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Biomedical subjects

N Nathanson

Publications and source records attributed to N Nathanson.

133 records · Page 8Linked to original sources
PubMedDate not supplied

Eradication of poliomyelitis in the United States.

Mass immunization with oral poliovirus vaccine (OPV) was begun in the United States in 1963, and the least natural outbreak of poliomyelitis occurred in 1972. Since immunization programs fail to reach the total population, eradication has been achieved in the presence of a residual susceptible population of at least 5% (2-5 million children under the age of 15 years). It is proposed that the fade-out of wild polioviruses is explained by their disappearance during the winter, a low point in the yearly cycle of the virus. In the post-eradication era, the continued presence of millions of susceptible children and adults presents a constant potential hazard. Every effort should be made to maintain maximal levels of immunization with oral poliovirus vaccine and to prevent the reintroduction of wild polioviruses into the United States.

Adolescent↗
PubMedDate not supplied

Epidemiologic aspects of poliomyelitis eradication.

Mass immunization with oral poliovirus vaccine was begun in the United States in 1963, and the last outbreak of natural poliomyelitis occurred in 1972. In the subsequent 10 years, there has been only one outbreak, in 1979, due to the introduction of wild polio-virus to an underimmunized Amish population. Paradoxically, eradication occurred even though 5%-10% of the population zero to 14 years of age were unimmunized and susceptible. It is suggested that this eradication was due to two factors. First, the marked seasonality of poliovirus infections, imposed on a reduced number of susceptibles , led to wintertime fade-outs of wild poliovirus over sizable areas. Second, although reintroductions into virus-free areas did occur, they did not equal the frequency of fade-outs. This led, in turn, to an annual stepwise reduction in the number of infected states over a 10-year period, culminating in eradication. Measles makes an instructive comparison because it has more stubbornly resisted eradication. Although regional fade-outs of measles have occurred regularly during the seasonal low, measles is more frequently reintroduced because of its greater transmissibility. It is suggested that this difference in reintroduction was a critical determinant of the difference between the eradicability of measles and poliomyelitis.

Adolescent↗
PubMedDate not supplied

Experimental visna in Icelandic sheep: the prototype lentiviral infection.

A brief review of experimental infection of Icelandic sheep following intracerebral inoculation of neurotropic strains of visna virus is presented. In vivo replication of the virus is restricted, so that some cells carry the deoxyribonucleic acid provirus as an unexpressed genome. This cellular restriction plays a major role in the slow progression of the infection, abetted by neutralizing antibody in serum and spinal fluid. The latent provirus maintains the viral genome in the presence of an active immune response, since immune surveillance cannot recognize cells that are not synthesizing viral antigens. Infected Icelandic sheep experience two types of diseases of the central nervous system: a subclinical subacute encephalitis begins within weeks of infection in most sheep; and at irregular intervals from 0.5-8 years after infection, clinical paresis develops in the majority of Icelandic sheep and is accompanied by discrete focal demyelinating lesions in the spinal cord. The subacute encephalomyelitis is probably mediated by an antiviral cellular immune response, whereas the pathogenesis of the focal demyelinating lesions is still obscure. During persistent infection there is some selection for neutralization-resistant antigenic variants of the infecting serotype, and these are isolated at a frequency of approximately 15%. However, variants do not replace the infecting serotype, and antigenic drift does not appear essential for persistence of visna virus or for the occurrence of demyelinating lesions.

Animals↗
PubMedDate not supplied

Towards an AIDS vaccine: the role of nonhuman primates.

Over the last 10 years, about 20 human immunodeficiency virus (HIV) vaccine candidates have been tried in humans, with disappointing results as gauged by limited immune responses or protection against infection. These difficulties suggest that a new strategy is needed to test systematically new vaccine candidates. That opportunity is now afforded by nonhuman primate models with SIV, which have been shown to provide an excellent mirror of HIV infection in humans. The recent introduction of SHIVs, chimeric viruses that carry the HIV envelope and are able to infect and cause AIDS in monkeys, also has added an important additional research tool. These models can be used to address a series of questions, including the following: (1) Can protection be provided by partial immunity or is sterilizing immunity required? (2) What are the immune parameters that best predict protection against a potentially pathogenic challenge? (3) What role does mucosal immunity play and can it be induced by practical modes of immunization? (4) Can an attenuated virus be selected that is both protective and safe? An orderly strategy for the evaluation of vaccine candidates could be adopted that would involve several phases: (a) the selection of a limited set of challenge models, ranging from very severe to mild and requiring consideration of primate species, age, route of infection, and challenge viruses; (b) the assessment of candidate vaccines using comparable virus challenges; and (c) accelerated testing in humans of any candidate vaccines that have met a 'proof of efficacy' in primates.

AIDS Vaccines↗