Classical swine fever (CSF) remains one of the most important transboundary viral diseases of swine worldwide. The causative agent is CSF virus, a small, enveloped RNA virus of the genus Pestivirus. Based on partial sequences, three genotypes can be distinguished that do not, however, directly correlate with virulence. Depending on both virus and host factors, a wide range of clinical syndromes can be observed and thus, laboratory confirmation is mandatory. To this means, both direct and indirect methods are utilized with an increasing degree of commercialization. Both infections in domestic pigs and wild boar are of great relevance; and wild boars are a reservoir host transmitting the virus sporadically also to pig farms. Control strategies for epidemic outbreaks in free countries are mainly based on classical intervention measures; i.e., quarantine and strict culling of affected herds. In these countries, vaccination is only an emergency option. However, live vaccines are used for controlling the disease in endemically infected regions in Asia, Eastern Europe, the Americas, and some African countries. Here, we will provide a concise, updated review on virus properties, clinical signs and pathology, epidemiology, pathogenesis and immune responses, diagnosis and vaccination possibilities.

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Classical Swine Fever-An Updated Review.

Porcine reproductive and respiratory syndrome virus (PRRSV), one of the most economically significant pathogens worldwide, has caused numerous outbreaks during the past 30 years. PRRSV infection causes reproductive failure in sows and respiratory disease in growing and finishing pigs, leading to huge economic losses for the swine industry. This impact has become even more significant with the recent emergence of highly pathogenic PRRSV strains from China, further exacerbating global food security. Since new PRRSV variants are constantly emerging from outbreaks, current strategies for controlling PRRSV have been largely inadequate, even though our understanding of PRRSV virology, evolution and host immune response has been rapidly expanding. Meanwhile, practical experience has revealed numerous safety and efficacy concerns for currently licensed vaccines, such as shedding of modified live virus (MLV), reversion to virulence, recombination between field strains and MLV and failure to elicit protective immunity against heterogeneous virus. Therefore, an effective vaccine against PRRSV infection is urgently needed. Here, we systematically review recent advances in PRRSV vaccine development. Antigenic variations resulting from PRRSV evolution, identification of neutralizing epitopes for heterogeneous isolates, broad neutralizing antibodies against PRRSV, chimeric virus generated by reverse genetics, and novel PRRSV strains with interferon-inducing phenotype will be discussed in detail. Moreover, techniques that could potentially transform current MLV vaccines into a superior vaccine will receive special emphasis, as will new insights for future PRRSV vaccine development. Ultimately, improved PRRSV vaccines may overcome the disadvantages of current vaccines and minimize the PRRS impact to the swine industry.

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Improved Vaccine against PRRSV: Current Progress and Future Perspective.

Porcine circovirus 2 (PCV-2) is one of the most widespread viral infections of swine, causing a remarkable economic impact because of direct losses and indirect costs for its control. As other ssDNA viruses, PCV-2 is characterized by a high evolutionary rate, leading to the emergence of a plethora of variants with different biological and epidemiological features. Over time, several attempts have been made to organize PCV-2 genetic heterogeneity in recognized genotypes. This categorization has clearly simplified the epidemiological investigations, allowing to identify different spatial and temporal patterns among genotypes. Additionally, variable virulence and vaccine effectiveness have also been hypothesized. However, the rapid increase in sequencing activity, coupled with the per se high viral variability, has challenged the previously established nomenclature, leading to the definition of several study-specific genotypes and hindering the capability of performing comparable epidemiological studies. Based on these premises, an updated classification scheme is herein reported. Recognizing the impossibility of defining a clear inter-cluster p-distance cut-off, the present study proposes a phylogeny-grounded genotype definition based on three criteria: maximum intra-genotype p-distance of 13% (calculated on the ORF2 gene), bootstrap support at the corresponding internal node higher than 70% and at least 15 available sequences. This scheme allowed defining 8 genotypes (PCV-2a to PCV-2h), which six of those had been previously proposed. To minimize the inconvenience of implementing a new classification, the most common names already adopted have been maintained when possible. The analysis of sequence-associated metadata highlighted a highly unbalanced sequencing activity in terms of geographical, host and temporal distribution. The PCV-2 molecular epidemiology scenario appears therefore characterized by a severe bias that could lead to spurious associations between genetic and epidemiological/biological viral features. While the suggested classification can establish a "common language" for future studies, further efforts should be paid to achieve a more homogeneous and informative representation of the PCV-2 global scenario.

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Porcine circovirus 2 (PCV-2) genotype update and proposal of a new genotyping methodology.

Antiviral Strategies against PRRSV Infection

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) causes severe outbreaks in swine leading to serious economic losses in swine industry in Thailand and other countries in Southeast Asia. However, information regarding whole genome characterization of HP-PRRSV isolate in this region is limited. This report describes sequencing and characterizations of the complete nucleotide sequence of a Thai HP-PRRSV isolate, designated HP/Thailand/19500LL/2010 (TH19500LL/10). The complete genomic sequence consists of 189-nt 5UTR, 14,982-nt protein-coding region containing 9 ORFs and 150-nt 3UTR. In addition, the full-length sequence of Thai HP-PRRSV isolate was compared with that of VR2332 and other HP-PRRSV strains. The genomic sequence of TH19500LL/10 is highly similar to that of BH58/10 isolate, a HP-PRRSV from Laos. Nsp2 of TH19500LL/10 has common 30-amino acid discontinuous deletions. Amino acid comparison showed that GP5 of Thai HP-PRRSV was completely identical to that of other HP-PRRSV including JN-HS, BB0907, 09HEN2 and BH58/10 strains. It shares 98.5% and 89.1% similarity at amino acid level to that of the HP-PRRSV prototype (JXA1) and classical NA prototype (VR2332), respectively. In addition, in silico functional analysis of structural proteins of TH19500LL/10 was also performed and discussed. This study provides basic knowledge for further studies of HP-PRRSV related to molecular mechanisms of viral infection and pathogenesis.

Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus

ABSTRACT Since commencement of COVID-19 pandemic, several SARS-CoV-2 variants have emerged amid containment efforts via vaccination. The Delta variant (B.1.617.2), discovered in October 2020, was designated as a VOC by the WHO on May 11, 2021. The enhanced transmissibility of Delta variant has been associated with critical mutations such as D614G, L452R, P681R, and T478K in the S-protein. The increased affinity of the S-protein and ACE2 has been postulated as a key reason for decreased vaccine efficacy. As per evidence, the Delta variant possesses increased transmissibility and decreased vaccine efficacy compared to other VOCs like Alpha and Beta. This has led to concerns regarding the acquisition of novel mutations in the Delta variant and outbreaks in vulnerable communities, including vaccinated people. In this mini-review of Delta variant, we have explained its evolution and characteristics, the impact of spike mutations on infectivity and immune evasion, and measures to combat future outbreaks.

https://www.tandfonline.com/doi/pdf/10.1080/21645515.2022.2068883?needAccess=true

Delta variant (B.1.617.2) of SARS-CoV-2: Mutations, impact, challenges and possible solutions

Background: Porcine reproductive and respiratory syndrome (PRRS) is an economically important viral disease of pigs worldwide. India has reported the first outbreak of PRRS in the pig population of Mizoram state to the Office International des Epizooties on the 26 June 2013.Hypothesis/Objectives: The aim of the present study was to determine the genotype and origin of porcine reproductive and respiratory syndrome virus (PRRSV) from the first outbreak in the pig population of Mizoram state, India, in 2013.Animals and methods: A total of 880 affected pigs from the outbreak were clinically examined, 51 animals were necropsied and tested by reverse transcription polymerase chain reaction (RT-PCR) to detect PRRSV and 148 serum samples were tested to detect PRRSV-specific antibodies. The full open reading frame 5 (ORF5) gene sequences from 12 and ORF7 gene sequences from three clinical cases were sequenced and analysed for genomic characterization, respectively.Results: The outbreak was confirmed by the detecti...

https://www.tandfonline.com/doi/pdf/10.1080/01652176.2015.1066043

Porcine reproductive and respiratory syndrome virus (PRRSV) from the first outbreak of India shows close relationship with the highly pathogenic variant of China.

Genetic characterisation and phylogenetic analysis of PCV2 isolates from India: Indications for emergence of natural inter-genotypic recombinants

Background: Limited studies are available on molecular epidemiology of classical swine fever virus (CSFV) in India and are restricted to domestic pigs. These studies show the presence of 1.1. genotype.Hypothesis/objectives: The aim of the present study was to subgenotype four CSFV isolates, two each from the outbreaks of CSF in wild (Sus scrofa) and domestic pigs of Mizoram state, India, in 2011.Animals and methods: CSFV isolates were subjected to nucleotide sequencing in E2 and NS5B genomic regions. Phylogenetic analysis of the isolates in both genomic regions was carried out with 39 Indian isolates (4 isolates from the present study of Mizoram state and 35 isolates from the other states of India) and 57 reference sequences retrieved from the GenBank database. Two of the 39 isolates from India were collected from wild boar and were subgenotyped as 2.1. Out of 37 isolates from domestic pigs, only two were subgenotyped as 2.1.Results: The analysis revealed the emergence of 2.1. subgenotype of CSFV in both ...

Emergence of 2.1. subgenotype of classical swine fever virus in pig population of India in 2011.

Since its first outbreak in 2013, porcine reproductive and respiratory syndrome (PRRS) has established as an enzootic disease in pig population of Mizoram state, India. Our previous studies based on phylogenetic analysis of ORF5 and ORF7 gene sequences revealed close relationship of Indian PRRSV with the highly pathogenic variant of PRRSV (HP-PRRSV) of Chinese origin. Despite the control measures, second major outbreak of the disease was recorded in Aizawl district of Mizoram in 2015. The objective of the present study was to examine the origin of PRRSV isolates of 2015 outbreak, identification of deleted region in Nsp2 gene and determination of any genetic variation between 2013 and 2015 isolates of PRRSV. The outbreak was confirmed by the detection of PRRSV-specific antibodies in 57 out of 92 serum samples (61.96 %) and also by RT-PCR in 42 out of 42 necropsy samples (100 %). Nucleotide sequence analysis of Nsp2 coding region of Indian isolates and comparison with reference sequences revealed 90 nucleotides discontinuous deletion further establishes the closeness of Indian PRRSV to Chinese HP-PRRSV. Further, sequence and phylogenetic analysis of ORF5, ORF7 and Nsp2 genes of Indian PRRSV from both 2013 and 2015 revealed that the outbreaks were caused by two different strains of HP-PRRSV closely associated with the Chinese 10 HEB-3 isolate and 07QN isolates of Vietnam origin respectively. The present study confirms that the Indian PRRSV is a highly pathogenic variant of PRRSV and this study serves as the basis for developing practical and effective control measures against this disease.

T.K. Rajkhowa

Papers

Delta variant (B.1.617.2) of SARS-CoV-2: Mutations, impact, challenges and possible solutions

Porcine reproductive and respiratory syndrome virus (PRRSV) from the first outbreak of India shows close relationship with the highly pathogenic variant of China.

Genetic characterisation and phylogenetic analysis of PCV2 isolates from India: Indications for emergence of natural inter-genotypic recombinants

Emergence of 2.1. subgenotype of classical swine fever virus in pig population of India in 2011.

Indian porcine reproductive and respiratory syndrome virus bears discontinuous deletion of 30 amino acids in nonstructural protein 2