Monocyte receptors for fibronectin characterized by a monoclonal antibody that interferes with receptor activity.

We describe a molecule on the surface of human peripheral blood monocytes that appears to be a plasma membrane receptor for fibronectin. We have identified this protein using a monoclonal antibody, A6F10, which prevents the interaction between monocytes and substrate-bound fibronectin. Thus, at least functionally, the antibody appears to recognize the plasma membrane receptor for fibronectin. The antibody and its Fab fragments bound to the cell surfaces of human monocytes, tissue macrophages, and, to a lesser extent, neutrophils. It did not react with fibroblasts, lymphocytes, platelets, or erythrocytes. It bound human and guinea pig cells but did not react with rat, mouse, or hamster cells. In Western blots, this monoclonal antibody bound specifically to a polypeptide with apparent molecular weight of 110,000 and made of a single chain. The antigen recognized by A6F10 was susceptible to trypsin digestion. These observations suggest that the monoclonal antibody A6F10 is directed to the fibronectin receptor of human monocytes.

Long-term high-titer neutralizing activity induced by octameric synthetic HIV-1 antigen.

A titer for homologous viral neutralization activity (greater than 1:19,683) was observed after a 3.5-year immunization period with an octameric, branching peptide representing the principal neutralizing determinant (PND) of the human immunodeficiency virus-1IIIB envelope protein. Booster immunizations elicited persistent and potent antibodies in guinea pigs, exceeding responses produced by a conventional bovine serum albumin conjugate by 100-fold. Peptide length, central presentation of a conserved sequence, and inclusion of an upstream sequence contributed to immunogenicity. Titers (greater than 1:1,000) of heterotypic neutralizing antibodies also developed. Octameric PND peptides are a promising approach for an acquired immunodeficiency syndrome (AIDS) vaccine.

Antibodies to human immunodeficiency virus type 1 in the urine specimens of HIV-1-seropositive individuals.

Specific antibodies to human immunodeficiency virus type 1 (HIV-1) were detected in 200-fold concentrated urine samples, but none were detected in unconcentrated urine specimens, from 100 randomly selected HIV-1--seropositive individuals by enzyme-linked immunosorbent assay (ELISA) and Western blot techniques using the manufacturer's recommended procedures. Using modified methods for both the ELISA and Western blot tests, antibodies to HIV-1 have also been detected in the unconcentrated urine specimens from the same HIV-1--seropositive individuals. No difference in the frequency of antibodies to HIV-1 were found between unconcentrated and 200-fold concentrated urine samples when tested by the modified methods. HIV-1 core antigen (p24) was not detected in either the concentrated or the unconcentrated HIV-1--seropositive adult urine samples; none of these individuals showed overt clinical or laboratory evidence of renal dysfunction. The titer of the antibodies to HIV-1 found in the urine specimens was found to be parallel with the titer of antibodies to HIV-1 in the corresponding individual's serum. Further elucidation of the pathophysiology and the nature of the specific antibodies to HIV-1 observed in the urine of HIV-1--seropositive individuals is under investigation in our laboratories.

Amino acid sequence and physicochemical similarities between streptococcal M protein and mammalian tropomyosin.

The amino-terminal sequences of two peptides of type 24 streptococcal M protein show similarities with that of rabbit skeletal muscle tropomyosin, having up to 40% identical residues and probabilities of occurring by chance as low as P less than 10(-5). In addition, a hexapeptide (Glu-Ala-Glu-Lys-Ala-Ala) that is found five times in the M24 protein was shown to be identical to a sequence in tropomyosin. Similarities are also seen in the amino acid compositions and physicochemical properties of the two proteins. The amino-terminal sequences of peptides from another bacterial surface protein, staphylococcal protein A, are highly correlated with segments of two other myofibrillar proteins, rabbit actin (P less than 10(-7)) and rabbit myosin A1 light chain (P less than 10(-6)). The data presented suggest that a close structural relationship exists between mammalian muscle proteins and the biologically active surface proteins of staphylococci and streptococci. In addition, the correlation between sequences in M protein and tropomyosin represents direct evidence of a structural similarity at a molecular level between a streptococcal protein and a mammalian muscle component and may therefore prove relevant to the pathogenicity of the streptococcus.

Improved serodiagnosis of hepatitis C virus infection with synthetic peptide antigen from capsid protein.

Cloning and expression of hepatitis C virus have allowed the development of immunoassays to detect hepatitis C virus infection. However, currently available recombinant fusion protein C100-3 assays, based on a nonstructural protein of the virus, are limited in sensitivity, particularly for detecting acute infection. In this report seroconversion panels showed that an assay based on synthetic peptides, derived from immunodominant regions of both capsid and nonstructural proteins, accelerated hepatitis C virus antibody detection by 4-10 weeks. In screening, this enzyme immunoassay increased detection from 47% to 64% in plasmapheresis donors with elevated alanine aminotransferase levels (greater than 100 international units per liter), from 15% to 24% in anti-hepatitis B core antigen-positive blood donors, and from 28% to 42% in renal dialysis patients when compared with nonstructural peptide-based assays. The screening assay was repeatedly reactive for 27 of 2902 volunteer blood donor samples (0.93%); four sera reacted only with the capsid antigen. The peptide test distinguished true from false positive results in agreement with recombinant immunoblot assay in 96% of blood donor samples repeatably reactive on a recombinant hepatitis C virus enzyme immunoassay.

Hepatitis C in sickle cell anemia.

We evaluated the contribution of hepatitis C virus infection to liver disease in patients with sickle cell anemia. Antibody to hepatitis C virus (anti-HCV) by commercial enzyme immunoassay and a second confirmatory assay were assayed in 121 consecutive patients with sickle cell anemia. Anti-HCV was detected in 25 of 121 patients (20.7%). Of patients transfused > 10 units of blood products, 30.3% were anti-HCV seropositive, whereas 8.6% of those patients who transfused < 10 units were seropositive. In 11 of the 121 patients, serum alanine aminotransferase levels were repeatedly elevated. Nine of these 11 patients were anti-HCV seropositive, one was positive for hepatitis B surface antigen, and one was negative for all viral markers. In contrast, of 110 patients with normal serum alanine aminotransferase levels, only 14% were anti-HCV seropositive. In patients with sickle cell anemia, exposure to hepatitis C is common, related to the number of previous transfusions, and the most likely cause of persistently elevated aminotransferase levels.

Patterns and prevalence of hepatitis C virus infection in posttransfusion non-A, non-B hepatitis.

Improved serologic and polymerase chain reaction (PCR)-based tests for hepatitis C virus (HCV) infection provided an opportunity to reexamine a posttransfusion follow-up study done from 1969 to 1972. A total of 213 cardiac surgery patients was prospectively followed after receiving an average of 18 units of blood, 24% of which was from paid donors. Serial sera were tested for antibody to recombinant DNA-derived C100-3 and capsid polypeptides; selected cases were also tested against synthetic peptides derived from different regions of the HCV sequence. PCR and RIBA II immunoblot assays were done on selected sera. Each of 55 probable and 5 of 11 possible hepatitis cases who were seronegative before transfusion seroconverted. Anti-HCV seroconversion also occurred in 6 (4%) of 148 subjects without hepatitis. Among subjects followed > 1 year, PCR positivity persisted in 14 (82%) of 17. If the results of this study can be generalized, all bloodborne non-A, non-B hepatitis may be due to HCV.

Seroprevalence of HTLV-1 and HTLV-2 among intravenous drug users and persons in clinics for sexually transmitted diseases.

UNLABELLED: Background. The human T-cell lymphotropic virus Type I (HTLV-I) is associated with adult T-cell leukemia and myelopathy, whereas HTLV-II infection has uncertain clinical consequences. We assessed the seroprevalence of these retroviruses among intravenous drug users and among patients seen at clinics for sexually transmitted diseases (STD clinics). METHODS: We used serum samples that were collected in eight cities in 1988 and 1989 during surveys of human immunodeficiency virus infection among intravenous drug users entering treatment and persons seen in STD clinics. The serum samples were tested for antibodies to HTLV, and positive specimens were tested further by a synthetic peptide-based enzyme-linked immunosorbent assay to differentiate between HTLV-I and HTLV-II. RESULTS: Among 3217 intravenous drug users in 29-drug-treatment centers, the median seroprevalence rates of HTLV varied widely according to city (range, 0.4 percent in Atlanta to 17.6 percent in Los Angeles). Seroprevalence increased sharply with age, to 32 percent in persons over 44 years of age. HTLV infection was more common among blacks (15.5 percent) and Hispanics (10.7 percent) than among whites (4.1 percent), and it was strongly associated with a history of heroin injection (P less than or equal to 0.001). Among 5264 patients in 24 STD clinics, the median rates of HTLV infection were much lower (range, 0.1 percent in Atlanta and Newark to 2.0 percent in Los Angeles). Again, this infection was more common among intravenous drug users (7.6 percent) than among non-drug users (0.7 percent). Eighty-four percent of the seropositive samples from drug-treatment centers and 69 percent of those from STD clinics were due to HTLV-II infection (P = 0.03). CONCLUSIONS: HTLV infections are common among intravenous drug users and are primarily caused by HTLV-II. Among patients seen at STD clinics, HTLV is strongly associated with intravenous drug use, but the retrovirus is also prevalent among non-drug users.