The interaction between the Nipah virus nucleocapsid protein and phosphoprotein regulates virus replication.

Continued outbreaks of Henipaviruses in South Asia and Australia cause severe and lethal disease in both humans and animals. Together, with evidence of human to human transmission for Nipah virus and the lack of preventative or therapeutic measures, its threat to cause a widespread outbreak and its potential for weaponization has increased. In this study we demonstrate how overexpression of the Nipah virus nucleocapsid protein regulates viral polymerase activity and viral RNA production. By overexpressing the Nipah virus nucleocapsid protein in trans viral transcription was inhibited; however, an increase in viral genome synthesis was observed. Together, the bias of polymerase activity towards genome production led to the severe inhibition of viral progeny. We identified two domains within the nucleocapsid protein, which were each independently capable of binding the viral phosphoprotein. Evident by our data, we propose that the nucleocapsid protein's ability to interact with the phosphoprotein of the polymerase complex causes a change in polymerase activity and subsequent deficiency in viral replication. This study not only provides insights into the dynamics of Henipavirus RNA synthesis and replication, but also provides insight into potential targets for antiviral drug development.

Acute BVDV-2 infection in beef calves delays humoral responses to a non-infectious antigen challenge.

Immunosuppressive effects of an intranasal challenge with non-cytopathic bovine viral diarrhea virus (BVDV) 2a (strain 1373) were assessed through acquired and innate immune system responses to ovalbumin (OVA). Concurrent BVDV infection was hypothesized to delay and reduce the humoral response to ovalbumin (administered on days 3 and 15 post-inoculation). Infected animals followed the expected clinical course. BVDV titers, and anti-BVDV antibodies confirmed the course of infection and were not affected by the administration of OVA. Both the T-helper (CD4(+)) and B-cell (CD20(+)) compartments were significantly (P < 0.05) reduced in infected animals, while the gamma-delta T-cell population (Workshop cluster 1+, WC1(+)) decreased slightly in numbers. Infection with BVDV delayed the increase in OVA IgG by approximately 3 d from day 12 through day 21 post-inoculation. Between days 25 and 37 post-inoculation following BVDV infection the IgM concentration in the BVDV- group decreased while the OVA IgM titer still was rising in the BVDV+ animals. Thus, active BVDV infection delays IgM and IgG responses to a novel, non-infectious antigen.

Une infection aiguë par le BVDV-2 chez les veaux retarde les réponses humorales face à un test à l'aide d'un antigène non infectieux. Les effets immunosuppressifs d'une inoculation défin intranasale à l'aide du virus non cytopathogène de la diarrhée virale bovine (VBVD) 2a (souche 1373) ont été évalués par les réactions acquises et innées du système immunitaire à l'ovalbumine (OVA). On a émis l'hypothèse que l'infection concomitante par le VBVD retardait et réduisait la réaction humorale à l'ovalbumine (administrée aux jours 3 et 15 après l'inoculation). Les animaux infectés ont suivi le cheminement clinique prévu. Les titres de BVDV et les anticorps anti-BVDV ont confirmé le déroulement de l'infection et ils n'ont pas été affectés par l'administration d'OVA. Les compartiments des lymphocytes T auxiliaires (CD4+) et des cellules B (CD20+) étaient significativement réduits (P < 0,05) chez les animaux infectés, tandis que la numération de la population de cellules T gamma-delta (WC1+) a diminué légèrement. L'infection par le VBVD a retardé l'augmentation de l'OVA IgG d'environ 3 jours, à compter du jour 12 jusqu'au jour 21 après l'inoculation. Entre les jours 25 et 37 après l'inoculation suivant l'infection par le BVDV, la concentration d'IgM dans le groupe VBVD a diminué tandis que le titre d'OVA IgM augmentait toujours chez les animaux positifs pour le VBVD. Par conséquent, l'infection active par le VBVD retarde les réactions IgM et IgG face à un antigène non infectieux nouveau.(Traduit par Isabelle Vallières).

Porcine circovirus-2 capsid protein induces cell death in PK15 cells.

Studies have shown that Porcine circovirus (PCV)-2 induces apoptosis in PK15 cells. Here we report that cell death is induced in PCV2b-infected PK15 cells that express Capsid (Cap) protein and this effect is enhanced in interferon gamma (IFN-γ)-treated cells. We further show that transient PCV2a and 2b-Cap protein expression induces cell death in PK15 cells at rate similar to PCV2 infection, regardless of Cap protein localization. These data suggest that Cap protein may have the capacity to trigger different signaling pathways involved in cell death. Although further investigation is needed to gain deeper insights into the nature of the pathways involved in Cap-induced cell death, this study provides evidence that PCV2-induced cell death in kidney epithelial PK15 cells can be mapped to the Cap protein and establishes the need for future research regarding the role of Cap-induced cell death in PCV2 pathogenesis.

Cytotoxicity of ORF3 proteins from a nonpathogenic and a pathogenic porcine circovirus.

Porcine circovirus type 2 (PCV2) infection is associated with significant and serious swine diseases worldwide, while PCV1 appears to be a nonpathogenic virus. Previous studies demonstrated that the ORF3 protein of PCV2 (PCV2ORF3) was involved in PCV2 pathogenesis via its proapoptotic capability (J. Liu, I. Chen, Q. Du, H. Chua, and J. Kwang, J. Virol. 80:5065-5073, 2006). If PCV2ORF3-induced apoptosis is a determinant of virulence, PCV1ORF3 is hypothesized to lack this ability. The properties of PCV1 and PCV2 ORF3, expressed as fusion proteins to an enhanced green fluorescent protein (eGFP), were characterized with regard to their ability to cause cellular morphological changes, detachment, death, and apoptosis. PCV1ORF3 significantly induced more apoptotic cell death and was toxic to more different cell types than PCV2ORF3 was. PCV1ORF3-associated cell death was caspase dependent. PCV1ORF3 also induced poly(ADP-ribose) polymerase 1 (PARP) cleavage; however, whether PARP was involved in cell death requires further studies. Truncation of PCV1 and elongation of PCV2 ORF3 proteins revealed that the first 104 amino acids contain a domain capable of inducing cell death, whereas the C terminus of PCV1ORF3 contains a domain possibly responsible for enhancing cell death. These results suggest that the pathogenicity of PCV2 for pigs is either not determined or not solely determined by the ORF3 protein.

Genomic analysis of porcine circovirus type-2 isolates in Alberta pigs demonstrating clinical porcine circovirus associated disease (PCVAD).

Nineteen pigs with clinical signs of porcine circovirus associated diseases (PCVAD) on 5 Alberta pig farms were examined pathologically, including gross pathology, histopathology, and immunohistochemistry. Polymerase chain reaction (PCR) for porcine circovirus type-2 (PCV-2) and sequence analysis was performed on tissue samples of 12 animals. Results showed that new strains of porcine circovirus type-2 genogroup b were present in most pigs that were positive for PCV-2. Furthermore, a mixed infection with PCV-2a and PCV-2b occurred in the liver and lungs of 1 pig. Comparison of whole genome sequences representing known viruses and the newly discovered Alberta viruses revealed mutations distributed over the entire genome of PCV-2; however, sequences encoding for immunodominant epitopes of PCV-2 appear to be unaffected by these mutations.