Untersuchungen der genetischen Varianz aktueller Isolate des porzinen Parvovirus

Studies on the genetic variability of recent isolates of porcine
parvovirus The aim of this study was to review the antigenetic
variability of porcine parvovirus and to examine the role of
porcine parvovirus in reproductive failure. Organ specimens of 500
fetuses and stillborn piglets from a total of 172 farms were
analysed. Total DNA was isolated from the explants and quantitative
as well as qualitative PCR was subsequently carried out. In 82
samples (15,8%) out of 28 farms (16,3%), PPV was diagnosed. In this
study, we were able to show that rectal swabs are suitable
substrates from which to detect porcine parvovirus in sows using a
PCR analysis. In 12 out of 19 rectal swabs PPV genome was
amplified. In one PPV-positive sample the sow was infected a
minimum of 45 days before the rectal swab was collected. An attempt
was made to cultivate porcine parvovirus out of 22 PPV-positive
organ specimens of different origin. However, only 5 isolates could
be cultivated and the production of progeny virus was very low in
two of these isolates. Although multiple passages were performed,
the virus yield did not increase. As the viral capsid is the target
of host protective immunity against PPV, the complete gene of the
structural protein of 7 field isolates was amplified and sequenced.
The obtained sequences were aligned with the porcine
parvovirus-strains NADL-2, Kresse, one challenge-virus of the year
1986 and with the vaccine strain of IDT. The sequence homology
among the isolates sequenced is very high (on the level of
nucleotide acids minimum 98,7%, on the level of amino acids minimum
97,7). Phylogenetic analysis revealed that there is only a distant
relationship between NADL-2, Kresse and the challenge-virus on the
hand and the field isolates on the other hand. A comparison of the
aligned PPV-sequences from field isolates with the published
sequence of two primers recommended for diagnostic PCR revealed
single nucleotide differences. Therefore, it appears possible that
the primer sequences published may not be suitable for a diagnostic
PPV-PCR in the field. Taken as a whole, these data suggest that the
porcine parvovirus may have altered antigenetically. Furthermore,
the obtained sequences from field isolates of PPV now permit the
examination of the antigenetic consequence of this evolution to
develop effective vaccines against the PPV strains now present in
the field.