A second neutralizing epitope of B19 parvovirus implicates the spike region in the immune response

We used 18 monoclonal antibodies against B19 parvovirus to identify neutralizing epitopes on the viral capsid. Of the 18 antibodies, 9 had in vitro neutralizing activity in a bone marrow colony culture assay. The overlapping polypeptide fragments spanning the B19 structural proteins were produced in a pMAL-c Escherichia coli expression system and used to investigate the binding sites of the neutralizing antibodies. One of the nine neutralizing antibodies reacted with both VP1 and VP2 capsid proteins and a single polypeptide fragment on an immunoblot, identifying a linear neutralizing epitope between amino acids 57 and 77 of the VP2 capsid protein. Eight of nine neutralizing antibodies failed to react with either of the capsid proteins or any polypeptide fragments, despite reactivities with intact virions in a radioimmunoassay, suggesting that additional conformationally dependent neutralizing epitopes exist.

Self-assembled B19 parvovirus capsids, produced in a baculovirus system, are antigenically and immunogenically similar to native virions

B19 parvovirus is pathogenic in humans, causing fifth disease, transient aplastic crisis, some cases of hydrops fetalis, and acquired pure red cell aplasia. Efforts to develop serologic assays and vaccine development have been hampered by the virus's extreme tropism for human bone marrow and the absence of a convenient culture system. We constructed recombinants containing either the major (VP2) or minor (VP1) structural proteins of B19 in a baculovirus-based plasmid, from which the polyhedrin gene had been deleted; these recombinant plasmids were used to generate recombinant infectious baculovirus. Subsequent infection of insect cells in vitro resulted in high-level expression of either B19VP1 or VP2. Parvovirus capsids were obtained by self-assembly in cell cultures coinfected with either VP1- and VP2-containing baculoviruses or, surprisingly, VP2-containing baculoviruses alone. Empty B19 capsids composed of VP1 and VP2 could replace serum virus as a source of antigen in a conventional immunoassay for detection of either IgG or IgM antiparvovirus antibodies in human serum. Immunization of rabbits with capsids composed of VP1 and VP2 resulted in production of antisera that recognized serum parvovirus on immunoblot and neutralized parvovirus infectivity for human erythroid progenitor cells. Baculovirus-derived parvovirus antigen can substitute for scarce viral antigen in immunoassays and should be suitable as a human vaccine.

O'Bannon v. Town Court Nursing Center: patients' right to participate in nursing home decertification

A decertification action by the Department of Health and Human Services (formerly the Department of Health, Education and Welfare) substantially impacts on the lives of Medicaid patients who reside in the affected nursing home. Decertification means that the federal government, the state government, or both will no longer pay for the care of Medicaid patients in the decertified home. Thus, a decision to decertify necessitates the transfer of elderly and infirm Medicaid patients out of the decertified home. Since this transfer may threaten the lives and health of these patients, they should be granted the right to participate in pre-decertification proceedings. However, in O'Bannon v. Town Court Nursing Center, the Supreme Court decided that patients do not have the right to participate in predecertification proceedings. The Court rejected the patients' due process arguments, finding: 1) that decertification does not deprive the patients of any constitutionally protected interest in life, liberty, or property; and 2) that any adverse consequences of decertification are only an "indirect and incidental" result of government action. This Comment analyzes the Supreme Court opinion and concludes that the patients have protectable property and life interests that entitle them to participate in some form of hearing prior to the decertification of the nursing home where they reside. In addition, this Comment suggests alternative methods for asserting nursing home patients' legal rights.

Gelfoam paste in experimental laminectomy and cranial trephination: hemostasis and bone healing

The hemostatic properties and effect on osteogenesis of gelatin foam paste and bone wax were compared on surgical bone lesions in experimental animals. Thirty rabbits each received four trephine craniotomies and four lumbar laminectomies. Alternate bone incisions in each animal were treated with either gelatin foam paste or bone wax. Blood loss was measured by absorbing the blood into dry surgical cottonoids weighed before and after use. Bone healing sites of three rabbits were examined histologically to assess the effect of each agent on osteogenesis. The trephination sites of eight rabbits were subjected to fracture force testing at 6 weeks postoperatively to compare the effect ot the two agents on bone healing. No significant difference was found between gelatin foam paste and bone wax in either effectiveness of hemostasis or effect on osteogenesis.

The linearity of the volume/pressure response during intracranial pressure "reserve" testing

The intracranial pressure "reserve" test seems to be the most reliable method of determining when the brain's natural mechanisms for pressure compensation for added intracranial volume have been compromised or exhausted. The test employs a timed sequence of intracranial fluid injections, but as a safety precaution injections are discontinued if intracranial pressure remains elevated more than 10 Torr over baseline. In this case, a linear extrapolation is then calculated to determine the elevation which might have been achieved by a full series of injections. However, this linear extrapolation has been criticised on the expectation that an exponential response should be expected. A series of experimental observations in dogs and baboons and a review of clinical records in humans have been made to determine the observed slope of increase following aliquot injection during performance of the intracranial pressure reserve test. In these species the observed response was actually linear in shape rather than exponential. This held true even for different initial baseline values and with different volumes of "lesion" balloon inflations in experimental animals. A theoretic explanation is proposed.

Coexistence of IgA myeloma and Gaucher's disease

An elderly woman of Ashkenazic Jewish descent, who had had adult Gaucher's disease diagnosed seven years previously, was found to have IgA myeloma. The diagnosis of IgA myeloma was confirmed by the presence of lytic lesions in the skull and long bones, atypical plasma cells in bone marrow, and monoclonal elevation of IgA, kappa-type. In addition, the marrow contained Gaucher's cells. A causal relationship between these two pathologic entities remains speculative.

Cleavage of a specific bond in troponin C by thrombin

Limited proteolysis of rabbit skeletal troponin C with bovine thrombin yielded two fragments, TH1 (Mr = 11000) containing Ca2+ binding regions I--III and TH2 (Mr = 6000) containing region IV. Determination of the partial sequences of the fragments established the site of cleavage at Arg120-Ala121. Secondary cleavage by thrombin at other arginyl or lysyl residues in troponin C was ruled out by the sequence data and by the amino acid compositions of the two fragments.

Renin stimulation by isoproterenol and theophylline in the isolated perfused kidney

The intrarenal mechanisms of renin release were studied in the isolated perfused rabbit kidney during stimulation by isoproterenol, 0.01 mug/kg per min, and by theophylline, 0.87 mg/kg per min. In the absence of urinary flow during the early stages of perfusion, isoproterenol caused a 17% increase of renal vein serum renin concentration (RVSRC) (P less than 0.001) without changing renal blood flow, renal vascular resistance, or serum potassium. dl-Propranolol, 2.0 mg/kg per min. abolished this isoproterenol-induced renin release. A moderate reduction in perfusion pressure prior to the infusion of isoproterenol resulted in a marked additional stimulation of renin release. Studies during and following ureteral occlusion demonstrated that theophylline stimulates renin release by decreasing renal vascular resistance, whereas the concomitant increase in sodium transport to the macula densa exerted an opposite effect. dl-Propranolol did not affect theophylline-induced renin secretion. It is concluded that single exogenous stimuli may activate more than one intrarenal mechanism simultaneously. Isoproterenol has a direct renin-stimulatory effect on intrarenal beta-adrenergic receptors that may be reinforced by baroreceptor stimulation. Theophylline stimulates renin via a baroreceptor mechanism, with simultaneous renin suppression via a sodium-macula densa effect.

On the chemical nature of transfer factor

Two transfer factors prepared in an experimental animal model, the guinea pig, have been tested for their susceptibility to various enzymes of known specificity. The biological activity of these immune response mediators can be destroyed by RNase III, an enzyme that degrades duplex RNA. It, therefore, appears that these transfer factors consist entirely or partly of double-stranded RNA.

Inactivation of arginine-vasopressin by the isolated perfused rabbit kidney

The ability of the kidney to extract (inactivate and excrete) argininevasopressin (AVP) from the blood was studied in the isolated perfused rabbit kidney. AVP was added to the blood reservoir to give an initial approximate concentration of 100 μu./ml plasma and samples were taken simultaneously from the arterial and venous side at 5, 15, 30 and 45 min. The AVP concentration in the plasma samples was determined by bioassay in the water-loaded, ethanol-anaesthetized rat. The clearance (extraction ratio x renal plasma flow) of AVP from the blood was concentration-dependent. The average extraction ratio ranged from 0·25 at levels of 100 to 44 μu./ml plasma and 0·42 at levels of 44 to 19 μu./ml plasma. The excretion of AVP in the urine was 23% and 29% respectively of the calculated filtered load, in two isolated perfused kidneys, indicating tubular reabsorption and/or tissue inactivation of the filtered hormone.

Transfer factor: a subcellular component that transmits information for specific immune responses

Two transfer factors have been prepared in an animal model system, the guinea pig. They are both small molecules, derived from the leukocytes of immunologically experienced individuals, and capable of transferring information for specific immune responses to naive individuals.