Among six human coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle-East respiratory syndrome coronavirus (MERSCoV) are connected with severe respiratory-tract infection, which lead to high case-fatality rates of ~10 and ~35%, respectively. The papain-like protease, a domain located in the middle part of the largest non-structural protein Nsp3, has proteolytic, deubiquitinating, and deISGylating activities. The latter two functions are involved in the suppression of the antiviral innate immune response of the host cell. In this issue, Lei and Hilgenfeld present the X-ray crystal structure of a complex between MERS-CoV PLpro and human ubiquitin (Ub) that is devoid of any covalent linkage between the two proteins. The cover shows five regions of the PLpro bind to two areas of the Ub. See page 288-299 for details.
Emerging infectious diseases are major threats to human health. Most severe viral disease
outbreaks occur in developing regions where health conditions are poor. With increased
international travel and business, the possibility of eventually transmitting infectious viruses
between different countries is increasing. The most effective approach in preventing viral diseases
is vaccination. However, vaccines are not currently available for numerous viral diseases. Viruslike
particles (VLPs) are engineered vaccine candidates that have been studied for decades. VLPs
are constructed by viral protein expression in various expression systems that promote the selfassembly
of proteins into structures resembling virus particles. VLPs have antigenicity similar to
that of the native virus, but are non-infectious as they lack key viral genetic material. VLP vaccines
have attracted considerable research interest because they offer several advantages over
traditional vaccines. Studies have shown that VLP vaccines can stimulate both humoral and
cellular immune responses, which may offer effective antiviral protection. Here we review recent
developments with VLP-based vaccines for several highly virulent emerging or re-emerging
infectious diseases. The infectious agents discussed include RNA viruses from different virus
families, such as the Arenaviridae, Bunyaviridae, Caliciviridae, Coronaviridae, Filoviridae,
Flaviviridae, Orthomyxoviridae, Paramyxoviridae, and Togaviridae families.
Jian Lei, Rolf Hilgenfeld. Structural and mutational analysis of the interaction between the Middle-East respiratory syndrome coronavirus (MERS-CoV) papain-like protease and human ubiquitin[J]. Virologica Sinica, 2016, 31(4): 288-299. doi: 10.1007/s12250-016-3742-4.
The papain-like protease (PLpro) of Middle-East respiratory syndrome coronavirus (MERS-CoV) has proteolytic, deubiquitinating, and deISGylating activities. The latter two are involved in the suppression of the antiviral innate immune response of the host cell. To contribute to an understanding of this process, we present here the X-ray crystal structure of a complex between MERS-CoV PLpro and human ubiquitin (Ub) that is devoid of any covalent linkage between the two proteins. Five regions of the PLpro bind to two areas of the Ub. The C-terminal five residues of Ub, RLRGG, are similar to the P5–P1 residues of the polyprotein substrates of the PLpro and are responsible for the major part of the interaction between the two macromolecules. Through sitedirected mutagenesis, we demonstrate that conserved Asp165 and non-conserved Asp164 are important for the catalytic activities of MERS-CoV PLpro. The enzyme appears not to be optimized for catalytic efficiency; thus, replacement of Phe269 by Tyr leads to increased peptidolytic and deubiquitinating activities. Ubiquitin binding by MERS-CoV PLpro involves remarkable differences compared to the corresponding complex with SARS-CoV PLpro. The structure and the mutational study help understand common and unique features of the deubiquitinating activity of MERS-CoV PLpro.
Aquareovirus species vary with respect to pathogenicity, and the nonstructural protein NS80 of aquareoviruses has been implicated in the regulation of viral replication and assembly, which can form viral inclusion bodies (VIBs) and recruit viral proteins to its VIBs in infected cells. NS80 consists of 742 amino acids with a molecular weight of approximately 80 kDa. Interestingly, a short specific fragment of NS80 has also been detected in infected cells. In this study, an approximately 58-kDa product of NS80 was confirmed in various infected and transfected cells by immunoblotting analyses using α-NS80C. Mutational analysis and time course expression assays indicated that the accumulation of the 58-kDa fragment was related to time and infection dose, suggesting that the fragment is not a transient intermediate of protein degradation. Moreover, another smaller fragment with a molecular mass of approximately 22 kDa was observed in transfected and infected cells by immunoblotting with a specific anti-FLAG monoclonal antibody or α-NS80N, indicating that the 58- kDa polypeptide is derived from a specific cleavage site near the amino terminus of NS80. Additionally, different subcellular localization patterns were observed for the 22-kDa and 58-kDa fragments in an immunofluorescence analysis, implying that the two cleavage fragments of NS80 function differently in the viral life cycle. These results provide a basis for additional studies of the role of NS80 played in replication and particle assembly of the Aquareovirus.
Aquareovirus species vary with respect to pathogenicity, and the nonstructural protein NS80 of aquareoviruses has been implicated in the regulation of viral replication and assembly, which can form viral inclusion bodies (VIBs) and recruit viral proteins to its VIBs in infected cells. NS80 consists of 742 amino acids with a molecular weight of approximately 80 kDa. Interestingly, a short specific fragment of NS80 has also been detected in infected cells. In this study, an approximately 58-kDa product of NS80 was confirmed in various infected and transfected cells by immunoblotting analyses using α-NS80C. Mutational analysis and time course expression assays indicated that the accumulation of the 58-kDa fragment was related to time and infection dose, suggesting that the fragment is not a transient intermediate of protein degradation. Moreover, another smaller fragment with a molecular mass of approximately 22 kDa was observed in transfected and infected cells by immunoblotting with a specific anti-FLAG monoclonal antibody or α-NS80N, indicating that the 58-kDa polypeptide is derived from a specific cleavage site near the amino terminus of NS80. Additionally, different subcellular localization patterns were observed for the 22-kDa and 58-kDa fragments in an immunofluorescence analysis, implying that the two cleavage fragments of NS80 function differently in the viral life cycle. These results provide a basis for additional studies of the role of NS80 played in replication and particle assembly of the Aquareovirus.
Hedi Zhou, Bryan Eaton, Zhihong Hu, Basil Arif. Accidental discovery and isolation of Zika virus in Uganda and the relentless epidemiologist behind the investigations[J]. Virologica Sinica, 2016, 31(4): 357-361. doi: 10.1007/s12250-016-3821-6.
Zika virus (ZIKV) has captured the attention of the world because of its potential to infect neural cells and its teratogenic effects on foetuses and the new born. The virus seems to have various modes of transmission and has been the subject of many reviews in the literature (example, Musso and Gubler, 2016, Wang et al., 2016). ZIKV was first isolated in 1947 but remained almost innocuous causing few and sporadic mild infections until 60 years later when an outbreak occurred in YAP State in the Federal State of Micronesia in 2007 infecting nearly 75% of the population (Duffy et al., 2009; Ai et al., 2016). A few years later (2013– 2014), there was an epidemic in the islands of French Polynesia located about half way between Mexico and Australia. Almost concomitantly, minor outbreaks occurred in other isolated Pacific islands such as Cook Islands, Samoa, Fiji and New Caledonia. It is truly remarkable how the virus has spread within a short time to these seemingly isolated islands. However, nothing brought ZIKV to the attention of the world more than the horrific images of newborn babies with microcephaly in north eastern Brazil (Adibi et al., 2016, Rubin et al., 2016; Schuler-Faccini et al., 2016). These images were the impetus for concerted efforts to study viral tropism and to put into motion efforts to combat its spread. The World Health Organization has deemed ZIKV a “public health emergency of international concern” (Cohn J, 2016). The purpose of this manuscript is to review the very early research that led to the discovery and partial characterization of the virus along with some current thoughts and add few personal anecdotes about the scientist who discovered it.