Putative Capsid Protein Research Articles

Antigenic and genetic differentiation of the two putative types of human herpes virus 6

Ten human herpes virus 6 (HHV-6) strains from different origins were studied using reactivity to monoclonal antibodies and polymerase chain reaction analysis. Using immunofluorescence and neutralization assays, two monoclonal antibodies gave a positive reaction with the ten strains while three others only reacted with a fraction of these strains. This differential reactivity permitted segregation of the ten strains into two non-overlapping antigenic groups, designated as I and II. DNA was amplified from two regions of HHV-6 genome corresponding to the putative large tegument protein (LTP) gene and major capsid protein (MCP) gene, respectively. The restriction analysis of amplified products using HindIII for LTP and HaeII for MCP showed identical patterns among the strains belonging to the same antigenic group while BglII, TaqI and ClaI provided distinct patterns among group II strains. The nucleotide sequence of amplified products was determined and homology was found to be equal to or greater than 99% within each group whereas it was 96% between both groups. The number of amino-acid changes was higher when comparing two strains of different groups than when comparing two strains of the same group. The converging results of antigenic and genetic analyses led us to consider HHV-6 groups I and II as two distinct types of HHV-6 species.

Three different patterns of hepatitis C virus infection in chimpanzees.

The relationship between hepatitis C virus RNA and hepatitis C virus-associated antibodies (antibody against the putative capsid protein and C-100 antibody) was determined by nested polymerase chain reaction and enzyme-linked immunosorbent assay in serial serum samples obtained from eight chimpanzees experimentally infected with hepatitis C virus. Three different patterns emerged from the polymerase chain reaction data: the first (group 1) was acute resolving hepatitis with transient appearance of HCV RNA (two cases). The second (group 2) had chronic hepatitis with persistent hepatitis C virus RNA positivity (four cases) and the third (group 3) had chronic hepatitis with intermittent appearance of hepatitis C virus RNA (two cases). In four of eight animals, hepatitis C virus RNA was first detectable in serum 1 wk after inoculation. Although serum HCV RNA was detected in all infected chimpanzees, two were positive only for antibody against the putative capsid protein, whereas two were positive only for antibody to C-100 antigen. In four of eight cases, antibody against the putative capsid protein appeared earlier than did antibody to C-100 antigen, was detected just before or coincident with rising glutamate pyruvate transaminase values and remained positive for a long time even after recovery. Six of eight animals (75%) were still hepatitis C virus RNA positive 1 yr after inoculation, suggesting that the risk of development of the chronic carrier state is high in hepatitis C virus infection. Furthermore, there did not appear to be a good correlation between antibody titer in serum and hepatitis C virus infectivity titer.

Nucleotide sequence and genome organization of the murine polyomavirus, kilham strain

The polyomavirus Kilham strain (KV) represents a second murine member of the polyomavirus family. However, in contrast to other polyomaviruses, KV exhibits a stringent host and cell specificity. To determine the relationship of these viruses, the complete DNA sequence of KV consisting of 4754 by was determined. The predicted organization of K virus was found to be comparable to that of other members of the polyomavirus family with two strands coding in an opposite direction of an intergenic region harboring putative control elements for gene expression. These include consensus elements for the origin of DNA replication as well as predicted promoter protein binding domains. Inferred signal sequences for 3′ and 5′ end formation of mRNAs and splice/branch site consensus sequences resemble those found among the SV40 group of viruses. From the organization of the genome two nonstructural proteins, large T and small t antigen, are predicted, both of which share the same amino-terminal sequence. Three putative capsid proteins VP1, VP2, and VP3 are encoded by alternative open reading frames. The nucleotide sequence in the proposed origin of DNA replication and the inferred amino acid sequence of the viral proteins suggest an evolutionary relationship placing KV between the murine PyV and the SV40 group of viruses. In the region bearing putative transcriptional control elements less nucleotide similarity to that of other polyomaviruses is found and this may reflect the unique host and cell specificity of KV.

Helper virus-dependent replication, nucleotide sequence and genome organization of the satellite virus of maize white line mosaic virus

Virus like particles (17 nm in diameter) associated with maize white line mosaic virus (MWLMV) were shown to be a satellite virus of MWLMV (SV-MWLMV) on the basis of the following properties: (1) The SV-MWLMV was dependent upon the presence of MWLMV for replication in maize, while the latter virus could replicate independently of the SV particles. (2) No nucleotide sequence homology was detected between the SV-MWLMV and MWLMV, using complementary DNA probes prepared to the two RNAs, in a Northern blot hybridization analysis. (3) The RNA of the SV-MWLMV translated in vitro to produce a protein of the same Mr (24,000) as that found associated with the SV particles. This protein could be immunoprecipitated with an antiserum to the SV particles. And (4), there was no serological relationship between the coat proteins of MWLMV and the SV-MWLMV. The complete nucleotide sequence of the SV-MWLMV RNA (1168 nucleotides) was determined. The SV-MWLMV RNA contains a single open reading frame encoding a polypeptide of Mr 23,961. Computer analysis revealed no significant homology between SV-MWLMV RNA and any other viral or satellite RNAs. However, the putative SV-MWLMV capsid protein is predicted to share some structural features with the capsid protein of the satellite virus of panicum mosaic virus.

Further characterization of Rhopalosiphum padi virus of aphids and comparison of isolates from South Africa and Illinois

A South African isolate of Rhopalosiphum padi virus (RhPV) was directly compared with an isolate from Illinois. Although these viruses were serologically closely related, differences were detected in their capsid protein molecular weights and particle buoyant densities. The South African isolate was further characterized; two additional putative capsid proteins were found, an RNA poly(A) tract was detected, and an RNA size of 10 kb was calculated. Virions were found to degrade quickly below pH 3.0, to be stable between pH 5.0 and 8.4, and to lose RNA when heated to 56°C. From this evidence, and from radioiodination and Western blot reactions of capsid proteins, it is proposed that RhPV be classified as an enterovirus. No serological relationship was detected between RhPV and several other picorna- and picorna-like viruses. Three RhPV-specific double-stranded RNA species were isolated from infected aphids. Although virions could be isolated after long periods from plants on which viruliferous aphids had fed, and clean aphids could become infected by feeding on such plants, no replicative form RNA was detected in these plants.

Sequence analysis of hepatitis A virus cDNA coding for capsid proteins and RNA polymerase.

We report here the nucleotide sequence corresponding to two large regions of the hepatitis A virus (HAV) genome. These comprise a sequence of 3274 bases corresponding to the 5' end of the genome, which includes the putative capsid protein region of this picornavirus, and 1590 bases corresponding to the 3' end of the genome, terminating in a 15-base poly(A) tract. These sequences revealed that HAV had the characteristic genomic organization of picornaviruses: an open reading frame beginning approximately 750 bases from the 5' end of the RNA and a termination codon 60 bases from the 3' poly(A) tract. The predicted amino acid sequences of both regions have been compared to analogous regions previously determined for other picornaviruses. There was sufficient homology to conclude that the 5' region of HAV codes for capsid proteins and that the 3' region codes for an RNA polymerase. However, these regions of HAV were not found to be closely related to analogous regions of poliovirus, encephalomyocarditis virus, and foot and mouth disease virus.

In vitro translation of the genome of a small RNA virus from Trichoplusia ni

The genomic RNA of a member of the “ Nudaurelia β virus” group functioned as a mRNA in vitro. The translation products included a protein, which comigrated with the single virus capsid protein, and a stable 100 × 10 3 MW protein, which was synthesized by cleavage of a precursor protein. No precursor proteins were involved in synthesis of the putative capsid protein. Attempts to inhibit proteolytic cleavage did not result in the appearance of a product corresponding to the entire coding capacity of the genome.

Location and orientation of homologous sequences in the genomes of five herpesviruses.

Molecular hybridization experiments were carried out to investigate homologous regions in the genomes of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), equid herpesvirus 1 (EHV-1), pseudorabies virus (PRV) and varicella-zoster virus (VZV). Virion DNA probes from EHV-1, PRV and VZV hybridized to similar regions of the HSV genome, and the use of cloned DNA probes allowed heterologous genomes to be oriented with respect to homologous regions. The HSV-1 and HSV-2 genomes are colinear, the EHV-1 and VZV genomes are colinear with the IL or ISL genome arrangement of HSV, and the PRV genome is essentially colinear with the IL genome arrangement of HSV except that the region 0.1 to 0.4 fractional genome units appears to be inverted. A detailed analysis of sequences in the HSV-2 and PRV genomes to which the HSV-1 major capsid protein gene hybridized was carried out in order to demonstrate the application of molecular hybridization to the location of genes in heterologous genomes. The lesion in a DNA-positive temperature-sensitive mutant of PRV was mapped within the putative PRV major capsid protein gene. We conclude that the herpesviruses we have studied possess several highly conserved genes, and propose that they are similar in genetic organization despite presumably separate evolutionary histories.