Evidence against Wolbachia symbiosis in Loa loa

BACKGROUND: The majority of filarial nematode species are host to Wolbachia bacterial endosymbionts, although a few including Acanthocheilonema viteae, Onchocerca flexuosa and Setaria equina have been shown to be free of infection. Comparisons of species with and without symbionts can provide important information on the role of Wolbachia symbiosis in the biology of the nematode hosts and the contribution of the bacteria to the development of disease. Previous studies by electron microscopy and PCR have failed to detect intracellular bacterial infection in Loa loa. Here we use molecular and immunohistological techniques to confirm this finding. METHODS: We have used a combination of PCR amplification of bacterial genes (16S ribosomal DNA [rDNA], ftsZ and Wolbachia surface protein [WSP]) on samples of L. loa adults, third-stage larvae (L3) and microfilariae (mf) and immunohistology on L. loa adults and mf derived from human volunteers to determine the presence or absence of Wolbachia endosymbionts. Samples used in the PCR analysis included 5 adult female worms, 4 adult male worms, 5 mf samples and 2 samples of L3. The quality and purity of nematode DNA was tested by PCR amplification of nematode 5S rDNA and with diagnostic primers from the target species and used to confirm the absence of contamination from Onchocerca sp., Mansonella perstans, M. streptocerca and Wuchereria bancrofti. Immunohistology was carried out by light and electron microscopy on L. loa adults and mf and sections were probed with rabbit antibodies raised to recombinant Brugia malayi Wolbachia WSP. Samples from nematodes known to be infected with Wolbachia (O. volvulus, O. ochengi, Litomosoides sigmodontis and B. malayi) were used as positive controls and A. viteae as a negative control. RESULTS: Single PCR analysis using primer sets for the bacterial genes 16S rDNA, ftsZ, and WSP were negative for all DNA samples from L. loa. Positive PCR reactions were obtained from DNA samples derived from species known to be infected with Wolbachia, which confirmed the suitability of the primers and PCR conditions. The quality and purity of nematode DNA samples was verified by PCR amplification of 5S rDNA and with nematode diagnostic primers. Additional analysis by 'long PCR' failed to produce any further evidence for Wolbachia symbiosis. Immunohistology of L. loa adults and mf confirmed the results of the PCR with no evidence for Wolbachia symbiosis. CONCLUSION: DNA analysis and immunohistology provided no evidence for Wolbachia symbiosis in L. loa

Age-related prevalence of antibody response against three different, defined Plasmodium falciparum antigens in children from the Haut-Ogooué province in Gabon

The kinetics of the humoral response to defined Plasmodium falciparum antigens was studied in 543 children, 1 month to 15 years old, living in an area endemic for malaria. The antigens used for enzymelinked immunosorbent assay were (i) the synthetic peptide (NANP)40 representing the immunodominant repeated region of the circumsporozoite protein, and (ii) the fusion peptide 31.1, representing the N-terminal portion of the 83 kDa polypeptide expressed at the surface of merozoites which is a processed product of the 190-200 kDa glycoprotein. In addition, glutaraldehyde-fixed infected red blood cells (RBC) were used to detect ring-infected erythrocyte surface antigen (RESA) and unfixed infected RBC to detect intra-erythrocytic asexual form (IEF) antigens by immunofluorescence. In the 1 to 2 months age group, 50%, 26% and 21% of the children had antibodies for IEF, (NANP)40 and 31.1 respectively, but none had anti-RESA antibodies. The proportions of positive subjects decreased until 3 to 6 months and then increased progressively for the 4 antigens, approaching, but not reaching, adult values by the age of 15 years. Antibodies against specific antigens were acquired concomitantly. Children born from (NANP)40-positive mothers showed enhanced anti-(NANP)40 IgG response

Prevalence of Plasmodium falciparum infection in asymptomatic rural Gabonese populations

<p>Abstract</p> <p>Background</p> <p>Malaria may be perennial or epidemic in sub-Saharan Africa, and its transmission may be stable or unstable, depending on the region. The prevalence of asymptomatic <it>Plasmodium falciparum </it>carriage is poorly documented in Gabon. A large survey of <it>P. falciparum </it>infection was conducted in asymptomatic individuals living in rural Gabon.</p> <p>Methods</p> <p>Two hundred and twenty-two villages were randomly selected in the nine administrative regions. With the participants' informed consent, blood samples were collected for thick and thin blood film examination after 20% Giemsa staining. Prevalence rates were calculated per village, per region and per ecosystem, and nationwide. Demographic risk factors were identified with STATA software version 9.0. Significance was assumed at p < 0.05.</p> <p>Results and discussion</p> <p>The prevalence of <it>P. falciparum </it>in adults was 6.2% (269/4342) nationwide, with a maximum of 37.2% in one village; a linear decrease was observed with increasing age (p = 0.045). Only 5% of the 399 children from forest areas tested positive. The prevalence was significantly higher in forest areas (7%) than in savannah (4%) and lakeland (2.5%). Within the forest region, the prevalence was significantly higher in forest grassland (10.9%) than in the mountain forest (3.5%), interior forest (6.8%) and north-eastern forest (4.5%).</p> <p>Conclusion</p> <p><it>Plasmodium falciparum </it>carriage remains high among adults in rural Gabon. Control measures must be adapted to the region and ecosystem. Routine treatment of asymptomatic individuals should be considered.</p

Epidemiology of Concomitant Infection Due to Loa loa and Mansonella perstans in Gabon

Loa loa and Mansonella perstans are blood filarial parasites, endemic in the central and western African forest block, and transmitted by chrysops and culicoides flies, respectively. Loa loa is pathogenic and represents a major obstacle to the control of co-endemic filariae. Treatment of individuals with >8000 Loa loa microfilariae/ml can result in severe adverse reactions. M. perstans is prevalent in the tropics, with undefined clinical symptoms. We screened 4392 individuals for these infections in 212 Gabonese villages. The overall prevalence rates were 22.4% for Loa loa microfilariae, 10.2% for M. perstans, and 3.2% for mixed infection. These rates varied across the different ecosystems: forest, savannah, Lakeland, river (Ogouée), and equator. A correlation was found between the prevalence and intensity of microfilariae, while a negative relationship was found between clinical symptoms (pruritis, Calabar swelling) and the prevalence of Loa loa microfilaremia. This study confirms the spatial uniformity of the relationship between parasitological indices, and provides a map and baseline data for implementation of mass chemotherapy for these infections

Transmission Intensity Affects Both Antigen-Specific and Nonspecific T-Cell Proliferative Responses in Loa loa Infection

T-cell proliferative responses were studied in two villages in Gabon with different levels of Loa loa transmission. The first village (Okoumbi) had an annual transmission potential (ATP) of ≈9,000 infective larvae (L3)/person/year (high transmission village), while the second village (Ndjokaye) had an ATP of ≈1,000 L3/person/year (low transmission village). Proliferation and cytokine assays were performed on peripheral blood mononuclear cells (PBMC) from individuals aged 18 years and over using either mitogens (concanavalin A or phytohemagglutinin), antigens (purified protein derivative [PPD], irrelevant antigen), or soluble extracts of L3, microfilariae, or adult L. loa. PBMC from individuals in the low transmission village responded better to stimulation with adult antigen and to PPD than did PBMC from individuals in the high transmission village (P = 0.0031 and P = 0.0012, respectively). These data suggest that high levels of transmission of L. loa depress both specific and nonspecific T-cell proliferative responses in infected humans

High levels of parasite-specific IgG1 correlate with the amicrofilaremic state in Loa loa infection

To investigate the mechanisms of protective immunity operating in Loa loa infection, 56 persons from a L. loa–endemic village in southeast Gabon were examined over a 7-year period. The level of L. loa–specific IgG subclasses in defined parasitologic groups was compared by use of ELISA with either adult, microfilarial, or third-stage larval (L3) antigens ofL. loa. With all antigen preparations, IgG1 levels were significantly higher in amicrofilaremic persons than in persons with high or low levels of microfilariae. Moreover, there was a significant negative correlation between IgG1 levels to L3 antigen and the density of microfilariae (Spearman's rs = –.701; P &lt; .01). There was no correlation between density of microfilariae and levels of other IgG subclasses or of IgE. These data indicate that IgG1 may playa role in the effector mechanism(s) involved in resistance against L. loa and suggest that L3 antigens may be important in eliciting protective responses

Etude des réponses immunitaires contre l'antigène recombinant "15 kDa" de la filaire Loa loa

TOURS-BU Médecine (372612103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Coinfection of Human Filarial Loa loa, Mansonnella perstans in Human T Lymphotropic Virus Type 1 Infected Individuals in Gabon

International audienceA survey was conducted throughout Gabon to search simultaneously for Human T-Lymphotropic Virus type 1 (HTLV-1) using quantitative polymerase chain reaction (qPCR) and the serological method as well as filarial infection on the same sample by direct examination of 10 μL of blood and the concentration technique. 3728 samples were analyzed, showing that 8.3% (320/3728) were positive for HTLV-1, 22.3 % (831/3728) exhibited Loa loa and 9.8% (366/3728) were positive for Mansonella perstans. A total of 95 (2.5%) individuals had HTLV-1–L. Loa coinfection and 33 (0.9%) HTLV1–M. perstans coinfection. Interestingly, there were more carriers of L. loa microfilaria positive for HTLV-1 than L. loa-negative individuals (10.1% vs. 6.7%, respectively; p=0.0004). Regarding Mansonella perstans distribution (another filarial species prevalent in Gabon), there was no significant difference between HTLV-1 / M. perstans carriers and non-carriers (7.4% vs. 7.9%, respectively; p=0.77). Furthermore, a density of Loa loa microfilariae over 30,000 microfilariae per milliliter influences HTLV-1 carriage (p=0.02). The prevalence of L. loa, M. perstans microfilaremia and HTLV-1 monoinfections and coinfections was higher in forest ecosystems than in savannah and lakeland (p<0.001). Correlations were also found with age and sex. These results suggest that L. loa and not M. perstans microfilariae carriage may affect the carriage of HTLV-1. A relationship between sex, age, and the forest ecosystem is suggested