Correction: Onchocerciasis: Target product profiles of in vitro diagnostics to support onchocerciasis elimination mapping and mass drug administration stopping decisions

[This corrects the article DOI: 10.1371/journal.pntd.0010682.].

[Susceptibility Of ABOS Blood Groups To COVID-19 At The National Institute Of Public Health (INSP) Of Mali In 2020]

INTRODUCTION

Several authors have suggested an association between the ABO system (ABOS) and the risk of SARS CoV-2 infection. The objective of the present study was to identify the susceptibility of ABOS blood groups to COVID-19 at the National Institute of Public Health (INSP) of Mali.

MATERIAL AND METHODS

This was an unpaired case-control study. The cases (402) were COVID-19 patients, and the controls (5438) were Muslim pilgrims, all of whom had undergone ABO blood grouping at the INSP. Logistic regression was performed to identify factors associated with SARS-CoV-2 infection status using SPSS version25 software.

RESULTS

Blood types had the following frequencies: O(34%), B(30%), A(28%), AB(8%) for cases and O(42%), B(27%), A(25%), AB(6%) for controls. COVID-19 positive status was not significantly associated with blood groups A(oR=1.17; CI95%[0.93-1.47]), B(OR=1.11; CI95%[0.89-1.39]) and AB(OR=1.41; CI95%[0.97-2.06]). However, blood group O subjects were 28 times less likely to have COVID-19 than non-O(OR=0.72; CI95%[0.58-0.89).

CONCLUSION

The results show that blood group O individuals were less likely to have SARS CoV-2 infection than non-O individuals. This should not affect the use of barrier measures in ABOS groups.

Onchocerciasis: Target product profiles of in vitro diagnostics to support onchocerciasis elimination mapping and mass drug administration stopping decisions

In June 2021, the World Health Organization (WHO), recognizing the need for new diagnostics to support the control and elimination of onchocerciasis, published the target product profiles (TPPs) of new tests that would support the two most immediate needs: (a) mapping onchocerciasis in areas of low prevalence and (b) deciding when to stop mass drug administration programs. In both instances, the test should ideally detect an antigen specific for live, adult O. volvulus female worms. The preferred format is a field-deployable rapid test. For mapping, the test needs to be ≥ 60% sensitive and ≥ 99.8% specific, while to support stopping decisions, the test must be ≥ 89% sensitive and ≥ 99.8% specific. The requirement for extremely high specificity is dictated by the need to detect with sufficient statistical confidence the low seroprevalence threshold set by WHO. Surveys designed to detect a 1–2% prevalence of a given biomarker, as is the case here, cannot tolerate more than 0.2% of false-positives. Otherwise, the background noise would drown out the signal. It is recognized that reaching and demonstrating such a stringent specificity criterion will be challenging, but test developers can expect to be assisted by national governments and implementing partners for adequately powered field validation.

River blindness, also known as onchocerciasis, affects 21 million people, predominantly in sub-Saharan Africa. For decades, the international community has fought this disease through mass drug administration (MDA) programs focused on controlling morbidity in areas of high prevalence. Now, as part of their 2021–2030 Roadmap for Neglected Tropical Diseases, the World Health Organization (WHO) has set an ambitious goal, shifting from controlling to eliminating onchocerciasis. This implies addressing areas of low infection prevalence. As a result, new diagnostics tools are required to identify and map areas of low onchocerciasis prevalence and to help decide where to initiate MDA. Similarly, new diagnostics are required to decide when the prevalence of onchocerciasis is sufficiently low to justify stopping MDA. A WHO-appointed independent panel, the Diagnostics Technical Advisory Group for Neglected Tropical Diseases, and its subgroup specific to onchocerciasis, have established the desired Target Product Profiles (TPPs) for such new tests. The TPPs were posted in June 2021 on the WHO website. This article describes the methodology used to produce the TPPs, with an emphasis on calculating the required sensitivity and specificity characteristics.

Seroreactivity of the Severe Acute Respiratory Syndrome Coronavirus 2 Recombinant S Protein, Receptor-Binding Domain, and Its Receptor-Binding Motif in COVID-19 Patients and Their Cross-Reactivity With Pre-COVID-19 Samples From Malaria-Endemic Areas

Despite the global interest and the unprecedented number of scientific studies triggered by the COVID-19 pandemic, few data are available from developing and low-income countries. In these regions, communities live under the threat of various transmissible diseases aside from COVID-19, including malaria. This study aims to determine the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroreactivity of antibodies from COVID-19 and pre-COVID-19 samples of individuals in Mali (West Africa). Blood samples from COVID-19 patients (n = 266) at Bamako Dermatology Hospital (HDB) and pre-COVID-19 donors (n = 283) from a previous malaria survey conducted in Dangassa village were tested by ELISA to assess IgG antibodies specific to the full-length spike (S) protein, the receptor-binding domain (RBD), and the receptor-binding motif (RBM436-507). Study participants were categorized by age, gender, treatment duration for COVID-19, and comorbidities. In addition, the cross-seroreactivity of samples from pre-COVID-19, malaria-positive patients against the three antigens was assessed. Recognition of the SARS-CoV-2 proteins by sera from COVID-19 patients was 80.5% for S, 71.1% for RBD, and 31.9% for RBM (p < 0.001). While antibody responses to S and RBD tended to be age-dependent, responses to RBM were not. Responses were not gender-dependent for any of the antigens. Higher antibody levels to S, RBD, and RBM at hospital entry were associated with shorter treatment durations, particularly for RBD (p < 0.01). In contrast, higher body weights negatively influenced the anti-S antibody response, and asthma and diabetes weakened the anti-RBM antibody responses. Although lower, a significant cross-reactive antibody response to S (21.9%), RBD (6.7%), and RBM (8.8%) was detected in the pre-COVID-19 and malaria samples. Cross-reactive antibody responses to RBM were mostly associated (p < 0.01) with the absence of current Plasmodium falciparum infection, warranting further study.

Serological Evaluation of Onchocerciasis and Lymphatic Filariasis Elimination in the Bakoye and Falémé Foci, Mali

Background

Ivermectin-based onchocerciasis elimination, reported in 2009–2012, for Bakoye and Falémé, Mali, supported policy-shifting from morbidity control to elimination of transmission (EOT). These foci are coendemic with lymphatic filariasis (LF). In 2007–2016 mass ivermectin plus albendazole administration was implemented. We report Ov16 (onchocerciasis) and Wb123 (LF) seroprevalence after 24–25 years of treatment to determine if onchocerciasis EOT and LF elimination as a public health problem (EPHP) have been achieved.

Methods

The SD Bioline Onchocerciasis/LF Ig[immunoglobulin]G4 biplex rapid diagnostic test (RDT) was used in 2186 children aged 3–10 years in 13 villages (plus 2 hamlets) in Bakoye and in 2270 children in 15 villages (plus 1 hamlet) in Falémé. In Bakoye, all-age serosurveys were conducted in 3 historically hyperendemic villages (1867 individuals aged 3 -78 years).

Results

In Bakoye, IgG4 seropositivity was 0.27% (95% confidence interval [CI] = .13%–.60%) for both Ov16 and Wb123 antigens. In Falémé, Ov16 and Wb123 seroprevalence was 0.04% (95% CI = .01%–.25%) and 0.09% (95% CI = .02%–.32%), respectively. Ov16-seropositive children were from historically meso/hyperendemic villages. Ov16 positivity was <2% in ≤14 year-olds, and 16% in ≥40 year-olds. Wb123 seropositivity was <2% in ≤39 year-olds, reaching 3% in ≥40 year-olds.

Conclusions

Notwithstanding uncertainty in the biplex RDT sensitivity, Ov16 and Wb123 seroprevalence among children in Bakoye and Falémé is consistent with EOT (onchocerciasis) and EPHP (LF) since stopping treatment in 2016. The few Ov16-seropositive children should be skin-snip polymerase chain reaction tested and followed up.

Human Migration and the Spread of the Nematode Parasite Wuchereria bancrofti

The human disease lymphatic filariasis causes the debilitating effects of elephantiasis and hydrocele. Lymphatic filariasis currently affects the lives of 90 million people in 52 countries. There are three nematodes that cause lymphatic filariasis, Brugia malayi, Brugia timori, and Wuchereria bancrofti, but 90% of all cases of lymphatic filariasis are caused solely by W. bancrofti (Wb). Here we use population genomics to reconstruct the probable route and timing of migration of Wb strains that currently infect Africa, Haiti, and Papua New Guinea (PNG). We used selective whole genome amplification to sequence 42 whole genomes of single Wb worms from populations in Haiti, Mali, Kenya, and PNG. Our results are consistent with a hypothesis of an Island Southeast Asia or East Asian origin of Wb. Our demographic models support divergence times that correlate with the migration of human populations. We hypothesize that PNG was infected at two separate times, first by the Melanesians and later by the migrating Austronesians. The migrating Austronesians also likely introduced Wb to Madagascar where later migrations spread it to continental Africa. From Africa, Wb spread to the New World during the transatlantic slave trade. Genome scans identified 17 genes that were highly differentiated among Wb populations. Among these are genes associated with human immune suppression, insecticide sensitivity, and proposed drug targets. Identifying the distribution of genetic diversity in Wb populations and selection forces acting on the genome will build a foundation to test future hypotheses and help predict response to current eradication efforts.

Validation of two parent-reported autism spectrum disorders screening tools M-CHAT-R and SCQ in Bamako, Mali

BACKGROUND

Early screening is crucial for early autism spectrum disorders (ASD) diagnosis and intervention. ASD screening tools have mostly been constructed based on the Western cultural context. We hypothesized that their use in Mali may require a prior validation.

OBJECTIVE

To validate the modified checklist for autism in toddlers-Revised (M-CHAT-R) and the social communication questionnaire (SCQ) in the Malian sociocultural context for ASD screening.

STUDY DESIGN

We administered M-CHAT-R and SCQ in 947 toddlers aged 16-30 months old at the district and community health centers in Bamako and 120 patients (60 autistic and 60 age and sex matched controls) aged ≥4 years old at the psychiatry department in Bamako. Toddlers at moderate to high risk of ASD underwent M-CHAT-R/F and clinical evaluation by an ASD multidisciplinary team. M-CHAT-R and SCQ were evaluated for cultural appropriateness by Malian anthropologists. The sensitivity, specificity, PPV, NPV were determined for both M-CHAT-R and SCQ. Health professionals have been trained during ASD seminary on how to use M-CHAT-R and SCQ for ASD screening in Bamako.

RESULTS

We found for the M-CHAT-R a sensitivity of 50%, a specificity of 100%, a PPV of 100% and a NPV of 87%. The SCQ had a sensitivity of 71%, a specificity of 72%, a PPV of 73% and a NPV of 70%. We have found four out of 20 items on the M-CHAT-R that were culturally inappropriate in the Malian context.

DISCUSSION

M-CHAT-R and SCQ can be used for early autism screening in Mali. In the future, we plan to train a descent number of Malian physicians in chief and pediatricians at the district hospitals across the country to integrate the early ASD screening into the national health system.

CONCLUSION

M-CHAT-R has a perfect specificity and SCQ a fair diagnostic accuracy for ASD in Mali.

Performance of microscopic observation drug susceptibility for the rapid diagnosis of tuberculosis and detection of drug resistance in Bamako, Mali

OBJECTIVES

In Mali early detection and treatment of multidrug-resistant tuberculosis (MDR-TB) are still challenging due to the cost, time and/or complexity associated with regular tests. Microscopic Observation Drug Susceptibility (MODS) is a low-cost assay validated by WHO in 2010. It is a liquid-culture-based assay to detect the 'cording' characteristic of Mycobacterium tuberculosis complex and to assess susceptibility to both isoniazid and rifampicin defining multidrug-resistant tuberculosis (MDR-TB). In this study we aimed to evaluate the performance of MODS as diagnostic tool compared with a validated method-Mycobacteria Growth Indicator Tube/Antimicrobial Susceptibility Testing/Streptomycin, Isoniazid, Rifampicin and Ethambutol (MGIT/AST/SIRE).

METHODS AND RESULTS

Between January 2010 and October 2015 we included 98 patients with suspected TB in an observational cohort study. The sensitivity and specificity of MODS assay for detecting TB were respectively 94.12% and 85.71% compared with the reference MGIT/7H11 culture, with a Cohen κ coefficient of 0.78 (95% CI 0.517-1.043). The median time to culture positivity for MODS assay and MGIT (plus interquartile range, IQR) was respectively 8 days (IQR 5-11) and 6 days (IQR 5-6). In detecting patients with MDR-TB, the sensitivity and specificity of MODS assay were respectively 100% and 95.92%. The positive predictive value and negative predictive value were, respectively, 66.7% and 100%. The median turnaround times for obtaining MDR-TB results using MODS assay and MGIT/AST/SIRE was respectively 9 days and 35 days. Hence, the MODS assay rapidly identifies MDR-TB in Mali compared with the MGIT/AST/SIRE.

CONCLUSION

As an easy, simple, fast and affordable method, the MODS assay could significantly improve the management of TB.

Dynamics of antigenemia and transmission intensity of Wuchereria bancrofti following cessation of mass drug administration in a formerly highly endemic region of Mali

Background

After seven annual rounds of mass drug administration (MDA) in six Malian villages highly endemic for Wuchereria bancrofti (overall prevalence rate of 42.7%), treatment was discontinued in 2008. Surveillance was performed over the ensuing 5 years to detect recrudescence.

Methods

Circulating filarial antigen (CFA) was measured using immunochromatographic card tests (ICT) and Og4C3 ELISA in 6–7 year-olds. Antibody to the W. bancrofti infective larval stage (L3) antigen, Wb123, was tested in the same population in 2012. Microfilaraemia was assessed in ICT-positive subjects. Anopheles gambiae complex specimens were collected monthly using human landing catch (HLC) and pyrethrum spray catch (PSC). Anopheles gambiae complex infection with W. bancrofti was determined by dissection and reverse transcriptase polymerase chain reaction (RT-PCR) of mosquito pools.

Results

Annual CFA prevalence rates using ICT in children increased over time from 0% (0/289) in 2009 to 2.7% (8/301) in 2011, 3.9% (11/285) in 2012 and 4.5% (14/309) in 2013 (trend χ²  = 11.85, df =3, P = 0.0006). Wb123 antibody positivity rates in 2013 were similar to the CFA prevalence by ELISA (5/285). Although two W. bancrofti-infected Anopheles were observed by dissection among 12,951 mosquitoes collected by HLC, none had L3 larvae when tested by L3-specific RT-PCR. No positive pools were detected among the mosquitoes collected by pyrethrum spray catch. Whereas ICT in 6–7 year-olds was the major surveillance tool, ICT positivity was also assessed in older children and adults (8–65 years old). CFA prevalence decreased in this group from 4.9% (39/800) to 3.5% (28/795) and 2.8% (50/1,812) in 2009, 2011 and 2012, respectively (trend χ²  = 7.361, df =2, P = 0.0067). Some ICT-positive individuals were microfilaraemic in 2009 [2.6% (1/39)] and 2011 [8.3% (3/36)], but none were positive in 2012 or 2013.

Conclusion

Although ICT rates in children increased over the 5-year surveillance period, the decrease in ICT prevalence in the older group suggests a reduction in transmission intensity. This was consistent with the failure to detect infective mosquitoes or microfilaraemia. The threshold of ICT positivity in children may need to be re-assessed and other adjunct surveillance tools considered.

Prevalence of Cutaneous Leishmaniasis in Districts of High and Low Endemicity in Mali

Historically the western sahelian dry regions of Mali are known to be highly endemic for cutaneous leishmaniasis (CL) caused by Leishmania major, while cases are rarely reported from the Southern savanna forest of the country. Here, we report baseline prevalence of CL infection in 3 ecologically distinct districts of Mali (dry sahelian, north savanna and southern savanna forest areas). We screened 195 to 250 subjects from 50 to 60 randomly selected households in each of the 6 villages (four from the western sahelian district of Diema in Kayes region, one from the central district of Kolokani and one from the southern savanna district of Kolodieba, region of Sikasso). The screening consisted of: 1] A Leishmanin Skin Test (LST) for detection of exposure to Leishmania parasites; 2] clinical examination of suspected lesions, followed by validation with PCR and 3] finger prick blood sample to determine antibody levels to sand fly saliva. LST positivity was higher in the western district of Diema (49.9%) than in Kolokani (24.9%) and was much lower in Kolondieba (2.6%). LST positivity increased with age rising from 13.8% to 88% in Diema for age groups 2-5 years and 41-65 years, respectively. All eight PCR-confirmed L. major CL cases were diagnosed in subjects below 18 years of age and all were residents of the district of Diema. Exposure to sand fly bites, measured by anti-saliva antibody titers, was comparable in individuals living in all three districts. However, antibody titers were significantly higher in LST positive individuals (P<0.0001). In conclusion, CL transmission remains active in the western region of Mali where lesions were mainly prevalent among children under 18 years old. LST positivity correlated to higher levels of antibodies to sand fly salivary proteins, suggesting their potential as a risk marker for CL acquisition in Mali.

The Impact of Six Annual Rounds of Mass Drug Administration on Wuchereria bancrofti Infections in Humans and in Mosquitoes in Mali

Wuchereria bancrofti prevalence and transmission were assessed in six endemic villages in Sikasso, Mali prior to and yearly during mass drug administration (MDA) with albendazole and ivermectin from 2002 to 2007. Microfilaremia was determined by calibrated thick smear of night blood in adult volunteers and circulating filarial antigen was measured using immunochromatographic card test in children < 5 years of age. Mosquitoes were collected by human landing catch from July to December. None of the 686 subjects tested were microfilaremic 12 months after the sixth MDA round. More importantly, circulating antigen was not detected in any of the 120 children tested, as compared with 53% (103/194) before the institution of MDA. The number of infective bites/human/year decreased from 4.8 in 2002 to 0.04 in 2007, and only one mosquito containing a single infective larva was observed 12 months after the final MDA round. Whether this dramatic reduction in transmission will be sustained following cessation of MDA remains to be seen.

Highly heterogeneous, activated, and short-lived regulatory T cells during chronic filarial infection

The mechanisms underlying the increase in the numbers of regulatory T (Treg) cells in chronic infection settings remain unclear. Here we have delineated the phenotype and transcriptional profiles of Treg cells from 18 filarial-infected (Fil(+) ) and 19 filarial-uninfected (Fil(-) ) subjects. We found that the frequencies of Foxp3(+) Treg cells expressing CTLA-4, GITR, LAG-3, and IL-10 were significantly higher in Fil(+) subjects compared with that in Fil(-) subjects. Foxp3-expressing Treg-cell populations in Fil(+) subjects were also more heterogeneous and had higher expression of IL-10, CCL-4, IL-29, CTLA-4, and TGF-β than Fil(-) subjects, each of these cytokines having been implicated in immune suppression. Moreover, Foxp3-expressing Treg cells from Fil(+) subjects had markedly upregulated expression of activation-induced apoptotic genes with concomitant downregulation of those involved in cell survival. To determine whether the expression of apoptotic genes was due to Treg-cell activation, we found that the expression of CTLA-4, CDk8, RAD50, TNFRSF1A, FOXO3, and RHOA were significantly upregulated in stimulated cells compared with unstimulated cells. Taken together, our results suggest that in patent filarial infection, the expanded Treg-cell populations are heterogeneous, short-lived, activated, and express higher levels of molecules known to modulate immune responsiveness, suggesting that filarial infection is associated with high Treg-cell turnover.

[Role Of Emigration In The Spread Of HIV Infection In The Region Of Kayes, Mali]

AIM

To determine the impact of emigration on HIV transmission in the Kayes region.

PATIENTS AND METHODS

It was a cross-sectional study conducted in 2007 in the Fousseyni DAOU Hospital of Kayes. A total of 109 subjects were included - all participants were over 14 years old and were diagnosed as HIV positive. The variables studied were knowledge, attitudes and behaviors regarding HIV/AIDS, the notion of traveling outside of Mali and emigration. Pearson Chi² and Fisher test were used for a bivariate analysis.

RESULTS

The female/male sex ratio was of 2.51. In this data pool, 32.3% (10/31) of men were emigrants. More than a third 37.2% (29/78) of women had an emigrant as a sexual partner. There was no significant difference in the levels of knowledge regarding HIV between emigrants and those who never went abroad. The likelihood of having had relations with a sex worker in the preceding 12 months was nine times higher for an emigrant than to a non-emigrant [OR=9.13, CI 95% (2.20 - 37.84)].

An emigrant was five times more likely to have at least two sexual partners [OR=5.11, CI 95% (1.37-18.94)].

CONCLUSION

This study showed that emigration is an important factor regarding the spread of HIV in the region of Kayes Mali. Sensitization of the candidates to emigration must be reinforced.

Filariasis attenuates anemia and proinflammatory responses associated with clinical malaria: a matched prospective study in children and young adults

Background

Wuchereria bancrofti (Wb) and Mansonella perstans (Mp) are blood-borne filarial parasites that are endemic in many countries of Africa, including Mali. The geographic distribution of Wb and Mp overlaps considerably with that of malaria, and coinfection is common. Although chronic filarial infection has been shown to alter immune responses to malaria parasites, its effect on clinical and immunologic responses in acute malaria is unknown.

Methodology/Principal Findings

To address this question, 31 filaria-positive (FIL+) and 31 filaria-negative (FIL−) children and young adults, matched for age, gender and hemoglobin type, were followed prospectively through a malaria transmission season. Filarial infection was defined by the presence of Wb or Mp microfilariae on calibrated thick smears performed between 10 pm and 2 am and/or by the presence of circulating filarial antigen in serum. Clinical malaria was defined as axillary temperature ≥37.5°C or another symptom or sign compatible with malaria infection plus the presence of asexual malaria parasites on a thick blood smear. Although the incidence of clinical malaria, time to first episode, clinical signs and symptoms, and malaria parasitemia were comparable between the two groups, geometric mean hemoglobin levels were significantly decreased in FIL− subjects at the height of the transmission season compared to FIL+ subjects (11.4 g/dL vs. 12.5 g/dL, p<0.01). Plasma levels of IL-1ra, IP-10 and IL-8 were significantly decreased in FIL+ subjects at the time of presentation with clinical malaria (99, 2145 and 49 pg/ml, respectively as compared to 474, 5522 and 247 pg/ml in FIL− subjects).

Conclusions/Significance

These data suggest that pre-existent filarial infection attenuates immune responses associated with severe malaria and protects against anemia, but has little effect on susceptibility to or severity of acute malaria infection. The apparent protective effect of filarial infection against anemia is intriguing and warrants further study in a larger cohort.

In many regions of the world, including sub-Saharan Africa, concomitant infection with multiple parasites is common. In order to examine the effects of filariasis, a chronic helminth infection, on immune responses and clinical manifestations of acute malaria infection, the authors followed 31 filaria-infected (FIL+) and 31 filaria-uninfected (FIL–) individuals living in a malaria-endemic area of Mali through an entire malaria transmission season for the development of clinical malaria (fever or other symptoms of malaria in the setting of detectable blood parasites). Serum levels of inflammatory cytokines previously associated with severe malaria were decreased in FIL+ subjects at the time of acute clinical malaria. Although there were no differences between FIL+ and FIL– subjects with respect to the time of first episode of malaria or the number or severity of malaria episodes, filarial infection appeared to protect against the development of anemia during the malaria transmission season. These findings demonstrate that chronic filarial infection modulates the immune response to acute malaria. The apparent effect on anemia is intriguing and deserves further study.

Interferon regulatory factor modulation underlies the bystander suppression of malaria antigen-driven IL-12 and IFN-γ in filaria-malaria co-infection

In areas where polyparasitism is highly prevalent, the impact of multiple parasites on the host response is underestimated. In particular, the presence of helminth infection coincident with malaria profoundly alters the production of malaria-specific IFN-γ, IL-12p70, CXCL9, CXCL10 and CXCL11, cytokines/chemokines known to be critical in mediating malaria-specific immunity. In order to elucidate the mechanisms underlying the suppression of malaria-specific cytokines/chemokines, we assessed the expression of malaria-specific IL-12Rβ1, IL-12Rβ2 and interferon regulatory factor (IRF)-1 in blood obtained from 18 filaria-infected (Fil(+)) and 17 filaria-uninfected (Fil(-)) individuals in a filaria-malaria co-endemic region of Mali. We found that Fil(+) individuals had significantly lower RNA expression of IRF-1 but not IL-12Rβ1 or IL-12Rβ2 in response to malaria antigen stimulation. We also measured the frequency of IL-12-producing DCs from these subjects and found that Fil(+) subjects had lower frequencies of IL-12(+) mDCs after malaria antigen stimulation than did the Fil(-) subjects. Modeling these data in vitro, we found that mDCs pre-exposed to live microfilariae not only produced significantly lower levels of CXCL-9, CXCL-10, IL-12p35, IL-12p40, IL-12p19 and CXCL-11 following stimulation with malaria antigen but also markedly downregulated the expression of IRF-1, IRF-2 and IRF-3 compared with microfilaria-unexposed mDCs. siRNA-inhibition of irf-1 in mDCs downregulated the production of IL-12p70 through repression of IL-12p35. Our data demonstrate that the modulation of IRFs seen in filarial (and presumably other tissue-invasive helminths) infection underlies the suppression of malaria-specific cytokines/chemokines that play a crucial role in immunity to malaria.

Filarial infection suppresses malaria-specific multifunctional Th1 and Th17 responses in malaria and filarial coinfections

The mechanisms underlying the modulation of both the malaria-specific immune response and the course of clinical malaria in the context of concomitant helminth infection are poorly understood. We used multiparameter flow cytometry to characterize the quality and the magnitude of malaria-specific T cell responses in filaria-infected and -uninfected individuals with concomitant asymptomatic Plasmodium falciparum malaria in Mali. In comparison with filarial-uninfected subjects, filarial infection was associated with higher ex vivo frequencies of CD4(+) cells producing IL-4, IL-10, and IL-17A (p = 0.01, p = 0.001, and p = 0.03, respectively). In response to malaria Ag stimulation, however, filarial infection was associated with lower frequencies of CD4(+) T cells producing IFN-γ, TNF-α, and IL-17A (p < 0.001, p = 0.04, and p = 0.04, respectively) and with higher frequencies of CD4(+)IL10(+)T cells (p = 0.0005). Importantly, filarial infection was associated with markedly lower frequencies of malaria Ag-specific Th1 (p < 0.0001), Th17 (p = 0.012), and "TNF-α" (p = 0.0008) cells, and a complete absence of malaria-specific multifunctional Th1 cells. Filarial infection was also associated with a marked increase in the frequency of malaria-specific adaptive regulatory T/Tr1 cells (p = 0.024), and the addition of neutralizing anti-IL-10 Ab augmented the amount of Th1-associated cytokine produced per cell. Thus, among malaria-infected individuals, concomitant filarial infection diminishes dramatically the frequencies of malaria-specific Th1 and Th17 T cells, and alters the quality and magnitude of malaria-specific T cell responses.

Use of high-dose, twice-yearly albendazole and ivermectin to suppress Wuchereria bancrofti microfilarial levels

BACKGROUND

Annual mass treatment with albendazole and ivermectin is the mainstay of current strategies to interrupt transmission of Wuchereria bancrofti in Africa. More-effective microfilarial suppression could potentially reduce the time necessary to interrupt transmission, easing the economic burden of mass treatment programs in countries with limited resources.

METHODS

To determine the effect of increased dose and frequency of albendazole-ivermectin treatment on microfilarial clearance, 51 W. bancrofti microfilaremic residents of an area of W. bancrofti endemicity in Mali were randomized to receive 2 doses of annual, standard-dose albendazole-ivermectin therapy (400 mg and 150 μg/kg; n = 26) or 4 doses of twice-yearly, increased-dose albendazole-ivermectin therapy (800 mg and 400 μg/kg; n = 25).

RESULTS

Although microfilarial levels decreased significantly after therapy in both groups, levels were significantly lower in the high-dose, twice-yearly group at 12, 18, and 24 months. Furthermore, there was complete clearance of detectable microfilariae at 12 months in the 19 patients in the twice-yearly therapy group with data available at 12 months, compared with 9 of 21 patients in the annual therapy group (P < .001, by Fisher's exact test). This difference between the 2 groups was sustained at 18 and 24 months, with no detectable microfilariae in the patients receiving twice-yearly treatment. Worm nests detectable by ultrasonography and W. bancrofti circulating antigen levels, as measured by enzyme-linked immunosorbent assay, were decreased to the same degree in both groups at 24 months, compared with baseline.

CONCLUSIONS

These findings suggest that increasing the dosage and frequency of albendazole-ivermectin treatment enhances suppression of microfilariae but that this effect may not be attributable to improved adulticidal activity.

At homeostasis filarial infections have expanded adaptive T regulatory but not classical Th2 cells

Despite the well-documented immune suppression associated with human helminth infections, studies characterizing the immune response at the single-cell level are scanty. We used multiparameter flow cytometry to characterize the type of effector (Th1, Th2, and Th17) and regulatory (natural T regulatory cells [nTregs] and adaptive Treg cells [aTreg/type 1 regulatory cells (Tr1s)]) CD4(+) and CD8(+) T cells in filaria-infected (Fil(+)) and -uninfected (Fil(-)) individuals at homeostasis (in the absence of stimulation). Frequencies of CD4(+) lymphocytes spontaneously producing IL-4, IL-10, and IL-17A were significantly higher in Fil(+), as were those of IL-10(+)/IL-4(+) double-producing CD4(+) cells. Interestingly, frequencies of Th17 and aTreg/Tr1s but not classical Th1 or Th2 cells were significantly increased in Fil(+) compared to Fil(-) individuals. Although the frequency of nTreg was increased in Fil(+), IL-10 was overwhelmingly produced by CD4(+)CD25(-) cells. Moreover, the concentration of IL-10 produced spontaneously in vitro strongly correlated with the integrated geometric mean fluorescence intensity of IL-10-producing aTreg/Tr1s in Fil(+). Together, these data show that at steady state, IL-10-producing aTreg/Tr1 as well as nTreg and effector Th17 CD4(+) cells are expanded in vivo in human filarial infections. Moreover, we have established baseline ex vivo frequencies of effector and Tregs at homeostasis at a population level.

A randomized trial of doxycycline for Mansonella perstans infection

BACKGROUND

Mansonella perstans infection is common in areas of Africa where Wuchereria bancrofti, a causative agent of lymphatic filariasis, is endemic. M. perstans is refractory to standard antifilarial therapies. The recent discovery of bacterial endosymbionts (e.g., wolbachia) in most filarial species, including M. perstans, provides new therapeutic options for reducing microfilaremia.

METHODS

In an open-label, randomized trial, we recruited subjects with M. perstans microfilaremia, with or without concomitant W. bancrofti infection, from four villages in Mali and randomly assigned them to receive doxycycline, at a dose of 200 mg daily for 6 weeks (106 subjects), or no treatment (110). At 6 months, subjects who were coinfected with W. bancrofti underwent a second random assignment, to treatment with a single dose of albendazole (400 mg) and ivermectin (150 microg per kilogram of body weight) or no treatment. Subjects were monitored daily during the first 6-week study period for adverse events. M. perstans and W. bancrofti microfilarial levels were assessed at 6, 12, and 36 months.

RESULTS

At 12 months, 67 of 69 subjects who had received treatment with doxycycline only (97%) had no detectable M. perstans microfilariae per 60 microl of blood, as compared with 10 of 63 subjects who had received no treatment (16%) (relative risk, 6.18; 95% confidence interval, 3.63 to 11.89; P<0.001). At 36 months, M. perstans microfilaremia remained suppressed in 48 of 64 subjects who had received treatment with doxycycline only (75%), a finding that was consistent with a macrofilaricidal effect of doxycycline. Vomiting was more frequent in the doxycycline-treated group than in the untreated group (17% vs. 4%).

CONCLUSIONS

These results are consistent with previous findings that M. perstans harbors the intracellular endosymbiont, wolbachia, and suggest that doxycycline is an effective therapy for M. perstans infection. (ClinicalTrials.gov number, NCT00340691.)

Patent filarial infection modulates malaria-specific type 1 cytokine responses in an IL-10-dependent manner in a filaria/malaria-coinfected population

The effect of filarial infections on malaria-specific immune responses was investigated in Malian villages coendemic for filariasis (Fil) and malaria. Cytokines were measured from plasma and Ag-stimulated whole blood from individuals with Wuchereria bancrofti and/or Mansonella perstans infections (Fil(+); n = 19) and those without evidence of filarial infection (Fil(-); n = 19). Plasma levels of IL-10 (geometric mean [GM], 22.8 vs 10.4) were higher in Fil(+) compared with Fil(-), whereas levels of IFN-inducible protein (IP)-10 were lower in Fil(+) (GM, 66.3 vs 110.0). Fil(+) had higher levels of spontaneously secreted IL-10 (GM, 59.3 vs 6.8 pg/ml) and lower levels of IL-2 (1.0 vs 1.2 pg/ml) than did Fil(-). Although there were no differences in levels of Staphylococcus aureus enterotoxin B-induced cytokines between the two groups, Fil(+) mounted lower IL-12p70 (GM, 1.11 vs 3.83 pg/ml; p = 0.007), IFN-gamma (GM, 5.44 vs 23.41 pg/ml; p = 0.009), and IP-10 (GM, 29.43 vs 281.7 pg/ml; p = 0.007) responses following malaria Ag (MalAg) stimulation compared with Fil(-). In contrast, Fil(+) individuals had a higher MalAg-specific IL-10 response (GM, 7318 pg/ml vs 3029 pg/ml; p = 0.006) compared with those without filarial infection. Neutralizing Ab to IL-10 (but not to TGFbeta) reversed the down-regulated MalAg-specific IFN-gamma and IP-10 (p < 0.001) responses in Fil(+). Together, these data demonstrate that filarial infections modulate the Plasmodium falciparum-specific IL-12p70/IFN-gamma secretion pathways known to play a key role in resistance to malaria and that they do so in an IL-10-dependent manner.

Filaria-induced monocyte dysfunction and its reversal following treatment

Monocyte dysfunction in filarial infection has been proposed as one mechanism underlying the diminished antigen-specific T-cell response seen in patent lymphatic filariasis. Cytokine/chemokine production and gene expression in monocytes from filaria-infected patients and uninfected healthy donors were assessed unstimulated and in response to stimulation with Staphylococcus aureus Cowan I bacteria plus gamma interferon both before and 8 months following treatment. Monocytes from filaria-infected individuals were studded with intracellular microfilarial antigens. Furthermore, monocytes from these individuals were less capable of producing interleukin-8 (IL-8), Exodus II, MIP-1alpha, MIP-1beta, and IL-1alpha and preferentially expressed genes involved in apoptosis and adhesion compared with monocytes from uninfected donors. Eight months following treatment with a single dose of ivermectin-albendazole, some of these defects were reversed, with monocyte production of IL-8, IL-1alpha, MIP-1alpha, and IL-10 being comparable to that seen in the uninfected controls. In addition, a marked increase in mRNA expression of genes associated with protein metabolism, particularly heat shock proteins, was seen compared with pretreatment expression. These data suggest that the function and gene expression of monocytes in filaria-infected patients are altered but that this dysfunction is partially reversible following antifilarial treatment.

[Presence and risk of transmission of Wuchereria bancrofti is a reality in rural Mali: the case of the town of Bariambani in the Cirle of Kati]

Previous studies on lymphatic filariasis in Mali showed high infection rate in rural area. This study was aimed to find Wuchereria bancrofti microfilaria in human peripheral blood and larvae in vectors. For that purpose we carried out an entomological, clinical and parasitological study in Banambani a village located at 25 km from Bamako the capital city. The parasitological and clinical study was a single cross sectional study including night blood thick smear and physical examination. The entomological study was longitudinal with three annual surveys at the beginning, the middle and the end of the rainy season with parasite detection on vector by PCR. The infection rates by night thick smear was 1.5% of the study sample. The transmission was assured by Anopheles gambiae s.l and Anopheles funestus. Wuchereria bancrofti larvae have been detected on 0.5% of the vectors. The higher entomological inoculation rate (EIR) for An. gambiae s.l has been observed in August (4.03 infective bites per man per night) and in October for An. funestus (1.9 infective bites per man per night). Lymphatic filariasis is present in Malian rural area and transmission still occurring.

Clinical characteristics of post-treatment reactions to ivermectin/albendazole for Wuchereria bancrofti in a region co-endemic for Mansonella perstans

Post-treatment reactions to single-dose ivermectin (200 microg/kg) and albendazole (400 mg) were studied in a filarial endemic region of Mali. The prevalence of Wuchereria bancrofti in this region was 48.3% (69 of 143), and coinfection with Mansonella perstans was common (30 of 40, 75%). Microfilarial levels of M. perstans correlated positively with age (P = 0.006) and with W. bancrofti microfilarial levels (P = 0.006). Forty individuals (28 infected and 12 uninfected) were treated, with mild post-treatment reactions occurring in 35.7% (7 of 28) of the W. bancrofti-infected subjects. Reaction severity correlated with pretreatment W. bancrofti microfilarial levels (P = 0.001). There were no significant differences in the prevalence or severity of post-treatment reactions in those who were co-infected with M. perstans. It is concluded that co-infection with M. perstans does not significantly alter the post-treatment reaction profile to single-dose ivermectin/albendazole in W. bancrofti infection in this community, and that acute post-treatment reactions should not limit patient compliance in community-based programs to eliminate lymphatic filariasis.