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Table of Contents for this page:

  • Current Issue
  • Current Issue of Virology Journal

    Virology Journal - Latest Articles

  • Long-term persistence of Chikungunya virus neutralizing antibodies in human populations of North Eastern Thailand

  • Background: Chikungunya virus (CHIKV) outbreak recurrences in Thailand are unpredictable and separated by unexplained and often long silent epidemiological periods that can last for several years. These silent periods could be explained in part by the fact that infection with one CHIKV strain confers lasting natural immunity, even against other CHIKV strains. In this study we evaluated the persistence of CHIKV-specific neutralizing antibodies in the population of Chumpae District, Khon Kaen Province, nineteen years after a CHIKV outbreak occurred in the same area in 1991.FindingsOverall 39% (44/111) of 111 former patients had neutralizing antibodies reacting against CHIKV ECSA strain. Consistently high titers of neutralizing antibodies were found in 75% (33/44) of all positively-reacting sera, 70% of which (23/33) were collected from individuals amongst the ggt;60 years old age group. Although the prevalence found in Pong Haeng village (70%) was significantly higher than the prevalence detected in the Nong Thum village (14%), control study villages without known previous Chikungunya epidemics had a high Chikungunya neutralizing antibody prevalence (65%). Conclusions: More than one-third of the pre-exposed population had persisting natural immunity that was more likely boosted by recent and repetitive exposure to the emerging ECSA CHIKV in Thailand. Also, Chikungunya virus appears to largely circulate in the country with a great variability appears between villages or area probably associated with the vector abundance and efficiency. Altogether these results show a potential for a lifelong immunity against CHIKV. Given the rapid spread of the highly pathogenic ECSA strain in Southern Thailand, the development of CHIK vaccine is strongly recommended.

  • Epidemiology of human parechovirus, Aichi virus and salivirus in fecal samples from hospitalized children with gastroenteritis in Hong Kong

  • Background: Emerging human picornaviruses, including human parechovirus (HPeV), Aichi virus (AiV) and salivirus (SalV) were found to be associated with gastroenteritis, but their roles in enteric infections are not fully understood. In addition, no report on the circulation of these viruses in Hong Kong is available. The objective of this study was to investigate the prevalence and genetic diversity of HPeV, AiV and SalV in fecal samples from hospitalized children with gastroenteritis in Hong Kong. Methods: Fecal samples from hospitalized children with gastroenteritis were subject to detection of HPeV, AiV and SalV by RT-PCR using consensus primers targeted to their 5′UTRs. Positive samples were subject to capsid and/or 3CD region analysis for genotype determination. The epidemiology of HPeV, AiV and SalV infections was analyzed. Results: Among 1,708 fecal samples subjected to RT-PCR using primers targeted to 5′UTR of HPeV, AiV and SalV, viruses were detected in 55 samples, with 50 positive for HPeV only, 3 positive for AiV only, 1 positive for both HPeV and AiV, and 1 positive for both HPeV and SalV. Phylogenetic analysis of the partial VP1 gene of the 33 HPeV strains revealed the presence of genotypes of HPeV- 1, 3, 4, 5, 7, 10, among which HPeV-1 was the predominant genotype circulating in our population. The peak activity of HPeV infection was in fall. Of the 3 children with AiV infection, the 3 AiV strains were found to belong to genotype A based on the phylogenetic analysis of their partial VP1 and 3CD regions. The genotype of a SalV strain detected in this study could not be determined. Co-detection of different pathogens was observed in 24 samples (43.6%) of 55 fecal samples positive for HPeV, AiV and SalV. Conclusions: HPeV, AiV and SalV were detected in fecal samples of hospitalized children with gastroenteritis in Hong Kong, with the former having the highest prevalence. HPeV-1 was the predominant genotype among HPeVs, while genotype A was the predominant genotype among AiVs in this study.

  • Frequent migration of introduced cucurbit-infecting begomoviruses among Middle Eastern countries

  • Background: In the early 2000s, two cucurbit-infecting begomoviruses were introduced into the eastern Mediterranean basin: the Old World Squash leaf curl virus (SLCV) and the New World Watermelon chlorotic stunt virus (WmCSV). These viruses have been emerging in parallel over the last decade in Egypt, Israel, Jordan, Lebanon and Palestine. Methods: We explored this unique situation by assessing the diversity and biogeography of the DNA-A component of SLCV and WmCSV in these five countries. Results: There was fairly low sequence variation in both begomovirus species (SLCVπ = 0.0077; WmCSVπ = 0.0066). Both viruses may have been introduced only once into the eastern Mediterranean basin, but once established, these viruses readily moved across country boundaries. SLCV has been introduced at least twice into each of all five countries based on the absence of monophyletic clades. Similarly, WmCSV has been introduced multiple times into Jordan, Israel and Palestine. Conclusions: We predict that uncontrolled movement of whiteflies among countries in this region will continue to cause SLCV and WmCSV migration, preventing strong genetic differentiation of these viruses among these countries.

  • CHD1 and CHD2 are positive regulators of HIV-1 gene expression

  • Background: Retroviruses encode a very limited number of proteins and therefore must exploit a wide variety of host proteins for completion of their lifecycle. Methods: We performed an insertional mutagenesis screen to identify novel cellular regulators of retroviral replication. Results: This approach identified the ATP-dependent chromatin remodeler, chromodomain helicase DNA-binding protein 2 (CHD2), as well as the highly related CHD1 protein, as positive regulators of both MLV and HIV-1 replication in rodent and human cells. RNAi knockdown of either CHD2 or the related CHD1 protein, in human cells resulted in a block to infection by HIV-1, specifically at the level of transcription. Conclusions: These results demonstrate that CHD1 and CHD2 can act as positive regulators of HIV-1 gene expression.

  • Avian paramyoxvirus-8 immunization reduces viral shedding after homologous APMV-8 challenge but fails to protect against Newcastle disease

  • Background: Protection against infection by Newcastle disease virus (NDV), also designated as avian paramyxovirus subtype-1 (APMV-1), is mediated by immune responses to the two surface glycoproteins, hemagglutinin-neuraminidase (HN) and fusion (F) protein. Thus, a chimeric APMV-1 based vaccine that encodes APMV-8 HN- and F-proteins and expresses the hemagglutinin of avian influenza virus (AIV) H5N1, is able to protect against HPAIV H5N1 but fails to protect against NDV [PLoS One 8:e72530, 2013]. However, it is unclear whether avirulent APMV-subtypes, like APMV-8 can induce subtype-specific immunity and protect from a homologous challenge.FindingsAPMV-8 infections of 3- and 6-weeks-old specific pathogen free (SPF)-chickens did not induce any clinical signs but was associated with virus shedding for up to 6 days. Viral replication was only detected in oropharyngeal- and never in cloacal swabs. Upon reinfection with homologous APMV-8, viral shedding was restricted to day 2 and in contrast to naive SPF-chickens, only RNA but no infectious virus was recovered. No protection was induced against virulent NDV challenge, although morbidity and mortality was delayed in APMV-8 primed chickens. This lack of protection is in line with a lack of reactivity of APMV-8 specific sera to APMV-1 HN-protein: Neither by hemagglutin-inhibition (HI) test nor immunoblot analyses, cross-reactivity was detected, despite reactivity to internal proteins. Conclusions: Immune responses mounted during asymptomatic APMV-8 infection limit secondary infection against homologues reinfection and facilitates a delay in the onset of disease in a subtype independent manner but is unable to protect against Newcastle disease, a heterologous APMV-subtype.

  • Pathogenicity and tissue distribution of grass carp reovirus after intraperitoneal administration

  • Grass carp reovirus (GCRV) is the causative agent of grass carp hemorrhage and causes significant loss of fingerlings. However, little is known about how the virus is distributed in organs and tissues. The aim of the present study was to investigate the distribution of different GCRV stains in tissues and organs of grass carp. The pathogenicity and tissue distribution of GCRV were monitored after intraperitoneal administration. The study showed a distribution of GCRV in different tissues and organs, particularly in the liver, spleen, kidney, intestine, and muscle, which had a higher number of viral RNA copies during the sixth to ninth days. The kidney had the highest numbers of viral RNA copies, as high as 24000 copies. Until the fourteenth day, nearly no viral RNA copies could be detected. This study defined the virus distribution in different tissues of grass carp inoculated by i.p. and supplied clues for the pathogenesis of GCRV.

  • Identification of an env-defective HIV-1 mutant capable of spontaneous reversion to a wild-type phenotype in certain T-cell lines

  • Background: Attempts to eradicate HIV from cellular reservoirs are vital but depend on a clear understanding of how viral variants are transmitted and survive in the different cell types that constitute such reservoirs. Mutations in the env gene of HIV may be able to exert a differential influence on viral transmission ability in regard to cell-free and cell-associated viral forms. Methods: The ability of HIV containing an env G367R mutation in cell-free and cell-associated viruses to cause infection and to revert to wild-type was measured using several T cell lines. To determine factors that might potentially influence the reversion of G367R, we studied each of entry inhibitors, inhibitors of cellular endocytosis, and modulators of cell growth and activation. Results: We demonstrate that an HIV-1 variant containing a G367R substitution within the CD4 binding site of gp120 was non-infectious as free virus in culture but was infectious when infected cells were co-cultured with certain T cell lines or when cells were transfected by a relevant proviral plasmid. Differences in viral infectivity by cell-associated G367R viruses were determined by the type of target cell employed, regardless which type of donor cell was used. Reversion was slowed or inhibited by entry inhibitors and by inhibitors of cellular endocytosis. Interleukin 2 was able to block G367R reversion in only one of the T cell lines studied but not in the other, while phorbol 12-myristate 13-acetate (PMA) inhibited G367R reversion in all the T cell lines. Conclusions: Env-defective HIV may have a different phenotype as cell-free versus cell-associated virus. The persistence of defective forms can potentially lead to the emergence of virulent forms. The heterogeneity of cell types that constitute the HIV reservoir can contribute to viral variability, even among similar types of cells. This is the first demonstration of a mutation in the HIV envelope, i.e. G367R, that can compromise infection by cell-free virus but less severely by cell-associated virus and that does so in a cell type-dependent manner.

  • Sequencing and molecular characterization of CTNCEC25, a China fixed rabies virus vaccine strain CTN-1 adapted to primary chicken embryo cells

  • Background: Rabies virus is the main etiologic agent of the widespread neurological disease rabies. Recently, the China rabies virus vaccine strain CTN-1 adapted to chicken embryo cells, which has been designated as CTNCEC25, was obtained and demonstrated to have high immunogenicity. However, the full genome sequence of CTNCEC25 and its phylogenetic relationship with other rabies virus street and vaccine strains have not been characterized. Results: The complete genome of CTNCEC25 was sequenced and analyzed. The length of CTNCEC25 genome is 11,924 nucleotides (nt), comprising a 3′ leader sequence of 59 nt, nucleoprotein (N) gene of 1,425 nt, phosphoprotein (P) gene of 989 nt, matrix protein (M) gene of 803 nt, glycoprotein (G) gene of 2,067 nt, RNA-dependent RNA polymerase gene (L) of 6,474 nt and a 5′ trailer region of 71 nt. A comparison of the entire genomes of CTN-1 and CTNCEC25 identified 16 nt substitutions and 1 deletion, resulting in 8 amino acid (aa) changes in the five structural proteins with one in L (aa 1602), two in M (aa 99 and 191) and six in mature G (aa 147, 333, 389, 421 and 485). The percentage homology of the CTNCEC25 genomic sequence with other fully sequenced rabies virus strains ranged from 81.4% to 99.9%. Phylogenetic analysis indicated that CTNCEC25 was more closely related with those recently isolated China street strains than other vaccine strains. Virus growth analysis showed that CTNCEC25 achieved high rate of propagation in cultured cells. Conclusions: In this study, the complete genome of CTNCEC25 was sequenced and characterized. Our results showed that CTNCEC25 was more closely related to wild street strains circulating in China than other vaccine strains. Sequence analysis showed that the G protein ectodomain amino acid sequence identity between CTNCEC25 and other rabies virus strains was at least 90% identical. Furthermore, CTNCEC25 achieved high virus titers in cultured cells. Given that CTNCEC25 has high immunogenicity and induced strong protective immune response in animals, these results collectively demonstrated that CTNCEC25 is an ideal vaccine strain candidate for producing human vaccine with high quality and safety in China.

  • Development of kinomic analyses to identify dysregulated signaling pathways in cells expressing cytoplasmic PrP

  • Background: Dysregulated protein kinase signaling is involved in the pathogenesis of many chronic diseases. However, the dysregulated signaling pathways critical to prion pathogenesis remain incompletely characterized. Global analyses of signaling pathways may be useful to better characterize these pathways. We therefore set out to develop such global assays. To this end, we used as a model cytoplasmic mutants of the cellular prion protein (PrPC), which are toxic to N2a neuroblastoma cells. We tested the global assays for their sensitivity to detect changes in signaling pathways in cells expressing cytoplasmic PrP mutants. Methods: We developed a targeted proteomics (kinomics) approach using multiplex Western blots to identify signaling pathways dysregulated in chronic neurological pathologies. We tested the approach for its potential ability to detect signaling changes in N2a cells expressing cytoplasmic PrP mutants. Results: Multiplex Western blots were designed to quantitate the expression levels of 137 protein kinases in a single membrane and using only 1.2 mg of sample. The response of the blots was sensitive and linear to changes of 6% in protein levels. Hierarchical and functional clustering of the relative expression levels identified an mTOR signaling pathway as potentially dysregulated in N2a cells expressing cytoplasmic PrP. The mTOR signaling pathway regulates global protein synthesis, which is inhibited in cells expressing cytoplasmic PrP. The levels of proteins involved in the Akt1/p70S6K branch of mTOR signaling changed in synchrony with time of cytoplasmic PrP expression. Three kinases in this pathway, Akt, p70S6K, and eIF4B were in their inactive states, as evaluated by phosphorylation of their regulatory sites. Conclusion: The results presented are consistent with the previously reported inhibition of Akt/p70S6K/eIF4B signaling as mediating pathogenesis of cytoplasmic PrP. We conclude that the kinomic analyses are sensitive and specific to detect signaling pathways dysregulated in a simple in vitro model of PrP pathogenesis.

  • Antibodies reacting with JCPyV_VP2 _167-15mer as a novel serological marker for JC polyomavirus infection

  • Background: JC polyomavirus (JCPyV) is a widespread human polyomavirus that usually resides latently in its host, but can be reactivated under immune-compromised conditions potentially causing Progressive Multifocal Leukoencephalopathy (PML). Detection of antibodies against the major capsid protein VP1 currently is the main marker for assessment of infection with JCPyV. Methods: Based on a peptide microarray, peptide JCPyV_VP2_167-15mer was selected and a peptide ELISA was developed for detection of antibodies directed against this peptide. Epitope mapping and computational modelling was performed to further characterize this peptide. In a cohort of 204 healthy subjects it was investigated whether antibodies against JCPyV_VP2_167-15mer were correlated with VP1 serology or urinary viral load. Results: Epitope mapping of peptide JCPyV_VP2_167-15mer showed that the minimal epitope consisted of L173PALTSQEI181 with amino acids P174, L176 and E180 being essential for antibody recognition. Computational analysis was used to predict that this epitope is located at an exposed domain of the VP2 capsid protein, readily accessible for immune recognition upon infection. No correlation could be observed with JCPyV VP1 antibody levels, or urinary viral load. Conclusion: This work indicates that specific antibodies against JCPyV_VP2_167-15mer might be considered as a novel serological marker for infection with JCPyV.
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