Retinoids: in vitro interaction with retinol-binding protein and influence on plasma retinol

Studies have been conducted to investigate the structure-function relationships of retinoids in their in vitro interaction with plasma retinol-binding protein (RBP) and in their influence on plasma retinol concentration. Two classes of retinoids, one bearing modifications in the area of the retinol hydroxyl end group (fenretinide, N-(ethyl) retinamide, all-trans, and 13-cis retinoic acid) and the other one also bearing modifications in the area of the cyclohexene ring (etretinate, acitretin, and arotinoid Ro 13-7410), were investigated. Whereas substantial modifications of the retinol hydroxyl group do not prevent the binding to RBP, an intact trimethylcyclohexenyl group seems to be crucial for binding. Both classes of retinoids, administered orally at equimolar doses, reduce plasma retinol concentration in rats but with different kinetics. A marked lowering of plasma retinol occurs early (within 5 h) after administration of retinoids that interact with RBP in vitro, whereas it occurs at later times (24 h) after retinoids that do not interact with RBP. The concentrations of both classes of retinoids found in plasma do not account for the temporal difference in this effect. The early reduction of plasma retinol might be the consequence of in vivo specific binding of retinoids to RBP, as suggested by the in vitro results. The late reduction observed for retinoids lacking in vitro affinity for RBP is due to other mechanisms or to metabolism to retinoids binding to RBP.

[Mental retardation and family environment: role of emotional factors]

The authors present data from an experimental study conducted on 20 institutionalized mentally handicapped adult patients. Relevant family variables were investigated by means of the Expressed Emotion (EE) scales, then compared with similar variables obtained in a matched sample of 20 schizophrenic patients and their families. Results show, in relatives of mentally handicapped patients, a higher rate of Warmth than in relatives of schizophrenics (p = 0.009), while other EE scales appear to reach similar values in both groups. Within the mentally handicapped family group, a higher rate of Emotional Over-involvement (p = 0.046) is shown by relatives of patients treated with neuroleptic drugs. The presence of high Warmth and Emotional Over-involvement, together with low Criticism and Hostility, may be interpreted as adaptation by the families to an organic disease with very early onset, clearer ad less rejecting than schizophrenia.

Occurrence of resistance to retinoic acid in the acute promyelocytic leukemia cell line NB4 is associated with altered expression of the pml/RAR alpha protein

The mechanism(s) by which acute promyelocytic leukemia (APL) cells acquire resistance to all-trans retinoic acid (ATRA) is poorly understood. We describe here an APL cell line, named NB4.306, that shows resistance to the anti-proliferative action of ATRA. This cell line is also operationally resistant to most ATRA-induced phenotypic modifications (CD11b, CD11c, CD13, and CD33). No significant differences in ATRA intracellular accumulation, efflux, or metabolism were found between NB4.306 and the parent NB4 cell line that could explain the observed resistance of the NB4.306 line. The NB4.306 cell line was found to be positive for the t15;17 translocation and showed the usual pml/RAR alpha fusion bands in both Southern and Northern blot assays, but expressed no detectable amount of the usual pml/RAR alpha protein, as assayed by Western blot analysis using an anti-RAR alpha antibody. These results were confirmed in 14 of 14 clones obtained from the NB4.306 cell line, while 30 of 30 clones obtained from the parental NB4 line expressed the usual 110-Kd fusion polypeptide. It is concluded that the occurrence of resistance to ATRA in the NB4.306 cell line is closely associated to the loss of expression of the intact pml/RAR alpha protein.

Alloactivated cytotoxic T cells recognize the carboxy-terminal domain of human immunodeficiency virus-1 gp120 envelope glycoprotein

Infection with the human immunodeficiency virus (HIV) virus leads to clinical disease in humans but not in chimpanzees. Progression to disease is associated with activation of the immune system followed by loss of T helper cell function and a slow decline in CD4-positive lymphocytes. The presence of autoreactive and cytotoxic cells in humans but not chimpanzees suggests that mechanisms other than, or in addition to, direct virus-induced cell killing, are required for disease to develop. The observed changes are similar to those seen in chronic allogeneic disease. Here we show that a peptide from the carboxy terminus of gp120, predicted to have a structure similar to the major alpha-helices of major histocompatibility complex (MHC) class I and class II, acts as a cytolytic target when presented on syngeneic cells for alloactivated cytotoxic T effector cells. These data add further evidence to the hypothesis that HIV can act as an allostimulant due to its dual properties of CD4 binding and MHC mimicry. The ability to signal nonspecifically through the T cell receptor could explain the initially paradoxical responses of proliferation, anergy and apoptosis.

Adjuvant treatment of stage I lung cancer with high-dose vitamin A

PURPOSE

Vitamin A and retinoids are strong inhibitors of epithelial cancer promotion and progression in experimental carcinogenesis. This study examined whether they may prevent the occurrence of upper aerodigestive cancer in subjects heavily exposed to tobacco smoking, such as patients already cured of an early-stage lung cancer.

PATIENTS AND METHODS

The adjuvant effect of high-dose vitamin A was tested on 307 patients with stage I non-small-cell lung cancer. After curative surgery, patients were randomly assigned to either a group prescribed retinol palmitate administration (orally 300,000 IU daily for 12 months) or a control group prescribed no treatment.

RESULTS

After a median follow-up of 46 months, the number of patients with either recurrence or new primary tumors was 56 (37%) in the treated arm and 75 (48%) in the control arm. Eighteen patients in the treated group developed a second primary tumor, and 29 patients in the control group developed 33 second primary tumors. A statistically significant difference in favor of treatment was observed concerning time to new primary tumors in the field of prevention (P = .045, log-rank test). The treatment difference in terms of disease-free interval was close to statistical significance (P = .054, log-rank test) and just significant when adjusted for primary tumor classification (P = .038, Cox regression model).

CONCLUSION

Daily oral administration of high-dose vitamin A is effective in reducing the number of new primary tumors related to tobacco consumption and may improve the disease-free interval in patients curatively resected for stage I lung cancer. The impact of such a treatment on survival needs to be further explored.

Analysis of T helper and antigen-presenting cell functions in cord blood and peripheral blood leukocytes from healthy children of different ages

The development of antigen-specific functional T lymphocyte immunity in infants and children is an area of immunology that needs elucidation. Leukocytes from cord blood (CBL) and from PBL of children of different ages who were in the hospital for minor surgical procedures were compared with PBL from healthy adults for their ability to generate T helper cell (Th) responses assessed by in vitro proliferation and IL-2 production after stimulation with: influenza A virus (FLU); tetanus toxoid (TET); adult allogeneic PBL that were either undepleted (ALLO) or depleted of adherent antigen presenting cells (ALLONW); and PHA. CBL generated Th responses to ALLONW, ALLO, and PHA, but not to FLU or TET. PBL from infants between 6 and 13 mo of age responded to ALLO and PHA; none responded to FLU or ALLONW, and two of four responded weakly to TET. PBL from children between 13 and 26 mo of age responded to all stimuli except FLU, to which only one child responded marginally. PBL from children older than 36 mo responded to all stimuli at levels comparable to those of PBL from adults. The use of undepleted and adherent cell-depleted CBL and PBL from children of different ages as allogeneic stimulators of responses generated by PBL from adults indicated that the antigen presenting function of CBL and PBL from children 13 mo or older are sufficiently developed to present alloantigen, whereas PBL from children younger than 13 mo are not. Therefore, our results indicate that age-dependent differences exist in both T helper and antigen-presenting functions of CBL and PBL from children of different ages. Surprisingly, CBL appear to be more efficient in antigen-presenting function than PBL from children younger than 13 mo. These findings are important for establishing developmental parameters of T helper cell immunity relevant for pediatric infection and transplantation in infants and children.

Changes in interleukin-2 and interleukin-4 production in asymptomatic, human immunodeficiency virus-seropositive individuals

Infection with HIV results in an incremental loss of T helper cell (TH) function, which can occur years before CD4 cell numbers are critically reduced and AIDS is diagnosed. All TH function is not affected, however, because B cell activation and hypergammaglobulinema are also characteristic of this period. Recently, in a murine model of AIDS an early loss in production of the CD4 cytokines IL-2 and IFN-gamma was correlated with an increase in the B cell stimulatory cytokines IL-4, IL-5, and IL-10. We therefore assessed the production of IL-4 generated by PBL from HIV-seropositive (HIV+) individuals who did not have AIDS, yet who exhibited different TH functional categories based on their IL-2 production profiles. We observed that the decreases in recall antigen-stimulated IL-2 production were accompanied by an increase in IL-4 production. The loss of recall antigen-stimulated responses in HIV+ individuals could be reversed in vitro by anti-IL-4 antibody. Our results suggest that the TH functions assessed by IL-4 production replace the normally dominant TH function of antigen-stimulated IL-2 production in the progression toward AIDS, and raise the possibility of cytokine cross-regulation in AIDS therapy.

[Solid tumors associated with HIV infection]

Between December 1986 and December 1991, the Italian Cooperative Group on AIDS-related tumours documented 94 HIV related solid tumours. Of 21 germinal testicular tumours collected, ten were seminomas. Cervical carcinoma was observed observed in 28 IVDAs (intraepithelial in 8 and advanced, with rapid progression, in one). Lung cancer associated with HIV infection was reported in 14 patients. Also reported were two cases of colorectal carcinoma, one anorectal carcinoma, one pancreatic carcinoma, one carcinoid, one oral carcinoma. Of the central nervous system tumours, were diagnosed 3 cases of glioblastomas, one medulloblastoma and one meningioma. This retrospective study shows that while oral and anorectal tumours were very rarely observed, a wide spectrum of other HIV-related solid tumours were found in this series. The required therapeutic approaches may not necessarily be influenced by the HIV infection, in contrast with the observed pattern for treatment of EKS and lymphomas in HIV infected subjects.

A TH1-->TH2 switch is a critical step in the etiology of HIV infection

This viewpoint proposes that an imbalance in the TH1-type and TH2-type responses contributes to the immune dysregulation associated with HIV infection, and that resistance to HIV infection and/or progression to AIDS is dependent on a TH1-->TH2 dominance. This hypothesis is based on the authors' findings that: (1) progression to AIDS is characterized by loss of IL-2- and IFN-gamma production concomitant with increases in IL-4 and IL-10; and (2) many seronegative, HIV-exposed individuals generate strong TH1-type responses to HIV antigens.

A cisplatinum-cyclophosphamide regimen in advanced ovarian cancer: reporting 5-year results

The following paper reports the evaluation of 53 consecutive patients with advanced ovarian epithelial carcinoma (FIGO stage III-IV), treated between October 1984 and December 1987 with immediate or delayed cytoreduction surgery and chemotherapy. Combination chemotherapy consisted of cisplatinum 45 mg/m2 i.v. for 2 consecutive days and cyclophosphamide 900 mg/m2 i.v. on the second day, administered every 28 days for a maximum of 8 courses. Objective responses were observed in 35 of 50 evaluable patients (70%), 17 (34%) of whom were pathological complete remissions (pCR). For patients with minimal residual disease before chemotherapy a higher pCR rate was achieved (10/20 vs. 7/30; p = N.S.). Median survival time of all patients was 29 months; subjects with minimal residual disease and good performance status before treatment had higher survival (48 vs. 22 months-p < 0.05 and 29 vs. 9 months-p < 0.05, respectively). Median time to progression was 25 months. After a median follow-up of 60 months, 15 (28%) patients were alive, 14 of whom disease-free. Toxicity was moderate with a particularly low incidence of nephrotoxicity and no case of serious long-lasting neuropathy. These findings suggest that the described combination has an efficacy comparable to other CDDP-containing combinations, using 2, 3 or more drugs, with a low incidence of acute serious toxicities and of disabling delayed sequelae.

Limiting dilution analysis of interleukin-2-producing T cells responsive to recall and alloantigens in human immunodeficiency virus-infected and uninfected individuals

Peripheral blood mononuclear cells (PBMC) from individuals who were seropositive for the human immunodeficiency virus type 1 (HIV), and most without symptoms (HIV+) were compared with PBMC from healthy HIV-seronegative (HIV-) individuals for in vitro generated T helper cell (Th) responses. Th function in bulk culture and limiting dilution analysis was assessed by IL-2 production following stimulation with influenza A virus (FLU) or irradiated allogeneic PBMC (ALLO). We observed that the frequencies of FLU- and ALLO-stimulated Th cells were not appreciably different in the PBMC of HIV- individuals, and that they were also not different in the PBMC of those HIV+ individuals who responded to both FLU and ALLO in bulk culture. However, there was a severe drop in the Th frequency to FLU in HIV+ individuals who were unresponsive to FLU but responsive to ALLO by bulk culture. The PBMC of HIV+ individuals who were unresponsive by bulk culture to both FLU and ALLO exhibited a drastic reduction in the Th frequencies for both stimuli. These results demonstrate a concordance between Th functional analysis performed by limiting dilution and bulk culture. The results also indicate that the early selective loss in Th function to recall antigens is not likely to be due simply to a difference in frequencies of FLU- and ALLO-stimulated Th cells present prior to the onset of Th dysfunction.

Abnormalities of immune regulation in human immunodeficiency virus infection

The severe depletion of CD4+ T cells is the most obvious and dramatic immunologic event that occurs in individuals infected with the human immunodeficiency virus (HIV) type 1 during development to AIDS. Nevertheless, a complex and sequential pattern of loss of T-helper cell (TH) function can occur years before development of AIDS symptoms. Such suppression could be due to immunosuppressive factors that are either products of HIV, such as gp120 and tat, or HIV-induced immunoregulatory cytokines such as transforming growth factor-beta and IL-10. Recent data suggest that multiple and independent immunosuppressive factors, including gp120-induced suppression and IL-10, are responsible for the loss of TH function seen in HIV-infected individuals before development of symptoms. The same TH functional abnormalities observed in adult patients are also seen in pediatric cases. Pediatric cases of HIV infection present some unique problems, however, in that one needs to be able to distinguish between HIV-induced suppression of TH function and the absence of TH function that is due to lack of maturation or immunologic priming.

Changes in T-helper cell function in human immunodeficiency virus-infected children during didanosine therapy as a measure of antiretroviral activity

Didanosine has shown activity against the human immunodeficiency virus (HIV) in both children and adults. We prospectively assessed T-helper cell (Th) function as determined by in vitro interleukin-2 (IL-2) production in response to a panel of T-cell stimuli in 22 HIV-infected children before and during didanosine therapy and we correlated the incidence of opportunistic and recurrent bacterial infections with changes in p24 antigen and CD4 counts. Didanosine (270, 360, or 540 mg/m2/d) was administered orally for periods ranging from 8 to 40 weeks (mean, 24 weeks). Five of six asymptomatic patients (Centers for Disease Control P-1) compared with 6 of 16 symptomatic (P-2) patients exhibited improved Th function (greater than threefold increase in IL-2 production to at least 2 of the 4 stimuli) during therapy. Of 12 patients without infections during therapy, 9 (75%) showed improvement in Th function, compared with only 2 of 10 patients with infections (P = .03). Notably, the incidence of infections was not correlated with improvements in CD4 count or decreases in p24 antigen. Improvement in Th function during didanosine therapy is correlated with decreased incidence of infections. Assessment of Th function may provide an additional measurement of immunologic response to antiretroviral therapy.

How human immunodeficiency virus ravages the immune system

The immune system of individuals infected with human immunodeficiency virus is affected in two distinct ways: by loss of CD4+ cells and by loss of T-helper-cell function. Neither of these processes is yet fully understood. Research during 1991 that investigated the interaction between human immunodeficiency virus and the immune system has raised as many questions as it answered. Nevertheless, many of the issues raised are relevant to mechanisms responsible for the ravaging of the immune system by human immunodeficiency virus.

Reconstitution of long-term T helper cell function after zidovudine therapy in human immunodeficiency virus-infected patients

Peripheral blood mononuclear cells from 12 asymptomatic patients infected with immunodeficiency virus (HIV) and 4 patients with AIDS were analyzed before and during therapy with zidovudine for T helper cell (Th) function. Th function improved by more than fourfold to one or more of three stimuli tested in 9 (75%) of 12 asymptomatic patients on zidovudine therapy and in 3 of 4 patients with AIDS. Only 6 (7.4%) of 80 untreated HIV-infected control patients showed spontaneous improvement in Th function (P less than 10(-6)). Improved Th function was detected as early as 5 weeks into therapy in 6 patients and continued to be evident for greater than 1 year after start of therapy in 6 patients and for greater than 2 years in 2 patients. No correlation was observed between improved Th function and changes in CD4+ or CD8+ cell numbers or in levels of serum HIV p24 antigen or beta 2-microglobulin. These results suggest inclusion of in vitro Th function as a useful marker in determining the efficacy of antiretroviral drug therapy of HIV-infected patients.

Prevention of local relapses and new localisations of oral leukoplakias with the synthetic retinoid fenretinide (4-HPR). Preliminary results

This paper analyses preliminary results of a randomised chemoprevention trial in patients surgically treated for oral leukoplakia started in 1988 at the Istituto Nazionale Tumori of Milan with the synthetic retinoid N-(4-hydroxyphenyl)-retinamide (4-HPR). To date 115 patients have been randomised, after surgical excision of oral leukoplakia, to receive 200 mg 4-HPR daily for 52 weeks versus no intervention. 80 patients completed the 1-year intervention, 41 in the control group and 39 in the 4-HPR group. During this period 12 local relapses or new lesions occurred in the control group and three in the 4-HPR group. Only 5 patients interrupted the intervention because of toxicity. No impaired dark adaptation was observed. It is concluded that 4-HPR is well tolerated and seems efficacious in preventing relapses and new localisations during the treatment period. This promising trend needs further confirmation.

Role of T-cell derived cytokines in the downregulation of immune responses in parasitic and retroviral infection

Parasitic infection is frequently accompanied by a downregulation in host cell-mediated immunity. Recent studies suggest that this modulation of helper T cells and effector cell function can at least in part be attributed to the action of a set of inhibitory cytokines produced by T lymphocytes as well as by a number of other cell types. The best characterized of these inhibitory lymphokines are IL-4, IL-10 and TGF-beta. Interestingly, both IL-4 and IL-10 are produced by the Th2 but not the Th1 subset of CD4+ helper cells. The former subset dominates in many situations of chronic or exacerbated parasitic infection and is thought to suppress Th1 function as a consequence of the cross-regulatory activity of these two cytokines. The latter hypothesis is supported by recent experiments demonstrating that mAb-mediated neutralization of IL-10 reverses suppressed IFN-gamma responses and/or disease susceptibility in mice with parasitic infections. In vivo neutralization of TGF-beta has also been reported to increase host resistance to parasite challenge. In addition to suppressing T-cell differentiation, function or proliferation, IL-4, IL-10 and TGF-beta each inhibit the ability of IFN-gamma to activate macrophages for killing of both intracellular and extracellular parasites. Moreover, the three cytokines are able to synergize with each other in downregulating these parasiticidal effects. Interestingly, each of the cytokines inhibits the production of reactive nitrogen oxides, an effector mechanism previously demonstrated to play a major role in parasite killing by activated macrophages. In the case of IL-10, this suppression of nitrogen oxide production appears to result from an inhibition of TNF-alpha synthesis leading to defective macrophage stimulation. While distant from parasites in their biology and phylogeny, some retroviruses also appear to induce an over-production in downregulatory cytokines which is closely associated with the onset of immunodeficiency. Thus, in an animal model involving infection of mice with LP-BM5 MuLV and in human HIV infection, Th2 (IL-10 and/or IL-4) cytokine synthesis is increased while Th1 (IFN-gamma and/or IL-2) cytokine production is suppressed. These observations suggest that cytokine-mediated cross-regulation may play a role in the pathogenesis of acquired immune deficiency disease, contributing both to the progression of retroviral infection and the increase in susceptibility to opportunistic infections and malignancy. Observations of similar cytokine cross-regulatory activities in organisms as diverse as helminths, protozoa and retroviruses predict that comparable mechanisms may operate in a wide variety of infectious diseases.

A factor from CD8 cells of human immunodeficiency virus-infected patients suppresses HLA self-restricted T helper cell responses

Defective in vitro T helper cell (Th) function can occur in asymptomatic human immunodeficiency virus (HIV)-seropositive (HIV+) individuals. A characteristic, early finding is the loss of an in vitro response to recall antigens, such as influenza A virus (FLU), despite an intact Th response to alloantigen (ALLO). To determine whether suppressor cells and/or inhibitory factors could contribute to this HIV-associated Th immunodeficiency, coculture studies were performed using peripheral blood leukocytes (PBLs) from monozygotic twins, one of whom was HIV-infected (HIV+) and one of whom was uninfected (HIV-seronegative, HIV-). In vitro Th function was measured as interleukin 2 production or proliferation to FLU and ALLO. Two pairs of twins were repetitively studied. A single HIV+ individual with multiple samples of cryopreserved PBLs over 6 years (including a HIV- specimen) was also studied. PBLs from the HIV+, but not from the HIV-, individuals demonstrated defective in vitro Th function in response to FLU but not to ALLO. PBLs from HIV+ individuals could induce a similar defect in the Th function of syngeneic or autologous HIV- PBLs. This suppression was generated by CD4-depleted, but not by CD8-depleted, PBLs. A suppressive factor from CD8+ cells of HIV+ donors was generated by 24-hr unstimulated cultures of HIV+ PBLs. This factor inhibited FLU but not ALLO responses of autologous, syngeneic, or allogeneic HIV- PBLs. This suppressive effect could not be explained by HIV infection or replication during the culture period. These results demonstrate that selective abrogation of Th function to recall antigens in HIV+ individuals is associated with an inhibitory factor produced by CD8+ T cells.

Expressed emotion and schizophrenia in Italy. A study of an urban population

Forty-two schizophrenic patients and their close relatives took part in an Italian replication study of expressed emotion (EE). The patients were selected from the psychiatric ward of a general hospital in Milan and were subsequently followed up for nine months. All patients attended a community service clinic as out-patients, and all but one were prescribed neuroleptics for the duration of the study. Relatives were assigned to the high-EE group if they scored 4 or 5 on the emotional overinvolvement (EOI) scale, or showed hostility, or made six or more critical comments. On this basis, 18 (42%) families were rated as low EE and 24 (57%) as high EE. At follow-up, the admission rate for the 9-month period was significantly higher for the high-EE group (P less than 0.05). Furthermore, significantly fewer patients were readmitted from families showing high warmth (P less than 0.05). The presence of high warmth appeared to be associated with a lower admission rate, even in high-EE families.