Carol Duffy

Characterization of a UL49-Null Mutant: VP22 of Herpes Simplex Virus Type 1 Facilitates Viral Spread in Cultured Cells and the Mouse Cornea

ABSTRACT Herpes simplex virus type 1 (HSV-1) virions, like those of all herpesviruses, contain a proteinaceous layer termed the tegument that lies between the nucleocapsid and viral envelope. The HSV-1 tegument is composed of at least 20 different viral proteins of various stoichiometries. VP22, the product of the UL49 gene, is one of the most abundant tegument proteins and is conserved among the alphaherpesviruses. Although a number of interesting biological properties have been attributed to VP22, its role in HSV-1 infection is not well understood. In the present study we have generated both a UL49-null virus and its genetic repair and characterized their growth in both cultured cells and the mouse cornea. While single-step growth analyses indicated that VP22 is dispensable for virus replication at high multiplicities of infection (MOIs), analyses of plaque morphology and intra- and extracellular multistep growth identified a role for VP22 in viral spread during HSV-1 infection at low MOIs. Specifically, VP22 was not required for either virion infectivity or cell-cell spread but was required for accumulation of extracellular virus to wild-type levels. We found that the absence of VP22 also affected virion composition. Intracellular virions generated by the UL49-null virus contained reduced amounts of ICP0 and glycoproteins E and D compared to those generated by the wild-type and UL49-repaired viruses. In addition, viral spread in the mouse cornea was significantly reduced upon infection with the UL49-null virus compared to infection with the wild-type and UL49-repaired viruses, identifying a role for VP22 in viral spread in vivo as well as in vitro.

VP22 of Herpes Simplex Virus 1 Promotes Protein Synthesis at Late Times in Infection and Accumulation of a Subset of Viral mRNAs at Early Times in Infection

ABSTRACT VP22, encoded by the UL49 gene, is one of the most abundant proteins of the herpes simplex virus 1 (HSV-1) tegument. In the present study we show VP22 is required for optimal protein synthesis at late times in infection. Specifically, in the absence of VP22, viral proteins accumulated to wild-type levels until ∼6 h postinfection. At that time, ongoing synthesis of most viral proteins dramatically decreased in the absence of VP22, whereas protein stability was not affected. Of the individual proteins we assayed, VP22 was required for optimal synthesis of the late viral proteins gE and gD and the immediate-early protein ICP0 but did not have discernible effects on accumulation of the immediate-early proteins ICP4 or ICP27. In addition, we found VP22 is required for the accumulation of a subset of mRNAs to wild-type levels at early, but not late, times in infection. Specifically, the presence of VP22 enhanced the accumulation of gE and gD mRNAs until ∼9 h postinfection, but it had no discernible effect at later times in infection. Also, VP22 did not significantly affect ICP0 mRNA at any time in infection. Thus, the protein synthesis and mRNA phenotypes observed with the UL49-null virus are separable with regard to both timing during infection and the genes affected and suggest separate roles for VP22 in enhancing the accumulation of viral proteins and mRNAs. Finally, we show that VP22s effects on protein synthesis and mRNA accumulation occur independently of mutations in genes encoding the VP22-interacting partners VP16 and vhs.

Quantification of the DNA Cleavage and Packaging Proteins UL15 and UL28 in A and B Capsids of Herpes Simplex Virus Type 1

ABSTRACT The proteins produced by the herpes simplex virus type 1 (HSV-1) genes UL15 and UL28 are believed to form part of the terminase enzyme, a protein complex essential for the cleavage of newly synthesized, concatameric herpesvirus DNA and the packaging of the resultant genome lengths into preformed capsids. This work describes the purification of recombinant forms of pUL15 and pUL28, which allowed the calculation of the average number of copies of each protein in A and B capsids and in capsids lacking the putative portal encoded by UL6. On average, 1.0 (±0.29 [standard deviation]) copies of pUL15 and 2.4 (±0.97) copies of pUL28 were present in B capsids, 1.2 (±0.72) copies of pUL15 and 1.5 (±0.86) copies of pUL28 were found in mutant capsids lacking the putative portal protein pUL6, and approximately 12.0 (±5.63) copies of pUL15 and 0.6 (±0.32) copies of pUL28 were present in each A capsid. These results suggest that the packaging machine is partly comprised of approximately 12 copies of pUL15, as found in A capsids, with wild-type B and mutant UL6(−) capsids containing an incomplete complement of cleavage and packaging proteins. These results are consistent with observations that B capsids form by default in the absence of packaging machinery in vitro and in vivo. In contrast, A capsids may be the result of initiated but aborted attempts at DNA packaging, resulting in the retention of at least part of the DNA packaging machinery.

Deletion of the Herpes Simplex Virus 1 UL49 Gene Results in mRNA and Protein Translation Defects That Are Complemented by Secondary Mutations in UL41

ABSTRACT Herpes simplex virus 1 (HSV-1) virions, like those of all herpesviruses, contain a protein layer termed the tegument localized between the capsid and the envelope. VP22, encoded by the UL49 gene, is one of the most abundant tegument proteins in HSV-1 virions. Studies with a UL49-null mutant showed that the absence of VP22 resulted in decreased protein synthesis at late times in infection. VP22 is known to form a tripartite complex with VP16 and vhs through direct interactions with VP16. Given that UL49-null mutants have been shown to acquire spontaneous secondary mutations in the UL41 gene, which encodes vhs, we hypothesized that VP22 and vhs may play antagonistic roles during HSV-1 infections. In the present study, we show that the protein synthesis defect observed in UL49-null virus infections was rescued by a secondary, compensatory frameshift mutation in UL41. A double mutant bearing a deletion of UL49 and a point mutation in vhs previously shown to specifically abrogate vhss RNase activity also resulted in a rescue of protein synthesis. To determine whether the UL49− protein synthesis defect, and the rescue by secondary mutations in vhs, occurred at the mRNA and/or translational levels, quantitative reverse transcriptase PCR (qRT-PCR) and polysome analyses were performed. We found that the absence of VP22 caused a small decrease in mRNA levels as well as a defect in polysome assembly that was independent of mRNA abundance. Both defects were complemented by the secondary mutations in vhs, indicating functional interplay between VP22 and vhs in both accumulation and translation of viral mRNAs.

Deletion of UL21 Causes a Delay in the Early Stages of the Herpes Simplex Virus 1 Replication Cycle

ABSTRACT The herpes simplex virus 1 (HSV-1) UL21 gene encodes a 62-kDa tegument protein with homologs in the alpha-, beta-, and gammaherpesvirus subfamilies. In the present study, we characterized a novel UL21-null virus and its genetic repair to determine whether this protein plays a role in early stages of the HSV-1 replication cycle. Single-step growth analyses, protein synthesis time courses, and mRNA quantifications indicated that the absence of UL21 results in a delay early in the HSV-1 replication cycle.

Streptomyces scopuliridis sp. nov., a bacteriocin- producing soil streptomycete

Actinomycete strain RB72(T) was isolated from woodland bluff soil in northern Alabama, USA, and shown to produce a broad spectrum bacteriocin. Based on morphological and chemotaxonomic characteristics, the strain was determined to belong to the genus Streptomyces. Phylogenetic analysis of the near-complete 16S rRNA gene sequence indicated that it differed from those of the described streptomycetes available in public databases. The distinctive white aerial hyphae and lack of sporulation suggest a deficiency in the whi pathway of the organism. A combination of substrate utilization patterns, morphological and chemotaxonomic characteristics and DNA-DNA hybridization results supported the affiliation of strain RB72(T) to the genus Streptomyces and enabled the genotypic and phenotypic differentiation of strain RB72(T) from closely related reference strains. Strain RB72(T) therefore represents a novel species of the genus Streptomyces, for which the name Streptomyces scopuliridis sp. nov. is proposed. The type strain is RB72(T) ( = DSM 41917(T)  = NRRL B-24574(T)).

First demonstration of equid gammaherpesviruses within the gastric mucosal epithelium of horses

Horses commonly develop gastric mucosal ulcers, similar to humans, a condition known as equine gastric ulcer syndrome (EGUS) that can lead to poor performance and lost training time and care expenses. Unlike humans, however, an infectious bacterial cause of ulcers has not been conclusively identified. Herpesviruses, while well-established causative agents of diseases such as cold sores, genital lesions, and certain types of cancer, have also been implicated in the development of a subset of gastric ulcers in humans. The presence of equid herpesviruses in the gastrointestinal tract and their potential contribution to EGUS has not been evaluated. Here, we provide the first evidence of equid gammaherpesviruses 2 and 5 (EHV-2 and -5) within the epithelium of the gastric mucosa of horses. These viruses were initially detected by a nested PCR screen of gastric tissue samples obtained from client- and university-owned horses with and without ulcers; however, no association with EGUS was found in this limited sample set. We then validated a highly sensitive in situ hybridization (ISH) assay and used this assay to characterize the distribution of these viruses in necropsy gastric tissue samples from five racehorses. Analyses revealed frequent EHV-2 and EHV-5 co-infections within the gastric mucosal epithelium, regardless of the ulcer status. These results are the first to demonstrate the presence of equid gammaherpesviruses in the gastric mucosa of horses and warrants further investigation to determine the contribution of these viruses to the development of EGUS and/or other gastrointestinal diseases.

A VP22-Null HSV-1 Is Impaired in Inhibiting CD1d-Mediated Antigen Presentation

CD1d-restricted T (natural killer T [NKT]) cells are important for controlling a herpes simplex virus (HSV) infection. One of the mechanisms of immune evasion by HSV is to downregulate CD1d-mediated activation of NKT cells. VP22 is an HSV-1-encoded protein responsible for reorganizing the host cells cytoskeletal network and viral spreading. We have previously shown that modification of the cytoskeleton can alter CD1d-mediated antigen presentation. In this study, we found that an HSV-1 lacking VP22 (ΔUL49) was impaired in its ability to inhibit CD1d-mediated antigen presentation compared with the wild-type (WT) virus; this was reversed by a repair virus (UL49R) in CD1d-expressing cells. We further demonstrated that CD1d recycling was inhibited by infection with WT and UL49R, but not the ΔUL49 virus. Ectopic expression of VP22 in CD1d-expressing cells complemented the VP22-deficient virus in inhibiting antigen presentation. Moreover, inhibiting viral protein synthesis rescued VP22-dependent inhibition of CD1d antigen presentation. In conclusion, our findings suggest that VP22 is required (but not sufficient) for the inhibition of CD1d-mediated antigen presentation by an HSV-1 infection.

Purification of full-length VP22 from cells infected with HSV-1: A two-pronged approach for the solubilization and purification of viral proteins for use in biochemical studies

VP22, encoded by the U(L)49 gene, is one of the most abundant proteins of the herpes simplex virus type 1 (HSV-1) tegument and has been shown to be important for virus replication and spread. However, the exact role(s) played by VP22 in the HSV-1 replication cycle have yet to be delineated. The lack of a procedure to purify full-length VP22 has limited molecular studies on VP22 function. A procedure was developed for the purification of soluble, full-length VP22 from cells infected with HSV-1. A recombinant virus encoding His-tagged VP22 was generated and found to express VP22 at levels comparable to the wild type virus upon infection of Vero cells. By experimenting with a wide variety of cell lysis buffer conditions, several buffers that promote the solubility of full-length VP22 were identified. Buffers that gave the highest levels of solubility were then used in immobilized metal ion affinity chromatography experiments to identify conditions that provided the greatest level of VP22 binding and recovery from cobalt and nickel affinity resins. Using this strategy soluble, full-length VP22 was purified from cells infected with HSV-1.

A coiled-coil strategy for the directional display of multiple proteins on the surface of iron oxide nanoparticles

Current methods for attachment of proteins to inorganic nanoparticle surfaces utilize strategies that can destroy the tertiary structure of large proteins and/or do not allow for directional attachment, thereby diminishing functionality. We report a novel approach for the conjugation of proteins to iron oxide nanoparticles (IONPs) through coiled-coil interactions. With this strategy, coiled-coiled interactions drive attachment of the desired protein, fused to a K-coil peptide, and E-coil peptides linked to the IONP surface via a nanoparticle attachment peptide (NAP). Importantly, this method allows for directional attachment of proteins without the use of either chemical conjugation or extreme pH solutions and, thus, allows maintenance of correct protein structure with functional orientation relative to the IONP surface. In our studies, monomeric red fluorescent protein (mRFP) and enhanced green fluorescent protein (EGFP) were used as model proteins to demonstrate the coiled-coil approach can be utilized to attach large proteins to IONP surfaces while maintaining complex tertiary structures. These proof-of-concept studies showed EGFP- and mRFP-K-coil fusion proteins interacted specifically with E-coil-coated nanoparticles and multiple different proteins could be displayed on individual IONPs. We did not observe fluorescence after conjugation of fluorescent proteins to either E-coil-coated IONPs or dopamine-coated IONPs, which was likely due to quenching or FRET activity induced by the iron oxide core. However, substituting an E-coil-bound chromatography resin for E-coil-coated IONPs allowed the preservation of protein fluorescence following coiled-coil attachment of K-coil-fused mRFP, demonstrating the coiled-coil attachment strategy provided maintenance of the mRFP tertiary structure required for fluorescence. The coiled-coil nanoparticle attachment strategy developed herein should have broad applications in nanomedicine.