CD47 regulates the phagocytic clearance and replication of the Plasmodium yoelii malaria parasite

Several Plasmodium species exhibit a strong age-based preference for the red blood cells (RBC) they infect, which in turn is a major determinant of disease severity and pathogenesis. The molecular basis underlying this age constraint on the use of RBC and its influence on parasite burden is poorly understood. CD47 is a marker of self on most cells, including RBC, which, in conjunction with signal regulatory protein alpha (expressed on macrophages), prevents the clearance of cells by the immune system. In this report, we have investigated the role of CD47 on the growth and survival of nonlethal Plasmodium yoelii 17XNL (PyNL) malaria in C57BL/6 mice. By using a quantitative biotin-labeling procedure and a GFP-expressing parasite, we demonstrate that PyNL parasites preferentially infect high levels of CD47 (CD47^hi)-expressing young RBC. Importantly, C57BL/6 CD47^−/− mice were highly resistant to PyNL infection and developed a 9.3-fold lower peak parasitemia than their wild-type (WT) counterparts. The enhanced resistance to malaria observed in CD47^−/− mice was associated with a higher percentage of splenic F4/80⁺ cells, and these cells had a higher percentage of phagocytized parasitized RBC than infected WT mice during the acute phase of infection, when parasitemia was rapidly rising. Furthermore, injection of CD47-neutralizing antibody caused a significant reduction in parasite burden in WT C57BL/6 mice. Together, these results strongly suggest that CD47^hi young RBC may provide a shield to the malaria parasite from clearance by the phagocytic cells, which may be an immune escape mechanism used by Plasmodium parasites that preferentially infect young RBC.Malaria, caused by Plasmodium parasites, remains a major cause of mortality and morbidity in the developing world. Among the four principal human Plasmodium species, Plasmodium falciparum is the most virulent, being responsible for more than 90% of malaria-associated deaths. Likewise, Plasmodium species that infect rodents and nonhuman primates also differ widely in their fulminant nature and in the mortality they cause (1–3). How different Plasmodium species have evolved to exhibit this wide array of virulence and disease severity remains one of the major unsolved questions in malaria biology and pathogenesis.One important factor that is associated with Plasmodium parasite burden and disease severity is the age constraint of the host red blood cells (RBC) they infect. The age-based preference for restricted invasion of RBC by the Plasmodium parasite is characterized as young RBC (reticulocyte), aged RBC (mature), or both young and aged RBC. Plasmodium species that preferentially infect and grow inside young RBC generally cause a low-grade, self-resolving infection that is rarely fatal (e.g., Plasmodium vivax and Plasmodium ovale), whereas those that infect both young and aged RBC cause more fulminant infection that can be fatal in the absence of immunity (e.g., P. falciparum) (1, 4–6). Thus, along with host genetic background and immune response, restriction for age-specific RBC invasion is a major determinant of the severity and outcome of malaria infection.Malaria parasites have evolved to use redundant receptors and pathways to invade the RBC. For example, sialic acid (7) and Duffy antigen (8) are the major RBC receptors for invasion of P. falciparum and P. vivax, respectively, although other receptors and invasion pathways are known to exist (9, 10). Although a redundancy in RBC receptor use would ensure successful invasion by mitigating the effects of polymorphism and immune targeting, the reasons behind the RBC age-based preference for invasion are not fully clear and remain a subject of debate.Survival of normal cells through the course of their life cycle is essential to maintain homeostasis, and aberrant cells (e.g., senescent or foreign antigen-expressing cells) are eliminated through a sophisticated programmed cell removal system that relies on the recognition of self and nonself determinants (11). CD47, a cell surface molecule in the Ig superfamily, is ubiquitously expressed on many cell types, including RBC, and is a marker of self to avoid early clearance by phagocytic cells through ligation of signal regulatory protein alpha (12). In contrast, altered expression or conformational changes in CD47 may lead to a molecular switch that triggers a phagocytic signal to remove aged or damaged cells (11). Recent studies have shown that the level of CD47 expression is higher in progenitor cells and declines as they undergo maturation and are subsequently aged (13). This age-dependent difference in CD47 expression shields young cells but allows clearance of aging and damaged cells from the system.CD47 is overexpressed in cancer cells (11, 14, 15), and the CD47–signal regulatory protein alpha interaction is considered a major pathway of immune evasion by tumor cells (15). Administration of anti-CD47 antibodies enabled the phagocytosis of tumor cells in vitro, reduced their growth, and prevented the metastasis of human patient tumor cells (14). In this article, using the murine Plasmodium yoelii nonlethal model, we provide quantitative evidence for age of RBC as the basis for the survival and growth of malaria parasites and provide supporting data that suggest that P. yoelii nonlethal parasites prefer to grow inside younger RBC, which allows them to evade immune clearance by phagocytic cells through a CD47-mediated process, and that CD47 modulates the clearance of malaria infection. To our knowledge, this is the first report that provides a molecular basis for the age-dependent preference for infection of RBC by a Plasmodium parasite and sheds light on its implications for the severity of malaria infection in a host.     

Surgical Management of Resistant Priapism

We report a 31 year old patient, presented with painful erection since 48 hours. There was no known predisposing factor on history and examination. Surgery for priapism is rarely indicated nowadays but conservative management failed to achieve detumescence in our case. So Winter’s shunt surgery was done which failed then a formal shunt was created between corpora cavernosa and spongiosum which also failed to achieve detumescence. After 4 days - a formal left side cavernosa saphenous shunt procedure was done and detumescence achieved within 24 hrs .Follow up showed good results.     

Hemorrhagic liver cyst

INTRODUCTION: Simple cysts of the liver are usually discovered incidentally on abdominal imaging, and asymptomatic simple cysts do not require treatment regardless of size. DISCUSSION: We report a case of a symptomatic simple cyst of the liver complicated by intracystic hemorrhage for which a partial hepatectomy was performed. Treatment of simple hepatic cysts is indicated in the presence of associated symptoms or complications, and inability to exclude a cystic neoplasm requires operative intervention.     

Multidrug resistance of Pseudomonas aeruginosa as known from surveillance of nosocomial and community infections in an Indian teaching hospital

Aim

The aim of the present study was to record nosocomial and community-acquired accounts of antibiotic resistance in Pseudomonas aeruginosa strains, isolated from clinical samples of a hospital by surveillance, over a period of 18?months (November 2009–April 2011).

Subject and Methods

Clinical samples from nosocomial sources, i.e. wards and cabins and intensive care unit (ICU) and neonatal intensive care unit (NICU) sources, and community (outpatient department, OPD) sources of a hospital were used for isolating strains of P. aeruginosa.

Results

Of 368 isolated strains of P. aeruginosa, a total of 201 (54.62%) strains were from nosocomial and 167 (45.38%) strains were from community samples. There were 42 (25.14%) extended spectrum β-lactamase (ESβL) strains among the 167 isolates from the community samples. And from wards and cabins, there were 29 (23%) ESβL strains among the 126 isolates. Of the 75 isolates from ICU and NICU, there were 25 (33.33%) ESβL strains; the total of nosocomial ESβL strains was 54 (26.86%) in this study from the total of 201 P. aeruginosa isolates. In a computation of the χ² test of independence for assessing incidences of ESβL strains among all multidrug-resistant (MDR) strains, it was inferred that ESβL strains were equally distributed in wards and cabins, ICU and NICU or community, similar to the rest of the other MDR P. aeruginosa strains. Fifteen antibiotics were used for assessing antibiotic sensitivity of all isolated P. aeruginosa strains and a progressive increase of percent values of drug resistance was recorded.

Conclusion

This study on surveillance of a hospital revealed the daunting state of occurrence of MDR P. aeruginosa. A progressive increase of percent values of drug resistance to 15 antibiotics used for antibiotic sensitivity of P. aeruginosa strains was recorded.     

High performance liquid chromatography determination of dexamethasone in plasma to evaluate its systemic absorption following intra-space pterygomandibular injection of twin-mix (mixture of 2 % lignocaine with 1:200,000 epinephrine and 4 mg dexamethasone): randomized control trial

Purpose

To determine systemic absorption of dexamethasone by detection of plasma concentration using high performance liquid chromatography following its administration along with local anesthetic agent as a mixture via pterygomandibular space.

Methods

A prospective randomized double-blind clinical study was undertaken to analyze the plasma concentration of dexamethasone after intra-space pterygomandibular injection along with local anesthesia. The study was performed as per split mouth model where the mandibular quadrant allocation was done on a random basis considering each of the 30 patients is included in the two study interventions (SS and CS). For the study site (SS) procedures, dexamethasone was administered as a mixture (2 % lignocaine with 1:200,000 epinephrine and 4 mg dexamethasone) intra-space. In the control site (CS) procedures, a regular standard inferior alveolar nerve block was administered, and dexamethasone was given as intramuscular injection. The plasma dexamethasone determination was done in venous blood 30- and 60-min post injection using high performance liquid chromatography (HPLC). The clinical parameters like pain; swelling; and mouth opening on the first, third, and seventh post-operative day were analyzed and compared.

Results

No significant difference was found in the clinical parameters assessed; comparative evaluation showed less swelling in the SS interventions. The plasma concentration of dexamethasone for the CS interventions was 226?±?47 ng/ml at 30-min and 316?±?81.6 ng/ml at 60-min post injection, and for SS, it was 221?±?81.6 ng/ml at 30-min and 340?±?105 ng/ml at 60-min post injection. On inter-site (CS and SS) comparison, no statistically significant difference was ascertained in dexamethasone plasma concentration at 30-min post injection (P?=?0.77) and at 60-min post injection. (P?=?0.32).

Conclusion

Intra-space (pterygomandibular space) administration of dexamethasone can achieve statistically similar plasma concentration of the drug as when the same dose is administered intramuscularly with demonstration of similar clinical effects.

     

Redox titration of fluorescence yield of photosystem II

The variable fluorescence yield of photosystem II is dependent on the redox state of the fluorescence quencher molecule or the primary electron acceptor of the system. We have carried out redox titrations of fluorescence yield of a photochemically active photosystem-II reaction-center particle and have measured the redox potential of the photosystem-II primary acceptor.     

Source of retreatment cases under the revised national TB control programme in Rajasthan, India, 2003.

BACKGROUND: Three years after state-wide DOTS coverage and achievement of global targets for detection and cure, the proportion of sputum-positive retreatment cases remained high in the north Indian state of Rajasthan. AIM: To determine source, accuracy of categorisation and treatment outcomes in Category II sputum-positive retreatment cases registered from January to March 2003 in five districts of Rajasthan. MATERIAL AND METHODS: Two hundred consecutive Category II sputum-positive retreatment cases were identified from the tuberculosis register and interviewed using a semi-structured questionnaire. RESULTS: Categorisation was correct in 195 (97.5%) of retreatment cases interviewed. Treatment after default (TAD) comprised 84.6% (165/195) of interviewees, with 13.3% (n = 26) relapses and 2.1% (n = 4) failure cases. Of the TAD cases, 84.8% (n = 140) had defaulted from previous treatment in the private sector. Only 6.1% (n = 10) had defaulted from Category II DOTS treatment. The most unfavourable treatment outcome seen amongst interviewees was default, as also described in the national data. CONCLUSION: TADs constituted the majority of interviewed retreatment cases (84.6%), and were overwhelmingly being generated by irregular treatment in the private sector. Further involvement of the private sector in the DOTS programme in Rajasthan is needed to stop the creation of further retreatment cases.     

Impact of alphacypermethrin treated bed nets on malaria in villages of Malkangiri district, Orissa, India

The impact of use of bed-nets treated with alphacypermethrin, at 20 mg (ai)/m2, in comparison to untreated nets or no nets on malaria vectors and malaria incidence was studied in tribal villages of Malkangiri district, Orissa state, India, which are highly endemic for falciparum malaria. Treated or untreated nets were supplied to the villagers in June 1999 and the nets were re-treated in September 1999, just before the rise in vector abundance and malaria incidence. The seasonal pattern of indoor resting Anopheles fluviatilis females was similar in all the three groups of villages before the start of intervention and the indoor resting catches were not significantly different between treatment-groups (two-way ANOVA, F = 1.53; d.f. = (2, 78); P = 0.2). During intervention, the indoor resting catches differed significantly among treatment groups (two-way ANOVA, F = 38.9; d.f.= (2, 66); P < 0.005). There was a 99% reduction in the indoor resting catches of An. fluviatilis in villages with treated nets and 61% reduction in villages with untreated nets compared with no-net villages. Comparison between villages with and without treated nets showed that there was 97% reduction in indoor resting catches in villages with treated nets. Pair-wise comparison showed that the reductions between villages with and without nets as well as between villages with treated and untreated nets were significant (Dunnett's C-test, P < 0.05). The indoor resting catches of Anopheles culicifacies did not differ significantly among the three groups of villages either before (F = 0.99; d.f. = (2, 121); P = 0.4) or during intervention (F = 0.21; d.f. = (2, 66); P = 0.8). Bioassay with 3 min exposure to treated bed nets showed 100% mortality of An. culicifacies for 2 months and with An. fluviatilis for 4.5 months after which tests were not carried out. In villages with treated nets, the Annual Parasite Incidence (API) significantly declined (P < 0.05) by about 65.7% and prevalence of infection among children (< 15 years) declined by 57.1%, whereas in villages with untreated nets, there was only 34% reduction in API and 13% in the prevalence of infection. In villages with treated nets, there was 48% reduction in API and 64% in prevalence of infection compared with villages with untreated nets. The impact of use of treated bed nets on other arthropod pests lasted for at least 1.5 months. After 1.5 months, observations on arthropod pests were not continued. The use rate of treated nets varied from 49.8 to 93.7% in three seasons and about 68.3% of treated bed nets and 60% of untreated nets were in good condition 1 year after distribution. Out of 489 users of treated net, five people complained of a burning sensation on the face (skin irritation) for 5 days following the distribution of treated nets. There were no other complaints of any discomfort in using the treated nets. The use of alphacypermethrin treated bed nets at 20 mg (ai)/m2 can be one of the options for reducing the vector abundance and incidence of malaria in this area.