Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) is of major economic significance to swine industry. There is no effective vaccine currently available to combat PRRS. In previous studies, we demonstrated that virus-neutralizing antibodies are important for protective immunity against PRRSV. These neutralizing antibodies constitute a significant parameter for evaluating the efficacy of a vaccine. Although four viral glycoproteins (GPs) are present in PRRSV, their roles in the virus’ biology, especially in their capacity to induce a protective immune response in the pig, remains poorly understood. Development of safe and efficacious vaccines to combat PRRSV infections requires a basic understanding of the role of these GPs in virus biology. In particular, identification and characterization of the viral glycoproteins that interact with the cellular receptor (CD163), which is a key component of the cell that permits the penetration and infection of the cells by PRRSV. Furthermore, determining the precise areas of contact between these viral GPs and CD163 is important in developing strategies to inhibit the process of binding of the virus to the cells, so that virus infections can be blocked. In a previously funded NPB project (#08-253), we had demonstrated that two (namely, the GP2 and GP4) of the four PRRSV GPs specifically interact with CD163. One of the objectives of this proposal (#09-248) has been to delineate the regions of these two GPs that interact with CD163. Other objectives of the 09-248 proposal were to generate antibodies to these small regions of the GPs as well as to the entire proteins for future studies to determine if any of these antibodies possess PRRSV neutralizing (or inactivating) activity.
 
To carry out the studies in the proposed objectives, we generated a series of mutants of PRRSV GP2 and GP4 proteins in which various regions were specifically removed by manipulating the plasmids encoding these proteins. We then examined these proteins for their ability to interact with CD163 to ascertain the regions important for such interactions. Our results identified the regions of GP2 and GP4 that appear to interact with CD163. Furthermore, we generated recombinant baculoviruses that expressed these viral GPs. The viral proteins were purified from the cells and have been used to generate antibodies.
Further studies will be conducted to characterize these antibodies in the future. In addition, we are now exploring, beyond the life of this grant, alternative novel strategies to obtain high affinity swine monoclonal antibodies that would inactivate PRRSV with very high efficiency. We are conducting these studies in collaboration with an industry partner (Trellis Biosciences, San Francisco, CA). The results obtained through this NPB support (09-248) have been critical for initiating such collaborative work with the biotech industry. Part of our studies supported by the NPB grant (#09-248) has also been recently published in Virology (Das et al., Virology, 410: 385-394, 2011; a copy of the paper has also been forwarded to B. L. Everitt).
Contact information: Asit K. Pattnaik, Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, E126 Beadle Center, 1901 Vine Street, Lincoln, NE 68588, Phone: 402-472-1067""; Fax: 402-472-8722""; e-mail: [email protected]