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An Introduction to the Immune System and Vaccines
Published in Patricia G. Melloy, Viruses and Society, 2023
The term “antigenic drift” is used to describe changes in the shape of these key antigen proteins of the virus as the strain evolves, and “antigenic shift” refers specifically to changes in these antigens through the combination of new nucleic acid segments, such as what occurs with the influenza virus (Minkoff and Baker 2004b). One could say these changes to viral surface antigens are analogous to a wanted criminal putting on a new disguise to avoid capture by the police. In a similar analogy, Professor Sunetra Gupta described a pathogen as slightly changing its wardrobe over time to avoid detection, in a series of cartoons presented as a part of her Royal Society lecture in 2009 (Society 2009). Finally, insidiously, some viruses like Epstein-Barr virus and herpes simplex virus can affect the function of immune cells and their proteins, cutting the immune system off at its knees (Coico and Sunshine 2015).
Chest
Published in Henry J. Woodford, Essential Geriatrics, 2022
It has been identified in three types, called A, B and C, but only A and B are clinically important. They exist in numerous subtypes due to variations in haemagglutinin (H) and neuraminidase (N) proteins. The three subtypes that commonly affect humans are H1N1, H2N2 and H3N2. Seasonal variation in virus strains also occurs. ‘Antigenic drift' causes a minor change that results in annual epidemics because the virus is able to avoid memory T cells and circulating antibodies. ‘Antigenic shift' occurs following a major change of the virus (i.e. recombination of RNA), which can lead to pandemics. The virus rarely spreads beyond the respiratory tract. Bacterial infection typically occurs at five to seven days following initial symptoms. Viral culture takes three to five days. More rapid serological tests have been developed for diagnosis. Barrier nursing can reduce the spread of infection around hospitals or care homes.
Routine maternal immunizations for all pregnant women
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
While antigenic drift describes minor genetic changes in the viral genome, “antigenic shift” refers to major genetic alteration. The major pandemic strain in 1917 to 1918 was caused by an H1N1 subtype influenza A virus and this presented until 1957 when the H2N2 subtype appeared. The H2N2 subtype underwent a major antigen shift in 1968 resulting in the H3N2, which has been circulating until the present time. An H1N1 subtype emerged in 1977 and has been co-circulating with the H3N2 subtype. Current influenza vaccine contains one H3N2 strain, one H1N1 strain, and one influenza B strain. In March 2009, a novel H1N1 subtype emerged in Mexico and is the result of influenza A strains from pigs, birds, and humans. Recombinant analysis showed triple-reassessment swine H1N1 influenza virus coming from classic swine, North American lineage; avian, North American lineage; human (seasonal) H3N2 and human seasonal (H1N1) strain initiated a worldwide pandemic (7).
Clinical development of variant-adapted BNT162b2 COVID-19 vaccines: the early Omicron era
Published in Expert Review of Vaccines, 2023
Shanti Pather, Alexander Muik, Ruben Rizzi, Federico Mensa
However, in studies in the United Kingdom, reduction in the risk of hospitalization and death from COVID-19 in those who received a fifth dose booster of bivalent Original/Omicron BA.1 vaccine was similar to that observed with previous original vaccine boosters [91,92]. This is likely due to differences in circulating lineages by the time this vaccine was rolled out. In addition, waning effectiveness of the bivalent Original/Omicron BA.4–5 vaccines has been observed from 2–4 months post-booster [93], likely due to the antigenic difference between the vaccine and circulating sub-lineages. This highlights the limitations of variant-adapted vaccines. Antigenic drift will inevitably lead to further changes in the genome of SARS-CoV-2 over time, which may eventually result in a mismatch between the vaccine and the circulating virus. Antigenic drift and shift also have the potential to grant additional immuno-evasive properties. As emerging variants that are more antigenically distant from the variant-adapted vaccine displace previously circulating viruses, further variant-adapted vaccines will be needed. Consequently, in May 2023, the WHO TAG-CO-VAC recommended an update to COVID-19 vaccines based on an XBB.1 descendent sub-lineage, such as XBB.1.5 or XBB.1.16, in order to better match the vaccines to the current dominant circulating variant. A monovalent formulation was recommended, as variants that are antigenically related to the wild-type virus are no longer in circulation [76]. Ongoing updates to COVID-19 vaccines are expected as SARS-CoV-2 continues to evolve.
Approaches in broadening the neutralizing antibody response of the influenza vaccine
Published in Expert Review of Vaccines, 2021
Ruiqi Zhang, Ivan Fan-Ngai Hung
Influenza vaccine can elicit immune response, especially neutralizing antibody, against influenza virus as virus infection, and is the most effective way to prevent influenza virus infection [19]. However, as RNA virus, influenza virus keeps constantly antigenic evolution, resulting in the antigenic drift and shift. The antigenic changes help the virus escape from the preexisting neutralizing antibodies, and then weaken the vaccine effectiveness [20]. For instance, in the 2014–2015 influenza season, the emergence of an H3N2 drifted virus resulted in low vaccine effectiveness of 11% [21]. During the 2018–2019 season, as an H3N2 with antigenic drift circulated, the vaccine was only 9% effective for this virus [22]. To overcome the threat of antigenic changes, we should broaden the heterologous cross-neutralizing antibody induced by influenza vaccine. In this article, we first review currently various types of influenza vaccines. Then, we discuss how to broaden the neutralizing antibody response of the vaccine.
Influenza vaccine: progress in a vaccine that elicits a broad immune response
Published in Expert Review of Vaccines, 2021
Irina Isakova-Sivak, Ekaterina Stepanova, Daria Mezhenskaya, Victoria Matyushenko, Polina Prokopenko, Ivan Sychev, Pei-Fong Wong, Larisa Rudenko
Influenza viruses are highly contagious respiratory pathogens that pose a constant threat to global public health. Annual influenza epidemics cause 3 to 5 million cases of severe respiratory diseases, up to 650,000 of which are fatal [1]. Despite the reduction in influenza activity in the 2020–2021 season because of the measures taken to combat the new coronavirus disease, COVID-19 [2], influenza viruses continue to circulate in human and animal reservoirs with the potential to cause severe epidemics. Annual influenza vaccination is recommended for the entire human population to reduce the disease burden and delay virus transmission. Traditional influenza vaccines predominantly induce neutralizing antibodies against the surface antigens of the virus, mainly to their immunodominant hypervariable regions. Constant antigenic drift allows the virus to escape from the action of these antibodies, reducing vaccination effectiveness and requiring an almost annual update in the composition of seasonal influenza vaccines [3–5]. Many different approaches have been developed to improve the immunogenic and protective properties of the existing influenza vaccines, with the ultimate goal of creating a universal influenza vaccine that can elicit prolonged and broadly reactive immune responses with the potential to protect people of all ages from any circulating and emerging influenza viruses. In this review, we have summarized the state-of-the-art development of cross-protective influenza vaccines and discussed the main challenges in evaluating them in preclinical and clinical trials.