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Vaccines, Hepatitis B and Insulin Production
Published in Debabrata Das, Soumya Pandit, Industrial Biotechnology, 2021
The infectious hepatitis B virus particles have two proteins: a core protein associated with the virus genome and a coat protein or S protein envelope. The core protein is not useful as a vaccine, but is used for diagnosing the disease (Powell and Newman, 2012). The HBV coat has the hepatitis B surface antigen (HbsAg), which is found in the form of aggregates in the blood of patients. The coat protein is not synthesized in large quantities in E. coli, but has been cloned in yeast using a vector based on a 2 µm circle. The 3.2kb HBV genome contains the HbsAg gene. Initial cloning is done in prokaryote (e.g. E. coli) using a shuttle vector which can replicate on both bacteria as well as yeast (eukaryotic cell). Yeast is used because it is easy to culture and grows rapidly. Yeast vectors are based on a plasmid called the two-micron plasmid (2 µm circle) which inhabits yeast cells (Robinson, 2016).
Nanosensors for Industrial Applications
Published in Vinod Kumar Khanna, Nanosensors, 2021
HbsAg is a protein covering the external surface of the hepatitis B virus. The chronoamperometric mode gold nanoparticle electroactive label (AuNP)-assisted magnetosandwich assay is used for its detection (Escosura-Muňiz et al. 2010). The scheme of the assay is shown in Figure 11.18 and its description is described below: Tosylactivated magnetic beads (MBs) are incubated with HbsAg, separated with a magnet, suspended in PBS-BSA blocking buffer, and washed with PBS-Tween, forming MB/HbsAg.The MB/HbsAg is incubated with human serum of post-infected patients forming the immunocomplex α-HbsAg IgG antibody/MB/HbsAg.The 20-nm AuNPs, synthesized by reducing trichloroauric acid with trisodium acetate, are conjugated with goat polyclonal antibodies anti-human IgG (α-HIgG) followed by blocking with BSA, to obtain the α-HIgG antibody/AuNP conjugate.α-HbsAg IgG antibody/MB/HbsAg is incubated with α-HIgG antibody/AuNP conjugate to form the complete magneto-immunosandwich: α-HbsAg IgG antibody/MB/HbsAg/α-HIgG antibody/AuNP conjugate.Making the magneto-immunosandwich for chronoamperometric sensor for detecting antibodies to hepatitis B surface antigen (Escosura-Muňiz et al. 2010).
Bloodborne Pathogens
Published in Barry Spurlock, Physical Hazards of the Workplace, 2017
The acute and chronic consequences of hepatitis B virus (HBV) infection are major health problems in the United States. An estimated 200,000–300,000 new infections occurred annually during the period 1980–1991. Approximately 8700 healthcare workers each year contract HBV, and about 200 will die as a result. Transmission of HBV is by direct injection through the skin (e.g., needlestick injuries in healthcare workers; the use of shared needles and syringes by intravenous drug users), blood contamination of mucous membranes (e.g., eyes, mouth, nose), exchange of sexual fluids during intercourse (e.g., semen and vaginal secretions), and transmission from an infected mother to her newborn infant. Infection with HBV may result in a variety of clinical symptoms from asymptomatic infection to a mild, flu-like illness to a very severe infection that may result in debilitating hepatitis, cirrhosis of the liver, or primary liver cancer. An individual who becomes infected with HBV may develop a chronic form of hepatitis from which they never completely recover. Currently, an estimated 1.25 million persons in the U.S. have chronic HBV infection. Persons infected with HBV are capable of transmitting this organism during any of the clinical states already mentioned. Once an individual is infected with HBV, the presence of certain “markers” can be determined (HBsAG, hepatitis B surface antigen; HBeAG, hepatitis B envelope antigen; HBsAb, hepatitis B surface antibody). HBsAG and HBeAG may give us information that an individual is still in the infectious stage of disease and capable of transmitting the hepatitis virus. HBsAb may show that the infected individual has produced antibodies against the hepatitis virus, which indicates recovery from infection. These antibodies are “protective antibodies” and prevent the individual from becoming ill if exposed to HBV again. These protective antibodies are what is produced in individuals who receive the hepatitis B vaccination series. The risk of death and impairment of health resulting from acute and chronic hepatitis B infection is significant. Therefore, knowledge of the disease and prevention against it are important. The best defense against HBV is to receive the hepatitis B vaccination series.
The roadmap towards cure of chronic hepatitis B virus infection
Published in Journal of the Royal Society of New Zealand, 2022
Nucleic acid polymers (NAPs) or S-antigen traffic-inhibiting oligonucleotide polymers (STOPs) are 40 nucleotide phosphorothioate oligoribonucleotides which are thought to target an unknown hydrophobic host protein, which indirectly inhibits subviral particle assembly and release. Rapid declines in serum levels of HBsAg levels are not accompanied by intracytoplasmic accumulation of HBsAg suggesting that this same mechanism also enhances intracellular degradation of HBsAg (Boulon et al. 2020). After 48 weeks treatment with both weekly intravenous REP-2139 and weekly subcutaneous pegylated IFN, 41% patients with active CHB achieved sustained off-treatment HBsAg loss (functional cure) and an additional 44% remained HBsAg positive but had sustained off-treatment suppression of HBV DNA and normalisation of ALT. Therefore 85% of all patients previously maintained on oral antiviral therapy were able to come off all treatment (Bazinet et al. 2020). These very encouraging preliminary results will need to be confirmed by the larger multicentre North American ACTIG collaborative study of REP-2139 plus pegylated IFN. Second-generation STOPs will be entering clinical development in early 2020.
Improving the recovery of clarification process of recombinant hepatitis B surface antigen in large-scale by optimizing adsorption-desorption parameters on Aerosil-380
Published in Preparative Biochemistry and Biotechnology, 2018
Seyed Nezamedin Hosseini, Parisa Ghaisari, Shahram Sharifnia, Maryam Khatami, Amin Javidanbardan
According to the World Health Organization (WHO) data, there are more than 350 million hepatitis B virus (HBV) carriers worldwide.[1,2] The hepatitis B surface antigen (HBsAg) is widely used for hepatitis B vaccine production. This antigen is a 22-nm spherical or filamentous particle with a molecular weight of 3500 kDa composed of 100 protein subunits, carbohydrates, and lipids.[3–7] Nowadays, HBsAg is produced commercially via recombinant technology using different yeasts such as Saccharomyces cerevisiae (S. cerevisiae) and Pichia pastoris (P. pastoris).[8,9] After expression of rHBsAg, in the downstream section, multiple separation units such as chromatographic columns are applied to isolate the antigens from other fragments of the hosts.[8–13]