Chromium Induced Histological Changes in the Body Wall of the Earthworm Eudrillus eugeniae

In Sri Lanka, documented evidence indicates that the Chromium (Cr) content in water andsoil is high, reaching upto 0.60 mgl-1 in water and 103 mg kg-1 in soil and sediment. Cr is oneof the most toxic heavy metals, which is capable of inducing adverse effects in exposedorganisms even in trace amounts. Of the two valency states, Cr3+ and Cr6+, the latter ispotentially more toxic than the former. In the present study we examined the histologicalalterations in the body wall of Eudrillus eugeniae, a commonly occurring species ofearthworm, exposed to hexa-valent Cr.Adult earthworms were collected from a culture facility in Talawakalle, and acclimatized fortwo weeks. Worms with a well-developed clitellum and of 0.29 + 0.009 g weight were usedfor standard chronic exposure trials of 28 days. For the trials, the animals were placed insuitably prepared clay pots containing banana piths soaked in five different concentrations(0.002 – 20 mg l-1) of Cr6+. At the end of the 28 days, the worms were fixed in Zenkerfixative, washed, dehydrated, embedded in paraffin wax and the tissue sections taken at7 μmwere stained using hematoxylin-eosin. Histological alterations in the outer epithelium werethen recorded in detail.It was evident that Cr6+ induced alterations in the outer epithelium of the earthworm at all testlevels. A reduction in the thickness of the epithelium was noted (Control – 61.6 ± 6.1μm,0.02 mg l-1 – 28.0 ± 1.5 μm). Another observation was the reduction in the number of nuclei(Control – 31.3 ± 2.8, 0.02 mg l-1 - 7.4 ± 0.4) and the increase in the number of pyknoticnuclei in a given area of epithelial tissue (Control - 2.3 ± 0.4, 0.002 mg l-1 - 10.5 ± 1.0).Epithelial cells were neatly compacted with distinct cell margins in earthworms that were notexposed, whilst those exposed showed disintegration of cell margins even at 0.002 mg l-1 ofCr6+. Mucous cells, which are generally apparent, were not distinct in Cr6+ treated worms.Epithelial sloughing was more pronounced in treated earthworms than in the controls. Thespace between the epidermis and muscle layers were greater in treated worms than in thecontrols (Control - 0.7 ± 0.5 μm, 0.02 mg l-1 - 23.6 ± 1.0 μm). The muscle layers of the bodywall of the Cr6+ treated worms showed loss of structural integrity and increased intercellularspaces with the damage being more severe in those exposed to 20 mg l-1. This study providesevidence that histopathological alterations are possible in the earthworm at levels of Crrecorded in Sri Lanka’s natural ecosystems.

Dengue type 1 viruses circulating in humans are highly infectious and poorly neutralized by human antibodies

The four dengue virus (DENV) serotypes are mosquito-borne flaviviruses of humans. The interactions between DENVs and the human host that lead to asymptomatic, mild, or severe disease are poorly understood, in part, because laboratory models are poor surrogates for human DENV disease. Virologists are interested in how the properties of DENVs replicating in people compare with virions propagated on laboratory cell lines, which are widely used for research and vaccine development. Using clinical samples from a DENV type 1 epidemic in Sri Lanka and new ultrasensitive assays, we compared the properties of DENVs in human plasma and after one passage on laboratory cell lines. DENVs in plasma were 50- to 700-fold more infectious than cell culture-grown viruses. DENVs produced by laboratory cell lines were structurally immature and hypersensitive to neutralization by human antibodies compared with DENVs circulating in people. Human plasma and cell culture-derived virions had identical genome sequences, indicating that these phenotypic differences were due to the mature state of plasma virions. Several dengue vaccines are under development. Recent studies indicate that vaccine-induced antibodies that neutralized DENVs in cell culture assays were not sufficient for protecting people from DENV infections. Our results about structural differences between DENVs produced in humans versus cell lines may be key to understanding vaccine failure and developing better models for vaccine evaluation

Merozoite surface protein-3α is a reliable marker for population genetic analysis of Plasmodium vivax

BACKGROUND: The knowledge on population structure of the parasite isolates has contributed greatly to understanding the dynamics of the disease transmission for designing and evaluating malaria vaccines as well as for drug applications. msp-1 and msp-3α genes have been used as a genetic marker in population studies of Plasmodium vivax isolates. In this study, msp-3α was compared and assessed with msp-1 marker in order to find whether msp-3α is a reliable genetic marker for P. vivax population studies. METHODS: This comparative study was designed and carried out as the first assessment of diversity in Pvmsp-3α gene by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in the 50 northern and 94 southern P. vivax isolates from Iran, which had been analysed before for msp-1 gene. RESULTS: Three allele size as, Type A (1.8 kb), Type B (1.5 kb) and Type C (1.2 kb) have been detected among both northern and southern isolates based on PCR results. Type C (70%) and Type A (68.7%) were the predominant fragments among northern and southern parasites, respectively. 99 distinct Pvmsp-3α fragments defined by the size were detected in the 94 southern samples by PCR analysis. However, no mixed genotype infections have been detected among northern isolates. Based on restriction pattern from digestion with Hha I and Alu I 12 and 49 distinct allelic variants have been detected among 50 northern and 94 southern isolates. However, based on msp-1 gene, 30 distinct variants identified in all 146-sequenced Iranian P. vivax isolate. CONCLUSION: The results suggested that PCR-RFLP on msp-3α gene is an adequate, applicable and easily used technique for molecular epidemiology studies of P. vivax isolates without the need for further sequencing analysis

Immunity against sexual stage Plasmodium falciparum and Plasmodium vivax parasites.

The efficient spread of malaria from infected humans to mosquitoes is a major challenge for malaria elimination initiatives. Gametocytes are the only Plasmodium life stage infectious to mosquitoes. Here, we summarize evidence for naturally acquired anti-gametocyte immunity and the current state of transmission blocking vaccines (TBV). Although gametocytes are intra-erythrocytic when present in infected humans, developing Plasmodium falciparum gametocytes may express proteins on the surface of red blood cells that elicit immune responses in naturally exposed individuals. This immune response may reduce the burden of circulating gametocytes. For both P. falciparum and Plasmodium vivax, there is a solid evidence that antibodies against antigens present on the gametocyte surface, when co-ingested with gametocytes, can influence transmission to mosquitoes. Transmission reducing immunity, reducing the burden of infection in mosquitoes, is a well-acknowledged but poorly quantified phenomenon that forms the basis for the development of TBV. Transmission enhancing immunity, increasing the likelihood or intensity of transmission to mosquitoes, is more speculative in nature but is convincingly demonstrated for P. vivax. With the increased interest in malaria elimination, TBV and monoclonal antibodies have moved to the center stage of malaria vaccine development. Methodologies to prioritize and evaluate products are urgently needed

Parasite infectivity and immunity to Plasmodium falciparum gametocytes in Gambian children.

Immunity to the sexual stages of Plasmodium falciparum can be induced during natural infections. Characterization of this immunity may facilitate the design of a transmission-blocking vaccine (TBV). This study aimed to assess the prevalence and serological correlates of functional transmission-blocking immunity in Gambian children (aged 1-4 years old) who were P. falciparum gametocyte carriers. Serological assays showed 100% response to fixed, whole parasites but only 42% to live gametes. Responses to the antigens Pfs230 and Pfs48/45 were 54.1% and 37.3%, respectively, in an IgG1 ELISA. 14/55 sera were capable of reducing the infectivity of laboratory isolate NF54 in a standard membrane-feeding assay (SMFA). This activity was strongly correlated with IgG1 responses to Pfs48/45 (r = 0.49, P < 0.001) and to a serological reaction with epitopes of the same molecule (r = 0.38, P = 0.003). A weaker correlation was observed with IgG1 to Pfs230 (r = 0.29, P = 0.03). In direct membrane feeding assays (DMFA) with autologous isolates, sera from 4/29 children showed transmission-blocking activity. There was no correlation with serological assays and the DMFA or between the SMFA and DMFA. This may be caused by variation in sexual stage antigens and/or alternative modes of transmission-blocking immunity, both of which have implications for vaccine implementation