Issue link: https://wardsworld.wardsci.com/i/1330441
Vaccination (continued) Attenuated-live vaccines Because attenuated-live-virus vaccines reproduce in the recipient, they provoke both a broader and more intense range of antibodies and T-lymphocyte-associated immune responses than noninfectious vaccines. Live-virus vaccines have been administered subdermally (vac- cinia), subcutaneously (measles), intramuscularly (pseudorabies virus), intranasally (infectious bovine rhinotracheitis), and orally (trivalent Sabin poliovirus). Combinations of vaccines have also been used. When combined live measles, rubella, and mumps vaccines have been given by injection, the antibody response to each component has been com- parable with the antibody response to the individual vaccines given separately. Many organisms produce their pathophysiologic effects through acute infections localized to the gastrointestinal, pulmonary, nasopha- ryngeal, and genitourinary surfaces. These areas are bathed in mucus that contains highly important secretory immunoglobulin A (IgA). Sub- cutaneous, intravenous, and intramuscular immunization regimens, al- though effective in inducing IgG-type antibodies, are almost universal- ly ineffective at the induction of secretory IgA antibodies. In contrast, oral administration is a feasible alternative to stimulate the common mucosal immune system, as with the live-attenuated polio vaccine. Live-virus vaccines administered through a natural route of infection often induce local immunity, which is a decided advantage. However, in the past, attenuated-live virus vaccines have been associated with several problems, including reversion to virulence, natural spread to contacts, contaminating viruses, lability, and viral interference. Noninfectious vaccines Noninfectious vaccines include inactivated killed vaccines, subunit vaccines, synthetic peptide and biosynthetic polypeptide vaccines, oral transgenic plant vaccines, anti-idiotype antibody vaccines, DNA vaccines, and polysaccharide-protein conjugate vaccines. With most noninfectious vaccines, a suitable formulation is essential to provide the optimal antigen delivery for maximal stimulation of protective im- mune responses. Development of new adjuvant and vector systems is pivotal to produce practical molecular vaccines. Killed vaccines The inactivated forms of the toxins produced by the tetanus and diphtheria bacteria, called toxoids, were among the first vaccines developed. For human use, toxoid vaccines must be highly purified to remove extraneous materials. Killed-virus vaccines consist of partially purified virus particles whose infectivity has been destroyed by treat- ment with chemicals or with radiation. These virus particles retain the ability to elicit an immune response and to protect from clinical disease. Although generally safer and more stable than attenuated- live-virus vaccines, killed-virus vaccines require multiple doses of high concentrations of antigen sometimes administered with adjuvant, that + ward ' s science Fig. 2: The flu (influenza) gene reassortment process that researchers employ to create a proper flu vaccine. The reassortment combines the desired genes coding for hemagglutinin (HA) and neuraminidase (NA) antigens from the target strain (flu strain 1) with genes from a harmless strain that grows well in an egg (flu strain 2). The best combinations (typically three in number) comprising new reassortment flu strains are used in the production of the flu vaccines for a particular year. (Credit: Link Studio for the National Institute of Allergy and Infectious Diseases)