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The pregnant guinea-pig as a model for studying influenza virus infection in utero: infection of foetal tissues in organ culture and in vivo.

Organ cultures of guinea-pig foetal tissues showed a similar pattern of susceptibility to influenza virus to that already observed for human (Rosztoczy et al., 1975) and ferret (Sweet, Toms and Smith, 1977) foetal tissues. Respiratory, alimentary and urogenital tract tissues were susceptible whereas neural and lymphopoietic tissues were insusceptible. However, of the foetal membranes (amnion, chorion, umbilical cord and placenta) only the chorion was susceptible, in contrast to the corresponding ferret tissues, all of which were susceptible. The insusceptibility of the placenta paralleled that of human placenta which is similarly haemomonochorial in structure. Following intracardial inoculation of high titre virus (ca 10(9-4) EBID50) into pregnant guinea-pigs virus was isolated from all foetal membranes (amnion, chorion, umbilical cord and placenta), but in low titre. Although sporadic isolations were made from foetal tissues (intestine, kidney, heart, liver and spleen) there was no evidence for viral replication in these tissues. These results are discussed in relation to possible infection of the human foetus in utero with influenza virus.