Improved Quality of Life Among Chronic Pancreatitis Patients Undergoing Total Pancreatectomy With Islet Autotransplantation-Single Center Experience With Large Cohort of Patients

Total pancreatectomy with islet autotransplantation (TPIAT) is the treatment of choice to preserve pancreatic endocrine function, alleviate pain, and improve quality of life (QoL) when other strategies are ineffective for chronic pancreatitis (CP) patients. This study utilized pancreatic disease-specific surveys developed by the European Organisation for Research and Treatment of Cancer (EORTC) to conduct a comprehensive, single-center examination of a large cohort of patients to gain understanding of QoL post-TPIAT. Two validated QoL surveys of the EORTC-QLQ-C30 and QLQ-PAN26-were administered in a prospective cohort of CP patients during pre-and post-operative scheduled visits. A total of 116 patients responded to the preoperative survey and were included in this study. The global health scale of QLQ-C30 was significantly improved after TPIAT when compared to baseline with delta scores of 24.26, 20.54, and 26.7 at 1, 2, and 3 years post-TPIAT (p < 0.001). The EORTC-PAN26 revealed significant improvements in symptom scales for pancreatic pain, bloating, digestive symptoms, taste, indigestion, weight loss, body image, and future worries. The comprehensive surveys in such a large cohort expands the QoL criterion in CP patients and indicates significant improvement in QoL post-TPIAT, further validating TPIAT as a treatment option for refractory CP.

Spleen-preserving total pancreatectomy and islet autotransplantation with complete preservation of the splenic arterial and venous supply does not impact islet yield and function

BACKGROUND

Standard total pancreatectomy and islet autotransplantation (TPIAT) for chronic pancreatitis includes splenectomy, but TPIAT can be performed without splenectomy by full preservation of the blood supply to the spleen.

METHODS

We compared the metabolic and clinical outcomes of patients who underwent TPIAT at our center between 2015 and 2021 with or without splenectomy. A total of 89 patients were included in the study, and 17 of them underwent spleen-preserving total pancreatectomy (SPTP).

RESULTS

The two study groups had similar demographic and metabolic parameters. Short-term morbidity and long-term outcomes were similar. The operative time was significantly shorter with splenectomy: a median of 9.91 h (interquartile range [IQR] 8.89-10.83) compared to 10.78 h (IQR 10.2-11.6) for SPTP (P = 0.021). There was no difference between the groups in postoperative morbidity. Metabolic outcomes at 1 year were better in the SPTP group compared to the splenectomy group, with a median daily insulin requirement of 7 units (IQR 4-12) vs 15 units (IQR 7-26; P = 0.049) and a median C-peptide at 1 year of 0.65 (IQR 0.40-1.26) vs 1.00 (IQR 0.80-1.90; P = 0.63). The reduction in morphine milligram equivalents per day over time was significantly better in the SPTP group (P < 0.001), as was the decrease in pain score (P < 0.001).

CONCLUSION

TPIAT with full arterial and venous preservation of the spleen had no adverse impact on islet yield or function. TPIAT can be safely and effectively performed with preservation of the spleen and the entire splenic artery and vein. The spleen should be preserved when feasible in every TPIAT surgery.

Postoperative Outcomes Analysis After Pancreatic Duct Occlusion: A Safe Option to Treat the Pancreatic Stump After Pancreaticoduodenectomy in Low-Volume Centers

Background: Surgical resection is the only possible choice of treatment in several pancreatic disorders that included periampullar neoplasms. The development of a postoperative pancreatic fistula (POPF) is the main complication. Despite three different surgical strategies that have been proposed–pancreatojejunostomy (PJ), pancreatogastrostomy (PG), and pancreatic duct occlusion (DO)–none of them has been clearly validated to be superior. The aim of this study was to analyse the postoperative outcomes after DO.

Methods: We retrospectively reviewed 56 consecutive patients who underwent Whipple's procedure from January 2007 to December 2014 in a tertiary Hepatobiliary Surgery and Liver Transplant Unit. After pancreatic resection in open surgery, we performed DO of the Wirsung duct with Cyanoacrylate glue independently from the stump characteristics. The mean follow-up was 24.5 months.

Results: In total, 29 (60.4%) were men and 19 were (39.6%) women with a mean age of 62.79 (SD ± 10.02) years. Surgical indications were in 95% of cases malignant diseases. The incidence of POPF after DO was 31 (64.5%): 10 (20.8%) patients had a Grade A fistula, 18 (37.5%) Grade B fistula, and 3 (6.2%) Grade C fistula. No statistical differences were demonstrated in the development of POPF according to pancreatic duct diameter groups (p = 0.2145). Nevertheless, the POPF rate was significantly higher in the soft pancreatic group (p = 0.0164). The mean operative time was 358.12 min (SD ± 77.03, range: 221–480 min). Hospital stay was significantly longer in patients who developed POPF (p < 0.001). According to the Clavien-Dindo (CD) classification, seven of 48 (14.58%) patients were classified as CD III–IV. At the last follow-up, 27 of the 31 (87%) patients were alive.

Conclusions: Duct occlusion could be proposed as a safe alternative to pancreatic anastomosis especially in low-/medium-volume centers in selected cases at higher risk of clinically relevant POPF.

Circulating dipeptidyl peptidase-4 is independently associated with the presence and severity of NAFLD/NASH in individuals with and without obesity and metabolic disease

INTRODUCTION

Dipeptidyl peptidase 4 (DPP4) levels are associated to metabolic and cardiovascular diseases in humans; initial evidence reported a relationship between DPP4 and chronic liver diseases. Aim of this study was to investigate hepatic and systemic DPP4 levels/activity in relation to NAFLD/NASH in individuals with and without metabolic disease.

METHODS

We recruited fifty-two obese individuals undergoing bariatric surgery and intra-operative liver biopsy at Sapienza University, Rome, Italy. The association between DPP4 levels/activity and NAFLD was also evaluated in 126 non-obese individuals recruited in the same setting.

RESULTS

NAFLD patients had significantly higher circulating DPP4 activity than no-NAFLD in both the obese and non-obese cohorts; plasma DPP4 activity and levels linearly correlated with steatosis grade and inflammation at the liver biopsy. Hepatic DPP4 mRNA was not associated to either its circulating levels/activity or NAFLD. In the multivariate logistic regression analysis on all the study participants (n = 178), higher circulating DPP4 activity was associated with NAFLD independently of potential confounders with OR (95% CI): 3.5 (1.2-10.21), p = 0.022.

CONCLUSIONS

This study demonstrates the coexistence of increased plasma DPP4 levels and activity in NAFLD. Circulating DPP4 measurement may represent a novel cost-effective strategy for NAFLD/NASH risk stratification and a potential tool for monitoring disease's progression in established NAFLD.

Myogenic oxidative imbalance interferes with antral motility in obese subjects

BACKGROUND

Obesity is characterized by a systemic low-grade chronic inflammatory oxidative condition that affects vascular and cardiac smooth muscle relaxation. In human antrum, relaxation is mediated by vasoactive intestinal peptide (VIP) through cAMP and cGMP signaling pathways. A genome-wide association study has demonstrated an association between VIP and obesity.

AIM

To evaluate smooth muscle activity in human obese antrum, both in in vitro preparations as well as in vivo.

METHODS

Antral muscle strips and cells were isolated from surgical gastric samples from obese and normal weight subjects. Muscle contraction and relaxation, myogenic oxidative stress and inflammatory status were analyzed in vitro. Distal antral motility was evaluated in vivo by magnetic resonance imaging.

RESULTS

Obese antral muscle cells showed an oxidative-inflammatory imbalance with overexpression of NLRP3 inflammasome, increased IL-1β secretion and caspase1-activation, and reduced antioxidant capacity associated with a myogenic motor impairment of VIP-induced relaxation. The intracellular alterations were characterized by a decreased activation of the cAMP-signaling pathway and a decreased expression of eNOS. These in vitro alterations coincided with the hindering of antral motor activity observed in vivo. Apocynin treatment, counteracting oxidative stress, reverted alterations observed in obese antral muscle.

CONCLUSION

Antral myogenic activity of obese subjects can be impaired by alterations of signaling pathways induced by oxidative stress.

Rectal Carcinoid Tumor With Liver Metastases Treated by Local Excision and Orthotopic Liver Transplant With Long-term Follow-up

In patients affected by unresectable liver metastases from neuroendocrine tumor, liver transplant represents currently the only realistic chance for cure. The first attempt to establish selection criteria for liver transplant in patients affected by neuroendocrine tumor liver metastases was made by Mazzaferro and associates in 2007. We report the case of a 46-year-old man who came to our institution in 2006 with right upper quadrant abdominal pain. Diagnosis of rectal neuroendocrine tumor with bilobar liver nodules was made; the patient underwent transanal local resection. A liver biopsy confirmed the metastatic nature of the hepatic lesion, showing a low-grade neuroendocrine tumor (G1, proliferation index Ki-67 <2%). The patient underwent 2 sessions of transarterial chemoembolization that resulted in stable disease. Afterward, the patient underwent a liver transplant, using the piggyback technique without a venous-venous bypass. His postoperative course was uneventful. The patient has been disease-free for 3 years. Posttransplant treatment has played a key role in increasing the overall survival of the patient and assuring him a good quality of life. He died 9 years (102 mo) after liver transplant.

Recurrent gallstone ileus: case report and literature review

The gallstone ileus is a rare complication of cholelithiasis and it represents the 1-4% of small intestinal mechanical obstruction. Gallstone is generally wedged in the terminal ileum, even if unusual locations have been described. The literature reports a very high morbidity and mortality, often because misdiagnosis or delayed diagnosis. There is no unique opinion in literature about the choice between one-stage and two-stage surgery. We report a clinical case that summarizes the diagnostic and therapeutic difficulties of gallstone ileus.

Evaluation of bloodsucking arthropod bite as possible risk co-factor in Human herpesvirus-8 transmission route

Human herpesvirus-8 non-sexual transmission occurs primarily from mother-to-child. The viral load in saliva is higher than in other human fluids. Moreover, there is evidence that bloodsucking arthropod bites induce an inflammatory/immune response that facilitates viral replication. We aim to explore possible risk factors in mother-to-child HHV-8 transmission associated with traditional methods which involve the use of saliva to relieve the irritation and skin reaction caused by arthropod bites. We administered questionnaires to 2244 children from several African countries and Italy. Descriptive statistics and logistic regression were used in the analysis of the answers to evaluate the relationships between the use of traditional methods and other risk factors. The use of traditional methods is high in Cameroon (63.0%) and Uganda (39.9%), intermediate in Senegal (26.7%) and Italy (21.7%), low in Madagascar (6.7%). Statistical analyses show significant direct relationships between the use of traditional methods, skin reactions to the bite and their duration in Cameroon, Uganda and Senegal. The use of saliva and herbs applied by the mothers on the child's skin, is a common habit in Africa. If this practice plays a role in the HHV-8 transmission, then, it could provide the basis for interventions capable of reducing the health impact of the infection in children in tropical areas.

Distribution of 'promoter' sandflies associated with incidence of classic Kaposi's sarcoma

The patchy geographical distributions of classic Kaposi's sarcoma (KS) and human herpesvirus type 8 (HHV-8), better known as Kaposi's sarcoma-associated herpesvirus (KSHV) remain unexplained. It has been proposed that certain species of bloodsucking insects ('promoter arthropods') promote the reactivation of HHV-8/KSHV and facilitate both HHV-8/KSHV transmission and KS development. This hypothesis was tested by sampling the presence and density of human-biting Diptera with CDC light traps in two areas of Sardinia with contrasting incidence rates of classic KS. In total, 11,030 specimens (99.9% sandflies and 0.1% mosquitoes) belonging to 10 species were collected from 40 rural sites. Five of these species are considered to be possible promoter arthropods because of the irritation their bites cause: Phlebotomus perniciosus Newstead; Phlebotomus perfiliewi Parrot (Diptera: Psychodidae); Aedes berlandi Seguy; Culiseta annulata (Schrank) and Culex theileri Theobald (Diptera: Culicidae). Five species are probable 'non-promoters' because their bites are not particularly irritating: Culiseta longiareolata (Macquart); Culex pipiens s.l.; Anopheles algeriensis Theobald; Anopheles maculipennis s.l., and Anopheles plumbeus Stephens. A significant correlation was found between the geographical distribution of promoter arthropods and incidence rates of KS (Spearman's r = 0.59,P < 0.01). Promoter arthropods were more likely to be caught in areas with cutaneous leishmaniasis and a past high prevalence of malaria, and in areas of limestone, acid volcanic soil and cereal cultivation. The study supports the association between promoter arthropods and classic KS, which may explain the geographic variability of KS and HHV-8/KSHV, and highlights the links with a number of variables previously associated with the incidence of KS.

The role of research in molecular entomology in the fight against malaria vectors

The text summarizes the principal current fields of investigation and the recent achievements of the research groups presently contributing to the Molecular Entomology Cluster of the Italian Malaria Network. Particular emphasis is given to the researches with a more direct impact on the fight against malaria vectors.

Comparative analysis of epicuticular lipid profiles of sympatric and allopatric field populations of Anopheles gambiae s.s. molecular forms and An. arabiensis from Burkina Faso (West Africa)

We analysed by gas chromatography-mass spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID) the epicuticular lipid profiles of field females of the major Afro-tropical malaria vector, Anopheles gambiae. The samples were collected in three villages in Burkina Faso (West Africa), where An. gambiae M and S molecular forms and An. arabiensis live sympatrically. The aim was to compare the cuticular hydrocarbon (CHC) composition of individual field specimens of these three taxa, to highlight possible differences among them. All the samples analysed by GC-MS (55 individuals and eight pools) were characterized by the same 48 CHCs and 10 oxygenated compounds. The 19 most abundant CHCs were quantified in 174 specimens by GC-FID: quantitative intra-taxon differences were found between allopatric populations of both An. arabiensis and S-form. Inter-taxa quantitative differences in the relative abundances of some hydrocarbons between pairs of sympatric taxa were also found, which appear to be mainly linked to local situations, with the possible exception of diMeC(35) between An. arabiensis and S-form. Moreover, MeC(29) shows some degree of differentiation between S- and M-form in all three villages. Possible causes of these differences are discussed.

Distribution of mosquito species in areas with high and low incidence of classic Kaposi's sarcoma and seroprevalence for HHV-8

The 'promoter-arthropod' hypothesis, which postulates that exposure to the bites of certain species of haematophagous arthropods is an environmental risk cofactor linked to human herpes virus 8 (HHV-8) and Kaposi's sarcoma, was investigated in the Po River valley, northern Italy. The presence and density of adult female mosquitoes (Diptera: Culicidae) was determined by CDC light trap catches in two adjacent districts, at variance with respect to Kaposi's sarcoma incidence and HHV-8 seroprevalence. A total of 3910 specimens belonging to 11 species was collected in 34 rural sites (six municipalities) representative of the two districts. Five of these species are considered to be possible 'promoters' because of the irritation their bites cause humans: Aedes vexans (Meigen) and Ae. caspius (Pallas) (87% of sampled promoters), Culex modestus Ficalbi, Culiseta annulata (Schrank) and Coquillettidia richiardii (Ficalbi). Six are probable 'non-promoters': Cx. pipiens s.l., Cx. martinii Medschid, Anopheles claviger (Meigen), An. maculipennis s.l., An. plumbeus Stephens and Uranotaenia unguiculata Edwards. The density of promoters by site was correlated with the incidence rates of Kaposi's sarcoma at the district level (Pearson's r = 0.33, P = 0.06) and at the municipal level (r = 0.50, P< 0.01). Similar correlations emerged for non-promoters (r = 0.48, P< 0.01 and r = 0.42, P = 0.01, respectively). The density of promoters was higher than that of non-promoters in sites with livestock (odds ratio, OR = 2.8, 95% CI 2.2-3.6) and in municipalities with Kaposi's sarcoma cases (OR = 2.5, 95% CI 1.7-3.5). The study provides additional evidence of the association between the density of some mosquito species and Kaposi's sarcoma.

Genetic complexity and gametocyte production of Plasmodium falciparum in Fulani and Mossi communities in Burkina Faso

We have examined Plasmodium falciparum gametocyte prevalence, density and their genetic complexity among children of 2 sympatric ethnic groups (Mossi and Fulani) in villages in Burkina Faso. The 2 groups are known to have distinct differences in their susceptibility and immune responses to malaria. We used RT-PCR and sequence-specific probes to detect and type RNA of the gametocyte-specific protein Pfs48/45. There were no differences in detection rates of asexual forms and gametocytes among the 2 groups, using PCR and RT-PCR, respectively. However, there were significant differences in densities of asexual forms and gametocytes, which were both higher among Mossi than Fulani. Both asexual forms and gametocyte densities were influenced by age and ethnicity. Multiple-clone infections with more than 1 gametocyte genotype were equally prevalent among Fulani and Mossi. These differences can most probably be attributed to genetic differences in malaria susceptibility in the 2 ethnic groups.

Malaria vector analysis and control

Antivector measures in malaria control should aim for a cost-effective reduction of the transmission potential ideally to below the critical level for sustained transmission. The available measures include those that decrease vector abundance, vector-human contact and vector survival rate or that increase the length of the sporogonic cycle. These have widely different impact on malaria transmission, as shown by epidemiological modelling. Direct modification of vector receptivity to Plasmodium is also hypothetically attainable by the use of transmission-blocking vaccines or by genetic manipulation and replacement of the vector population. Vector analysis constitutes the essential prerequisite for basic malaria epidemiology as well as for the development, planning and evaluation of antivector measures. The rationale, the problems and the perspectives of vector analysis are reviewed here by Mario Coluzzi, on the basis of his experience with Afrotropical and Mediterranean malaria vectors.

An Anopheles gambiae salivary gland promoter analysis in Drosophila melanogaster and Anopheles stephensi

Regulatory regions driving gene expression in specific target organs of the African malaria vector Anopheles gambiae are of critical relevance for studies on Plasmodium-Anopheles interactions as well as to devise strategies for blocking malaria parasite development in the mosquito. In order to identify an appropriate salivary gland promoter we analysed the transactivation properties of genomic fragments located just upstream of the An. gambiae female salivary gland-specific genes AgApy and D7r4. An 800 bp fragment from the AgApy gene directed specific expression of the LacZ reporter gene in the salivary glands of transgenic Anopheles stephensi. However, expression levels were lower than expected and the transgene was expressed in the proximal-rather than in the distal-lateral lobes of female glands. Surprisingly, a promoter fragment from the D7r4 gene conferred strong tissue-specific expression in Drosophila melanogaster but only low transcription levels in transgenic An. stephensi. These results imply a certain conservation of gland-specific control elements between the fruit fly and the mosquito suggesting that an increased degree of complexity, probably connected to the evolution of haematophagy, underlies the regulation of tissue-specific expression in mosquito female salivary glands.

Reduced seroprevalence of Kaposi's sarcoma-associated herpesvirus (KSHV), human herpesvirus 8 (HHV8), related to suppression of Anopheles density in Italy

In two formerly malarious parts of Italy, age-related seroprevalence rates of Kaposi's sarcoma-associated herpesvirus [human herpesvirus 8 (KSHV/HHV8)] were determined from local blood donors and correlated with periods of vector control during anti-malaria campaigns. In Veneto, decreased KSHV/HHV8 seroprevalence in the 1951-1955 birth cohort coincides with the peak of DDT house-spraying. In Sardinia, where larviciding augmented indoor DDT-spraying, a significant drop of KSHV/HHV8 seroprevalence between 1945 and 1950 and 1951-1955 birth cohorts (P = 0.0046) coincides with suppression of the malaria vector Anopheles labranchiae Falleroni (Diptera: Culicidae). These results are consistent with age-related association between KSHV/HHV8 seroprevalence rates in native/resident populations and the density of malaria vectors in Veneto and Sardinia. This example supports our 'promoter arthropod' hypothesis on the role of haematophagous insects [putatively blackflies (Simuliidae), sandflies (Phlebotominae) and biting midges (Ceratopogonidae), as well as mosquitoes] when their bites induce hypersensitivity and immunosuppression, potentiate KSHV/HHV8 transmission via human saliva (when insect bite lesions are licked by another person whose saliva carries the virus) and may facilitate Kaposi's sarcoma.

The pyrethroid knock-down resistance gene in the Anopheles gambiae complex in Mali and further indication of incipient speciation within An. gambiae s.s

In Mali the Anopheles gambiae complex consists of An. arabiensis and Mopti, Savanna and Bamako chromosomal forms of An. gambiae s.s. Previous chromosomal data suggests a complete reproductive isolation among these forms. Sequence analysis of rDNA regions led to the characterization of two molecular forms of An. gambiae, named M-form and S-form, which in Mali correspond to Mopti and to Savanna/Bamako, respectively, while it has failed so far to show any molecular difference between Savanna and Bamako. The population structure of An. gambiae s.l. was analysed in three villages in the Bamako and Sikasso areas of Mali and the frequency of pyrethroid resistance of the knock-down resistance (kdr) type was calculated. The results show that the kdr allele is associated only with the Savanna form populations and absent in sympatric and synchronous populations of Bamako, Mopti and An. arabiensis. This is the first molecular indication of barriers to gene flow between the Bamako and Savanna chromosomal forms. Moreover, analyses of specimens collected in the Bamako area in 1987 show that the kdr allele was already present in the Savanna population at that time, and that the frequency of this allele has gradually increased since then.

An alternative focus in strategic research on disease vectors: the potential of genetically modified non-biting mosquitoes

We examine the constraints and the feasibility of field experiments involving the release of genetically modified (GM) pathogen-resistant mosquitoes, and whether there are alternatives to the research line based on the production of refractory strains. The production of a GM mosquito strain characterized instead by obligate primiparous and parous autogeny and by disrupted host seeking and biting behaviour could make the release more acceptable by the general public. Genetic transformation should act in this case to reverse some of the essential steps of the evolutionary process that gave rise to hematophagy. The replacement strategy could be based on the mass release of both sexes in a well defined ecological niche made temporarily empty of the natural population, thus avoiding the problems related to the need of sexual competitiveness of the released material. This option is encouraged by the growing evidence that competitive exclusion mechanisms influence the pattern of distribution of different taxa within Anopheles gambiae s.s. and by the fact that the plesiomorphic characteristics of vitellogenesis without a blood meal (autogeny), which exploits fat body reserve accumulated during larval life and food other than blood in adult life, persist as genetic variants in various hematophagous insect groups, and it has been found secondarily fixed in others showing stable reversions to primiparous and parous autogeny. If this has been the result of natural selection, then the artificial production of non-biting mosquito strains, by selection and/or transgenesis, should be feasible.

Editorial introduction to the paper by A. Celli and G. Gasperini reprinted from Atti della Società per gli studi della Malaria (Volume III, 1902, pp. 115-145)

The editorial note introduces the issue of Anopheles without malaria focused in 1902 by Celli and Gasperini. The historical problem is outlined until the puzzle was solved in the Fourties.

Speciation within Anopheles gambiae--the glass is half full

Restrictions to gene flow among molecular forms of the mosquito Anopheles gambiae sensu stricto reveal an ongoing speciation process affecting the epidemiology of malaria in sub-Saharan Africa.

The bloodsucking arthropod bite as possible cofactor in the transmission of human herpesvirus-8 infection and in the expression of Kaposi's sarcoma disease

Based on a review of the literature on human herpesvirus-8 (HHV8) and Kaposi's sarcoma (KS) and on the distribution of KS in Italy (Veneto region particularly), we hypothesize that the bite of bloodsucking arthropods is a cofactor in the seroconversion to HHV8 positivity and probably in the pathogenesis of KS. The bloodsucking arthropod releases with saliva powerful antihaemostatics and immunomodulators which may favour the replication and the establishment of the pathogen. Transmission would depend on the close contact of the child with a seropositive mother (or relatives) whose infective saliva is used to relieve itching and scratching at the arthropod bite's sites. During any deregulation of the immune system (e.g. ageing), local immune responses to new insect bites may induce virus activation which could prelude KS insurgence. The pathogen is not directly transmitted by the arthropod which merely prepares the cutaneous microenvironment for the virus. We have therefore introduced a new category of medically important arthropods, "promoter arthropods", besides those already defined as biological or mechanical vectors. Promoter arthropods are species able to induce in the host long-lasting, immediate or delayed-type hypersensitivity responses as well as local immunosuppression due to substances injected with their saliva. The striking variability of ORF-K1 gene of HHV8 could be due to the adaptation of the virus to the specific microenvironments resulting from the immune response to the salivary antigens characteristic of the bloodsucking arthropod species prevalent in each geographical area. It is worth noting that other viruses (especially Hepatitis B Virus) may exploit the same non-sexual transmission route.

A cluster of four D7-related genes is expressed in the salivary glands of the African malaria vector Anopheles gambiae

Four genes expressed in the Anopheles gambiae adult female salivary glands and similar in sequence to the Aedes aegypti D7 gene were identified. The genes, called D7-related (D7r), are included in a single cluster encompassing approximately six kilobases on chromosome arm 3R. The deduced proteins contain secretory signals and they are probably injected by the mosquito into the host with the saliva during blood feeding. The region of similarity to D7 encompasses the carboxy-terminal part of the Ae. aegypti protein and the different An. gambiae D7r show a degree of similarity to each other, varying from 53% to 73%. The weak but significant similarity to members of a wide family of insect proteins, including odourant- and pheromone-binding proteins, raises the possibility that the D7r-encoded proteins may bind and/or carry small hydrophobic ligands.

Haemoglobin C protects against clinical Plasmodium falciparum malaria

Haemoglobin C (HbC; beta6Glu --> Lys) is common in malarious areas of West Africa, especially in Burkina Faso. Conclusive evidence exists on the protective role against severe malaria of haemoglobin S (HbS; beta6Glu --> Val) heterozygosity, whereas conflicting results for the HbC trait have been reported and no epidemiological data exist on the possible role of the HbCC genotype. In vitro studies suggested that HbCC erythrocytes fail to support the growth of P. falciparum but HbC homozygotes with high P. falciparum parasitaemias have been observed. Here we show, in a large case-control study performed in Burkina Faso on 4,348 Mossi subjects, that HbC is associated with a 29% reduction in risk of clinical malaria in HbAC heterozygotes (P = 0.0008) and of 93% in HbCC homozygotes (P = 0.0011). These findings, together with the limited pathology of HbAC and HbCC compared to the severely disadvantaged HbSS and HbSC genotypes and the low betaS gene frequency in the geographic epicentre of betaC, support the hypothesis that, in the long term and in the absence of malaria control, HbC would replace HbS in central West Africa.

Antimalarial antibody levels and IL4 polymorphism in the Fulani of West Africa

The Fulani are less clinically susceptible and more immunologically responsive to malaria than neighbouring ethnic groups. Here we report that anti-malarial antibody levels show a wide distribution amongst the Fulani themselves, raising the possibility that quantitative analysis within the Fulani may be an efficient way of screening for important genetic factors. The Th2 cytokine interleukin-4 is an obvious candidate: in Fulani, the IL4-524 T allele is at high frequency and is associated with elevated antibody levels against malaria antigens. These data highlight the possibility of combining inter- and intra-ethnic comparisons to characterize critical determinants of malarial immunity in a natural setting.

Electroantennogram and behavioural responses of the malaria vector Anopheles gambiae to human-specific sweat components

Afrotropical malaria vectors of the Anopheles gambiae complex (Diptera: Culicidae), particularly An. gambiae sensu stricto, are attracted mainly to human hosts. A major source of human volatile emissions is sweat, from which key human-specific components are the carboxylic acids (E)- and (Z)-3-methyl-2-hexenoic acid and 7-octenoic acid. Electrophysiological studies on the antennae of An. gambiae s.s. showed selective sensitivity to these compounds, with a threshold at 10(-6) g comparable to that of known olfactory stimulants 1-octen-3-ol, p-cresol, isovaleric acid, and lower than threshold sensitivity to L-lactic acid and the synthetic mosquito repellent N,N-diethyltoluamide (DEET). A combination of the acids released at concentrations > 10(-5) g in wind tunnel bioassays significantly reduced the response to CO2, the major attractant released by human hosts, for strains of An. gambiae s.s. originating from East and West Africa. Field trials with odour-baited entry traps (OBETs) in Burkina Faso showed that 7-octenoic acid significantly increased (by 1.7-fold) the catch of females of An. gambiae sensu lato (comprising two sibling species: An. arabiensis Patton and An. gambiae s.s.) in OBETs baited with CO2, whereas combinations of the acids significantly reduced the catch in CO2-baited traps (by 2.1-fold) and in whole human odour-baited traps (by 1.5-fold). The pure (E) and (Z) geometric isomers of 3-methyl-2-hexenoic acid gave comparable results to the (EIZ) isomer mixture. These results provide the first experimental evidence that human-specific compounds affect the behaviour of highly anthropophilic An. gambiae s.l. mosquitoes. The compounds appear to inhibit the upwind flight' response to known long-range attractants, and may serve either to mask' the attractants present or, more probably, to 'arrest' upwind flight when mosquitoes arrive at a host under natural conditions. In the final approach to hosts, vectors are known to reduce their flight speed and increase their turning rate, to avoid overshooting the source. In our experimental apparatus, these changes in flight behaviour would reduce the number of mosquitoes entering the ports of the collection devices.

The lower susceptibility to Plasmodium falciparum malaria of Fulani of Burkina Faso (west Africa) is associated with low frequencies of classic malaria-resistance genes

The gene frequencies in 1993-94 for haemoglobin S, haemoglobin C, alpha-3.7 deletional thalassaemia, G6PDA-, HLAB*5301 were estimated in Fulani, Mossi and Rimaibé ethnic groups of Burkina Faso, West Africa. The aim of the study was to verify whether the previously reported Fulani lower susceptibility to Plasmodium falciparum malaria was associated with any of these malaria-resistance genes. Similar frequencies for haemoglobin S were recorded in the 3 ethnic groups (0.024 +/- 0.008, 0.030 +/- 0.011, 0.022 +/- 0.013; in Mossi, Rimaibé and Fulani, respectively). The Mossi and Rimaibé showed higher frequencies when compared to Fulani for haemoglobin C (0.117 +/- 0.018, 0.127 +/- 0.020, 0.059 +/- 0.020), alpha-3.7 deletional thalassaemia (0.227 +/- 0.040, 0.134 +/- 0.032, 0.103 +/- 0.028), G6PDA- (0.196 +/- 0.025, 0.187 +/- 0.044, 0.069 +/- 0.025) and HLA B*5301 (0.189 +/- 0.038, 0.202 +/- 0.041, 0.061 +/- 0.024). Among Fulani the proportion of individuals not having any of these protective alleles was more than 3-fold greater than in the Mossi-Rimaibé group (56.8% vs 16.7%; P < 0.001). These findings exclude the involvement of these genetic factors of resistance to P. falciparum in the lower susceptibility to malaria of Fulani. This evidence, in association with the previously reported higher immune reactivity to malaria of Fulani, further supports the existence in this ethnic group of unknown genetic factor(s) of resistance to malaria probably involved in the regulation of humoral immune responses.

Zoophily of Anopheles arabiensis and An. gambiae in Madagascar demonstrated by odour-baited entry traps

In Madagascar we used odour-baited entry traps (OBETs) for host choice tests of wild female anopheline mosquitoes (Diptera: Culicidae) at representative localities on the East and West sides of the island (villages Fenoarivo and Tsararano, respectively) and at the southern margin of the central plateau (Zazafotsy village, 800 m altitude). No insecticide house-spraying operations have been undertaken at these villages. Odours from a man and a calf of similar mass, concealed in different tents, were drawn by fans into separate OBETs set side by side. Traps were alternated to compensate for position effects, and different pairs of individual baits were employed for successive replicates. Totals of 266 An. funestus Giles sensu stricto and 362 An. gambiae Giles sensu lato were collected in 48 trap nights during March-June 1999. For each mosquito species the 'index of anthropophily' was defined as the proportion of females caught in the human-baited trap. For An. funestus this index was found to be consistently greater than 0.5 (value for random choice between traps/hosts), indicating that this species 'preferred' human to calf odour (index=0.83). Conversely, the index of anthropophily for An. gambiae s.l. indicated they 'chose' calf in preference to human odour (index=0.26). No significant differences of relative preference for calf or man were detected between villages; geographical variance accounted for <8% of the total experimental variance. Molecular identifications of 181 specimens of the An. gambiae complex (approximately 50% of the samples) revealed only An. arabiensis Patton at Tsararano and Zazafotsy, but >97% An. gambiae Giles sensu stricto at Fenoarivo, in accordance with prior knowledge of the differential distributions of these sibling species on the island. Predominant zoophily (i.e. intrinsic 'preference' for cattle odours) by both An. arabiensis and An. gambiae s.s. in Madagascar contrasts with their greater anthropophily in continental Africa.

Patterns of DNA sequence variation in chromosomally recognized taxa of Anopheles gambiae: evidence from rDNA and single-copy loci

Patterns of DNA sequence variation in the ribosomal DNA (rDNA) second internal transcribed spacer (ITS2) and five unlinked single-copy nuclear loci were examined for evidence of reproductive isolation among four chromosomally recognized taxa of Anopheles gambiae from West Africa: Savanna, Bamako, Mopti and Forest, as well as sibling species An. arabiensis and An. merus. Included among the single-copy loci were three sequence-tagged random amplified polymorphic DNA (RAPD) loci, two of which (R15 and R37) had been reported as discriminating between Mopti and other chromosomal forms. Each of the five single-copy sequences were highly polymorphic in most samples. However, the R15 and R37 loci had no diagnostic value, and therefore are not recommended as tools in recognition of field-collected An. gambiae chromosomal forms. Although pairwise comparisons between species generally revealed significant levels of differentiation at all five loci, variation was not partitioned by chromosomal form within An. gambiae at any single-copy locus examined. The few exceptions to these trends appear related to a location either inside or nearby chromosomal inversions. At the tryptophan oxygenase locus inside inversion 2Rb, variation was structured only by inversion orientation and not by taxonomic designation even between An. gambiae and An. arabiensis, providing the first molecular evidence that the 2Rb inversion was transferred between species by introgressive hybridization. By contrast, the rDNA showed fixed differences between species and a difference diagnostic for Mopti, consistent with effective, if not complete, reproductive isolation. The apparent disagreement between the data from this locus and multiple single-copy loci within An. gambiae may be explained by the much lower effective population size of rDNA, owing to concerted evolution, which confers increased sensitivity at much shorter divergence times. Taken together with the accompanying reports by della Torre et al. (2001), Favia et al. (2001) and Gentile et al. (2001), our data suggest that neutral molecular markers may not have the sensitivity required to detect isolation between these recently established taxa.

Molecular evidence of incipient speciation within Anopheles gambiae s.s. in West Africa

We karyotyped and identified by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis Anopheles gambiae s.s. samples collected in several African countries. The data show the existence of two non-panmictic molecular forms, named S and M, whose distribution extended from forest to savannahs. Mosquitoes of the S and M forms are homosequential standard for chromosome-2 inversions in forest areas. In dry savannahs, S is characterized mainly by inversion polymorphisms typical of Savanna and Bamako chromosomal forms, while M shows chromosome-2 arrangements typical of Mopti and/or Savanna and/or Bissau, depending on its geographical origin. Chromosome-2 inversions therefore seem to be involved in ecotypic adaptation rather than in mate-recognition systems. Strong support for the reproductive isolation of S and M in Ivory Coast comes from the observation that the kdr allele is found at high frequencies in S specimens and not at all in chromosomal identical M specimens. However, the kdr allele does not segregate with molecular forms in Benin.

HLA class I in three West African ethnic groups: genetic distances from sub-Saharan and Caucasoid populations

Fulani of Burkina Faso (West Africa) are a particularly interesting ethnic group because of their lower susceptibility to Plasmodium falciparum malaria as compared to sympatric populations, Mossi and Rimaibé. Moreover, the occurrence of a Caucasoid component in their genetic make-up has been suggested on the basis of their physical traits and cultural traditions even though this view was not supported by genetic studies. A total of 149 unrelated subjects (53 Mossi, 47 Rimaibé and 49 Fulani) have been typed for 97 HLA class I alleles with the amplification refractory mutation system/polymerase chain reaction (ARMS/PCR) technique. Mossi and Rimaibé data were pooled since none of the 42 statistically testable alleles exhibited a significant heterogeneity. These pooled gene frequencies were found to be very different from those of Fulani: a certain (P<0.001) or a likely (0.001 <P<0.01) difference was found for 5 and 12 alleles, respectively. Four alleles (A*24, A*29, B*27, B*3701) appeared to be essentially "private" Fulani alleles with respect to the other two populations but their presence was not associated with higher resistance to P. falciparum. Our data have then been compared using chord distances (CD) with those from the literature on Africans (including Gambian Fulani) and Caucasoids. The Burkina Faso and Gambian Fulani turned out to be very different (CD=2.191). Moreover, Burkina Faso Fulani were very distant from sympatric Mossi and Rimaibé (CDs=1.912 and 1.884), whereas Gambian Fulani were similar to sympatric Mandinka and Wolof (CDs=0.412 and 0.388) to an extent comparable to that found between Mossi and Rimaibé (CD=0.555). Our study does not suggest the involvement of HLA I in the higher resistance to malaria of Fulani, and confirms a low, if any, Caucasoid component in their gene pool.

[Malaria eradication in Calabria, residual anopheles and transmission risk]

The paper is from a presentation at the meeting "La malaria in Calabria" (Cosenza, Italy, May 3, 1997) held to celebrate the half centenary of the antimalaria campaign (1947-1952) that eradicated the infection from the region. While Plasmodium falciparum had already disappeared in 1950, P. vivax persisted and the last autochtonous case was documented on the river Esaro in 1955. From the records of that time, it is clear that malaria eradication was achieved in the presence of important vector densities, as shown by larval surveys. Indoor DDT spraying, acting through the insecticide irritant effect, mainly avoided the house resting by the vector and forced the exposure of the mosquito to the outdoor environment where the lower mean temperatures eventually proved instrumental in destabilizing the parasite's life cycle. It is stressed that insecticide resistance never arised in the Anopheles vector populations of Calabria, in spite of at least ten years of continuous indoor spraying with an excellent overall coverage. This is expected in the absence of important selection pressures at the larval breeding sites and whenever the impact of the house spraying on the vector is due mainly to the insecticide irritant effect rather than to a direct imagocidal effect.

Promoter sequences of the putative Anopheles gambiae apyrase confer salivary gland expression in Drosophila melanogaster

The saliva of blood-feeding arthropods contains an apyrase that facilitates hematophagy by inhibiting the ADP-induced aggregation of the host platelets. We report here the isolation of a salivary gland-specific cDNA encoding a secreted protein that likely represents the Anopheles gambiae apyrase. We describe also two additional members of the apyrase/5'-nucleotidase family. The cDNA corresponding to the AgApyL1 gene encodes a secreted protein that is closely related in sequence to the apyrase of the yellow fever mosquito, Aedes aegypti, and whose expression appears enriched in, but not restricted to, female salivary glands. The AgApyL2 gene was found searching an A. gambiae data base, and its expression is restricted to larval stages. We isolated the gene encoding the presumed A. gambiae apyrase (AgApy) and we tested its putative promoter for the tissue-specific expression of the LacZ gene from Escherichia coli in transgenic Drosophila melanogaster. All the transgenic lines analyzed showed a weak but unambiguous staining of the adult glands, indicating that some of the salivary gland-specific transcriptional regulatory elements are conserved between the malaria mosquito and the fruit fly. The availability of salivary gland-specific promoters may be useful both for studies on vector-parasite interactions and, potentially, for the targeted tissue-specific expression of anti-parasite genes in the mosquito.

Cytogenetics of the Anopheles gambiae complex in Sudan, with special reference to An. arabiensis: relationships with East and West African populations

The species composition of malaria vector mosquitoes belonging to the Anopheles gambiae complex (Diptera: Culicidae) from >40 localities in Sudan, representing most ecological situations, was determined by analysis of ovarian polytene chromosomes. Of 2162 females, 93% were identified as An. arabiensis Patton and 7% were An. gambiae Giles sensu stricto. No hybrids were found between the two species. Anopheles arabiensis occurred in all but two sites, whereas An. gambiae s.s. was effectively limited to the southernmost, more humid localities. For chromosomal paracentric inversions, the degree of polymorphism was low in An. gambiae s.s. (inversions 2La, 2Rb and 2Rd), higher in An. arabiensis (inversions Xe, 2Ra, b, bc, d1, s; 3Ra, d). Anopheles gambiae samples from Sudan were all apparently panmictic, i.e. they did not show restricted gene flow such as observed among West African populations (interpreted as incipient speciation). Chromosomal inversion patterns of An. gambiae in southern Sudan showed characteristics of intergrading Savanna/Forest populations similar to those observed in comparable eco-climatic situations of West Africa. Anopheles arabiensis was polymorphic for inversion systems recorded in West Africa (2Ra, 2Rb, 2Rdl, 3Ra) and for a novel 2Rs polymorphism, overlapping with inversion systems 2Rb and 2Rd1. Samples carrying the 2Rs inversion were mostly from Khashm-el-Girba area in central-eastern Sudan. In the great majority of the samples all polymorphic inversions were found to be in Hardy-Weinberg equilibrium. Sudan populations of An. arabiensis should therefore be considered as generally panmictic. Anopheles arabiensis shows more inversion polymorphism in west than in east African populations. Sudan populations have more evident similarities with those from westwards than those from eastwards of the Great Rift Valley. The possible influence of the Rift on evolution of An. arabiensis is discussed.

Chromosomal and bionomic heterogeneities suggest incipient speciation in Anopheles funestus from Burkina Faso

Sampling of day-resting Anopheles funestus was carried out in September-November 1991, October-December 1992, and November 1994 at two sites near Ouagadougou, Burkina Faso: the small village of Noungou where humans outnumber cattle, and the nearby Fulani settlement of Loumbila where cattle outnumber humans. Collections made inside human dwellings were supplemented in 1992 by outdoor-resting samples from artificial pit-shelters. Indoor-resting An. funestus were also collected in November 1992 and November 1994 in four villages of the Banfora area (southern Burkina Faso) and in a sudanese-sahelian village in northern Burkina Faso (Tougouri). Half-gravid female sub-samples were preserved in carnoy's fixative and processed for polytene chromosome analysis. The material from the two villages near Ouagadougou was analysed by ELISA to know (i) the human/animal origin of the blood meal; (ii) the infectivity for Plasmodium falciparum malaria; and (iii) the possible correlation of these parameters with chromosomal variants. A total of 1416 An. funestus could be scored for the whole polytenic complement, while the origin of the blood meal and circumsporozoite protein (CSP) positivity were asserted from 1076 and 1154 specimens, respectively. With a few exceptions, four polymorphic paracentric inversions (3a, 3b, 2a and 5a in decreasing order of frequency) were observed in all populations. Inversion 2s, whose breaking points include those of inversion 2a, was found only as the heterokaryotype 2s/+ floating at an overall frequency of 3.7% in two villages of the Banfora area and in the two sites near Ouagadougou. Two heterokaryotypes 2a/t out of 186 scored specimens were observed in different years from one village of the Banfora area. Wide variations in inversion frequencies were observed among the samples without consistent geographical or temporal clines. Highly significant departures from Hardy-Weinberg equilibrium were recorded for inversions 3a and 3b in most samples, with the alternative homokaryotypes (standard and inverted) significantly more frequent than expected. Conversely, inversion 5a was in Hardy-Weinberg equilibrium in most samples, whereas the 2a-s inversion system was intermediate between these extremes. However, a deficit of heterokaryotypes was apparent practically in all samples. Significantly higher frequencies of the standard homokaryotypes were recorded (i) in the exophilic samples collected in Loumbila for arrangement 3a; (ii) in the animal-fed sub-sample collected outdoors in Noungou vs. the parallel human-fed sub-sample for arrangements 2a-s, 3a, and 3b, or vs. the samples obtained from indoor catches in both Loumbila and Noungou in the case of inversion 3a; (iii) in the December CSP-negative sub-sample from Loumbila vs. the parallel CSP-positive sub-sample for arrangement 2a. A plausible working hypothesis is that An. funestus in Burkina Faso includes two taxonomic units, one of which is mainly monomorphic standard with most inverted arrangements floating at very low frequencies, and probably uniquely characterised by arrangement 2s, while the other taxon is nearly fixed for arrangement 3ab and polymorphic for all the other inversions at intermediate to high frequencies. The latter would be characterised by a higher vectorial capacity and would probably correspond to An. funestus s.s. from East Africa. About the former hypothetical taxon, its endophily and anthropophily appear less marked and its relationship with other members of the An. funestus subgroup will require specific investigations.

Interethnic differences in the humoral response to non-repetitive regions of the Plasmodium falciparum circumsporozoite protein

We analyzed the humoral immune response to the amino- (amino acids 22-125) and carboxy-terminal (amino acids 289-390) non-repetitive domains of the Plasmodium falciparum circumsporozoite protein (PfCSP) in individuals belonging to three west African ethnic groups (the Fulani, Mossi, and Rimaibé) living in the same conditions of hyperendemic transmission in a Sudan savanna area of Burkina Faso. Previous surveys conducted in the same area showed obvious interethnic differences in the susceptibility and immune reactivity to malaria, with the Fulani showing lower infection and disease rates and higher humoral responses to various P. falciparum antigens than sympatric ethnic groups. A total of 764 subjects (311 Mossi, 273 Rimaibé, and 180 Fulani) of all age classes were tested. The total mean +/- SE anti-(CSPf-N-term) and anti-(CSPf-C-term) seroprevalences were 65.6 +/- 1.7% and 57.0 +/- 1.8%, respectively. These seroprevalences were lower than that recorded in the same sample for the central (NANP)40 repetitive domain (88.3 +/- 1.2%). As previously reported for other P. falciparum antigens (PfCSP-(NANP)40, thrombospondin-related anonymous protein, merozoite surface protein-1, Pf155-ring-infected erythrocyte surface antigen, and Pf332), in spite of similar exposure to malaria, the Fulani showed higher immune reactivity than sympatric populations for both antigens tested. Our results confirm the presence of B cell epitopes in the non-repetitive regions of the PfCSP; moreover a further evidence of interethnic differences in the capacity to mount humoral responses against P. falciparum malaria was obtained. The assessment of the biological basis of interethnic heterogeneities in the susceptibility and in the humoral immune responses to malaria appears relevant in the development of anti-malaria vaccines.

The clay feet of the malaria giant and its African roots: hypotheses and inferences about origin, spread and control of Plasmodium falciparum

Grassi's allegory of the fragile feet of clay of the malaria giant applies particularly to Plasmodium falciparum marginal populations in temperate climates such as those that spread within the last three thousand years in the Mediterranean area through their close association with non diapausing vectors of the Anopheles maculipennis complex. The winter survival of the vector and the successful completion of the sporogonic cycle depended on the availability of the house environment to the mosquito. The fragility of the parasite's cycle became especially evident with the crucial impact of indoor-sprayed residual insecticides resulting in very rapid malaria eradication. The malaria giant showed to possess much more solid feet in the Tropics where P. falciparum eventually reached an exceptionally stable endemicity in sub-Saharan Africa due to a vectorial system which produces inoculation rates far higher than the minimum necessary to saturate human populations. This very high transmissibility resulting from recent human-dependent speciation processes in Afrotropical Anopheles mosquitoes (namely the emergence in the Neolithic period of specifically anthropophilic taxa in the An. funestus and An. gambiae complexes) had probably a key influence on the origin of the modern P. falciparum from an ancestral, less pathogenic, taxon. It is hypothesised that under the prevalence of multiple inoculation during epidemic flashes, a fast growing, aggressive strain responsible for acute, short-lived infections was selected. This quickly replaced the ancestral taxon and spread all over the world taking advantage of previous Anopheles radiation and of the demographic expansion following the agricultural revolution. Dealing with the African 'roots' of the malaria giant means to face both the exceptional stability of the parasite cycle and the risk of disrupting the human natural response with unsustainable interventions. Most efforts should be concentrated in the support and improvement of the available anti-disease strategies whereas the development of effective anti-infection strategies should be mainly pursued through reasonably diversified research programmes and well monitored pilot interventions within a long-term perspective. The aim is to discover and test new anti-malarial tools which either alone or, more probably, integrated with the available measures, could allow the interruption of transmission. In most Afrotropical hyper- and holoendemic zones, once given full priority to strengthening disease control, P. falciparum eradication appears the only realistic anti-infection objective, unless it is demonstrated that progress can be achieved in these epidemiological zones through sustainable and cost-effective intermediate steps based on the reduction of infection prevalence.

Are chromosomal inversions induced by transposable elements? A paradigm from the malaria mosquito Anopheles gambiae

Chromosomal rearrangements abound in nature and can be studied in detail in organisms with polytene chromosomes. In Drosophila and in Anopheline mosquitoes most speciation processes seem to be associated with the establishment of chromosomal rearrangements, particularly of paracentric inversions. It is not known what triggers inversions in natural populations. In the laboratory inversions are commonly generated by X-rays, mutagens or after the activity of certain transposable elements (TEs). The Anopheles gambiae complex is comprised of six sibling species, each one characterized by the presence of fixed paracentric inversions on their chromosomes. Two of these, An. gambiae s.s. and An. arabiensis, are the most important vectors of human malaria and are structured into sub-populations, each carrying a characteristic set of polymorphic chromosomal inversions. We have cloned the breakpoints of the naturally occurring polymorphic inversion In(2R)d' of An. arabiensis. Analysis of the surrounding sequences demonstrated that adjacent to the distal breakpoint lies a transposable element that we called Odysseus. Characteristics of Odysseus' terminal region and its cytological distribution in different strains as well as within the same strain indicate that Odysseus is an actively transposing element. The presence of Odysseus at the junction of the naturally occurring inversion In(2R)d' suggests that the inversion may be the result of the TEs activity. Cytological evidence from Drosophila melanogaster has also implicated the hobo transposable element in the generation of certain Hawaiian endemic inversions. This picture supports the hypothesis of the important role of TEs in generating natural inversions.

Different response to Plasmodium falciparum in west African sympatric ethnic groups: possible implications for malaria control strategies

The comparison of malaria indicators among populations with different genetic backgrounds and uniformly exposed to the same parasite strains, is one of the approaches to the study of human heterogeneities in the response to the infection. The results of our comparative studies conducted in Burkina Faso, West Africa, showed consistent interethnic differences in Plasmodium falciparum infection rates, malaria morbidity, prevalence and levels of antibodies to various P. falciparum antigens, and genetic background. The differences in the immune response were not explained by the entomological observations which indicated substantially uniform exposure to infective bites. The presence in the same epidemiological context of individuals characterized by different immune reactivity to malaria represents an ideal opportunity to study the possible relationships between the baseline level of anti-malaria immunity of a population and the protective efficacy of control measures based on the reduction of transmission. In spite of similar reduction of entomological inoculation rates obtained by permethrin-impregnated curtains, ethnic- and age-dependent efficacy was observed. These studies demonstrate the existence of marked interethnic differences in the susceptibility to P. falciparum malaria, probably involving the genetic regulation of humoral immune responses. These differences should be considered in the development of anti-malaria vaccines and in the evaluation and application of malaria control strategies.

Salivary gland-specific gene expression in the malaria vector Anopheles gambiae

Molecular studies on the tissue-specific gene expression in the salivary glands of Anopheles gambiae may provide useful tools for the development of new strategies for the control of the most efficient malaria vector in the sub-Saharan Africa. We summarize here the results of a recent investigation focused on the isolation of secreted factors and putative receptors from the salivary glands of An. gambiae. Using the Signal Sequence Trap technique we have identified the first cDNAs specifically expressed in the An. gambiae salivary glands. Among these, four are exclusively expressed in female glands and encode factors presumably involved in blood-feeding, whereas two other cDNAs seem to be expressed both in male and in female glands and are likely implicated in sugar-feeding. Homologues of genes previously identified in the yellow fever mosquito Aedes aegypti, like the apyrase and D7, as well as novel salivary gland-specific cDNAs, were identified. The isolation and characterization of promoter sequences from the corresponding genes may prove useful for the expression of anti parasitic agents in the salivary glands of transgenic mosquitoes.