.The establishment of an arterivirus family acknowledgesthemanyuniquebiologicalandmolecularpropertiesofitsfourpresent members. On the other hand, the aﬃliation with thecoronavirusesrecognizesanintriguingancestralrelationshipatthelevelofgenomeorganizationandreplication.ThegenomesequencesofEAV,PRRSV,LDVandSHFVwereinstrumentalin uniting and reclassifying the arteriviruses (den Boon

The molecular biology of arteriviruses.

In 1987, porcine reproductive and respiratory syndrome (PRRS) was recognized in the USA as a new disease of swine causing late-term reproductive failure and severe pneumonia in neonatal pigs. The syndrome is caused by an RNA virus referred to as PRRS virus (PRRSV), which is classified in the family Arteriviridae. Swine macrophages are the only indigenous cell type known to support PRRSV replication. Direct contact between infected and naive pigs is the predominant route of PRRSV transmission. Exposure of a mucosal surface to PRRSV leads to virus replication in regional macrophages, a prolonged viremia and systemic distribution of virus to other macrophage populations. Reproductive failure induced by PRRSV infection in late-gestation sows is characterized by premature farrowing of stillborn, partially autolyzed, and mummified fetuses. Pneumonia caused by PRRSV infection is more severe in young pigs compared to adults and may be complicated by concurrent bacterial infections. Gross lung lesions associated w...

https://journals.sagepub.com/doi/pdf/10.1177/030098589803500101

Porcine reproductive and respiratory syndrome

One hundred 4-week-old cesarean-derived colostrum-deprived pigs were inoculated with one of two different US porcine reproductive and respiratory syndrome virus (PRRSV) isolates (VR2385, VR2431) or the European Lelystad virus to detect and compare the location and amount of virus antigen. Interstitial pneumonia, myocarditis, lymphadenopathy, and encephalitis were consistently seen in all three groups; however, disease and lesions were more severe in the VR2385 group. Immunohistochemical evaluation of formalin-fixed tissues revealed virus antigen in alveolar macrophages in lungs of 22/25, 14/25, 14/25, and 0/25 of the VR2385, VR2431, Lelystad, and control pigs, respectively. Follicular macrophages and dendritic cells in the lymph nodes of 14/25, 10/25, 10/25, and 0/25 pigs from the VR2385, VR2431, Lelystad, and control groups, respectively, stained positive for virus antigen. Similar cells in the tonsils from 25/25, 21/25, 23/25, and 0/25 pigs from the VR2385, VR2431, Lelystad, and control groups, respectively, stained positive for virus antigen. Other tissues and cells in which virus antigen was detected included macrophages and endothelial cells in the heart, macrophages, and interdigitating cells in the thymus, macrophages and dendritic cells in the spleen and Peyer's patches, and macrophages in hepatic sinusoids, renal medullary interstitium, and adrenal gland. PRRSV persisted in macrophages in the lung, tonsil, lymph node, and spleen for at least 28 days. Significantly more PRRSV antigen was detected in the lung (P < 0.01), lymph nodes (P < or = 0.05), and tonsils (P < 0.05) of the VR2385 pigs than was detected in the same tissues of the VR2431 and Lelystad pigs. The cell types in which PRRSV antigen was detected and the distribution of PRRSV antigen-positive cells within particular tissues and organs were generally similar for the different virus inoculation groups despite differences in virulence of the isolates.

https://journals.sagepub.com/doi/pdf/10.1177/030098589503200606

Comparison of the Pathogenicity of Two US Porcine Reproductive and Respiratory Syndrome Virus Isolates with that of the Lelystad Virus

This review addresses important issues of porcine reproductive and respiratory syndrome virus (PRRSV) infection, immunity, pathogenesis, and control. Worldwide, PRRS is the most economically important infectious disease of pigs. We highlight the latest information on viral genome structure, pathogenic mechanisms, and host immunity, with a special focus on immune factors that modulate PRRSV infections during the acute and chronic/persistent disease phases. We address genetic control of host resistance and probe effects of PRRSV infection on reproductive traits. A major goal is to identify cellular/viral targets and pathways for designing more effective vaccines and therapeutics. Based on progress in viral reverse genetics, host transcriptomics and genomics, and vaccinology and adjuvant technologies, we have identified new areas for PRRS control and prevention. Finally, we highlight the gaps in our knowledge base and the need for advanced molecular and immune tools to stimulate PRRS research and field applications.

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): Pathogenesis and Interaction with the Immune System.

Porcine reproductive and respiratory syndrome virus (PRRSV) belongs to the recently recognized Arteriviridae family within the genus Arterivirus, order Nidovirales, which also includes equine arteritis virus (EAV), lactate dehydrogenase-elevating virus (LDV), and simian hemorrhagic fever virus (SHFV). Mature viral particles are composed of an envelope 50–72 nm in diameter, with an isometric core about 20–30 nm enclosing a linear positive-stranded RNA genome of approximately 15 kb. The virions are assembled by the budding of preformed nucleocapsids into the lumen of the smooth endoplasmic reticulum and/or Golgi apparatus. The mature virions are then released by exocytosis. The viral genome contains eight open reading frames (ORFs) which are transcribed in cells as a nested set of subgenomic mRNAs. The ORF1a and ORF1b situated at the 5′end of the genome represent nearly 75% of the viral genome and code for proteins with apparent replicase and polymerase activities. The major structural proteins consist of a 25 kDa envelope glycoprotein (GP5), an 18–19 kDa unglycosylated membrane protein (M), and a 15 kDa nucleocapsid (N) protein, encoded by ORFs 5, 6 and 7, respectively. The N protein is the more abundant protein of the virion and is highly antigenic, which therefore makes it a suitable candidate for the detection of virus-specific antibodies and diagnosis of the disease. Four to five domains of antigenic importance have been identified for the N protein, a common conformational antigenic site for European and North American strains being localized in the central region of the protein. In cells and virions, both M and GP5 occur in heterodimeric complexes linked by disulfide bonds. The expression products of ORFs 2 and 4 are also incorporated into virus particles as additional minor membrane-associated glycoproteins designated as GP2 and GP4, with Mr of 29 and 31 kDa, respectively. The structural nature of the ORF3 product, a highly glycosylated protein with an apparent Mr of 42 kDa, is still being debated, in view of the apparently conflicting data on its presence in virus particles. Nonetheless, the GP3 of North American and European strains has been shown to be antigenic, providing protection for piglets against PRRSV infection in the absence of a noticeable neutralizing humoral response. Pigs exposed to the native form of GP5 by means of DNA immunization develop specific neutralizing and protecting antibodies. The GP5 is involved in antigenic variability, apoptosis, and possibly antibody-dependent enhancement phenomena. The GP4 also possesses antigenic determinants that trigger the immune system to produce neutralizing antibodies. Each of the PRRSV structural proteins carries common and type-specific antigenic determinants that permit the ability to differentiate between European and North American strains. The potential use of the PRRSV structural proteins in subunit recombinant-type vaccines is also discussed.

/pdf/current-knowledge-on-the-structural-proteins-of-porcine-351x8nn29s.pdf

Current knowledge on the structural proteins of porcine reproductive and respiratory syndrome (PRRS) virus: comparison of the North American and European isolates.

Two different cell populations, high- (MARC-145) and low-permissive cell clones (L-1) to porcine reproductive and respiratory syndrome (PRRS) virus, were derived from MA-104 cell line (parent cell: P) by cell cloning. Maximum virus yields in MARC-145, P, and L-1 cell clones were 108.5, 103.5, and 102.5 tissue culture infective dose 50 (TCID50)/0.1 ml, respectively. The MARC-145 cell clone supported replication of all 11 different porcine reproductive and respiratory syndrome virus isolates that were tested. These results indicated that the MARC-145 cells will be useful for PRRS virus replication.

Enhanced replication of porcine reproductive and respiratory syndrome (PRRS) virus in a homogeneous subpopulation of MA-104 cell line

Mammals experience similar stages of embryonic development, birth, infancy, youth, adolescence, maturity, and senescence. While embryonic developmental processes have been extensively researched, many molecular mechanisms regulating the different life stages after birth, such as aging, remain unresolved. We investigated the conserved and global molecular transitions in transcriptional remodeling with age in dogs of 15 breeds, which revealed that genes underlying hormone level regulation and developmental programs were differentially regulated during aging. Subsequently, we show that the candidate genes associated with tumorigenesis also exhibit age-dependent DNA methylation patterns, which might have contributed to the tumor state through inhibiting the plasticity of cell differentiation processes during aging, and ultimately suggesting the molecular events that link the processes of aging and cancer. These results highlight that the rate of age-related transcriptional remodeling is influenced not only by the lifespan, but also by the timing of critical physiological milestones.

/pdf/genome-wide-integrative-transcriptional-profiling-identifies-24udju5h.pdf

Genome-Wide Integrative Transcriptional Profiling Identifies Age-Associated Signatures in Dogs

ABSTRACT Prolonged exposure to high temperatures is linked to a range of physiological responses in broiler chickens including reduced disease resistance, low growth rate, and high mortality rate. In this study, we investigated the effect of heat stress on gene expression levels in 4-week-old and 6-week-old chickens each exposed to environments conditioned at thermoneutral (21 °C) and high (32 °C) temperatures. The analysis of differentially expressed genes (DEGs) using microarray revealed that genes underlying reactive oxygen species (ROS) production, cell nutrient intake, glucose metabolism, and circadian rhythm were differentially regulated in association with heat stress. We also found that the deviation in expression levels across the transcriptome in response to heat stress was significantly stronger (P< 2.2×10−16) in 6-week-olds compared to younger chickens. We finally observed a significant trend (r = 0.78, P< 2.2×10−16) that genes with a higher estimate of expression in the microarray were more likely to have a higher expression level in RNA-sequencing. Together, our findings provide comprehensive insights into the physiology involved in stress responses at varying developmental stages, which may facilitate chicken breeding to maximize their productivity under adverse conditions.

https://www.tandfonline.com/doi/pdf/10.1080/19768354.2022.2059566?needAccess=true

H. S. Kim

Papers

Enhanced replication of porcine reproductive and respiratory syndrome (PRRS) virus in a homogeneous subpopulation of MA-104 cell line

Genome-Wide Integrative Transcriptional Profiling Identifies Age-Associated Signatures in Dogs

Characterization of differential gene expression of broiler chicken to thermal stress in discrete developmental stages