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Detection of neutralizing antibody to viral neuraminidase (NA) by testing for enzyme inhibition has been recognized as an important part of the immunogenicity of influenza vaccines. However, the absence of a well characterized standard source of active NA and validated assays has significantly limited clinical studies of NA immunity. Influenza virus-like particles (VLPs) containing hemagglutinin (HA), NA, and M1 proteins were produced from insect cells infected with a recombinant baculovirus and used as the NA source for the NA inhibition (NAI) assay. The NA activity of 6 different VLP strains varied from 0.43 to 1.61 (×10(-3)) enzyme units per μg of HA and was stable over 6 months of storage at 2-8°C. The NAI assay using 2'-(4-methylumbelliferyl)-α-d-N-acetylneuraminic acid as a substrate was modified for testing the antibody titer in clinical samples and validated. The advantages of the assay include: (1) stable, reproducible, and standardized source of NA; (2) testing the antibody titer specific to each subtype of NA in serum from subjects immunized with trivalent vaccines (H1N1, H3N2, B) with no interference from antibodies specific to the HA and to heterologous subtypes of the NA; (3) suitability for conducting long-term clinical trials as a result of low intra- and inter-assay variability, and (4) a wide analytical range due to 25% inhibition cut-off value for the NAI titer estimation.
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http://dx.doi.org/10.1016/j.jviromet.2011.03.011 | DOI Listing |
Virology
August 2025
Changchun Institute of Biological Products Co.,Ltd, Changchun, China; State Key Laboratory of Novel Vaccines for Emerging Infectious Diseases, China National Biotec Group Company Limited, Beijing, China. Electronic address:
Avian influenza virus infections pose a potential pandemic threat. The currently licensed vaccines have inherent limitations, emphasizing the urgent need for improved influenza vaccines. Here, we developed a novel hemagglutinin (HA) virus-like particle (VLP) vaccine candidate through the baculovirus expression vector system (BEVS).
View Article and Find Full Text PDFVirology
September 2025
Center for Inflammation, Immunity and Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, USA. Electronic address:
To better understand the contribution of interferon-γ (IFN-γ) receptor signaling to vaccine-induced immunity, we employed A129 (IFN-α/β receptor-deficient) and AG129 (IFN-α/β/γ receptor-deficient) mouse models. AG129 mice induced comparable levels of virus-specific IgG after vaccination with influenza virus H5 hemagglutinin (HA) virus-like particles (VLPs). Vaccinated AG129 mice with HA VLPs exhibited impaired Th1-immune responses, lower hemagglutination inhibition (HAI) titers, increased susceptibility to virus infection, and lower survival rates following influenza virus (H5N1) challenge than vaccinated A129 mice.
View Article and Find Full Text PDFVirus Res
August 2025
Key Laboratory for prevention and control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, Key Laboratory of Livestock Disease Prevention of Guangdong Province, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, Ch
The emergence of SARS-CoV-2 has posed a substantial global public - health threat and has led to the emergence of diverse variant strains. A prevalent mutation, D614G, is commonly detected in the spike glycoprotein (S) of successive SARS- CoV-2 variants, which enhances viral infectivity. Here, the objective was to examine the influence of mutations on the synthesis and processing of the S protein, virus assembly, and infectivity.
View Article and Find Full Text PDFFront Microbiol
July 2025
Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, China.
Pigeon circovirus (PiCV) infection, which causes young pigeon disease syndrome (YPDS) and immunosuppression, significantly impacts both the meat and racing pigeon industries. Currently, no inactivated vaccine exists for PiCV prevention, primarily due to the challenges associated with isolating the PiCV virion, except for some gene subunit vaccines express the Cap protein of PiCV. The development of detection techniques is crucial for the diagnosis of PiCV.
View Article and Find Full Text PDFNanomedicine (Lond)
September 2025
Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, Core Research Institute (CRI), Kyung Hee University, Seoul, Republic of Korea.
Aim: dense granule antigen 7 (GRA7) is a membrane-associated protein expressed across parasite life cycle and represents a promising vaccine target. This study aimed to develop a GRA7-based virus-like particle (VLP) vaccine and assess its protective efficacy.
Materials & Methods: GRA7 VLPs were constructed using an influenza M1 scaffold via the baculovirus expression system.