Phase I clinical evaluation of a neutralizing monoclonal antibody against epidermal growth factor receptor in advanced brain tumor patients: preliminary study

High levels of growth factors and their receptors have been demonstrated in human tumors. Gliomas and meningiomas are characterized by overexpression of epidermal growth factor receptor (EGF-R). Ior egf/r3, is a neutralizing murine monoclonal antibody (MAb) against EGF-R, and was generated at the Cuban Institute of Oncology. The antibody recognizes EGF-R with high affinity, inhibiting tyrosine kinase activation. A clinical trial was conducted in brain tumor patients to evaluate toxicity, immunogenicity, and clinical benefit of escalating doses of the antibody. Nine patients with histologically confirmed gliomas or meningiomas, who had active or recurrent disease after receiving conventional treatment, received four intravenous doses of ior egf/r3. Total dosages ranged from 160 to 480 mg. As inclusion criteria, radioimmunoscintigraphy with the same MAb labeled with 99mTechnetium (99mTc) was performed. Immune response against the murine antibody was also evaluated. After four doses of ior egf/r3 MAb, no significant toxicity was found, except in one patient who developed a grade 4 allergic adverse event. This reaction was probably related with previous sensitization to the same MAb and the development of human anti-mouse antibodies (HAMA) response. Despite no major objective antitumor responses, eight patients had stable disease on the 6-month evaluation, and two patients remain alive after four years of MAb therapy.     

Chlamydophila abortus (Chlamydia psittaci serotype 1) clearance is associated with the early recruitment of neutrophils and CD8(+)T cells in a mouse model

The immune mechanisms in response to Chlamydophila abortus (Chlamydia psittaci serotype 1) infection were studied in C57BL/6 and CBA mice. The infection was monitored and the following aspects of the immune response were evaluated: the nature of the leucocyte infiltrate in the liver, the percentages of polymorphonuclear neutrophils (PMNs), macrophages and lymphocytes in the spleen, and the concentrations of cytokines in serum. In addition, the serum concentrations of IgG1 and IgG2a were determined. Both mouse strains showed a Th1-like immune response, with high concentrations of IFN-gamma and minimal levels of IL-4; however, C57 mice differed from CBA mice in showing milder clinical signs and earlier resolution of infection. The greater ability of C57 mice than CBA mice to eliminate chlamydophilae was related to the establishment of an earlier innate immunity, based on a more pronounced PMN response, and on a greater presence of CD8(+)T cells.     

Two new mutations and three novel polymorphisms in the<Emphasis Type="Italic"> RB1</Emphasis> gene in Ecuadorian patients

RB1 is the gene responsible for retinoblastoma, the most common malignant intraocular tumor of infancy and early childhood. There are no reports about this gene in Ecuadorian populations, and only a few studies have been published in Latin America about this subject. There is a spectrum of more than 370 mutations described in the RB1 gene mutation database (http://www.d-lohmann.de/Rb/mutations.html), and alterations have been found in 25 of the 27 exons. During the exon-by-exon analysis of 31 tumor and blood samples from Ecuadorian patients, we found two new mutations and three novel polymorphisms. One of the polymorphisms is located in intron 26 where no alterations of the gene have been described previously. The polymorphisms were found in all of the patients tumor samples, but not in normal population, suggesting there might be a relationship between these polymorphisms and the development of retinoblastoma in the Ecuadorian population.The nucleotide sequence data reported are available in the GenBank database under the accession numbers: AY243567, AY260472, AY260473, AY273783     

Extended-spectrum beta-lactamases in clinical isolates of enterobacteria in Mexico

Resistance to extended-spectrum cephalosporins within members of the family Enterobacteriaceae occurs virtually world-wide. Nevertheless, nothing was known about this problem among isolates from Mexico. To address this issue, we studied oximino-cephalosporin resistant isolates of Klebsiella pneumoniae (13), Escherichia coli (7), and Enterobacter cloacae (23) recovered from patients in Mexico City hospitals during 1990 to 1992. In the presence of clavulanic acid, these strains increased susceptibility to cefotaxime and ceftazidime (MIC90 64 and >256 microg/ml, respectively). The ability of these isolates to transfer resistance to both antibiotics by conjugation was most successfully demonstrated by K. pneumoniae. In all the clinical isolates tested, the largest plasmid coded for the extended-spectrum beta-lactamases (ESBL). Characteristics of pI, by isoelectric focusing (IEF)/bioassay and DNA hybridization with specific probes of TEM and SHV, indicated that in most of the clinical isolates and all transconjugates, the most frequent beta-lactamase coded were SHV-derived (20 strains as 41% of isolates) and a plasmid-encoded beta-lactamase (12 strains as 25% of isolates) (with a pI of >8.2), which is not related to TEM/SHV. Apparently, isolates from Mexico show characteristics similar to isolates from other geographic areas. The type of beta-lactamases coded in these resistant isolates is documented for the first time in Mexico.     

Odor response properties of neighboring mitral/tufted cells in the rat olfactory bulb

Olfactory perception initiates in the nasal epithelium wherefrom olfactory receptor neurons--expressing the same receptor protein--project and converge in two different glomeruli within each olfactory bulb. Recent evidence suggests that glomeruli are isolated functional units, arranged in a chemotopic manner in the olfactory bulb. Exposure to odorants leads to the activation of specific populations of glomeruli. In rodents, about 25-50 mitral/tufted cells project their primary dendrites to a single glomerulus receiving similar sensory input. Yet, little is known about the properties of neighboring mitral/tufted cells connected to one or a few neighboring glomeruli. We used tetrodes to simultaneously record multiple single-unit activity in the mitral cell layer of anesthetized, freely breathing rats while exposed to mixtures of chemically related compounds. First, we characterized the odorant-induced modifications in firing rate of neighboring mitral/tufted cells and found that they do not share odorant response profiles. Individual units showed a long silent (11.01 ms) period with no oscillatory activity. Cross-correlation analysis between neighboring mitral/tufted cells revealed negligible synchronous activity among them. Finally, we show that respiratory-related temporal patterns are dissimilar among neighboring mitral/tufted cells and also that odorant stimulation results in an individual modification that is not necessarily shared by neighboring mitral/tufted cells. These results show that neighboring mitral/tufted cells frequently exhibit dissimilar response properties, which are not consistent with a precise chemotopic map at the mitral/tufted cell layer in the olfactory bulb.     

Effects of hormonal replacement with androgens and estrogens on male sexual behavior and plasma levels of these steroids in gonadectomized golden hamsters (Mesocricetus auratus)

Because the endocrine control of sexual behavior in male hamsters remains controversial, this study analyzed the influence of different androgens and estrogens in the regulation of masculine, sexual behavior (MBS). Aromatizable androgens: androstenedione (A) and testosterone (T), a non-aromatizable androgen: 5α-dihydrotestosterone (DHT), as well as estrogens (E₂ and E₁) alone or in combination with DHT, were administered in gonadectomized, sexually experienced males, for 3 weeks. In addition, plasma levels of these steroids were determined. Gonadectomy completely suppressed masculine sexual behavior (MSB) after 4 weeks. Both A and T replacements restored all the sexual behavior parameters in castrated hamsters by the 3rd week of treatment, with A being more potent in restoring all copulatory series and maintaining all MSB parameters, including long intromissions. Castrated males treated with DHT showed little interest in the female and did not display any copulatory behavior. Gonadectomized males treated with estrogens alone showed active anogenital investigation and displayed some mounts, but did not ejaculate. Males treated with estrogens combined with DHT had longer latencies and less number of ejaculations than males treated with aromatizable androgens. Long intromissions were observed only in males treated with T or A. Plasma levels of A were significantly higher than T levels in intact males. In males treated with A both androgens and estrogens were present in plasma. These results support the notion that aromatizable androgens, mainly A, but not non-aromatizable androgens or even estrogens in combination with DHT, play a relevant role in the endocrine regulation of MSB in the golden hamster.     

Platelet-activating factor receptor deficiency delays elimination of adult worms but reduces fecundity in Strongyloides venezuelensis-infected mice

We describe the parasitological kinetics and histopathological and immunological alterations in platelet-activating factor receptor-deficient (PAFR(-/-)) and wild-type mice after a single Strongyloides venezuelensis infection (subcutaneous inoculation of 500 L3 larvae). There was no difference in the numbers of worms that reached and became established in the small intestines of PAFR(-/-) and wild-type mice. However, at 12 days after infection, significantly more worms were recovered from PAFR(-/-) mice. Although PAFR(-/-) infected mice showed a delay in elimination of adult worms, worms established in the small intestine of these mice produced a significantly lower number of eggs due to a reduction in worm fecundity. There were also significant reductions in the number of circulating and tissue eosinophils and tumor necrosis factor levels in the small intestines of PAFR(-/-) mice infected for 7 days compared to the number and level in wild-type mice. Histological analysis confirmed the reduced inflammatory process and revealed that the PAFR(-/-) mice had a smaller number of goblet cells. The concentrations of the type 2 cytokines interleukin-4 (IL-4), IL-5, and IL-10 were lower in small intestine homogenates and in supernatants of antigen-stimulated lymphocytes from spleens or mesenteric lymph nodes of PAFR(-/-) mice than in the corresponding preparations from wild-type mice. Thus, in S. venezuelensis-infected PAFR(-/-) mice, decreased intestinal inflammation is associated with enhanced worm survival but decreased fecundity. We suggest that although a Th2-predominant inflammatory response decreases worm survival, the worm may use factors produced during this response to facilitate egg output and reproduction. PAFR-mediated responses appear to modulate these host-derived signals that are important for worm fecundity.