Search results for "Infectivity"
showing 10 items of 103 documents
Recombinant Semliki Forest virus vectors encoding hepatitis B virus small surface and pre-S1 antigens induce broadly reactive neutralizing antibodies
2012
Most hepatitis B virus (HBV) vaccines consist of viral small surface (S) protein subtype adw2 expressed in yeast cells. In spite of good efficacy, HBV-genotype and subtype differences, escape mutants and insufficient Th1 activation remain potential problems. To address these problems, we generated recombinant Semliki Forest virus (rSFV) vectors encoding S protein, subtype adw2 or ayw2, or a fragment of the large surface protein, amino acids 1-48 of the pre-S1 domain, fused to S (pre-S1.1-48/S). The antigen loop in S protein and the selected pre-S1 sequences are known targets of neutralizing antibodies. BALB/c mice were immunized intravenously with 10(7) rSFV particles and 10(8) rSFV particl…
N-terminal myristoylation-dependent masking of neutralizing epitopes in the preS1 attachment site of hepatitis B virus
2011
The N-terminally myristoylated preS1 domain of the large hepatitis B surface protein (LHBs) mediates specific attachment of hepatitis B virus (HBV) to hepatocytes. Its B-cell epitopes leading to neutralization of infectivity are not yet characterized.We inserted C- and N-terminal preS1 peptides into the most immunogenic region of HBV core particles, therewith immunized Balb/c mice and determined binding properties and neutralization potential of resulting antibodies in vitro.The particles with preS1 inserts were highly immunogenic and the corresponding anti-preS antibodies strongly bound to HBV particles from chronic carriers infected with different HBV genotypes A-F. However, antibodies bi…
Toxic and enzymatic activities of Vibrio vulnificus biotype 2 with respect to host specificity
1996
In this work, the enzymatic activities of selected strains of biotypes 1 and 2 of Vabrio vulnificus were analyzed by using conventional methods and the API ZYM system. The toxic activities of extracellular products (ECPs) were further evaluated by in vitro and in vivo experiments. The ECPs of both biotypes (i) showed high-level hydrolytic activities, (ii) displayed cytotoxicity for fish cell lines, and (iii) were lethal for eels. Exotoxins seem to be proteinaceous since heat treatment of ECP samples destroyed their toxicity. Only biotype 2 strains were virulent for cels, suggesting that host specificity must be related to differences in cell surface properties. Infectivity trials with other…
Green tea extract assisted low-temperature pasteurization to inactivate enteric viruses in juices.
2020
The current popularity of minimally processed foods is an opportunity for natural antimicrobial agents to be combined with mild heat treatments to act synergistically in reducing viral foodborne pathogens. Viral inactivation by heat-treatments (at 25, 40, 50 and 63 °C for 30 min) combined with aged green tea extract (aged-GTE) was initially evaluated in phosphate buffered saline (PBS) against murine norovirus (MNV-1) and hepatitis A virus (HAV) by cell culture, and against human norovirus by in situ capture RT-qPCR. The combination of aged-GTE and heat treatment at 50 °C for 30 min exerted strong antiviral activity, reducing by more than 5 log MNV-1 infectivity in PBS. Heating at 40 °C for …
In Vivo Replication of Recombinant Murine Cytomegalovirus Driven by the Paralogous Major Immediate-Early Promoter-Enhancer of Human Cytomegalovirus
1999
ABSTRACT Transcription of the major immediate-early (MIE) genes of cytomegaloviruses (CMV) is driven by a strong promoter-enhancer (MIEPE) complex. Transactivator proteins encoded by these MIE genes are essential for productive infection. Accordingly, the MIEPE is a crucial control point, and its regulation by activators and repressors is pertinent to virus replication. Since the MIEPE contains multiple regulatory elements, it was reasonable to assume that specific sequence motifs are irreplaceable for specifying the cell-type tropism and replication pattern. Recent work on murine CMV infectivity (A. Angulo, M. Messerle, U. H. Koszinowski, and P. Ghazal, J. Virol. 72:8502–8509, 1998) has do…
Domestic pig prioritized in one health action against fascioliasis in human endemic areas: Experimental assessment of transmission capacity and epide…
2021
The Northern Bolivian Altiplano is the human fascioliasis hyperendemic area where the highest prevalences and intensities in humans have been reported. Preventive chemotherapy was implemented in the last ten years. Surveillance showed high human infection and re-infection rates in between the annual triclabendazole monodose treatments. A complementary One Health control action was launched to decrease the infection risk. Among the multidisciplinary axes, there is the need to establish animal reservoir species priorities for a more efficient control. Laboratory and field studies were performed for the first time to assess the Fasciola hepatica transmission capacity of the pig and its potenti…
Discrimination of non-infectious SARS-CoV-2 particles from fomites by viability RT-qPCR.
2021
The ongoing coronavirus 2019 (COVID-19) pandemic constitutes a concerning global threat to public health and economy. In the midst of this pandemic scenario, the role of environment-to-human COVID-19 spread is still a matter of debate because mixed results have been reported concerning SARS-CoV-2 stability on high-touch surfaces in real-life scenarios. Up to now, no alternative and accessible procedures for cell culture have been applied to evaluate SARS-CoV-2 infectivity on fomites. Several strategies based on viral capsid integrity have latterly been developed using viability markers to selectively remove false-positive qPCR signals resulting from free nucleic acids and damaged viruses. T…
Structural analysis of Cryptosporidium parvum.
2004
Cryptosporidium parvum(Apicomplexa, formerly Sporozoa) is the causative agent of cryptosporidiosis, an enteric disease of substantial medical and veterinary importance.C. parvumshows a number of unique features that differ from the rest of the class of coccidea in which it is currently grouped taxonomically. Differences occur in the overall structure of the transmission form and the invasive stages of the parasite, its intracellular location, the presence of recently described additional extracellular stages, the host range and target cell tropism, the ability to autoinfection, the nonresponsiveness to anticoccidial drugs, the immune response of the host, and immunochemical and genetic char…
Morphology and in vitro infectivity of sporozoites of Cryptosporidium parvum.
2009
An important obstacle in studying Cryptosporidium parvum is the lack of a permanent in vitro cultivation system of the parasite. While short-term cultures using various host cell lines have been widely employed, long-term cultures that would facilitate the immortalization of C. parvum isolates have not yet been developed. The description of the complete development of C. parvum in cell-free culture in 2004 has been received with great interest and also with some astonishment. Unfortunately, attempts to reproduce these results with different isolates of C. parvum and also C. hominis have failed. In this report, we provide an alternative interpretation of the nature of a parasite stage that o…
Survival and infectivity of Hypoderaeum conoideum and Euparyphium albuferensis cercariae under laboratory conditions.
1999
The survival characteristics of the cercariae of Hypoderaeumconoideum and Euparyphiumalbuferensis (Trematoda: Echinostomatidae) at 20°C and 30°C are described, and the age dependency of their infectivity at 20°C is studied to determine their respective transmission efficiencies. Cercarial survival was found to be age-dependent and was higher at 20°C. For both cercariae, the maximum life-span was 26 h at 20°C and 16 h at 30°C, and their respective times to 50% mortality were similar at each temperature. Both cercariae seem to be well adapted to transmission in their natural habitat, though cercarial infectivity of H. conoideum was higher than that of E. albuferensis, this being correlated wi…