EBV DNA with a wide linear range. We estimated the virus load in peripheral blood mononuclear cells (PBMNC) from patients with symptomatic EBV infections. The mean EBV-DNA copy number in the PBMNC was 10(3.7) copies/microg of DNA in patients with EBV-related lymphoproliferative disorders, 10(4.1) copies/microg of DNA in patients with chronic active EBV infections, and 10(2.2) copies/microg of DNA in patients with infectious mononucleosis. These numbers were significantly larger than those in either posttransplant patients or immunocompetent control patients without EBV-related diseases. In a patient with infectious mononucleosis, the virus load decreased as the symptoms resolved. The copy number of EBV DNA in PBMNC from symptomatic EBV infections was correlated with the EBV-positive cell number determined by the in situ hybridization assay (r = 0.842; P < 0.0001). These results indicate that the real-time PCR assay is useful for diagnosing symptomatic EBV infection and for monitoring the virus load.

Population biology of HIV-1 infection: viral and CD4+ T cell demographics and dynamics in lymphatic tissues.

Abstract: Human immunodeficiency virus-1 (HIV-1) is usually transmitted through sexual contact and in the very early stages of infection establishes a persistent infection in lymphatic tissues (LT) Virus is produced and stored at this site in a dynamic process that slowly depletes the immune system of CD4+ T cells, setting the stage for AIDS In this review, I describe the changes in viral and CD4+ T cell populations in LT over the course of infection and after treatment I present recent evidence that productively infected CD4+ T cells play an important role in establishing persistent infection from the onset, and that the LT are the major reservoir where virus is produced and stored on follicular dendritic cells (FDCs) I discuss the methods used to define the size of viral and CD4+ T cell populations in LT and the nature of virus-host cell interactions in vivo These experimental approaches have identified populations of latently and chronically infected cells in which virus can elude host defenses, perpetuate infection, and escape eradication by highly active antiretroviral treatment (HAART) I discuss the dramatic impact of HAART on suppressing virus production, reducing the pool of stored virus, and restoring CD4+ T cell populations I discuss the contributions of thymopoiesis and other renewal mechanisms, lymphatic homeostasis and trafficking to these changes in CD4+ T cell populations in LT, and conclude with a model of immune depletion and repopulation based on the limited regenerative capacity of the adult and the uncompensated losses of productively infected cells that treatment stems The prediction of this model is that immune regeneration will be slow, variable, and partial It is nonetheless encouraging to know that even in late stages of infection, control of active replication of HIV-1 provides an opportunity for the immune system to recover from the injuries inflicted by infection

Origin and evolution of the 1918 “Spanish” influenza virus hemagglutinin gene

Abstract: The "Spanish" influenza pandemic killed over 20 million people in 1918 and 1919, making it the worst infectious pandemic in history. Here, we report the complete sequence of the hemagglutinin (HA) gene of the 1918 virus. Influenza RNA for the analysis was isolated from a formalin-fixed, paraffin-embedded lung tissue sample prepared during the autopsy of a victim of the influenza pandemic in 1918. Influenza RNA was also isolated from lung tissue samples from two additional victims of the lethal 1918 influenza: one formalin-fixed, paraffin-embedded sample and one frozen sample obtained by in situ biopsy of the lung of a victim buried in permafrost since 1918. The complete coding sequence of the A/South Carolina/1/18 HA gene was obtained. The HA1 domain sequence was confirmed by using the two additional isolates (A/New York/1/18 and A/Brevig Mission/1/18). The sequences show little variation. Phylogenetic analyses suggest that the 1918 virus HA gene, although more closely related to avian strains than any other mammalian sequence, is mammalian and may have been adapting in humans before 1918.

A Re-Evaluation of the Frequency of CD8+ T Cells Specific for EBV in Healthy Virus Carriers

Abstract: EBV is a gammaherpesvirus that can establish both nonproductive (latent) and productive (lytic) infections within the cells of its host. Although T cell responses to EBV latent proteins have been well characterized, little is known about the importance of responses to lytic proteins in long term virus carriers. Here we have compared the frequencies of CD8+ T cells specific for EBV latent and lytic Ags in healthy virus carriers, using three techniques: limiting dilution analysis, enzyme-linked immunospot assay, and FACS staining with tetrameric MHC-peptide complexes. T cells specific for EBV lytic protein epitopes were readily detectable in all donors and were usually more abundant than those specific for latent epitopes. We infer that direct T cell control of viral replicative lesions is maintained in long term carriers of EBV and is an important component of the immune response to this virus. Estimates of CD8+ T cell frequencies varied considerably according to methodology; values obtained from MHC-peptide tetramer staining were, on the average, 4.4-fold higher than those obtained from enzyme-linked immunospot assays, which were, in turn, on the average, 5.3-fold higher than those obtained from limiting dilution analysis. Tetramer staining showed that as many as 5.5% circulating CD8+ T cells in a virus carrier were specific for a single EBV lytic protein epitope. Such values are much greater than previously imagined and illustrate how antigenic challenge from a persistent herpesvirus can influence the composition of the host's CD8+ T cell pool.

Rescue of Newcastle disease virus from cloned cDNA: evidence that cleavability of the fusion protein is a major determinant for virulence

Abstract: A full-length cDNA clone of Newcastle disease virus (NDV) vaccine strain LaSota was assembled from subgenomic overlapping cDNA fragments and cloned in a transcription plasmid between the T7 RNA polymerase promoter and the autocatalytic hepatitis delta virus ribozyme. Transfection of this plasmid into cells that were infected with a recombinant fowlpoxvirus that expressed T7 RNA polymerase, resulted in the synthesis of antigenomic NDV RNA. This RNA was replicated and transcribed by the viral NP, P, and L proteins, which were expressed from cotransfected plasmids. After inoculation of the transfection supernatant into embryonated specific-pathogen-free eggs, infectious virus derived from the cloned cDNA was recovered. By introducing three nucleotide changes in the cDNA, we generated a genetically tagged derivative of the LaSota strain in which the amino acid sequence of the protease cleavage site (GGRQGR↓L) of the fusion protein F0 was changed to the consensus cleavage site of virulent NDV strains (GRRQRR↓F). Pathogenicity tests in day-old chickens showed that the strain derived from the unmodified cDNA was completely nonvirulent (intracerebral pathogenicity index [ICPI] = 0.00). However, the strain derived from the cDNA in which the protease cleavage site was modified showed a dramatic increase in virulence (ICPI = 1.28 out of a possible maximum of 2.0). Pulse-chase labeling of cells infected with the different strains followed by radioimmunoprecipitation of the F protein showed that the efficiency of cleavage of the F0 protein was greatly enhanced by the amino acid replacements. These results demonstrate that genetically modified NDV can be recovered from cloned cDNA and confirm the supposition that cleavage of the F0 protein is a key determinant in virulence of NDV.

HIV-1 drug resistance in newly infected individuals.

Abstract: ContextThere is concern that the widespread use of antiretroviral drugs to treat human immunodeficiency virus 1 (HIV-1) infection may result in the increased transmission of drug-resistant virus.ObjectiveTo determine the prevalence of drug resistance–conferring mutations and phenotypic resistance to antiretroviral agents in a cohort of individuals newly infected with HIV-1.DesignCase series with genetic analyses of the HIV-1 plasma-derived pol gene using reverse transcriptase polymerase chain reaction followed by direct sequencing of polymerase chain reaction products. Phenotypic analysis was performed with a recombinant virus assay.Setting and PatientsEighty individuals referred, on average, 1.7 months after infection with HIV-1 to the Aaron Diamond AIDS Research Center between July 1995 and April 1999. Subjects were from large urban areas (65 from New York, NY; 11 from Los Angeles, Calif); 60 (75%) were white, and 75 (93.8%) were homosexual men.Main Outcome MeasuresPrevalence of known resistance-conferring genotypes and reduced susceptibility to individual antiviral agents by phenotype.ResultsThirteen individuals (16.3%) had genotypes associated with drug resistance to any antiretroviral agent. Virus with known resistance-conferring mutations to any nucleoside reverse transcriptase inhibitors was found in 10 individuals, to any nonnucleoside reverse transcriptase inhibitors in 6 subjects, and to any protease inhibitors in 2 cases. Multidrug-resistant virus was identified in 3 individuals (3.8%). Extensive polymorphism in the protease gene was identified. Interpretation of genotypes and phenotypes was concordant in 57 (85%) of the 67 cases in which both studies were performed.ConclusionThe prevalence of HIV-1 variants with known resistance-conferring genotypes to any antiretroviral agent in this cohort of 80 newly infected individuals is 16.3%. These data support expanded use of resistance testing in the setting of primary HIV-1 infection. Clinical trials should be initiated to establish whether therapy guided by resistance testing, compared with the use of empirical triple combination antiretroviral therapy, provides additional virological and immunological benefit when treating primary HIV-1 infection. Further efforts to expand the study of transmission of drug-resistant HIV-1 variants, particularly in cohorts with different epidemiological profiles, are indicated.

Gene silencing without DNA. rna-mediated cross-protection between viruses

Abstract: Previously, it was shown that the upper leaves of plants infected with nepoviruses and caulimoviruses are symptom free and contain reduced levels of virus. These leaves are said to be recovered. Recovery is associated with RNA-mediated cross-protection against secondary virus infection. Here, by analyzing plants infected with viruses that are quite distinct from the nepovirus or caulimovirus groups, we demonstrate that this RNA-mediated defense is a general response to virus infection. Upon infection with a tobravirus, plants exhibited RNA-mediated cross-protection and recovery, as occurs in nepovirus-infected plants. However, upon infection with a potexvirus, plants exhibited RNA-mediated cross-protection without recovery. In both instances, a transient gene expression assay showed that RNA-mediated cross-protection was functionally equivalent to post-transcriptional gene silencing. Combined, these data provide direct evidence that post-transcriptional gene silencing of nuclear genes is a manifestation of a natural defense mechanism that is induced by a wide range of viruses.

Tuberculosis and Chronic Hepatitis B Virus Infection in Africans and Variation in the Vitamin D Receptor Gene

Abstract: The active metabolite of vitamin D, 1,25 dihydroxyvitamin D3, is an important immunoregulatory hormone [1]. Its effects are exerted by interaction with the vitamin D receptor, which is present on human monocytes and activated T and B lymphocytes. Variation in the vitamin D receptor gene was typed in 2015 subjects from large case-control studies of three major infectious diseases: tuberculosis, malaria, and hepatitis B virus. Homozygotes for a polymorphism at codon 352 (genotype tt) were significantly underrepresented among those with tuberculosis (X 2 = 6.22, 1 df, P =.01) and persistent hepatitis B infection (X 2 = 6.25, 1 df, P =.01) but not in subjects with clinical malaria compared with the other genotypes. Therefore, this genetic variant, which predisposes to low bone mineral density in many populations, may confer resistance to certain infectious diseases.