Mothers' motivations to participate in a pregnancy health survey

An important question in interpreting epidemiologic data is why some persons agree to participate in a health survey while others do not. Information about why people agree to interview or answer a questionnaire could help researchers to devise procedures for a health survey and to chose information to be communicated in the interview or questionnaire so as to increase subjects' participation. The authors interviewed 180 mothers who gave birth to a child with a birth defect and 198 mothers whose children were born without a birth defect. The interviews were part of two case-control studies to determine risk factors for selected birth defects. In the course of the interviews, each mother was asked why she agreed to be interviewed, and whether anything about the survey procedures that were followed could be improved. Among both the case mothers and the control mothers the most common reason for agreeing to be interviewed was humanitarian, expressed as "to help others" or "to prevent what happened to my baby from happening to babies in the future." Case mothers, more frequently than control mothers, gave as their reason for participating either to help themselves, their child, their family, or to further scientific understanding. Emphasizing these as benefits of participation to those who are survey subjects at the time of the initial contact could increase the proportion who agree to respond.

Birth defects monitoring in California: a resource for epidemiological research

The California Birth Defects Monitoring Program maintains a population-based birth defects registry of structural congenital malformations, monitoring over 600,000 resident births annually. Cases are actively ascertained from hospitals and genetic centres throughout California and from selected facilities in adjacent states. Field staff identify presumptive cases from careful review of medical records. Diagnostic and demographic information is collected from in-patient and genetic centre medical charts for children diagnosed with major structural malformations between conception and 1 year of age. The application of these data to epidemiological investigations of birth defects is described in the context of prevalence studies, aetiological studies and evaluative studies, and the strengths and limitations of the registry data are discussed.

Human immunodeficiency virus type 2 vpx protein augments viral infectivity

The genomes of HIV and SIV are complex and contain several accessory genes which modulate viral replication and pathogenicity. One of these genes, vpx, is unique to the HIV-2/SIV group of viruses and encodes a virion-associated protein of unknown function. To examine the function of vpx, we constructed a vpx-deficient HIV-2 proviral clone and characterized its in vitro biological properties. Following transfection into immortalized T-cell lines, vpx-mutant HIV-2 was fully replication competent and exhibited growth kinetics and cytopathic properties equivalent to wild-type HIV-2. In addition, vpx-deficient virions were indistinguishable from wild-type HIV-2 in ultrastructure, composition of major structural proteins, and reverse transcriptase activity. In PHA-stimulated normal peripheral blood mononuclear cells (PBMCs), however, vpx-deficient virus replicated at substantially lower titers and required a 100- to 1000-fold higher inoculum to establish a productive infection. This defect was localized to early events in the viral life cycle since vpx-deficient virus exhibited a 5- to 10-fold reduction in initial (single cycle) viral DNA synthesis following acute infection of primary PBMCs. Paradoxically, in long-term (9-23 months) cultures of immortalized T-cells (SupT1) continuous high level replication of vpx-deficient, but not wild-type, virus was observed, indicating less efficient viral spread and cell killing and a more attenuated phenotype of vpx-deficient HIV-2. Taken together, these results demonstrate that vpx is required for the production of fully infectious and cytopathic HIV-2 virions and that it functions early in the viral life cycle by facilitating viral entry and/or reverse transcription. The pronounced replicative defect of vpx-deficient HIV-2 in primary PBMCs but not in short-term cultures of immortalized T-cell lines emphasizes the need to characterize the properties of nonessential HIV accessory gene products in natural target cells.

Molecular characterization of human immunodeficiency virus type 1 cloned directly from uncultured human brain tissue: identification of replication-competent and -defective viral genomes

All presently available replication-competent proviral clones of human immunodeficiency virus type 1 (HIV-1) are derived from cell culture-amplified virus. Since tissue culture is highly selective for viral strains with an in vitro growth advantage, such clones may not be representative of the biologically relevant virus present in vivo. In this study, we report the molecular cloning and genotypic characterization of 10 HIV-1 genomes directly from uncultured brain tissue of a patient with AIDS dementia complex. Targeting unintegrated circular HIV-1 molecules for recombinant lambda phage cloning, we obtained four full-length genomes with one or two long terminal repeats (LTRs), three defective genomes with internal deletions, two rearranged genomes with inverted LTR sequences, and one integrated proviral half with flanking cellular sequences. Nucleotide sequence analysis of these clones demonstrated chromosomal integration, circle formation, genomic inversion, and LTR-mediated autointegration of HIV-1 genomes in vivo. Comparison of a 510-bp hypervariable envelope region among 8 lambda phage-derived and 12 polymerase chain reaction-derived clones from the same brain specimen identified a predominant viral form as well as genetically divergent variants. Variability among 19 of 20 clones ranged between 0.2 and 1.2%. One clone exhibited 8.2% nucleotide sequence differences consisting almost exclusively of G-to-A changes. Transfection of the four full-length HIV-1 genomes identified one clone (YU-2) as replication competent and exhibiting growth characteristics similar to those of tissue culture-derived macrophage tropic strains of HIV-1. These results demonstrate, for the first time, that replication-competent HIV-1 genomes, complex mixtures of defective viral forms, and chromosomally integrated provirus persist in vivo. In addition, the brain-derived viral clones are expected to prove valuable for future studies of macrophage and neurotropism as well as for the analysis of other viral properties that are subject to in vitro selection pressures.

Modified Western blot assay for confirmation and differentiation of human T cell lymphotropic virus types I and II

Disease association studies of human T cell lymphotropic virus (HTLV) types I and II are hindered by the need for multiple assays to confirm and differentiate between the viruses. A modified Western blot assay has been developed using HTLV-I viral lysate and unique (MTA-4) and shared (p21E) HTLV recombinant proteins. By defining confirmation of infection as the presence of antibodies to p24 gag protein and to p21E, all 56 HTLV-I and 49 HTLV-II antisera were confirmed by this modified Western blot alone. Differentiation was determined by reactivity to MTA-4. All HTLV-I antisera reacted with MTA-4 and all HTLV-II antisera did not react with MTA-4. These findings indicate the utility of selected HTLV-I recombinant proteins in a single assay format to confirm and differentiate infections with HTLV-I and HTLV-II.

High-level viremia in adults and children infected with human immunodeficiency virus: relation to disease stage and CD4+ lymphocyte levels

Sixty-eight adults and nine children infected with human immunodeficiency virus type 1 (HIV-1) were evaluated consecutively for the presence and amount of cell-free infectious virus in their plasma. Viremia was detected in 18 of 68 adults and in five of nine children; titers ranged from 10 to 100,000,000 TCID/ml plasma. Among the adults, none of 19 asymptomatic patients, 4 of 34 AIDS-related complex patients, and 14 of 15 AIDS patients had cell-free infectious virus in their plasma. None of 35 adult subjects with CD4+ lymphocyte counts greater than 400/mm3 were viremic, whereas 3 of 17 with 200-400 CD4+ lymphocytes/mm3 and 15 of 16 individuals with less than 200 CD4+ lymphocytes/mm3 were plasma viremic. In contrast to adults, each of five children infected with HIV-1 in utero or during the perinatal period were plasma viremic regardless of their CD4+ lymphocytes counts (range, 42-2227/mm3), duration of infection, or clinical stage; however, children infected by HIV-1 at older ages were less frequently plasma viremic. Therapy with zidovudine led to a 10- to 10(6)-fold decline in plasma HIV-1 TCID in all eight subjects studied before and after treatment.

Species-specific diversity among simian immunodeficiency viruses from African green monkeys

The prevalence, natural history, and genetic characteristics of simian immunodeficiency virus (SIV) infections in most feral African monkey species are presently unknown, yet this information is essential to elucidate their origin and relationship to other simian and human immunodeficiency viruses. In this study, a combination of classical and molecular approaches were used to identify and characterize SIV isolates from West African green monkeys (Cercopithecus sabaeus) (SIVagm isolates). Four SIVagm viruses from wild-caught West African green monkeys were isolated and analyzed biologically and molecularly. Amplification, cloning, and sequencing of a 279-bp polymerase fragment directly from uncultured peripheral blood mononuclear cells was facilitated by the use of nested polymerase chain reaction. The results indicated that West African green monkeys are naturally infected with SIVs which are closely related to East African SIVagm isolates. However, structural, antigenic, and genetic differences were observed which strongly suggest that the West African green monkey viruses comprise a phylogenetically distinct subgroup of SIVagm. These findings support our previous hypothesis that SIVagm viruses may have evolved and diverged coincident with the evolution and divergence of their African green monkey host. In addition, this study describes a polymerase chain reaction-based approach that allows the identification and molecular analysis of divergent SIV strains directly from primary monkey tissue. This approach, which does not depend on virus isolation methods, should facilitate future studies aimed at elucidating the origins and natural history of SIVs in feral African green monkey populations.

High titers of cytopathic virus in plasma of patients with symptomatic primary HIV-1 infection

BACKGROUND

Primary infection with the human immunodeficiency virus (HIV-1) frequently causes an acute, self-limited viral syndrome. To examine the relations among viral replication, the immune response of the host, and clinical illness during this initial phase of infection, we undertook a quantitative, molecular, and biologic analysis of infectious HIV-1 in the blood and plasma of three patients with symptomatic primary infection and of a sexual partner of one of them.

METHODS

During an eight-week period of primary infection, HIV-1 was cultured frequently in dilutions of plasma and peripheral-blood mononuclear cells (PBMC), and levels of HIV-1 antigen and antibody were determined sequentially by enzyme-linked immunosorbent assay and immunoblotting. Replication-competent HIV-1 proviruses were cloned and characterized biologically.

RESULTS

Six to 15 days after the onset of symptoms, high titers of infectious HIV-1 (from 10 to 10(3) tissue-culture-infective doses per milliliter of plasma) and viral p24 antigen were detected in the plasma of all three patients. These titers fell precipitously by day 27, and the decline coincided with an increase in the levels of antiviral antibodies and the resolution of symptoms. Sequential isolates of virus from plasma and PBMC obtained throughout the period of primary infection, as well as virus derived from two molecular proviral clones, were highly cytopathic for normal-donor PBMC and immortalized T cells, despite the marked reduction in the titers of virus in plasma.

CONCLUSIONS

Primary, symptomatic HIV-1 infection is associated with high titers of cytopathic, replication-competent viral strains, and during such infection potential infectivity is enhanced. Effective control of HIV-1 replication during primary infection implies the activation of clinically important mechanisms of immune defense that merit further examination in relation to the development of antiviral therapy and vaccines.

Isolated oral cleft malformations: associations with maternal and infant characteristics in a California population

Data on isolated oral cleft malformations from a birth defects registry covering a large population base were examined to describe potential associations with maternal and infant characteristics. Infants with cleft palate (CP) were analyzed separately from infants with cleft lip with or without cleft palate (CLP). The prevalence of isolated CLP per 1,000 births was 0.741, approximately twice the prevalence of isolated CP, which was 0.383. Male infants were more likely to be born with CLP (OR = 1.9) but less likely to be born with CP (OR = 0.56) than were females. Women 39 years or more of age were twice as likely as 25-29 year olds to have a child with either type of cleft. Black, nonhispanic infants had a lowered risk for CLP compared to white, nonhispanics (OR = 0.40). These risks were found to be independent of each other based on multivariate analyses. Associations with either type of cleft malformation were not observed for plurality, number of previous live births, and maternal birthplace.

Spontaneous lymphocyte proliferation in HTLV-II infection

We measured lymphocyte proliferation in the absence of antigenic stimulation in 45 HTLV-II infected, 9 HTLV-I infected, and 19 HTLV-I seronegative intravenous drug users (IVDU). Lymphocyte proliferation was higher in IVDUs infected with HTLV-II than in seronegative IVDUs but lower than among those infected with HTLV-I. Higher rates of proliferation were also associated with needle sharing, CD4+ and IL2R+ lymphocyte counts, and HTLV-I antibody titres.

Type-specific antigens for serological discrimination of HTLV-I and HTLV-II infection

55 HTLV-I (human T-cell lymphotropic virus) and 45 HTLV-II carriers, confirmed by HTLV-type specific polymerase chain reaction (PCR), were distinguished by western blot assays with recombinant HTLV I or II envelope glycoproteins. Recombinant protein (RP) B1 contains aminoacids 166-201 from HTLV-I exterior glycoprotein gp46 and was reactive with HTLV-I samples only. RP-IIB, which contains aminoacids 96-235 from HTLV-II exterior glycoprotein gp52, was reactive with all HTLV-II samples. 39 patients (86.6%) had high reactivity by densitometry. Of 55 HTLV-I samples, 35 (65.5%) had antibody reactivity to RP-IIB, but only 1 (1.8%) had high reactivity by densitometry. RP B1 and IIB western blot assays may replace the PCR test in diagnosis of HTLV infection.

Epidemiologic research using existing databases of environmental measures

When detailed information on individuals is not available, databases of environmental measures are sometimes used in epidemiologic studies to provide data on human exposure. The use of such databases is based on the assumption that the data are representative of individual human exposure and are applicable to the study. Twenty-six databases that contained data on the environment pertaining to California were summarized and evaluated by categorical criteria of spatial and temporal precision, availability, amount of quantitative information, "machine-readability," and type of environmental measure.

Determination of a unique and immunodominant epitope of human T cell lymphotropic virus type I

The identification and isolation of unique and immunogenic recombinant epitopes for human T cell lymphotrophic virus (HTLV) type I might allow the development of an antibody-based assay to differentiate between HTLV-I and HTLV-II infections. To test the feasibility of this approach, an HTLV-I envelope epitope was isolated by immunoscreening of a lambda gt11 recombinant HTLV-I DNA library with a human monoclonal antibody to HTLV-I. This recombinant epitope. MTA-4, when tested with sera from HTLV-I- or HTLV-II-infected individuals, was reactive with all HTLV-I and nonreactive with all HTLV-II antisera. These results indicate that MTA-4 is a unique and immunodominant epitope on HTLV-I and confirm the usefulness of human-derived monoclonal antibodies in an experimental approach to dissect the human humoral response to a viral pathogen.

An assessment of error in parental occupation from the birth certificate

This study used data obtained through interview with the mother to determine whether parental occupations from the California birth certificate were representative of maternal occupations during the first trimester of pregnancy or paternal occupations 3 months before conception. For 71% of mothers and 80% of fathers, the occupation on the birth certificate was the same as the occupation elicited from the interview. The sensitivity of the birth certificate for determining whether a mother or father was employed or employed in a particular standard occupational category ranged from 50 to 100%. The bias to the odds ratio associated with a sensitivity of 75% and a specificity of 80% is presented. The results suggest that the use of birth certificate information on parental occupation to screen for associations with congenital malformations will miss all but very strong associations.

Maternal water consumption during pregnancy and congenital cardiac anomalies

This case-control study, conducted in a California county that had a local incident of water contamination in 1981, investigated the relation between a mother's reported consumption of tap water during pregnancy and congenital cardiac anomalies in their offspring born during 1981-1983. Data were obtained from telephone interviews with 145 mothers of children born with a severe cardiac anomaly and 176 mothers of children born without such an anomaly. A positive association between a mother's consumption of home tap water during the first trimester of pregnancy and cardiac anomalies in her infant was unrelated to the incident of water contamination, the mother's race, or her educational level. A negative relation was found between a mother's use of bottled water and cardiac anomalies among the infants. These findings corresponded primarily to births in 1981. These data could not fully distinguish between a potential causal agent in the water and differential reporting of exposure by study subjects.

Detection of excess disease near an exposure point: a case study

Many studies have evaluated the likelihood of adverse health effects associated with environmental contamination from point source exposures. Two statistical measures used in these studies are the ratio, R, of the observed to the expected number of cases occurring in the area containing the point and the average distance, D, between the cases and the point. This paper estimates the probability of detecting an association between disease and exposure when one actually exists (power) for R and D for several specific and plausible statistical models. Results are presented in the context of rare diseases such as congenital malformations. The practical implications of using these measures for the evaluation of risk of disease in environmental epidemiologic investigations are discussed.

Molecular characterization of an attenuated human immunodeficiency virus type 2 isolate

Naturally occurring strains of human immunodeficiency virus (HIV) can vary considerably in their in vitro biological properties, and such differences may also be reflected in their in vivo pathogenesis. In an attempt to define genetic determinants of viral pathogenicity, we have molecularly cloned, sequenced, and characterized an attenuated isolate of HIV type 2 (HIV-2/ST) that differs from prototype HIV-2 strains in its inability to fuse with and kill susceptible CD4-bearing target cells. A proviral clone, termed JSP4-27, was identified to be transfection competent and to fully exhibit the noncytopathic and nonfusogenic properties of its parental isolate. Nucleotide sequence analysis of this clone revealed a genomic organization very similar to that of cytopathic HIV-2 strains and an overall nucleotide sequence homology of 88 to 90%. Amino acid sequence comparison confirmed the integrity of all major viral gene products in JSP4-27 but identified two amino acid sequence substitutions in its envelope fusion region. To investigate whether these mutations were responsible for the nonfusogenic phenotype of JSP4-27, we amplified, cloned, and sequenced the envelope fusion regions of four additional HIV-2/ST strains, two of which represented in vitro-generated, fusogenic and cytopathic variants of HIV-2/ST. The analysis showed that all HIV-2/ST strains examined, including the fusogenic variants, contained the same amino acid sequence changes. On the basis of these findings, we conclude that the attenuated phenotype of JSP4-27, and that of its parental virus, is not due to a direct alteration of the envelope fusion domain. Our results also show, for the first time, that individual replication-competent proviral clones can be representative of attenuated strains of HIV.

Illness and absenteeism among California highway patrol officers responding to hazardous material spills

Highway patrol officers are the primary responders to hazardous material spills in California, yet little is known regarding the health effects resulting from this exposure. A historical cohort study of 993 California highway patrol officers who responded to hazardous material spills in 1984 was conducted. The records of officers who were exposed to acutely toxic chemicals were followed for the subsequent week to determine if they demonstrated more absenteeism or illness compared to officers who were not exposed to toxic chemicals. No significant differences in the frequency of absenteeism or illness was found between the two groups during the week following exposure. No indication was found that exposure to hazardous materials during a highway patrol spill response results in increased absenteeism.

Individuals infected with HIV possess antibodies against IL-2

Studies are presented here which demonstrate that antibodies reacting with human interleukin-2 (IL-2) are present in the sera of patients infected with the human immunodeficiency virus (HIV). It is likely that these antibodies are present due to a homology between the HIV envelope protein and IL-2. The homologues are six amino acids in length corresponding to the carboxy terminus of gp41, Leu-Glu-Arg-Ile-Leu-Leu (LERILL), and residues 14-19 of secreted IL-2, Leu-Glu-His-Leu-Leu-Leu (LEHLLL). Thus, we questioned whether antibodies made against this HIV envelope peptide would cross-react with IL-2. Not only do a high percentage of the HIV-infected individuals tested here have antibodies against LERILL, but these antibodies cross-react with the IL-2 sequence, LEHLLL. Additional antigenic processing of IL-2 is suggested by the finding that epitopes other than this sixmer are also recognized by antibodies in patients' sera. Thus, these studies suggest a mechanism by which infection with HIV can induce a potentially suppressive autoimmune response. Specifically, antibodies against an HIV envelope peptide cross-react with an epitope in IL-2.

An examination of three spatial disease clustering methodologies

Patterns of disease in space are often analysed to determine whether a relationship exists between a disease outcome and environmental exposures. This report examines the performance of three cluster analytical methods when applied to a single data set. These methods, designed to assess the purely spatial variation of events, have been examined to assess their ability to detect clustering in an area where disease rates have previously been shown to be significantly elevated. The ability of these methods to detect spatial clustering was also examined using simulation techniques. All three methods were found to be poor at detecting spatially localized disease rates which were approximately three time the expected rate, as measured by the relative risk.

Methodological considerations in the study of parental occupational exposures and congenital malformations in offspring

The existence of hazardous substances in the workplace has raised concerns about the potential of these substances for adverse reproductive effects. Identification of associations between parental occupational exposures and congenital malformations in the offspring may provide the opportunity for preventing such exposures and thus reduce the risk of malformations. However, there are many methodological considerations inherent in studying the potential relation between parental occupational exposures and congenital malformations in the offspring. Considerations relating to outcome include methods and timing of ascertaining cases with malformations, diagnostic criteria, and problems in grouping malformations for purposes of analysis. With regard to measuring exposures, issues include methods for obtaining valid estimates of the nature, duration, timing of exposure, and exposure-response relationship. Other methodological issues discussed include selection of appropriate reference groups, sample size, and multiple hypothesis testing.

Identification of a novel retroviral gene unique to human immunodeficiency virus type 2 and simian immunodeficiency virus SIVMAC

Human and simian immunodeficiency-associated retroviruses are extraordinarily complex, containing at least five genes, tat, art, sor, R, and 3' orf, in addition to the structural genes gag, pol, and env. Recently, nucleotide sequence analysis of human immunodeficiency virus type 2 (HIV-2) and simian immunodeficiency virus SIVMAC revealed the existence of still another open reading frame, termed X, which is highly conserved between these two viruses but absent from HIV-1. In this report, we demonstrate for the first time that the X open reading frame represents a functional retroviral gene in both HIV-2 and SIVMAC and that it encodes a virion-associated protein of 14 and 12 kilodaltons, respectively. We also describe the production of recombinant TrpE/X fusion proteins in Escherichia coli and show that sera from some HIV-2-infected individuals specifically recognize these proteins.

Extensive variation of human immunodeficiency virus type-1 in vivo

Genotypic variation among independent isolates of human immunodeficiency virus type-1 (HIV-1) is well known, but its molecular basis and biological consequences are poorly understood. We examined the genesis of molecular variation in HIV-1 by sequential virus isolations from two chronically infected individuals and analysis of recombinant HIV-1 genomic clones. In three different virus isolates full-length HIV-1 clones were identified and found to consist, respectively, of 17, 9 and 13 distinguishable, but highly-related, viral genotypes. Thirty-five viral clones derived from two HIV-1 isolates obtained from the same individual but 16 months apart showed progressive change, yet were clearly related. Similar changes in the HIV-1 genome did not occur in vitro during virus isolation and amplification. The results indicate that HIV-1 variation in vivo is rapid, that a remarkably large number of related but distinguishable genotypic variants evolve in parallel and coexist during chronic infection, and that 'isolates' of HIV-1, unless molecularly or biologically cloned, generally consist of complex mixtures of genotypically distinguishable viruses.

Biologically diverse molecular variants within a single HIV-1 isolate

AIDS is a disorder characterized by a slow progressive impairment of immune function and by infection of human immunodeficiency viruses (HIV-1, HIV-2). Our knowledge of how these viruses cause disease in man, or how the related lentiviruses (visna and equine infectious anaemia virus) cause disease in animals, is still fragmentary. In particular, the significance of genetic variation in HIV-1, occurring within populations, within individuals and over periods of time, and the mechanisms of viral persistence remain unclear. To address these issues we prepared a series of proviral clones of HIV-1 originating from a single patient and compared their biological properties. Here we show that hybrid genomes (in which the envelope region of six viral clones were separately substituted into a prototype HIV-1 genome) generated viruses with widely differing capacity to grow in human T cells, cell lines and monocytoid cultures. These data suggest that extensive biological variation exists in vivo within an infected individual and is in part determined at the level of the viral envelope.

West African HIV-2-related human retrovirus with attenuated cytopathicity

Clinical and seroepidemiological studies in West Africa indicate that human immunodeficiency virus type 2 (HIV-2) is widespread and associated with immunodeficiency states of variable degree. In this study, an isolate of HIV-2 from a patient in Senegal was molecularly cloned and characterized. This isolate (HIV-2ST) was shown by hybridization and restriction enzyme analysis to be more related to the prototype HIV-2ROD than to other human or primate retroviruses. Cultures of HIV-2ST showed genotypic polymorphism, and clones of the virus had transmembrane envelope glycoproteins of 30 and 42 kilodaltons. Unlike other immunodeficiency viruses, HIV-2ST did not cause cell death or induce cell fusion in peripheral blood lymphocytes or in any of four CD4+ cell lines tested. Although HIV-2ST entered cells by a CD4-dependent mechanism and replicated actively, cell-free transmission of the virus was retarded at the level of cell entry. These findings suggest that immunodeficiency viruses prevalent in West African populations are members of the HIV-2 virus group and that certain strains of this virus have attenuated virulence.

Location and chemical synthesis of a binding site for HIV-1 on the CD4 protein

The human immunodeficiency virus type 1 (HIV-1) uses the CD4 protein as a receptor for infection of susceptible cells. A candidate structure for the HIV-1 binding site on the CD4 protein was identified by epitope mapping with a family of eight functionally distinct CD4-specific monoclonal antibodies in conjunction with a panel of large CD4-derived synthetic peptides. All of the seven epitopes that were located reside within two immunoglobulin-like disulfide loops situated between residues 1 and 168 of the CD4 protein. The CD4-specific monoclonal antibody OKT4A, a potent inhibitor of HIV-1 binding, recognized a site between residues 32 and 47 on the CD4 protein. By analogy to other members of the immunoglobulin superfamily of proteins, this particular region has been predicted to exist as a protruding loop. A synthetic analog of this loop (residues 25 to 58) showed a concentration-dependent inhibition of HIV-1-induced cell fusion. It is proposed that a loop extending from residues 37 to 53 of the CD4 protein is a binding site for the AIDS virus.

Relation of HTLV-4 to simian and human immunodeficiency-associated viruses

Human immunodeficiency virus type 1 (HIV-1) is the aetiologic agent of AIDS (acquired immune deficiency syndrome) in most countries and probably originated in Central Africa like the AIDS epidemic itself. Evidence for a second major group of human immunodeficiency-associated retroviruses came from a report that West African human populations like wild-caught African green monkeys had serum antibodies that reacted more strongly with a simian immunodeficiency virus (STLV-3Mac) (ref.6) than with HIV-1. Novel T-lymphotropic retroviruses were reported to have been isolated from healthy Senegalese West Africans (HTLV-4) (ref. 4) and from African green monkeys (STLV-3AGM) (ref. 7), and a different retrovirus (HIV-2) was identified in other West African AIDS patients. Genomic analysis of HIV-2 clearly distinguished it from STLV-3 (ref. 9), but restriction enzyme site-mapping of three different HTLV-4 isolates and six different STLV-3AGM isolates showed them to be essentially indistinguishable. In this report we clone, restriction map, and partially sequence three isolates of HTLV-4 (PK82, PK289, PK190) (ref. 4). We find that these viruses differ in nucleotide sequence from each other and from three isolates of STLV-3AGM (K78, K6W, K1) (ref. 7) by 1% or less. We also report the isolation of a T-lymphotropic retrovirus from the peripheral blood of a healthy Senegalese woman which hybridizes preferentially to HIV-2 specific DNA probes. We conclude that HTLV-4 (ref. 4) and STLV-3AGM (ref. 7) are not independent virus isolates and that HIV-2 is present in Senegal as it is in other West African countries.

Computer-assisted analysis of envelope protein sequences of seven human immunodeficiency virus isolates: prediction of antigenic epitopes in conserved and variable regions

Independent isolates of human immunodeficiency virus (HIV) exhibit a striking genomic diversity, most of which is located in the viral envelope gene. Since this property of the HIV group of viruses may play an important role in the pathobiology of the virus, we analyzed the predicted amino acid sequences of the envelope proteins of seven different HIV strains, three of which represent sequential isolates from a single patient. By using a computer program that predicts the secondary protein structure and superimposes values for hydrophilicity, surface probability, and flexibility, we identified several potential antigenic epitopes in the envelope proteins of the seven different viruses. Interestingly, the majority of the predicted epitopes in the exterior envelope protein (gp120) were found in regions of high sequence variability which are interspersed with highly conserved regions among the independent viral isolates. A comparison of the sequential viral isolates revealed that changes concerning the secondary structure of the protein occurred only in regions which were predicted to be antigenic, predominantly in highly variable regions. The membrane-associated protein gp41 contains no highly variable regions; about 80% of the amino acids were found to be conserved, and only one hydrophilic area was identified as likely to be accessible to antibody recognition. These findings give insight into the secondary and possible tertiary structure of variant HIV envelope proteins and should facilitate experimental approaches directed toward the identification and fine mapping of HIV envelope proteins.

Genetic variation in HTLV-III/LAV over time in patients with AIDS or at risk for AIDS

In a study of genetic variation in the AIDS virus, HTLV-III/LAV, sequential virus isolates from persistently infected individuals were examined by Southern blot genomic analysis, molecular cloning, and nucleotide sequencing. Four to six virus isolates were obtained from each of three individuals over a 1-year or 2-year period. Changes were detected throughout the viral genomes and consisted of isolated and clustered nucleotide point mutations as well as short deletions or insertions. Results from genomic restriction mapping and nucleotide sequence comparisons indicated that viruses isolated sequentially had evolved in parallel from a common progenitor virus. The rate of evolution of HTLV-III/LAV was estimated to be at least 10(-3) nucleotide substitutions per site per year for the env gene and 10(-4) for the gag gene, values a millionfold greater than for most DNA genomes. Despite this relatively rapid rate of sequence divergence, virus isolates from any one patient were all much more related to each other than to viruses from other individuals. In view of the substantial heterogeneity among most independent HTLV-III/LAV isolates, the repeated isolation from a given individual of only highly related viruses raises the possibility that some type of interference mechanism may prevent simultaneous infection by more than one major genotypic form of the virus.

Identification and characterization of conserved and variable regions in the envelope gene of HTLV-III/LAV, the retrovirus of AIDS

To determine the extent and nature of genetic variation present in independent isolates of HTLV-III/LAV, the nucleotide sequences of the entire envelope gene and parts of gag and pol were determined for two AIDS viruses. The results indicated that variation throughout the viral genome is extensive and that the envelope gene in particular is most highly variable. Within the envelope, changes were most prevalent within the extracellular region where clustered nucleotide substitutions and deletions/insertions were evident. Based on predicted secondary protein structure and hydrophilicity, these hypervariable regions represent potential antigenic sites. In contrast to the hypervariable regions, other sequences in the extracellular envelope and the overall envelope structure (including 18 of 18 cysteine residues), as well as most of the transmembrane region, were highly conserved.

Characteristics of hazardous material spills from reporting systems in California

Data on hazardous material releases that occurred between January 1, 1982 and September 30, 1983 in California were obtained from the California Highway Patrol (CHP) and the US Department of Transportation (DOT). The majority of incidents involved highway transport of hazardous materials, although some information was available on air, rail, and stationary facility releases. Vehicle accidents and failure of or damage to the container were the most frequent causes of releases. Proportionately more hazardous materials incidents occurred in early summer than at other times of the year, during weekdays, and daytime hours. The largest proportions of incidents involved the chemical categories of corrosives and fuels. Reported exposures and injuries to response personnel and other people at the scene were relatively few; no fatalities were reported. Few incidents were reported in both data sources, suggesting that the examination of only one data source would yield a gross underestimate of the total number of hazardous materials incidents in California. The lack of available denominator data limits the interpretation of the findings.

Genomic diversity of human T-lymphotropic virus type III (HTLV-III)

The DNA genomes of human T-lymphotropic virus type III (HTLV-III) isolated from 18 individuals with AIDS or who were at risk for AIDS were evaluated for evidence of variation. Although all of the 18 viral DNA's hybridized throughout their entire genomes to a full-length cloned probe of the original HTLV-III isolate, each of the 18 isolates showed a different restriction enzyme pattern. The number of restriction site differences between isolates ranged from only 1 site in 23 to at least 16 sites in 31. No particular viral genotype was associated with a particular disease state and 2 of the 18 patients had evidence of concurrent infection by more than one viral genotype. Propagation of three different viral isolates in vitro for up to 9 months did not lead to detectable changes in their restriction patterns. These findings indicate that different isolates of HTLV-III comprise a spectrum of highly related but distinguishable viruses and have important implications regarding the pathogenicity of HTLV-III and attempts to develop effective diagnostic, therapeutic, and preventive measures for this virus.

HTLV-III infection in brains of children and adults with AIDS encephalopathy

Unexplained debilitating dementia or encephalopathy occurs frequently in adults and children with the acquired immune deficiency syndrome (AIDS). Brains from 15 individuals with AIDS and encephalopathy were examined by Southern analysis and in situ hybridization for the presence of human T-cell leukemia (lymphotropic) virus type III (HTLV-III), the virus believed to be the causative agent of AIDS. HTLV-III DNA was detected in the brains of five patients, and viral-specific RNA was detected in four of these. In view of these findings and the recent demonstration of morphologic and genetic relatedness between HTLV-III and visna virus, a lentivirus that causes a chronic degenerative neurologic disease in sheep, HTLV-III should be evaluated further as a possible cause of AIDS encephalopathy.

Etiology of AIDS: biological and biochemical characteristics of HTLV-III

The newly identified human HTLV-III virus, the etiologic agent for AIDS, shares many of the biological and physicochemical properties common to a family of retroviruses named human T-cell leukemia (lymphotropic) viruses, or HTLV. Because of the similarities, and because of the uniform nomenclature for human T-cell leukemia (lymphotropic) viruses adopted at the first Cold Spring Harbor Meeting on HTLV (19, 79), this newly discovered virus associated with AIDS as HTLV-III was named HTLV-III. Other investigators making independent isolations of virus have suggested naming the virus lymphadenopathy virus or LAV (3, 16), immunodeficiency associated virus or IADV (48), AIDS-related virus (41). Immunological and nucleic acid comparison has now demonstrated that these viruses are, not surprisingly, very similar to HTLV-III (55, 63, 78). In view of the wide range of disease manifestations caused by the virus, and previous discussions concerning a uniform nomenclature for human T-lymphotropic retroviruses, it would seem ill-advised to restrict the name of this virus to one clinical manifestation of one disease. The frequent isolation of HTLV-III from patients with AIDS and ARC, the detection of antibodies specific for HTLV-III in nearly all patients with these diseases and in a high proportion of individuals at risk, and finally its effect on cells in vitro, leaves little doubt that HTLV-III is causatively involved in the development of these diseases. This etiologic association is further strengthened by the detection of HTLV-III infection in many instances where a direct cause-and-effect association can be made, e.g., hemophiliacs and children with AIDS, and blood from HTLV-III infected donors and the otherwise normal recipients of this blood who subsequently develop AIDS.

Molecular characterization of human T-cell leukemia (lymphotropic) virus type III in the acquired immune deficiency syndrome

The human T-cell leukemia (lymphotropic) virus type III (HTLV-III) appears to be central to the causation of the acquired immune deficiency syndrome (AIDS). Two full-length integrated proviral DNA forms of HTLV-III have now been cloned and analyzed, and DNA sequences of the virus in cell lines and fresh tissues from patients with AIDS or AIDS-related complex (ARC) have been characterized. The results revealed that (i) HTLV-III is an exogenous human retrovirus, approximately 10 kilobases in length, that lacks nucleic acid sequences derived from normal human DNA; (ii) HTLV-III, unlike HTLV types I and II, shows substantial diversity in its genomic restriction enzyme cleavage pattern; (iii) HTLV-III persists in substantial amounts in cells as unintegrated linear DNA, an uncommon property that has been linked to the cytopathic effects of certain animal retroviruses; and (iv) HTLV-III viral DNA can be detected in low levels in fresh (primary) lymphoid tissue of a minority of patients with AIDS or ARC but appears not to be present in Kaposi's sarcoma tissue. These findings have important implications concerning the biological properties of HTLV-III and the pathophysiology of AIDS and Kaposi's sarcoma.

Molecular cloning and analysis of a new variant of human T-cell leukemia virus (HTLV-ib) from an African patient with adult T-cell leukemia-lymphoma

We report the identification and characterization of a new variant of HTLV-I in an African patient with adult T-cell leukemia/lymphoma (ATL). Proviral sequences were detected by Southern blot analysis in three T-cell lines established from this patient's peripheral blood lymphocytes (PBL) and lymph-node cells. We molecularly cloned and analyzed proviruses from two of these cells lines, one established by direct culture of PBL and one established by co-cultivation of PBL with cord-blood T cells. These two HTLV clones contained full-length proviruses which were identical to each other in 44 out of 44 restriction enzyme sites. They were closely related to, but distinct from, the prototype HTLV-I, having divergence in their envelope and 5' pX regions and therefore represented a new variant of HTLV-I. We designated it as HTLV-Ib. Despite the genomic differences, however, HTLV-Ib retained its tropism for OKT4+ lymphocytes as well as its ability to initiate and maintain transformation of these cells. The finding of a variant of HTLV-I in this African ATL patient, along with the results of recent seroepidemiological studies, extends to the African continent the prevalence of HTLV-I associated malignancy previously identified in the Caribbean and Japan.

Molecular cloning and characterization of the HTLV-III virus associated with AIDS

We recently reported the isolation and characterization of a novel human T-lymphotropic retrovirus, HTLV-III, in patients with acquired immune deficiency syndrome (AIDS) and in those at risk for the disease. After extensive sero-epidemiological studies, together with numerous virus isolations from these patients, we concluded that HTLV-III is the causative agent of AIDS. Here we report the molecular cloning and characterization of two highly related but distinct forms of the HTLV-III genome. The viral genome is approximately 10 kilobases long and is detected in HTLV-III-infected cells but not in uninfected cells, including normal human tissue, indicating that this virus is exogenous to man. We also demonstrate distant nucleic acid sequence homology between the cloned genome of HTLV-III and those of HTLV-I and HTLV-II. The availability of the cloned HTLV-III genome will now allow an unambiguous comparison of this virus with other retroviruses that also have been associated with the pathogenesis of AIDS, and moreover, with facilitate the development of diagnostic and therapeutic measures in the treatment of AIDS.

Homology of genome of AIDS-associated virus with genomes of human T-cell leukemia viruses

A T lymphotropic virus found in patients with the acquired immune deficiency syndrome (AIDS) or lymphadenopathy syndrome has been postulated to be the cause of AIDS. Immunological analysis of this retrovirus and its biological properties suggest that it is a member of the family of human T-lymphotropic retroviruses known as HTLV. Accordingly, it has been named HTLV-III. In the present report it is shown by nucleic acid hybridization that sequences of the genome of HTLV-III are homologous to the structural genes (gag, pol, and env) of both HTLV-I and HTLV-II and to a potential coding region called pX located between the env gene and the long terminal repeating sequence that is unique to the HTLV family of retroviruses.

Genomes of evolutionarily divergent members of the human T-cell leukemia virus family (HTLV-I and HTLV-II) are highly conserved, especially in pX

Human T-cell leukemia virus (HTLV) is a family of related human T-lymphotropic retroviruses closely linked with certain human T-cell malignancies and associated with many cases of acquired immunodeficiency syndrome (AIDS). We isolated and molecularly cloned HTLV from patients with both types of clinical disorders and found by restriction endonuclease mapping and core and envelope protein analysis that at least two evolutionarily divergent viral subgroups exist, HTLV-I and HTLV-II. Previous studies have failed to detect significant nucleotide sequence homology between HTLV-I and HTLV-II even though these different members of the HTLV family share certain biologic properties such as T-cell tropism and transformation. To further test these viruses for conserved regions in their genomes, we examined hybridization between HTLV-I and HTLV-II by using Southern blotting and heteroduplex mapping at different melting points. These two techniques produced similar results, showing that HTLV-I and HTLV-II proviruses have, in fact, strongly conserved nucleotide sequences in the pX region and lesser although still substantial homology in the LTR, gag, pol, and env regions. These data provide experimental evidence that HTLV-II, like HTLV-I, contains pX sequences. Although the function of pX is unknown, its conservation in evolutionarily divergent human T-lymphotropic viruses implies a biologically important function. It is possible, but unproven, that pX could encode proteins involved in T-cell tropism, cell transformation, immune suppression, or other biologic actions characteristic of the HTLV family.

Quantification of platelet-bound IgG by 125I-Staphylococcal protein A in immune thrombocytopenic purpura and other thrombocytopenic disorders

In this report we describe the use of an 125I-Staphylococcal protein A (SPA) assay to measure platelet-bound IgG in the evaluation of 62 thrombocytopenic patients. Platelets from 150 normal subjects were found to bind 146 +/- 112 molecules of SPA per platelet (mean +/- 2 SD). Nineteen of 20 patients with untreated immune thrombocytopenia had platelet IgG values above this range, with 15 of 20 having values above 1,000 molecules of SPA per platelet. Patients with immune thrombocytopenic purpura by clinical criteria, but who had failed conventional therapy (corticosteroids or splenectomy), had a wide range of platelet IgG levels: 4 of 20 had normal values, 6 of 20 had minimally elevated levels in the range seen with nonimmune thrombocytopenia, and 10 of 20 had much higher values. Fifteen patients with thrombocytopenia of apparent nonimmune origin and 7 others with chronic stable thrombocytopenia of unknown etiology were found to have platelet IgG levels within or only slightly above the normal range. Because of its simplicity, accuracy, and clinical correlation, the 125I-SPA assay provides an important new approach for studying platelet IgG in thrombocytopenic states. The data obtained with this technique are similar to those found in immune hemolytic anemia and suggest that the platelet-bound IgG so measured has pathophysiologic relevance in immune thrombocytopenic purpura.

Immune thrombocytopenic purpura. Use of a 125I-labeled antihuman IgG monoclonal antibody to quantify platelet-bound IgG

We used a radiolabeled monoclonal antibody to the Fc portion of human IgG to measure platelet-bound IgG in 54 thrombocytopenic patients and in 48 normal controls. The control group had a mean (+/- 1 S.D.) of 169 +/- 79 IgG molecules bound per platelet--10 to 100 times lower than values generally reported with other assay techniques. Sixteen of 17 patients with untreated thrombocytopenic purpura considered to be of immune origin had values ranging from 790 to 13,095--levels well above those found in normal subjects and in patients with "nonimmune" thrombocytopenia (246 +/- 156). In a second group, consisting of 11 patients with "immune" thrombocytopenic purpura who did not respond to conventional therapy (corticosteroids or splenectomy), the values were quite divergent: two patients had levels in the normal range, three had levels in the range of subjects with nonimmune thrombocytopenia, and six had much higher levels. Measurement of platelet-bound IgG with this monoclonal-antibody technique can help differentiate between immune and nonimmune thrombocytopenias. Low platelet counts in patients who have immune thrombocytopenia according to clinical criteria but are resistant to therapy may be related to factors other than IgG antibody.