New Strains Intended for the Production of Inactivated Polio Vaccine at Low-Containment After Eradication

<div><p>Poliomyelitis has nearly been eradicated through the efforts of the World Health Organization’s Global Eradication Initiative raising questions on containment of the virus after it has been eliminated in the wild. Most manufacture of inactivated polio vaccines currently requires the growth of large amounts of highly virulent poliovirus, and release from a production facility after eradication could be disastrous; WHO have therefore recommended the use of the attenuated Sabin strains for production as a safer option although it is recognised that they can revert to a transmissible paralytic form. We have exploited the understanding of the molecular virology of the Sabin vaccine strains to design viruses that are extremely genetically stable and hyperattenuated. The viruses are based on the type 3 Sabin vaccine strain and have been genetically modified in domain V of the 5’ non-coding region by changing base pairs to produce a cassette into which capsid regions of other serotypes have been introduced. The viruses give satisfactory yields of antigenically and immunogenically correct viruses in culture, are without measurable neurovirulence and fail to infect non-human primates under conditions where the Sabin strains will do so.</p></div

Attenuation phenotype of passaged S19/N18S strains in transgenic mice.

<p>Attenuation phenotype of passaged S19/N18S strains in transgenic mice.</p

Persistence of adoptively transferred allogeneic lymphocytes in recipient animals.

<p>Solid lines represent peripheral blood samples; individual symbols represent lymph node biopsy samples. Dashed line indicates threshold for detection of CFDA-SE+ cells, calculated based on the mean of all negative samples plus two standard deviations. Animals are colour-coded by experimental group: <i>black</i> MHC-identical siblings; <i>red</i> MHC-identical unrelated; <i>blue</i> MHC-mismatch; <i>neg</i> negative control untreated animals.</p

Allogeneic Lymphocyte Transfer in MHC-Identical Siblings and MHC-Identical Unrelated Mauritian Cynomolgus Macaques

<div><p>The detailed study of immune effector mechanisms in primate models of infectious disease has been limited by the inability to adoptively transfer lymphocytes from vaccinated animals into naïve immunocompetent recipients. Recent advances in our understanding of the Major Histocompatibility Complex diversity of Mauritian cynomolgus macaques enabled the establishment of a breeding program to generate Major Histocompatibility Complex (MHC)-identical animals. The current study utilised this resource to achieve an improved model of adoptive transfer of lymphocytes in macaques. The effect of route of transfusion on persistence kinetics of adoptively transferred lymphocytes was evaluated in an autologous transfer system. Results indicated that peripheral persistence kinetics were comparable following infusion by different routes, and that cells were detectable at equivalent levels in lymphoid tissues six weeks post-infusion. In a pilot-scale experiment, the persistence of adoptively transferred lymphocytes was compared in MHC-identical siblings and MHC-identical unrelated recipients. Lymphocytes transferred intra-peritoneally were detectable in the periphery within one hour of transfer and circulated at detectable levels in the periphery and lymph nodes for 10 days. Donor lymphocytes were detectable at higher levels in MHC-identical siblings compared with unrelated animals, however the total time of persistence did not differ. These results demonstrate a further refinement of the lymphocyte adoptive transfer system in Mauritian cynomolgus macaques and provide a foundation for hitherto impractical experiments to investigate mechanisms of cellular immunity in primate models of infectious disease.</p></div

Reduction in plaques formed by S19 viruses shown in Fig 3 compared to permissive temperature: a, Hep2c cells, b.MRC5 cells.

<p>c shows the reduction in plaques formed by the S19 N18S series of viruses in Vero cells.</p

Experimental groupings and MHC genotype of cynomolgus macaques.

<p><i>rec</i>, recombinant MHC haplotype; a, reported ages and weights were on the day of allogeneic lymphocyte transfer.</p

Reduction in plaques formed by modified viruses at different temperatures compared to permissive temperature.

<p>a, L20B cells, b, Vero cells, c, Hep2c cells. The type 3 strains Sabin, Saukett, S15, S17, S18 and S19 were examined.</p

Immunogenicity after inactivation relative to reference strains.

<p>Immunogenicity after inactivation relative to reference strains.</p

Attenuation phenotype in transgenic mice of wild type and S19 derivative strains.

<p>Attenuation phenotype in transgenic mice of wild type and S19 derivative strains.</p

Base paired stem loop structures in domain V of the 5’ noncoding region of type 3 poliovirus.

<p>Arrow indicates base 472, which is a U in the Sabin type 3 strain but a C in revertants. Red base pairs show substitutions made; either of GC to AU, or mismatches or GU to AU pairs.</p