TOWARD A POLIOVIRUS-BASED SIMIAN IMMUNODEFICIENCY VIRUS-VACCINE - CORRELATION BETWEEN GENETIC STABILITY AND IMMUNOGENICITY

Recombinant polioviruses expressing foreign antigens may provide a con venient vaccine vector to engender mucosal immunity, Replication-compe tent chimeric viruses can be constructed by fusing foreign antigenic s equences to several positions within the poliovirus polyprotein, Artif icial cleavage sites ensure appropriate proteolytic processing of the recombinant polyprotein, yielding mature and functional viral proteins , To study the effect of the position of insertion, two different reco mbinant polioviruses were examined, A small amino-terminus insertion d elayed virus maturation and produced a thermosensitive particle, In co ntrast, insertion at the junction between the P1 and P2 regions yielde d a chimeric poliovirus that replicated like the wild type, Eight diff erent chimeras were constructed by inserting simian immunodeficiency v irus (SIV) sequences at the P1/P2 junction, All recombinant viruses re plicated with near-wild-type efficiency in tissue culture cells and ex pressed high levels of the SIV antigens, One of the inserted fragments corresponding to gp41 envelope protein was N-glycosylated but was not secreted, Inserted sequences were only partially retained after few r ounds of replication in HeLa cells, This problem could be remedied to some extent by altering the sequences flanking the insertion point, Re ducing the homology of the direct repeats by 37% decrease the propensi ty of the recombinant viruses to delete the insert, To determine the i mmunogenic potential of the recombinants, mice susceptible to poliovir us infection were inoculated intraperitoneally, The antibody titers el icited against Gag p17 depended on the viral doses and the number of i noculations, In addition, recombinants which display higher genetic st ability were more effective in inducing an immune response against the SIV antigens, and inoculation with a mix of recombinants carrying dif ferent SIV antigens (a cocktail of recombinants) elicited humoral resp onses against each of the individual SIV sequences.