Dear colleagues,
With respect to the degree of seroconversion, surely what matters is whether the immune response is sufficient for protection, not how high the VNT titre is?
We have a tendency to focus on the measurable antibody titre, but I want to point out again that it has never been shown that it is serum antibody that is protective. It could be the (much more difficult to measure) T cell immunity. The OIE manual only says that a PPRV vaccine has to give a VNT titre of 1:10 because we know from experience that an effective PPRV vaccine will give such a titre, not that such a titre is protective.
For those not familiar with the old RPV literature, it was shown that recombinant poxviruses that gave no detectable anti-RPV antibody were still protective. Yilma et al made recombinant RPV glycoproteins, injected them into cattle, and got nice antibody responses – but no protection.
The difference between sheep and goats may be in the balance of immune responses; as Dr Singh has just posted, PPRV may replicate a bit better in goats, and so elicit a higher immune antibody response. The only thing that counts, in the end, is whether the animal is protected.
best wishes
Michael
|
Michael D Baron PhD Group Leader, Paramyxo&Bunyaviruses t +44 (0) 1483 231024/1072/1145 |
|
Preventing and controlling viral diseases The Pirbright Institute, Ash Road, Pirbright, Woking, Surrey GU24 0NF t +44 (0)1483 232441 f +44 (0)1483 232448 e [log in to unmask] |
|
A company limited by guarantee, registered in England no. 559784. The Institute is also a registered charity. Director: Professor John Fazakerley BSc, MBA, PhD, FSB, FRCPath. The Pirbright Institute receives strategic funding from the Biotechnology and Biological Sciences Research Council. |
From: Establishment of a PPR Global Research and Expertise Network
(PPR-GREN) [mailto:[log in to unmask]] On Behalf Of Paul Rossiter
Sent: 07 February 2014 15:59
To: [log in to unmask]
Subject: From Dr Srinivasan on the possible need for species specific vaccines
Dear Colleagues,
When we first developed PPR Sungri/96 vaccine, during the initial field
evaluation of vaccine we observed goats were better sero-converters than
Sheep. In a study involving more than 500 post-vaccinate sera samples in
each of the species, we observed 98% sero-conversion in goats and 83% in
sheep. Even the VN titer was lesser in sheep than goats (eg., most of the
goats had 1:64 to 1:128 and sheep it was 1:32 to 1:64).
PPR Sungri/96 virus which was used to develop attenuated vaccine was
originally rescued from post-mortem samples from a goat died in the PPR
outbreak.
Does this suggests that we should have separate vaccine candidates for
sheep and goat? I must confess I am not keeping abreast of PPR literature
as I have moved away from PPR research almost 11 years back.
Regards
Srinivas
I hope that several of you will give us your views on this radical idea - moderator
________________________________
Dr.B.P.Srinivas
Principal Scientist
Indian Veterinary Research Institute (IVRI)
Hebbal, Bangalore-560024
India
Tel: 91-80-23410729 (Work)
Fax: 91-80-23412509
To unsubscribe from the FAO-AnimalHealth-L list, click the following link:
https://listserv.fao.org/cgi-bin/wa?SUBED1=FAO-AnimalHealth-L&A=1
To unsubscribe from the FAO-AnimalHealth-L list, click the following link:
https://listserv.fao.org/cgi-bin/wa?SUBED1=FAO-AnimalHealth-L&A=1