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PubMed1994

Targeting of the site of nonhomologous genetic recombination in brome mosaic virus.

The genome of brome mosaic virus (BMV) consists of three positive strand RNA segments that share a high degree of sequence homology in the 3' noncoding region. The phenomenon of both homologous and nonhomologous intersegment RNA-RNA recombinant has been demonstrated within the 3' noncoding region of BMV RNAs. It has been postulated that nonhomologous crossovers occur at local heteroduplexes formed between the recombining BMV RNA substrates of the same polarity and that the formation of double-stranded regions facilitates strand switching by the replicase. To test the hypothesis of hybridization-mediated recombination in BMV, RNA-3 constructs carrying short antisense RNA1-derived sequences have been used to induce nonhomologous recombination events between RNA-1 and RNA-3 at or near the site of hybridization. We find that both the incidence of recombination and the location of recombinant junctions depends on the structure and the stability of heteroduplexes. Furthermore, our preliminary results demonstrate that mutations in the helicase-like domain of BMV protein 1a affect the location of recombinant junctions. This provides experimental evidence that BMV replicase protein 1a participates in recombination.

Bromovirus↗
PubMed1988

Nucleotide sequence of the first exon of the rat c-myc gene: proviral insertions in murine leukemia virus-induced lymphomas do not affect exon 1.

We have previously reported that proviruses are integrated adjacent to the c-myc gene in rat thymomas induced by murine leukemia viruses. In order to characterize these insertions, we have isolated recombinant DNA clones from normal rat DNA containing all of the normal rat c-myc gene, and from two Moloney murine leukemia virus-induced lymphomas containing both proviral and adjacent rat c-myc sequences. We determined the DNA sequence of portions of the normal and one tumor-derived clone. The normal and tumor-derived exon 1 sequences are identical. By comparing our sequence to the sequences of mouse and human c-myc, we located the first exon of the rat c-myc gene. Analysis of the tumor-derived rat c-myc clones showed that proviral integration occurred approximately 1.4 kb upstream of exon 1 of c-myc in the case of one tumor and 0.55 kb upstream of c-myc exon 1 in the other. Thus, we conclude that the proviral insertions in these tumors did not affect the rat c-myc gene by altering the structure of the c-myc RNA. Consistent with this, the c-myc RNA present in a cell line derived from one of these tumors is identical in size to the normal c-myc RNA. Furthermore, the level of c-myc expression is not dramatically elevated in this cell line. Exon 1 of the rat c-myc gene contains no ATG start codons and contains multiple stop codons in all three reading frames, indicating that it, like the chicken and mouse exon 1 sequences, is noncoding. The extent of homology between our sequence of rat c-myc exon 1 and the published sequence of human c-myc exon 1 is similar to the extent of homology between the sequences of mouse and human c-myc exon 1. The rat and mouse c-myc exon 1 sequences differ from each other by about the amount predicted from the known divergence times of mice from rats. Exon 1 of c-myc is only slightly conserved, evolving at a rate similar to that seen for introns and pseudogenes.

Animals↗
PubMed1989

Internal entry of ribosomes and ribosomal scanning involved in hepatitis B virus P gene expression.

The recent demonstration that the synthesis of duck hepatitis B virus (HBV) reverse transcriptase does not require translational frameshifting and the finding that poliovirus mRNA translation occurs in a cap-independent manner by internal binding of ribosomes in the 5' noncoding region led us to design experiments to test the hypothesis of internal entry of ribosomes on C gene mRNA for HBV P gene expression. We show that in human cells, translation can be initiated at the first AUG of the HBV P gene by entry of ribosomes in a region located upstream of the P gene. Moreover, the leaky scanning of ribosomes observed on the first AUG of the HBV P gene could be responsible for the synthesis of the two forms of reverse transcriptase described for HBV particles.

Amino Acid Sequence↗
PubMed1998

Interference with Physalis mottle tymovirus replication and coat protein synthesis by transcripts corresponding to the 3'-terminal region of the genomic RNA--role of the pseudoknot structure.

The role of the 3' noncoding (NC) region of Physalis mottle tymovirus genomic RNA in the multiplication of the virus was examined using an in vivo protoplast assay system. Coat protein (CP) synthesis was specifically inhibited by sense 3' NC region transcripts. To establish the role of the pseudoknot structure present in the NC region in virus multiplication, four site-specific mutants, two of which disrupted the pseudoknot structure while the other two restored the structure, were constructed. Interestingly, none of the four sense mutant transcripts inhibited CP synthesis, suggesting that the specific sequence representing the 3' terminal pseudoknot structure may play an important role in virus multiplication. However, the wild-type antisense 3' NC transcript as well as the four antisense mutant transcripts inhibited CP synthesis, suggesting that the inhibitions by antisense transcripts could be due to the formation of RNA-RNA hybrids at the 3' end of the genomic RNA.

Capsid↗
PubMed1993

Lack of mother-to-infant transmission of hepatitis C virus in human immunodeficiency virus-seronegative women: a prospective study with hepatitis C virus RNA testing.

The published risk of mother-to-infant transmission of hepatitis C virus varies according to the population studied and the tests used. In a prospective study we used the polymerase chain reaction to assess the risk of vertical transmission of hepatitis C virus in an unselected population of women uninfected by human immunodeficiency virus. Hepatitis C virus antibodies were sought with a second-generation enzyme-linked immunosorbent assay in 2,367 consecutive pregnant women. Forty-one were positive, and 17 consented to serological follow-up of their offspring (n = 18). A second-generation recombinant immunoblot assay, ALT determination and hepatitis C virus RNA testing were performed on maternal sera obtained during pregnancy and sera from the offspring at birth and thereafter. Five older brothers or sisters were also tested. Hepatitis C virus RNA sequences in serum were amplified with a modified nested polymerase chain reaction procedure with primers from the highly conserved 5' noncoding region of the hepatitis C virus genome. All the neonates were positive for hepatitis C virus antibodies, with enzyme-linked immunosorbent assay titers and recombinant immunoblot assay patterns similar to those of their mothers. After birth hepatitis C virus antibodies gradually disappeared within 6 mo. Hepatitis C virus RNA was consistently negative in the 18 children from birth to 24 mo (range = 3 to 24 mo) and in the 5 older children, regardless of the hepatitis C virus polymerase chain reaction status of the mothers (8 of whom were positive).(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1994

Cap-dependent and cap-independent translation by internal initiation of mRNAs in cell extracts prepared from Saccharomyces cerevisiae.

Translation extracts were prepared from various strains of Saccharomyces cerevisiae. The translation of mRNA molecules in these extracts were cooperatively enhanced by the presence of 5'-terminal cap structures and 3'-terminal poly(A) sequences. These cooperative effects could not be observed in other translation systems such as those prepared from rabbit reticulocytes, wheat germ, and human HeLa cells. Because the yeast translation system mimicked the effects of the cap structure and poly(A) tail on translational efficiency seen in vivo, this system was used to study cap-dependent and cap-independent translation of viral and cellular mRNA molecules. Both the 5' noncoding regions of hepatitis C virus and those of coxsackievirus B1 conferred cap-independent translation to a reporter coding region during translation in the yeast extracts; thus, the yeast translational apparatus is capable of initiating cap-independent translation. Although the translation of most yeast mRNAs was cap dependent, the unusually long 5' noncoding regions of mRNAs encoding cellular transcription factors TFIID and HAP4 were shown to mediate cap-independent translation in these extracts. Furthermore, both TFIID and HAP4 5' noncoding regions mediated translation of a second cistron when placed into the intercistronic spacer region of a dicistronic mRNA, indicating that these leader sequences can initiate translation by an internal ribosome binding mechanism in this in vitro translation system. This finding raises the possibility that an internal translation initiation mechanism exists in yeast cells for regulated translation of endogenous mRNAs.

Animals↗
PubMed2000

Genetic epidemiology of hepatitis C virus throughout egypt.

Hepatitis C virus (HCV) infection is a major health problem in Egypt, where the seroprevalence is 10-20-fold higher than that in the United States. To characterize the HCV genotype distribution and concordance of genotype assessments on the basis of multiple genomic regions, specimens were obtained from blood donors in 15 geographically diverse governorates throughout Egypt. The 5' noncoding, core/E1, and NS5B regions were amplified by reverse transcription-polymerase chain reaction and analyzed by both restriction fragment length polymorphism (RFLP) and phylogenetic tree construction. For the 5' noncoding region, 122 (64%) of 190 specimens were amplified and analyzed by RFLP: 111 (91%) were genotype 4, 1 (1%) was genotype 1a, 1 (1%) was genotype 1b, and 9 (7%) could not be typed. Phylogenetic analyses of the core/E1 and NS5B regions confirmed the genotype 4 preponderance and revealed evidence of 3 new subtypes. Analysis of genetic distance between isolates was consistent with the introduction of multiple virus strains 75-140 years ago, and no clustering was detected within geographic regions, suggesting widespread dispersion at some time since then.

Blood Donors↗
PubMed1999

The genome nucleotide sequence of a contemporary wild strain of measles virus and its comparison with the classical Edmonston strain genome.

The only complete genome nucleotide sequences of measles virus (MeV) reported to date have been for the Edmonston (Ed) strain and derivatives, which were isolated decades ago, passaged extensively under laboratory conditions, and appeared to be nonpathogenic. Partial sequencing of many other strains has identified >/=15 genotypes. Most recent isolates, including those typically pathogenic, belong to genotypes distinct from the Edmonston type. Therefore, the sequence of Ed and related strains may not be representative of those of pathological measles circulating at that or any time in human populations. Taking into account these issues as well as the fact that so many studies have been based upon Ed-related strains, we have sequenced the entire genome of a recently isolated pathogenic strain, 9301B. Between this recent isolate and the classical Ed strain, there were 465 nucleotide differences (2.93%) and 114 amino acid differences (2.19%). Computation of nonsynonymous and synonymous substitutions in open reading frames as well as direct comparisons of noncoding regions of each gene and extracistronic regulatory regions clearly revealed the regions where changes have been permissible and nonpermissible. Notably, considerable nonsynonymous substitutions appeared to be permissible for the P frame to maintain a high degree of sequence conservation for the overlapping C frame. However, the cause and the effect were largely unclear for any substitution, indicating that there is a considerable gap between the two strains that cannot be filled. The sequence reported here would be useful as a reference of contemporary wild-type MeV.

3' Untranslated Regions↗
PubMed2001

[Reconstruction of hepatitis D virus ribozymes and their ability to trans-cleave hepatitis C virus RNA].

OBJECTIVE: To study whether reconstructed hepatitis D virus (HDV) ribozymes have the ability to trans-cleave hepatitis C virus (HCV) RNA. METHODS: We reconstructed the stem IV and substrate-binding region of HDV genomic ribozymes, thus obtained three HDV ribozymes named RzC1, RzC2 and RzC3 expected to be able to trans-cleave HCV RNA at predicted sites. The substrate containing HCV RNA 5'-noncoding region (5'-NCR) and 5'-fragment of C region (HCV RNA 5'-NCR-C) was synthesized by transcription in vitro, then radiolabelled at its 5'-end. Under certain pH and appropriate concentration of Mg(2+) with or without deionized formamide, the ribozymes and their substrate were mixed at mol ratio of 100 : 1 and reacted for two hours. Trans-cleaved products were shown by denatured polyacrylamide gel electrophoresis and autoradiography, and the percentage of trans-cleaved substrate was calculated as the activity indicator of these ribozymes. RESULTS: RzC1 and RzC2 were able to trans-cleave HCV RNA 5'-NCR-C site specifically, and their activity could be enhanced by certain concentration of deionized formamide. RzC3 could not trans-cleave the substrate. CONCLUSIONS: Optimized HDV genomic ribozymes can trans-cleave HCV RNA.

5' Untranslated Regions↗
PubMed1983

Regulation of polyoma virus transcription in murine embryonal carcinoma cells.

Undifferentiated murine embryonal carcinoma (EC) cells are resistant to infection with wild-type polyoma virus. The block appears to be located at the transcriptional level. Polyoma host range mutants capable of expressing early and late functions in EC cells have been isolated. The modifications responsible for the phenotype of these mutants are localized in the noncoding region of polyoma DNA genome, containing regulatory sequences for replication and transcription. We compared the 5' termini of early and late mRNAs of wild-type polyoma and mutant viruses in EC cells and in permissive cells. Our results show that wild-type mRNA is normally spliced in EC cells but present at a very low level. The sequence modifications of the mutant viruses lead to a 100-fold increase in the production of mRNA in these cells, but the major 5' termini of early and late mRNAs are identical to those in wild-type-infected 3T6 cells.

Animals↗
PubMed1994

Geographical distribution of hepatitis C virus genotypes in blood donors: an international collaborative survey.

The frequency of infection with the six classified major genotypes of hepatitis C virus (HCV) was investigated in 447 infected volunteer blood donors from the following nine countries: Scotland, Finland, The Netherlands, Hungary, Australia, Egypt, Japan, Hong Kong, and Taiwan. Viral sequences in plasma from blood donors infected with HCV were amplified in the 5'-noncoding region and were typed by restriction fragment length polymorphism analysis. Electrophoresis of DNA fragments produced by cleavage with HaeIII-RsaI and ScrFI-HinfI allowed HCV types 1 (or 5), 2, 3, 4, and 6 to be identified. Further analysis with MvaI-HinfI allowed sequences of the type 5 genotype to be distinguished from sequences of the type 1 genotype. Types 1, 2, and 3 accounted for almost all infections in donors from Scotland, Finland, The Netherlands, and Australia. Types 2 and 3 were not found in the eastern European country (Hungary), where all but one of the donors were infected with type 1. Donors from Japan and Taiwan were infected only with type 1 or 2, while types 1, 2, and 6 were found in those from Hong Kong. HCV infection among Egyptians was almost always by type 4. Donors infected with HCV type 1 showed broad serological reactivity with all four antigens of the second generation Chiron RIBA-2 assay (Chiron Corporation, Emeryville, Calif.), while infection with divergent HCV genotypes elicited antibodies mainly reactive to c22-3 and c33c. Reactivities with antibodies 5-1-1 and c100-3 were infrequent and were generally weak, irrespective of the geographical origin of the donor. Because the envelope region of HCV is even more variable than the NS-4 region, it is likely that vaccines based on these proteins need to be multivalent and perhaps specifically adapted for different geographical regions.

Base Sequence↗
PubMed1996

Molecular characterization of the Japanese encephalitis serocomplex of the flavivirus genus.

The Japanese encephalitis (JE) serocomplex of flaviviruses comprises 10 members, 9 of which: Alfuy (ALF); Koutango (KOU); Kokobera (KOK); Kunjin (KUN); Murray Valley encephalitis (MVE); JE; Stratford (STR); Usutu (USU); and West Nile (WN) have been isolated from Africa, southern Europe, Middle East, Asia, and Australia. The tenth member, St. Louis encephalitis (SLE) virus, is confined to North, Central, and South America. For ALF, KOK, KOU, STR, and USU, no sequence data have as yet been reported, and little molecular phylogeny has been determined for this complex as a whole. Using a rapid, one-step RT-PCR and universal primers, we have amplified and sequenced a 450-600 base pair region of the virus genome encompassing the N terminus of the nonstructural protein NS5 and the 5' end of the 3' noncoding region, for several strains of all of these viruses, except USU and SLE viruses. These data, as well as published sequence data for other flaviviruses, were analyzed with the ClustalW and Phylip computer packages. The resultant phylogenetic data were consistent with some of the current flavivirus serological classification, showing a close relationship between ALF and MVE viruses and between KOK and STR viruses, but suggested that KOK and STR are distantly related to the other viruses and should perhaps be reclassified in their own serocomplex. The data also confirmed the close relationship between KUN and WN viruses and showed that an isolate of KUN virus from Sarawak may represent a "link" between these two virus species. In addition, the primary sequence data revealed a polymorphic region just downstream of the stop codon in the 3' end of the viral genomes.

Amino Acid Sequence↗
PubMed1992

General primer-mediated polymerase chain reaction for detection of enteroviruses: application for diagnostic routine and persistent infections.

The aim of this study was to determine the applicability of the polymerase chain reaction (PCR) for routine diagnostic use and for the detection of persistent enteroviral infections. To this end, general primers were selected in the highly conserved part of the 5'-noncoding region of the enteroviral genome. They were tested on 66 different enterovirus serotypes. A specific fragment was amplified from 60 of 66 serotypes. An amplification product was not observed from coxsackievirus types A11, A17, and A24 and echovirus types 16, 22, and 23. Enteroviral RNA was detected by the PCR in routinely collected throat swabs and stool specimens that were found to be positive for enterovirus by isolation in tissue culture. Enteroviral RNA was detected in one of five myocardial biopsy specimens from patients with dilated cardiomyopathy, implicating virus persistence. No amplification product was obtained from eight control samples. Our results demonstrate the significance of the PCR for the detection of enteroviral RNA and, in particular, for the demonstration of persistent enteroviral infections.

Base Sequence↗
PubMed1989

Genetic variation occurring on the genome of an in vitro insertion mutant of poliovirus type 1.

An insertion sequence of 72 nucleotides prepared from a polylinker sequence of plasmid pUC18 was introduced at nucleotide position 702 of the 5' noncoding sequence (742 nucleotides long) of the genome of the Sabin strain of poliovirus type 1 by using an infectious cDNA clone of the virus strain. The insertion mutant thus obtained showed a small-plaque phenotype compared with that of the parent virus. Apparent revertants (large-plaque variants) were easily generated from the insertion mutant. Nucleotide sequence analysis was performed on the revertant genomes to determine the mutation(s) by which the plaque size of the parent virus was regained. Some large-plaque variants lacked genomic sequences including all or a part of the insertion sequence. A computer-aided search for secondary structures with respect to the deletion sites detected possible supporting sequences which provided fairly stable secondary structures at the deletion sites. This result was consistent with our supporting sequence-loop model which had been proposed as a new copy-choice model for the generation of genetic rearrangements occurring on single-stranded RNA genomes (S. Kuge, I. Saito, and A. Nomoto, J. Mol. Biol. 192:473-487, 1986). The other large-plaque variants had point mutations at any one of three positions of an AUG existing in the insertion sequence. A small-plaque phenotype was observed when an AUG codon was inserted in frame or out of frame with regard to the initiation site of viral polyprotein synthesis. Our data strongly suggest that an AUG sequence in this genome region is deleterious for efficient poliovirus replication.

Chromosome Deletion↗
PubMed2003

Pathogenicity of GB virus C on virus hepatitis and hemodialysis patients.

AIM: To determine the pathogenicity of GB virus C (GBV-C) on liver and the effects of its co-infection on the clinical features and prognosis of patients with hepatitis B and C. METHODS: Cross-sectional study was carried out in 413 patients with acute, chronic hepatitis B or liver cirrhosis, and in 67 hemodialysis patients. A 20-month prospective cohort study was carried out in 95 hepatitis B and 80 hepatitis C patients. A reverse transcriptase nested polymerase chain reaction (RT-nPCR) of the 5'-noncoding region was used to detect circulating GBV-C RNA. Liver function was determined by an automated analyzer for all patients. RESULTS: The prevalence of GBV-C in the high-risk populations with the virus transmitted via blood was high, ranging from 16.2 to 28.8 %. Co-infection with GBV-C in hepatitis B patients did not affect the clinical features of the disease or liver function. The dialysis patients infected with GBV-C alone did not develop functional changes to the liver. Prospective cohort study showed that GBV-C co-infection did not affect the clinical features, prognosis or negative serum conversion rate of chronic hepatitis B and C. CONCLUSION: The results suggest that GBV-C has no marked pathogenicity on liver, so it may not be a hepatitis virus.

Cohort Studies↗
PubMed2001

RNA splicing at human immunodeficiency virus type 1 3' splice site A2 is regulated by binding of hnRNP A/B proteins to an exonic splicing silencer element.

The synthesis of human immunodeficiency virus type 1 (HIV-1) mRNAs is a complex process by which more than 30 different mRNA species are produced by alternative splicing of a single primary RNA transcript. HIV-1 splice sites are used with significantly different efficiencies, resulting in different levels of mRNA species in infected cells. Splicing of Tat mRNA, which is present at relatively low levels in infected cells, is repressed by the presence of exonic splicing silencers (ESS) within the two tat coding exons (ESS2 and ESS3). These ESS elements contain the consensus sequence PyUAG. Here we show that the efficiency of splicing at 3' splice site A2, which is used to generate Vpr mRNA, is also regulated by the presence of an ESS (ESSV), which has sequence homology to ESS2 and ESS3. Mutagenesis of the three PyUAG motifs within ESSV increases splicing at splice site A2, resulting in increased Vpr mRNA levels and reduced skipping of the noncoding exon flanked by A2 and D3. The increase in Vpr mRNA levels and the reduced skipping also occur when splice site D3 is mutated toward the consensus sequence. By in vitro splicing assays, we show that ESSV represses splicing when placed downstream of a heterologous splice site. A1, A1(B), A2, and B1 hnRNPs preferentially bind to ESSV RNA compared to ESSV mutant RNA. Each of these proteins, when added back to HeLa cell nuclear extracts depleted of ESSV-binding factors, is able to restore splicing repression. The results suggest that coordinate repression of HIV-1 RNA splicing is mediated by members of the hnRNP A/B protein family.

3' Untranslated Regions↗
PubMed1993

A mutation in the RNA polymerase of poliovirus type 1 contributes to attenuation in mice.

The attenuated Sabin strain of poliovirus type 1 (PV-1) differs from the neurovirulent PV-1 Mahoney strain by 55 nucleotide mutations. Only one of these mutations (A-480-->G, in the 5' noncoding (5' NC) region of the genome, is well characterized, and it confers a strong attenuating effect. We attempted to identify genetic attenuation determinants in the 3'-terminal part of the Sabin 1 genome including the 3D polymerase (3Dpol) gene and the 3' NC region. Previous studies suggested that some of the 11 mutations in this region of the Sabin 1 genome, and in particular a mutation in the polymerase gene (U-6203-->C, Tyr-73-->His), are involved to some extent in the attenuation of PV-1. We analyzed the attenuating effect in the mouse model by using the mouse-adapted PV-1/PV-2 chimeric strain v510 (a Mahoney strain carrying nine amino acids of the VP1 capsid protein from the Lansing strain of PV-2). Mutagenesis of locus 6203 was performed on the original v510 (U-6203-->C) and also on a hybrid v510/Sabin 1 (C-6203-->U) carrying the downstream 1,840 nucleotides of the Sabin 1 genome including the 3Dpol and 3' NC regions. Statistical analysis of disease incidence and time to disease onset in numerous mice inoculated with these strains strongly suggested that nucleotide C-6203 is involved in the attenuation of the Sabin 1 strain. Results also suggested that, among the mutations located in the 3Dpol and 3' NC regions, nucleotide C-6203 may be the principal or the only one to be involved in attenuation in this mouse model. We also found that the effect of C-6203 was weaker than that of nucleotide G-480; the two nucleotides acted independently and may have a cumulative effect on attenuation. The U-6203-->C substitution also appeared to contribute to the thermosensitivity of the Sabin 1 strain.

Amino Acid Sequence↗
PubMed1996

Dengue type 4 virus mutants containing deletions in the 3' noncoding region of the RNA genome: analysis of growth restriction in cell culture and altered viremia pattern and immunogenicity in rhesus monkeys.

The dengue type 4 virus (DEN4) genome contains a 384-nucleotide (nt) 3' noncoding sequence in which the last 81 nt, predicted to form a secondary structure, are thought to be essential for virus replication. Immediately upstream of the secondary structure, short RNA sequences that are conserved among mosquito-borne flaviviruses have been identified. A series of deletions that range from 30 to 262 nt were introduced into this upstream region of full-length DEN4 cDNA to create viable deletion mutants, some of which might prove to be useful for inclusion in a live attenuated virus vaccine. When studied by an infectious-center assay, most full-length RNA transcripts of the deletion constructs exhibited reduced infectivity when transfected into simian LLC-MK2 cells compared with the full-length RNA transcripts of wild-type parental virus. Deletion mutations that extended as far as the 5' boundary of the 3' noncoding region and whose 3' boundary did not extend beyond the last 113 nt of the 3' end were viable. With the exception of mutant 3'd 303-183, which contained a deletion of nt 303 to 183 from the 3' terminus, deletion mutants produced plaques that appeared late on simian LLC-MK2 cells or exhibited a small-plaque morphology on mosquito C6/36 cells compared with the wild-type virus. These mutants also replicated less efficiently and attained a lower titer in LLC-MK2 cells than parental wild-type virus. Significantly, mutant 3'd 303-183 grew to a high titer and was least restricted in growth. Mutant 3'd 303-183 and four other moderately to severely restricted mutants were selected for evaluation of infectivity and immunogenicity in rhesus monkeys. There was a suggestion that occurrence and duration of viremia were reduced for some of the deletion mutants compared with the wild-type virus. However, more convincing evidence for attenuation of some of the mutants was provided by an analysis of antibody response to infection. Mutant 3'd 303-183 induced an antibody response equivalent to that stimulated by wild-type virus, whereas other mutants induced low to moderate levels of antibodies, as measured by radioimmunoprecipitation and virus neutralization. The immunogenicity of these 3' DEN4 deletion mutants in monkeys appeared to correlate with their efficiency of growth in simian LLC-MK2 cells. One or more mutants described in this paper may prove to be useful for immunization of humans against disease caused by dengue virus.

Animals↗