Michael S. Ascher

Direct HIV cytopathicity cannot account for CD4 decline in AIDS in the presence of homeostasis: a worst-case dynamic analysis

The central paradox of HIV pathogenesis is that the viral burden, either free or cellular, seems too low to deplete the CD4 population by direct killing. Until recently, little data could be used to compare direct and indirect pathogenic theories critically. Clinical trials with potent new antiviral agents have measured important kinetic parameters of HIV infection, including viral and infected cell half-lives. This has led to the construction of explicit models of direct killing. Using a worst-case dynamic analysis, we show that such cytopathic models are untenable. Rates of infected cell removal are orders of magnitude too low to suppress steady state CD4 counts significantly in the face of lymphocyte replenishment, especially in early infection. Furthermore, the direct cytopathic models, as proposed, predict an extremely variable disease course across the broad range of observed viral burdens (five orders of magnitude), which is inconsistent with the relatively small differences in disease progression observed between patients. In contrast, immunologic theories of pathogenesis, such as homeostatic dysregulation based on immune activation, do not suffer from these difficulties and are more consistent with the natural history of HIV infection.

Expression of CD69 after in vitro stimulation: a rapid method for quantitating impaired lymphocyte responses in HIV-infected individuals.

A flow cytometric assay based on expression of the activation antigen CD69 was developed to analyze immunological responses of T cells from human immunodeficiency virus (HIV)-infected (HIV+) or HIV-seronegative (HIV-) donors after in vitro simulation by antigens and polyclonal activators. The levels of CD69 on freshly-isolated or unstimulated, cultured CD3+, CD4+, or CD8+ peripheral blood lymphocyte (PBL) subsets were low and did not differ greatly between HIV+ and HIV- donors. The frequencies of CD3+, CD4+, and CD8+ lymphocytes from HIV+ donors that expressed CD69 after culture with antigenic or mitogenic stimuli were significantly lower than in HIV- donors. Comparison of CD69 expression with [3H]thymidine incorporation revealed that both assays could detect lymphocyte responses to antigenic or mitogenic stimuli. The CD3+ PBL from HIV+ or HIV- donors did not show increased CD69 expression after culture with soluble or cross-linked recombinant envelope glycoprotein, gp120. The gp120, however, significantly inhibited CD69 expression in phytohemagglutinin-stimulated T cells in vitro and may also affect T-cell activation in vivo. These studies demonstrate the usefulness of this CD69 expression assay for the rapid assessment of defects in immune responses of phenotypically defined lymphocyte subsets in HIV+ patients and for testing the effects of agents that modulate immune activation.

Dominant glycoprotein epitope of four corners hantavirus is conserved across a wide geographical area

A newly identified hantavirus, tentatively called Four Corners virus (FCV), was found to be the aetiological agent of a 1993 outbreak of hantavirus pulmonary syndrome (HPS) in the southwestern United States. Immunodominant epitopes of 43 and 31 amino acids were identified in the nucleocapsid protein and G1 glycoprotein, respectively. The G1 genes of different hantaviruses are highly divergent, suggesting that geographically diverse FCVs might fail to cross-react owing to antigenic drift. We now show that the immunodominant epitope of G1 is conserved among 18 FCVs from a broad geographical area, despite extensive nucleotide sequence heterogeneity. Antibodies from all 45 HPS patients, separated by more than 3000 km were shown to be reactive with the dominant G1 epitope. Evidence for limited cross-reactivity between the G1 antigen of a novel hantavirus of the cotton rat and that of FCV is presented.

The lack of association of Marijuana and other recreational drugs with progression to AIDS in the San Francisco men's health study☆

We evaluated the associations of specific recreational drugs and alcohol with laboratory predictors of AIDS at entry into the San Francisco Mens Health Study (SFMHS) in 1984 and with the development of the acquired immunodeficiency syndrome (AIDS) during 6 years of follow-up. Marijuana use was associated with a decreased rate of progression to AIDS in the univariate analysis (RR = 0.7; P = 0.01). Marijuana use was more common among individuals with elevated HIV viral core protein antibody (p24Ab) titer (> 1:16) at baseline (P = 0.03); this finding suggests that marijuana users were healthier at baseline. When the data were adjusted for p24 Ab and other laboratory parameters, no association with progression to AIDS was observed for marijuana, suggesting that the observed univariate result was due to a difference in HIV-related disease at the time of enrollment. No statistically significant associations were observed for nitrites, methylene dioxyamphetamines, ethyl chloride, downers, cocaine, stimulants, narcotics, or psychedelic drugs. These data suggest no substantial association between use of these drugs and the development of AIDS among HIV-infected men.

Aids as Immune System Activation

Since 1987, when we first formulated the hypothesis that AIDS and HIV disease are the result of inappropriate immune system activation triggered by viral gp 120 signalling at CD4 [1-3], the concept has been supported by several developments. First is a better understanding of the natural history of HIV disease. Second is the elucidation of the role of CD4 in T cell activation. Third is the appreciation of the prominent role of programmed cell death or apoptosis in the normal dynamic equilibrium of the immune system. Last is the failure of antiviral strategies to affect the clinical course of disease in infected individuals.

The HIV-1 seroprevalence rate of injured patients admitted through California emergency departments

STUDY OBJECTIVES To measure the HIV seroprevalence of injured emergency department patients in a number of California hospitals and to examine the relationship between ED seroprevalence and local AIDS incidence. DESIGN Prospective blinded testing for HIV-1 antibody was performed on routinely collected blood samples. SETTING Ten California hospitals; group 1 included three hospitals from counties of high AIDS incidence (more than 40 cases per 100,000 population), group 2 included three hospitals from counties of intermediate AIDS incidence (20 to 40 cases per 100,000 population); and group 3 included four hospitals from counties of low AIDS incidence (less than 20 cases per 100,000 population). TYPE OF PARTICIPANTS Eligible patients were all adult trauma victims admitted to a participating hospital through the ED during a consecutive three-month period occurring between June and November 1989. MEASUREMENTS HIV-1 antibody testing was done using enzyme immunoassay confirmed by immunofluorescence assay. Equivocal results were confirmed by Western blot. Mann-Whitney U test, chi 2 test, and multiple logistic regression were used where appropriate. RESULTS There were 2,264 patients with adequate blood samples for serologic testing. The seroprevalence rates for hospitals in groups 1, 2, and 3 were significantly different (chi 2 = 8.44, P = .02): Group 1, 2.5% (19 of 756: 95% confidence interval [CI], 1.5% to 3.9%); group 2, 0.9% (10 of 1,078; CI, 0.5% to 1.7%); and group 3, 0.5% (two of 430; CI, 0.06% to 1.7%). CONCLUSION This study suggests that local AIDS incidence rates do not necessarily predict the seroprevalence rates of injured patients who are admitted through local EDs.

A comparison of HIV-1, HBV, and HTLV-I/II seroprevalence rates of injured patients admitted through California emergency departments

STUDY OBJECTIVE To determine the seroprevalence rates of hepatitis B virus (HBV) and human T-lymphotropic virus (HTLV-I/II) and to compare these rates with the HIV-1 seroprevalence rate in a sample of injured patients admitted through ten California emergency departments. DESIGN Prospective blinded testing for serologic markers for HBV, HTLV-I/II, and HIV-1 on routinely collected blood samples. SETTING Ten California hospitals were chosen to reflect geographic and demographic diversity. TYPE OF PARTICIPANTS All injured adult patients who were admitted to a participating hospital through the ED during consecutive three-month periods from June through November 1989. MEASUREMENTS Serum samples were tested for HIV-1 antibody, HTLV-I/II antibody, and hepatitis B surface antigen (HBsAg) using standard methods. Mann-Whitney U tests, chi 2 tests for independence, sign tests, chi 2 tests for goodness of fit, and logistic regression were used as appropriate. RESULTS Seroprevalence rates were as follows: HBV, 2.6% (57 of 2,209); HTLV-I/II, 2.0% (46 of 2,262); and HIV-1, 1.4% (31 of 2,264). CONCLUSION The seroprevalence rate of HBV was slightly higher than that of HIV-1 in this sample of injured patients. Mortality estimates suggest, however, that HBV and HIV-1 pose roughly similar risks to emergency personnel, although the risk of HBV infection can be markedly reduced by vaccination. The data from this and other studies suggest that the ED incidence of HTLV-I/II in United States is low. The relative health risks to emergency personnel from HTLV-I/II appear to be minimal at this time.

Comparison of porcine and semisynthetic human insulins using euglycemic clamp-derived glucose-insulin dose-response curves in insulin-dependent diabetes

In order to compare the biologic effectiveness of porcine and semisynthetic human insulins, a euglycemic clamp method was used in eight insulin-dependent diabetic subjects. Each subject was tested for each insulin on separate days. In order to derive glucose-insulin dose-response curves for both insulins, sequential but constant infusion rates of 0.2, 0.5, 1.0, and 2.0 mU/kg/min were performed. Plasma glucose levels attained during the euglycemic clamp were 96 +/- 3 mg/dL. At each insulin infusion rate, the steady-state glucose infusion rate required to maintain euglycemia was measured. At each increment of insulin infused, steady-state glucose infusion rates for porcine insulin were 1.12 +/- 0.22, 1.90 +/- 0.59, 4.28 +/- 0.61, and 9.37 +/- 0.66 mg/kg/min compared with 1.27 +/- 0.42, 2.38 +/- 0.20, 4.25 +/- 0.43, and 8.87 +/- 0.67 mg/kg/min for semisynthetic human insulin. By ANOVA, no significant difference was noted between the two insulins. Because insulin infusion rates may not result in predictable circulating free insulin levels in subjects who have circulating insulin antibodies, free insulin levels were determined. When steady-state glucose infusion rates were compared with free insulin levels achieved at the four insulin infusion rates, dose-response curves for both porcine and semisynthetic human insulins were virtually identical. These data suggest that semisynthetic human insulin has equivalent biologic effects on overall glucose metabolism compared with porcine insulin in insulin-dependent diabetes.

Transfer factor in vitro: Nonspecificity of components that enhance lymphocyte proliferation to antigen

Abstract Dialysates of human leukocyte extracts (DLE) containing transfer factor have been shown in man to transfer cutaneous delayed-type hypersensitivity and in vitro to enhance lymphocyte proliferation to specific antigens. Reciprocal multifactorial experiments reported herein indicate that the in vitro effect does not require DLE donor sensitivity to the antigen used to stimulate the recipient lymphocytes. Active material can be derived from diverse tissue culture sources such as lung fibroblasts, baby hamster kidney cells, and mouse L-cells. DLE can produce an effect in a 7-day culture when added as late as the third day suggesting an effect on proliferation rather than on antigen recognition and transformation. The implications of these in vitro effects on possible mechanisms of action of DLE in vivo are considered.

Occupational Health Guidelines for Control of Q Fever in Sheep Research

Outbreaks of Q fever in the United States occur primarily in occupational settings with sheep, goat, and cattle exposure, including research facilities that conduct experimental research on sheep.14 At the University of California, San Francisco (UCSF), an outbreak occurred in 1979 which resulted in 19 confirmed cases (one fatality) and more than 68 presumptive cases among researchers and employees,s due to exposure to Coxiella burnetii during research on pregnant ewes. In response to that outbreak, the California Occupational Health and Safety Administration (CalOSHA) subsequently issued a Special Order to UCSF to initiate a medical surveillance program and construct a sheep containment facility.6 This Special Order applies to UCSF only; other facilities with similar risk, even in the same community, are not affected by it. Existing published guidelines for reducing the risk of Q fever in research facilities have emphasized the use of control technologies and the use of periodic skin and serological testing to assess the immune status of at-risk The National Institutes of Health have issued guidelines for a mandatory occupational health program both for direct employees of laboratory animal facilities and for research personnel who have substantial animal contact.1° Physical examinations, medical and work history, education, preexposure immunization, and storage of preemployment and postemployment serum samples are recommended. At UCSF, the CalOSHA Special Order mandated the provision of preemployment screening (including an opinion regarding the presence of concurrent medical conditions such as valvular heart disease), annual medical examinations (including clearance to wear respiratory protection), and periodic serological testing. The possibility of vaccine use was recommended (but not ordered), and skin testing was not discussed. Subsequent to the 1979 outbreak, UCSF instituted a voluntary medical surveillance program for employees with exposure to C . burnetii, including preemployment and yearly serological testing. However, recent evidence regarding the use of skin and serological testing has led to a revision of the occupational health program for employees with exposure to C . burnetii during sheep research. 11-14 These new guidelines represent efforts by UCSF to develop a program to monitor the immune status of at-risk personnel, as well as to detect new cases which occur