Hepatitis C virus serology in parenteral drug users with chronic liver disease.

Chronic liver disease is a common complication of parenteral drug use, and liver cirrhosis is frequently seen in users of both parenteral drugs and alcohol. In 1978-83, we studied 88 parenteral drug users with sufficient evidence of chronic liver disease to warrant liver biopsy. Current alcohol abuse was noted in 63 (72%), and six (7%) were former alcohol abusers. Cirrhosis was found in 33 (38%). Hepatitis C antibody (anti-HCV) was detected in 86 (98%). Also, 40 of the anti-HCV positive sera were tested with recombinant immunoblot assay and all of these were reactive. All but one of the 31 patients with anti-HCV and cirrhosis were alcohol abusers. We conclude that parenteral drug users with chronic liver disease almost always have evidence of HCV infection.

Vertical transmission of human immunodeficiency virus is correlated with the absence of high-affinity/avidity maternal antibodies to the gp120 principal neutralizing domain.

Many, but not all, infants born to mothers infected with the human immunodeficiency virus (HIV) are infected in utero. We have now shown that mothers who have high-affinity/avidity antibodies directed toward the principal neutralizing domain (PND) of gp120 are less likely to transmit HIV to their children. An ELISA that preferentially measures the level of the biologically functioning, high-affinity/avidity antibodies against PND is described. In a retrospective study of 15 maternal/neonatal serum samples, the assay correctly identified the 4 uninfected and the 11 HIV-infected infants. Other clinical and laboratory parameters such as p24 antigen, phytohemagglutinin mitogenic index, and absolute surface antigen T4+ cell counts did not accurately predict HIV fetal transmission. In addition to introducing a promising diagnostic tool, this study provides the in vivo evidence that protective antibodies may prevent infection by HIV.

Prognostic significance of quantitative levels of HIV p24 binding capacity in HIV infection.

Human immunodeficiency virus, type 1 (HIV-1), produces a chronic infection with a long latency before clinical disease. We followed 214 untreated subjects for 12-42 months to study the natural history of HIV infection: 110 were classified as asymptomatic, 11 as AIDS-related complex (ARC), 15 as AIDS with Kaposi's sarcoma (KS), 31 as AIDS with opportunistic infections (AIDS/OI), and 47 were HIV-seronegative controls. The quantitative capacity of serum to complex HIV p24 antigen, termed the p24 binding capacity (p24 BC), and quantitative levels of HIV p24 antigen in serum were determined at regular intervals. For people in all diagnostic groups, a p24 BC below 31 ng/ml was more closely associated with progression to AIDS/OI than was p24 antigen positivity; 94% of AIDS/OI, 86% of ARC, 56% of AIDS/KS, and 19% of asymptomatic subjects had p24 BC less than 31 ng/ml during the study period, while 67% of AIDS/OI, 27% of ARC, 61% of AIDS/KS, and 20% of asymptomatic subjects were p24 antigenemic. Prospective analysis of 47 asymptomatic seropositive men followed for 3 years, who showed actuarial progression rates to ARC at 4%, 13%, and 23% and to AIDS at 5%, 8%, and 8% at 1, 2, and 3 years, indicated that entry levels of p24 BC below 31 ng/ml were as strongly associated with progression to ARC/AIDS as was p24 antigenemia (p = 0.0003 vs. p = 0.008). The p24 binding capacity assay is a new and convenient methodology to measure immunocomplexing antibody to HIV p24 and is a powerful indicator of progressive HIV disease.

Rabies virus interaction with various cell lines is independent of the acetylcholine receptor.

Rabies virus infects most cells in vitro. The presence of the nicotinic acetylcholine receptor on the plasma membrane of various cell lines is not an obligate factor for rabies virus susceptibility of those cells.

Protection from rabies by a vaccinia virus recombinant containing the rabies virus glycoprotein gene.

Inoculation of rabbits and mice with a vaccinia-rabies glycoprotein recombinant (V-RG) virus resulted in rapid induction of high concentrations of rabies virus-neutralizing antibodies and protection from severe intracerebral challenge with several strains of rabies virus. Protection from virus challenge also was achieved against the rabies-related Duvenhage virus but not against the Mokola virus. Effective immunization by V-RG depended on the expression of a rabies glycoprotein that registered proline rather than leucine as the eighth amino acid from its NH2 terminus (V-RGpro8). A minimum dose required for effective immunization of mice was 10(4) plaque-forming units of V-RGpro8 virus. beta-propiolactone-inactivated preparations of V-RGpro8 virus also induced high levels of rabies virus-neutralizing antibody and protected mice against intracerebral challenge with street rabies virus. V-RGpro8 virus was highly effective in priming mice to generate a secondary rabies virus-specific cytotoxic T-lymphocyte response following culture of lymphocytes with either ERA or PM strains of rabies virus.

Characterization of saturable binding sites for rabies virus.

A specific, saturable receptor for rabies virus was analyzed on cultured cells of neural or non-neural origin. Viral attachment kinetics were enhanced by DEAE-dextran, an effect which in turn enhanced the apparent infectivity of the virus inoculum. Under optimized conditions, the attachment of metabolically labeled ERA strain rabies virus obeyed the laws of mass action, whereby the amount of virus bound to cells varied proportionally with the concentration of cells or virus. Attachment was sensitive to changes of temperature and pH, did not require divalent cations such as Mg2+ or Ca2+, and occurred despite prior treatment of cells with proteolytic or sialic acid-specific enzymes. Saturation of the cell surface with rabies virus could be accomplished with 3 X 10(3) to 15 X 10(3) attached virions per cell. Competition for the rabies receptor occurred with rabies nonpathogenic variant virus, RV194 -2, and vesicular stomatitis virus. Reovirus type 3, another neurotropic virus, failed to inhibit rabies virus binding, and West Nile virus only slightly inhibited rabies virus binding, suggesting independent cellular receptors were recognized by these viruses. Isolated rabies virus glycoprotein failed to compete in an equivalent manner. However, solubilization of BHK-21 cells with octylglucoside yielded a chloroform-methanol-soluble extract which blocked rabies virus attachment. The binding inhibition activity of this extract was resistant to proteases but could be destroyed by phospholipases and neuraminidase, suggesting a phospholipid or glycolipid component at the receptor site. These data provide evidence for a rhabdovirus-common mechanism for cellular attachment to cells in culture.

Altered receptor specificity of coxsackievirus B3 after growth in rhabdomyosarcoma cells.

Serial "blind" passages in human rhabdomyosarcoma (RD) cells of prototype viruses from each of the six immunotypes of the group B coxsackieviruses (CB) resulted in the isolation of intratypic variants of CB1, CB3, CB5, and CB6. Each variant virus strain acquired the capacity to agglutinate human erythrocytes and produce small plaques on HeLa cells, although their serological specificity remained unchanged. An alteration in VP1 mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis was noted for CB3-RD. The CB3-RD variant was plaque purified on RD cells and studied for receptor interactions on both HeLa and RD cells. An attachment restriction appeared to exist for prototype CB3 on RD cells, whereas CB3-RD attached well to both cells. In attachment interference assays, HeLa cells saturated with CB3-RD blocked the attachment of CB3. In contrast, saturation of cells with CB1 (which shares a common receptor with parental CB3) failed to block the attachment of CB3-RD. This unidirectional receptor blockade suggested that a second site for the attachment of virions to receptors was acquired by the CB3-RD variant. Thus, more than one virus receptor specificity may be operative in the selection of host range virus mutants. The implications of this phenomenon as they may relate to pathogenesis are discussed.

Anti-idiotypic antibodies induce neutralizing antibodies to rabies virus glycoprotein.

Rabbit anti-idiotypic antibodies (alpha Id Ab) were prepared against five murine monoclonal antibodies (mAb) specific for the rabies virus glycoprotein. Four of the mAb were directed against three known, type-specific, neutralizing sites on the glycoprotein, and the other mAb was directed against a topographically uncharacterized, nonneutralizing epitope. An absence of significant cross-reactivity among the alpha Id Ab for heterologous mAb suggested that the alpha Id Ab were highly specific for unique variable region determinants. The binding of three of the five alpha Id Ab to their homologous mAb could be inhibited by rabies virus-soluble glycoprotein, suggesting that the alpha Id Ab possessed subpopulations similar or adjacent to the antigen-binding site of the mAb. Two of the five alpha Id Ab injected into mice elicited a specific virus-neutralizing antibody response. Mechanisms to account for the induction of the virus-neutralizing antibody by alpha Id Ab are discussed.

Persistence of human rhinovirus infectivity under diverse environmental conditions.

The persistence of human rhinovirus type 2 and type 14 infectivity was studied under various laboratory conditions designed to mimic those commonly found in the environment. The effects of temperature, ionic strength, protein content, and evaporation were compared. Both viruses were stable (less than 0.3-log decrease in titer) at 6 and 23 degrees c for 24 h in the liquid state regardless of salt or protein additives; a titer decrease of less than 1.0 log was noted at 37 degrees C. However, evaporation at 37 degrees C reduced virus infectivity by 3.2 to 4.5 logs in buffered water, an effect which could be significantly lessened by the addition of bovine serum albumin in saline (2.0- to 2.9-log decrease in titer). These studies support and extend observations by others that the human rhinoviruses retain sufficient infectivity after drying on hard surfaces to permit their transmission to susceptible persons upon contact.