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HIV epidemic related to nosocomial transmission in Romanian nursed children represents up to now more than 50% of paediatric AIDS cases in Europe. Although the sources of this epidemic are obscure, HIV-1 subtype F, a minor form in Brasil and Africa, realised a founder effect in this risk group, thus becoming the major form in Romanian epidemic. This study presents the results of the virus isolation from HIV-infected children in Northeast Romania. Heteroduplex mobility assay (HMA) was performed in order to establish HIV-1 viral subtype for 6 isolates. All tested HIV-1 strains were proved to belong to F subtype. So, our study confirm that HIV-1 subtype F is responsible for the epidemic in the risk group of Romanian nosocomially infected children.

Cell cultures with a different multiplication potential in vitro, depending upon the strain source used, were obtained from mouse embryos belonging to the CVA, C57 Black A2G and Swiss strains. Only the Swiss 12 culture underwent spontaneous transformation and was carried through more than 50 passages in vitro. The Swiss-12 substrate proved not to be contaminated either by viruses or micoplasma. It is less sensitive than other elective cell substrates to infection with attenuated polioviruses, cytopathogenic Coxsackie A9 virus and vaccinia virus, but its sensitivity to infection with Herpes simplex type 1 virus is similar to that of human embryo fibroblasts. After a high number of passages the Swiss-12 substrate permits, in comparison to other cell substrates (human heteroploid Hep-2 line, human embryo fibroblasts), a highly efficient qualitative differentiation between the growth media and calf serum.

Differences in the susceptibility to paralytogenic infection with Coxsackie A10 virus were found in neonate and suckling mice belonging to A2G, ICR-K and CBA strains and ICR-K/CBA and CBA/ICR-K hybrids in the F1 generation. At the first passage in vivo the more susceptible strains selected paralytogenic viral particles from among the cytopathogenic and non-pathogenic Coxsackie A10 virus populations. The differences in susceptibility could not be related either with the humoral immune response to virus or to the rate of fixation of virus on the neonate mouse muscle cell receptors. These differences are, however, in agreement with the data concerning the synthesis of interferon in the striated muscle, the lots with greater resistance to viral infection being also those which synthesize interferon in higher concentrations. The hybrids resulting from the parental strains more susceptible to virus, presented a resistance superior to that of the parents.

The crown-like projections on the surface of the particles permits differentiation of coronaviruses from other riboviruses and their individualization as a distinct family. Recognition of their role in the aetiology of respiratory, enteral and encephalitic infections has promoted investigations for the finding of preventive vaccines. Selection of the strains showed that their immunogenicity depends upon the density and salience of the crown-like projections, the antigenic relationship of the projections determining cross serologic reactions between different species. At present experiments are being carried out on animals with vaccines prepared with antigenically related heterologous cornavirus species, not pathogenic for the host, and with subunitary vaccines prepared from the projections of the homologous species. The Coronaviridae family established on morphologic criteria is thus confirmed by the immunologic relationship and specificity of its members.