Lucas Taylor

Insertion and deletion in a non-essential region of the nonstructural protein 2 (nsp2) of porcine reproductive and respiratory syndrome (PRRS) virus: effects on virulence and immunogenicity

Developing a vaccine that can differentiate infected and vaccinated animals (DIVA) is a new challenge in the design of a vaccine for porcine reproductive and respiratory syndrome virus (PRRSV). Nonstructural protein 2 (nsp2) is the single largest viral product, and it has multiple roles in polypeptide processing and replication complex formation. Using reverse genetics and an infectious PRRSV cDNA clone, we constructed several deletion mutants in the non-essential region of nsp2. One mutant, which has a 131 amino acid deletion within a relatively conserved region of nsp2, was recovered and found to produce a viable virus. The deleted region was replaced with a peptide tag encoding eight amino acids. A recombinant virus containing the 131 amino acid deletion was found to produce normal virus yields in MARC-145 cells and porcine alveolar macrophages (PAM); however, gross and micro-histopathology showed that the virus was less virulent in pigs. The 131 amino acid peptide was expressed as a recombinant protein and used to coat enzyme-linked immunosorbent assay (ELISA) plates. This peptide was recognized by sera from pigs infected with wild-type virus, but not by sera from pigs infected with the deletion mutant. The results from this study show that nsp2 is an important target for the development of marker vaccines and for virus attenuation.

Fetal protection in heifers vaccinated with a modified-live virus vaccine containing bovine viral diarrhea virus subtypes 1a and 2a and exposed during gestation to cattle persistently infected with bovine viral diarrhea virus subtype 1b.

OBJECTIVE To determine efficacy of a modified-live virus (MLV) vaccine containing bovine viral diarrhea virus (BVDV) 1a and 2a against fetal infection in heifers exposed to cattle persistently infected (PI) with BVDV subtype 1 b. ANIMALS 50 heifers and their fetuses. PROCEDURES Susceptible heifers received a placebo vaccine administered IM or a vaccine containing MLV strains of BVDV1a and BVDV2a administered IM or SC. On day 124 (64 to 89 days of gestation), 50 pregnant heifers (20 vaccinated SC, 20 vaccinated IM, and 10 control heifers) were challenge exposed to 8 PI cattle. On days 207 to 209, fetuses were recovered from heifers and used for testing. RESULTS 2 control heifers aborted following challenge exposure; both fetuses were unavailable for testing. Eleven fetuses (8 control heifers and 1 IM and 2 SC vaccinates) were positive for BVDV via virus isolation (VI) and for BVDV antigen via immunohistochemical analysis in multiple tissues. Two additional fetuses from IM vaccinates were considered exposed to BVDV (one was seropositive for BVDV and the second was positive via VI in fetal tissues). A third fetus in the SC vaccinates was positive for BVDV via VI from serum alone. Vaccination against BVDV provided fetal protection in IM vaccinated (17/20) and SC vaccinated (17/20) heifers, but all control heifers (10/10) were considered infected. CONCLUSIONS AND CLINICAL RELEVANCE 1 dose of a BVDV1a and 2a MLV vaccine administered SC or IM prior to breeding helped protect against fetal infection in pregnant heifers exposed to cattle PI with BVDV1b.

Vaccination of piglets at 1 week of age with an inactivated Mycoplasma hyopneumoniae vaccine reduces lung lesions and improves average daily gain in body weight

The field efficacy and safety of a single-dose inactivated Mycoplasma hyopneumoniae vaccine, Suvaxyn MH-One, was evaluated in 4-5-day-old piglets on a commercial farm with a history of Mycoplasma disease in Southern Germany. The piglets were injected intramuscularly with the vaccine or saline (control group) and raised under commercial conditions to slaughter weight. The efficacy of the vaccine was determined by comparing the lung lesions associated with infection by M. hyopneumoniae in control and vaccinated pigs post mortem. In this analysis the vaccinated pigs had the lower mean percentage lung lesion at 5% compared to 9% in controls. Of the vaccinated pigs 52.3% were shown to have low levels of lung lesions between 0% and 5% and no more than 5.4% were shown to have levels above 20%. In contrast, the pigs administered saline showed 36.5% in the lower category (0-5%), while 18.3% showed lesions greater than 20%. There were significant differences in the mean body weight of pigs at the final two weight measurements at approximately 21 weeks and 26 weeks of age, with those receiving Suvaxyn MH-One being on average 5 kg heavier at each time point. There was also a significant increase in average daily gain in the vaccinated animals compared to the control group, particularly in the period from vaccination to the final two body weight measurements on day 138 and 166, from weaning at day 28 to the final two body measurements and from mid-way during finishing at day 84 to the final two body weight measurements. Vaccination had no adverse impact on appetite, although small numbers of vaccinated and control pigs did show mild signs of coughing, sneezing, respiratory distress or depression. There was no adverse impact on rectal temperatures and no signs of injection site reactions during the course of the study. We can conclude that vaccination with Suvaxyn MH-One to pigs at less than 1 week of age is effective in reducing lung lesions resulting from M. hyopneumoniae and also aids growth performance by reducing weight losses and improving average daily gain.

Evaluation of three experimental bovine viral diarrhea virus killed vaccines adjuvanted with combinations of Quil A cholesterol and dimethyldioctadecylammonium (DDA) bromide

Bovine viral diarrhea virus (BVDV) infections cause respiratory, reproductive, and enteric disease in cattle. Vaccination raises herd resistance and limits the spread of BVDV among cattle. Both killed and modified live vaccines against BVDV are available. While modified live vaccines elicit an immune response with a broader range and a longer duration of immunity, killed vaccines are considered to be safer. One way to improve the performance of killed vaccines is to develop new adjuvants. The goal of this research was evaluate new adjuvants, consisting of combinations of Quil A cholesterol and dimethyldioctadecylammonium (DDA) bromide, for use in killed vaccines. Responses to three novel killed vaccines, using combinations of Quil A and DDA as adjuvants, were compared to responses to a commercial modified live and a commercial killed vaccine. Vaccination response was monitored by measuring viral neutralizing antibodies (VN) levels and by response to challenge. All three novel vaccines were efficacious based on reduction in virus isolation, pyrexia, and depression. Compared to a commercial killed vaccine, the three novel vaccines elicited higher VN levels and reduced injection site inflammation.