Showing papers on "Virus classification published in 1971"

Arboviruses: Incorporation in a General System of Virus Classification

Abstract: Publisher Summary The arboviruses constitute a set defined by the epidemiologic fact that they are transmitted between vertebrate hosts through the agency of biting, blood-sucking arthropods. The word arbovirus is an abbreviation for arthropod-borne virus of vertebrates; it defines a concept not related to the chemical, physical, or morphological properties of the virion. Arboviruses are viruses that are maintained in nature principally, or to an important extent, through biological transmission between susceptible vertebrate hosts by hematophagous arthropods. In the strict sense, the definition of arbovirus requires that the cycle of biological propagation from arthropod to vertebrate and back to arthropod be observed under controlled conditions as it occurs in nature. Properties of a virus that are not directly related to the transmission cycle, though helpful at times for orientation, should not be entertained as defining criteria. Easy isolation and propagation by intracerebral inoculation into newborn or adult mice or the inactivation of the virus by lipid solvents are properties shared with other viruses not remotely suspected of being arthropod-borne such as herpes and rabies.

Remarks on the Classification of Viruses

Abstract: Publisher Summary This chapter presents remarks on viruses, phanerogram, cryptogram, and gymnogram. It discusses various characteristics of the families of viruses. Viruses are defined by the sum of the distinctive traits of the virion. These distinctive traits are as follows: (1) presence of a single nucleic acid; (2) incapacity to grow and to divide; (3) reproduction from the genetic material only; (4) absence of enzymes for energy metabolism; (5) absence of ribosomes; (6) absence of information for the production of enzymes in the energy cycle; (7) absence of information for the synthesis of the ribosomal proteins; and (8) absence of information for the synthesis of ribosomal RNA and transfer RNA. The viral infectious particle presents a great diversity in composition and structure. Order could be achieved only through a classification, which is a system of order. The goal of biological classification is to group together organisms presenting certain analogies and certain affinities and, if possible, to also bring out phylogenic relationships. The conceptions relative to the methodology of taxonomy, which is the science of classification, are diverse. A virus may have evolved from a given sector of DNA within the host cell. It could also very well have derived from the corresponding RNA messenger that contains the same information, both qualitatively and quantitatively. Therefore, theoretically, different viruses could have originated from nucleic acids of different but complementary nature. The nucleic acid of viruses is either single- or double-stranded. Viruses, as is generally accepted, derive from the nucleic acid of their host. Thus, RNA viruses could possibly have their origin in the RNA messenger.

Oncogenic Viruses: A Survey of Their Properties

Abstract: Publisher Summary This chapter discusses the virus–host cell interaction, RNA oncogenic viruses, and possible human tumor viruses. The history of oncogenic viruses, defined as viruses capable of inducing neoplasms, either benign or malignant, and including leukemia, extends almost as far back as the first recognition of viruses as agents of disease. Oncogenic viruses occur in both of the two major classes of viruses—DNA- and RNA-containing. The chapter discusses the properties of oncogenic viruses within each of these major classes; it also presents the comparison of one with another and with nononcogenic members of the class. Oncogenic viruses are defined in terms of the effects they elicit in the host animal or host cell. However, the classification of viruses in general is no longer based on host response but primarily on the properties of the virion.