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F Gonzalez-Scarano

Publications and source records attributed to F Gonzalez-Scarano.

At least 55 records · Page 3Linked to original sources
PubMed1990

Neuroattenuated bunyavirus variant: derivation, characterization, and revertant clones.

A neuroattenuated variant bunyavirus, designated RFC/25B.5 (B.5), was selected by serial passage of a reassortant clone (RFC virus) of a California serogroup virus in BHK-21 cells, followed by plaque purification of that passaged stock. Based on its virulence index (ratio of PFU/50% lethal dose), clone B5 was over 40,000-fold less virulent than its unpassaged RFC parent after intracerebral (i.c.) inoculation into adult mice. Clone B.5 also exhibited markedly reduced neuroinvasiveness after subcutaneous injection into neonatal mice, although it retained its ability to replicate and kill suckling mice after i.c. injection. A murine neuroblastoma line (NA cells) can be used as an in vitro surrogate for the adult mouse brain, since clone B.5 replicated to at least 1,000-fold-lower titers in NA cells than did several neurovirulent California serogroup viruses. Clone B.5 replicated in BHK-21 cells at 37 degrees C to titers similar to those achieved by other California serogroup viruses but was temperature sensitive (ts) since its replication was markedly restricted at 38.9 degrees C. Ten ts revertant clones of B.5 virus were selected at 38.9 degrees C, and all of them lost their ts phenotype and regained the ability to replicate to high titer in NA cells and to kill adult mice after i.c. injection. Clone B.5 is the first described California serogroup virus which is truly attenuated after i.c. inoculation, and its availability will permit genetic analysis of bunyavirus neurovirulence.

Animals↗
PubMed1990

Macrophage-tropic strains of human immunodeficiency virus type 1 utilize the CD4 receptor.

To characterize the role of CD4 in human immunodeficiency virus type 1 (HIV-1) infection of macrophages, we examined the expression of CD4 by primary human monocyte-derived macrophages and studied the effect of recombinant soluble CD4 and anti-CD4 monoclonal antibodies on HIV-1 infection of these cells. Immunofluorescence and Western blot (immunoblot) studies demonstrated that both monocytes and macrophages display low levels of surface CD4, which is identical in mobility to CD4 in lymphocytes. Recombinant soluble CD4 and the anti-CD4 monoclonal antibody Leu3a blocked infection of macrophages by three different macrophage-tropic HIV isolates, and the cytopathic effects of HIV-1 infection were similarly prevented. Dose-response experiments using a prototype isolate which replicates in both macrophages and T lymphocytes showed that recombinant soluble CD4 inhibited infection of macrophages more efficiently than in lymphocytes. These results indicate that CD4 is the dominant entry pathway for HIV-1 infection of macrophages. In addition, recombinant soluble CD4 effectively blocks HIV-1 infection by a variety of macrophage-tropic strains and thus has the potential for therapeutic use in macrophage-dependent pathogenesis in HIV disease.

Antibodies, Monoclonal↗
PubMed1989

Human choroid plexus cells can be latently infected with human immunodeficiency virus.

The human immunodeficiency virus (HIV) penetrates the central nervous system, particularly the cerebrospinal fluid, early in the course of HIV infection, and may cause a progressive encephalopathy in patients prior to the development of the acquired immunodeficiency syndrome. Neither the specific mechanism for penetration of the virus into the central nervous system nor the pathophysiological basis for these abnormalities is well understood. We cultured cells from the choroid plexus of 3 individuals who died of causes unrelated to the acquired immunodeficiency syndrome and demonstrated that these cells can be infected with type 1 HIV. Infection of cells of the choroid plexus may provide an initial route of entry of HIV into the cerebrospinal fluid and, together with the macrophage, a route of entry into the brain.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Human immunodeficiency virus can infect CD4-negative human fibroblastoid cells.

Certain human immunodeficiency virus (HIV) strains were shown to infect human fibroblastoid cells. Replication was demonstrated only by coculturing normal peripheral blood mononuclear cells or human T-lymphotropic virus type 1-transformed T-cell lines with the infected human cells. This infection of human fibroblastoid cells did not involve the CD4 molecule and did not have the properties of endocytosis. Human sera could be distinguished by their ability to neutralize HIV infection of the fibroblastoid versus human T-cell lines. These observations demonstrate further that other mechanisms for viral entry, besides CD4 binding, must be considered for HIV. They also indicate the wide cellular host range and heterogeneity of HIV strains. The possibility that fibroblastoid cells serve as a reservoir for the AIDS virus and are involved in connective tissue disorders of infected individuals merits attention.

Antibodies, Monoclonal↗
PubMed1989

The large viral RNA segment of California serogroup bunyaviruses encodes the large viral protein.

Reassortant bunyaviruses derived from two members of the California serogroup (La Crosse/original and Tahyna/181-57) viruses were used to demonstrate that the large Mr viral protein (L) is encoded by the L RNA segment. Radiolabelled viral proteins were analysed by discontinuous SDS-PAGE. The L protein of La Crosse virus was observed to migrate ahead of its Tahyna virus counterpart when electrophoresed through a 5% acrylamide resolving gel. Among the reassortant viruses, the L protein phenotype segregated with the viral L RNA segment. After confirming the genotype of the viruses used in this study, it was concluded that the L RNA species of California serogroup viruses codes for the L protein, the presumed viral polymerase.

Animals↗
PubMed1989

CD4-independent infection of human neural cells by human immunodeficiency virus type 1.

A number of studies have indicated that central nervous system-derived cells can be infected with human immunodeficiency virus type 1 (HIV-1). To determine whether CD4, the receptor for HIV-1 in lymphoid cells, was responsible for infection of neural cells, we characterized infectable human central nervous system tumor lines and primary fetal neural cells and did not detect either CD4 protein or mRNA. We then attempted to block infection with anti-CD4 antibodies known to block infection of lymphoid cells; we noted no effect on any of these cultured cells. The results indicate that CD4 is not the receptor for HIV-1 infection of the glioblastoma line U373-MG, medulloblastoma line MED 217, or primary human fetal neural cells.

Antibodies, Viral↗
PubMed1988

Multiple sclerosis: serial study of gadolinium-enhanced MR imaging.

Thirteen patients with definite multiple sclerosis (MS), studied 16-24 months previously with magnetic resonance (MR) imaging with and without enhancement by intravenously administered gadolinium diethylenetriaminepentaacetic acid (DTPA) dimeglumine, were reexamined with a similar protocol. Assessment of enhancement and clinical activity in both studies revealed that enhancement was observed in 13 of 14 cases in which clinical activity had changed within 4 weeks of the study and thus appeared more sensitive than clinical examination in determining active disease. The 3-minute postinjection, short repetition time image (TR) was the most efficient for depicting enhancement. Enhancing lesions (active plaques) arose from previously hyper- or isointense regions on long TR images. Previously active lesions reverted to areas of iso- or hyperintensity on long TR images. Serial comparison of long TR images in this population reveals a decrease in high-intensity lesions on long TR images in some cases and an increase in others. The findings of high-intensity regions on long TR images and previously enhancing lesions both becoming isointense suggests that transient inflammatory changes with concomitant edema without demyelination and/or with significant remyelination may occur in some MS lesions. MS lesions are dynamic; both active and inactive lesions may show dramatic change on longitudinal MR imaging studies.

Adult↗
PubMed1988

Organization of the middle RNA segment of snowshoe hare Bunyavirus.

The genetic organization of the M RNA segment of snowshoe hare (SSH) virus, a member of the Bunyavirus genus of the family Bunyaviridae, has been determined. The middle (M) RNA segment has a single open reading frame (ORF) of 1441 amino acids. We have used amino- and carboxy-terminus sequencing and synthetic peptides to map proteins within the ORF. The order of the proteins translated from the single large open reading frame is G2, NSm, G1. The G2 protein extends from amino acids 14 to 299. The molecule is 286 residues long, with a computed nonglycosylated molecular weight of 31,973 Da. It is preceded by a cleaved 13 amino acid signal sequence. G2 includes a long highly hydrophobic sequence and contains three potential N-linked glycosylation sites. The G1 protein occupies the C-terminal end of the open reading frame from amino acids 474 to 1441 (968 amino acid residues) and has a computed nonglycosylated, molecular weight of 108,981 kDa. It has two potential N-linked glycosylation sites, and a potential transmembrane region followed by a potential cytoplasmic domain at the C-terminal end. If membrane associated it has an orientation of N-terminus outer, C-terminus inner. Limited trypsin digestion removes a 33-kDa fragment from the N-terminal end, leaving a virion-associated truncated G1 molecule (amino acids 762 to 1441) with a single N-linked glycosylation site. Between the G2 and G1 molecules there are 174 amino acids, sufficient to code for 19 kDa of protein. Some antibodies raised against peptides within this region react with proteins of 11 kDa (NSm) and 10 kDa present in infected cell lysates, but the exact relationship of these proteins to the open reading frame remains to be determined.

Amino Acid Sequence↗
PubMed1987

A G1 glycoprotein epitope of La Crosse virus: a determinant of infection of Aedes triseriatus.

Arthropod-borne viruses (arboviruses) have specific vector-vertebrate host cycles in nature. The molecular basis of restriction of virus replication to a very limited number of vector species is unknown, but the present study suggests that viral attachment proteins are important determinants of vector-virus interactions. The principal vector of La Crosse (LAC) virus is the mosquito Aedes triseriatus, and LAC virus efficiently infects the mosquito when ingested. However, a variant (V22) of LAC virus, which was selected by growing the virus in the presence of a monoclonal antibody, was markedly restricted in its ability to infect Ae. triseriatus when it was ingested. Only 15% of the mosquitoes that ingested V22 became infected and 5% of these developed disseminated infections. In contrast, 89% of the mosquitoes that ingested LAC became infected and 74% developed disseminated infections. When V22 was passed three times in mosquitoes by feeding, a revertant virus, V22M3, was obtained that infected 85% of Ae. triseriatus ingesting this virus. In addition, V22M3 regained the antigenic phenotype and fusion capability of the parent LAC virus. These results suggest that the specificity of LAC virus-vector interactions is markedly influenced by the efficiency of the fusion function of the G1 envelope glycoprotein operating at the midgut level in the arthropod vector.

Aedes↗
PubMed1987

Multiple sclerosis disease activity correlates with gadolinium-enhanced magnetic resonance imaging.

Magnetic resonance imaging provides a method of visualizing multiple sclerosis plaques, but the age and activity of these plaques cannot be determined with routine magnetic resonance images. Gadolinium DTPA is a paramagnetic contrast agent that does not cross an intact blood-brain barrier. We studied 16 patients with multiple sclerosis, using magnetic resonance imaging, gadolinium-enhanced magnetic resonance imaging, and computed tomographic scans. Gadolinium enhancement of multiple sclerosis plaques correlated with the clinical activity of the disease and corresponded anatomically with the symptoms and signs. We conclude that gadolinium enhancement of magnetic resonance images is a promising tool in the investigation of multiple sclerosis lesions and that it may provide a method for objective follow-up in clinical trails.

Adult↗
PubMed1987

Molecular pathogenesis of neurotropic viral infections.

Classical virologists defined a number of viruses that affect the nervous system and identified tissue tropism, extraneural replication, and viremia as important parameters that determine whether viral infections will affect the central nervous system. Molecular techniques are expanding this knowledge by permitting us to relate specific genes and gene products to two defined phenotypes: neuroinvasion and neurovirulence. Two converging situations make this knowledge particularly useful: (1) the development of antiviral drugs and subunit vaccines, which mandate that pathogenesis be related to specific regions of the viral genome; and (2) the expanding problem of central nervous system infections in immunodeficient states.

Cell Survival↗
PubMed1987

Sequence similarities between human immunodeficiency virus gp41 and paramyxovirus fusion proteins.

Cell fusion is a characteristic cytopathic effect induced by the human immunodeficiency virus (HIV) that leads to the formation of syncytia between infected lymphocytes. Although this process has been shown to occur following the specific binding of the 110-120 kD externalized envelope molecule of the virus with the CD4 glycoprotein, the region of the HIV envelope that directly mediates cell fusion is unknown. In an attempt to identify this fusion domain, we compared the amino acid sequences from the envelope molecules of several HIV isolates to the fusion proteins of paramyxoviruses. We found that the amino terminal region of the HIV transmembrane protein gp41 had a striking degree of similarity with the fusion domain of the respiratory syncytial virus. Moreover, similar sequences were noted in the fusion proteins of other paramyxoviruses and the transmembrane envelope proteins of a variety of lentiviruses suggesting that a functional relationship exists between these glycoproteins. This finding indicates that the amino terminal region of the HIV gp41 molecule may mediate cell fusion for this virus, and could be an important target in the design of immunologic strategies for the prevention of HIV infection in vivo.

Amino Acid Sequence↗
PubMed1986

Biological studies of the fusion function of California serogroup Bunyaviruses.

Like other enveloped viruses, La Crosse virus is capable of inducing membrane fusion after exposure to mild acid. This function is known to have biological significance at the level of the whole organism, since it has been related to infection in a mouse model. In this report the process of fusion-from-within (FFWI) for LAC and other members of the California serogroup of Bunyaviruses is characterized. Like fusion-from-without, FFWI is dependent on pH, temperature, and number of virus particles present in the supernatant of fusing cells. Electron micrographs demonstrate that LAC mediated cell membrane fusion is a rapid, multi-point event, and that other than fusion of their plasma membranes, the cells do not show any morphological change. In agreement with theory, lysosomotropic agents were capable of inhibiting La Crosse virus infection. This inhibition was not due to non-specific toxic effects on infected cells. Finally, fusion studies of other California serogroup members revealed minor differences in the pH of fusion induction in some strains. These differences were consistent with the known subtyping within the serogroup.

Animals↗
PubMed1986

Virulence of La Crosse virus is under polygenic control.

To identify which RNA segments of the California serogroup bunyaviruses determine virulence, we prepared reassortant viruses by coinfecting BHK-21 cells with two wild-type parents, La Crosse/original and Tahyna/181-57 viruses, which differed about 30,000-fold in virulence. The progeny clones were screened by polyacrylamide gel electrophoresis to ascertain the phenotype of the M and S RNA segments, and RNA-RNA hybridization was used to determine the genotype of selected clones. Two or three clones of each of the six possible reassortant genotypes were characterized quantitatively for neuroinvasiveness by determining the PFU/50% lethal dose (LD50) ratio after subcutaneous injection into suckling mice. The reassortants fell into two groups. (i) Six of seven reassortants with a La Crosse M RNA segment were as virulent as the parent La Crosse virus (about 1 PFU/LD50); the one exception was strikingly different (about 1,000 PFU/LD50) and probably represents a spontaneous mutant. (ii) The seven reassortants with a Tahyna M RNA segment were about 10-fold more virulent than the parent Tahyna virus (median 1,600 PFU/LD50 for reassortants and 16,000 PFU/LD50 for Tahyna virus). A comparative pathogenesis study in suckling mice of one reassortant virus and the parent Tahyna virus confirmed the greater neuroinvasiveness of the reassortant virus. From these data it was concluded that the M RNA segment was the major determinant of virulence, but that the other two gene segments could modulate the virulence of a nonneuroinvasive California serogroup virus.

Animals↗
PubMed1986

Multiple sclerosis: gadolinium enhancement in MR imaging.

Magnetic resonance (MR) images--both nonenhanced and enhanced with gadolinium DTPA/dimeglumine (Gd)--were compared with high-iodine (88.1 g I) computed tomographic (HICT) scans in demonstrating lesions in 15 patients known to have multiple sclerosis (MS). T1-weighted, mixed (T1, proton density, and T2), and T2-weighted MR pulse sequences were used. More than 20 lesions in each of 14 patients were demonstrated by pre-Gd mixed images and T2WI. Nine patients had clinical symptoms of active disease. Gd-enhanced T1WI showed at least one lesion that appeared to correspond with newly reported symptoms or signs. In addition, three clinically stable patients showed enhancement. Enhancement was best seen on 3-minute T1WI. HICT scans showed enhancement in four of the nine patients with active disease and in none of five clinically stable patients. Gd-enhanced MR imaging appears to be more sensitive than HICT in the detection of the transient abnormalities of the blood-brain barrier that occur in patients with active MS and appears capable of distinguishing active lesions that may correspond to the anatomic regions responsible for abnormal clinical findings.

Adult↗
PubMed1985

Epitopes of the G1 glycoprotein of La Crosse virus form overlapping clusters within a single antigenic site.

Antigenic sites on the G1 glycoprotein of La Crosse bunyavirus were defined by constructing a panel of neutralizing and nonneutralizing monoclonal antibodies (F. Gonzalez-Scarano, R. E. Shope, C. H. Calisher, and N. Nathanson (1982), Virology 120, 42-53). To analyze the relationship between the individual epitopes delineated by monoclonal antibodies, 11 neutralizing antibodies were used to select variant viruses. These variant viruses were tested against the panel of anti-G1 protein monoclonal antibodies by neutralization and by ELISA. The neutralization tests assigned the 11 epitopes to five groups, consisting of 6, 2, 1, 1, and 1 epitopes. ELISA tests gave a similar pattern, but also demonstrated interrelationships between four of the five epitope groups, suggesting that there may be a single immunodominant antigenic site on the G1 protein. When eight nonneutralizing anti-G1 monoclonal antibodies were tested in ELISA, they fell into three of the five epitope groups defined by neutralization; there was no evidence of a separate noneutralizing antigenic site on the G1 protein.

Antibodies, Monoclonal↗