Chapter category: Viruses
Approaches to Viral Vaccine Development Involving Chemokine Receptors and Their Ligands, with Special Reference to Human Immunodeficiency Virus 1
Chapter authors:
Gordon Ada
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There are currently registered vaccines against 22 infectious agents pathogenic for humans and candidate vaccine preparations against 18 other infectious agents have undergone phase II clinical trials.1 Some of these later preparations may become licensed for medical use within the next five years. The form of current viral or bacterial vaccines vary greatly, being either live, attenuated whole agent, inactivated whole agent, subunit preparations consisting usually of one or more surface antigens, bacterial toxoids, and polysaccharide preparations or more usually now, polysaccharide/protein conjugates. Most of these vaccines are against agents which show very little antigenic variation and mainly cause acute infections, i.e., a sublethal dose of the agent is cleared within a few weeks by the host's immune system.
There is now very well documented evidence that many of these vaccines, especially some of the childhood vaccines, are highly effective. Data from the Centers for Disease Control and Prevention in Atlanta show that, compared to the number of notified cases of disease during an epidemic prior to the availability of the specific vaccine, the number of cases in recent years (some years after the vaccine became available) has dropped by more than 99%.1 Recently, the effect of a newly available vaccine on the reduction of cases of disease can be dramatic. The administration in 1999 of a new N. meningiditis type C vaccine in the UK reduced the incidence of disease by 9295% in two different aged groups within one year.2 These facts, together with the earlier global eradication of smallpox by vaccination, have encouraged the hope that it may be possible to control by vaccination at least some of the remaining infectious human pathogens.
There are still many infectious agents—viruses, bacteria and multicellular parasites which are major causes of morbidity and mortality in the world.3 Many of these agents show considerable antigenic diversity which allows them to by-pass antibody responses following earlier infections or vaccinations. In one way or another, they can also evade or subvert cellmediated immune responses so that the infection persists. For many years, diseases caused by agents such as malaria, tuberculosis and different viruses (including rotaviruses, hepatitis C and respiratory syncytial viruses) vied for the position as the world's leading cause of sickness and death. But very recently, HIV-1 has acquired that dubious honor and short of a new pandemic influenza virus outbreak in the next few years, is very likely to retain that position for some time to come. In some developed countries, HIV-1 infection can be avoided by safe sexual practices and/or kept under control by multidrug regimens. But in most developing countries, an effective vaccine offers the only hope of controlling in the future what has become an explosive pandemic.
