Vaccination of sows against type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) before artificial insemination protects against type 2 PRRSV challenge but does not protect against type 1 PRRSV challenge in late gestation

Abstract

The objective of the present study was to determine the effects of the commercially available type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)-based modified live vaccine against type 1 and type 2 PRRSV challenge in pregnant sows. Half of the sows in the study were vaccinated with a type 2 PRRSV-based vaccine 4 weeks prior to artificial insemination while the other half remained non-vaccinated. Sows were then challenged intranasally with type 1 or type 2 PRRSV at 93 days of gestation. The sows which received the type 2 PRRSV-based vaccine followed by type 2 PRRSV challenge had significantly higher neutralizing antibody titers against type 2 PRRSV than they did against type 1 PRRSV. These same sows had higher frequencies of IFN-γ-secreting cells when stimulated with type 2 PRRSV compared to those stimulated with type 1 PRRSV. Subsequent virological evaluation demonstrated that the type 2 PRRSV-based vaccine reduced the type 2 PRRSV load but not the type 1 PRRSV load present in the blood of the sows. Additionally, vaccination of pregnant sows with the type 2 PRRSV-based vaccine effectively reduced the level of type 2 PRRSV nucleic acids observed in fetal tissues from type 2 PRRSV-challenged sows but did not reduce the level of type 1 PRRSV nucleic acid observed in fetal tissues from type 1 PRRSV-challenged sows. This study demonstrates that the vaccination of pregnant sows with the type 2 PRRSV-based vaccine protects against type 2 PRRSV challenge but does not protect against type 1 PRRSV challenge.

Efficacy and safety of simultaneous vaccination with two modified live virus vaccines against porcine reproductive and respiratory syndrome virus types 1 and 2 in pigs

“…In contrast, vaccination with the PRRSV-2 vaccine had limited effect on viremia following challenge with PRRSV-1 which also is in accordance with the outcome of most of the previous comparable studies with this vaccine [5,26,34].…”

A Synthetic Porcine Reproductive and Respiratory Syndrome Virus Strain Confers Unprecedented Levels of Heterologous Protection

“…PRRSV is classified into 2 major types: type 1 and type 2. There is very limited cross-protection between type 1 and type 2 PRRSV strains (17,18,70). Genetically, type 1 and type 2 PRRSVs share ϳ65% sequence identity (20,21).…”

“…Current PRRS MLV vaccines confer excellent protection against a PRRSV strain that is genetically similar to the vaccine strain (14,15). However, the levels of protection against heterologous PRRSV strains are highly variable and are considered suboptimal in all cases (10,(14)(15)(16)(17)(18)(19).…”

Innate and adaptive immunity against Porcine Reproductive and Respiratory Syndrome Virus

“…However, it should be kept in mind that: (1) Protective NAb titers in blood (i.e. 1:8-1:32) are hard to obtain with just one application of currently available PRRSV vaccines (Han et al, 2014;Roca et al, 2012;Trus et al, 2014;Zuckermann et al, 2007); (2) Most of NAb are specific for the vaccine strain (homologous), as significant titers of cross-neutralizing antibodies are rare (Vu et al, 2011;Zhou et al, 2012); and (3) The anamnestic induction of NAb observed after heterologous challenge in some previously sensitized (vaccinated or previously infected) animals indicates a good prognosis of broad heterologous protection, but the anamnestic NAb response only seems to occur when a certain period of time has elapsed between primary sensitization and subsequent secondary heterologous challenge. The necessary length of time appears to be 2-3 months, if the challenge is one month or less, the anamnestic NAb response is not detected (Osorio et al, 1998;Scortti et al, 2006;Zuckermann et al, 2007).…”