Studies on Simian Virus 40

Abstract
Summary: Simian virus 40 or vacuolating virus infection, in our experience as in that of others, is common in rhesus monkeys and uncommon in Cercopithecus monkeys that reach laboratories in this country. Cynomolgus monkeys resemble the Cercopithecus in this respect. The infection rate in laboratory rhesus has been high for a number of years, at least since 1953. Experimental infection of Cercopithecus monkeys with SV40 by intranasal instillation results in viremia but no apparent illness; virus also appears in the nasopharyngeal secretions and in the feces. Susceptible monkeys contract infection when intimately exposed to those that are excreting virus. A positive correlation exists between complement-fixing and neutralizing antibodies against SV40 in the sera of monkeys. Hence, in most serologic studies the more rapid complement fixation test may be substituted for the neutralization test. Serologic tests serve as a guide in selecting SV40-free monkeys whose kidneys are to be used for the preparation of cell cultures. Animals with antibodies are likely to provide contaminated tissues. On the other hand, monkeys which remain free of antibodies for a number of weeks while maintained under isolation conditions should provide tissues which do not yield SV40 in cell cultures. The multiplication of SV40 in primary cell cultures prepared from Cercopithecus monkey kidney, in continuous line cells obtained from the same source (BS-C-1) and in rhesus continuous cell culture (LLC-MK2) has been studied. The observations provide information on the time of appearance of cytopathogenic changes following inoculation of different amounts of virus, and the relation of the level of virus in the culture to presence of recognizable CPE and detectable complement-fixing antigen. Cultures of a continuous cell line (BS-C-1) developed from Cercopithecus kidney tissue are fully as susceptible to SV40 as are primary Cercopithecus kidney cell cultures. A stable line of rhesus kidney cells sustains the growth of SV40, develops cytopathogenic changes after prolonged incubation, but without the characteristic vacuolation produced by this agent in Cercopithecus cells and produces complement-fixing antigen. However, the rhesus stable line lacks the exquisite sensitivity of the continuous Cercopithecus line in detecting minute amounts of virus.

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