Suppression of bovine viral diarrhea virus replication by small interfering RNA and short hairpin RNA-mediated RNA interference

Bovine viral diarrhea virus (BVDV) is a ubiquitous viral pathogen that affects cattle herds’ worldwide causing significant economic loss. The current strategies to control BVDV infection include vaccination (modified-live or killed) and control of virus spread by enhanced biosecurity management, however, the disease remains prevalent. With the discovery of the sequence-specific method of gene silencing known as RNA interference (RNAi), a new era in antiviral therapies has begun. Here we report the efficient inhibition of BVDV replication by small interfering (siRNA) and short hairpin RNA (shRNA)-mediated gene silencing. siRNAs were generated to target the 5′ non-translated (NTR) region and the regions encoding the C, NS4B and NS5A proteins of the BVDV genome. The siRNAs were first validated using an EGFP/BVDV reporter system and were then shown to suppress BVDV-induced cytopathic effects and viral titers in cell culture with surprisingly different activities compared to the reporter system. Efficient viral suppression was then achieved by bovine 7SK-expressed BVDV-specific shRNAs. Overall, our results demonstrated the use of siRNA and shRNA-mediated gene silencing to achieve efficient inhibition of the  replication of this virus in cell culture.

Hepatitis B Virus transmission and hepatocarcinogenesis: a 9 year retropective cohort of 13676 relatives with hepatocellular carcinoma

Background/Aims
Familial clustering of hepatitis B virus (HBV) infection is related to perinatal transmission, and is the main cause of familial-type hepatocellular carcinoma (HCC). The route of HBV transmission differs between the children and siblings of patients with HCC. This study examined the differences in HBV carrier rates and HCC-related mortality between two generations in HCC families.
Methods
From 1992 to 1997, relatives of individuals with HCC were screened prospectively with ultrasonography, alpha-fetoprotein, liver biochemistry tests and viral markers. Total HCC-related deaths during a 9-year period were compared between the generations of index patients and their children.
Results
The study included a total of 13 676 relatives in two generations. More HCC-related deaths occurred in the index patient generation than in the child generation. Furthermore, children of female index patients had higher rates of liver cancer related mortality than children of male index patients. The same was true when the analysis was limited to male HBV carriers. The prevalence of HBsAg in the offspring of HBsAg positive mothers was 66% in the child generation and 72% in the index patient generation. These high prevalences indicated high maternal HBV replication status.
Conclusions
Perinatal transmission and maternal viral load are important risk factors in hepatocarcinogenesis.

The current pattern of hepatitis B virus infectiion in Australia

Summary. There is little recent data of the seroprevalence of hepatitis B in Australia. We have surveyed a large cohort of endoscopy patients attending a teaching hospital in central Sydney, and related the presence of hepatitis B virus (HBV) markers with putative risk factors for exposure using the SAS statistical package. Of the 2115 patients tested: 2.1% (45/2115) were HBV surface antigen positive, 0.75% (14/2115) viraemic, 9.5% (200/2115) anti-HBs and anti-HBc positive, 20.1% (430/2115) vaccinated (anti-HBs only) and the remaining 70% were susceptible. The adjusted OR of HBV infection was significantly increased in patients who had been diagnosed with human immunodeficiency virus (36.3-fold), born in Asia or Pacific islands (12.4-fold), born in North Africa, Middle East & Mediterranean countries (6-fold) or born abroad elsewhere in the world (2.7-fold), had household contact with someone diagnosed with hepatitis between 1980 and 1990 (3.9-fold), injected drugs between 1980 and 1990 (4.4-fold), resided in a military establishment for 3 months (2.3-fold) or in a hospital for 3 months (2.2-fold), never been vaccinated for hepatitis B (2.8-fold), received blood transfusion due to an accident and/or a haemorrhage (1.92-fold) and finally been a male gender (1.59-fold). The prevalence of HBV in this hospital population was higher than predicted on the basis of notifications to the passive surveillance scheme. Most HBV patients had multiple risk factors for infection, but the hierarchy of odds ratios provides a rational basis for targeted programmes to identify asymptomatic HBV carriers who might benefit from treatment.

The significance of transfusion in the past as a risk for current hepatitis B and Hepatitis C infection: a study in endoscopy patients

BACKGROUND: The objective was to determine the contribution of transfusion in the past to the risk of current infection with hepatitis B or C among patients attending a large hospital for endoscopic procedures.
STUDY DESIGN AND METHODS: Blood samples had been tested for hepatitis markers by routine methods. Patients completed a comprehensive risk factor questionnaire and results were analyzed using computer software.
RESULTS: Twenty-seven percent of the 2120 participants in the study received transfusions in the past. There was no increase in prevalence of hepatitis B among those transfused. Compared with nontransfused participants, recipients of blood before the implementation of hepatitis C virus (HCV) screening in 1990 had a 4.6-fold increased risk of HCV infection, whereas those transfused with screened blood had a 3-fold increased risk. The difference between the odds ratios for patients before and after screening was not significant.
CONCLUSIONS: Because screening has almost completely eliminated HCV from the blood supply, our finding of a continuing association of HCV infection with transfusion was unexpected. It implies that there are significant other nosocomial risks for hepatitis C transmission associated with the clinical situations where patients received blood. These should be actively investigated.

Varicella infection : evidence for peak activity in summer months

This study aimed to identify seasonal variations in the presentation of primary varicella infection in susceptible patients in Victoria (a temperate region in south-east Australia) by analysing Victorian hospital admissions data and medical locum service data from the years preceding the introduction of a universally offered vaccination, complemented by available surveillance data from the neighbouring state, of South Australia. Contrary to the conventional assumption, which is based on observations in temperate regions elsewhere in the world, we found no consistent evidence of seasonal peaks during late winter and early spring for varicella infection in Victoria. This finding may have implications for prevention in temperate regions elsewhere in the world wherever estimations of local seasonal trends have been based on international experiences.

Effects of sexually transmitted infection status, relationship status, and disclosure status on sexual self-concept

Research has indicated that having a sexually transmitted infection (STI) such as genital herpes and genital human papilloma virus (HPV) can have a negative impact on an individual's sexuality. The current study was designed to evaluate the effect of STI status, relationship status, and disclosure status on various dimensions of sexual self-concept. A questionnaire that evaluated the above variables was completed by 117 individuals with genital herpes, 82 individuals with HPV, and 75 individuals with no STI. The results demonstrated that having herpes or HPV had a significant negative impact on aspects of sexual self-concept. It does not appear that an individual's relationship status is a factor associated with the impact of having an STI on the sexual self-concept. Respondents who had disclosed their STI to their partners, however, had significantly more positive feelings about aspects of their sexual self-concept than those who had not disclosed their STI to their partners. The implications of these research findings for health practitioners are discussed.

Reconstructing the incidence of human immunodeficiency virus (HIV) in Hong Kong by using data from HIV positive tests and diagnoses of acquired immune deficiency syndrome

The human immunodeficiency virus–acquired immune deficiency syndrome (HIV–AIDS) epidemic in Hong Kong has been under surveillance in the form of voluntary reporting since 1984. However, there has been little discussion or research on the reconstruction of the HIV incidence curve. This paper is the first to use a modified back-projection method to estimate the incidence of HIV in Hong Kong on the basis of the number of positive HIV tests only. The model proposed has several advantages over the original back-projection method based on AIDS data only. First, not all HIV-infected individuals will develop AIDS by the time of analysis, but some of them may undertake an HIV test; therefore, the HIV data set contains more information than the AIDS data set. Second, the HIV diagnosis curve usually has a smoother pattern than the AIDS diagnosis curve, as it is not affected by redefinition of AIDS. Third, the time to positive HIV diagnosis is unlikely to be affected by treatment effects, as it is unlikely that an individual receives medication before the diagnosis of HIV. Fourth, the induction period from HIV infection to the first HIV positive test is usually shorter than the incubation period which is from HIV infection to diagnosis of AIDS. With a shorter induction period, more information becomes available for estimating the HIV incidence curve. Finally, this method requires the number of positive HIV diagnoses only, which is readily available from HIV–AIDS surveillance systems in many countries. It is estimated that, in Hong Kong, the cumulative number of HIV infections during the period 1979–2000 is about 2600, whereas an estimate based only on AIDS data seems to give an underestimate.

Antibody-mediated protection of plants against infection from potyviruses

Transgenic plants expressing single-chain antibodies have been produced to investigate the feasibility of antibody-mediated broad-spectrum protection against plant virus infections. This study indicates that protection against a wide range of plant viruses can be achieved in transgenic plants expressing a single antibody construct.

Recent advances on the possible neuroprotective activities of Epstein-Barr virus oncogene BARF1 protein in chronic inflammatory disorders of central nervous system

Multiple sclerosis and neurodegenerative diseases in which cells of the central nervous system (CNS) are lost or damaged are rapidly increasing in frequency, and there is neither effective treatment nor cure to impede or arrest their destructive course. The Epstein-Barr virus is a human gamma-herpesvirus that infects more than 90% of the human population worldwide and persisting for the lifetime of the host. It is associated with numerous epithelial cancers, principally undifferentiated nasopharyngeal carcinoma and gastric carcinoma. Individuals with a history of symptomatic primary EBV infection, called infectious mononucleosis, carry a moderately higher risk of developing multiple sclerosis (MS). It is not known how EBV infection potentially promotes autoimmunity and central nervous system (CNS) tissue damage in MS. Recently it has been found that EBV isolates from different geographic regions have highly conserved BARF1 epitopes. BARF1 protein has the neuroprotective and mitogenic activity, thus may be useful to combat and overcome neurodegenerative disease. BARF1 protein therapy can potentially be used to enhance the neuroprotective activities by combinational treatment with anti-inflammatory antagonists and neuroprotectors in neural disorders.

You are what you eat : influence of host ecology on infection risk in populations and individuals

It is widely accepted that wild aquatic birds are the major reservoir for Avian Influenza viruses (AIV), and also play a significant role as vectors for the disease. However, despite intensive surveillance, we still know very little about the role individual wild birds (and their populations) play in the transmission and maintenance of these viruses. Traditionally, combinations of single-location surveillance and historical migration patterns have been used to estimate the degree to which different species may be involved. However, this broad scale approach tends to neglect the ecology of the virus, and just as importantly, the ecology of the host. Over 100 species have been found infected with these viruses worldwide, with many more purportedly negative for the disease. Using data from ten years of wild bird surveillance in the Netherlands we catalogued the ecological properties of each species sampled, in order to determine whether infected species are ecologically separated from those that are not. Using stable isotope analysis of feathers and blood components, we also examine whether infection risk of individuals within a species known to be infected by AIV can be attributable to antecedent foraging habitats. The use of an aquatic habitat is strongly associated with infection risk at all levels analysed, including individuals and populations of a single species, and between species. These unique findings underscore the usefulness of stable isotope methods in disease ecology, particularly when compared to broader-scale inter-species patterns, and the potential role of host ecology in transmission and maintenance of AIV.

Effects of infection-induced migration delays on the epidemiology of avian influenza in wild mallard populations

Wild waterfowl populations form a natural reservoir of Avian Influenza (AI) virus, and fears exist that these birds may contribute to an AI pandemic by spreading the virus along their migratory flyways. Observational studies suggest that individuals infected with AI virus may delay departure from migratory staging sites. Here, we explore the epidemiological dynamics of avian influenza virus in a migrating mallard (Anas platyrhynchos) population with a specific view to understanding the role of infection-induced migration delays on the spread of virus strains of differing transmissibility. We develop a host-pathogen model that combines the transmission dynamics of influenza with the migration, reproduction and mortality of the host bird species. Our modeling predicts that delayed migration of individuals influences both the timing and size of outbreaks of AI virus. We find that (1) delayed migration leads to a lower total number of cases of infection each year than in the absence of migration delay, (2) when the transmission rate of a strain is high, the outbreak starts at the staging sites at which birds arrive in the early part of the fall migration, (3) when the transmission rate is low, infection predominantly occurs later in the season, which is further delayed when there is a migration delay. As such, the rise of more virulent AI strains in waterfowl could lead to a higher prevalence of infection later in the year, which could change the exposure risk for farmed poultry. A sensitivity analysis shows the importance of generation time and loss of immunity for the effect of migration delays. Thus, we demonstrate, in contrast to many current transmission risk models solely using empirical information on bird movements to assess the potential for transmission, that a consideration of infection-induced delays is critical to understanding the dynamics of AI infection along the entire flyway.

Role of position 627 of PB2 and the multibasic cleavage site of the hemagglutinin in the virulence of H5N1 avian influenza virus in chickens and ducks

Highly pathogenic H5N1 avian influenza viruses have caused major disease outbreaks in domestic and free-living birds with transmission to humans resulting in 59% mortality amongst 564 cases. The mutation of the amino acid at position 627 of the viral polymerase basic-2 protein (PB2) from glutamic acid (E) in avian isolates to lysine (K) in human isolates is frequently found, but it is not known if this change affects the fitness and pathogenicity of the virus in birds. We show here that horizontal transmission of A/Vietnam/1203/2004 H5N1 (VN/1203) virus in chickens and ducks was not affected by the change of K to E at PB2-627. All chickens died between 21 to 48 hours post infection (pi), while 70% of the ducks survived infection. Virus replication was detected in chickens within 12 hours pi and reached peak titers in spleen, lung and brain between 18 to 24 hours for both viruses. Viral antigen in chickens was predominantly in the endothelium, while in ducks it was present in multiple cell types, including neurons, myocardium, skeletal muscle and connective tissues. Virus replicated to a high titer in chicken thrombocytes and caused upregulation of TLR3 and several cell adhesion molecules, which may explain the rapid virus dissemination and location of viral antigen in endothelium. Virus replication in ducks reached peak values between 2 and 4 days pi in spleen, lung and brain tissues and in contrast to infection in chickens, thrombocytes were not involved. In addition, infection of chickens with low pathogenic VN/1203 caused neuropathology, with E at position PB2-627 causing significantly higher infection rates than K, indicating that it enhances virulence in chickens.

HIV infection of dendritic cells subverts the IFN induction pathway via IRF-1 and inhibits type 1 IFN production

Many viruses have developed mechanisms to evade the IFN response. Here, HIV-1 was shown to induce a distinct subset of IFN-stimulated genes (ISGs) in monocyte-derived dendritic cells (DCs), without detectable type I or II IFN. These ISGs all contained an IFN regulatory factor 1 (IRF-1) binding site in their promoters, and their expression was shown to be driven by IRF-1, indicating this subset was induced directly by viral infection by IRF-1. IRF-1 and -7 protein expression was enriched in HIV p24 antigen-positive DCs. A HIV deletion mutant with the IRF-1 binding site deleted from the long terminal repeat showed reduced growth kinetics. Early and persistent induction of IRF-1 was coupled with sequential transient up-regulation of its 2 inhibitors, IRF-8, followed by IRF-2, suggesting a mechanism for IFN inhibition. HIV-1 mutants with Vpr deleted induced IFN, showing that Vpr is inhibitory. However, HIV IFN inhibition was mediated by failure of IRF-3 activation rather than by its degradation, as in T cells. In contrast, herpes simplex virus type 2 markedly induced IFNβ and a broader range of ISGs to higher levels, supporting the hypothesis that HIV-1 specifically manipulates the induction of IFN and ISGs to enhance its noncytopathic replication in DCs.

X4 and R5 HIV-1 have distinct post-entry requirements for uracil DNA glycosylase during infection of primary cells

It has been assumed that R5 and X4 HIV utilize similar strategies to support viral cDNA synthesis post viral entry. In this study, we provide evidence to show that R5 and X4 HIV have distinct requirements for host cell uracil DNA glycosylase (UNG2) during the early stage of infection. UNG2 has been previously implicated in HIV infection, but its precise role remains controversial. In this study we show that, although UNG2 is highly expressed in different cell lines, UNG2 levels are low in the natural host cells of HIV. Short interfering RNA knockdown of endogenous UNG2 in primary cells showed that UNG2 is required for R5 but not X4 HIV infection and that this requirement is bypassed when HIV enters the target cell via vesicular stomatitis virus envelope-glycoprotein-mediated endocytosis. We also show that short interfering RNA knockdown of UNG2 in virus-producing primary cells leads to defective R5 HIV virions that are unable to complete viral cDNA synthesis. Quantitative PCR analysis revealed that endogenous UNG2 levels are transiently up-regulated post HIV infection, and this increase in UNG2 mRNA is ∼10–20 times higher in R5 versus X4 HIV-infected cells. Our data show that both virion-associated UNG2 and HIV infection-induced UNG2 expression are critical for reverse transcription during R5 but not X4 HIV infection. More importantly, we have made the novel observation that R5 and X4 HIV have distinct host cell factor requirements and differential capacities to induce gene expression during the early stages of infection. These differences may result from activation of distinct signaling cascades and/or infection of divergent T-lymphocyte subpopulations.

DNA found in human immunodeficiency virus type 1 particles may not be required for infectivity

We have studied the presence and significance of retroviral genome-derived DNA in the core of human immunodeficiency virus (HIV) particles produced from transfections of HXB2 expression vectors in COS-7 cells and from HIV type 1 IIIB chronically infected H9 cells. Viruses purified by sucrose cushion centrifugation and treated with DNase I contained 1000-fold more viral RNA than DNA. However protease-defective viruses that contained only pl60 ga~p°z had less than 100 times the amount of DNA in their cores than wild-type viruses suggesting that the p66/p51 form of reverse transcriptase was responsible for DNA transcription. Viruses produced by transfections in the presence of 3'-azido-3'-deoxythymidine (AZT) contained the viral RNA genome but only DNA of premature length because of the chain terminating effects of AZT. However such viruses were as infectious for CD4 + cells as wild-type virus. We conclude that retrovirus-derived DNA in HIV-1 particles is not required for infection and does not play a significant role in this process.