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Biomedical subjects

Y Guan

Publications and source records attributed to Y Guan.

At least 73 records · Page 4Linked to original sources
PubMed2002

Emergence of multiple genotypes of H5N1 avian influenza viruses in Hong Kong SAR.

Although A/Hong Kong/156/97 (H5N1/97)-like viruses associated with the "bird flu" incident in Hong Kong SAR have not been detected since the slaughter of poultry in 1997, its putative precursors continue to persist in the region. One of these, Goose/Guangdong/1/96 (H5N1 Gs/Gd)-like viruses, reassorted with other avian viruses to generate multiple genotypes of H5N1 viruses that crossed to chickens and other terrestrial poultry from its reservoir in geese. Whereas none of these recent reassortants had acquired the gene constellation of H5N1/97, these events provide insight into how such a virus may have been generated. The recent H5N1 reassortants readily infect and kill chicken and quail after experimental infection, and some were associated with significant mortality of chickens within the poultry retail markets in Hong Kong. Some genotypes are lethal for mice after intra-nasal inoculation and spread to the brain. On this occasion, the early detection of H5N1 viruses in the retail, live poultry markets led to preemptive intervention before the occurrence of human disease, but these newly emerging, highly pathogenic H5N1 viruses provide cause for pandemic concern.

Animals↗
PubMed2002

H5N1 influenza viruses isolated from geese in Southeastern China: evidence for genetic reassortment and interspecies transmission to ducks.

The H5N1 viruses (H5N1/97) associated with the "bird-flu" incident in the Hong Kong SAR have not been isolated since the slaughter of poultry in December 1997 brought that outbreak to an end. Recent evidence points to this virus as having arisen through a reassortment of a number of precursor avian viruses and a virus related to Goose/Guangdong/1/96 (H5N1) (Gs/Gd/96) was the likely donor of the H5 hemagglutinin. We characterize the Goose/Guangdong/1/96-like viruses isolated from geese and ducks imported into Hong Kong in the year 2000. Antigenically and genetically, these recent H5N1 viruses fall into two groups, one mainly associated with geese, and the other, recently transmitted to ducks. Further, viruses isolated from a goose and a duck in December 2000 have acquired NS, PA, M, and PB2 genes from the aquatic avian influenza gene pool through reassortment. For pandemic preparedness, it is important to monitor whether these reassortant viruses have the capacity for interspecies transmission to terrestrial poultry or mammals.

Animals↗
PubMed2002

Molecular changes associated with the transmission of avian influenza a H5N1 and H9N2 viruses to humans.

In order to identify molecular changes associated with the transmission of avian influenza A H5N1 and H9N2 viruses to humans, the internal genes from these viruses were compared to sequences from other avian and human influenza A isolates. Phylogenetically, each of the internal genes of all sixteen of the human H5N1 and both of the H9N2 isolates were closely related to one another and fell into a distinct clade separate from clades formed by the same genes of other avian and human viruses. All six internal genes were most closely related to those of avian isolates circulating in Asia, indicating that reassortment with human strains had not occurred for any of these 18 isolates. Amino acids previously identified as host-specific residues were predominantly avian in the human isolates although most of the proteins also contained residues observed previously only in sequences of human influenza viruses. For the majority of the nonglycoprotein genes, three distinct subgroups could be distinguished on bootstrap analyses of the nucleotide sequences, suggesting multiple introductions of avian virus strains capable of infecting humans. The shared nonglycoprotein gene constellations of the human H5N1 and H9N2 isolates and their detection in avian isolates only since 1997 when the first human infections were detected suggest that this particular gene combination may confer the ability to infect humans and cause disease. J. Med. Virol. 66:107-114, 2002. Published 2002 Wiley-Liss, Inc.

Animals↗
PubMed2002

Molecular evolution of H6 influenza viruses from poultry in Southeastern China: prevalence of H6N1 influenza viruses possessing seven A/Hong Kong/156/97 (H5N1)-like genes in poultry.

The A/teal/Hong Kong/W312/97 (H6N1) influenza virus and the human H5N1 and H9N2 influenza viruses possess similar genes encoding internal proteins, suggesting that H6N1 viruses could become novel human pathogens. The molecular epidemiology and evolution of H6 influenza viruses were characterized by antigenic and genetic analyses of 29 H6 influenza viruses isolated from 1975 to 1981 and 1997 to 2000. Two distinct groups were identified on the basis of their antigenic characteristics. Phylogenetic analysis revealed that all H6N1 viruses isolated from terrestrial poultry in 1999 and 2000 are closely related to A/teal/Hong Kong/W312/97 (H6N1), and the nucleotide sequences of these viruses and of A/Hong Kong/156/97 (H5N1) were more than 96% homologous. The hemagglutinin (HA) of the 1999 and 2000 terrestrial viruses does not have multiple basic amino acids at the site of cleavage of HA1 to HA2; however, a unique insertion of aspartic acid in HA1 between positions 144 and 145 (H3 numbering) was found. The neuraminidase of these terrestrial H6N1 viruses has a deletion of 19 amino acids characteristic of A/Hong Kong/156/97 (H5N1). Evolutionary analysis suggested that these H6N1 viruses coevolved with A/quail/Hong Kong/G1/97-like H9N2 viruses and became more adapted to terrestrial poultry. These terrestrial 1999 and 2000 A/teal/Hong Kong/W312/97 (H6N1)-like viruses, along with the H9N2 viruses, could have been involved in the genesis of the pathogenic H5N1 influenza viruses of 1997. The presence of H6N1 viruses in poultry markets in Hong Kong that possess seven of the eight genes of the A/Hong Kong/156/97 (H5N1) virus raises the following fundamental questions relevant to influenza pandemic preparedness: could the pathogenic H5N1 virus reemerge and could the H6N1 viruses directly cross the species barrier to mammals?

Animals↗
PubMed2002

Changes in gene expression and neuronal phenotype in brain stem pain modulatory circuitry after inflammation.

Recent studies indicate that descending pain modulatory pathways undergo time-dependent changes in excitability following inflammation involving both facilitation and inhibition. The cellular and molecular mechanisms of these phenomena are unclear. In the present study, we examined N-methyl-D-aspartate (NMDA) receptor gene expression and neuronal activity in the rostral ventromedial medulla (RVM), a pivotal structure in pain modulatory circuitry, after complete Freund's adjuvant (CFA)-induced hindpaw inflammation. The reverse transcription polymerase chain reaction analysis indicated that there was an upregulation of mRNAs encoding NMDA receptor subunits in the RVM after inflammation. The increase in the NR1, NR2A, and NR2B receptor mRNAs started at 5 h, maintained for 1-7 days (P < 0.05-0.001) and returned to the control level at 14 days after inflammation. Western blot analysis indicated that the protein translation products of the NR2A subunit were also increased (P < 0.01). In single-unit extracellular recordings, we correlated RVM neuronal activity with the paw withdrawal response in rats with inflammation. We describe these RVM cells as on-, off-, and neutral-like cells because of their similarity to previous studies in which neuronal responses were correlated with tail-flick nocifensive behavior in the absence of inflammation. In contrast to previous studies in the absence of inflammation, using tail flick as a behavioral correlate, fewer off-like cells in naïve animals exhibited a complete pause before the paw withdrawal to a noxious thermal stimulus. The percentage of cells showing a pause of activity after noxious stimulation was further reduced after inflammation (chi(2) P < 0.0001 vs. naïve rats). Continuous neuronal recordings (3-6.5 h) revealed a phenotypic switch of RVM neurons during the development of inflammation: 11/15 neutral-like cells initially unresponsive to noxious stimuli exhibited and maintained response profiles characteristic of pain modulatory neurons (became off-like: n = 5; became on-like: n = 6). Neutral-like cells recorded in noninflamed animals did not show response profile changes during continuous recordings (5-5.5 h, n = 7). A population study (n = 165) confirmed an increase in on- and off-like cells and a decrease in neutral-like cells at 24 h after inflammation as compared with naïve rats (P < 0.001). These results suggest that enhanced NMDA receptor activation mediates time-dependent changes in excitability of RVM pain modulatory circuitry. The functional phenotypic switch of RVM neurons provides a novel mechanism underlying activity-dependent plasticity and enhanced net descending inhibition after inflammation.

Action Potentials↗
PubMed2002

Targeting peroxisome proliferator-activated receptors (PPARs) in kidney and urologic disease.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Three PPAR isoforms, designated PPAR-alpha, beta/delta and -gamma, have been identified and were initially investigated in the tissues along urinary tract because of their known role in regulating lipid-activated gene transcription, lipid metabolism, inflammation and cell proliferation and differentiation. Gene distribution studies suggested that 3 PPAR isoforms are differentially expressed in the kidney. PPAR-alpha is predominantly expressed in renal proximal tubules and medullary thick ascending limbs. PPAR-gamma is mainly localized in renal medullary collecting duct with lower expression in renal glomeruli and renal microvasculature. Unlike PPAR-alpha and -gamma, PPAR-beta/delta is ubiquitously expressed in every segment along the nephron. In ureter and urinary bladder, all PPAR isoforms are mainly localized in urothelium of ureter and bladder. The emerging data have suggested physiological and pathophysiological roles of PPARs in tissues along urinary tract. PPAR-alpha plays a major role in triggering fatty acid utilization and the adaptive response to dietary lipids in the kidney. PPAR-beta/delta contributes to cell survival of renal interstitial cell in medullary hyperosmality. PPAR-gamma is involved in regulating renal hemodynamic and water and sodium transport. Furthermore, it also participates in the pathogenesis of glomerulopathy, antidiabetic thiazolidinedione-related water and sodium retention and renal, bladder and prostate carcinomas. PPARs may serve as potential therapeutic targets for certain diseases along urinary tract including glomerulosclerosis, diabetic nephropathy and kidney, prostate and bladder tumors.

Animals↗
PubMed2001

Toxicokinetics of tremorogenic natural products, harmane and harmine, in male Sprague-Dawley rats.

Tremorogenic beta-carboline alkaloids are present in foodstuffs and beverages. Acute exposure to beta-carboline derivatives causes severe tremor; however, the disposition of these dietary contaminants remains unclear. This study was performed to evaluate toxicokinetics of harmane and harmine, two major beta-carboline alkaloids, in rats. Blood concentrations of both toxicants were quantified by high-performance liquid chromatography (HPLC). Following an intravenous injection (0.5 mg/kg), the concentration-time profiles of harmane or harmine fit well with a two-compartment model. While both compounds had comparable elimination t 1/2beta (24 and 26 min for harmane and harmine, respectively), the systemic clearance (CLs) for harmine (103.2 ml/kg/ml) was two times greater than that for harmane (52.2 ml/kg/ml). Accordingly, the area under the blood concentration-time curve (AUC) in harmane-treated rats was 2.7-fold greater than that in harmine-treated rats. Harmine appeared to distribute to tissues better than harmane, with a larger volume of distribution (V,d) (3.9 and 1.6 L/kg for harmine and harmane, respectively). After an oral dose (20 mg/kg), the absolute bioavailability (F) was 19% for harmane and 3% for harmine. Harmane was absorbed more slowly (lower Ka), yet more completely (higher Cmax' AUC, and F) than harmine. An oral administration of harmane resulted in blood harmine whose formation accounted for 13% of the ingested harmane, indicating a biotransformation of harmane to harmine. These results suggest that harmane is absorbed into the systemic circulation more completely than harmine. Upon entering the body, harmane can be metabolized to form harmine; the latter may better distribute to the tissue compartment.

Administration, Oral↗
PubMed2001

The synthesis, discovery, and development of a highly promising class of microtubule stabilization agents: curative effects of desoxyepothilones B and F against human tumor xenografts in nude mice.

We have evaluated two synthetic epothilone analogues lacking the 12,13-epoxide functionality, 12,13-desoxyepothilone B (dEpoB), and 12,13-desoxyepothilone F (dEpoF). The concentrations required for 50% growth inhibition (IC(50)) for a variety of anticancer agents were measured in CCRF-CEM/VBL1000 cells (2,048-fold resistance to vinblastine). By using dEpoB, dEpoF, aza-EpoB, and paclitaxel, the IC(50) values were 0.029, 0.092, 2.99, and 5.17 microM, respectively. These values represent 4-, 33.5-, 1,423- and 3,133-fold resistance, respectively, when compared with the corresponding IC(50) in the parent [nonmultiple drug-resistant (MDR)] CCRF-CEM cells. We then produced MDR human lung carcinoma A549 cells by continuous exposure of the tumor cells to sublethal concentrations of dEpoB (1.8 yr), vinblastine (1.2 yr), and paclitaxel (1.8 yr). This continued exposure led to the development of 2.1-, 4,848-, and 2,553-fold resistance to each drug, respectively. The therapeutic effect of dEpoB and paclitaxel was also compared in vivo in a mouse model by using various tumor xenografts. dEpoB is much more effective in reducing tumor sizes in all MDR tumors tested. Analysis of dEpoF, an analog possessing greater aqueous solubility than dEpoB, showed curative effects similar to dEpoB against K562, CCRF-CEM, and MX-1 xenografts. These results indicate that dEpoB and dEpoF are efficacious antitumor agents with both a broad chemotherapeutic spectrum and wide safety margins.

Animals↗
PubMed2001

On the interactivity of complex synthesis and tumor pharmacology in the drug discovery process: total synthesis and comparative in vivo evaluations of the 15-aza epothilones.

The total syntheses of 12,13,15-desoxy-15(S)-aza-epothilone B (aza-dEpoB; dEpoB-lactam) and 12,13,15-desoxy-15(R)-aza-epothilone B (15-epi-aza-dEpoB; 15-epi-dEpoB-lactam) have been accomplished via a highly convergent strategy. We have also successfully oxidized 12,13,15-desoxy-15(S)-aza-epothilone B to aza-epothilone B (aza-EpoB; EpoB-lactam). Aza-epothilone B has been advanced to phase I clinical trials by the Bristol-Myers Squibb group. Our synthesis is efficient and was amenable to the production of significant quantities of these lactams. Using our fully synthetically derived lactams, in vitro and in vivo studies were conducted in comparison with advanced clinical candidates, 12,13-desoxyepothilone B and 12,13-desoxyepothilone F, also derived by total synthesis.

Animals↗
PubMed2001

Insights into long-range structural effects on the stereochemistry of aldol condensations: a practical total synthesis of desoxyepothilone F.

A processable total synthesis of a potent antitumor agent, desoxyepothilone F (dEpoF, 21-hydroxy-12,13-desoxyepothilone B, 21-hydroxyepothilone D), has been accomplished. The route is highly convergent. The new technology has also been applied to a total synthesis of 12,13-desoxyepothilone (dEpoB). The crucial point of departure from previous syntheses of dEpoB and dEpoF involves presentation of the C1-C11 sector for Suzuki coupling with C3 in reduced form. Hitherto, the required S stereochemistry at C3 had been implemented via reduction of a keto function after Suzuki coupling. Whereas that chemistry worked quite well in a synthesis of dEpoB, it was not transferable to a high-yielding synthesis of dEpoF. The reduction of the keto group at C3 via a Noyori protocol after Suzuki coupling had proved to be very difficult. In our current approach, two consecutive aldol reactions are used to fashion the acyl sector. In the first aldol condensation, C6 becomes attached to C7. Following protection at C7, a two-carbon acetate equivalent is used to join C2 and C3 with very high asymmetric induction at C3. Only after this center has been implemented is the Suzuki reaction conducted. This major advance allowed us to synthesize dEpoF in a straightforward fashion. These findings found ready application in the total synthesis of dEpoB. Another part of the study involved analysis of the factors associated with aldol condensations joining C6 to C7. In the work described herein, the consequences of the status of C3 in promoting the C6-C7 aldol coupling are probed in detail. Dramatic stereochemical long-range effects uncovered during the study are described, and a working model to explain these effects has emerged.

Antineoplastic Agents↗
PubMed2001

Universal primer set for the full-length amplification of all influenza A viruses.

To systematically identify and analyze the 15 HA and 9 NA subtypes of influenza A virus, we need reliable, simple methods that not only characterize partial sequences but analyze the entire influenza A genome. We designed primers based on the fact that the 15 and 21 terminal segment specific nucleotides of the genomic viral RNA are conserved between all influenza A viruses and unique for each segment. The primers designed for each segment contain influenza virus specific nucleotides at their 3'-end and non-influenza virus nucleotides at the 5'-end. With this set of primers, we were able to amplify all eight segments of N1, N2, N4, N5, and N8 subtypes. For N3, N6, N7, and N9 subtypes, the segment specific sequences of the neuraminidase genes are different. Therefore, we optimized the primer design to allow the amplification of those neuraminidase genes as well. The resultant primer set is suitable for all influenza A viruses to generate full-length cDNAs, to subtype viruses, to sequence their DNA, and to construct expression plasmids for reverse genetics systems.

Child↗
PubMed2001

Effects of six antihypertensive drugs on blood pressure and hypothalamic GABA content in spontaneously hypertensive rats.

In order to investigate the effects of antihypertensive drugs on blood pressure and gamma-amino butyric acid (GABA) content in the hypothalamus and the possible relationship between blood pressure decrease and GABA content changes, blood pressure and GABA contents after chronic (20 weeks) treatments of nitrendipine, atenolol, captopril, hydrochlorothiazide, dihydralazine and prazosin were studied in spontaneously-hypertensive rats (SHR). The acute and subacute (1 week) effects of nitrendipine on GABA contents was also observed in SHR. It was found that 20 week treatments with six different antihypertensive agents produced a decrease in systolic blood pressure and an increase in GABA content. The blood pressure level was significantly correlated with GABA content in the hypothalamus, but not with that in the cortex. Acute treatment with a single dose of nitrendipine, did not alter GABA content. Bicuculline, a GABA receptor antagonist, did not attenuate the hypotensive effect of nitrendipine. In conclusion, chronic treatments by different antihypertensive agents produced an increase of hypothalamic GABA content and a decrease of blood pressure. The increase of GABA content induced by nitrendipine seems likely to be secondary to blood pressure decrease.

Animals↗
PubMed2001

Peroxisome proliferator-activated receptors (PPARs): novel therapeutic targets in renal disease.

Peroxisome proliferator-activated receptors (PPARs): Novel therapeutic targets in renal disease. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-dependent transcription factors. PPARs play an important role in the general transcriptional control of numerous cellular processes, including lipid metabolism, glucose homeostasis, cell cycle progression, cell differentiation, inflammation and extracellular matrix remodeling. Three PPAR isoforms, designated PPARalpha, PPARbeta and PPARgamma, have been cloned and are differentially expressed in several tissues including the kidney. PPARalpha primary regulates lipid metabolism and modulates inflammation. PPARalpha is the molecular target of the hypolipidemic fibrates including bezafibrate and clofibrate. PPARbeta participates in embryonic development, implantation and bone formation. PPARgamma is a key factor in adipogenesis and also plays an important role in insulin sensitivity, cell cycle regulation and cell differentiation. Antidiabetic thiazolidinediones (TZDs) such as troglitazone and rosiglitazone are specific ligands of PPARgamma, and this interaction is responsible for the insulin-sensitizing and hypoglycemic effect of these drugs. The kidney has been shown to differentially express all PPAR isoforms. PPARalpha is predominantly expressed in proximal tubules and medullary thick ascending limbs, while PPARgamma is expressed in medullary collecting ducts, pelvic urothelium and glomerular mesangial cells. PPARbeta is ubiquitously expressed at low levels in all segments of nephron. Accumulating data has begun to emerge suggesting physiological and pathophysiological roles of PPARs in several tissues including the kidney. The availability of PPAR-selective agonists and antagonists may provide a new approach to modulate the renal response to diseases including glomerulonephritis, glomerulosclerosis and diabetic nephropathy.

Animals↗
PubMed2001

Structure-activity of inhibition of HIV-1 integrase and virus replication by G-quartet oligonucleotides.

As novel anti-HIV agents, the G-tetrad-forming oligonucleotides have been explored for their structure-activity relations with regard to inhibition of integrase (IN) (N. Jing, Expert Opin. Investig. Drugs (2000) 9, 1777-1785). We have now developed two families of G-quartet oligonucleotides: T40217-T40222, with potential formation of a tail-to-tail G-quartet dimer, and T40224-T40227, with phosphorothioate (PT) linkages in the guanine loops. The results obtained from biophysical measurements and the assays of the inhibition of HIV-1 IN and virus replication demonstrated that an increase in the length of the G-quartet structure from a monomer (15A) to a tail-to-tail dimer (47A) does not distinctly disrupt the inhibition of HIV-1 IN activity or the inhibition of HIV-1 replication in cell cultures. G-quartet oligonucleotides were observed to induce molecular aggregation of HIV-1 IN and interrupt the binding of viral DNA to HIV-1 IN. Also, PT substitutions did not confer any advantages compared with the regular phosphodiesters for the inhibition of HIV-1 replication by intramolecular G-quartets. The G-quartet motif is the primary requirement for the remarkable nuclease resistance and pronounced biological efficacy of these oligonucleotides.

Cell Line↗
PubMed2001

Hydrophobic amino acids in the human immunodeficiency virus type 1 p2 and nucleocapsid proteins can contribute to the rescue of deleted viral RNA packaging signals.

An RNA fragment of 75 nucleotides, which is located between the primer binding site and the 5' major splice donor site in human immunodeficiency virus type 1, has been shown to participate in specific encapsidation of viral RNA. Compensation studies have identified two second-site mutations, namely, MP2 (a T12I substitution in p2) and MNC (a T24I substitution in the nucleocapsid [NC] protein) that were involved in the rescue of various deletions in the aforementioned RNA region (i.e., BH-D1, BH-D2, and BH-LD3). To study whether the MP2 and MNC point mutations exert their compensatory effects in a cis manner, production of Gag proteins was blocked by insertion of stop codons into LD3, LD3-MP2-MNC, and wild-type BH10 such that the constructs generated, i.e., LD3-DG, LD3-MP2-MNC-DG, and BH-DG, only provided RNA transcripts for packaging. The results of cotransfection experiments showed that the LD3-MP2-MNC-DG viral RNA was packaged as inefficiently as LD3-DG; in contrast, BH-DG was efficiently packaged. Therefore, nucleotide substitutions in MP2 and MNC did not act in a cis manner to correct the packaging deficits in LD3. Next, we deliberately changed the T12 in p2 or the T24 in the NC to each of 19 other amino acids. We found that amino acids with long hydrophobic side chains, i.e., V, L, I, and M, were favored at either position 12 in p2 or at position 24 in NC to compensate for the above-mentioned deletions. Further studies showed that only a few amino acids could not be used at these two sites by the wild-type virus due to decreased RNA levels in the virion or abnormal Gag protein processing. In this case, W, D, and E could not substitute for T12 in p2, and S, D, and N could not substitute for T24 in NC, without affecting viral infectivity. Therefore, the long hydrophobic side chains of V, L, I, and M are necessary for these amino acids to rescue the BH-D1, BH-D2, and BH-LD3 mutated viruses.

Amino Acids↗
PubMed2001

Cocirculation of avian H9N2 and contemporary "human" H3N2 influenza A viruses in pigs in southeastern China: potential for genetic reassortment?

Pigs are permissive to both human and avian influenza viruses and have been proposed to be an intermediate host for the genesis of pandemic influenza viruses through reassortment or adaptation of avian viruses. Prospective virological surveillance carried out between March 1998 and June 2000 in Hong Kong, Special Administrative Region, People's Republic of China, on pigs imported from southeastern China, provides the first evidence of interspecies transmission of avian H9N2 viruses to pigs and documents their cocirculation with contemporary human H3N2 (A/Sydney/5/97-like, Sydney97-like) viruses. All gene segments of the porcine H9N2 viruses were closely related to viruses similar to chicken/Beijing/1/94 (H9N2), duck/Hong Kong/Y280/97 (H9N2), and the descendants of the latter virus lineage. Phylogenetic analysis suggested that repeated interspecies transmission events had occurred from the avian host to pigs. The Sydney97-like (H3N2) viruses isolated from pigs were related closely to contemporary human H3N2 viruses in all gene segments and had not undergone genetic reassortment. Cocirculation of avian H9N2 and human H3N2 viruses in pigs provides an opportunity for genetic reassortment leading to the emergence of viruses with pandemic potential.

Animals↗
PubMed2001

Partial restoration of replication of simian immunodeficiency virus by point mutations in either the dimerization initiation site (DIS) or Gag region after deletion mutagenesis within the DIS.

We used the simian immunodeficiency virus (SIV) molecular clone SIVmac239 to generate a deletion construct, termed SD2, in which we eliminated 22 nucleotides at positions +398 to +418 within the putative dimerization initiation site (DIS) stem. This SD2 deletion severely impaired viral replication, due to adverse effects on the packaging of viral genomic RNA, the processing of Gag proteins, and viral protein patterns. However, long-term culture of SD2 in either C8166 or CEMx174 cells resulted in restoration of replication capacity, due to two different sets of three compensatory point mutations, located within both the DIS and Gag regions. In the case of C8166 cells, both a K197R and a E49K mutation were identified within the capsid (CA) protein and the p6 protein of Gag, respectively, while the other point mutation (A423G) was found within the putative DIS loop. In the case of CEMx174 cells, two compensatory mutations were present within the viral nucleocapsid (NC) protein, E18G and Q31K, in addition to the same A423G substitution as observed with C8166 cells. A set of all three mutations was required in each case for restoration of replication capacity, and either set of mutations could be substituted for the other in both the C8166 and CEMx174 cell lines.

Base Sequence↗