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Biomedical subjects

J S Porterfield

Publications and source records attributed to J S Porterfield.

At least 37 records · Page 2Linked to original sources
PubMed1984

Flavivirus infection enhancement in macrophages: radioactive and biological studies on the effect of antibody on viral fate.

35S-labelled West Nile virus was used in radioactive binding, internalization and degradation studies in the macrophage cell line P388D1 in the absence or presence of various concentrations of antiviral antibody. Proteases were used to help distinguish between intracellular and extracellular (bound) virus. It was found that the enhancement in viral infectivity that occurs in the presence of subneutralizing concentrations of antiviral antibody was caused by (i) increased binding of virus to the cell surface and (ii) a higher specific infectivity of antibody-opsonized virus particles, apparently due to a more efficient internalization process. In contrast, little difference was found in the rate of internalization and intracellular degradation for virus particles that did enter the cells. Lysosomotropic amines were capable of markedly inhibiting viral replication in P388D1 cells at an early stage of infection both in the absence and presence of subneutralizing concentrations of antibody, although antibody-mediated enhancement of viral replication remained.

Animals↗
PubMed1983

Complement receptor mediates enhanced flavivirus replication in macrophages.

Evidence is presented that M phi complement receptors (CR3) mediate IgM-dependent enhancement of flavivirus replication in the presence of complement. Enhancement is blocked by pretreatment of macrophages with monoclonal antibody Ml/70, which inhibits CR3 binding, but not by pretreatment with monoclonal antibody 2.4G2, which inhibits FcR binding.

Animals↗
PubMed1983

Comparison of P388D1 mouse macrophage cell line and human monocytes for assay of dengue-2 infection-enhancing antibodies.

Tissue culture-adapted dengue 2 virus (DEN 2), strain 16681, exhibits antibody-dependent enhancement of infection (ADE) in P388D1 cells, a mouse macrophage-like cell line. ADE is dependent upon maintaining DEN 2 multiplicity of infection at between 0.1 and 0.001, and can be simply measured in multi-well plastic plates. The assay uses either trypsinized or non-trypsinized P388D1 cells at 5 x 10(5) cells per ml, an appropriate dilution of DEN 2 virus, and a source of antibody, and is most conveniently performed without further washing of stationary cultures, which are incubated in 5% CO2. Trypsinization of P388D1 cells prior to the addition of virus-serum mixtures reduced infection in control cultures thus increasing ADE. When cells were washed after incubation of virus-serum mixtures for 1 hour, a paradoxical increase of infection in cultures exposed to virus plus normal serum was noted, which reduced the sensitivity of the ADE assay. Using human cord blood sera, ADE titers measured in human monocytes and P388D1 cells were closely similar. This convenient and economical assay will facilitate large scale biological and epidemiological studies of dengue virus enhancing antibodies.

Animals↗
PubMed1982

Immunological enhancement and the pathogenesis of dengue haemorrhagic fever.

Laboratory studies have provided evidence that the replication of dengue viruses in preparations of primary peripheral blood mononuclear cells of human or simian origin, or in macrophage-like cell lines of human or murine origin, may be enhanced by sub-neutralizing concentrations of homotypic dengue antibody, by heterotypic dengue antibody, or by antibody against heterologous flaviviruses. The mechanism underlying this phenomenon is discussed in the context of dengue haemorrhagic fever and the dengue shock syndrome.

Animals↗
PubMed1982

Monoclonal antibodies against the flavivirus West Nile.

Monoclonal antibodies having three different specificities have been prepared against the Egypt 101 strain of West Nile virus (WNV). All were reactive against the envelope glycoprotein in radioimmune precipitation tests, and all enhanced WNV replication in the mouse macrophage line P388D1. One antibody, which is of IgG2a subclass, had strong neutralizing activity against the homologous virus, although it failed to neutralize a different WNV strain. The other two antibodies, both of IgG1 subclass, had little neutralizing activity, but one had strong reactivity with the haemagglutinin of the inducing virus and other flavivirus haemagglutinins.

Antibodies, Monoclonal↗
PubMed1982

Antibody-dependent plaque enhancement: its antigenic specificity in relation to Togaviridae.

The antigenic specificity of antibody-dependent plaque enhancement (ADPE) on the macrophage cell line P388D1 has been investigated using viruses in the flavivirus and alphavirus genera. Whereas ADPE detected group-specific antigenic determinants in the flaviviruses, narrower specificity (type and subgroup) was seen with alphaviruses. ADPE titres correlated well with haemagglutination inhibition titres.

Alphavirus↗
PubMed1982

Relationship between glycoproteins of the viral envelope of bunyaviruses and antibody-dependent plaque enhancement.

Hamster antisera against three parental bunyaviruses, Batai, Bunyamwera and Maguari viruses, and six recombinant viruses which carried the nucleocapsid protein of one parent and the glycoproteins of the other, have been tested for their interaction with each of the nine viruses under study by two assays, plaque reduction neutralization and antibody-dependent plaque enhancement. Neutralization was clearly related to the specificity of the parental glycoproteins rather than the nucleoprotein, but the antibody-dependent plaque enhancement assay showed greater cross-reactivity.

Animals↗
PubMed1981

Monoclonal anti-Fc receptor IgG blocks antibody enhancement of viral replication in macrophages.

Flaviviruses, when complexed with antibody at subneutralizing concentrations, show enhanced replication in human and simian peripheral blood leukocytes (ref. 1, and J.S.M.P. and J.S.P., unpublished observations) and in P388 D1 and other macrophage cell lines. A comparable phenomenon has been demonstrated with alphaviruses and Bunyaviruses in P388 D1 cells, (J.S.M.P. and J.S.P., unpublished observations) but cells lacking macrophage characteristics fail to show antibody-dependent enhancement (ADE) of viral replication. It has been suggested that the macrophage Fc receptor (FcR) provides an efficient route of entry of virus through the attachment of non-neutralized virus-antibody complexes and that for those viruses that escape destruction by the phagocyte, antibody results in a paradoxical increase in virus replication. West Nile virus (WNV) replication in the P388 D1 macrophage cell line provides a reproducible model system for studying ADE of viral replication. Mouse macrophages have two FcRs-FcRI, which is trypsin-sensitive and binds IgG2a, and FcRII, which is trypsin-resistant and binds IgG2b and IgG1 complexes. The FcR has been purified using rat anti-mouse FcR monoclonal antibody which blocks FcRII. We show here that anti-FcRIgG and its Fab fragment block ADE of virus replication by anti-WNV monoclonal antibodies.

Animals↗
PubMed1981

Antibody-dependent enhancement of plaque formation on cell lines of macrophage origin - a sensitive assay for antiviral antibody.

An assay for antiviral antibody based on antibody-dependent plaque enhancement (ADPE) in the macrophage cell line P388D1 is described which is as sensitive as, or more sensitive than a radioimmune assay. The method is applicable to a range of Togaviridae and Bunyaviridae although not to Picornaviridae and Herpesviridae. The variables affecting the assay are investigated.

Animals↗
PubMed1980

Bunyaviridae.

The family Bunyaviridae comprises over 200 viruses (serotypes, subtypes, and varieties) that infect vertebrates and/or invertebrates. Four genera of viruses have been defined (Bunyavirus, Nairovirus, Phlebovirus, and Uukuvirus). The main characteristics of the member viruses are: (i) the virus particles are for the most part uniformly spherical, 80-110 nm in diameter, and possess a unit membrane envelope from which protrude polypeptide spikes 5-10nm long; (ii) the viruses have three helical nucleocapsids, often in the form of supercoiled circles, each consisting of a single species of single-stranded RNA, major nucleocapsid polypeptide, N, and at least in some cases minor amounts of a large polypeptide which may be a transcriptase component; (iii) the genome is composed of three species of RNA (L, large; M, medium; and S, small), organized in end-hydrogen bonded circular structures; (iv) most viruses have three major virion polypeptides (N, and two surface polypeptides, designated G1 and G2); (v) for at least some member viruses, the virions have been shown to contain an RNA-directed RNA polymerase, believed to be responsible for the synthesis of viral complementary mRNA, so that bunyaviruses are considered to be negative-stranded viruses; (vi) at least some bunyaviruses are capable of heterologous virus genome segment reassortment and can form recombinant viruses at high or low frequency; (vii) viruses appear to mature primarily at smooth membrane surfaces and accumulate in Golgi vesicles and saccules, or nearby; (viii) transovarial, venereal and/or transstadial transmission in arthropods has been shown to occur for some members of the family.

Bunyaviridae↗
PubMed1980

Enhancement of dengue virus infection in monocytes by flavivirus antisera.

Enhanced dengue 2 virus (D2V) infection in suspension cultures of human peripheral blood mononuclear phagocytes (PBL) produced by subneutralizing concentrations of dengue antisera has been described previously. In this study, the enhancement phenomenon was found to be a general property of representative flavivirus antisera. All except one of 24 antisera, which had been raised by 1-3 injections of flaviviruses in rabbits, enhanced the growth of dengue 2 virus in human PBL. Flavivirus antisera showing the greatest level of cross-reactivity against a battery of 42 flavivirus antigens in the hemagglutination-inhibition test were most potent in enhancing dengue replication in PBL cultures. Cross-neutralizing reactivity did not relate to enhanced D2V infection. However nearly one-half of studied flavivirus antisera neutralized D2V at dilutions of 1:10 or 1:20. Heterotypic D2V neutralizing antibody could serve as a "brake" on infection enhancement in vivo. Observations should be made in the field to look for possible enhancement of dengue infection in heterotypic flavivirus immunes.

Adult↗
PubMed1979

Antibody-mediated enhancement of Flavivirus replication in macrophage-like cell lines.

Interactions between animal viruses and antiviral antisera may exceptionally result in an apparent increase in viral infectivity. Halstead and coworkers demonstrated enhanced replication of dengue virus (a Flavivirus, family Togaviridae) in human or simian peripheral blood leucocytes carrying Fc receptors at subneutralising concentrations of antidengue antibody. We have used three continuous cell lines which express macrophage markers to explore the mechanism of this phenomenon. Dengue virus failed to replicate in these cells, but West Nile virus, another Flavivirus, replicated in all three, and we were able to demonstrate reproducibly 50--100-fold enhancement of virus yields in the presence of Flavivirus antisera, the effect also being directly demonstrable in P388D1 cells by increased numbers of virus-induced plaques. The phenomenon of antibody-dependent enhancement of viral replication is not unique to dengue virus, and may have far wider relevance in other viral infections.

Animals↗
PubMed1978

Isolation of an infectious agent from bone-marrows of patients with multiple sclerosis.

Bone-marrow aspirates from 5 patients with recent episodes of multiple sclerosis (M.S.) contained increased numbers of plasma cells, and aspirates from 3 of these patients contained atypical reticulum cells. When bone-marrow from 4 of the patients was inoculated into cell cultures a cytopathic effect (C.P.E.) was observed, and this effect could be serially passaged to further cultures. The C.P.E. was not observed when ether-treated extracts of cells showing C.P.E. were used for passage or when the passage material was filtered through a 100 nm filter. Appearance of C.P.E. was delayed in cultures inoculated with 220 nm filtrates of inoculum was passed through filters of greater pore size. No C.P.E. was observed after culture of bone-marrow aspirated from each of 7 patients under clinical investigation for disorders other than M.S.

Adult↗
PubMed1978

Togaviridae.

The family Togaviridae is described; it contains four genera--Alphavirus, Flavivirus, Pestivirus and Rubivirus--and additional members. The main characteristics of the family are as follows: single-stranded, linear RNA, molecular weight about 4 X 10(6). Virions have isometric nucleocapsids surrounded by a lipoprotein envelope containing host cell lipid and virus-specified polypeptides including one or more glycopeptides. Virions yield infectious RNA. There are at least 80 members; all the alphaviruses and most flaviviruses are arboviruses in the biological sense.

Arboviruses↗
PubMed1975

The multiplication of Nodamura virus in insect and mammalian cell cultures.

Nodamura virus multiplied in mosquito cell lines, as determined by infectivivity assays in adult honey bees (Apis mellifera) and wax moth larvae (Galleria mellonella). Titres of more than 10-7 and 10-5 bee LD50 /ml were obtained in culture fluids of Aedes albopictus and Aedes aegypti cells respectively after 10 days. Comparable titres were obtained after several months, during which the cultures were subdivided up to six times. Nodamura virus also multiplied in BHK cells and yielded titres of 10-4-8 to 10-6-6 mouse LD50/ml and 10-5-1 to 10-7-1 wax moth LD50/ml in culture fluid 1 to 4 days after infection. No c.p.e. was observed in infected cells.

Aedes↗
PubMed1975

The basis of arbovirus classification.

The biologically defined set of arboviruses contains well over 300 separate viruses which have been subdivided into some 40 serological groups on the basis of antigenic cross-reactivity. More than three quarters of all arboviruses can now bw placed into one of the following five major taxonomic genera based upon the fundamental properties of the virion: alphavirus, flavivirus, orbivirus, rhadovirus, bunyavirus. There are 20 alphaviruses, representing serological Group A, and 57 flaviviruses in serological Group B; these two genera fall into the familty Togaviridae. The 40 orbiviruses, in the family Reoviridae, include some 8 serological groups, and the 8 rhabdoviruses, in the family Rhabdoviridae include another 3 groups. About 160 bunyaviruses, family Bunyaviridae, are divisible into 20 serological groups, 10 of which show intra-group cross-reactions in the Bunyamwera supergroup. One arbovirus contains DNA, namely African swine fever virus; this is classified as an Iridovirus, or icosahedral cytoplasmic deoxyvirus. Nodamura virus, which has been classified as a picornavirus, must be reclassified on the evidence that it possesses a divided genome. A number of arboviruses remain unclassified in taxonomic terms. The absence of arbovirus representatives in several major genera, such as the adenoviruses and the myxoviruses is of no interest.

Arboviruses↗