Protection against L3 induced Brugia malayi infection in Mastomys coucha pre-immunized with BmAFII fraction of the filarial adult worm

Immune Response Profiling of Cocktails of Brugia malayi Vaccine Candidates DIM-1, Calponin and Troponin 1 in BALB/c Mice

PURPOSE

In search of a vaccine for the control of human lymphatic filariasis (LF) caused by Wuchereria bancrofti, Brugia malayi and B. timori, we identified three parasite-specific potential candidates: the disorganized muscle protein-1 (D), calponin (C) and troponin 1 (T) in B. malayi adult worm. In the present study, we investigated the immune response profile of the cocktails of the recombinant D, T and C proteins.

METHODS

Groups of BALB/c mice were immunized with individual rproteins or their cocktails DT, TC, DC and DTC, and the immunogen-specific IgG and its subclasses and IgE were determined. Cells from the immunized animals were challenged in vitro with the respective rproteins and cocktails and the release of nitric oxide (NO) from macrophages and Th1 and Th2 cytokines from splenocytes were determined.

RESULTS

Among the immunized groups, DTC elicited comparatively a stronger response which included augmented release of NO, Th1 (IL-1β, IL-2, IFN-γ and TNF-α) and Th2 (IL-4, IL-6, IL-10 and TGF-β) cytokines, and increased levels of immunogen-specific IgG, IgG1 and IgG2b and low levels of immunogen-specific IgG2a and IgE and the Th2 cytokine IL-13.

CONCLUSION

Immune responses that play important role in host protection were elicited strongly by DTC cocktail compared to the individual rproteins or DT, TC and DC cocktails. The findings provide a sound rationale for further studies on DTC cocktail as a vaccine candidate for the control of LF.

Lymphatic filariasis and visceral leishmaniasis coinfection: A review on their epidemiology, therapeutic, and immune responses

Coinfection is less commonly observed in individuals around the world, yet it is more common than the single infection. Around 800 million people worldwide are infected with helminths as a result of various diseases. Lymphatic filariasis (LF) and visceral leishmaniasis (VL) are chronic, deadly, crippling, and debilitating neglected tropical diseases (NTDs) that are endemic in tropical and subtropical regions of the world. Due to poor hygienic conditions, poverty, and genetic predisposition, those living in endemic areas are more likely to develop both leishmaniasis and filariasis. One of the key challenges in the management of LF/VL coinfection is the development of an effective therapeutic strategy that not only treats the first episode of VL but also prevents LF. However, there is a scarcity of knowledge and data on the relationship between LF and VL coinfection. While reviewing it was apparent that only a few studies relevant to LF/VL coinfections have been reported from southeastern Spain, Sudan, and the Indian subcontinents, highlighting the need for greater research in the most affected areas. We also looked at LF and VL as a single disease and also as a coinfection. Some features of the immune response evolved in mammalian hosts against LF and VL alone or against coinfection are also discussed, including epidemiology, therapeutic regimens, and vaccines. In addition to being potentially useful in clinical research, our findings imply the need for improved diagnostic methodology and therapeutics, which could accelerate the deployment of more specific and effective diagnosis for treatments to lessen the impact of VL/LF coinfections in the population.

Lymphatic filariasis vaccine development: neglected for how long?

INTRODUCTION

Lymphatic filariasis (LF), also known as elephantiasis, has been recognized by the world health organization and the centers for disease control and prevention as one of the neglected tropical diseases. The huge prevalence and risk of manifestation to date reflect the poor management of this disease. The disease poses vast public health and socio-economic burdens and generates a dire need for the development of a prophylactic solution for mass administration.

AREAS COVERED

Vaccination has been a sought-out strategy for dealing with ever-evolving infectious diseases and can be duly tuned to become a cost effective means of disease control and eventual eradication. In this review, we highlight the epidemiology of LF with the current diagnosis and treatment modules. The need for the development of a potential vaccine candidates, and challenges are discussed. The evidence presented in this review aims to enlighten the readers regarding the essential factors governing LF and its management using prophylactic measures.

EXPERT OPINION

The complex nature of filarial parasites is evident from the absence of a single vaccine for LF. The development and selection of an appropriate preclinical model and its translation into clinical practice is deemed to be a major task needing in-depth evaluation to formulate an effective vaccine. Explorations of the existing vaccine platforms would serve to be an apt strategy in this direction.

Cross-protective efficacy of immuno-stimulatory recombinant Brugia malayi protein HSP60 against the Leishmania donovani in BALB/c mice

Coinfection of Leishmania with bacteria, viruses, protozoans, and nematodes alter the immune system of the host, thereby influencing the disease outcomes. Here, we have determined the immunogenic property and protective efficacy of the cross-reactive molecule HSP60 of filarial parasite B. malayi against the L. donovani in BALB/c mice. Parasitological parameters results showed a significant decrease in the parasite burden (~59%; P < 0.001) and also a substantial increase in the delayed-type hypersensitivity (DTH) response (P < 0.001) in mice immunized with 10 μg of rBmHSP60. Protection against L. donovani in mice immunized with rBmHSP60 resulted from activation of the T cells, which is characterized by higher levels of nitric oxide (NO) production, enhanced cell proliferation, higher levels (expression and release) of IFN- γ, TNF- α, and IL-12, also, higher production of IgG and IgG2a antibodies. This strong Th1 immune response creates an inflammatory domain for L. donovani and protects the host from VL.

Immunolocalization of Disorganized Muscle Protein-1 in Different Life Stages of Human Lymphatic Filariid, Brugia malayi

Purpose

We recently identified disorganized muscle protein-1 of Brugia malayi (DIM-1bm) as a vaccine candidate for human lymphatic filariasis. The present study was aimed at investigating the localization of DIM-1bm in the life-stages of B. malayi to identify the tissue target of vaccine action.

Methods

Recombinant DIM-1bm (rDIM-1bm) was prepared and antibodies were raised in BALB/c mice. Immunoblots of SDS-PAGE resolved B. malayi infective 3rd stage larvae (L₃) and adult worm antigens and rDIM-1bm were prepared and reacted with anti-rDIM-1bm sera. Sections of adult female worms and whole-mount preparations of L₃ and microfilariae (mf) were stained by immunofluorescence using rDIM-1bm antibodies and Alexa Fluor 488 labeled secondary antibodies, and examined under a confocal microscope.

Results

Immunofluorescence staining showed that DIM-1bm is localized mainly in the subcuticular muscle layer in the L₃ and the adult worms; no fluorescent signal could be detected in mf.

Conclusion

The localization of DIM-1bm in the parasites’ muscle layer suggests that the immunoprophylactic efficacy of DIM-1 is evidently due to immobilization of the parasite and its subsequent immune elimination.

Troponin 1 of human filarial parasite Brugia malayi: cDNA cloning, expression, purification, and its immunoprophylactic potential

In the search for immunoprophylactics for the control of human lymphatic filariasis, we recently identified troponin 1 (Tn1) in Brugia malayi adult worms. The present study reports the cloning and expression of the B. malayi Tn1 (Tn1bm), its immunoprophylactic efficacy against B. malayi infection, and the immunological responses of the host. The Tn1bm gene was cloned (Acc no. JF912447) and expressed, and the purified recombinant Tn1bm (rTn1bm) presented a single ~ 27 kDa band. Parasite load in rTn1bm-immunized BALB/c mice challenged with B. malayi infective larvae (L₃) was assessed. In rTn1bm-immunized animals, IgE, IgG, and IgG subclasses in the serum, cell proliferative response, Th1 and Th2 cytokine secretion (from splenocytes), and NO release (from peritoneal macrophages) were determined. Antibody-dependent cell-mediated cytotoxicity (ADCC) to L₃ was assayed using rTn1bm-immune serum. The innate immune response markers MHC class-I, MHC class-II, TLR2, TLR4, and TLR6 expression in peritoneal macrophages and CD3+, CD4+, CD8+, and CD19+ in the splenocyte population were determined in Tn1bm-exposed cells from naïve mice. rTn1bm-immunized L₃-challenged animals showed a 60% reduction in parasite burden. Immunization upregulated cellular proliferation, cytokine (IFN-γ, TNF-α, IL-1β, IL-4, IL-6, and IL-10) secretion, NO release, and antigen-specific IgG, IgG1, and IgG2b antibody levels. rTn1bm-immune serum killed > 65% of L₃ in the ADCC assay. Increased MHC class-II, TLR2, and TLR6 expression and the relative CD4+ and CD19+ cell populations of naïve animal cells indicated the ability of rTn1bm to mobilize innate immune responses. This is the first report of the immunoprophylactic potential of rTn1bm against B. malayi.

Recombinant Calponin of human filariid Brugia malayi: Secondary structure and immunoprophylactic potential

In the search for potential vaccine candidates for the control of human lymphatic filariasis, we recently identified calponin-like protein, that regulates actin/myosin interactions, in a proinflammatory fraction F8 (45.24-48.64kDa) of Brugia malayi adult worms. In the present study, the gene was cloned, expressed, and the recombinant Calponin of B. malayi (r-ClpBm) was prepared and characterized. r-ClpBm bears homology with OV9M of Onchocerca volvulus, a non-lymphatic filariid that causes loss of vision and cutaneous pathology. r-ClpBm was found to be a ∼45kDa protein that folds into a predominantly α-helix conformation. The protective efficacy of r-ClpBm against B. malayi infection in Mastomys coucha was investigated by assessing the course of microfilaraemia and adult worm burden in the host immunized with r-ClpBm and subsequently infected with infective third stage larvae (L3). Expression of the Calponin was detected in all life stages (microfilariae, L3, L4, L5 and adults) of the parasite and immunization with r-ClpBm partially protected M. coucha against establishment of infection as inferred by ∼42% inhibition in parasite burden. Upregulated cellular proliferation, TNF-α, IFN-γ, IL-1β, IL-4, nitric oxide (NO) release, expression of iNOS, and specific IgG, IgG1 and IgG2b in immunized animals correlated with parasitological findings. r-ClpBm immunization caused degranulation in majority of mast cells indicating possible involvement of mast cell products in reducing the parasite survival. It appears that complex mechanisms including Th1, Th2, NO and mast cells are involved in the clearance of infection. To the best of our knowledge this is the first report on cloning, expression of the gene and purification of r-ClpBm, determination of its secondary structure and its ability to partially prevent establishment of B. malayi infection. Thus, r-ClpBm may further be studied and developed in combination with other protective molecules of B. malayi as a component of potential filarial cocktail vaccine candidate.

Protection against filarial infection by 45-49 kDa molecules of Brugia malayi via IFN-γ-mediated iNOS induction

Nitric oxide (NO) mediated mechanisms have been implicated in killing of some life-stages of Brugia malayi/Wuchereria bancrofti and protect the host through type 1 responses and IFN-γ stimulated toxic mediators' release. However, the identity of NO stimulating molecules of the parasites is not known. Three predominantly NO-stimulating SDS-PAGE resolved fractions F8 (45.24-48.64 kDa), F11 (33.44-38.44 kDa) and F12 (28.44-33.44 kDa) from B. malayi were identified and their proteins were analyzed by 2-DE and MALDI-TOF/TOF. Tropomyosin, calponin and de novo peptides were identified by 2-DE and MALDI-TOF/TOF in F8 and immunization with F8 conferred most significant protection against L3-initiated infection in Mastomys coucha. Immunized animals showed upregulated F8-induced NO, IFN-γ, TNF-α, IL-1β, IL-10, TGF-β release, cellular proliferative responses and specific IgG and IgG1. Anti-IFN-γ, anti-TNF-α, and anti-IL-1β significantly reduced F8-mediated NO generation and iNOS induction at protein levels. Anti-IFN-γ treated cells showed maximum reduction (>74%) in NO generation suggesting a predominant role of IFN-γ in iNOS induction. In conclusion, the findings suggest that F8 which contains tropomyosin, calponin and de novo peptides protects the host via IFN-γ mediated iNOS induction and may hold promise as vaccine candidate(s). This is also the first report of identification of tropomyosin and calponin in B. malayi.

Anti-inflammatory BmAFI of Brugia malayi modulates IgE, histamine and histamine receptor responses in Mastomys coucha

We recently reported that BmAFI, an anti-inflammatory fraction of Brugia malayi adult worm supports parasite development in the hostile peritoneal cavity (p.c.) of Mastomys coucha through a modified Th2 type of response that includes IL-13 and IgE response and anti-inflammatory IL-10 cytokine milieu. In the present study we investigated IgE related responses such as histamine release and modulation of histamine receptors 1 and 2 (HR1 and HR2) by presensitization with BmAFI of M. coucha infected with B. malayi. Sensitization with BmAFI alone enhanced IgE, histamine and HR2, but decreased HR1. Exposure of these animals to infection produced an IgE response that was inversely related to the parasite burden, and decreased histamine conc., and HR1 and HR2 expression. However, there was an early small increase in HR1 expression for a short period after exposure to infection. As expected, BmAFI sensitization supported parasite survival and development in the hostile p.c. of the host. These findings further establish that BmAFI decreases inflammatory/Th1 response and modulates Th2 responses to favour survival and development of the parasite in the hostile p.c. of the host and that IgE and histamine play an important role in this.

Single multivalent vaccination boosted by trickle larval infection confers protection against experimental lymphatic filariasis

The multivalent vaccine BmHAT, consisting of the Brugia malayi infective larval (L3) antigens heat shock protein12.6 (HSP12.6), abundant larval transcript-2 (ALT-2) and tetraspanin large extra cellular loop (TSP-LEL), was shown to be protective in rodent models from our laboratory. We hypothesize that since these antigens were identified using protective antibodies from immune endemic normal individuals, the multivalent vaccine can be augmented by natural L3 infections providing protection to the vaccinated host. This hypothesis was tested using single dose of DNA and protein or protein alone of the BmHAT vaccination in gerbils followed by live trickle L3 infection as booster dose. Vaccine-induced protection in gerbils was determined by worm establishment, micropore chamber assay and by antibody dependant cell cytotoxicity (ADCC) assay. Results were compared with the traditional prime-boost vaccination regimen. Gerbils vaccinated with BmHAT and boosted with L3 trickle infection were protected 51% (BmHAT DNA-protein) and 48% (BmHAT protein) respectively. BmHAT vaccination plus L3 trickle booster generated significant titer of antigen-specific IgG antibodies comparable to the traditional prime boost vaccination approach. BmHAT vaccination plus L3 trickle booster also generated antigen-specific cells in the spleen of vaccinated animals and these cells secreted predominantly IFN-γ and IL-4 in response to the vaccine antigens. These studies thus show that single dose of BmHAT multivalent vaccination followed by L3 trickle booster infection can confer significant protection against lymphatic filariasis.

Immunization with a multisubunit vaccine considerably reduces establishment of infective larvae in a rodent model of Brugia malayi

Although recombinant vaccines have several advantages over conventional vaccines, protection induced by single antigen vaccines is often inadequate for a multicellular helminth parasite. Therefore, immunoprophylactic efficacy of cocktail antigen vaccines comprised of several combinations of three Brugia malayi recombinant proteins BmAF-Myo, Bm-iPGM and Bm-TPP were evaluated. Myosin+TPP and iPGM+TPP provided the best protection upon B. malayi infective larval challenge with ∼70% reduction in adult worm establishment over non-vaccinated animals that was significantly higher than the protection achieved by any single antigen vaccine. Myosin+iPGM, in contrast did not provide any enhance protection over the single recombinant protein vaccines. Specific IgG, IgM level, IgG antibody subclasses levels (IgG1, IgG2a, IgG2b, IgG3), lymphocyte proliferation, reactive oxygen species level and cytokines level were also determined to elucidate the characteristics of the protective immune responses. Thus the study undertaken provided more insight into the cocktail vaccination approach to combat LF.

A comprehensive, model-based review of vaccine and repeat infection trials for filariasis

SUMMARY Filarial worms cause highly morbid diseases such as elephantiasis and river blindness. Since the 1940s, researchers have conducted vaccine trials in 27 different animal models of filariasis. Although no vaccine trial in a permissive model of filariasis has provided sterilizing immunity, great strides have been made toward developing vaccines that could block transmission, decrease pathological sequelae, or decrease susceptibility to infection. In this review, we have organized, to the best of our ability, all published filaria vaccine trials and reviewed them in the context of the animal models used. Additionally, we provide information on the life cycle, disease phenotype, concomitant immunity, and natural immunity during primary and secondary infections for 24 different filaria models.

Heat shock protein 60 of filarial parasite Brugia malayi: cDNA cloning, expression, purification and in silico modeling and analysis of its ATP binding site

We report here cloning and expression of full length mitochondrial HSP60 gene of Brugia malayi adult worm (mtHSP60bm), purification of the gene product by affinity chromatography, its in silico 3D structure and the sequence homology of the protein with Escherichia coli GroEL/ES and human HSP60. The ATP binding pocket of human HSP60 and mtHSP60bm were analyzed and compared using in silico models. The distribution of HSP60 in different life-stages of the parasite was determined using antibodies raised against recombinant mtHSP60bm (rmtHSP60bm). mtHSP60bm was present in all life-stages of the parasite except third stage infective larvae, in which it could be induced by heat-shock, and showed high degree of homology with E. coli GroEL/ES. The ATP binding pocket of HSP60 in humans, E. coli and B. malayi were also found structurally conserved. This similarity between human and mtHSP60bm might be useful in understanding the host-parasite interactions. This is the first ever report on distribution, cloning, sequence homology and ATP binding site of mtHSP60bm.

Immunization with L. sigmodontis microfilariae reduces peripheral microfilaraemia after challenge infection by inhibition of filarial embryogenesis

BACKGROUND

Lymphatic filariasis and onchocerciasis are two chronic diseases mediated by parasitic filarial worms causing long term disability and massive socioeconomic problems. Filariae are transmitted by blood-feeding mosquitoes that take up the first stage larvae from an infected host and deliver it after maturation into infective stage to a new host. After closure of vector control programs, disease control relies mainly on mass drug administration with drugs that are primarily effective against first stage larvae and require many years of annual/biannual administration. Therefore, there is an urgent need for alternative treatment ways, i.e. other effective drugs or vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Using the Litomosoides sigmodontis murine model of filariasis we demonstrate that immunization with microfilariae together with the adjuvant alum prevents mice from developing high microfilaraemia after challenge infection. Immunization achieved 70% to 100% protection in the peripheral blood and in the pleural space and furthermore strongly reduced the microfilarial load in mice that remained microfilaraemic. Protection was associated with the impairment of intrauterine filarial embryogenesis and with local and systemic microfilarial-specific host IgG, as well as IFN-γ secretion by host cells from the site of infection. Furthermore immunization significantly reduced adult worm burden.

CONCLUSIONS/SIGNIFICANCE

Our results present a tool to understand the immunological basis of vaccine induced protection in order to develop a microfilariae-based vaccine that reduces adult worm burden and prevents microfilaraemia, a powerful weapon to stop transmission of filariasis.

Inflammatory mediator release by Brugia malayi from macrophages of susceptible host Mastomys coucha and THP-1 and RAW 264.7 cell lines

OBJECTIVE

To investigate which life stage of the parasite has the ability to stimulate release of pro- or anti-inflammatory mediators from macrophages.

METHODS

The human macrophage/monocyte cell line THP-1, the mouse macrophage cell line RAW 264.7 and naive peritoneal macrophages (PM) from the rodent host Mastomys coucha (M. coucha) were incubated at 37 °C in 5% CO(2) atmosphere with extracts of microfilariae (Mf), third stage infective larvae (L(3)) and adult worms (Ad) of Brugia malayi. After 48 hr post exposure, IL-1β, IL-6, TNF-α, IL-10 and nitric oxide (NO) in cell-free supernatants were estimated.

RESULTS

Extracts of all the life stages of the parasite were capable of stimulating pro- (IL-1β, IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines in both the cell lines and peritoneal macrophages of M. coucha. Mf was the strongest stimulator of pro-inflammatory cytokines followed by L(3) and Ad; however, Ad was a strong stimulator of IL-10 release. Mf was found to have potential to modulate LPS-induced NO release in RAW cells. Ad-induced NO release was concentration dependent with maximum at 20 μg/mL in both RAW and PMs.

CONCLUSIONS

The results show that parasites at all life stages were capable of stimulating pro- (IL-1β, IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines and NO release from macrophages of susceptible host M. coucha, human and mouse macrophage cell lines. Mf can suppress the LPS-induced NO release in RAW cells. The findings also show that the two cell lines may provide a convenient in vitro system for assaying parasite-induced inflammatory mediator release.

Sensitization with anti-inflammatory BmAFI of Brugia malayi allows L3 development in the hostile peritoneal cavity of Mastomys coucha

Filarial parasites survive by inducing tolerance in host but the antigens and mechanisms involved are not clear. Recently we found that BmAFI, a Sephadex G-200 eluted fraction of Brugia malayi adult worm extract, stimulates IL-10 release from THP-1 cells. In the present study, we determined the SDS-PAGE profile of BmAFI and infective 3rd stage larva (L3), investigated the effect of pre-sensitization of host with BmAFI on the survival and development of L3 in the non-permissive peritoneal cavity (p.c.) of the permissive host Mastomys coucha and in the p.c. of non-permissive Swiss mice, and studied immunological correlates for the observed effects. The parasite development and burden in p.c., was determined in sensitized infected M. coucha and Swiss mice and the release of TGF-β, IL-4, IL-10, IL-13, IFN-γ and NO, cellular proliferative response to Con A and BmAFI and levels of IgG subclasses and IgE were determined in sensitized infected M. coucha. Cellular proliferative response to Con A and BmAFI, mRNA expression of GATA-3, CTLA-4 and T-bet were determined in sensitized Swiss mice. In addition, the parasitological parameter was also studied in BmAFI-sensitized M. coucha exposed to the infection by standard subcutaneous (s.c.) route to assess whether sensitization enhances the intensity of infection. BmAFI-sensitization permitted survival of L3 and their development to adult stage by day 60 p.i. in the p.c. of M. coucha; in non-sensitized animals L3 could molt to L4 only and no parasite could be recovered beyond day 30 p.i. In M. coucha that received infection by s.c. route, pre-sensitization with BmAFI enhanced the microfilaraemia and adult worm recovery. In sensitized Swiss mice L3 could successfully molt to L4 in p.c. with improved recovery of parasite. BmAFI sensitization upregulated TGF-β and IL-10 release, IgG1 and IgG2b levels, GATA-3 and CTLA-4 mRNA expression, suppressed the cellular proliferative response and downregulated Con A stimulated response, IgE, IL-13, IFN-γ and NO responses. Immunoblot analysis showed that the BmAFI antiserum also strongly reacts with some L3 molecules. The results show, for the first time, that sensitization with the anti-inflammatory BmAFI which shares some of its molecules with those in L3, facilitates parasite survival in the non-permissive p.c. of the permissive host M. coucha, render a non-permissive Swiss mouse partially permissive to infection and enhances parasite load in M. coucha receiving the infection through permissive s.c. route by evoking a modified Th2 type of response and anti-inflammatory milieu. In conclusion, the findings suggest that the anti-inflammatory BmAFI fraction facilitates survival of B. malayi infection even in non-permissive environment.

The adjuvant-free immunoprotection of recombinant filarial protein Abundant Larval Transcript-2 (ALT-2) in Mastomys coucha and the immunoprophylactic importance of its putative signal sequence

The filarial protein Abundant Larval Transcript-2 (ALT-2) of the filarial parasite Brugia malayi has been shown to produce 74% worm clearance when administered with an adjuvant. In the present study, we show that it not only induces humoral and cell-mediated immunity, but also protection up to 71% in Mastomys coucha, a permissive animal model for filariasis, even without adjuvant. This unique feature of ALT-2 protein is highly restricted to its 21 amino acid N-terminal signal sequence, the absence of which resulted in poor immune response as well as immunoprotection (49%). Moreover, ALT-2 is likely to exert immunoprotection effects in B. malayi infection by maintaining a Th1-Th2 balance, evident from higher levels of IgG1 and IgG2a as well as IL-4 and IFN-γ. An improved understanding about the role of this filarial protein in host immunity, host-parasite interaction and worm clearance will aid in the development of good immunoprophylaxis for the disease.

Sufficiency of a single administration of filarial antigens adsorbed on polymeric lamellar substrate particles of poly (L-lactide) for immunization

A majority of antigens require repeated administration to ensure development of adequate humoral and cell mediated immune response. To minimize the number of administrations required, we investigated the utility of biodegradable polymeric lamellar substrate particles of poly (l-lactide) (PLSP) as adjuvant for filarial antigen preparations. PLSP was prepared and characterized and Brugia malayi adult worm extract (BmA) and its SDS-PAGE resolved 54-68 kDa fraction F6 were adsorbed on to PLSP. Swiss mice received a single injection of PLSP-F6, PLSP-BmA, FCA-F6, FCA-BmA and two doses of the plain antigens. Specific IgG, IgG1, IgG2a, IgG2b and IgE levels in serum, IFN-γ, TNF-α and nitric oxide (NO) release from cells of the immunized animals in response to antigen challenge were studied. The average size of PLSP particles was <10 μm and its % antigen adsorption efficacy was 60.4, 55.2 and 61.6 for BSA, BmA and F6, respectively. Single injection of PLSP-F6 or PLSP-BmA produced better immune responses compared to one injection of FCA-F6/BmA or two injections of plain F6 or BmA. Moreover, PLSP-F6 produced much better response than PLSP-BmA. These data demonstrate for the first time that PLSP is a superior immunoadjuvant for enhancing the immune response to filarial BmA and F6 molecules and obviates the need for multiple immunization injections.

AdultBrugia malayimitochondrial and nuclear fractions impart Th1-associated sizeable protection against infective larval challenges inMastomys coucha

Protective immunity to the subperiodic human filariid,Brugia malayi, was explored in the rodent host,Mastomys couchaafter vaccination with subcellular fractions derived from the adult stage of the parasite. The highest level of protection was conferred in animals vaccinated with the ‘mitochondria rich’ (MT) fraction, in which microfilaraemia and worm burden were markedly reduced by 67.2 and 65.9%, respectively, followed by the ‘nucleus rich’ (NR) fraction, showing reductions of 62 and 52.3%, respectively, over the non-immunized control group. Mastomys vaccinated with MT and NR, displayed a significant increase in the level of antigen-specific serum immunoglobulin G (IgG). The levels of IgG2a, IgG2b and IgM antibody isotypes were remarkably elevated in both the MT and NR immunized groups, while IgG1 and IgG3 levels were low. Apart from antibodies, both these fractions also led to marked antigen-specific lymphoproliferationin vitro, along with enhanced release of nitric oxide by peritoneal macrophages. There was an increased population of CD4+ and CD8a+T-cells in MT immunized animals, as measured by flow cytometry, accompanied by elevated levels of proinflammatory cytokines; interferon gamma (IFN-γ), tumour necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) in the culture supernatants of the activated splenocytes. The results suggest that both NR and MT contain proinflammatory molecules which evoke a protective Th1 type of immune response.

Influence of Brugia malayi life stages and BmAFII fraction on experimental Leishmania donovani infection in hamsters

The influence of live Brugia malayi parasites and a Sephadex G-200 fraction of the adult parasite extract (BmAFII) on the progression of Leishmania donovani infection was studied. Inbred hamsters were first infected with B. malayi infective 3rd stage larvae (L3), adult worms or microfilariae (mf), and then with L. donovani amastigotes (Ld), or vice versa or received both the infections simultaneously; a group of animals were first immunized with BmAFII and then infected with Ld. L. donovani parasite burden was determined between 17 and 19 days post amastigote challenge (p.a.c.) and, in case of immunized animals, between 32 and 35 days p.a.c also. Nitric oxide (NO) release from peritoneal macrophages and cellular proliferative responses of lymphnode cells were assessed in BmAFII-immunized animals given leishmania infection or no infection. Leishmanial parasite burden was significantly reduced in animals exposed to filarial L3 before amastigote inoculation and in animals given filarial adult worms after or together with amastigotes. Prior immunization of leishmania-infected animals with BmAFII also reduced the leishmanial parasite burden (17-19 days p.a.c.: >90%; 32-35 days p.a.c.: 60%). These animals showed upregulation of NO release and cellular proliferative responses to promastigote antigen or BmAFII stimulation in vitro. The findings show, for the first time, that B. malayi L3/adult worms or immunization with BmAFII inhibits progression of L. donovani infection in hamsters and this is associated with upregulation of NO and lymphocyte proliferative responses indicating that Th1 response might be responsible for this.