Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is an
important pathogen that endangers the swine industry worldwide.
Recently, lineage 1 PRRSVs, especially NADC30-like PRRSV, have become
the major endemic strains in many pig-breeding countries. Since 2016,
NADC30-like PRRSV has become the predominant strain in China.
Unfortunately, current commercial vaccines cannot provide sufficient
protection against this strain. Here, an attenuated lineage 1 PRRSV
strain, named SD-R, was obtained by passaging NADC30-like PRRSV strain
SD in Marc-145 cells for 125 passages. Four-week-old PRRSV-free piglets
were vaccinated intramuscularly with
105.0TCID50 SD-R and then challenged
intramuscularly (2 ml) and intranasally (2 ml) with homologous
NADC30-like PRRSV SD
(1×105.0TCID50/ml) and heterologous
NADC30-like PRRSV HLJWK108-1711
(1×105.0TCID50/ml). The results showed
that 5 of 5 immunized piglets had a perceptible humoral immune response
to vaccination and did not develop fever or clinical diseases after
NADC30-like PRRSV challenge. Additionally, compared to challenge control
piglets, vaccinated piglets gained significantly more weight and showed
much milder pathological lesions. Furthermore, the viral replication
levels of the immunized group were significantly lower than those of the
challenge control group. These results demonstrate, for the first time,
that lineage 1 PRRSV SD-R is a good candidate for an efficacious vaccine
against NADC30-like PRRSVs.