Evaluation of the antimalarial and CD4+ T-cell modulatory effects of leaf methanol extract of Phyllanthus muellerianus (Kuntze) Exell (Phyllanthaceae) in Plasmodium berghei-infected mice

ETHNOPHARMACOLOGICAL RELEVANCE

Phyllanthus muellerianus (Kunze) Exell, a member of the Phyllanthaceae family, is a medicinal plant widely distributed in Africa. Decoctions from the leaves are used in Nigeria to treat fevers, convulsions, some neurological disorders and malaria.

AIM OF THE STUDY

This study is to evaluate the anti-malarial properties of methanol extract of Phyllanthus muellerianus (MEPM) leaves and its ethyl acetate fraction using a murine malaria model infected with Plasmodium berghei. Additionally, we seek to investigate the potential modulatory effects of this extract and fraction on CD4+ T-cell populations in the context of malaria infection.

MATERIALS AND METHODS

The anti-malarial effects of the leaf methanol extract of Phyllanthus muellerianus (MEPM) were screened using three established in vivo models of anti-plasmodial screening namely the curative, suppressive and prophylactic models. The methanol extract (MEPM) was afterwards fractionated into hexane (HFPM), ethyl acetate (EAFPM), and methanol (MFPM) fractions. In the pilot anti-malarial screening of the fractions, EAFPM exhibited the best antiparasitic activity. Subsequently, EAFPM was screened for anti-malarial activity using the three models above. The effects of the MEPM and EAFPM on haematological indices (Hb and PCV) of the inoculated animals were further screened and the mean survival time (MST) of the animals was monitored. CD4+ T cells of various groups were counted before and after treatment using a flow cytometer. The EAFPM was further subjected to HPLC analysis for identification of its major compounds.

RESULTS

The EAFPM (100 and 200 mg/kg) elicited 88% and 93% cure respectively in the curative model, while artesunate (5 mg/kg,- the positive control) gave 87% protection. The MEPM and EAFPM also gave significant suppression of parasitemia in the suppressive model. The treated groups survived beyond 28 days as against 11 days by the control group (infected but not treated). The treated groups also prevented anaemia seen in the negative control. The EAFPM group significantly modulated the CD4+ T cell. Compounds identified were Gallocatechin, Quercetin -3-O-gallate, Ellagic acid, and Methylellagic acid rhamnoside).

CONCLUSION

The study established that the leaf of Phyllanthus muellerianus possesses antimalarial activity, thus lending support to its use in the folkloric treatment of malaria.

Diverse functions of myeloid-derived suppressor cells in autoimmune diseases

Since myeloid-derived suppressor cells (MDSCs) were found suppressing immune responses in cancer and other pathological conditions, subsequent researchers have pinned their hopes on the suppressive function against immune damage in autoimmune diseases. However, recent studies have found key distinctions of MDSC immune effects in cancer and autoimmunity. These include not only suppression and immune tolerance, but MDSCs also possess pro-inflammatory effects and exacerbate immune disorders during autoimmunity, while promoting T cell proliferation, inducing Th17 cell differentiation, releasing pro-inflammatory cytokines, and causing direct tissue damage. Additionally, MDSCs could interact with surrounding cells to directly cause tissue damage or repair, sometimes even as an inflammatory indicator in line with disease severity. These diverse manifestations could be partially attributed to the heterogeneity of MDSCs, but not all. The different disease types, disease states, and cytokine profiles alter the diverse phenotypes and functions of MDSCs, thus leading to the impairment or obversion of MDSC suppression. In this review, we summarize the functions of MDSCs in several autoimmune diseases and attempt to elucidate the mechanisms behind their actions.

Evaluation of in vivo anti-malarial potential of omidun obtained from fermented maize in Ibadan, Nigeria

BACKGROUND

The menace of resistance to anti-malarial drugs is a great challenge to malaria control, necessitating the search for new anti-malarial agents. This search has led to the exploration of natural products for efficacy in malaria therapy. Omidun is the supernatant of fermenting maize (ogi) slurry that has been widely investigated and reported to possess several health benefits and it is used traditionally as solvent for preparing anti-malarial herbs. However, there is no information on the anti-malarial activity of omidun itself. This study was conducted to investigate the prophylactic, curative and suppressive anti-malarial potential of omidun.

METHODS

Experimental mice in the curative group were infected with 1 × 106 cells of Plasmodium berghei strain ANKA and treated with either 0.2 ml of omidun containing 3 × 109 cfu/ml of viable lactic acid bacteria or 0.2 ml of 5 mg/kg of chloroquine (positive control) or 0.2 ml of saline (negative control) for 4 days from day 3 post infection. The prophylactic group of mice were pre-treated with either omidun, chloroquine or saline for 4 days before infection with P. berghei, while the suppressive group was treated with omidun or chloroquine or saline and infected with P. berghei simultaneously. A group of mice were uninfected but treated (with omidun and control samples), while a final group was uninfected and untreated (controls). Parasitaemia and histopathology analysis were done in all groups.

RESULTS

The curative and suppressive groups showed a significant difference between the omidun-treated mice (100% parasitaemia reduction) and the untreated mice (54.5% parasitaemia increase). There was no significance difference between the omidun treatment and chloroquine (positive control) treatment in suppressive group as both treatment had 100% parasitaemia reduction. The omidun prophylactic treatment however did not show any parasitaemia suppression, but a significant difference was observed between the omidun treatment (85% increase) and the chloroquine (positive control) treatment (100% reduction) in the group. Omidun treatment is non-toxic to the kidney.

CONCLUSION

This study provides scientific evidence supporting omidun usage in the treatment of malaria. Consequently, further work may yield the specific component of omidun responsible for the anti-malarial activity.

Investigation of pre-clinical pharmacokinetic parameters of atovaquone nanosuspension prepared using a pH-based precipitation method and its pharmacodynamic properties in a novel artemisinin combination

OBJECTIVES

Recently, a growing resistance to antimalarial drugs such as chloroquine, sulfadoxine-pyrimethamine, artemisinin derivatives and mefloquine has been observed. The pharmacokinetic limitation of the current therapy and multi-drug resistance has resulted in an urgent need to study the new antimalarial combinations with existing drugs. This study investigated the activity of a novel triple combination of atovaquone (nanosized)-proguanil-artesunate as an alternative artemisinin combination therapy. Atovaquone in this combination was formulated as a freeze-dried nanosuspension and its pharmacokinetic parameters were also evaluated.

METHODS

The suppressive and curative effect of atovaquone nanosuspension, proguanil, and artesunate were studied in a murine model. The in vivo pharmacokinetics of the newly developed atovaquone nanosuspension with particle size less than 200 nm was investigated.

RESULTS

Prophylactic efficacy of atovaquone nanosuspension alone at 1/80th the therapeutic dose was proven. In the curative test, atovaquone nanosuspension and proguanil at 1/10th the therapeutic dose was the minimum effective dose that resulted in complete cure of parasitaemia. As a triple combination, atovaquone nanosuspension in combination with proguanil at 1/80th the therapeutic dose of each and 1/5th the therapeutic dose of artesunate resulted in a complete cure. The in vivo pharmacokinetics of the nanosuspension showed a significant (three times) reduction in T_max value and the area under the curve of the nanosuspension was 1.9 times greater as compared with the plain suspension.

CONCLUSIONS

The potential of the synergistic combination of atovaquone nanosuspension-proguanil-artesunate in curing the multi-drug resistant malarial infection at reduced doses of all three drugs could be a solution to pill burden observed with the current therapy.

Regulatory functions of γδ T cells

γδ T cells share characteristics of innate and adaptive immune cells and are involved in a broad spectrum of pro-inflammatory functions. Nonetheless, there is accumulating evidence that γδ T cells also exhibit regulatory functions. In this review, we describe the different phenotypes of regulatory γδ T cells in correlation with the identified mechanisms of suppression.

A New Method for Post-introduction Risk Assessment of Biological Invasions Among Introduced Shrubs in Developing Countries

Risk-assessment methods are useful in collecting data that can help decision making to prevent the introduction of new species that have the potential of invading as well as in management of established taxa. Not only the complexity and unaffordability of available pre-introduction risk-assessment models make them rarely or inconsistently applied in the least-developed countries, but also there is lack of tools to assess the status of already introduced plant species. In this study, an affordable and rapid method of assessment of invasiveness among introduced plant species was developed and tested in Rwanda. This method defines three invasion stages (potential, effective, and suppressive invaders) and four levels of risk assessment: post-introduction assessment of species inherent invasive potential (Level 1), post-establishment assessment of species capacity of regeneration (Level 2), post-naturalization assessment of species range of occurrence and ability for long-distance dispersal (Level 3), and post-naturalization assessment of species ability to outcompete other plants in the community and transform the landscape (Level 4). A review of invasive species in Rwanda was developed through desk review, examination of herbarium records, and vegetation surveys. This method should be applicable in other countries that lack the means for a more conventional scientific investigation or under any circumstance where a quick and inexpensive assessment is needed. The method could be useful to environmental managers for timely intervention with strategies specific to different stages of invasion (post-introduction, post-establishment, or post-naturalization) and allocate resources accordingly.

Avian CD4(+)CD25(+) regulatory T cells: properties and therapeutic applications

Regulatory T cells (Tregs) are a subset of T cells that specialize in immune suppression. CD4(+)CD25(+)FoxP3(+) T cells have been characterized as Tregs and extensively studied in mammals. In the absence of a putative FoxP3 ortholog in avians, CD4(+)CD25(+) cells is characterized as Tregs in avians. Avian CD4(+)CD25(+) cells produce high amounts of IL-10, TGF-β, CTLA-4, and LAG-3 mRNA; lack IL-2 mRNA; and suppress T cell proliferation in vitro through both contact-dependent and -independent pathways. Depleting avian CD4(+)CD25(+) cells increases the proliferation of, IL-2 amount, and IFNγ mRNA amount of CD4(+)CD25(-) cells. Avian CD4(+)CD25(+) cells lose their suppressive properties immediately after inflammation and acquire supersuppressive properties once inflammation subsides. Although Treg activity could be beneficial to the host, Tregs simultaneously inhibit host immunity and cause persistent infections of certain pathogens. Therapy targeted toward alleviating Treg mediated immune suppression can improve host immunity against those persistent pathogens and benefit poultry production.