The safety and efficacy of indinavir and ritonavir (400/400 mg BID) in HIV-1-infected individuals from an inner-city minority population: a pilot study

We evaluated the safety and efficacy of indinavir 400 mg and ritonavir 400 mg twice daily (RIT/IND 400/400) in HIV-1-infected individuals, using an open label, proof of concept study. All patients received indinavir 400 mg and ritonavir 400 mg twice daily. Patients were followed up to 48 weeks. Nineteen subjects were enrolled, 11 (58%) men and eight (42%) women. The majority were American Black (nine; 47%) or Haitian (eight; 42%). The median baseline plasma HIV-1 viral load (VL) was 5.13 log10 copies/mL and the median CD4 cell count was 112 cells/mm3. The proportion of compliant patients with VL <400 copies/mL at week 24 was 60% compared with 0% for non-compliant patients ( P=0.011 [intent-to-treat] or P=0.085 [on-treatment]). VL at week 4 predicted week 24 VL response. Compliant patients had a median average CD4 cell count increase of 83.2 cells/mm3 compared with 42.0 cells/mm3 for non-compliant patients (P=0.010). The median average changes in triglycerides and cholesterol were significantly higher in compliant patients.

This is a potent, safe combination for the treatment of HIV-1. VL at week 4 is predictive of viral outcome at week 24. Fasting serum cholesterol and triglycerides were significantly elevated during the study.

Influence of 4- and 6-color flow cytometers and acquisition/analysis softwares on the determination of lymphocyte subsets in HIV infection

BACKGROUND AND OBJECTIVES

Lymphocyte immunophenotyping provides valuable information for the diagnosis and monitoring of patients with cellular immunodeficiencies, such as HIV/AIDS. In this study, we have assessed the influence of 4-color and 6-color flow cytometers, and respective analytical softwares on the enumeration of lymphocytes in HIV infected individuals.

METHODS

The expression of various cell surface markers on lymphocytes was measured from the EDTA blood of 66 HIV infected patients on the FACSCalibur (4-color) and FACSCanto (6-color) flow cytometers. Percentage of lymphocytes expressing a particular cell surface marker was analyzed on FACSCalibur using the Cell Quest Pro software (v 5.2), while the analysis on FACSCanto was done using FACSCanto (v 1.0.3) and FACSDiva (v 4.1) softwares respectively.

RESULTS

The data shows significantly higher mean CD3 T-cell counts on FACSCalibur, Cell Quest Pro (1,864 +/- 1,044 cells/microl) as compared to FACSCanto (1,840 +/- 1,040 cells/microl) (P < 0.05). The CD4 T-cell counts were also higher on FACSCalibur, Cell Quest Pro (885 +/- 770 cells/microl), and FACSDiva (892 +/- 773 cells/microl) versus FACSCanto (867 +/- 767 cells/microl) (P < 0.05). FACSCalibur, Cell Quest Pro, and FACSDiva showed similar values except for CD8 T-lymphocytes where FACSDiva had significantly lower values (P < 0.05). The B-cell counts were unaffected when either of the instruments or softwares were used, while the natural killer (NK) cells (CD16 + 56 positive cells) showed similar trend like CD3 and CD4 counts with significant differences in the mean cell counts between FACSCalibur, Cell Quest Pro (240 +/- 165 cells/microl), and FACSDiva (238 +/- 163 cells/microl) versus FACSCanto with higher NK cell counts (260 +/- 176 cells/microl).

CONCLUSIONS

The enumeration of lymphocyte subsets was comparable between FACSCalibur, Cell Quest Pro, and FACSDiva, based analysis and it was significantly different than FACSCanto software based analysis. Our observations suggest that FACSDiva software should be preferred over the FACSCanto software for immunophenotyping on FACSCanto flow cytometer and the laboratories should report the instrument and software used for the specimen analysis while reporting immunophenotyping results.

Biochip array-based analysis of plasma cytokines in HIV patients with immunological and virological discordance

Assessment of cytokines in body fluids or cells provides important information in understanding the disease process and designing treatment strategies. Recent introduction of antibody-based protein arrays have provided investigators simultaneous and specific detection of multiple analytes in a single sample using minimum volumes. In this study, we used a biochip array system capable of measuring 12 cytokines and growth factors (IL-2, IL-4, IL-6, IL-8, IL-10, IL-1alpha, IL-1beta, IFN-gamma, TNF-alpha, monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF)) in HIV patients with immunological and virological discordance (discordant) to find out differences if any, in their plasma cytokine profiles when compared with concordant HIV-infected individuals. A sandwich chemiluminescent assay was performed with plasma specimens of 110 HIV patients (55 discordant, 55 concordant) and 22 normal healthy individuals followed by enzyme-linked immunosorbent assay (ELISA) to the confirm levels of cytokines and growth factors that showed significant differences in the two groups. The discordant HIV patients showed significantly higher levels of plasma VEGF (P = 0.001) and EGF (P = 0.034) levels when compared with concordant patients. Overall, the patients showed significantly higher levels of TNF-alpha, MCP-1 and VEGF when compared with the normal healthy controls (P < 0.05). ELISA for VEGF (P < 0.001) and EGF (P = 0.004) confirmed the comparison obtained with biochip array, between the discordant and concordant patients. The results of cytokine quantitation by biochip array and ELISA confirmed that this technology is not only comparable but also has a good potential in the future applications involving measurement of multiple cytokines with limiting specimens.

The impact of improved self-efficacy on HIV viral load and distress in culturally diverse women living with AIDS: the SMART/EST Women's Project

The purpose of the present study was to determine whether changes in self-efficacy over time would be related to changes in disease progression markers (CD4, viral load) in a sample of women with AIDS. A self-efficacy measure was developed and two sub-scales emerged via factor analysis of 391 HIV-positive women: AIDS Self-efficacy and Cognitive Behavioral Skills Self-efficacy. Subsequently, the sub-scales and an additional adherence self-efficacy item were given to 56 HIV-positive women who were measured at two time points three months apart. Half of these women were randomly assigned to a CB intervention and half to a low intensity comparison condition. Increases in AIDS Self-efficacy over the three-month period were significantly related to increases in CD4 and decreases in viral load. Similarly, increases in Cognitive Behavioral Skills Self-efficacy were significantly related to decreases in distress over time. Findings were maintained within the intervention group alone. Interestingly, increases in cognitive behavioral skills self-efficacy and increases in the self-efficacy adherence item were also significantly related to decreases in viral load. Implications of the findings and suggestions for future research are discussed.

Aging and neuro-AIDS conditions and the changing spectrum of HIV-1-associated morbidity and mortality

Older individuals (>50 years of age) now comprise over 11% of patients with AIDS in the United States. This percentage is expected to continue to grow, due both to the improved longevity of patients prescribed highly active antiretroviral therapy (HAART) and to new infections among older individuals. This review focuses on the neuropsychiatric and neurological conditions that are most likely to be affected by advancing age-HIV-1-associated cognitive-motor disorder, peripheral neuropathy, progressive multifocal leukoencephalopathy, primary CNS lymphoma, and risk for cerebrovascular accident. Age associations with incidence of these disorders and with treatment foci are specified. Implications for future changes in management are discussed.

A bereavement support group intervention affects plasma burden of human immunodeficiency virus type 1. Report of a randomized controlled trial

OBJECTIVES

This study investigates the potential impact of a bereavement support group on plasma viral load.

METHODS

A randomly selected subsample of human immunodeficiency virus type 1 (HIV-1)-positive homosexual men participating in a controlled clinical trial of a bereavement support group intervention was studied. The intervention consisted of one 90-minute group session per week for 10 weeks. The plasma HIV-1 RNA copy number was measured at baseline and after intervention (10 weeks) by the Roche AMPLICOR assay.

RESULTS

There was a significant effect of the intervention on the change on the plasma HIV-1 RNA copy number (limited control model, beta = -0.49, p = 0.02; extended control model, beta = -0.37, p = 0.01), independent of antiretroviral therapies; prophylactic therapies against potentially lethal HIV-1 associated conditions; CD4 cell count; viral load; and Centers for Disease Control and Prevention clinical disease stage at baseline.

CONCLUSIONS

Bereavement support group interventions may prove to be not only a primary therapy for psychologic distress after bereavement but also an adjunctive therapy for sustained control of plasma viral load in conjunction with highly active antiretroviral therapy in this population.

Need for an external proficiency testing program for cytokines, chemokines, and plasma markers of immune activation

An external evaluation program for measuring the performance of laboratories testing for cytokines and immune activation markers in biological fluids was developed. Cytokines, chemokines, soluble cytokine receptors, and other soluble markers of immune activation (CSM) were measured in plasma from a healthy human immunodeficiency virus (HIV)-seronegative reference population and from HIV-seropositive individuals as well as in supernatant fluids from in vitro-stimulated human immune cells. The 14 components measured were tumor necrosis factor (TNF) alpha, gamma interferon, interleukin-1 (IL-1), IL-2, IL-4, IL-6, IL-10, Rantes, MIP-Ia, MIP-Ibeta, soluble TNF receptor II, soluble IL-2 receptor alpha, beta(2)-microglobulin, and neopterin. Twelve laboratories associated with the Adult and Pediatric AIDS Clinical Trial Groups participated in the study. The performance features that were evaluated included intralaboratory variability, interlaboratory variability, comparison of reagent sources, and ability to detect CSM in the plasma of normal subjects as well as the changes occurring in disease. The principal findings were as follows: (i) on initial testing, i.e., before participating in the program, laboratories frequently differed markedly in their analytic results; (ii) the quality of testing of a CSM in individual participating laboratories could be assessed; (iii) most commercial kits allowed distinction between normal and abnormal plasma CSM levels and between supernatants of stimulated and unstimulated cells; (iv) different sources of reagents and reference standards frequently provided different absolute values; (v) inexperienced laboratories can benefit from participating in the program; (vi) laboratory performance improved during active participation in the program; and (vii) comparability between analyses conducted at different sites can be ensured by an external proficiency testing program.

Mortality risk in selenium-deficient HIV-positive children

OBJECTIVE

To determine the independent contribution of specific nutritional factors on disease progression and survival in HIV-1-infected children.

POPULATION

HIV-infected children (N = 24), who were perinatally exposed to the virus and symptomatic, were recruited between October and December of 1990 from the Jackson Memorial Pediatric Immunology Clinic, Miami, Florida, and observed for 5 years.

METHODS

Immune status was measured by CD4 cell count; nutritional status was determined using serum albumin and plasma trace elements including iron, zinc, and selenium. Cox proportional hazards regression models were used to evaluate the relationship of these parameters to survival. Use of antiretroviral treatment was considered in the statistical model, and age at death was considered a parameter of disease progression.

RESULTS

Over the course of the study, 12 children died of HIV-related causes. The final Cox multivariate analysis indicated that, of the variables evaluated, only CD4 cell count below 200 (risk ratio [RR] = 7.05; 95% confidence interval [CI], 1.87-26.5); p = .004], and low levels of plasma selenium (RR = 5.96; 95% CI, 1.32-26.81; p = .02) were significantly and independently related to mortality. Among the children who died, those with low selenium levels (< or =85 microg/L), died at a younger age, suggesting more rapid disease progression.

CONCLUSIONS

In pediatric HIV-infection, low plasma level of selenium is an independent predictor of mortality, and appears to be associated with faster disease progression.

Stressful events, pessimism, natural killer cell cytotoxicity, and cytotoxic/suppressor T cells in HIV+ black women at risk for cervical cancer

OBJECTIVE

This study examines whether stressful negative life events and pessimism were associated with lower natural killer cell cytotoxicity (NKCC) and T cytotoxic/suppressor cell (CD8+CD3+) percentage in black women co-infected with human immunodeficiency virus Type 1 (HIV-1) and human papillomavirus (HPV), a viral initiator of cervical cancer.

METHOD

Psychosocial interviews, immunological evaluations, and cervical swabs for HPV detection and subtyping were conducted on 36 HIV+ African-American, Haitian, and Caribbean women.

RESULTS

Greater pessimism was related to lower NKCC and cytotoxic/suppressor cells after controlling for presence/absence of HPV Types 16 or 18, behavioral/lifestyle factors, and subjective impact of negative life events.

CONCLUSIONS

A pessimistic attitude may be associated with immune decrements, and possibly poorer control over HPV infection and increased risk for future promotion of cervical dysplasia to invasive cervical cancer in HIV+ minority women co-infected with HPV.

A bereavement support group intervention is longitudinally associated with salutary effects on the CD4 cell count and number of physician visits

A randomized, controlled, clinical trial was conducted to examine the impact of a semistructured, 10-week, once weekly, 90-min/session bereavement support group intervention on immunological, neuroendocrine, and clinical health status in human immunodeficiency virus type 1-seropositive (HIV-1+) and HIV-1-seronegative (HIV-1-) homosexual men, compared to a standard of care control condition. A total of 119 homosexual men (74 HIV-1+ and 45 HIV-1-) were assessed at baseline, 10 weeks, and 6 months follow-up. At the 6-month follow-up assessment, the intervention groups exhibited significant beneficial effects compared to controls on changes in CD4 cell, total T-lymphocyte, and total lymphocyte counts, when baseline levels, antiretroviral medication use, CDC stage of disease, and other potentially confounding factors were accounted for. There was no statistically significant effect on the CD4/CD8 ratio or on the CD8 cell count. The effect on CD4 cell count was associated with group attendance and with changes in plasma cortisol level. Plasma cortisol levels decreased significantly among intervention subjects, compared to controls. A significantly reduced number of health care visits over the 6-month follow-up period among the intervention subjects supported the clinical relevance of the immunological changes observed for both HIV-1+ and HIV-1- individuals. These results indicate that behavioral interventions may have salutary immunological and clinical health effects following bereavement among HIV-1-infected individuals. The effect in HIV-1- individuals suggests that this bereavement support group intervention might have similar salutary effects in the general population. Potential effects of such interventions on clinical HIV disease progression are of interest and should be studied.

Subtle neuropsychological impairment and minor cognitive-motor disorder in HIV-1 infection. Neuroradiological, neurophysiological, neuroimmunological, and virological correlates

HIV-1 infection of brain may be associated with multiple treatment targets, only the most severe of which is represented by HAD. Focusing on earlier treatment targets such as MCMD and cognitive-motor impairment in the absence of any clinical disorder (as well as neuroprotection) may prove to be of greater clinical utility in the treatment and prevention of such impairment than a focus on later-stage cognitive-motor disease, when neuronal cell death is already extensive. This may be especially important now that improvements using the protease inhibitors in triple-drug combination regimens have reduced plasma viral load to unmeasurable levels, while these drugs do not penetrate the CSF well. Currently, peripheral blood markers do not appear to be highly sensitive for central nervous system impairment, and specific CSF laboratory markers have some limited value at present-while requiring a lumbar puncture to obtain. Hence, a role for noninvasive techniques using neuroimaging exists in the clinical management of HIV-1-infected patients. To date, structural imaging techniques have proven limited in value for HIV-1-specific impairment. Several functional techniques (PET, SPECT, and MR spectroscopy) have now provided promising results for the purposes of identifying clinically significant dysfunction, relating such dysfunction to clinical neuropsychiatric symptom status, and for treatment response monitoring. Further studies are needed to examine the extent to which such imaging modalities not only parallel clinically relevant aspects of HIV-1 disease progression, but also match specific types of neuropsychologic performance deficits with potential significance for neuroanatomical localization. It is particularly important to include neurophysiological, neuroimmunological, and virological measures in studies that examine clinical neuropsychiatric status with neuroimaging techniques. In addition, the inclusion of neuropathology data, where possible, is important because demonstration of HIV-1 encephalitis cannot be equated with clinical disorder and because specific HIV-1-associated pathological changes have not yet been proven to be assessed well with neuroimaging techniques (e.g., the extent of microglial cell and macrophage activation). Also, treatment response studies are needed in conjunction with primary antiretroviral therapy regimens specifically aimed at central nervous system penetration (e.g., GW1592, GW141, and nevirapine). The results of such work will provide the data required to determine whether these promising functional neuroimaging techniques will aid in meeting the expected, imminent increase in clinical burden of this frequent complication of HIV-1 infection.

Longitudinal induced IL-2 mRNA monitoring in renal transplant patients immunosuppressed with cyclosporine and in unmodified canine renal transplant rejection

Immune monitoring of transplant patients to define optimal immunosuppression continues to be important, as rejection occurs despite adjustment of dosaging of CsA or even FK506 to achieve "therapeutic-range" blood levels. Because CsA is known to inhibit upregulation of IL-2 mRNA transcription, we prospectively sequentially measured (induced) IL-2 mRNA in PHA-stimulated PBMC cultures from transplant recipients of kidneys from living-related donors (n = 15) using a quantitative PCR assay, with a potential 24-hour turnaround time, to define immunologic events in real time. Reproducible individual patient sensitivity or refractoriness to CsA was determined pretransplant, by adding a range of CsA concentrations to the PBMC cultures and constructing induced IL-2 mRNA regression inhibition curves. However, this was not predictive of rejection episodes, but did correlate well with individual differences in IL-2 mRNA levels posttransplant, despite similar maintenance trough blood concentrations of CsA between patients. In this prospective study, seven patients experienced rejection episodes despite therapeutic CsA trough levels. Three of these, plus one not receiving CsA therapy, who happened to be prospectively tested at the time that rejection was clinically diagnosed, had a decrease in induced IL-2 mRNA before treatment was instituted. As a correlation to this observation in patients, induced IL-2 mRNA levels in unmodified rejection were sequentially measured in PBMC cultures in autologous vs allogeneic canine renal transplants and IL-2, IL-10, TNF-alpha, and IFN-gamma mRNA were also measured in kidney biopsies. Sequential PHA lymphoproliferation assays of [3H] thymidine incorporation on patient and dog PBMC cultures were also performed. Similar to the observations in patients, unmodified rejection in the canine renal allograft model also was accompanied by a decline of PHA-induced IL-2 mRNA in PBMCs as the serum creatinine concentrations became elevated. In the dog kidney biopsies at later phases of rejection, IL-10 mRNA levels were also significantly elevated (p = 0.032).

Cloning and expression of the cDNA for canine tumor necrosis factor-alpha in E. coli

We have utilized the reverse transcription polymerase chain reaction (RT-PCR) to clone the protein coding region of canine tumor necrosis factor (TNF-alpha) cDNA. The gene displays 90% sequence homology to the corresponding human TNF-alpha cDNA. The predicted initial translation product is 233 amino acids and shows 88% homology to the human counterpart, and 92% homology with the human putative mature TNF-alpha protein. The canine TNF-alpha clone was used to engineer bacteria to express large amounts of the mature form of recombinant protein. A monoclonal antibody against human TNF-alpha cross-reacted with canine rTNF-alpha using Western blot and ELISA analysis. The purified canine rTNF-alpha had a cytotoxic effect on WEHI 164 clone 13 cells as well as increasing the cell surface expression of major histocompatibility class II antigens on canine kidney cortical cell line (MDCK) in vitro. The availability of canine rTNF-alpha will allow further studies on its role in immunoregulatory mechanisms in the canine transplantation model, both by itself and in conjunction with the already available canine specific recombinant interferon-gamma.

T cell receptor V beta 15 dominates the antiacetylcholine receptor response in Lewis rat T cell lines

Ten Lewis rat T cell lines responsive to Torpedo californica acetylcholine receptor (AChR) were assayed for TCR V beta usage. All lines were CD4+, OX-22-, and exhibited reactivity to one or more AChR chains. Several different V beta s were expressed by these lines, but V beta 15 was dominant in 5 of 10 lines. Unique CDR3 sequences were observed among the 10 lines, although three of the V beta 15 rearrangements used J beta 1.4. These data suggest that V beta 15+ T cells are selected in the in vitro response to the antigenically complex AChR in the Lewis rat.

Characterization of anti-canine cytokine monoclonal antibodies specific for IFN-gamma: effect of anti-IFN-gamma on renal transplant rejection

Two murine monoclonal antibodies specific for IFN-gamma, ADI-1, and ADI-23 (both IgG1 kappa), were generated in BALB/c mice. The ADI-1 exhibited a higher avidity for canine rIFN-gamma than for nIFN-gamma and human rIFN-gamma. In contrast, the ADI-23 showed equal avidity for the three IFN-gamma preparations. The anti-canine IFN-gamma mAb did not bind to mouse and rat rIFN-gamma. The ADI-1, and ADI-23 mAb were also tested for binding to human rTFN-alpha and, contrary to our expectations, it was found that ADI-23 showed significant binding to human rTFN-alpha and rIFN-gamma, in contrast to ADI-1. Both anti-canine IFN-gamma mAb stained 48-h PHA-induced dog lymphoblasts. A two-site mAb ELISA was developed, which was linear in the range of 7-500 ng of canine rIFN-gamma, which indicated that the two mAb detected non-overlapping epitopes on the canine rIFN-gamma molecule. We studied the effect of ADI-1 on the prolongation of canine renal allografts. Recipients of kidney allografts, that were treated with ADI-1 by continuous arterial infusion, were prolonged to 22 and 25 days, compared to 9 and 13 days for animals given the IgG1 isotype control.

T cell receptor V beta 15 dominates the antiacetylcholine receptor response in Lewis rat T cell lines

Ten Lewis rat T cell lines responsive to Torpedo californica acetylcholine receptor (AChR) were assayed for TCR V beta usage. All lines were CD4+, OX-22-, and exhibited reactivity to one or more AChR chains. Several different V beta s were expressed by these lines, but V beta 15 was dominant in 5 of 10 lines. Unique CDR3 sequences were observed among the 10 lines, although three of the V beta 15 rearrangements used J beta 1.4. These data suggest that V beta 15+ T cells are selected in the in vitro response to the antigenically complex AChR in the Lewis rat.

Differential effects of IFN-gamma on kidney cell expression of MHC class II molecules, kidney cell associated molecules and their stimulatory capacity in mixed lymphocyte kidney cell culture

Mixed cell co-cultures of lymphocytes responding to kidney cells (MLKC), islets of Langerhans (MLIC) and mixed lymphocyte culture (MLC), were used to clarify mechanisms in allogeneic and autoimmune (tissue-associated) antigen presentation. Fresh kidney cortical tubular cells (KC), Madin-Darby canine kidney (MDCK), and dog kidney (6247) (DK) cell lines were used in MLKC reactions, and islets of Langerhans were used in the MLIC as putative antigen presenting cells (APC). The stimulating cells were treated with purified or recombinant dog interferon-gamma (IFN-gamma), and the detection of class II MHC molecule expression was assessed by a moneclonal antibody (mAb) (B1F6). Transcription of MHC class II mRNA and IFN-gamma mRNA was measured by semiquantitative polymerase chain reaction, and detection of a kidney cell (tissue-associated) antigen molecule was assessed by the mAb I1F6 that recognizes 72 and 150 kDa tubular cell protein(s) (KT1). The MDCK cell line constitutively expressed low levels of MHC class II molecules and KT1. The steady-state level of the MHC class II mRNA transcription was virtually unaltered by treatment with IFN-gamma (400 units) for 48 hours; however, the MHC cell surface protein expression was enhanced. The KC and DK cell lines constitutively expressed KT1, but not MHC class II molecules; these cells required a minimum of 4000 units, and a 62-hour incubation with IFN-gamma was needed to upregulate both surface MHC class II molecules and the transcription of corresponding specific mRNA. In the MLKC reaction both the MDCK and DK cell lines, as well as fresh KC cells, could serve as lymphocyte activators. This could be amplified by exogenous IFN-gamma. The removal of APC from the responding T cell population did not reduce the IFN-gamma effect. This indicates that IFN-gamma treatment allows for the expression of all of the co-stimulating factors and/or adhesion molecules necessary for these cells to serve as (surrogate) APC (direct as opposed to indirect antigen presentation). The requirements for purified IFN-gamma to increase this amplification was greater in the MLKC reactions with kidney cells than in the MLC reactions. The mAbs anti-IFN-gamma and I1F6 differed in their ability to inhibit lymphocyte proliferation depending on the different cell types involved. The I1F6 inhibited the MDCK and DK cell-driven MLKC (in the absence of exogenous IFN-gamma).(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of antibody production by helper T cell clones in experimental autoimmune myasthenia gravis is mediated by IL-4 and antigen-specific T cell factors

Acetylcholine receptor (AChR)-specific rat T cell clones (CD4+, CD8-, and OX22-) were shown to secrete both Th1 and Th2 lymphokines, IL-2, IL-4, and IFN-gamma following stimulation with AChR. These clones helped production of antibody to AChR by B cells which was found to be regulated primarily by IL-4, not by IL-2, secreted by the T cells in response to AChR. Cell-free supernatants from some AChR-activated T cell clones led to production of low levels of antibody to AChR by B cell-enriched, AChR-primed lymph node cells. Supernatant-regulated help in antibody production by B cells was antigen specific, and antibodies to T cell receptors blocked the antigen-specific activity. Thus, supernatant-mediated help may not be due solely to IL-4, and other factors, possibly including some fragment of the T cell antigen receptor present in the supernatant, appear to contribute to helping antibody production by B cells.

Production and characterization of recombinant canine interferon-gamma from Escherichia coli

We have used the recently cloned cDNA for canine interferon-gamma (IFN-gamma) to engineer bacteria to produce large amounts of the recombinant cytokine. The resulting protein can be recognized by monoclonal and polyclonal antibodies largely species specific for canine IFN-gamma. The purified recombinant IFN-gamma (rIFN-gamma) also had biological activity in vitro in three assay systems: (i) vesicular stomatitis virus plaque inhibition, (ii) class II major histocompatibility complex antigen upregulation on canine kidney parenchymal cells, and (iii) amplification of in vitro tissue-associated lymphoproliferation, all known to be effected by native IFN-gamma (nIFN-gamma). The availability of large amounts of active canine rIFN-gamma will be an important tool in studies of the role of this cytokine in the widely used experimental canine organ transplant model and also will be of diagnostic and therapeutic veterinary interest.

A simplified ELISA for anti-receptor antibodies in myasthenia gravis

Nicotinic acetylcholine receptor (nAchR) from triton extracts of muscle adsorbed specifically and optimally to microtitration plates at pH 7.4 rather than at pH 9.6. An ELISA for anti-receptor antibodies in myasthenia gravis based on direct adsorption of the receptor at pH 7.4 is described (direct assay). The direct assay compares very well in sensitivity and specificity with an indirect assay, in which the receptor was attached through alpha-bungarotoxin adsorbed on the solid phase (correlation coefficient 0.94).

alpha-Bungarotoxin aggregates on radioiodination with chloramine-T but not with iodogen

The presence of polymer(s) of radioiodinated bungarotoxin (Bgt) in preparations iodinated with chloramine-T or with iodogen, was investigated by chromatography on Sephadex-G50. In addition to a monomeric peak (P2), chloramine-T preparations showed a high content of polymeric forms (16-43%) eluting in the void volume (P1), present only to the extent of 1-3% in iodogen preparations. In purified [125I]Bgt prepared by the iodogen method, the content of P1 increased on treatment with chloramine-T, in the absence of radioiodine. The nonspecific binding of [125I]Bgt to DE-81 filter discs was high in the case of chloramine-T preparations and proportional to the content of P1 in each batch. Purified P1 (polymer) but not P2 (monomer) showed a concentration-dependent high degree of binding to DE-81 discs.