Dear All,
As I informed you few weeks before currently we are developing multivalent vaccines using PPRV as a viral vector.
To address the question whether immunosupression nature of PPRV affect the antibody production of other vaccines coadministered with PPR vaccine, I had recently conducted an vaccine challenge experiment in goats.
3 groups of goats (n=4) were used in this study. The first group had been administered both PPR and FMD conventional vaccines, the second group had been administered PPR rescued live attenuated vaccine (recovered from c-DNA clone of live attenuated conventioanal vaccine) and FMD vaccine and third group had been administered only FMD vaccine. After 28 days post challenge with virulent virus, both the conventional and rescued live attenuated PPR vaccines provided 100% perotection which is expected. There was no difference of antibody level against FMDV in these 3 groups. So this proved that immunosupression nature of PPRV does not effect the antibody production of other vaccines coadministered with PPR.
Regards
Satya.
The issue of possible immunosuppresion by PPR vaccine causing untoward effects with other vaccines, as well as the concept of antigenic competition will need to be addressed and answered to satisfy some veterinary authorities. I am assuming that the PPR vaccine used in the experiment described above was strain Nig75/1 and that the FMD vaccine was a dead one. I think previous work with RP cell-culture attenuated vaccine and both dead FMD and other "dead" antigens tended to show that the immune responses to the combined/simultaneous inoculations were comparable to those when the RP and dead vaccines were given separately and at different times. In the human field we know that the vaccine combining measles virus with both mumps and
rubella live virus vaccines works very effectively (before someone draws my attention to it, I know there was a controversy over this vaccine but the view I give above is that of the WHO and most medical authorities). However, when Dr Alain Provost, working in Chad, tested live combined vaccines of RP and bovine virus diarrhoea virus in cattle the result was severe disease and this combination was never used. In the field I saw RP vaccine contaminated with BVDV cause quite severe disease - the BVD virus was not a vaccine strain but it caused little or no disease (as often the case) when inoculated on its own. I guess what I am saying is that results with a dead antigen may not be directly applicable to live vaccines used with PPR vaccine and before entering routine use all combinations should really be backed up by solid experimental evidence of safety and efficacy. To date the field evidence where we use PPR and SGP
is good but we haven't tried every combination yet. We also need to bear in mind that this experiment and some other studies have used the Nig75/1 strain of PPRV vaccine but there are a number of different strains of PPRV vaccine being used in the field today.
Old RP vaccines definitely caused immunosupression but the cell-culture attenuated RP vaccine seemed not to. In fact when you see just how fast the RP and PPR vaccines work in the face of disease in the field, immunosuppression doesn't spring to mind. Pirbright had a very detailed immunological project on RP vaccine in the early 1990s and I think I still have a letter in my files admitting that some experiments into cell-mediated immunity indicated immunostimulation with TCRV not immunosuppression! And please excuse the RP analogies as usual.
Moderator.