Role of bovine respiratory syncytial virus in etiology of respiratory diseases on milk farms

Bovine respiratory syncytial virus (BRSV) is one of the etiological agents of respiratory diseases. The agent spreads widely in all the countries with intensive livestock farming and can cause pathologic changes in respiratory system either alone or in combination with other viruses and bacteria. It is a matter of crucial importance to study spread of the agent on large milk farms, to detect it in the internal organs of infected animals, and to quantify virus accumulation in them. The purpose of the research was to study peculiarities of RS infection spread, frequency of the virus detection in biomaterial samples (both alone and in associations with infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea/mucosal disease viruses (BVDV) and with Pasteurellaceae bacteria) on large milk farms affected by respiratory animal diseases; and to determine virus concentration in the respiratory organs. BRSV alone was reported in 9.2% of the tested biomaterial samples, as associated with IBR and BVDV it was reported in 1.4% and 5.2% of samples, correspondingly. The number of samples containing simultaneously BRSV and Pasteurellaceae bacteria was 10.8%. The virus was reported in a maximum of 26.6% of the tested samples. With the help of real-time PCR the virus genome was detected in lungs (13.1%), in exudate from trachea, bronchi and nasal sinuses (6.0%), in nasal discharge (4.0%) and in bronchi (1.7%). The virus was seldom detected in trachea and bronchial mucosa (1.1%) and in pulmonary lymph nodes (0.8%). Quantification of BRSV RNA demonstrated that maximum virus accumulation was observed in lungs and nasal charges and it confirms data on its tropism to pulmonary interstitium.

Differential Response of Mycorrhizal Plants to Tomato bushy stunt virus and Tomato mosaic virus Infection

Tomato bushy stunt virus (TBSV) and Tomato mosaic virus (ToMV) are important economic pathogens in tomato fields. Rhizoglomus irregulare is a species of arbuscular mycorrhizal (AM) fungus that provides nutrients to host plants. To understand the effect of R. irregulare on the infection by TBSV/ToMV in tomato plants, in a completely randomized design, five treatments, including uninfected control plants without AM fungi (C), uninfected control plants with AM fungi (M) TBSV/ToMV-infected plants without AM fungi (V), TBSV/ToMV-infected plants before mycorrhiza (VM) inoculation, and inoculated plants with mycorrhiza before TBSV/ToMV infection (MV), were studied. Factors including viral RNA accumulation and expression of Pathogenesis Related proteins (PR) coding genes including PR1, PR2, and PR3 in the young leaves were measured. For TBSV, a lower level of virus accumulation and a higher expression of PR genes in MV plants were observed compared to V and VM plants. In contrast, for ToMV, a higher level of virus accumulation and a lower expression of PR genes in MV plants were observed as compared to V and VM plants. These results indicated that mycorrhizal symbiosis reduces or increases the viral accumulation possibly via the regulation of PR genes in tomato plants.

HDAC6 regulates antibody-dependent intracellular neutralization of viruses via deacetylation of TRIM21

Tripartite motif–containing protein 21 (TRIM21) is a cytosolic antibody receptor that targets the internalized virus–antibody complex to the proteasome for degradation. However, the precise mechanism regulating TRIM21 activity is unknown. Here we show that TRIM21 is a substrate of histone deacetylase 6 (HDAC6) and that its function is regulated by acetylation. HDAC6 interacts with TRIM21 through its PRYSPRY motif and deacetylates TRIM21 at lysine 385 and lysine 387, thus promoting its homodimerization. Inhibiting HDAC6 activity increases TRIM21 acetylation, and hyperacetylation blocks TRIM21 dimerization and ubiquitination, preventing its binding to the virus–antibody complex and its degradation via the ubiquitin–proteasome pathway. HDAC6 depletion or inhibition increases virus accumulation in cells, indicative of an impaired capacity for antibody-dependent intracellular neutralization of viruses, whereas TRIM21 acetylation-deficient K385/387R mutant rescues HDAC6 depletion–caused ADIN impairment. These findings provide evidence for HDAC6 as a novel regulator of TRIM21-mediated intracellular innate immunity.

Low Frequency of Horizontal and Vertical Transmission of Cucurbit Leaf Crumple Virus in Whitefly Bemisia tabaci Gennadius

Cucurbit leaf crumple virus (CuLCrV), a bipartite begomovirus, is transmitted by whiteflies in a persistent and circulative manner. Like other begomoviruses, CuLCrV transmission via feeding is well understood; however, whether and how CuLCrV is transmitted by horizontal and vertical modes in its vector, Bemisia tabaci, remains unexplored. We studied transovarial and mating transmission of CuLCrV, and comparatively analyzed virus accumulation in whiteflies through feeding and nonfeeding modes. Furthermore, we quantified CuLCrV DNA A accumulation at different time points to determine whether this virus propagates in whiteflies. CuLCrV DNA A was transmitted vertically and horizontally by B. tabaci, with low frequency in each case. Transovarial transmission of CuLCrV DNA A was only 3.93% in nymphs and 3.09% in adults. Similarly, only a single viruliferous male was able to transmit CuLCrV DNA A to its nonviruliferous female counterparts via mating. In contrast, viruliferous females were unable to transmit CuLCrV DNA A to nonviruliferous males. Additionally, the recipient adults that presumably acquired CuLCrV transovarially and via mating were not able to transmit the virus to squash plants. We further report that the CuLCrV DNA A viral copy numbers were significantly lower in nonfeeding modes of transmission than in feeding ones. The viral copy numbers significantly decreased at succeeding time points throughout adulthood, suggesting no CuLCrV propagation in B. tabaci. Altogether, the low frequency of nonfeeding transmission, reduced virus accumulation in whiteflies, and absence of plant infectivity through nonfeeding transmission suggest that transovarial and mating CuLCrV transmission might not substantially contribute to CuLCrV epidemics.

Multiple ER-to-nucleus stress signaling pathways become active during Plantago asiatica mosaic virus and Turnip mosaic virus infection in Arabidopsis thaliana

SummaryEndoplasmic reticulum (ER) stress due to biotic or abiotic stress activates the unfolded protein response (UPR) to restore ER homeostasis. The UPR relies on multiple ER-to-nucleus signaling factors which mainly induce the expression of cytoprotective ER-chaperones. The inositol requiring enzyme (IRE1) along with its splicing target, bZIP60, restrict potyvirus, and potexvirus accumulation. Until now, the involvement of the alternative UPR pathways and the role of UPR to limit virus accumulation have remained elusive. Here, we used the Plantago asiatica mosaic virus (PlAMV) and the Turnip mosaic virus (TuMV) to demonstrate that the potexvirus triple gene block 3 (TGB3) protein and the potyvirus 6K2 protein activate the bZIP17, bZIP28, bZIP60, BAG7, NAC089 and NAC103 signaling in Arabidopsis thaliana. Using the corresponding knock-out mutant lines, we demonstrated that these factors differentially restrict local and systemic virus accumulation. We show that bZIP17, bZIP60, BAG7, and NAC089 are factors in PlAMV infection, whereas bZIP28 and bZIP60 are factors in TuMV infection. TGB3 and 6K2 transient expression in leave reveal that these alternative pathways induce BiPs expression. Finally, using dithiothreitol (DTT) and tauroursodeoxycholic acid (TUDCA) treatment, we demonstrated that the protein folding capacity significantly influences PlAMV accumulation. Together, these results indicate that multiple ER-to-nucleus signaling pathways are activated during virus infection and restrict virus accumulation through increasing protein folding capacity.Significance statementThe IRE1/bZIP60 pathway of unfolded protein response (UPR) is activated by potyviruses and potexviruses, limiting their infection, but the role of alternative UPR pathways is unknown. This study reveals the activation of multiple ER-to-nucleus signaling pathways by the Plantago asiatica mosaic virus and the Turnip mosaic virus. We identify additional signaling pathways serve to restrict virus accumulation through increased protein folding capacity.