Single cell transcriptional changes across the blood stages of artemisinin resistant K13C580Y mutant Plasmodium falciparum upon dihydroartemisinin exposure

Artemisinins have been a cornerstone of malaria control, but resistance in Plasmodium falciparum, due to mutations in the Kelch 13 gene, threaten these advances. Artemisinin exposure results in a dynamic transcriptional response across multiple pathways, but most work has focused on ring stages and ex vivo transcriptional analysis, limiting evaluation of all life cycle stages. We applied single cell RNAseq to two unsynchronized isogenic parasite lines (K13C580 and K13580Y) over 6 hrs after a pulse exposure to dihydroartemisinin (DHA). Transcription was altered across all stages, with the greatest occurring at the early trophozoite and mid ring stage in both lines. This response involved the arrest of metabolic processes and the enhancement of protein trafficking and the unfolded protein response. While similar, the response was enhanced in the K13580Y mutant, which may lead to the dormancy phenomenon upon treatment. Increased surface protein expression was seen in mutant parasites at baseline and upon drug exposure, highlighted by the increased expression of PfEMP1 and GARP, a potential therapeutic target. Antibody targeting GARP maintained anti-parasitic efficacy in mutant parasites. This work provides single cell insight of gene transcription across all life cycle stages revealing transcriptional changes that could initiate dormancy state and mediate survival.

A newly characterized malaria antigen on erythrocyte and merozoite surfaces induces parasite inhibitory antibodies

We previously identified a Plasmodium falciparum (Pf) protein of unknown function encoded by a single-copy gene, PF3D7_1134300, as a target of antibodies in plasma of Tanzanian children in a whole-proteome differential screen. Here we characterize this protein as a blood-stage antigen that localizes to the surface membranes of both parasitized erythrocytes and merozoites, hence its designation as Pf erythrocyte membrane and merozoite antigen 1 (PfEMMA1). Mouse anti-PfEMMA1 antisera and affinity-purified human anti-PfEMMA1 antibodies inhibited growth of P. falciparum strains by up to 68% in growth inhibition assays. Following challenge with uniformly fatal Plasmodium berghei (Pb) ANKA, up to 40% of mice immunized with recombinant PbEMMA1 self-cured, and median survival of lethally infected mice was up to 2.6-fold longer than controls (21 vs. 8 d, P = 0.005). Furthermore, high levels of naturally acquired human anti-PfEMMA1 antibodies were associated with a 46% decrease in parasitemia over 2.5 yr of follow-up of Tanzanian children. Together, these findings suggest that antibodies to PfEMMA1 mediate protection against malaria.

Maternally-derived Antibodies to Schizont Egress Antigen-1 and Protection of Infants From Severe Malaria

BACKGROUND

In holoendemic areas, children suffer the most from Plasmodium falciparum malaria, yet newborns and young infants express a relative resistance to both infection and severe malarial disease (SM). This relative resistance has been ascribed to maternally-derived anti-parasite immunoglobulin G; however, the targets of these protective antibodies remain elusive.

METHODS

We enrolled 647 newborns at birth from a malaria-holoendemic region of Tanzania. We collected cord blood, measured antibodies to Plasmodium falciparum Schizont Egress Antigen-1 (PfSEA-1), and related these antibodies to the risk of severe malaria in the first year of life. In addition, we vaccinated female mice with PbSEA-1, mated them, and challenged their pups with P. berghei ANKA parasites to assess the impact of maternal PbSEA-1 vaccination on newborns' resistance to malaria.

RESULTS

Children with high cord-blood anti-PfSEA-1 antibody levels had 51.4% fewer cases of SM compared to individuals with lower anti-PfSEA-1 levels over 12 months of follow-up (P = .03). In 3 trials, pups born to PbSEA-1-vaccinated dams had significantly lower parasitemia and longer survival following a P. berghei challenge compared to pups born to control dams.

CONCLUSIONS

We demonstrate that maternally-derived, cord-blood anti-PfSEA-1 antibodies predict decreased risk of SM in infants and vaccination of mice with PbSEA-1 prior to pregnancy protects their offspring from lethal P. berghei challenge. These results identify, for the first time, a parasite-specific target of maternal antibodies that protect infants from SM and suggest that vaccination of pregnant women with PfSEA-1 may afford a survival advantage to their offspring.

Antibodies to PfsEGXP, an Early Gametocyte-Enriched Phosphoprotein, Predict Decreased Plasmodium falciparum Gametocyte Density in Humans

Background

Antigametocyte-specific immune responses may regulate Plasmodium falciparum gametocyte density, providing the rationale for pursuing transmission-blocking vaccines (TBVs) that target gametocytes in the human host.

Methods

To identify novel antigametocyte TBV antigens, we interrogated the gametocyte proteome with our whole proteome differential screening method using plasma from a treatment-reinfection study conducted in western Kenya. At the start of the high-transmission season, 144 males (12-35 years) were enrolled and treated with quinine and doxycycline, peripheral venous blood samples were obtained, volunteers were observed, and weekly blood films were obtained for 18 weeks to quantify gametocytemia. Using plasma pooled from individuals with low versus high gametocyte carriage, we differentially screened a P falciparum gametocyte stage complementary deoxyribonucleic acid expression library.

Results

We identified 8 parasite genes uniquely recognized by gametocyte-resistant but not by gametocyte-susceptible individuals. Antibodies to one of these antigens, PfsEGXP, predicted lower gametocytemia measured over the 18-week transmission season (P = .021). When analyzed dichotomously, anti-PfsEGXP responders had 31% lower gametocyte density over 18 weeks of follow-up, compared with nonresponders (P = .04).

Conclusions

PfsEGXP is one of the first reported gametocyte-specific target of antibodies that predict decreased gametocyte density in humans and supports our novel TBV antigen discovery platform.

Accurate light microscopic diagnosis of South-East Asian ovalocytosis

INTRODUCTION

South-East Asian ovalocytosis (SAO) is a common inherited red blood cell polymorphism in South-East Asian and Melanesian populations, coinciding with areas of malaria endemicity. Validation of light microscopy as a diagnostic alternative to molecular genotyping may allow for its cost-effective use either prospectively or retrospectively by analysis of archived blood smears.

METHODS

We assessed light microscopic diagnosis of SAO compared to standard PCR genotyping. Three trained microscopists each assessed the same 971 Giemsa-stained thin blood films for which SAO genotypic confirmation was available by PCR. Generalized mixed modeling was used to estimate the sensitivity, specificity, positive predictive value, and negative predictive value of light microscopy vs "gold standard" PCR.

RESULTS

Among red cell morphologic parameters evaluated, knizocytes, rather than ovalocytic morphology, proved the strongest predictor of SAO status (odds ratio [OR] = 19.2; 95% confidence interval [95% CI] = 14.6-25.3; P ≤ 0.0001). The diagnostic performance of a knizocyte-centric microscopic approach was microscopist dependent: two microscopists applied this approach with a sensitivity of 0.89 and a specificity of 0.93. Inter-rater reliability among the microscopists (κ = 0.20) as well as between gold standard and microscopist (κ = 0.36) underperformed due to misclassification of stomatocytes as knizocytes by one microscopist, but improved substantially when excluding the error-prone reader (κ = 0.65 and 0.74, respectively).

CONCLUSION

Light microscopic diagnosis of SAO by knizocyte visual cue performed comparable to time-consuming and costlier molecular methods, but requires specific training that includes successful differentiation of knizocytes from stomatocytes.

False-negative compatible antiglobulin crossmatches in samples with alloantibodies to cognate red blood cell antigens

BACKGROUND

Patient samples showing a positive indirect antiglobulin test are further tested to identify alloantibody specificity using a panel of phenotypically characterized group O reagent red blood cells (RBCs). Donor RBCs phenotypically negative for the antibody specificity are then serologically crossmatched using an antiglobulin reagent. This latter test is performed to identify any incompatibility due to the presence of undetected minor blood group antibodies and considered an important step in patient safety.

STUDY DESIGN AND METHODS

Samples with well-characterized alloantibodies were intentionally crossmatched against donor RBCs expressing the cognate antigen. In a separate set of specimens, the alloantibody was titered and crossmatched against both heterozygous and homozygous cells.

RESULTS

Thirty-five samples containing 10 common alloantibodies crossmatched against 240 ABO-compatible donor cells phenotypically positive for the cognate antigen showed compatible crossmatches in 89 of 240 (37%). Antibody titering of 12 alloantibodies showed that a titer of 2 or more was required for incompatibility of all homozygous cells and a titer of 8 or more for incompatibility of all heterozygous cells.

CONCLUSION

The antiglobulin crossmatch has a high failure rate (false-negatives) related to antibody titer and donor cell zygosity and is not reliable in interdicting incompatibility due to minor blood group antibodies.

How do we reduce plasma transfusion in Rhode Island?

BACKGROUND

Plasma transfusions are given to patients with coagulopathy, either prophylactically, before an invasive procedure; or therapeutically, in the presence of active bleeding; and as an exchange fluid in therapeutic plasma exchange for disorders such as thrombotic thrombocytopenic purpura. There is consensus that many prophylactic plasma transfusions are non-efficacious, and the misdiagnosis of thrombotic thrombocytopenic purpura results in unnecessary therapeutic plasma exchange.

STUDY DESIGN AND METHODS

Beginning in 2001, programs to reduce plasma transfusion in the three major teaching hospitals in Rhode Island were initiated. The programs evolved through the establishment of guidelines, education for key prescribers of plasma, screening of plasma prescriptions, and engagement of individual prescribing physicians for out-of-guidelines prescriptions with modification or cancellation. Establishment of an in-house ADAMTS13 (ADAM metallopeptidase with thrombospondin type 1, motif 13) assay in 2013 was used to prevent therapeutic plasma exchange in patients with non-thrombotic thrombocytopenic purpura microangiopathy. Transfusion service data were gathered at the hospital level regarding blood component use, hospital data for discharges, inpatient mortality, and mean case-mix index, and, at the state level, for units of plasma shipped from the community blood center to in-state hospitals.

RESULTS

Between 2006 and 2016, a reduction in plasma use from 11,805 to 2677 units (a 77% decrease) was observed in the three hospitals and was mirrored in the state as a whole. This decline was not associated with any increase in red blood cell transfusion. Inpatient mortality either declined or was unchanged.

CONCLUSION

An active program focused on education and interdiction can achieve a large decrease in plasma transfusions without evidence of patient harm.

Acquired Factor XIII inhibitor associated with mantle cell lymphoma

BACKGROUND

Acquired Factor (F)XIII deficiency is a very rare bleeding diathesis with a potentially fatal outcome, previously described in the context of autoimmune disorders and leukemias. There is minimal information on autoantibody characterization and the role of antifibrinolytic therapy in patient management.

CASE REPORT

A 79-year-old woman with a 3-month history of bruising and heavy menorrhagia presented with ongoing vaginal bleeding, symptomatic anemia, and a right thigh hematoma. Initial management included an axillary lymph node biopsy and coagulation evaluation. Pathologic examination of the biopsy specimen revealed mantle cell lymphoma. Clot solubility assay was consistent with a FXIII activity of less than 3%. An anti-FXIII inhibitor was suspected, the epitope specificity of which was mapped by micropeptide array analysis to regions in the β-sandwich and catalytic core domain of the FXIII-A subunit. Management with cryoprecipitate, steroids, rituximab, and antifibrinolytic therapy resolved the bleeding diathesis and suppressed the inhibitor.

CONCLUSION

This is the first reported case of an acquired FXIII inhibitor associated with mantle cell lymphoma in which the epitope specificity of the pathologic autoantibody was accurately defined. Antifibrinolytic therapy played a prominent role in the prevention of bleeding complications in the window period between initiation of immunosuppression and disappearance of the pathologic anti-FXIII autoantibody.

Autoimmune Cytopenias: Diagnosis & Management

The autoimmune cytopenias are a related group of disorders in which differentiated hematopoietic cells are destroyed by the immune system. Single lineage disease is characterized by the production of autoantibodies against red cells (autoimmune hemolytic anemia [AIHA]), platelets (autoimmune thrombocytopenia [ITP]) and neutrophils (autoimmune neutropenia [AIN]) whereas multilineage disease may include various combinations of these conditions. Central to the genesis of this disease is the breakdown of central and/or peripheral tolerance, and the subsequent production of autoantibodies by both tissue and circulating self-reactive B lymphocytes with support from T helper lymphocytes. These disorders are classified as primary (idiopathic) or secondary, the latter associated with an underlying malignancy, systemic autoimmune disease, infectious disease or a specific drug. Non-specific immunosuppression with corticosteroids remains the first-line therapy for many of these disorders, and although associated with high response rates, is compromised by significant toxicity and high relapse rates. Management of patients with chronic refractory autoimmune cytopenias who have failed first-line and second-line (cytotoxic immunosuppressant therapy and or splenectomy) is particularly complex, with definitive treatment in select patients requiring hematopoietic stem cell transplantation. Given the toxicity concerns of non-selective immunosuppressants, development of therapeutic regimens that avoid steroids has progressed rapidly in recent decades. [Full article available at http://rimed.org/rimedicaljournal-2016-12.asp].

Plasmodium falciparum gametocyte transit through the cutaneous microvasculature: A new target for malaria transmission blocking vaccines?

Malaria remains one of the most significant infectious diseases worldwide. Concordant with scaled intervention efforts and the emphasis of elimination and eradication on the agenda of many malaria control programs, the development of a malaria vaccine that reduces transmission of the parasite from human host to mosquito vector has been incorporated as an important new strategic goal. Transmission of malaria from man to mosquito relies on gametocytes, highly specialized sexual-stage parasites, that once mature, circulate in the peripheral vasculature of the human host. The complex interplay between mature gametocytes, their uptake in the mosquito bloodmeal and forward maturation/fertilization events provide unique opportunities for intervention. Although recent advances have yielded greater understanding into the mechanisms that mediate sequestration of immature gametocytes in the human host, the spatial dynamics of circulating mature gametocytes in the cutaneous microvaculature remains far less defined, which is the focus of this review.

Transfusion-transmitted anaplasmosis from a leukoreduced platelet pool

BACKGROUND

Human granulocytic anaplasmosis is an emerging tick-borne illness. Anaplasma phagocytophilum resides intracellularly, can cause asymptomatic infection, and can survive blood component refrigeration conditions for at least 18 days. To date, eight cases of transfusion-transmitted anaplasmosis (TTA) have been reported: seven attributed to red blood cell (RBC) units, five of which were prestorage leukoreduced using RBC leukoreduction filters, and one involving a process leukoreduced apheresis platelet (PLT) unit. Here, we report a case of TTA from a whole blood-derived PLT pool.

STUDY DESIGN AND METHODS

Donation segments from the 7 units of RBCs and two PLT pools transfused were examined. Fast protocol multiplex real-time A. phagocytophilum polymerase chain reaction (PCR) and serologic testing for immunoglobulin (Ig)M and IgG antibodies to A. phagocytophilum by enzyme immunoassay were performed.

RESULTS

Transmission was confirmed by positive A. phagocytophilum PCR and serology in one of 16 donors and by positive PCR and seroconversion in the recipient.

CONCLUSION

This is the first confirmed case of TTA from a whole blood-derived PLT pool prepared from PLT concentrates leukoreduced by in-line filtration of PLT-rich plasma.

Sulfamethoxazole-induced thrombocytopenia masquerading as posttransfusion purpura: a case report

BACKGROUND

Drug-induced immune thrombocytopenia (DITP) is a rare clinical disorder characterized by accelerated platelet (PLT) clearance in the presence of drug-dependent antibodies. Distinguishing DITP from other immune-mediated disorders such as posttransfusion purpura (PTP) and autoimmune thrombocytopenia can represent a clinical challenge.

CASE REPORT

A 68-year-old male with no prior transfusion history presented to the emergency department (ED) with dyspnea, epistaxis, and severe thrombocytopenia (<10 × 10(9)/L) 12 days after discharge from a hospital admission for a coronary artery bypass graft. Evaluation of the degree of thrombocytopenia and the temporal association between the peri- and postoperative receipt of multiple transfusions and the acute decrease in PLT count indicated PTP as a possible cause of the severe thrombocytopenia. Treatment with 1 g/kg intravenous immunoglobulin (IVIG) was initiated and followed by a rapid 48-hour increase in the PLT count. PLT antibodies lacking serologic specificity were subsequently identified in a sample collected upon presentation. Two weeks later he again presented to the ED with epistaxis and severe thrombocytopenia (<10 × 10(9)/L). Clinical history now revealed that the patient had been treated with trimethoprim-sulfamethoxazole by his primary care physician after his first hospitalization for a "cellulitic-appearing" leg and again before his final presentation for surgical site erythema and edema. IVIG was administered again with a rapid return of PLT count to baseline. Sulfamethoxazole-dependent PLT antibodies were subsequently identified in the original patient sample.

CONCLUSION

This case report documents a case of IVIG-responsive DITP initially misdiagnosed as PTP, highlighting the clinical overlap of these immunologic-mediated phenomena.

Distance to Anopheles sundaicus larval habitats dominant among risk factors for parasitemia in meso-endemic Southwest Sumba, Indonesia

BACKGROUND

The decline in intensity of malaria transmission in many areas now emphasizes greater importance of understanding the epidemiology of low to moderate transmission settings. Marked heterogeneity in infection risk within these populations creates opportunities to understand transmission and guide resource allocation to greater impact.

METHODS

In this study, we examined spatial patterns of malaria transmission in a hypo- to meso-endemic area of eastern Indonesia using malaria prevalence data collected from a cross-sectional socio-demographic and parasitological survey conducted from August to November 2010. An entomological survey performed in parallel, identified, mapped, and monitored local anopheline larval habitats.

RESULTS

A single spatial cluster of higher malaria prevalence was detected during the study period (relative risk=2.13; log likelihood ratio=20.7; P<0.001). In hierarchical multivariate regression models, risk of parasitemia was inversely correlated with distance to five Anopheles sundaicus known larval habitats [odds ratio (OR)=0.21; 95% confidence interval (CI)=0.14-0.32; P<0.001], which were located in a geographically restricted band adjacent to the coastline. Increasing distance from these sites predicted increased hemoglobin level across age strata after adjusting for confounders (OR=1.6; 95% CI=1.30-1.98; P<0.001).

CONCLUSION

Significant clustering of malaria parasitemia in close proximity to very specific and relatively few An. sundaicus larval habitats has direct implications for local control strategy, policy, and practice. These findings suggest that larval source management could achieve profound if not complete impact in this region.

Antibodies to PfSEA-1 block parasite egress from RBCs and protect against malaria infection

Novel vaccines are urgently needed to reduce the burden of severe malaria. Using a differential whole-proteome screening method, we identified Plasmodium falciparum schizont egress antigen-1 (PfSEA-1), a 244-kilodalton parasite antigen expressed in schizont-infected red blood cells (RBCs). Antibodies to PfSEA-1 decreased parasite replication by arresting schizont rupture, and conditional disruption of PfSEA-1 resulted in a profound parasite replication defect. Vaccination of mice with recombinant Plasmodium berghei PbSEA-1 significantly reduced parasitemia and delayed mortality after lethal challenge with the Plasmodium berghei strain ANKA. Tanzanian children with antibodies to recombinant PfSEA-1A (rPfSEA-1A) did not experience severe malaria, and Kenyan adolescents and adults with antibodies to rPfSEA-1A had significantly lower parasite densities than individuals without these antibodies. By blocking schizont egress, PfSEA-1 may synergize with other vaccines targeting hepatocyte and RBC invasion.

Antibodies to Rhoptry‐Associated Membrane Antigen Predict Resistance toPlasmodium falciparum

Previously, we collected plasma from 143 male volunteers residing in an area of western Kenya where Plasmodium falciparum is holoendemic. Volunteers were cured of current malaria infection by use of drugs, blood was collected 2 weeks after treatment, and blood films were collected weekly for 18 weeks. We identified and pooled plasma from the 10 most resistant individuals (RP) and the 7 most susceptible individuals (SP) and used these pools in a differential screen of a P. falciparum cDNA expression library. We screened 550,000 clones and identified 7 clones that were uniquely recognized by RP but not by SP. Two clones encoded a C-terminal region polypeptide from rhoptry-associated membrane antigen (RAMA-pr), a recently described RAMA. We measured anti-RAMA-pr antibody levels in plasma obtained 2 weeks after treatment. Individuals with detectable immunoglobulin G1 anti-RAMA-pr (n = 24) had fewer positive blood films (odds ratio, 1.7 [95% confidence interval, 1.21-2.44]; P < .003), 43% lower density of parasitemia (P < .02), and prolonged time to reinfection (P < .0027), compared with individuals without detectable antibody levels (n = 115), after known determinants of resistance were accounted for. In summary, RAMA-pr is a rationally identified vaccine candidate that is preferentially recognized by antibodies produced by humans with a high level of naturally acquired resistance to P. falciparum infection.

Protective human immunity as a vaccine discovery tool for falciparum malaria

BACKGROUND

Plasmodium falciparum malaria remains a leading cause of morbidity and mortality in developing countries, and malaria-associated severe anemia is the major factor driving the high transfusion requirements in pediatric populations living in endemic areas.

STUDY DESIGN AND METHODS

In this report, we identify and evaluate the targets of naturally acquired protective antibody responses in a cohort of n = 143 male volunteers residing in a P. falciparum holoendemic area of western Kenya. Volunteers were drug-cured of current malaria infection, blood was collected 2 weeks after treatment, and blood smears were collected weekly for 18 weeks. We identified and pooled plasma from the 10 most resistant (RP) and the 7 most susceptible individuals (SP) and utilized these pools in a differential screen of a P. falciparum cDNA expression library. We screened 550,000 clones and identified 7 clones that were uniquely recognized by RP but not by SP. Two clones encoded a C-terminal region polypeptide from rhoptry-associated membrane antigen (RAMA-pr), a recently described rhoptry-associated membrane antigen.

RESULTS

We measured RAMA-pr antibody levels in plasma obtained 2 weeks after treatment. Individuals with detectable immunoglobulin G(1) anti-RAMA-pr (n = 24) had fewer positive blood films (p < 0.003) and 43 percent lower density of parasitemia (p < 0.02) than individuals with undetectable (n = 115) antibody levels.

CONCLUSION

RAMA-pr is a rationally identified vaccine candidate preferentially recognized by antibodies produced by humans with a high level of naturally acquired resistance to P. falciparum infection. Our results demonstrate that naturally acquired protective antibody responses are useful tools to identify vaccine candidates for falciparum malaria.

Expression, purification, and human antibody response to a 67 kDa vaccine candidate for schistosomiasis japonica

Schistosomiasis remains a leading cause of morbidity and mortality in the developing tropical world, and vaccines to prevent these infections remain a scientific and public health priority. Sj67 is a 67 kDa Schistosoma japonicum surface membrane protein homologous to a family of actin-binding proteins. Sj67 is recognized by a mouse monoclonal antibody (mAb 6) that confers resistance to challenge infection in passive transfer experiments. These data support Sj67 as a potential vaccine candidate for schistosomiasis japonica. In the present study, we report the ligation-independent cloning of a cDNA encoding thioredoxin/elastin-like polypeptide (ELP)/rSj67 into a pET-32 Xa/LIC vector. Soluble recombinant fusion protein (Thio-ELP-rSj67) was expressed and purified using anion-exchange and size exclusion chromatography. rSj67 was cleaved from the Thio-ELP fusion partner by digestion with Factor Xa protease and purified using hydroxyapatite column chromatography. Endotoxin was reduced by absorption to a polymyxin support. Purified rSj67 had a molecular weight of 67 kDa and N-terminal sequencing confirmed that the first five amino acids of the recombinant protein matched the predicted sequence for the Sj67 gene. In Western blot analysis, rSj67 was recognized by the Sj67 specific mAb 6 antibody. IgG antibodies in sera from schistosomiasis infected volunteers living in an endemic area of the Philippines (n = 13) recognized rSj67 with 4.7-fold greater median fluorescence compared to uninfected North American controls (n = 5) (p < 0.009). Together, these data confirm the expression and purification of recombinant Sj67 and its immuno-reactivity with sera from S. japonicum infected humans.

Dehydroepiandrosterone sulfate levels associated with decreased malaria parasite density and increased hemoglobin concentration in pubertal girls from western Kenya

In areas where Plasmodium falciparum malaria is endemic, parasite density, morbidity, and mortality decrease with increasing age, which supports the view that years of cumulative exposure are necessary for the expression of maximal protective immunity. Developmental changes in the host also have been implicated in the expression of maximal resistance. To further evaluate the contribution of host developmental factors in malaria resistance, we examined the relationship between P. falciparum parasitemia and pubertal development in a cross-sectional sample of 12-18-year-old schoolgirls from an area of intense transmission in western Kenya. Among pubertal girls, dehydroepiandrosterone sulfate (DHEAS) levels were significantly associated with decreased parasite density, even after adjustment for age. DHEAS levels also were related to increased hemoglobin levels, even after accounting for age and other determinants of hemoglobin level. These findings support the hypothesis that host pubertal development, independent of age and, by proxy, cumulative exposure, is necessary for maximal expression of resistance to malarial infection and morbidity, as assessed by hemoglobin level.

Elevated tumor necrosis factor-alpha activation of human immunodeficiency virus type 1 subtype C in Southern Africa is associated with an NF-kappaB enhancer gain-of-function

The human immunodeficiency virus type 1 (HIV-1) epidemic within southern Africa is predominantly associated with the HIV-1C subtype. Functional analysis of the enhancer region within the long terminal repeat (LTR) indicates that HIV-1C isolates have >/=3 NF-kappaB binding sites, unlike other subtypes, which have only 1 or 2 sites. A correlation was shown between NF-kappaB enhancer configuration and responsiveness to the proinflammatory cytokine tumor necrosis factor (TNF)-alpha within the context of naturally occurring subtype LTRs, subtype-specific NF-kappaB enhancer regions cloned upstream of an isogenic HXB2 core promoter or a heterologous SV40 minimal promoter, and full-genome subtype clones. In all cases, TNF-alpha activation was correlated with the subtype configuration of the NF-kappaB enhancer. Whether the naturally occurring gain-of-function in the NF-kappaB enhancer of HIV-1C observed in this study can provide a selective advantage for the virus in vivo remains to be determined and warrants further study.

Dysregulation through the NF-kappaB enhancer and TATA box of the human immunodeficiency virus type 1 subtype E promoter

The global diversity of human immunodeficiency virus type 1 (HIV-1) genotypes, termed subtypes A to J, is considerable and growing. However, relatively few studies have provided evidence for an associated phenotypic divergence. Recently, we demonstrated subtype-specific functional differences within the long terminal repeat (LTR) region of expanding subtypes (M. A. Montano, V. A. Novitsky, J. T. Blackard, N. L. Cho, D. A. Katzenstein, and M. Essex, J. Virol. 71:8657-8665, 1997). Notably, all HIV-1E isolates were observed to contain a defective upstream NF-kappaB site and a unique TATA-TAR region. In this study, we demonstrate that tumor necrosis factor alpha (TNF-alpha) stimulation of the HIV-1E LTR was also impaired, consistent with a defective upstream NF-kappaB site. Furthermore, repair of the upstream NF-kappaB site within HIV-1E partially restored TNF-alpha responsiveness. We also show, in gel shift assays, that oligonucleotides spanning the HIV-1E TATA box displayed a reduced efficiency in the assembly of the TBP-TFIIB-TATA complex, relative to an HIV-1B TATA oligonucleotide. In transfection assays, the HIV-1E TATA, when changed to the canonical HIV-1B TATA sequence (ATAAAA-->ATATAA) unexpectedly reduces both heterologous HIV-1B Tat and cognate HIV-1E Tat activation of an HIV-1E LTR-driven reporter gene. However, Tat activation, irrespective of subtype, could be rescued by introducing a cognate HIV-1B TAR. Collectively, these observations suggest that the expanding HIV-1E genotype has likely evolved an alternative promoter configuration with altered NF-kappaB and TATA regulatory signals in contradistinction with HIV-1B.