New East European sub-type 3 PRRS virus isolate found

Previously reported here

//11 Jun 2010

A group of researchers from Ghent University in Belgium led by Dr Hans Nauwynck has published a paper on the pathogenesis and antigenic characterisation of a new East European sub-type 3 PRRS virus isolate in BMC Veterinary Research*.

First author, U. Karniychuk, and colleagues explain that the PRRS virus (PRRSV) is divided into a European and North American genotype. East European PRRSV isolates have been found to be of the European genotype but form different sub-types.

In the present study, PRRSV was isolated from a Belarusian farm with reproductive and respiratory failure and designated 'Lena'. Analyses revealed that Lena is a new East European sub-type 3 PRRSV isolate. The main purpose of this investigation was to study the pathogenesis and antigenic characteristics of the PRRS virus (Lena).

Results
Obvious clinical and virological differences were observed between the animals inoculated with a recent European sub-type 1 PRRSV isolate (Belgium A) and animals inoculated with PRRSV (Lena). Three out of six pigs inoculated with PRRSV (Belgium A) had anorexia and low fever at three, four and five days post-inoculation. High fever, anorexia and depression were prominent signs in most pigs inoculated with PRRSV (Lena) between two and 28 days post-inoculation. Four pigs out of ten died during the experiment. Arcanobacterium pyogenes was isolated from lungs of one animal that died, and Streptococcus suis was isolated from lungs of one animal that was euthanised.

The difference in viral titres in sera from PRRSV (Belgium A) and PRRSV (Lena)-infected pigs was statistically significant (p>

High viral titres were detected in lungs (102.3 to 107.7 TCID50/g tissue), tonsils (102.0 to 106.2 TCID50/g tissue) and inguinal lymph nodes (102.2 to 106.6 TCID50/g tissue) until 35, 28 and 35 days post-inoculation, respectively. To examine the antigenic heterogeneity between the East European sub-type 3 isolate Lena, the European sub-type 1 strain Lelystad and the North American strain US5, sets of mono-specific polyclonal antisera were tested in immunoperoxidase monolayer assays (IPMAs) with homologous and heterologous viral antigens.

Heterologous antibody titres were significantly lower than homologous titres (p=0.01-0.03) for antisera against PRRSV (Lena) at all sampling time points. For antisera against PRRSV (Lelystad) and PRRSV (US5), heterologous antibody titres were significantly lower than homologous titres at 14 and 21 days post-inoculation (p=0.01-0.03) and at 10 and 14 days post-inoculation (p=0.04), respectively.

* Karniychuk U.U., M. Geldhof, M. Vanhee, J. Van Doorsselaere, T.A. Saveleva and H.J. Nauwynck 2010. Pathogenesis and antigenic characterization of a new East European sub-type 3 porcine reproductive and respiratory syndrome virus isolate. BMC Veterinary Research, 6:30. doi:10.1186/1746-6148-6-30.