Innate and adaptive immune responses against picornaviruses and their counteractions: An overview

Picornaviruses, small positive-stranded RNA viruses, cause a wide range of diseases which is based on their differential tissue and cell type tropisms. This diversity is reflected by the immune responses, both innate and adaptive, induced after infection, and the subsequent interactions of the viruses with the immune system. The defense mechanisms of the host and the countermeasures of the virus significantly contribute to the pathogenesis of the infections. Important human pathogens are poliovirus, coxsackievirus, human rhinovirus and hepatitis A virus. These viruses are the best-studied members of the family, and in this review we want to present the major aspects of the reciprocal effects between the immune system and these viruses.

Molecular and clinical aspects of hepatitis D virus infections

Hepatitis D virus (HDV) is a defective virus with circular, single-stranded genomic RNA which needs hepatitis B virus (HBV) as a helper virus for virion assembly and infectivity. HDV virions are composed of a circular shape HDV RNA and two types of viral proteins, small and large HDAgs, surrounded by HBV surface antigen (HBsAg). The RNA polymerase II from infected hepatocytes is responsible for synthesizing RNAs with positive and negative polarities for HDV, as the virus does not code any enzyme to replicate its genome. HDV occurs as co-infection or super-infection in up to 5% of HBsAg carriers. A recent multi-center study highlighted that pegylated interferon α-2a (PEG-IFN) is currently the only treatment option for delta hepatitis. Nucleotide/nucleoside analogues, which are effective against HBV, have no relevant effects on HDV. However, additional clinical trials combining PEG-IFN and tenofovir are currently ongoing. The molecular interactions between HDV and HBV are incompletely understood. Despite fluctuating patterns of HBV viral load in the presence of HDV in patients, several observations indicate that HDV has suppressive effects on HBV replication, and even in triple infections with HDV, HBV and HCV, replication of both concomitant viruses can be reduced. Additional molecular virology studies are warranted to clarify how HDV interacts with the helper virus and which key cellular pathways are used by both viruses. Further clinical trials are underway to optimize treatment strategies for delta hepatitis.

Selection of RNAi-based inhibitors for anti-HIV gene therapy

In the last decade, RNA interference (RNAi) advanced to one of the most widely applied techniques in the biomedical research field and several RNAi therapeutic clinical trials have been launched. We focus on RNAi-based inhibitors against the chronic infection with human immunodeficiency virus type 1 (HIV-1). A lentiviral gene therapy is proposed for HIV-infected patients that will protect and reconstitute the vital immune cell pool. The RNAi-based inhibitors that have been developed are short hairpin RNA molecules (shRNAs), of which multiple are needed to prevent viral escape. In ten distinct steps, we describe the selection process that started with 135 shRNA candidates, from the initial design criteria, via testing of the in vitro and in vivo antiviral activity and cytotoxicity to the final design of a combinatorial therapy with three shRNAs. These shRNAs satisfied all 10 selection criteria such as targeting conserved regions of the HIV-1 RNA genome, exhibiting robust inhibition of HIV-1 replication and having no impact on cell physiology. This combinatorial shRNA vector will soon move forward to the first clinical studies.

Roles of the two distinct proteasome pathways in hepatitis C virus infection

Hepatitis C virus (HCV) infection often causes chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The development of a HCV cell culture system enabled us to investigate its whole HCV life cycle and develop a better understanding of the pathogenesis of this virus. Post-translational modification plays a crucial role in HCV replication and in the maturation of viral particles. There is growing evidence also suggesting that the ubiquitin-proteasome pathway and the ubiquitin-independent proteasome pathway are involved in the stability control of HCV proteins. Many viruses are known to manipulate the proteasome pathways to modulate the cell cycle, inhibit apoptosis, evade the immune system, and activate cell signaling, thereby contributing to persistent infection and viral carcinogenesis. The identification of functional interactions between HCV and the proteasome pathways will therefore shed new light on the life cycle and pathogenesis of HCV. This review summarizes the current knowledge on the involvement of the ubiquitin-dependent and -independent proteasome pathways in HCV infection and discusses the roles of these two distinct mechanisms in HCV pathogenesis.

West Nile virus: A re-emerging pathogen revisited

West Nile virus (WNV), a flavivirus of the Flaviviridae family, is maintained in nature in an enzootic transmission cycle between avian hosts and ornithophilic mosquito vectors, although the virus occasionally infects other vertebrates. WNV causes sporadic disease outbreaks in horses and humans, which may result in febrile illness, meningitis, encephalitis and flaccid paralysis. Until recently, its medical and veterinary health concern was relatively low; however, the number, frequency and severity of outbreaks with neurological consequences in humans and horses have lately increased in Europe and the Mediterranean basin. Since its introduction in the Americas, the virus spread across the continent with worrisome consequences in bird mortality and a considerable number of outbreaks among humans and horses, which have resulted in the largest epidemics of neuroinvasive WNV disease ever documented. Surprisingly, its incidence in human and animal health is very different in Central and South America, and the reasons for it are not yet understood. Even though great advances have been obtained lately regarding WNV infection, and although efficient equine vaccines are available, no specific treatments or vaccines for human use are on the market. This review updates the most recent investigations in different aspects of WNV life cycle: molecular virology, transmission dynamics, host range, clinical presentations, epidemiology, ecology, diagnosis, control, and prevention, and highlights some aspects that certainly require further research.

Delivery strategies for novel vaccine formulations

A major challenge in vaccine design is to identify antigen presentation and delivery systems capable of rapidly stimulating both the humoral and cellular components of the immune system to elicit a strong and sustained immunity against different viral isolates. Approaches to achieve this end involve live attenuated and inactivated virions, viral vectors, DNA, and protein subunits. This review reports the state of current antigen delivery, and focuses on two innovative systems recently established at our labs. These systems are the filamentous bacteriophage fd and an icosahedral scaffold formed by the acyltransferase component (E2 protein) of the pyruvate dehydrogenase complex of Bacillus stearothermophilus.

Face up to challenge of virology world

Welcome to the World Journal of Virology (WJV), a new member of the World Journal Series. The World Journal Series was first launched as a peer-reviewed scientific journal covering aspects of research, diagnostics and clinical practice in biomedicine in 1995. WJV is an online and open-access peer-reviewed periodical focusing on virology. WJV covers a variety of topics in different areas of virology, including advances in basic research, updates in nomenclature, the development of novel diagnostic assays, the epidemiology of viral disorders and, new developments in the clinical management of viral diseases, including new vaccines and antiviral therapeutics. The purpose in launching the WJV is to promote knowledge exchange related to the classic human viruses as well as newly emerging viruses and their associated clinical disorders. Continually updating knowledge in a timely manner in this field where information related to the unceasing evolution of viruses is becoming available at a rapid pace is challenging. Thanks to the World-Wide-Web we are able to provide a podium for all authors and readers of WJV to address this challenge. I would like to acknowledge the Baishideng publisher, the members of the editorial board, and all contributing authors involved in this inaugural issue of the WJV. I sincerely hope all readers, i.e. future contributing authors, will like WJV and we look forward to your input in assisting WJV to grow and mature.

Serological diagnosis of Epstein-Barr virus infection: Problems and solutions

Serological tests for antibodies specific for Epstein-Barr virus (EBV) antigens are frequently used to define infection status and for the differential diagnosis of other pathogens responsible for mononucleosis syndrome. Using only three parameters [viral capsid antigen (VCA) IgG, VCA IgM and EBV nuclear antigen (EBNA)-1 IgG],it is normally possible to distinguish acute from past infection: the presence of VCA IgM and VCA IgG without EBNA-1 IgG indicates acute infection, whereas the presence of VCA IgG and EBNA-1 IgG without VCA IgM is typical of past infection. However, serological findings may sometimes be difficult to interpret as VCA IgG can be present without VCA IgM or EBNA-1 IgG in cases of acute or past infection, or all the three parameters may be detected simultaneously in the case of recent infection or during the course of reactivation. A profile of isolated EBNA-1 IgG may also create some doubts. In order to interpret these patterns correctly, it is necessary to determine IgG avidity, identify anti-EBV IgG and IgM antibodies by immunoblotting, and look for heterophile antibodies, anti-EA (D) antibodies or viral genome using molecular biology methods. These tests make it possible to define the status of the infection and solve any problems that may arise in routine laboratory practice.

Porcine reproductive and respiratory syndrome virus vaccines: Immunogenicity, efficacy and safety aspects

Porcine reproductive and respiratory syndrome virus (PRRSV) infection is the leading cause of economic casualty in swine industry worldwide. The virus can cause reproductive failure, respiratory disease, and growth retardation in the pigs. This review deals with current status of commercial PRRS vaccines presently used to control PRRS. The review focuses on the immunogenicity, protective efficacy and safety aspects of the vaccines. Commercial PRRS modified-live virus (MLV) vaccine elicits delayed humoral and cell-mediated immune responses following vaccination. The vaccine confers late but effective protection against genetically homologous PRRSV, and partial protection against genetically heterologous virus. The MLV vaccine is of concern for its safety as the vaccine virus can revert to virulence and cause diseases. PRRS killed virus (KV) vaccine, on the other hand, is safe but confers limited protection against either homologous or heterologous virus. The KV vaccine yet helps reduce disease severity when administered to the PRRSV-infected pigs. Although efforts have been made to improve the immunogenicity, efficacy and safety of PRRS vaccines, a better vaccine is still needed in order to protect against PRRSV.

Emerging and re-emerging viruses: A global challenge illustrated by Chikungunya virus outbreaks

In recent decades, the issue of emerging and re-emerging infectious diseases, especially those related to viruses, has become an increasingly important area of concern in public health. It is of significance to anticipate future epidemics by accumulating knowledge through appropriate research and by monitoring their emergence using indicators from different sources. The objective is to alert and respond effectively in order to reduce the adverse impact on the general populations. Most of the emerging pathogens in humans originate from known zoonosis. These pathogens have been engaged in long-standing and highly successful interactions with their hosts since their origins are exquisitely adapted to host parasitism. They developed strategies aimed at: (1) maximizing invasion rate; (2) selecting host traits that can reduce their impact on host life span and fertility; (3) ensuring timely replication and survival both within host and between hosts; and (4) facilitating reliable transmission to progeny. In this context, Arboviruses (or ARthropod-BOrne viruses), will represent with certainty a threat for the coming century. The unprecedented epidemic of Chikungunya virus which occurred between 2005 and 2006 in the French Reunion Island in the Indian Ocean, followed by several outbreaks in other parts of the world, such as India and Southern Europe, has attracted the attention of medical and state authorities about the risks linked to this re-emerging mosquito-borne virus. This is an excellent model to illustrate the issues we are facing today and to improve how to respond tomorrow.