Dose-finding and efficacy study for i.m. artemotil (beta-arteether) and comparison with i.m. artemether in acute uncomplicated P. falciparum malaria.

AIMS: The antimalarial efficacy/pharmacodynamics and pharmacokinetics of intramuscular (i.m.) artemotil in Thai patients with acute uncomplicated falciparum malaria were studied to determine effective dose regimens and to compare these with the standard dose regimen of artemether. METHODS: In part I of the study three different artemotil dose regimens were explored in three groups of 6-9 patients for dose finding: 3.2 mg kg-1 on day 0 and 1.6 mg kg-1 on days 1-4 (treatment A), 1.6 mg kg-1 on day 0 and 0.8 mg kg-1 on days 1-4 (treatment B), 3.2 mg kg-1 on day 0 and 0.8 mg kg-1 on days 1-4 (treatment C). In part II of the study, artemotil treatments A and C were compared in three groups of 20-22 patients with standard i.m. artemether treatment: 3.2 mg kg-1 on day 0 and 0.8 mg kg-1 on days 1-4 (treatment R). RESULTS: Full parasite clearance was achieved in all patients in Part I, but parasite clearance time (PCT) and fever clearance time (FCT) tended to be longer in treatment B. Also the incidence of recrudescence before day 28 (RI) tended to be higher for treatment B. In part II, the mean PCT for each of the two artemotil treatments (52 and 55 h, respectively) was significantly longer than for artemether (43 h). The 95% CI for the difference A vs R was 0, 16 h (P=0.0408) and for difference C vs R it was 2, 19 h (P=0.0140). FCT was similar for the three treatments. The incidence of RI ranged from 5 out of 19 for treatment C to 3 out of 20 for treatment R. Plasma concentration-time profiles of artemotil indicated an irregular and variable rate of absorption after i.m. injection. A late onset of parasite clearance was associated with delayed absorption and/or very low initial artemotil plasma concentrations. Pharmacokinetic-pharmacodynamic evaluations supported a relationship between the rate of parasite clearance and exposure to artemotil during approximately the first 2 days of treatment, and suggested that artemotil has a slower rate of absorption than artemether. Safety assessment, including neurological and audiometric examinations showed no clinically relevant findings. Adverse events before and during treatment included headache, dizziness, nausea, vomiting and abdominal pain. These are characteristic of acute malaria infections and resolved during treatment. CONCLUSIONS: The optimum dose regimen for artemotil in this study was identical to the standard dose regimen of artemether. The findings that artemotil is more slowly absorbed from the i.m. injection site than artemether, and that early systemic availability may be insufficient for an immediate onset of parasite clearance contributed to the decision to choose a higher loading dose of artemotil (divided over two injection sites) and to omit the fifth dose in later studies. With this optimized dosing schedule, the more pronounced depot characteristics of i.m. artemotil can be an advantage, since it may allow shorter hospitalization.

Studies on the induction of antigen-specific antibody in anti-CD40 cultured human B lymphocytes.

Costimulatory signals provided by T cells are required for B cells to produce specific antibody to T-dependent antigen. We have investigated the suitability of using the CD40 culture system for the proliferation and differentiation of Ag-specific human B cells using cytomegalovirus (CMV) or tetanus toxoid (TT) as antigen. We modified the CD40 culture system (CD32-transfected L cells, anti-CD40, and IL-4) by applying a sequential cytokine stimulation and compared total B-cell cultures with antigen-specific B cells preselected by panning. The detection of specific antibody became possible when antigen-selected B cells were cultured for 7 days in the CD40 system to induce clonal expansion, followed by the addition of IL-2 and IL-10 for an additional 7 days to induce plasma-cell differentiation. We conclude that our initial inability to detect specific antibody in the CD40 system is due to overgrowth of nonspecific B-cell clones and that selection of antigen-specific B cells by panning overcomes this problem. Induction of antigen-specific antibody production was found to be optimal when the initial contact with antigen during panning was limited to between 1 to 24 hours.

Effect of B-cell receptor engagement on CD40-stimulated B cells.

Activation of human B cells in vitro either by cross-linking of surface immunoglobulins (sIg) or by triggering CD40 antigen, in the presence of interleukin-10 (IL-10) and interleukin-2 (IL-2), may result in high levels of immunoglobulin secretion in vitro. We studied the combined effects of ligation of the B-cell receptor (BCR) and CD40 [with anti-CD40 monoclonal antibody (mAb)] on B-cell proliferation and production of human immunoglobulin. For this purpose highly purified splenic B cells were cultured with various combinations of anti-CD40 and IL-10/IL-2 or IL-4 in the presence of CD32-transfected L cells. Simultaneous cross-linking of the BCR was achieved by mAb held on CD32-L cells or Staphylococcus aureus (SA). We found that dual BCR and CD40 ligation with IL-10/IL-2 leads to reduced immunoglobulin G (IgG) secretion compared with B cells stimulated with either anti-CD40 and IL-10/IL-2, or compared with B cells stimulated with SA or anti-BCR mAb and IL-10/IL-2. Dual BCR and CD40 ligation with anti-immunoglobulin mAb (anti-kappa + anti-lambda light chains) but not with SA induced a similar reduction in IgM production. The reduced immunoglobulin secretion found during dual ligation is accompanied by increased proliferation. This was independent of cytokine stimulation but SA/CD40-induced proliferation was increased in the presence of IL-10/IL-2, although not with IL-4. The combination anti-kappa and anti-lambda with anti-CD40 showed a long-term suppression of IgG and IgM production (at least 14 days), while anti-kappa or anti-lambda alone, or SA, allowed a moderate recovery of immunoglobulin production by day 14. These results suggest that simultaneous B-cell antigen receptor cross-linking and CD40 engagement via CD40L on T cells induces strong initial proliferation. This may be followed later by antibody production depending on the strength of the BCR signal and the presence of the appropriate cytokines.

Impaired antigen-specific B-cell response and altered splenic microstructure in mice following continuous administration of IL-4 in vivo.

The effect of long term in vivo administration of IL-4 on the induction of antigen-specific B cells, the splenic microenvironment and the yield of antigen-specific antibody producing hybridomas was studied. Immunization with DNP-KLH, followed by 12 weeks continuous IL-4 treatment resulted in increased numbers of total splenic (non-DNP) IgM and IgG AFC (antibody forming cells) on day 5 after booster, whereas the DNP-specific IgG and IgG1 AFC were reduced compared to age-matched control animals not treated with IL-4. In addition, an almost 300-fold increase in non-DNP IgE was found while the IgE anti-DNP response was minimal. When the splenic cells were used in a fusion protocol, a relative decrease in yield of antigen-specific hybridomas was found in the long term IL-4 treated mice. Immunohistological staining of spleen sections from mice treated with IL-4 up until the time of booster revealed reduced B-cell follicle area and germinal centre numbers. These results show that extensive IL-4 treatment reduced antigen-specific B-cell formation and suggests a reduction in the number of B cells entering the memory B-cell pathway in the spleen.

Increased production of antigen-specific B lymphocytes during in vitro immunization using carrier-specific T helper hybridomas.

An in vitro method to increase the production of hapten-specific antibody-forming B cells (AFC) using a carrier-specific T helper hybridoma and murine splenocytes is described. Naive splenocytes (6 x 10(6)/ml) are cultured in vitro in the presence of a hapten-carrier conjugate (DNP.OVA) and OVA-specific T helper hybridomas (0.5 x 10(6)/ml). After 4-5 days in vitro immunization (IVI), the maximum number of DNP-specific AFC were found using a spot-ELISA with twice the number of IgM positive cells as IgG positive AFC. The presence of antigen in the form of a hapten-carrier complex and the use of a carrier-specific Th hybridoma resulted in more hapten-specific AFC than when neither antigen nor Th hybridoma were present or when antigen alone or T help alone were used. Also when the hapten was conjugated to a carrier not recognised by the carrier-specific Th hybridoma there were considerably fewer (less than 50%) hapten specific AFC formed. When in vivo primed splenocytes (DNP) were boosted in vitro (IVB) under the same conditions as for IVI most hapten-specific AFC were found on day 4 and both anti-DNP IgM and IgG AFC were increased relative to IVI. Again most AFC were found when hapten was bound to the relevant carrier. In conclusion, carrier-specific T hybridomas can be used in an in vitro immunization procedure with naive or primed splenocytes to increase the frequency of anti-hapten AFC. This method offers an improvement over the current in vitro immunization procedures for the production of monoclonal antibodies.

Expression of class II major histocompatibility complex antigens on alveolar epithelium in interstitial lung disease: relevance to pathogenesis of idiopathic pulmonary fibrosis.

To determine whether expression of class II major histocompatibility complex antigens on alveolar epithelium is relevant to the pathogenesis of idiopathic pulmonary fibrosis (IPF) lung biopsy specimens were investigated from nine patients with IPF with or without connective tissue disease, four patients with sarcoidosis, eight patients with lung disease of presumably infectious origin, and five controls. The alveolar epithelium stained strongly with anti-Ia (HLA-DR) or Leu 10 (HLA-DS) monoclonal antibodies, in eight of nine biopsy specimens from patients with IPF, in three of four biopsy specimens from patients with sarcoidosis, in all six biopsy specimens from patients with presumably viral, mycobacterial, or pneumocystic lung disease, but not in control lung tissue, nor in two biopsy specimens from patients with bacterial pneumonia. Mononuclear cell infiltrates consisted of T4 positive (helper/inducer) lymphocytes, predominantly present in a nodular arrangement in the interstitium, and T8 positive (cytotoxic/suppressor) cells, distributed equally in the interstitium and subepithelially or intraepithelially. T8 cells outnumbered T4 cells in six of nine biopsy specimens from patients with IPF, but in none of the biopsy specimens from patients with sarcoidosis or interstitial lung disease of infectious origin. Although the expression of class II antigens on the alveolar epithelium which is infiltrated by T8 cells in IPF is consistent with local presentation of autoantigens and an ensuing local immune response, class II expression is also present in interstitial lung disease of sarcoidosis and microbial infections: its role in the pathogenesis of IPF must therefore remain speculative.

Expression of class II MHC antigens on alveolar epithelium in fibrosing alveolitis.

Lung biopsy specimens from eight patients with fibrosing alveolitis with or without connective tissue disease were investigated for the presence of immune deposits and the expression of class II histocompatibility antigens on the alveolar epithelium. Immune deposits were not detected. The alveolar epithelium stained strongly with anti-Ia (HLA-DR) monoclonal antibodies in seven out of eight biopsy specimens from the patients, but not in control lung tissue. Sub- and intra-epithelially localized mononuclear cell infiltrates consisted predominantly of T8-positive (cytotoxic/suppressor) lymphocytes. The expression of class II antigens on the alveolar epithelium and its infiltration with T8 positive cells is consistent with local presentation of self-antigens and an ensuing local immune response.