Three spliced mRNAs of TT virus transcribed from a plasmid containing the entire genome in COS1 cells.

A permuted whole-genome construct of a TT virus (TTV), named VT416, had 3,852 nucleotides (nt) 98.2% similar to the prototype TA278 genome. To allow the transcription of TTV from the internal promoter, pBK*VT416(1.3G), carrying 1.3 units of VT416, was constructed. The poly(A)(+) RNAs expressed in COS1 cells 48 h posttransfection contained three TTV mRNA species 3.0, 1.2, and 1.0 kb in length, which were recovered in the 13 DNA clones from a lambda phage cDNA library. These mRNAs in the antigenomic orientation possessed in common the 3' terminus downstream of a poly(A) signal (A(3073)ATAAA) and the 5' terminus downstream of a cap site (C(98)ACTTC). A common splicing to join nt 185 with nt 277 was detected in all mRNAs. The coding region of the largest open reading frame (ORF) was maintained in 3.0-kb mRNA, because this splicing was located upstream of its initiation codon (A(589)TG). The second splicing was detected in 1.2-kb mRNA to join nt 711 with nt 2374 and in 1.0-kb mRNA to bind nt 711 to nt 2567. They linked a proposed ORF2 to another ORF for creating new ORFs over nt 2374 to 2872 in frame 2 and nt 2567 to 3074 in frame 3. The donor and acceptor sites of all three splicings matched the consensus sequence and were conserved in most of the 16 TTVs of distinct genotypes retrieved from the database. The observed transcription profile is unique to TTV among known members in the family Circoviridae.

High frequency of postnatal transmission of TT virus in infancy.

DNA of TT virus (TTV), a novel human circovirus, was tested for in 116 mother-infant pairs who had participated in the adult T-cell leukemia prevention program (APP) in Nagasaki, Japan, and refrained from breast-feeding. By polymerase chain reaction with Okamoto's seminested primers, 36 of the 115 (31%) mothers were positive. At the age of 6-8 months, 7 of 29 (24%) and 6 of 72 (8%) infants born to infected and uninfected mothers were positive, respectively (P = 0.047; RR, 2.90). Maternal TTV DNA load did not correlate with infantile infections. Since 99 of 100 (99%) cord blood samples were negative and all the mothers refrained from breast-feeding, the infantile TTV transmission would not be intrauterine or milk-borne. Between 6-8 and 12-21 months of age, 4 of 12 (33%) and 5 of 22 (23%) children born to infected and uninfected mothers turned positive, respectively (NS). At 12-21 months of age, 8 of 21 (38%) and 12 of 32 (38%) children born to infected and uninfected mothers were positive, respectively (NS). These results indicate that the TTV infection prevails in children at a frequency comparative to that in their mothers within the first 2 years of life, regardless of the maternal TTV status.

Identification of a novel GC-rich 113-nucleotide region to complete the circular, single-stranded DNA genome of TT virus, the first human circovirus.

The sequence data (H. Okamoto et al., Hepatol. Res. 10:1-16, 1998) of a newly discovered single-stranded DNA virus, TT virus (TTV), showed that it did not have the terminal structure typical of a parvovirus. Elucidation of the complete genome structure was necessary to understand the nature of TTV. We obtained a 1.0-kb amplified product from serum samples of four TTV carriers by an inverted, nested long PCR targeted for nucleotides (nt) 3025 to 3739 and 1 to 216 of TTV. The sequence of a clone obtained from serum sample TA278 was compared with those registered in GenBank. The complete circular TTV genome contained a novel sequence of 113 nt (nt 3740 to 3852 [=0]) in between the known 3'- and 5'-end arms, forming a 117-nt GC-rich stretch (GC content, 90.6% at nt 3736 to 3852). We found a 36-nt stretch (nt 3816 to 3851) with an 80.6% similarity to chicken anemia virus (CAV) (nt 2237 to 2272 of M55918), a vertebrate circovirus. A putative SP-1 site was located at nt 3834 to 3839, followed by a TATA box at nt 85 to 90, the first initiation codon of a putative VP2 at nt 107 to 109, the termination codon of a putative VP1 at nt 2899 to 2901, and a poly(A) signal at nt 3073 to 3078. The arrangement was similar to that of CAV. Furthermore, several AP-2 and ATF/CREB binding sites and an NF-kappaB site were arranged around the GC-rich region in both TTV and CAV. The data suggested that TTV is circular and similar to CAV in its genomic organization, implying that TTV is the first human circovirus.

Aberrant expression of double-stranded RNA-dependent protein kinase in hepatocytes of chronic hepatitis and differentiated hepatocellular carcinoma.

We immunohistochemically analyzed the expression of double-stranded RNA-dependent protein kinase (PKR) using a monoclonal antibody, 71/10. Test samples included 64 human liver biopsies and 25 liver sections of rats inoculated with diethylnitrosamine. The PKR signals in human fatty livers and normal rat livers were minimum. Scoring signal intensity from 0-4, the average scores of chronic active (14 cases) and chronic persistent (6 cases) hepatitis associated with hepatitis virus C (HCV) were 2.8 and 2.0, respectively (P = 0.038). The stained cells were significantly more abundant in the periportal than centrilobular regions for both chronic active and persistent hepatitis (P < 0.001 each). The average score of liver cirrhosis associated with HCV was 1.9. Those scores of well-, moderately, and poorly differentiated hepatocellular carcinomas associated with HCV were 3.4, 2.1, and 0.3, respectively (P < 0.001 for each pair). Those scores of well- and poorly differentiated carcinomas associated with hepatitis virus B were 2.3 and 0.0, respectively (P < 0.001). The average score of rat carcinomas induced by diethylnitrosamine was 1.9. Morphologically, nuclei of the vast majority of PKR-positive cells looked not apoptotic. The ratio of PKR-positive cells to apoptotic cells by terminal transferase-mediated dUTP nick end labeling method was approximately 20 in hepatitis, and over 100 in well-differentiated carcinoma.

Deleted HTLV-1 provirus in cord-blood samples of babies born to HTLV-1-carrier mothers.

We screened 596 cord-blood samples by nested short PCRs for the gag and pX regions of HTLV-1 which are capable of detecting a single copy. The samples were derived from 449 and 147 babies born to seropositive and seronegative mothers respectively. Of these, 20 samples were positive in at least one of the PCRs: 9 (45%) were positive in both PCRs, but 10 and 1 samples in either the pX or the gag PCR respectively. These samples were tested further in nested long PCRs directed for gag-pX, gag-pol and pol-pX regions capable of detecting 8, 1 and 2 copies respectively. Of 9 dually positive samples, 7 (77%) showed the predicted 6.2-kbp band in the gag-pX PCR; only 2 of them had the predicted band alone; 7 samples had discrete bands shorter than the predicted size. In the gag-pol PCR, all 9 samples showed the predicted 2.2-kbp band alone. In the pol-pX PCR, 819 samples showed the predicted 4.2-kbp band, including one with an additional 2.1-kbp band, and the last a 1.0-kbp band alone. Thus, all of the dually positive samples had proviruses harboring gag, pol and pX priming sites. In contrast, none of the 11 singly positive samples showed the predicted band in the gag-pX PCR: 5 had no visible band, and the other 6 had shorter bands only. None of these 11 samples showed any positive signal in either gag-pol or pol-pX PCR. Our results suggest that HTLV-1 proviruses in the cord blood are frequently defective.

Dependency of antibody titer on provirus load in human T lymphotropic virus type I carriers: an interpretation for the minor population of seronegative carriers.

To evaluate the prevalence of seronegative carriers of human T lymphotropic virus type I (HTLV-I), buffy coat samples from 1015 Okinawan high school students were tested by immunoassays and nested polymerase chain reaction (PCR). Among 17 HTLV-I carriers, 1 person who was seronegative and 1 who was PCR-negative were identified. gag and tax/rex PCR titers correlated with each other (r = .92; P < .001). Of the 17 carriers, 14 (82%) had high virus loads (geometric averages, 522 gag and 703 tax/rex copies/micrograms of DNA; 95% confidence intervals, 38-7260 and 75-6594, respectively). Carriers with low virus loads had < or = 2.2 gag copies. In the high-virus-load group, the gag PCR titers correlated with the antibody titers (r = 0.88; P < .001). The regression line intersected the minimum antibody detection level at 35 gag copies/micrograms of DNA. These results suggest that a small percentage of carriers may be seronegative.

Characterization of effector cells against B16 melanoma in mice inoculated with allogeneic spleen cells.

Inbred C57BL/6 (B6) mice which had received an inoculation of allogeneic spleen cells showed remarkable antitumor activity against syngeneic tumor challenge with B16 melanoma cells 3 days after the allogeneic cell inoculation. This antitumor activity was not specific to the inoculated alloantigen, since the challenging B16 cells are syngeneic to B6 mice and since it was induced by BALB/c spleen cells as well as C3H/He spleen cells. The antitumor activity was sensitive to an in vivo treatment with anti-asialo GM1 (AGM1) antiserum or anti-Thy.1 monoclonal antibody (mAb) just before the tumor challenge and was resistant to an in vivo treatment with anti-CD8 (Ly.2) mAb. These results suggest that AGM1+Thy.1+CD8- activated natural killer (NK) cells were generated by alloantigen inoculation and took an important part in the antitumor effect of the alloantigen inoculation.

Rapid DNA diagnosis of herpes simplex virus serotypes.

The presence of nucleotide sequences specific for each of herpes simplex virus (HSV) serotypes was demonstrated. These sequences were applied for dot DNA-DNA hybridization and for PCR for rapid DNA diagnosis of HSV infections. These sequences were found by molecular cloning of HSV-DNA fragments after digestion of DNA by KpnI enzyme. The type 1-specific sequence was found around the 5' end of BamHI B-fragment in the L region of type 1 DNA (corresponds to alpha gene 27, promoter-regulatory region) and the type 2-specific sequence was around the junction region of the L and S of type 2 DNA (corresponds to a' sequence). Both simple dot blot hybridization and PCR of HSV DNA's, employing these type-specific nucleotide sequences, were proven to be much more useful than immunofluorescence in terms of type-specific diagnosis of HSV infections.

A new method for extracting DNA or RNA for polymerase chain reaction.

The use of glass powder suspension for the extraction of RNA or DNA was studied to simplify the procedures of polymerase chain reaction (PCR). Using this procedure, proviral DNA of human T-lymphotropic virus type-1 (HTLV-1) in the blood of an asymptomatic virus carrier and viral RNA of human immunodeficiency virus (HIV) in the blood of an AIDS patient were easily detected by PCR employing glass powder. The use of glass powder is a simple and highly efficient procedure for the extraction of DNA or RNA, and can be applied for routine PCR.

Early development of CD8-negative and CD8-positive MHC-unrestricted cytotoxic cells induced by alloantigen inoculation in mice.

Peritoneal cells (PC) in C57B1/6 (B6, H-2b) mice receiving an intraperitoneal (i.p.) injection of allogeneic BALB/c (H-2d) spleen cells demonstrated potent cytotoxic activity against syngeneic, xenogeneic, third-party allogeneic tumors as well as H-2d derived tumors. Maximum cytotoxic activity against various tumors other than H-2d derived tumor, B16 (H-2b) was elicited on day 3 post allosensitization and decreased drastically thereafter, whereas cytotoxic activity against P815 (H-2d) peaked 3 days after the inoculation and maintained the peak activity thereafter. Surface phenotype of PC responsible for the cytotoxic activity against B16 was Thy-1+/-, Lyt-2-, L3T4-, asialo GM1 (AGM1)+, and that of PC against P815 was Thy-1+, Lyt-2+ (or Lyt-2+/-), L3T4-, AGM1+. These phenotypes showed similar phenotypes to the counterparts against B16 and against P815 in spleen cells induced by intravenous inoculation of alloantigen. When mice were pretreated i.p. with anti-AGM1 antibody before the allosensitization, anti-P815 cytotoxic-activity in PC was completely diminished. Similar activity in spleen, however, was enhanced by i.v. treatment with the antibody before the i.v. inoculation of alloantigen. The data clearly demonstrate that in vivo inoculation of B6 mice with normal allogeneic cells induces "NK-like" CD8- cytotoxic cells and "anomalous" CD8+ cytotoxic cells in PC.

Sequence analysis of the nucleocapsid protein gene of human coronavirus 229E.

Human coronaviruses are important human pathogens and have also been implicated in multiple sclerosis. To further understand the molecular biology of human coronavirus 229E (HCV-229E), molecular cloning and sequence analysis of the viral RNA have been initiated. Following established protocols, the 3'-terminal 1732 nucleotides of the genome were sequenced. A large open reading frame encodes a 389 amino acid protein of 43,366 Da, which is presumably the nucleocapsid protein. The predicted protein is similar in size, chemical properties, and amino acid sequence to the nucleocapsid proteins of other coronaviruses. This is especially evident when the sequence is compared with that of the antigenically related porcine transmissible gastroenteritis virus (TGEV), with which a region of 46% amino acid sequence homology was found. Hydropathy profiles revealed the existence of several conserved domains which could have functional significance. An intergenic consensus sequence precedes the 5'-end of the proposed nucleocapsid protein gene. The consensus sequence is present in other coronaviruses and has been proposed as the site of binding of the leader sequence for mRNA transcriptional start. This region was also examined by primer extension analysis of mRNAs, which identified a 60-nucleotide leader sequence. The 3'-noncoding region of the genome contains an 11-nucleotide sequence, which is relatively conserved throughout the Coronavirus family and lends support to the theory that this region is important for the replication of negative-strand RNA.

Sequence analysis of nucleocapsid gene and leader RNA of human coronavirus OC43.

The nucleotide sequence of the 3'-end of the genomic RNA of human coronavirus OC43 (HCV-OC43) was determined from the cDNA clones of the intracellular virus-specific mRNAs. The nucleotide sequence and the predicted amino acid sequence of the main open reading frame (ORF), which represents the nucleocapsid (N) protein, were highly homologous to those of bovine coronavirus (BCV) Mebus strain. This ORF predicts a protein of 448 amino acids. Additional smaller ORFs are also present in a different reading frame. We have also determined the leader sequence present at the 5'-end of HCV-OC43 mRNAs by a primer extension study. This sequence is highly homologous to that of mouse hepatitis virus, particularly in the 3'-end of the leader sequence, which is postulated to be involved in the unique mechanism of leader-primed transcription. These data suggest that HCV-OC43 and BCV might have diverged from each other fairly recently and that the 3'-end of the leader sequence has significant functional roles.

Human hepatitis delta antigen is a nuclear phosphoprotein with RNA-binding activity.

The genetic origin, structure, and biochemical properties of the delta antigen (HDAg) of a human hepatitis delta virus (HDV) were investigated. A cDNA fragment containing the open reading frame encoding the HDAg was transcribed into RNA and used for in vitro translation in rabbit reticulocyte lysates. The HDAg open reading frame was also inserted into an expression vector containing a simian virus 40 T-antigen promoter and expressed into COS 7 cells. In both systems, a protein species of 26 kilodaltons was synthesized from this open reading frame and could be specifically immunoprecipitated with antisera obtained from patients with delta hepatitis. A similar protein was also synthesized from antigenomic-sense monomeric HDV RNA in both systems, although the efficiency of translation was lower than that of the isolated open reading frame. This protein was found to be phosphorylated at the serine residues. Immunoperoxidase studies with anti-HDV sera demonstrated that the HDAg was expressed mainly in the nuclei of the transfected COS 7 cells. Moreover, the HDAg was shown to bind the genomic RNA of HDV. These studies indicate that HDAg is encoded by the antigenomic-sense RNA of HDV and is a nuclear phosphoprotein associated with an RNA-binding activity.

Molecular cloning and sequencing of a human hepatitis delta (delta) virus RNA.

Human hepatitis delta (delta) virus (HDV) is a form of defective virus, which infects humans only in the presence of a co-infecting hepatitis B virus (HBV). HDV superinfection in a chronic HBV carrier often results in severe chronic hepatitis and cirrhosis, whereas acute HDV and HBV co-infection is frequently associated with fulminant hepatitis. HDV consists of a 36-nm particle, which contains an envelope with HBV surface antigen, and a nucleocapsid containing the hepatitis delta-antigen (HDAg) and an RNA genome of 1.75 kilobases (kb). Recently, the genomic RNA from an HDV serially passaged in chimpanzees has been cloned and sequenced in a study which showed that the HDV RNA is a single-stranded circular molecule with properties similar to those of viroid or virusoid. However, it is not known whether serial passages in chimpanzees had altered the properties of human HDV. Here we report the cloning and sequencing of an HDV RNA isolated directly from a patient with acute delta-hepatitis. The sequence showed considerable divergence (11%) from that of the chimpanzee-adapted HDV. Five open reading frames (ORFs) of more than 100 amino acids in both genomic and anti-genomic sense were found. The largest ORF in antigenomic sense, which can code for 214 amino acids, may correspond to the HDAg.

Isolation and characterization of a cold-sensitive strain of coxsackievirus A10.

A coxsackievirus A10 strain, isolated from a clinical specimen from a patient with pharyngitis, was characterized with respect to its growth properties in different cultured cells and at different incubation temperatures. This virus multiplied within cultured cells and produced cytopathogenic effects, whereas a prototype strain of coxsackievirus A10 did not. The isolate multiplied efficiently in cultured cells at 37 degrees C but its replication was markedly restricted at 32 degrees C. Temperature shift experiments indicated that the cold-sensitive event affected the late function(s) of the virus.

Augmentation of killer activity of murine spleen cells against allogeneic and syngeneic tumor cells by inoculation of alloantigen in vivo.

After C57BL/6 (B6) mice were inoculated with BALB/c spleen cells via tail vein, kinetics of cytotoxic activities in the B6 mice against sensitizing alloantigens (H-2d) and against syngeneic antigens were investigated using, as target cells, P815 mastocytoma cells (H-2d) and B16 melanoma cells (H-2b). Cytotoxic activity against P815 in the B6 spleen cells reached a peak 3 days after alloantigen inoculation, decreased drastically on day 5 and rose again thereafter. The profile of anti-B16 cytotoxic activity was similar to that of anti-P815 activity. The cytotoxic activity against P815 was inhibited partially by cold B16, but that against B16 was not inhibited by cold P815. Surface phenotype of cytotoxic cells against P815 was Lyt2+, Thy1+, Asialo GM1+ and that of cytotoxic cells against B16 was Lyt2-, Thy1+/-, and Asialo GM1+. The results indicate that inoculation of B6 mice with allogeneic BALB/c spleen cells induce two types of cytotoxic cells; one is similar to lymphokine-activated killer (LAK) cells and the other is activated natural killer cells.

Actin filaments and tumorigenicity in a Fischer rat embryo fibroblast cell line (3Y1) transformed by ultraviolet-irradiated HSV.

The characteristics of the cytoskeleton of a Fischer rat embryo fibroblast cell line (3Y1) transformed by ultraviolet (UV)-irradiated HSV were studied by indirect immunofluorescence using anti-actin IgG. Parental 3Y1 cells possessed well-developed actin filaments, while 3Y1 cells transformed by UV-irradiated HSV also retained well-developed actin filaments. Transformed cells were divided into 2 groups according to tumorigenicity in newborn Fischer rats; one had a strongly tumorigenic potential and the other a weakly tumorigenic potential. Tumor-derived cell lines exhibited a highly tumorigenic potential, and were also divided into 2 groups, one with well-developed actin filaments and the other without well-developed actin filaments. Our results suggested that transformation or tumor formation by HSV is a multi-step process and that morphological loss of actin filaments in the cells is not essential to the tumorigenic potential of the cells transformed by HSV.