Magnitude of Mycobacterium tuberculosis transmission among household and non-household contacts of TB patients

<sec id="st1"> <title>SETTING</title> The household and non-household contacts of patients with tuberculosis (TB) face varying degrees of risk of infection by Mycobacterium tuberculosis. </sec> <sec id="st2"> <title>OBJECTIVE</title> To quantify new infection and to determine the risk factors associated with new infection among named contacts in San Francisco, CA, USA. </sec> <sec id="st3"> <title>DESIGN</title> We performed a cohort study in patients with culture-positive pulmonary TB. We analyzed patient, contact, environmental and bacterial characteristics. </sec> <sec id="st4"> <title>RESULTS</title> Of the 2422 contacts named by 256 patients, 149 (6.2%) had new infection due to recent transmission from 79 (30.9%) patients. Of the 149 new infections, 87 (58.4%) occurred among household contacts and 62 (41.6%) among non-household contacts. Numerous acid-fast bacilli in sputum (odds ratio [OR] 2.64, 95%CI 1.32-5.25) and contacts being named by more than one patient (OR 2.90, 95%CI 1.23-6.85) were associated with new infection among household contacts. Being older than 50 years (OR 1.93, 95%CI 1.09-3.41) and an Asian/Pacific Islander (OR 3.09, 95%CI 1.50-6.37) were associated with new infection among non-household contacts. </sec> <sec id="st5"> <title>CONCLUSIONS</title> Fewer than one third of patients caused new infection to his/her contacts. A substantial proportion of transmission resulting in new infection occurred outside of the household. The risk factors for infection among household and non-household contacts are different and should be considered when prioritizing control interventions. </sec>.

Interplay of strain and race/ethnicity in the innate immune response to M. tuberculosis

Background

The roles of host and pathogen factors in determining innate immune responses to M. tuberculosis are not fully understood. In this study, we examined host macrophage immune responses of 3 race/ethnic groups to 3 genetically and geographically diverse M. tuberculosis lineages.

Methods

Monocyte-derived macrophages from healthy Filipinos, Chinese and non-Hispanic White study participants (approximately 45 individuals/group) were challenged with M. tuberculosis whole cell lysates of clinical strains Beijing HN878 (lineage 2), Manila T31 (lineage 1), CDC1551 (lineage 4), the reference strain H37Rv (lineage 4), as well as with Toll-like receptor 2 agonist lipoteichoic acid (TLR2/LTA) and TLR4 agonist lipopolysaccharide (TLR4/LPS). Following overnight incubation, multiplex assays for nine cytokines: IL-1β, IL-2, IL-6, IL-8, IL-10, IL-12p70, IFNγ, TNFα, and GM-CSF, were batch applied to supernatants.

Results

Filipino macrophages produced less IL-1, IL-6, and more IL-8, compared to macrophages from Chinese and Whites. Race/ethnicity had only subtle effects or no impact on the levels of IL-10, IL-12p70, TNFα and GM-CSF. In response to the Toll-like receptor 2 agonist lipoteichoic acid (TLR2/LTA), Filipino macrophages again had lower IL-1 and IL-6 responses and a higher IL-8 response, compared to Chinese and Whites. The TLR2/LTA-stimulated Filipino macrophages also produced lower amounts of IL-10, TNFα and GM-CSF. Race/ethnicity had no impact on IL-12p70 levels released in response to TLR2/LTA. The responses to TLR4 agonist lipopolysaccharide (TLR4/LPS) were similar to the TLR2/LTA responses, for IL-1, IL-6, IL-8, and IL-10. However, TLR4/LPS triggered the release of less IL-12p70 from Filipino macrophages, and less TNFα from White macrophages.

Conclusions

Both host race/ethnicity and pathogen strain influence the innate immune response. Such variation may have implications for the development of new tools across TB therapeutics, immunodiagnostics and vaccines.

Impact of Euro-American sublineages of Mycobacterium tuberculosis on new infections among named contacts

BACKGROUND

The impact of demographic, clinical, and bacterial factors on new infection by Euro-American lineage Mycobacterium tuberculosis among contacts of patients with tuberculosis (TB) has not been evaluated.

OBJECTIVE

To describe the risk factors for new infection by Euro-American M. tuberculosis sublineages in San Francisco, California.

DESIGN

We included contacts of patients with TB due to Euro-American M. tuberculosis. Sublineages were determined by large-sequence polymorphisms. We used tuberculin skin testing or QuantiFERON®-TB Gold In-Tube to identify contacts with new infection. Regression models with generalized estimating equations were used to determine the risk factors for new infection.

RESULTS

We included 1488 contacts from 134 patients with TB. There were 79 (5.3%) contacts with new infection. In adjusted analyses, contacts of patients with TB due to region of difference 219 M. tuberculosis sublineage were less likely to have new infection (OR 0.23, 95%CI 0.06-0.84) than those with other sublineages. Other risk factors for new infection were contacts exposed to more than one patient with TB, contacts exposed for 30 days, or contacts with a history of smoking or excessive alcohol consumption.

CONCLUSIONS

In addition to well-known exposure and clinical characteristics, bacterial characteristics independently contribute to the transmissibility of TB in San Francisco.

Clinical and bacteriological characteristics associated with clustering of multidrug-resistant tuberculosis

SETTING

The impact of the genetic characteristics of Mycobacterium tuberculosis on the clustering of multidrug-resistant tuberculosis (MDR-TB) has not been analyzed together with clinical and demographic characteristics.

OBJECTIVE

To determine factors associated with genotypic clustering of MDR-TB in a community-based study.

DESIGN

We measured the proportion of clustered cases among MDR-TB patients and determined the impact of clinical and demographic characteristics and that of three M. tuberculosis genetic characteristics: lineage, drug resistance-associated mutations, and rpoA and rpoC compensatory mutations.

RESULTS

Of 174 patients from California and Texas included in the study, the number infected by East-Asian, Euro-American, Indo-Oceanic and East-African-Indian M. tuberculosis lineages were respectively 70 (40.2%), 69 (39.7%), 33 (19.0%) and 2 (1.1%). The most common mutations associated with isoniazid and rifampin resistance were respectively katG S315T and rpoB S531L. Potential compensatory mutations in rpoA and rpoC were found in 35 isolates (20.1%). Hispanic ethnicity (OR 26.50, 95%CI 3.73-386.80), infection with an East-Asian M. tuberculosis lineage (OR 30.00, 95%CI 4.20-462.40) and rpoB mutation S531L (OR 4.03, 95%CI 1.05-23.10) were independent factors associated with genotypic clustering.

CONCLUSION

Among the bacterial factors studied, East-Asian lineage and rpoB S531L mutation were independently associated with genotypic clustering, suggesting that bacterial factors have an impact on the ability of M. tuberculosis to cause secondary cases.

Reduced sensitivity of the QuantiFERON(®) test in diabetic patients with smear-negative tuberculosis

SETTING

Immunosuppressive conditions have been associated with low sensitivity of interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST) for the diagnosis of tuberculosis (TB). However, no systematic analysis of patient and bacterial characteristics has been performed before.

OBJECTIVE

To determine the sensitivity and the risk factors for false-negative QuantiFERON(®)-TB (QFT) assay and TST in TB patients.

DESIGN

We performed a retrospective analysis of data collected in a community-based study of TB in San Francisco, CA, USA. We included 300 TB patients who underwent QFT and TST.

RESULTS

The risk factors for false-negative QFT were human immunodeficiency virus infection and the use of QuantiFERON(®)-TB Gold. In patients with sputum smear-negative TB, diabetes mellitus (DM) was associated with false-negative QFT (OR 2.85, 95%CI 1.02-7.97, P = 0.045). TST sensitivity was higher than QFT sensitivity in DM patients (OR 9.46, 95%CI 2.53-35.3).

CONCLUSIONS

In San Francisco, QFT sensitivity was lower than that of TST, especially in patients with DM. Stratified analysis by sputum smear results showed that this association was specific to smear-negative TB. In contrast, TST was not affected by the presence of DM.

Sensitivity and specificity of fluorescence microscopy for diagnosing pulmonary tuberculosis in a high HIV prevalence setting

SETTING

Mulago Hospital, Kampala, Uganda.

OBJECTIVE

To evaluate the diagnostic performance of fluorescence microscopy (FM) for diagnosing pulmonary tuberculosis (TB) in a high human immunodeficiency virus (HIV) prevalence setting.

DESIGN

Consecutive in-patients with cough for >2 weeks submitted two sputum specimens for smear microscopy. Smears were examined by conventional light microscopy (CM) and FM. The performance of the two methods was compared using mycobacterial culture as a reference standard.

RESULTS

A total of 426 patients (82% HIV-infected) were evaluated. FM identified 11% more smear-positive patients than CM (49% vs. 38%, P < 0.001). However, positive FM results were less likely than positive CM results to be confirmed by culture when smears were read as either 'scanty' (54% vs. 90%, P < 0.001) or 1+ (82% vs. 91%, P = 0.02). Compared to CM, the sensitivity of FM was higher (72% vs. 64%, P = 0.005), and the specificity lower (81% vs. 96%, P < 0.001). In receiver operating characteristic analysis, maximum area under the curve for FM was obtained at a threshold of >4 acid-fast bacilli/100 fields (sensitivity 68%, specificity 90%).

CONCLUSION

Although FM increases the sensitivity of sputum smear microscopy, additional data on FM specificity and on the clinical consequences associated with false-positive FM results are needed to guide implementation of this technology in high HIV prevalence settings.

A 13-year molecular epidemiological analysis of tuberculosis in San Francisco

BACKGROUND

We examined the molecular epidemiology of tuberculosis (TB) in San Francisco during a 13-year period encompassing the peak of TB resurgence and subsequent decline to historic low levels.

OBJECTIVE

To compare rates of TB caused either by rapid progression of recent Mycobacterium tuberculosis infection or by reactivation of latent infection.

METHODS

All TB cases reported from 1991 to 2003 were included. Genotyping was performed to identify clustered cases.

RESULTS

The annual TB case rate decreased significantly from 50.8 to 28.8 cases/100000 persons from 1992 to 1999 (P < 0.0001). After 1999, no significant decrease was observed for the population as a whole or in any subgroup examined. Similarly, the rate of clustered cases decreased significantly from 1992 to 1999 (11.4 to 3.1 cases/100000, P < 0.0001). Although the rate of non-clustered cases also declined significantly (25.6 to 17.6 cases/100,000, P < 0.0001), there was a disproportionate reduction in clustered cases (94.7% vs. 50.8%, P < 0.0001). Neither clustered nor non-clustered cases decreased significantly after 1999.

CONCLUSIONS

TB case rates reached a plateau despite ongoing application of control measures implemented in 1993. These data suggest that intensification of measures designed to identify and treat persons with latent TB infection will be necessary to further reduce TB incidence.

Primary care physicians' experience with disease management programs

OBJECTIVE

To examine primary care physicians' perceptions of how disease management programs affect their practices, their relationships with their patients, and overall patient care.

DESIGN

Cross-sectional mailed survey.

SETTING

The 13 largest urban counties in California.

PARTICIPANTS

General internists, general pediatricians, and family physicians.

MEASUREMENTS AND MAIN RESULTS

Physicians' self-report of the effects of disease management programs on quality of patient care and their own practices. Respondents included 538 (76%) of 708 physicians: 183 (34%) internists, 199 (38%) family practitioners, and 156 (29%) pediatricians. Disease management programs were available 285 to (53%) physicians; 178 had direct experience with the programs. Three quarters of the 178 physicians believed that disease management programs increased the overall quality of patient care and the quality of care for the targeted disease. Eighty-seven percent continued to provide primary care for their patients in these programs, and 70% reported participating in major patient care decisions. Ninety-one percent reported that the programs had no effect on their income, decreased (38%) or had no effect (48%) on their workload, and increased (48%)) their practice satisfaction.

CONCLUSIONS

Practicing primary care physicians have generally favorable perceptions of the effect of voluntary, primary care-inclusive, disease management programs on their patients and on their own practice satisfaction.

Correlates of heavy substance use among young gay and bisexual men: The San Francisco Young Men's Health Study

Correlates of heavy substance use among a household-based sample of young gay and bisexual men (n=428) were identified and the odds ratio (OR) was calculated. A total of 13.6% reported frequent, heavy alcohol use and 43% reported polydrug use. Compared with men employed in professional occupations, men in service positions (OR=3.77) and sales positions (OR=2.51) were more likely to be heavy alcohol consumers. Frequent gay bar attendance and multiple sex partners were related to heavy alcohol use, as well as to polydrug use. Polydrug users were more likely to be HIV seropositive (OR=2.05) or of unknown HIV serostatus (OR=2.78). HIV serostatus was similarly related to frequent drug use. These correlates of heavier substance use among young gay and bisexual men could be used to identify and intervene early with members of this population who are at risk of substance misuse, as well as HIV/AIDS risk.

Friend or foe? How primary care physicians perceive hospitalists

BACKGROUND

Increased use of hospitalists is redefining the role of primary care physicians. Whether primary care physicians welcome this transition is unknown. We examined primary care physicians' perceptions of how hospitalists affect their practices, their patient relationships, and overall patient care.

METHODS

A mailed survey of randomly selected general internists, general pediatricians, and family practitioners with experience with hospitalists practicing in California.

MAIN OUTCOME MEASURES

Physicians' self-reports of hospitalists' effects on quality of patient care and on their own practices.

RESULTS

Seven hundred eight physicians were eligible for this study, and there was a 74% response rate. Of the 524 physicians who responded, 34% were internists, 38% were family practitioners, and 29% were pediatricians. Of the 524 respondents, 335 (64%) had hospitalists available to them and 120 (23%) were required to use hospitalists for all admissions. Physicians perceived hospitalists as increasing (41%) or not changing (44%) the overall quality of care and perceived their practice style differences as neutral or beneficial. Twenty-eight percent of primary care physicians believed that the quality of the physician-patient relationship decreased; 69% reported that hospitalists did not affect their income; 53% believed that hospitalists decreased their workload; and 50% believed that hospitalists increased practice satisfaction. In a multivariate model predicting physician perceptions, internists, physicians who attributed loss of income to hospitalists, and physicians in mandatory hospitalist systems viewed hospitalists less favorably.

CONCLUSIONS

Practicing primary care physicians have generally favorable perceptions of hospitalists' effect on patients and on their own practice satisfaction, especially in voluntary hospitalist systems that decrease the workload of primary care physicians and do not threaten their income. Primary care physicians, particularly internists, are less accepting of mandatory hospitalist systems. Arch Intern Med. 2000;160:2902-2908

Obtaining HIV test results with a home collection test kit in a community telephone sample

OBJECTIVES

To test the feasibility of obtaining HIV test results by home collection kit from a probability telephone sample of men who have sex with men (MSM).

METHODS

A quota sample of 615 MSM previously interviewed by the Urban Men's Health Study phone survey in Chicago, Los Angeles, New York City, and San Francisco were re-contacted and offered an HIV test using an oral specimen (Orasure) home collection kit.

RESULTS

Eighty percent consented to be mailed a kit, and 84% returned a specimen, for a 67% participation rate. All self-reported HIV-positive persons tested positive (77 of 77); 4 of 266 (1.5%) with a prior negative test and 2 of 69 (2.9%) with no prior positive HIV test result. Participation was associated with self-reported prior HIV test status-HIV-positive (83%), HIV-negative (68%), or no prior HIV test result (54%)-and marginally associated with New York City residence after adjustment for HIV status (odds ratio = 0.7; 95% confidence interval, 0.4-1.1; p =.08).

CONCLUSIONS

These results suggest that urban MSM identified and interviewed by telephone will participate in home collection HIV testing. This methodology could be used to produce population-based estimates of HIV seroprevalence and seroincidence in MSM and could probably be extended to other populations and other viral infections.

Invited commentary: determining specific sexual practices associated with human herpesvirus 8 transmission

Laboratory and epidemiologic studies have established human herpesvirus 8 (HHV8) as an etiologic agent of Kaposi's sarcoma. With strong evidence linking HHV8 infection with the number of sexual partners among homosexual men, the challenge now is to determine the specific sexual acts associated with HHV8 transmission. Initial studies of specific practices, however, have differed in their conclusions; the paper by Dukers et al. in this issue of the Journal is the first to associate penile-oral intercourse with HHV8 transmission. Many sources of bias may contribute to the conflicting findings of studies reported to date: HHV8 research still lacks an adequately specific and sensitive serologic assay; identification of relevant exposure periods and measurement of sexual practices are imperfect; and sufficient adjustment for confounding is problematic. These numerous potential biases may be particularly important when trying to detect underlying associations that may be of low-order magnitude. The study by Dukers et al. (Am J Epidemiol 2000;151:213-24) is an important contribution to research on HHV8 transmission, but we do not yet know enough about the possible sexual routes of transmission to recommend avoiding any single behavior. For now, the best prevention advice is to reinforce the more general safe sex practices that have been promoted to prevent human immunodeficiency virus and other sexually transmitted diseases.

Use of epidemiologically well-defined subjects and existing immunofluorescence assays to calibrate a new enzyme immunoassay for human herpesvirus 8 antibodies

Agreement between assays for the detection of human herpesvirus 8 (HHV-8) antibodies has been limited. In part, this disagreement has been because assay calibration (i.e., differentiating positive from negative results) has not been done in a standardized fashion with reference to a wide spectrum of HHV-8-infected (true-positive) and HHV-8-uninfected (true-negative) persons. To describe the performance of an assay for HHV-8 antibodies more accurately, we used epidemiologically well-characterized subjects in conjunction with testing on two existing immunofluorescence assays for HHV-8 antibodies to define two groups: a group of 135 HHV-8-infected individuals (true positives), including Kaposi's sarcoma patients and those asymptomatically infected, and a group of 234 individuals with a high likelihood of being HHV-8 uninfected (true negatives). A new enzyme immunoassay (EIA), using lysed HHV-8 virion as the antigen target, was then developed. With the above true positives and true negatives as references, the sensitivity and specificity of the EIA associated with different cutoff values were determined. At the cutoff that maximized both sensitivity and specificity, sensitivity was 94% and specificity was 93%. When the EIA was used to test a separate validation group, a distribution of seropositivity that matched that predicted for the agent of Kaposi's sarcoma was observed: 55% of homosexual men were seropositive, versus 6% seropositivity in a group of children, women, and heterosexual men. It is proposed that the EIA has utility for large-scale use in a number of settings and that the calibration method described can be used for other assays, both to more accurately describe the performance of these assays and to permit more-valid interassay comparison.

Characterization of apelin, the ligand for the APJ receptor

The apelin peptide was recently discovered and demonstrated to be the endogenous ligand for the G protein-coupled receptor, APJ. A search of the GenBank databases retrieved a rat expressed sequence tag partially encoding the preproapelin sequence. The GenBank search also revealed a human sequence on chromosome Xq25-26.1, containing the gene encoding preproapelin. We have used the rat sequence to screen a rat brain cDNA library to obtain a cDNA encoding the full-length open reading frame of rat preproapelin. This cDNA encoded a protein of 77 amino acids, sharing an identity of 82% with human preproapelin. Northern and in situ hybridization analyses revealed both human and rat apelin and APJ to be expressed in the brain and periphery. Both sequence and mRNA expression distribution analyses revealed similarities between apelin and angiotensin II, suggesting they that share related physiological roles. A synthetic apelin peptide was injected intravenously into male Wistar rats, resulting in immediate lowering of both systolic and diastolic blood pressure, which persisted for several minutes. Intraperitoneal apelin injections induced an increase in drinking behavior within the first 30 min after injection, with a return to baseline within 1 h.

Name-based surveillance and public health interventions for persons with HIV infection. Multistate Evaluation of Surveillance for HIV Study Group

Name-based surveillance of HIV infection is the law in 31 U.S. states but remains controversial. This policy can be advocated solely to support surveillance of the epidemic, but a frequent argument is that it also provides a public health benefit by allowing follow-up of HIV-infected persons. These persons can then receive timely medical care and can be assisted with notifying sex and needle-sharing partners. Few comparative data are available to evaluate the outcomes of these interventions. In five states with name-based surveillance of HIV infection, the Multistate Evaluation of Surveillance for HIV Study Group surveyed a cross-sectional probability sample of persons with AIDS who tested positive for HIV before the date of their AIDS diagnosis. Health department follow-up of a reported HIV infection was not associated with more timely receipt of medical care after a positive HIV test result. Only 8.6% of persons who delayed medical care after their first positive HIV test result gave concern about being reported by name as a reason; no person gave it as the main reason. Persons who were tested anonymously and those who were tested confidentially did not differ in the mean number of sex and needle-sharing partners notified: Those tested anonymously reported personally notifying 3.85 sex and needle-sharing partners, and those tested confidentially reported notifying-personally and through the health department-3.80 partners. Many researchers and policymakers believe that name-based surveillance of HIV infection will have positive or negative effects on partner notification and access to health care. These results suggest that the potential for such effects has been exaggerated.

Kaposi's sarcoma-associated herpesvirus and sexual transmission of cancer risk

The epidemiology of AIDS-related Kaposi's sarcoma (KS) predicted that a nonubiquitous sexually transmitted agent was central to its etiology. An assessment of Hill's criteria for causality reveals there is now sufficient evidence to declare Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, a necessary, albeit not sufficient, cause of KS. The most compelling evidence comes from longitudinal studies presented in the past year that demonstrate that KSHV infection temporally precedes and is independently associated with AIDS-related KS even after adjustment for other potential etiologic factors. In the United States and Northern Europe, many studies have now shown that KSHV can be sexually transmitted among homosexual men, but determining specific routes of sexual transmission is methodologically challenging, and initial results are conflicting. Data are also emerging that demonstrate nonsexual modes of transmission. Spread via renal allograft appears to occur, and in endemic areas of Europe and Africa, nonsexual horizontal and perhaps vertical spread are the dominant modes of transmission.

Impact of bacterial pneumonia and Pneumocystis carinii pneumonia on human immunodeficiency virus disease progression. Pulmonary Complications of HIV Study Group

The course of pneumonia caused by pyogenic bacteria and Pneumocystis carinii was examined in a multicity cohort study of HIV infection. The median duration of survival among 150 individuals following initial bacterial pneumonia was 24 months, compared with 37 months among 299 human immunodeficiency virus (HIV)-infected control subjects matched by study site and CD4 lymphocyte count (P<.001). For 152 subjects with P. carinii pneumonia, median survival was 23 months, compared with 30 months for 280 matched control subjects (P = .002). Median durations of survival associated with the two types of pneumonia differed by only 47 days, despite a higher median CD4 lymphocyte count associated with bacterial pneumonia. These results suggest that both P. carinii pneumonia and bacterial pneumonia are associated with a significantly worse subsequent HIV disease course. The similarity of prognosis after one episode of bacterial pneumonia vs. an AIDS-defining opportunistic infection and the proportion of cases occurring in association with a CD4 lymphocyte count of >200 suggest that measures to prevent bacterial pneumonia should be emphasized.

Gay men report high rates of unprotected anal sex with partners of unknown or discordant HIV status

OBJECTIVE

To examine patterns and factors that correlate with unprotected anal intercourse (UAI) practices among San Francisco gay men, including UAI with partners of unknown or different HIV antibody status.

DESIGN

A longitudinal cohort recruited for the San Francisco Young Men's Health Study in 1992; re-assessed annually.

PARTICIPANTS AND METHODS

A sample of 510 unmarried gay men who were 18 to 29 years at baseline were originally recruited as part of a larger population and referral-based sample. Subjects participated in four consecutive waves of data collection.

RESULTS

The prevalence of reported unprotected anal intercourse (UAI) increased from 37% to 50% between 1993-1994 and 1996-1997. Almost half of all men who reported UAI in 1996-1997 indicated that it occurred with a partner of unknown or discordant HIV antibody status. This high-risk practice correlated with greater numbers of male sex partners, use of nitrite inhalants, sex in commercial sex environments, perceived difficulty controlling sexual risk-taking, and negative emotional reactions following UAI.

CONCLUSIONS

These data on increasing rates of sexual risk-taking further confirm trends in sexual behavior previously suggested by rising rates of rectal gonorrhea in this population. Additional and sustained prevention efforts are urgently needed in light of the very high background rates of HIV infection found among gay men in San Francisco.

Sexual transmission and the natural history of human herpesvirus 8 infection

BACKGROUND

Although human herpesvirus 8 (HHV-8) has been suspected to be the etiologic agent of Kaposi's sarcoma, little is known about its seroprevalence in the population, its modes of transmission, and its natural history.

METHODS

The San Francisco Men's Health Study, begun in 1984, is a study of a population-based sample of men in an area with a high incidence of human immunodeficiency virus (HIV) infection. We studied all 400 men infected at base line with HIV and a sample of 400 uninfected men. Base-line serum samples were assayed for antibodies to HHV-8 latency-associated nuclear antigen (anti-LANA). In addition to the seroprevalence and risk factors for anti-LANA seropositivity, we analyzed the time to the development of Kaposi's sarcoma.

RESULTS

Anti-LANA antibodies were found in 223 of 593 men (37.6 percent) who reported any homosexual activity in the previous five years and in none of 195 exclusively heterosexual men. Anti-LANA seropositivity correlated with a history of sexually transmitted diseases and had a linear association with the number of male sexual-intercourse partners. Among the men who were infected with both HIV and HHV-8 at base line, the 10-year probability of Kaposi's sarcoma was 49.6 percent. Base-line anti-LANA seropositivity preceded and was independently associated with subsequent Kaposi's sarcoma, even after adjustment for CD4 cell counts and the number of homosexual partners.

CONCLUSIONS

The prevalence of HHV-8 infection is high among homosexual men, correlates with the number of homosexual partners, and is temporally and independently associated with Kaposi's sarcoma. These observations are further evidence that HHV-8 has an etiologic role in Kaposi's sarcoma and is sexually transmitted among men.

Potent 'new pressor protein' related to coagulation factor XII is potentiated by inhibition of angiotensin converting enzyme

BACKGROUND

'New pressor protein' was observed after tryptic activation of human and rat plasma in vitro, which is done conventionally for prorenin measurements.

RESULTS

It is potently pressor, heat labile, possesses enzyme activity, and has a relative molecular mass > 30 kDa with isoelectric point(s) 4.7-4.9. New pressor protein equivalent to only 0.01 ml human, or rat, plasma injected intravenously quickly raises systolic blood pressure in 300 g anesthetized, ganglion-blocked, bioassay rats by about 15 mmHg. For unknown reasons, this is potentiated to about 45 mmHg after treatment with angiotensin I converting enzyme inhibitors (such as captopril and enalapril). New pressor protein activity in rats remains normal 24 h after bilateral nephrectomy, suggesting that it has an extrarenal origin and, furthermore, excluding the possibility of an association with renin-angiotensin system. Systolic blood pressure elevation is greater than the diastolic one, implicating cardiotonic effects. Human plasma new pressor protein was purified using standard biochemical techniques and its N-terminal sequence (19 residues) found to be homologous with the beta factor XIIa fragment of coagulation factor XII. This was supported by demonstrating inhibition of new pressor protein activity in vitro using the factor XII-specific corn trypsin inhibitor. Also, human new pressor protein activity in humans congenitally deficient in coagulation factor XII is very low. The high potency and multiphasic, cardiotonic effects of injected new pressor protein suggest that it interacts synergistically with other systems in the body. This was confirmed by showing that, within 10 min of total bilateral adrenalectomy, responses to new pressor protein decreased markedly.

CONCLUSIONS

New pressor protein's action requires adrenal (medullary?) involvement, but its mechanism of action and that of its potentiation by angiotensin converting enzyme inhibitors remain unknown. The physiologic and clinical relevance of these observations depends on whether activation of new pressor protein can occur in vivo.

Potent blood pressure raising effects of activated coagulation factor XII

A new pressor protein (NPP) in trypsin-activated human plasma was recently reported, whose blood pressure raising effects in bioassay rats are potentiated 300% after treatment with angiotensin I converting enzyme inhibitors (captopril). Pure NPP showed good N-terminal sequence homology with coagulation factor beta FXIIa, and little of it was present in FXII-deficiency plasmas (> or = 99%, n = 4). The present experiments confirm this in four additional FXII-deficiency plasmas. Further, (i) adding highly purified coagulation FXII, alpha FXIIa, or beta FXIIa fragment restores pressor activity to such plasmas, but only after activation with trypsin. (ii) Such requirement for trypsin suggests that no factor is structurally identical with NPP to begin with but that all can be activated to NPP. (iii) When injected directly by vein, only beta FXIIa is pressor, suggesting closest structural resemblance to NPP and (or) readiest endogenous conversion to NPP. (iv) NPP and beta FXIIa are cardiotonic: they both raise systolic pressure more than the diastolic, with a concomitant increase in heart rate. These observations support NPP's structural relationship with beta FXIIa and connect coagulation and blood pressure mechanisms in a new way, whose significance to the physiology and pathophysiology of blood pressure regulation remains to be established.

Treatment of X-linked hereditary nephritis in Samoyed dogs with angiotensin converting enzyme (ACE) inhibitor

X-linked hereditary nephritis (HN) in Samoyed dogs is a model for human HN (Alport's syndrome). Angiotensin converting enzyme (ACE) inhibitors have been shown to slow the progression of renal disease in animal models and human patients. To determine the effect of ACE inhibitor treatment on X-linked HN in Samoyed dogs, a group of affected and a group of normal males were each randomly divided into two subgroups, which were either treated with an ACE inhibitor or left untreated. ACE inhibitor treatment caused significant increases (P < 0.05) in plasma renin activity in normal and affected dogs, confirming its effectiveness, but did not lower systemic blood pressure. Three of four affected treated dogs had improved weight gains and, overall, treated dogs survived 1.36 times longer than affected untreated dogs (P < 0.05). ACE inhibitor treatment of affected dogs significantly delayed (P < 0.05) the onset of an increase in serum creatinine concentration, tended to delay the decline of glomerular filtration rate and effective renal plasma flow (ERPF), significantly improved (P < 0.05) the ERPF at 110-154 days of age, and significantly slowed (P < 0.01) the rate of increase of proteinuria. Affected treated dogs showed a significant (P < 0.05) transient reduction in glomerular basement membrane splitting. Thus, ACE inhibitor treatment of Samoyed dogs with X-linked HN produced beneficial effects with respect to renal function, renal structure, and survival.

Primary care and patient perceptions of access to care

BACKGROUND

Although much is known about how insurance affects access to care, it is unclear whether good primary care contributes to access. The purpose of this study was to determine how optimal primary care given by providers at a regular place of care, defined in terms of continuity, comprehensiveness, communication, and availability, contributed to perceptions of access to care in a large population-based probability sample of adults.

METHODS

Data were from a cross-sectional survey of 6674 English- and Spanish-speaking adults 18 to 64 years of age, randomly sampled from 41 urban California communities with a range of levels of access to care.

RESULTS

Following adjustment for sociodemographics and need for care, we found that having "optimal" primary care contributed independently to improved self-rated access, as did having health insurance, a regular place, and a regular provider. The largest difference n access was between having any health insurance and not having insurance. Once insurance was available, each additional element contributed in a cumulative manner to self-rated access. For those with insurance and a regular place, adding optimal primary care improved self-rated access to an extent similar to adding a regular provider.

CONCLUSIONS

We conclude that although providing insurance to the uninsured is the most effective means of improving self-rated access, the other elements each improve access as well. Once insurance and a regular place are provided, good primary care at that place may be equivalent to having a regular provider in terms of perceived access. Results support promotion of primary care as a model of health care that encourages good access.

Predictors of Pneumocystis carinii pneumonia in HIV-infected persons. Pulmonary Complications of HIV Infection Study Group

The Pulmonary Complications of HIV Infection Study is a prospective, multicenter, observational study evaluating pulmonary disease among HIV-infected persons. For approximately 52 mo, 1,182 HIV-infected subjects were followed. All participants were evaluated for pulmonary disease on a predetermined schedule. There were 145 episodes of Pneumocystis carinii pneumonia (PCP). Low CD4 count correlated with risk of PCP (p < 0.0001); 79% had CD4 counts less than 100/microl and 95% had CD4 counts less than 200/microl. Subtle changes in diffusing capacity for carbon monoxide (DLCO) were associated with PCP. Univariate analysis identified recurrent undiagnosed fevers, night sweats, oropharyngeal thrush, and unintentional weight loss to be associated with risk among persons with CD4 counts above 200/microl. Subjects in whom CD4 counts declined to below 200/microl and who were not receiving preventive therapy were nine times more likely to develop PCP within 6 mo compared with subjects who received such therapy. A strong trend toward differences between the sexes was detected. Black subjects had less than one third the risk of developing PCP as did white subjects (p < 0.0001). There was no significant difference in risk by HIV transmission category, study site, frequency of follow-up, age, education, smoking history, or use of antiretroviral therapy. Multivariable analysis revealed low CD4 lymphocyte count (p < 0.0001), use of prophylaxis (p < 0.0001), racial differences (p < 0.0001), and declining DLCO (p = 0.015) to influence risk. Constitutional signs and symptoms indicate increased risk for PCP among HIV-infected persons with CD4 counts above 200/microl.

Measuring the need for medical care in an ethnically diverse population

OBJECTIVE

To examine measures of need for health care and their relationship to utilization of health services in different racial and ethnic groups in California.

DATA SOURCE

Telephone interviews obtained by random-digit dialing and conducted between April 1993 and July 1993 in California, with 7,264 adults (ages 18-64): 601 African Americans, 246 Asians, 917 Latinos interviewed in English; 1,045 Latinos interviewed in Spanish; and 4,437 non-Latino whites.

STUDY DESIGN

A cross-sectional survey was conducted from a stratified, probability telephone sample.

DATA COLLECTION

Interviews collected self-reported indicators of need for health care: self-rated health, activity limitation, major chronic conditions, need for ongoing treatment, bed days, and prescription medication. The outcome was self-reported number of physician visits in the previous three months.

PRINCIPAL FINDINGS

Compared to whites, one or more of the other ethnic groups varied significantly (p < .05) on each of the six need-for-care measures after adjustment for health insurance, age, sex, and income. Latinos interviewed in Spanish reported lower percentages and means on five of the need measures but the highest percentage with fair or poor health (32 percent versus 7 percent in whites). Models regressing each need measure on the number of outpatient visits found significant interactions of ethnic group with need compared to whites. After adjustment for insurance and demographics, the estimated mean number of visits in those with the indicator of need was consistently lower in Latinos interviewed in Spanish, but the differences among the other ethnic groups varied depending on the measure used.

CONCLUSION

No single valid estimate of the relationship between need for health care and outpatient visits was found for any of the six indicators across ethnic groups. Applying need adjustment to the use of health care services without regard for ethnic variability may lead to biased conclusions about utilization.

HIV infection in homosexual and bisexual men 18 to 29 years of age: the San Francisco Young Men's Health Study

OBJECTIVES

Recent studies suggest very high human immunodeficiency virus (HIV) infection rates in some populations of younger homosexual men, but these studies may represent only particularly high-risk populations. The current study obtained population-based data on the HIV epidemic in young homosexual/bisexual men.

METHODS

A household survey of unmarried men 18 through 29 years of age involved a multistage probability sample of addresses in San Francisco. A follow-up interview and HIV test for men who were HIV negative at baseline were completed; the median follow-up was 8.9 months.

RESULTS

Sixty-eight of 380 homosexual/bisexual men (17.9%) tested HIV seropositive. Sixty-three percent of men reported one or more receptive anal intercourse partners in the previous 12 months, and 41% of those men did not use condoms consistently. The HIV seroincidence rate among those seronegative at first study was 2.6% per year.

CONCLUSIONS

HIV infection rates in young homosexual men in San Francisco are lower than those in the early 1980s; however, the rate of infection in these men, most of whom became sexually active after awareness of AIDS had become widespread, threatens to continue the epidemic in the younger generation at a level not far below that of a decade ago.

Relationship of beta 2 microglobulin and CD4 counts to neuropsychological performance in HIV-1-infected intravenous drug users

This study explores the relationship of immune dysfunction to the neuropsychological performance of i.v. drug users (IVDUs) infected with HIV-1. Ninety-seven HIV-positive and 45 HIV-negative former IVDUs on methadone maintenance were evaluated using neuropsychological measures, physical examinations, and measures of immune function, including absolute CD4 counts and beta 2 microglobulin (beta 2-M). There were no significant differences between the HIV-positive and HIV-negative subjects on any single neuropsychological domain. There was, however, a significant group difference on a composite indicator of neuropsychological impairment, with 32% of HIV-positive subjects demonstrating some degree of overall impairment compared with only 13% of HIV-negative subjects. HIV-positive subjects were then stratified according to the Centers for Disease Control (CDC) symptom groupings: group II, asymptomatic, n = 29; group III, lymphadenopathy, n = 30; and group IV A or C-2, symptomatic, non-AIDS, n = 38. There were no significant neuropsychological differences among the three CDC groups. The HIV-positive subjects were also stratified on absolute CD4 counts (< or = 200, 201-400, and > 400) and beta 2-M (> or = 5, 3-5, and < 3). Individuals with greater immune compromise (CD4, < 200, beta 2-M, > or = 5) were more impaired on measures of motor functioning. beta 2-M was found to be a better predictor than CD4 count of impaired neuropsychological performance. Furthermore, individuals with beta 2-M values > or = 5 have more than a threefold increase in the incidence of neuropsychological impairment than those with beta 2-M values < 3.0. These results suggest that beta 2-M may serve as a useful clinical marker for the development of neuropsychological impairment and that the risk of such impairment increases as the immune system weakens.

Plasma prorenin as an early marker of nephropathy in diabetic (IDDM) adolescents

We studied a group of 50 adolescents, average age 16 years, with diagnosed IDDM present for about seven years. Twenty-five had microalbuminuria (MA) averaging 111.0 +/- 34.0 (SEM) micrograms/min albumin excretion rate versus 6.7 +/- 7.4 micrograms/min in the 25 without MA. In other respects, such as sex ratio, age, body mass index, duration of IDDM, hemoglobin A1c, and normotensive systolic, diastolic and mean blood pressures (BP), these subgroups were closely matched. We compared them with a control group of 39 normotensive adolescents, of whom 18 were carefully matched siblings of the IDDM subjects with MA and 21 were similarly matched siblings of the IDDM non-MA subjects. Plasma renin concentration was determined by a direct radioimmunoassay method (Sanofi-Pasteur) and found to be virtually the same in the control and IDDM adolescents as a whole. There was also no real difference between the MA and non-MA subgroups. In contrast, plasma prorenin was significantly higher in the combined IDDM group (197.5 +/- 9.3 vs. control, 134.0 +/- 7.9 pg/ml, P < 0.0001). It was also higher in the MA subgroup than in the non-MA subgroup (226.4 +/- 13.6 vs. 168.5 +/- 10.1 pg/ml, P < 0.001). Interestingly, the 18 control siblings matching the MA subgroup had higher plasma prorenin than the 21 control siblings matching the non-MA subgroup (P < 0.001), suggesting a familial predisposition that precedes detectable diabetes and nephropathy. Our findings confirm and extend reports by other workers that elevated plasma prorenin is associated with incipient nephropathy, manifested by MA. The exclusive renal origin of this prorenin, its role in plasma, and the mechanism responsible for its elevation in IDDM with MA, are yet to be demonstrated, as is the general applicability of these findings to different populations of diabetics, with a higher incidence and severity of complications.

The identification of NP25: a novel protein that is differentially expressed by neuronal subpopulations

A novel gene encoding a 25-kDa neuronal-specific protein, here named 'NP25', has been isolated as a cDNA clone from rat brain. The sequence of the NP25 cDNA reveals a single open reading frame that encodes a primary translation product of 206 amino acids. A search of the protein sequence databank indicates that NP25 is significantly homologous with three recently discovered muscle proteins: SM22 alpha, mp20 and calponin. The gene is specifically and ubiquitously expressed in the rat brain and has conserved sequences among chicken, rat, mouse and human. Rat brain NP25 was identified by Western blot using an antiserum elicited against trpE-NP25 fusion protein. On pH gradient electrophoresis, NP25 was separated into at least two isoforms with similar molecular weights. Immunocytochemistry and in situ hybridization demonstrated that NP25 was differentially expressed by neuronal subpopulations of the rat central nervous system. The highest concentration of NP25 protein was localized in central amygdaloid nuclei and glomeruli in the granule layer of cerebellum. The wide and differential distribution of NP25 in the brain suggests that it may play a particular important role in the function of specific neuronal systems.

Time from HIV seroconversion to oral candidiasis or hairy leukoplakia among homosexual and bisexual men enrolled in three prospective cohorts

OBJECTIVES

We evaluated time from HIV seroconversion to diagnosis of two common oral lesions associated with HIV infection and disease progression.

DESIGN

Oral examinations were performed on homosexual and bisexual men enrolled in prospective cohorts.

SETTING

Homosexual and bisexual men were followed in three epidemiologic cohort studies in San Francisco, California, USA.

PARTICIPANTS

Data were evaluated from 80 men with well-defined dates of HIV seroconversion from 1984 through 1991.

MAIN OUTCOME MEASURES

We determined the cumulative incidence of oral candidiasis and hairy leukoplakia after HIV seroconversion.

RESULTS

Four per cent of men developed oral candidiasis within 1 year after HIV seroconversion, 8% within 2, 15% within 3, 18% within 4, and 26% within 5 years. Nine per cent developed hairy leukoplakia within 1 year, 16% within 2, 25% within 3, 35% within 4, and 42% within 5 years. The median CD4+ count was 391 x 10(6)/l when oral candidiasis was first reported and 468 x 10(6)/l when hairy leukoplakia was first reported.

CONCLUSIONS

Oral candidiasis or hairy leukoplakia appeared in a significant proportion of HIV-infected homosexual and bisexual men. These lesions occurred relatively soon after HIV seroconversion, typically before AIDS. Evaluation of HIV-infected individuals for these lesions has many potential clinical and research benefits, including the possible use of oral lesions as primary end-points in clinical trials.

Immune function and neuropsychological performance in HIV-1-infected homosexual men

This study explores the relationship of immune dysfunction to the neuropsychological performance of individuals infected with HIV-1. Fifty-five HIV-positive homosexual men and 37 negative homosexual controls were evaluated using neuropsychological measures, physical exams, and measures of immune functioning. There were no significant differences favoring HIV-negative subjects over HIV-positive subjects. HIV-positive subjects, in fact, performed slightly better on attention and memory procedures. The HIV-positive subjects were then stratified according to the Centers for Disease Control symptom groupings (Group II, asymptomatic, n = 19; Group III, lymphadenopathy, n = 17; and Group IVA or C-2, symptomatic, non-AIDS, (n = 19). There were no significant neuropsychological differences among the three CDC groups. The HIV-positive subjects were also stratified on two measures of immune functioning: absolute CD4 counts (< 200, 201-400, > 400) and beta 2-microglobulin (beta 2M) (> or = 5.0, 3.0-5.0, < 3.0). Individuals with greater immune compromise, as measured by beta 2M, were more impaired on measures of attention and memory and had greater overall neuropsychological impairment (p < 0.05). Furthermore, 57% of the subjects who were abnormal on beta 2M were also impaired on measures of attention and memory, whereas only 14% of those with normal beta 2M were impaired on these same measures (p < 0.05). These results suggest that HIV-positive asymptomatics without evidence of immune compromise do not appear to be at greater risk of cognitive impairment than HIV-negative controls. However, for those HIV-positive individuals who are immune-compromised (even while asymptomatic), there is increased risk of neuropsychological impairment. These results also suggest that knowledge of serostatus and the use of the CDC classification system alone are insufficient in exploring the development of neuropsychiatric changes in HIV-1 infection.

Relationship of CD4 counts to neurophysiological function in HIV-1--infected homosexual men

OBJECTIVE

To explore the relationship of immune dysfunction to neurophysiological measures of brain-stem conduction time.

DESIGN

Three-year longitudinal prospective cohort study; results of time 1 analyses reported.

SETTING

San Francisco (California) General Hospital, Departments of Psychiatry and Epidemiology.

PATIENTS

Volunteer sample of 55 human immunodeficiency virus (HIV)-positive and 37 HIV-negative homosexual men recruited from a larger cohort of homosexual men followed up since 1983 at San Francisco General Hospital as part of an ongoing study of the natural history and course of HIV type 1 infection.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Auditory brain-stem responses and somatosensory evoked potentials for subjects stratified separately on HIV serostatus, Centers for Disease Control and Prevention symptom groupings, and absolute CD4 counts.

RESULTS

The HIV-positive subjects had an increased wave III-V interpeak latency of the right ear auditory brain-stem response compared with the HIV-negative subjects (t test, P < .05). There were no significant differences among the three Centers for Disease Control and Prevention groupings on any evoked potential measure. When HIV-positive subjects were stratified on a measure of immune functioning, ie, CD4 counts, individuals with greater immune suppression were more impaired on speed of auditory brain-stem conduction time (Mann-Whitney U test, P < .05). Furthermore, 85% of subjects impaired on this evoked potential measure had CD4 counts of less than 0.40 x 10(9)/L (400/microL), whereas only 15% of those impaired on this measure had CD4 counts of greater than 0.40 x 10(9)/L.

CONCLUSIONS

Asymptomatic HIV-positive subjects who do not have evidence of immune suppression do not appear to be at greater risk for neurophysiological impairment than HIV-negative subjects. The HIV-positive individuals who are immune suppressed (even while asymptomatic) appear to have an increased likelihood of central conduction time slowing as measured by evoked potential procedures.

Risk factors for hepatitis C virus seropositivity in heterosexual couples

OBJECTIVES

To determine the risk of heterosexual transmission of hepatitis C virus (HCV) and to identify other risk factors for HCV seropositivity in heterosexual couples.

DESIGN

Retrospective cross-sectional study comparing HCV-seropositive and HCV-seronegative heterosexual men and women.

SETTING

Couples recruited from the community and screened for participation in a study of the heterosexual transmission of human immunodeficiency virus.

PARTICIPANTS

A total of 340 subjects, 170 men and 170 women in sexual partnerships, aged 18 through 61 years.

MAIN OUTCOME MEASURE

Seropositivity for HCV antibodies.

RESULTS

Overall, 31 (18%) of the 170 women and 56 (33%) of the 170 men were positive by a four-antigen HCV immunoblot. Injection drug use and hemophilia were strongly associated with HCV seropositivity. Sixty-four percent of injection drug users were positive (odds ratio [OR], 27.0; 95% confidence interval [CI], 13.4 to 56.1; P < .0001), as were all four hemophiliacs in the study. History of blood transfusion was significantly associated with HCV seropositivity (OR, 2.7; 95% CI, 1.1 to 7.0; P = .02). Positivity for HCV was not associated with measures of sexual behavior within couples or with numbers of other sexual partners, history of sexually transmitted diseases, or human immunodeficiency virus seropositivity. However, two of the 31 women without parenteral risk but with a long-term HCV-positive male partner were HCV seropositive compared with none of 81 women with an HCV-negative male partner (P = .07).

CONCLUSIONS

These results provide little evidence of HCV sexual transmission but are consistent with infrequent sexual transmission. They corroborate the importance of injection drug use and transfusion of blood or blood products in transmitting HCV and underscore the importance of ascertaining parenteral exposures when examining sexual transmission of HCV.

Comparison of risk factors for hepatitis C and hepatitis B virus infection in homosexual men

Serum samples from 735 homosexual or bisexual men were tested for antibodies to hepatitis C virus (HCV) and serologic markers of hepatitis B virus (HBV), and risk factors for each infection were compared. Thirty-four (4.6%) were confirmed HCV-positive compared with 81% positive for one or more HBV serologic marker(s). History of intravenous drug use (IVDU) and blood transfusion were significantly associated with HCV positivity (odds ratio [OR] = 14.3 and 4.4, respectively), but neither was significantly associated with HBV positivity. Sexual behavior was significantly associated with infection with both viruses. When IVDU and blood transfusion were controlled for, HCV infection was marginally associated with > 50 sex partners/year (OR = 2.1), > 25 oral receptive partners (OR = 2.4), and > 25 anal receptive partners (OR = 1.9). HBV infection was more strongly associated with the same variables. HCV infection is uncommon in homosexual men and IVDU is the primary route of transmission, but sexual transmission also occurs, albeit infrequently.

Differences in laboratory values in HIV infection by sex, race, and risk group

OBJECTIVES

To determine differences in CD4+ and CD8+ lymphocyte values, beta 2-microglobulin (beta 2M), and HIV p24 antigenemia by sex and race among HIV-seropositive and HIV-seronegative injecting drug users (IDU), and to compare these values with those in homosexual men of equivalent status.

DESIGN

Baseline values from a cohort of 206 HIV-seropositive and 173 HIV-seronegative IDU were compared with values from a cohort of 288 HIV-seropositive homosexual men and 176 HIV-seronegative controls, who were prospectively followed at 6-month intervals, to examine differences in laboratory values in HIV-infected individuals by sex, race, and risk group.

METHODS

Among HIV-seropositives, we compared white and black IDU only (n = 167), and white male IDU (n = 38) with white homosexual men (n = 256). Laboratory values from the cohort of homosexual men at 24, 36 and 48 months of follow-up were compared with IDU values.

RESULTS

HIV-infected female IDU had significantly higher CD4+ lymphocyte counts (P < 0.03) and percentages of CD4+ lymphocytes (P < 0.004) than male IDU, resulting in higher CD4:CD8 ratios (P < 0.002). White IDU had significantly higher serum beta 2M levels than black IDU (P < 0.02). Black female IDU were much less likely to be HIV p24-antigenemic (1%) than all other groups (P < 0.005). Compared with homosexual men, male IDU had significantly elevated beta 2M levels (0.58 mg/l higher). When controlled for CD4+ lymphocyte values as a surrogate for length of time HIV-infected, beta 2M and HIV p24 antigenemia differences persisted.

CONCLUSIONS

These differences should be considered when HIV p24 antigen, CD4+ lymphocyte counts and beta 2M levels are used as surrogate markers in clinical trials and management of HIV disease.

Activation and function of prorenin: different viewpoints

This Symposium includes 15 presentations and an editorial review dealing with prorenin activation and function. It comes 20 years after prorenin was first reported in various contexts and attracted attention because of its connection with renin--angiotensin, its high concentration relative to renin in the blood, and its presence in extrarenal, as well as renal, tissues. Intriguing changes in plasma prorenin have been reported after treatment with antihypertensive and other drugs, following various physiological stimuli, and in pathophysiological states such as Wilms' tumor, Bartter's syndrome, and diabetic nephropathy. Lately, very high prorenin concentrations have been found in human and animal ocular fluid, ovarian follicular fluid, and in association with angiogenesis and microangiopathy. High circulating prorenin concentrations and fulminant hypertension have been reported in rats harbouring the mouse Ren-2 gene. However, what prorenin does in all these extrarenal fluids, tissues, and conditions is not well understood. Among the reasons for this lack of understanding are the difficulties in measuring prorenin and in establishing good animal models. We have not answered the critical question as to whether prorenin itself is bioactive like a hormone, and if so, what its action(s) might be. Nor have we established the main alternative, i.e., whether the function of prorenin is indirect, through renin--angiotensin, be it in the circulation or in the extrarenal tissues. This Symposium provides only partial methodological advances and answers, but we hope it will stimulate the breakthrough work needed to supply more complete answers.

Activation and measurement of plasma prorenin in the rat

Prorenin determination in rat plasma has been problematic from the outset. Consequently, its existence is questioned by some and its quantity by others, making it difficult for knowledge to advance as to its function relative to the renin system. The present study examines major variables in the determination of rat plasma prorenin and renin, notably different prorenin activation protocols involving blood samples obtained under various conditions from animals under different anesthetics. We found that a trypsin activation step with 5 mg/mL plasma, 60 min at 23 degrees C, followed by a PRA step of 10 min at 37 degrees C, resulted in the highest prorenin estimates, up to approximately 400 ng.mL-1.h-1 in terms of angiotensin I, as compared with published values of 0-190, based on other protocols. These estimates were obtained despite considerable destruction of angiotensinogen (renin substrate) by trypsin. Cryoactivation of prorenin was much less effective than in human plasma but, when followed by trypsin, it facilitated greater activation than with trypsin alone. Comparable fresh and fresh-frozen plasmas had similar prorenin-renin values, but lower values were observed in plasmas that had been repeatedly frozen and thawed. Conscious rats and those anesthetized with Inactin or ether had higher renins and prorenins than those anesthetized with methoxyflurane or halothane. Rats with kidneys in place during blood collection had higher renins (but not prorenins) than those whose kidneys were clamped off, suggesting that last-minute renin release during blood collection had occurred. We conclude that (i) trypsin generates increased renin, or renin-like, activity in plasma, suggesting activation of a precursor; (ii) on this basis, high prorenin levels exist in normal rat plasma; (iii) renin and prorenin levels are variously influenced by different anesthetics and blood handling procedures; (iv) variation in prorenin levels suggests that it is a dynamic (functional?) component of the renin system; (v) prorenin measurements are heavily influenced by methodological variations during the trypsin step or the subsequent PRA step; (vi) using standardized methodology, the rat can serve as a model for investigating the function of prorenin in normotension and hypertension.

Immune activation markers and AIDS prognosis

Four assays for serum levels of cellular products of immune activation were examined as prognostic markers for AIDS in a prospective study of asymptomatic HIV-seropositive homosexual men. Baseline serum values of beta 2-microglobulin (beta 2M), neopterin, soluble CD8 (sCD8), and soluble interleukin-2 receptor (sIL-2R) for 185 men were examined univariately and multivariately as predictors of AIDS during 36 months of follow-up. Thirty-three cases of AIDS (18%) were diagnosed during the follow-up period. All four assays correlated highly with each other (r = 0.48-0.63), and all four were good univariate predictors of AIDS and comparable to CD4 lymphocyte count. beta 2M, neopterin, and sCD8 predicted AIDS independently of both CD4 count and HIV p24 antigen or p24 antibody in multivariate analysis. Within the range of CD4 count 200-499 x 10(6) cells/l, an immune activation marker used in combination with an assay for p24 antigen identifies those at 3-6% risk of AIDS over 36 months (low risk on both assays) and those at 63-86% risk (high risk on both assays). These results can be used to guide physicians and patients making decisions about treating asymptomatic HIV infection with zidovudine in individuals with CD4 lymphocyte count of 200-499 x 10(6) cells/l.

New renin--angiotensin from plasma prorenin?

Within 24 h of binephrectomy in rats, plasma prorenin (activated by trypsin) rose well above normal levels while renin disappeared. This rise in prorenin may be attributed to enhanced secretion by an unidentified extrarenal source and the lack of any renin formation from it suggests that nephrectomy abolishes any systemic "convertase" mechanism that exists for its activation. Within 48 h of adrenalectomy in rats, plasma prorenin levels dropped below normal, while renin rose sharply, suggesting enhanced activation of prorenin to renin, resulting in prorenin depletion, and/or the release of a higher proportion of renin: prorenin by the kidneys. To test for enhanced convertase activity, we crosscirculated adrenalectomized (high convertase) and nephrectomized (low convertase) rats and observed a rapid drop in prorenin with an increase in renin in their shared blood. This was also observed after mixing their bloods in vitro, without crosscirculation, indicating that renal convertase activity was in the bloodstream and not just in the kidneys. Acute nephrectomy of previously adrenalectomized rats lowered renin and raised prorenin within 15 min suggesting a rapid loss of kidney-derived convertase. These results could not be attributed to changes in renin-substrate concentration. The new renin (from activated extrarenal prorenin) was blocked by a monoclonal antibody effective against normal rat plasma renin. It also generated immunoreactive angiotensin I, indicating immunological and biological coidentity with renal renin. The blood of normal control rats did not exhibit convertase activity in vivo or in vitro. These data point to a secretory (endocrine) source of extrarenal prorenin which is stimulated by nephrectomy and to a renal prorenin convertase mechanism which is abolished by nephrectomy and stimulated by adrenalectomy. Thus, in a high renin state, active renin may arise by activation of circulating prorenin (renal and extrarenal) as well as by direct renal release.

Extrarenal production and activation of human plasma prorenin: the evidence after venous occlusion

Venous occlusion of the left arm in consenting men was induced for 10 or 20 min to stimulate local fibrinolytic and other proteases, thereby favouring the conversion of prorenin to renin. Using the two techniques cryoactivation and tryptic activation, we found that plasma active renin increased significantly after such occlusion (10 and 20 min) while prorenin rose more convincingly and progressively from 10 to 20 min. The renin increase can be partially attributed to hemoconcentration, but in vivo production and (or) local activation of prorenin to renin cannot be excluded. The prorenin rise can apparently be attributed to local extrarenal production, and not to hemoconcentration or influx, since it was progressive and neither prorenin nor renin levels were raised at all in blood circulating outside the occluded arm. Prekallikrein and plasminogen levels were elevated in occlusion plasmas, but responsibility of these enzyme systems for any enhanced activation of prorenin was not established. The trypsin inhibitory capacity was also elevated, increasing the requirement of trypsin to achieve optimal activation of prorenin, but not changing the prorenin estimate itself. Thus, prorenin appears to be released extrarenally, within the vasculature of an occluded arm, while in vitro evidence suggests that the mechanisms for its activation were stimulated. The importance of such extrarenal production and activation of prorenin for renin production under other physiological or pathophysiological conditions remains to be determined.

Does angiotensin regulate systemic conversion of prorenin to renin?

Within 12 hours of binephrectomy in rats, plasma prorenin rises about 250% above the pre-operative baseline and remains above-normal for at least 48 hours, indicating an extrarenal source of prorenin. Concurrently, active renin disappears, implying the loss of a renal "convertase" mechanism for prorenin activation. Such "convertase" activity was detected in incubates of renal cortical slices. To test the effect of angiotensin (Ang) on prorenin/"convertase" regulation, we infused Ang I (100 ng/kg/min) intraperitoneally for 24 hours and obtained evidence of "convertase" inhibition, as happened also following Ang II (2uM) addition to incubated cortical slices. Thus, the release and/or activity of "convertase" appears to be regulated by Ang in-vivo and in-vitro, suggesting that Ang controls not only direct renal renin release but also the secretion and/or activity of a renal "convertase" capable of producing additional renin from circulating prorenin pools.

Renin substrate (angiotensinogen) preparations in the determination of prorenin and renin: evidence for extrarenal plasma prorenin and its renal "convertase"

Standard methods for determining prorenin-renin concentrations in plasma (PRC) and other tissues require the addition of exogenous renin substrate (angiotensinogen) to improve the kinetics of the renin reaction. We studied the effects of substrate prepared from normal human plasma fraction Cohn IV-4, or from nephrectomized (2NX) sheep plasma, on PRC of normal and 2NX human plasmas before and after prorenin activation by acid, cold, and trypsin, and compared the results with plasma renin activities (PRA, no added substrate). Plasmas from 2NX men exhibited negligible basal PRA, indicating that very little, if any, renin had been formed from the extrarenal prorenin they contained, and suggesting the lack of an endogenous prorenin activating mechanism, or "convertase," of probable renal origin. Prorenin was demonstrable by tryptic activation, more than by acid or cold, at up to about 30% of normal. Addition of Cohn IV-4 substrate to 2NX plasma unexpectedly produced (i) a basal PRC value higher than in normal plasma, (ii) total renin values after activation by acid, cold, and trypsin that were much closer to normal values than reflected by PRA methodology, without a commensurate increase (if anything a decrease) in prorenin as a percentage of total renin estimated by all activation methods, and (iii) substantial equalization of activation effects such that trypsin was no longer more effective than acid and cold (and this was also noted with normal plasma). The skewing effect of adding Cohn IV-4 substrate on the PRC of 2NX plasma was much greater than in normal plasma, even though 2NX plasma already had an above normal level of endogenous substrate and should have been influenced less. Enhancement of PRC was very pronounced even when Cohn IV-4 was added to make up only 9% of total (endogenous + exogenous) substrate in the incubation system, suggesting that it was not the added substrate but a renin-generating contaminant that inflated the PRC. Such inflation could be blocked by adding protease inhibitors, suggesting that the responsible protease(s) acted as a prorenin "convertase" that generated new renin from renal and (or) extrarenal prorenin contributed by the added substrate, as well as by the plasma being assayed. One component of convertase could be kallikrein, which was identified by chromogenic assay, the importance of which relative to total convertase activity is unknown.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulated systemic activation of rat plasma prorenin

Nephrectomized rats have above-normal plasma prorenin levels, presumably of extra-renal origin, but essentially no renin, suggesting a lack of "convertase" for prorenin activation. Adrenalectomized rats have low plasma prorenin levels accompanied by high renin activity, suggesting enhanced prorenin activation by the action of a stimulated "convertase" mechanism. Cross-circulation between adrenalectomized and nephrectomized rats for 15 or 30 minutes, dramatically lowered prorenin and raised renin levels in both types of rats, suggesting extensive activation of prorenin to renin. Similarly, in vitro mixing of these bloods (without cross-circulation) raised renin activity over five times the expected calculated level, while prorenin essentially disappeared. In both cases, prorenin from nephrectomized rat plasma apparently was activated to renin by the enhanced action of "convertase" in the adrenalectomized rat plasma. This newly generated renin activity was, like normal plasma renin, almost completely inhibited by a monoclonal antibody against hog renin and generated an immunoreactive angiotensin I. In contrast, cross-circulation or in vitro mixing of blood from normal control and nephrectomized rats produced little detectable activation of prorenin and only modest increments of renin, suggesting relative inactivity of the "convertase" mechanism in normal plasma. Our data suggest that activation of plasma prorenin is a significant regulated pathway for renin production, as it is greatly stimulated after adrenalectomy and deficient after nephrectomy, thereby implicating the kidney as an important contributor to the "convertase" mechanism operating within the circulation.

Can total prorenin in human plasma be determined by current activation methods?

A proper evaluation of the physiological significance of plasma prorenin depends on its accurate determination. However, current activation methods do not necessarily measure total prorenin, or a known proportion of it, even when carried out to apparent completion. Thus, extending cold activation of human plasma at -4 degrees C generally revealed progressive increments of prorenin, mainly during the first 15 days, but the total and the time required to achieve it varied considerably among individuals. Similarly, the titration curves of individual plasmas varied with increments of added trypsin and achieved totals that were not necessarily greater than those obtained by cold activation. This indicates the inappropriateness of attributing greater effectiveness to one method over the other. When the two methods were paired in sequence, a synergism was apparent in that prorenin estimates increased consistently; in one case more than 10-fold. Thus, total prorenin by any single method generally fell short of the total achieved by double methods. However, this too may still not represent the unknown true total prorenin. The sequence of activation steps was important, providing clues as to the mechanism of the observed synergism. Trypsin-before-cold activation proved to be more effective than trypsin-after-cold activation, with no further advantage being gained from triple treatments involving cold before and after trypsin, or trypsin before and after cold. The inferiority of trypsin-after-cold activation was apparently due to sensitization of the plasma to the destructive effects of trypsin, shifting its titration curve to the left.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for beta-adrenergic regulation of renal and extrarenal plasma prorenin and renin in dogs

Beta blockade with propranolol for 7 days in healthy normotensive dogs produced a sustained 20-25% drop in heart rate, but only a transient suppression of blood pressure. Plasma renin activity and prorenin were also suppressed transiently, suggesting that both are under beta-receptor regulation. Bilateral nephrectomy (2NX) was followed by rapid clearance of renin from the circulation, at a rate that was minimally influenced by beta blockade. In contrast, the plasma prorenin level rose markedly to a peak within an hour after surgery, leveled off during the next 24 hr, dropped almost toward the pre-2NX baseline by 48 hr, but proceeded to rise again between 48 and 120 hr. Propranolol administration before and during the 2NX period reduced the detectable prorenin, suggesting that its extrarenal source is under beta-adrenergic regulation. The rapid increment of prorenin after 2NX suggests that extrarenal prorenin may have constituted part of the total plasma prorenin before 2NX, and/or had developed sufficiently quickly afterwards to replace and exceed the disappearing renal prorenin. Any fresh increment beyond 48 hr could presumably have been only extrarenal. These observations suggest the existence of a rich beta-regulated extrarenal source of prorenin capable of rapidly supplying the plasma. However, no renin-angiotesin was apparently produced from this prorenin in the nephrectomized state, implying the lack of renal "convertase," without which the prorenin convertase mechanism as a whole was rendered ineffective. The source of the extrarenal prorenin and the identity of the renal convertase remain to be established.