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Biomedical subjects

P A Webb

Publications and source records attributed to P A Webb.

At least 55 records · Page 3Linked to original sources
PubMed1975

Infection of wild and laboratory animals with Machupo and Latino viruses.

Natural infection with Machupo and Latino viruses occurs only in the cricetine rodent Calomys callosus. Machupo virus induces fatal infection in suckling mice and hamsters, and in adult guinea-pigs, marmosets, and rhesus monkeys. Latino virus kills only suckling hamsters; it produces chronic but non-viraemic infection in Calomys rodents.Machupo virus, in contrast, induces a viraemic immunotolerant infection in suckling Calomys, and a split response in animals more than 9 days of age. Tolerant infection is associated with haemolytic anaemia and splenomegaly, lesions not observed in animals able to clear viraemia and produce circulating neutralizing antibodies. Experimental increase in the fraction of tolerant response was obtained by decreasing the virus dose or by phenotypic inbreeding of rodents. Long-term effects of tolerant infection included mild runting, decreased survival time, and almost total sterility among females, largely caused by fatal virus infection of embryos.

Age Factors↗
PubMed1974

Arenaviruses.

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Antigens, Viral↗
PubMed1970

Serological relationship of the Tacaribe complex of viruses to lymphocytic choriomeningitis virus.

By means of the indirect fluorescent-antibody test, cross serological reactivity was demonstrated between lymphocytic choriomeningitis (LCM) virus and the viruses of the Tacaribe complex. Antisera to all members of the Tacaribe complex reacted with LCM virus; LCM antisera gave significant staining of Amapari virus, but minimal or inconsistent reactions with Tacaribe virus, and no reaction with two other viruses of the Tacaribe complex. A low level cross-reaction was observed in complement fixation tests of Machupo and Pichinde antisera against LCM antigen. Immunization with Tacaribe and Amapari viruses did not protect mice against challenge with LCM virus. Because of the identical appearance of the virions, the sharing of antigens, and the many biological similarities between LCM and the Tacaribe complex viruses, it is proposed that they be considered as constituting a new taxonomic group of viruses.

Animals↗
PubMed1970

Arenoviruses in Vero cells: ultrastructural studies.

Thin-section electron microscopy was carried out on Vero green monkey kidney cell cultures infected with some viruses of the newly constituted arenovirus group. Junin, Machupo, Amapari, Pichinde, Parana, Tamiami, and Latino viruses were morphologically identical and indistinguishable from lymphocytic choriomeningitis virus, the prototype virus of the group. Virus particles were round, oval, or pleomorphic, 60 to 280 nm in diameter, and matured via budding from plasma membranes. Most characteristically, particles contained various amounts of homogeneous, 20- to 25-nm, dense granules; these granules in large masses also formed distinctive intracytoplasmic inclusions. In negative-contrast preparations from infected Vero cell culture supernatant fluids, several of the viruses appeared as pleomorphic membrane-bound forms with rather pronounced surface projections. Most particles were between 90 and 220 nm in diameter, although some reached 350 nm in their longest dimension. Internal structure was not resolved by negative-contrast electron microscopy. All observations supported the current delineation of a distinct arenovirus group.

Animals↗
PubMed1965

Chronic infection of rodents by Machupo virus.

Machupo virus, the etiologic agent of human hemorrhagic fever in Bolivia, induced chronic asymptomatic infection in laboratory hamsters and colonized individuals of the peridomestic, wild, South American rodent, Calomys callosus. Viruria was detected for more than 500 and 150 days, respectively, in the two species. Chronic viremia was shown only for Calomys. Virus-neutralizing substances were present in parenterally infected adult animals, but not in animals born to, and in contact with, an infected female. Chronic infection in wild rodents may be an important mechanism in the natural history of Machupo and related virus infections.

Animals↗