136 research outputs found
Studies in epidemiology and seroepidemiology of visceral leishmaniasis in Iraq.
Get PDFA defined population
was
studied
over
a
period
of
7
months
to
elucidate the epidemiology of visceral
leishmaniasis in Iraq,
using
serological methods as a screening
test.
Seroepidemiological
methods
were
also used in the search for a
canine reservoir
of
infection
and
the tests
used were studied in defined animal
systems
and
in
confirmed
human
cases.
A cross-sectional survey was
made
of
the
population
of
a
defined
rural area of 300 km2, south
of
Baghdad. It included
19
villages with
1,171 houses and a total population
of
9,889.
Houses
were
mapped
and a
census completed. The 3,403 persons
under
7
years
of
age
were
screened
using two serological tests for
visceral leishmaniasis: indirect fluorescent antibody test (IFAT) and enzyme-linked
immunosorbent
assays
(ELISA).
Seropositive children were fully examined
clinically and
by the leishmanin
test. The blood picture and
serum proteins
were
determined
and,
in the
absence of clinical signs, follow-up was
by
monthly
serological
examination.
Symptomatic children were admitted
to
hospital for bone
marrow
biopsy.
Results showed a range from subclinical cases
defined
only
by
sero-conversion through to severe
disease
needing
hospital treatment
and
with
a
high mortality.
A repeat survey of
the
same
child population after
7
months
showed serological changes following the
main
transmission
season.
66 of the parasitologically
confirmed sero-positive
cases
from
this area and elsewhere in the
endemic region
were
examined, and
in
some,
monthly serology was determined at
domiciliary follow-up. IFAT
was
found
to be more sensitive than ELISA. 33%
of cases of visceral
leishmaniasis
were
found to revert to negative
within
9
months
of
treatment.
435 hospital inpatients with
a variety
of
diagnoses
were
studied
to determine the specificity of
tests.
ELISA
was
found
of
greater
specificity than IFAT. These cases
included
124
clinically suspected
leishmaniases of which 45 were subsequently culture-positive.
A longitudinal serological study
was carried
out
in inbred
mice
of varying genetically determined susceptibility
to infection.
All
innately
susceptible mice were seropositive by
day
50
and
the titre
continued
to
increase until the end of the experiment at
day
130
regardless
of
the
parasitological course of infection. In a search for the postulated canine
reservoir
of visceral
leishmaniasis 151 jackals and 65 dogs, largely
strays,
were
studied
parasitologically and serologically.
Neither from these
nor
from
a
limited
sample of rodents could the parasite
be isolated, though
several
jackals
were seropositive.
The results clarify
the
epidemiology
of
visceral
leishmaniasis
but do not demonstrate an animal
reservoir
unequivocally.
They
do however
define criteria which any satisfactory quantitative
hypothesis
of
transmission needs to fulfil
Evaluation of first generation vaccines against human leishmaniasis and the implication of Leishmanin Skin Test (LST) response in disease prevalence
Get PDFThis study reports the detailed analysis of the data from ten different clinical trials of
first generation prophylactic vaccines (FGV) against leishmaniasis. With the
exception of one trial, clinical trials of leishmaniasis FGV's have failed to show
efficacy. However, some trials have indicated reduced infection rates in the subset of
participants whose leishmanin skin test (LST) had converted after vaccination.
Additionally boys were observed to be protected more than girls by the vaccine in one
trial.
Objectives
One objective of this study was to re-assess the effectiveness of FGV's in providing
protection. This was done both, overall, with all vaccines and trials included and
separately, in more homogeneous subsets of clinical trials. The justification for this
re-assessment was the potential ability of the combined analysis to bypass the trialspecific
limitations of individual studies and bring about the advantages of a larger
sample size. Efficacy was also evaluated in different demographic groups identified
by age, gender and endemic/non-endemic origin of participants. In addition to
efficacy, immunological response (indicated by LST) to leishmanial antigen
introduced by vaccination or naturally was evaluated in different demographic groups.
LST reaction is an indication of delayed-type hypersensitivity (DTH) and has been
used by investigators to assess exposure. Another objective of this study was to
assess the merit of LST as a marker of infection and/or immunity in endemic and nonendemic
populations.
Findings
Vaccine efficacy:
Vaccine efficacy was re-evaluated by meta-analysis. Results were consistent with the
conclusion in most clinical trials that FGV's were not efficacious - L. amazonensis
vaccines in South America were possibly the only exception. Restricting the analysis
to more homogeneous subsets of trials (similar vaccine, same causative parasite, etc)
did not change this overall conclusion. Furthermore, overall no evidence of
protection associated with LST conversion after vaccination in the vaccine arm was
observed. Additionally, different demographic groups were not different in their
infection rates after vaccination.
Other factors associated with lower incidence:
In ALM+BCG (Autoclaved L. major + Bacille Calmette-Guerin) vaccine trials in Iran,
it was observed that immunological reactivity (LST>0) 80 days after vaccination was
associated with reduced incidence if LST measurement one year after study injection
were LST≥5. This observation, was independent of the study treatment (i.e., no
difference observed between the ALM+BCG and BCG alone arms). This could
indicate a level of BCG related protection.
Reduced infection rate associated with study participation (again, regardless of
treatment) was observed in ALM+BCG trials in all participants of endemic origin
13
with previous natural exposure (screening LST≥5). This confirms the protective
effect of endemic exposure associated with LST conversion.
Under endemic conditions, trials conducted with non-endemic participants showed
higher rates of infection than those with endemic participants; another observation
suggesting the effect of endemic immunity.
Exposure and LST response:
By design, two of the trials used in this analysis enrolled volunteers with LST>0 at
screening. This allowed studying natural exposure in demographic groups.
Inhabitants of an endemic focus were observed to have a different LST profile (more
frequent with smaller induration) from residents of a newly endemic focus.
LST as a marker of immunity:
LST measurement changes as a result of exposure to leishmanial antigen. However,
LST does not provide a reliable marker of immunity independently of the information
about factors that gave rise to it. For example, LST converts in a far greater percent of
vaccine arm participants compared to BCG participants. However, this difference is
not associated with better protection. Additionally, LST is subject to significant
variability from measurement to measurement. For example, in Borkhar, 38% of
participants with LST>0 at screening, had LST=0 eighty days after vaccination. This
could constitute a source of misclassification of previous exposure. Also, LST
reflects immune system stimulation due to different factors: natural exposure,
vaccination and even BCG could affect the LST response. Therefore, unless the
reasons for a reactive LST are known, LST cannot be used as a marker of immunity.
Thesis organization
This thesis is organized into 8 Chapters:
CHAPTER 1 - Background
CHAPTER 2 - Research objectives and methods
CHAPTER 3 - Efficacy of killed whole-parasite vaccines in prevention of
leishmaniasis - a meta-analysis
CHAPTER 4 - Prophylactic efficacy of whole-parasite killed vaccines in
demographic subgroups
CHAPTER 5 - Immunological response (measured by LST) in demographic
subgroups to the leishmanial antigen introduced by vaccine or
natural exposure
CHAPTER 6 - LST response as a correlate of immunity
CHAPTER 7 - Discussion
CHAPTER 8 - Conclusions and recommendations for further research
14
ZUSAMMENFASSUNG
Diese Studie berichtet über die detaillierte Datenanalyse von 10 verschiedenen
klinischen Studien der prophylaktischen Impfstoffe der ersten Generation (Englisch:
„first generation prophylactic vaccines“ FGV) gegen Leishmaniose. Mit Ausnahme
von einem Versuch haben klinische Studien von Leishmaniose FGVs bisher keine
Wirksamkeit gezeigt. Jedoch haben einige Versuche verringerte Infektionsraten in
einer Untergruppe der Versuchsteilnehmer gezeigt, deren Leishmaniose Hauttest
(Englisch: „leishmanin skin test“ LST) sich nach der Schutzimpfung umgewandelt
hatte. Des Weiteren wurde in einer Studie beobachtet, dass Jungen besser von dem
Impfstoff geschützt werden, als Mädchen.
Zielsetzung
Eine Zielsetzung dieser Studie war es, neu einzuschätzen, inwieweit FGV einen
wirksamen Impfschutz herstellen können. Dieses wurde in zwei Gruppen untersucht:
insgesamt mit allen Impfstoffen und allen Versuchen zusammen, und separat mit
homogeneren Untergruppen klinischer Studien. Die Rechtfertigung für diese Studie
war die Möglichkeit der kombinierten Analyse, die Versuchs-spezifischen
Beschränkungen der einzelnen Studien überbrückt sowie die Vorteile einer größeren
Stichprobe. Die Wirksamkeit wurde in den verschiedenen demographischen Gruppen
ausgewertet, die durch Alter, Geschlecht und endemischen/nicht-endemischen
Ursprung der Teilnehmer bestimmt wurden. Zusätzlich zur Wirksamkeit wurde die
immunologische Reaktion zum Leishmaniosis Antigen (angezeigt durch LST), das
durch Schutzimpfung oder natürlich eingeführt wurde, in den verschiedene
demographischen Gruppen ausgewertet. Die LST-Reaktion ist ein Indiz für eine
verzögerte Überempfindlichkeit (Englisch: „delayed-type hypersensitivity” DTH) und
wird in Studien verwendet, um eine Exposition festzustellen.
Eine weitere Zielsetzung dieser Studie war, den Benefit von LST als Markierung der
Infektion und/oder der Immunität in den endemischen und nicht-endemischen
Gruppen zu evaluieren.
Ergebnisse
Wirksamkeit des Impfstoffes:
Die Wirksamkeit des Impfstoffes wurde durch eine Meta-Analyse neu bewertet. Das
Ergebnis der Meta-Analyse deckt sich mit den Schlussfolgerungen der meisten
klinischen Studien, die FGVs als nicht wirkungsvoll bewerten. Die wahrscheinlich
einzige Ausnahme bilden die L. Amazonensis-Impfstoffe in Südamerika. Die
Beschränkung der Analyse auf homogenere Untergruppen der Studien (ähnlicher
Impfstoff, der gleiche kausale Parasit, usw.) erbrachte keine Änderung der
Schlussfolgerung. Darüber hinaus wurde in der Impfgruppe beobachtet, dass die
Umwandlung des LST-Tests nach Impfung nicht mit einem Impfschutz assoziiert ist.
Zusätzlich unterschieden sich die verschiedenen demographischen Gruppen nicht in
ihren Infektionsraten nach der Schutzimpfung.
15
Andere Faktoren, die mit geringer Inzidenz assoziiert sind:
Bei Versuchen mit dem ALM+BCG (Autoklavierten L. major + Bacille Calmette-
Guerin)-Impfstoff im Iran wurde beobachtet, dass die immunologische Reaktion
(LST> 0) 80 Tage nach der Impfung mit einer verringerten Inzidenz verbunden war,
wenn der LST ein Jahr nach der Impfung LST≥5 war. Dieses Ergebnis war
unabhängig von der Art der Impfung (d.h., kein Unterschied zwischen den
ALM+BCG und nur-BCG Gruppen). Dieses könnte ein gewisses Mass eines BCGbezogenen
Schutzes anzeigen.
Die verringerte Infektionsrate, die mit Studienteilnahme verbunden ist (wiederum
unabhängig von der Behandlung) wurde in den ALM+BCG- Versuchen in allen
Teilnehmern der endemischen Gruppe mit vorangegangener natürlicher Exposition
beobachtet (LST≥5). Dieses bestätigt den schützenden Effekt der endemischen
Exposition verbunden mit LST-Umwandlung.
Unter endemischen Bedingungen zeigten die Versuche, die mit nicht-endemischen
Teilnehmern durchgeführt wurden eine höhere Infektionsrate, als die mit endemischen
Teilnehmern; eine weitere Beobachtung, die auf den Effekt der endemischen
Immunität hinweist.
Exposition und LST-Antwort:
Zwei der Studien, die in dieser Analyse untersucht wurden, hatten Freiwillige mit
einem LST>0 eingeschlossen. Dieses ermöglichte die Untersuchung natürlicher
Exposition in den demographischen Gruppen. Es wurde beobachtet, dass Bewohner
einer endemischen Region ein anderes LST-Profil aufwiesen (häufiger mit geringerer
Verhärtung), als Bewohner eines neu entstandenen endemischen Gebietes.
LST als Immunitäts-Marker:
Die Messung von LST ändert sich als Resultat von einer Belastung durch das
Leishmaniose-Antigen. Jedoch liefert LST keine zuverlässige Markierung der
Immunität unabhängig der Informationen über Faktoren, die sie verursachten. Zum
Beispiel wandelt LST sich zu einem weit größeren Prozentsatz in den Impf-Gruppen
um, als BCG-Gruppen. Jedoch ist dieser Unterschied nicht mit besserem Schutz
verbunden. Darüber hinaus ist der LST-Test sehr variabel: Zum Beispiel hatten in
Borkhar 38% der Teilnehmern mit einem LST>0 bei den Vortests, einen LST von 0
achtzig Tage nach der Impfung. Dieses könnte eine Quelle für Fehlklassifizierung der
vorhergehenden Expositiondarstellen. Ebenso spiegelt der LST die
Immunsystemanregung aufgrund verschiedener Faktoren wider: natürliche Exposition,
Impfung, und sogar BCG konnten die LST-Antwort beeinflussen. Folglich eignet sich
der LST nicht als Immunitäts-Marker; es sei denn, die Gründe für einen reagierenden
LST sind hinreichend bekannt.
Gliederung
Diese Arbeit ist in acht Kapitel gegliedert:
KAPITEL 1 - Hintergrund
16
KAPITEL 2 - Forschungszielsetzungen und -methoden
KAPITEL 3 – Die Wirksamkeit von abgetöteten Voll-Parasit-Impfstoffen in der
Prävention der Leishmaniose - eine Meta-Analyse
KAPITEL 4 – Die prophylaktische Wirksamkeit des Voll-Parasit-Impfstoffes in
den demographischen Untergruppen
KAPITEL 5 – Immun-Reaktion (gemessen durch LST) in den demographischen
Untergruppen zum Leishmaniose-Antigen durch Impfstoffe oder
natürliche Exposition
KAPITEL 6 - LST-Antwort als Korrelat der Immunität
KAPITEL 7 - Diskussion
KAPITEL 8 - Zusammenfassungen und Empfehlungen für weitere Forschun
A Leishmania infantum FML-ELISA for the Detection of Symptomatic and Asymptomatic Canine Visceral Leishmaniasis in an Endemic Area of Iran
Get PDFBackground: Visceral leishmaniasis (VL) is caused by Leishmania infantum in
Mediterranean basin and is an endemic disease in some parts of Iran. Canines are the main
reservoirs of VL in most of the endemic areas. Different serological methods have been
introduced for diagnosis of canine visceral leishmaniasis (CVL). Objective: In this survey a
Fucose-Mannose Ligand (FML) ELISA, using native L. infantum antigen, was developed and
its validity for detection of infected dogs in comparison with direct agglutination test (DAT)
and PCR was evaluated. Methods: Blood samples of sixty ownership dogs (≤ 3 years old)
were collected from Meshkin-shahr district in Ardabil province, North-west of Iran. Sera
were separated for serological assays (DAT and FML-ELISA) and the buffy coats were
collected for molecular evaluation. Results: Two out of the 60 (3.33%) samples were found
to be positive (antibody titer of ≥ 1/320) in DAT while seven of the 60 (11.66%) samples
were positive by FML-ELISA. Nine out of 60 (15%) buffy coat samples showed a band about
680 bp indicative of L. infantum in PCR. Three out of 60 dogs had Kala-azar symptoms and
were positive by PCR and FML-ELISA, while two of these three dogs had antibody titers
>1/320 in their serum samples. The sensitivity and specificity of FML-ELISA for the
detection of CVL in both symptomatic and asymptomatic dogs were found to be 77.8% and
100%, respectively. Conclusion: Considering the acceptable sensitivity and high specificity
of FML-ELISA, use of this serological method can be recommended for epidemiological
surveys of CVL
Effect of village-wide use of long-lasting insecticidal nets on visceral Leishmaniasis vectors in India and Nepal: a cluster randomized trial.
Get PDFBACKGROUND: Visceral leishmaniasis (VL) control in the Indian subcontinent is currently based on case detection and treatment, and on vector control using indoor residual spraying (IRS). The use of long-lasting insecticidal nets (LN) has been postulated as an alternative or complement to IRS. Here we tested the impact of comprehensive distribution of LN on the density of Phlebotomus argentipes in VL-endemic villages. METHODS: A cluster-randomized controlled trial with household P. argentipes density as outcome was designed. Twelve clusters from an ongoing LN clinical trial--three intervention and three control clusters in both India and Nepal--were selected on the basis of accessibility and VL incidence. Ten houses per cluster selected on the basis of high pre-intervention P. argentipes density were monitored monthly for 12 months after distribution of LN using CDC light traps (LT) and mouth aspiration methods. Ten cattle sheds per cluster were also monitored by aspiration. FINDINGS: A random effect linear regression model showed that the cluster-wide distribution of LNs significantly reduced the P. argentipes density/house by 24.9% (95% CI 1.80%-42.5%) as measured by means of LTs. INTERPRETATION: The ongoing clinical trial, designed to measure the impact of LNs on VL incidence, will confirm whether LNs should be adopted as a control strategy in the regional VL elimination programs. The entomological evidence described here provides some evidence that LNs could be usefully deployed as part of the VL control program. TRIAL REGISTRATION: ClinicalTrials.gov CT-2005-015374
Epidemiology of Leishmania donovani infection in high-transmission foci in Nepal.
No full textOBJECTIVE: Nepal reports a visceral leishmaniasis (VL) incidence of 5 per 10 000 per year on the basis of notification by health facilities, but little community-based epidemiological information exists. We report data on prevalence rates of Leishmania donovani infection in ten communities in East Nepal. METHODS: Ten clusters with highest VL incidence rates were purposefully selected in Nepal. All households were mapped and socio-demographic data and data on past VL incidence were collected. An exhaustive serological survey was performed of individuals aged >2 years, by collecting finger prick blood on filter paper in November-December 2006. The samples were tested by direct agglutination, and a titre >or=1:1600 was taken as marker of infection. A generalized estimating equation (GEE) model was used to assess risk factors for Direct Agglutination Test (DAT) positivity taking into account the clustering at household and village level. RESULTS: The sero-survey (n = 5397) showed an infection prevalence rate of 9%, (range 5-15% per cluster) with higher prevalence in men (9.9%) than in women (8.3%) (P = 0.049). Male gender, increasing age and poverty were significant risk factors in the final GEE model. CONCLUSION: Leishmania infection rate in high-transmission areas in Nepal is associated with gender, age and socio-economic status
Longlasting insecticidal nets for prevention of Leishmania donovani infection in India and Nepal: paired cluster randomised trial.
Get PDFOBJECTIVE: To test the effectiveness of large scale distribution of longlasting nets treated with insecticide in reducing the incidence of visceral leishmaniasis in India and Nepal. DESIGN: Paired cluster randomised controlled trial designed to detect a 50% reduction in incidence of Leishmania donovani infection. SETTING: Villages in Muzaffarpur district in India and Saptari, Sunsari, and Morang districts in Nepal. PARTICIPANTS: 13 intervention and 13 control clusters. 12 691 people were included in the analysis of the main outcome (infection), and 19 810 were enrolled for the secondary (disease) end point. INTERVENTION: Longlasting insecticidal nets (treated with deltamethrin) were distributed in the intervention clusters in December 2006. MAIN OUTCOME MEASURES: Infection was determined by direct agglutination test at 12 and 24 months after the intervention in those who had negative results (titre <1:1600) at baseline. The effect estimate was computed as the geometric mean of the risk ratios for seroconversion for each cluster pair (net/no net), with its 95% confidence interval. Formal tests of effect of no intervention were obtained with a paired t test. RESULTS: There was no significant difference in the risk of seroconversion over 24 months in intervention (5.4%; 347/6372) compared with control (5.5%; 345/6319 people) clusters (risk ratio 0.90, 95% confidence interval 0.49 to 1.65) nor in the risk of clinical visceral leishmaniasis (0.99, 0.46 to 1.40). Adjustment for covariates did not alter these conclusions. CONCLUSIONS: There is no evidence that large scale distribution of longlasting insecticidal nets provides additional protection against visceral leishmaniasis compared with existing control practice in the Indian subcontinent. The observed effect was small and not significant, though the confidence intervals did not exclude a 50% change in either direction. TRIAL REGISTRATION: Clinical Trials NCT 2005-015374
Risk factors for visceral leishmaniasis in India: further evidence on the role of domestic animals.
No full textOBJECTIVE: Studies investigating risk factors for visceral leishmaniasis (VL) on the Indian Subcontinent have shown contradictory results related to the role of domestic animals. In some studies having animals in or around the house was a risk factor, in others it was protective. We investigated the specific hypothesis that keeping domestic animals inside the house at night is a risk factor for VL. METHODS: Individually matched case-control study. All patients with VL diagnosed in the study area in Bihar, India between March 1st, 2007 and December 1st, 2008 were eligible. For each case, we selected two random controls, with no history of previous VL; matched on sex, age group and neighbourhood. Patients and controls were subjected to a structured interview on the main exposure of interest and potential confounders; a conditional logistic regression model was used to analyse the data. RESULTS: We enrolled 141 patients and 282 controls. We found no significant associations between VL and keeping domestic animals inside the house (OR of 0.88 for bovines and 1.00 for 'any animal') or ownership of domestic animals (OR of 0.97 for bovines and 1.02 for 'any animal'). VL was associated with housing conditions. Living in a thatched house (OR 2.60, 95% CI 1.50-4.48) or in a house with damp floors (OR 2.60, 95% CI 1.25-5.41) were risk factors, independently from socio economic status. CONCLUSION: Keeping animals inside the house is not a risk factor for VL in Bihar, India. Improving housing conditions for the poor has the potential to reduce VL incidence
Development of an enzyme-linked immunosorbent assay to identify host-feeding preferences of Phlebotomus species (Diptera: Psychodidae) in endemic foci of visceral leishmaniasis in Nepal.
No full textAnthroponotic visceral leishmaniasis, transmitted by Phlebotomus argentipes Annandale & Brunetti (Diptera: Psychodidae) sand flies, is regarded as a major problem of public health importance in the Indian subcontinent. Understanding the feeding behavior of the vector can be used to investigate changes in human-vector contact during intervention programs. An enzyme-linked immunosorbent assay (ELISA) was modified to make it suitable to identify the origin of P. argentipes and Phlebotomus papatasi Scopoli (Diptera: Psychodidae) blood meals. The sensitivity and specificity of the precipitin ring test and ELISA were compared, as well as the stability of the tests across different stages of blood meal digestion. The ELISA was more sensitive and specific than the precipitin test for identifying the sources of blood meals. When using the ELISA method with a plate reader, it was possible to obtain 100% sensitivity and specificity. When comparing the techniques across digestion stages, it was found that there was a drop in sensitivity, 48 and 72 h postblood meal for precipitin and visually read ELISA, respectively. However, the sensitivity of the ELISA using a plate reader was not altered by the digestion time. The feeding habits of P. argentipes and P. papatasi from the Terai region of Nepal, determined by the ELISA developed, showed P. papatasi to be highly anthropophilic, and P. argentipes appeared to feed both on humans and animals, in particular bovines
Diabetic Nephropathy and COVID-19: The Potential Role of Immune Actors
Get PDFNowadays, type II diabetes mellitus, more specifically ensuing diabetic nephropathy, and severe COVID-19 disease are known to be closely associated. The exact mechanisms behind this association are less known. An implication for the angiotensin-converting enzyme 2 remains controversial. Some researchers have started looking into other potential actors, such as neuropilin-1, mitochondrial glutathione, vitamin D, and DPP4. In particular, neuropilin-1 seems to play an important role in the underlying mechanism linking COVID-19 and diabetic nephropathy. We suggest, based on the findings in this review, that its up-regulation in the diabetic kidney facilitates viral entry in this tissue, and that the engagement of both processes leads to a depletion of neuropilin-1, which was demonstrated to be strongly associated with the pathogenesis of DN. More studies are needed to confirm this hypothesis, and research should be directed towards elucidating the potential roles of all these suggested actors and eventually discovering new therapeutic strategies that could reduce the burden of COVID-19 in patients with diabetic nephropathy
Serological markers for Leishmania donovani infection in Nepal: agreement between direct agglutination test and rK39 ELISA
No full textVisceral leishmaniasis (VL) is an important vector-borne disease caused by Leishmania donovani in the Indian subcontinent. The actual incidence and role of asymptomatic infections in the region are not well known. We used the direct agglutination test (DAT) and the rK39 ELISA as L. donovani infection markers in 10 VL endemic villages in Nepal. DAT titre distribution showed two subgroups in the population (infected and non-infected individuals), while rK39 did not. The agreement between both tests was moderate (kappa = 0.53; 95% CI 0.49-0.57). More research is needed to develop validated markers for Leishmania infection
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