Coevolution of hosts and microorganisms: an analysis of the involvment of cytokines in host-parasite interactions

Parasites may employ particular strategies of eluding an immune response by taking advantage of those mechanisms that normally guarantee immunological self-tolerance. Much in the way as it occurs during the establishment of self-tolerance, live pathogens may induce clonal deletion, functional inactivation(anergy) and immunosupression. At this latter level, it appears that certain pathogens produce immunosupresive cytokine-like mediators or provoke like host the secrete cytokines that will compromise the anti-parasite immune response. It appears that immune responses that preferentially involve T helper l cells (secretors of interleukin-2-and interferon-y) tend to be protective, whereas T helper 2 cells (secretors of IL-4, IL5, IL-6, and IL-10), a population that antagonizes T helper cells, mediate disease susceptibility and are immunopathological reactions. Cytokines produced by T helper 2 cells mediate many symptoms of infection, including eosinophilia, mastocytosis, hyperimmunoglobulinemia, and elevated IgE levels. Administration of IL-2 and IFN-y has beneficial effects in many infections mediated by viruses, bacteria, and protozoa. The use of live vaccinia virus might be an avenue for the treatment of or vaccination against infection. We have found that a vaccinia virus expressing the gene for human IL-2, though attenuated, precipitates autoimmune disease in immunodeficient athymic mice. Thus, although T helper l cytokines may have desired immunostimulatory properties, they also may lead to unwarranted autoaggressive responses.

Mechanisms of immune protection in the asexual blood stage infection by Plasmodium falciparum: analysis by in vitro and ex-vivo assays

Mechanisms of immune protection against the asexual blood stage infection by Plasmodium falciparum are reviewed. Recent studies of two independent lines of research developed at the Institute Pasteur, in humans and primate infections clearly indicate an obligatory interaction of antibodies and effector cells to express the anti-parasitic effect.

Cytological and isoenzyme analysis of the Bucay and Quevedo cytotypes of the onchocerciasis vector Simulium exiguum (Diptera: Simuliidae) in Ecuador

Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by processing a differentiated X chromosome, wich is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been estabilished, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibiling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or mostadult females of any one (cytotype-pure) collection.

Comparative chromatin analysis of Trypanosoma congolense

The chromatin of Trypanosoma congolense was analyzed by electron microscopy. The chromatin is organized as nucleosome filaments but does not form a 30 nm fiber. There are five groups of histones, including a histone H1-like protein, which has a molecular weight within the range of the core histones, and is extremely hydrophilic. Weak histone-histone interaction, a typical feature of trypanosoma chromatin, was found. These results are similar to those for T. cruzi and T. b. brucei, but differ significantly from those for higher eukaryotes. The results confirm the model of trypanosome chromatin, and support the theory of their early separation from the other eukaryotes during the evolution. T. congolensis is an excellent model for chromatin research on trypanosomes, because it is easy to cultivate and its chromatin has, a relatively high stability, compared to that of other trypanosomes.

The identification of Anopheles (Nyssorhynchus) rondoni (Diptera: Culicidae) in Mato Grosso, Brazil: an analysis of key character variability

A morphological study was made of a population of Anopheles (Nyssorhynchus) rondoni (Neiva and Pinto) from northern Mato Grosso, Brazil. This population usually lacked the primary key character of a dark basal band on hindtarsomere 3, i.e., hindtarsomere 3 was all white as in most other members of the subgenus. It was determined that this species can be recognized instead by the presence of a dark spot on the thorax made up of a large dark prescutellar space that is contiguous with a concolorous central area on the scutellum. A secondary character of a dark area on the costa created by the fusion of the humeral dark, presector dark and sector dark proximal spots is also usually reliable. Regression analyses comparing the lengths and ratios of the dark bands on hindtarsomeres 2 to those on 3 describe a straight line relationship. This suggests that the "atypical" population is at one end of a character gradient. We propose that in the subgenus Nyssorhynchus individuals that have a long basal band on hindtarsomere 2 are more likely to also have a basal band on hindtarsomere 3. The pupal stage of this species has not been previously described. Reared-associated specimens from this study show that the pupa can be easily differentiated from all other Nyssorhynchus by the relatively stout, usually 2 or 3 branched (1-5), setae 1 and 5 on segments IV-VII.

Analysis of the clonal diversity of Staphylococcus aureus methicillin-resistant strains isolated at João Pessoa, state of Paraíba, Brazil

To investigate the clonal diversity of Staphylococcus aureus strains isolated at João Pessoa, State of Paraíba, Brazil, digested genomic DNA were studied by pulsed-field gel electrophoresis (PFGE) in nine methicillin-resistant strains (MRSA) and three methicillin-sensitive strains (MSSA), selected among 67 isolates based on their antimicrobial susceptibility and epidemiology. The isolates were obtained between April and November 1992 from the Hospital of the Federal University of Paraíba, located in João Pessoa. Two MRSA isolates from the Oswaldo Cruz Hospital, São Paulo, Brazil, including an epidemic strain previously detected from different hospitals at the country were used as control. Five different patterns, were demonstrated by MRSA isolated in João Pessoa and these patterns were described in several epidemiologically unrelated hospitals in São Paulo. Our results suggest the interstate dissemination of a MRSA clone in João Pessoa which is similar to that described in other cities of Brazil.

A Preliminary Analysis of Insects of Medico-legal Importance in Curitiba, State of Paraná

A survey of the carrion fauna was made at two sites in Curitiba, State of Paraná, with the objective of describing the insects associated with carrion and setting up a preliminary data-base for medico-legal purposes in south Brazil. Vertebrate exclusion experiments were carried out in each season between 1994 and 1995 with a 250 g laboratory-bred rat (Rattus norvegicus). Five stages of decomposition were identified: fresh, bloated, decaying, dry and adipocere-like. Some species showed seasonal and site preference and so could be used to identify the probable place and season where death took place. Sarconesia chlorogaster (Diptera, Calliphoridae) was restricted to an open field site and to cooler months. Hemilucilia semidiaphana (Diptera, Calliphoridae) and Pattonella resona (Diptera, Sarcophagidae) were restricted to the forest site and warmer months. Phaenicia eximia (Diptera, Calliphoridae) and Oxyletrum discicolle (Coleoptera, Silphidae) were present at both sites throughout the year and could be useful for population level analysis. Dissochaetus murray (Coleoptera, Cholevidae) was present throughout the year at the forest site and was associated with the adipocere-like stage. Ants played an important role producing post-mortem injuries to the carcasses. Insects of 32 species are reported as being useful in community level approaches

Analysis of Respiratory Syncytial Virus in Clinical Samples by Reverse Transcriptase-Polymerase Chain Reaction Restriction Mapping

The aim of this study was to develop a polymerase chain reaction (PCR) for the detection of respiratory syncytial virus (RSV) genomes. The primers were designed from published sequences and selected from conserved regions of the genome encoding for the N protein of subgroups A and B of RSV. PCR was applied to 20 specimens from children admitted to the respiratory ward of "William Soler" Pediatric Hospital in Havana City with a clinical diagnosis of bronchiolitis. The PCR was compared with viral isolation and with an indirect immunofluorescence technique that employs monoclonal antibodies of subgroups A and B. Of 20 nasopharyngeal exudates, 10 were found positive by the three assayed methods. In only two cases, samples that yielded positive RNA-PCR were found negative by indirect immunofluorescence and cell culture. Considering viral isolation as the "gold standard" technique, RNA-PCR had 100% sensitivity and 80% specificity. RNA-PCR is a specific and sensitive technique for the detection of the RSV genome. Technical advantages are discussed

Analysis of Mycobacterium avium Complex Serovars Isolated from AIDS Patients from Southeast Brazil

The purpose of this study was to assess the distribution of Mycobacterium avium serovars isolated from AIDS patients in São Paulo and Rio de Janeiro. Ninety single site or multiple site isolates from 75 patients were examined. The most frequent serovars found were 8 (39.2%), 4 (21.4%) and 1 (10.7%). The frequency of mixed infections with serovar 8 or 4 was 37.8%. Among the 90 strains examined, M. intracellulare serovars (7 strains) and M. scrofulaceum (4 strains) were found in 11 isolates (12%) indicating that M. avium (88%) was the major opportunistic species in the M. avium complex isolates in Brazilian AIDS patients

Life Cycle and Fecundity Analysis of Lutzomyia shannoni (Dyar) (Diptera: Psychodidae)

The life cycle of Lutzomyia shannoni (Dyar), was described for laboratory conditions with maximum daily temperatures of 27-30°C, minimum daily temperatures of 22-27°C and relative humidity between 87-99 %. Life cycle in each stage was as follows: egg 6-12 days (ave. 8.5 days); first stage larva 5-13 days (ave. 9.6 days); second stage larva 4-13 days (ave. 9.2 days ); third stage larva 5-19 days (ave. 11.8 days); fourth stage larva 7-37 days (ave. 19.9 days); pupa 7-32 days (ave. 15.2 days). The life expectancy of adults ranged from 4 to 15 days (ave. 8.6 days). The entire egg to adult period ranged from 36 to 74 days (ave. 54.6 days). On average, each female oviposited 22.7 eggs; the average egg retention per female was 24.3 eggs.

Genetic and Antigenic Analysis of Adenovirus Type 3 Strains Showing Intermediate Behavior in Standard Seroneutralization Test

During an epidemiological survey of acute respiratory infection in Rio de Janeiro, among 208 adenovirus isolates, we found two strains that we were not able, by a standard neutralization procedure, to distinguish between type 3 or 7. However, DNA restriction pattern for the two strains with different enzymes were analyzed and showed a typical Ad3h profile. Using a cross-neutralization test in which both Ad3p and Ad7p antisera were used in different concentration against 100 TCID50 of each adenovirus standard and both isolates, we were able to confirm that the two isolates belong to serotype 3. An hemagglutination inhibition test also corroborated the identification of both strains as adenovirus type 3. Comparing Ad3h and Ad3p genome, we observed 16 different restriction enzyme sites, three of which were located in genomic regions encoding polypeptides involved in neutralization sites

Morphometric Analysis of McCoy Cells Inoculated with Cerebrospinal Fluid from Patients with Rabies

To demonstrate the potential of McCoy cells for the isolation of rabies virus from the cerebrospinal (CSF) fluid of a patient with a diagnosis of rabies, McCoy cells were inoculated with CSF from a patient with a clinical diagnosis of rabies and investigated in terms of morphometric aspect using the JAVA analysis system for the quantification of the increased size of infected cells compared to noninfected cells. The cells were also examined in terms of specific staining for the diagnosis of rabies by the method of Sellers for the observation of intracytoplasmic inclusions and by specific immunofluorescence staining for rabies virus. Infected cells showed changes in cell permeability and morphologic modifications which differed significantly compared to normal cells (P<0.001) when analyzed by the Mann-Whitney and Kruskal-Wallis tests. Intense activity of the endoplasmic reticulum was also observed, as indicated by the presence of intracytoplasmic inclusions visualized by specific staining. The present study demonstrated the isolation of rabies virus from the CSF of a patient with rabies, showing that McCoy cells can be used for the laboratory diagnosis of patients suspected to have rabies.