Abstract
In a previous communication 1 the serial passage of the human influenzal virus in the European hamster (Cricetus cricetus) was reported. While this hamster was shown to be susceptible to a recently isolated virus strain, it was not demonstrated, because of lack of material at the time, whether or not infection could be transferred directly from humans.
This present report deals with the infection of the Syrian hamster (Cricetus auratus) from throat-washings of persons ill with epidemic influenza.
Material. The washings were collected in buffered broth during the early months of 1939 from persons acutely ill with influenza. The presence of virus originally in these specimens had been demonstrated by the inoculation of ferrets. 2 The washings had been preserved for 9 to 10 months in a low-temperature cabinet at −76°C when the inoculation of the hamsters was made. The hamsters employed were from 3 to 5 months of age and weighed approximately 100 g each.
Method. Preceding inoculation, 1 cc of blood was withdrawn by cardiac puncture from each hamster. From 0.3 to 0.4 cc of unfiltered throat-washing was administered intranasally while the animal was under light ether-anesthesia. Twelve to 14 days after the intranasal inoculation a second blood sample was taken. The blood serum obtained before and following inoculation was then titrated for neutralizing antibodies against the PR8 strain of influenzal virus.
Results. So far, 4 preserved washings obtained during the 1939 epidemic, but from separate localities, have been tested. All of these specimens were known to contain virus originally.
None of the blood samples taken before inoculation showed any neutralizing effect upon the virus in a 1:2 serum-mixture, but samples taken 12 to 14 days after inoculation of the hamsters with each of these 4 washings all neutralized 1000 M.L.D. of the virus in dilutions above 1:32. Despite the immune response, these animals manifested no symptoms or gross pathological lesions which could be used as diagnostic criteria.
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