Polymorphism and epitope sharing between the alleles of merozoite surface protein-1 of Plasmodium falciparum among Indian isolates

Autoantibodies against the melanoma differentiation-associated protein 5 in patients with dermatomyositis target the helicase domains

OBJECTIVES

Clinical observations in patients with dermatomyositis (DM) and autoantibodies against the melanoma differentiation-associated protein 5 (MDA5) suggest that the autoantibodies contribute to the pathogenesis of MDA5(+) DM. To gain insight into the role of the anti-MDA5 autoantibodies, we aimed to identify their binding sites on the different domains of the MDA5 protein.

METHODS

We developed an in-house ELISA to assess the reactivity against the MDA5 domains (conformational epitopes) in plasma (n = 8) and serum (n = 24) samples from MDA5(+) patients with varying clinical manifestations and disease outcomes. The reactivities were also assessed using western blot (linearized epitopes). An ELISA-based depletion assay was developed to assess cross-reactivity among the different MDA5 domains.

RESULTS

All eight plasma samples consistently showed reactivity towards conformational and linearized epitopes on the helicase domains of the MDA5 protein. The ELISA-based depletion assay suggests that anti-MDA5 autoantibodies specifically target each of the three helicase domains. Twenty-two of the 24 serum samples showed reactivity in the in-house ELISA and all 22 displayed reactivity towards the helicase domains of the MDA5 protein.

CONCLUSIONS

Our data revealed that the main immunogenic targets of anti-MDA5 autoantibodies from MDA5(+) patients are the helicase domains. Considering that the helicase domains are responsible for the enzymatic activity and subsequent triggering of an inflammatory response, our findings suggest that binding of anti-MDA5 autoantibodies could alter the canonical activity of the MDA5 protein and potentially affect the downstream induction of a pro-inflammatory cascade.

Diversity and natural selection of Merozoite surface Protein-1 in three species of human malaria parasites: Contribution from South-East Asian isolates

The present study aimed to examine the genetic diversity of human malaria parasites (i.e., P. falciparum, P. vivax and P. knowlesi) in Malaysia and southern Thailand targeting the 19-kDa C-terminal region of Merozoite Surface Protein-1 (MSP-1₁₉). This region is essential for the recognition and invasion of erythrocytes and it is considered one of the leading candidates for asexual blood stage vaccines. However, the genetic data of MSP-1₁₉ among human malaria parasites in Malaysia is limited and there is also a need to update the current sequence diversity of this gene region among the Thailand isolates. In this study, genomic DNA was extracted from 384 microscopy-positive blood samples collected from patients who attended the hospitals or clinics in Malaysia and malaria clinics in Thailand from the year 2008 to 2016. The MSP-1₁₉ was amplified using PCR followed by bidirectional sequencing. DNA sequences identified in the present study were subjected to Median-joining network analysis with sequences of MSP-1₁₉ obtained from GenBank. DNA sequence analysis revealed that PfMSP-1₁₉ of Malaysian and Thailand isolates was not genetically conserved as high number of haplotypes were detected and positive selection was prevalent in PfMSP-1₁₉, hence questioning its suitability to be used as a vaccine candidate. A novel haplotype (Q/TNG/L) was also detected in Thailand P. falciparum isolate. In contrast, PvMSP-1₁₉ was highly conserved, however for the first time, a non-synonymous substitution (A1657S) was reported among Malaysian isolates. As for PkMSP-1₁₉, the presence of purifying selection and low nucleotide diversity indicated that it might be a potential vaccine target for P. knowlesi.

Cross-species reactivity of antibodies against Plasmodium vivax blood-stage antigens to Plasmodium knowlesi

Malaria is caused by multiple different species of protozoan parasites, and interventions in the pre-elimination phase can lead to drastic changes in the proportion of each species causing malaria. In endemic areas, cross-reactivity may play an important role in the protection and blocking transmission. Thus, successful control of one species could lead to an increase in other parasite species. A few studies have reported cross-reactivity producing cross-immunity, but the extent of cross-reactive, particularly between closely related species, is poorly understood. P. vivax and P. knowlesi are particularly closely related species causing malaria infections in SE Asia, and whilst P. vivax cases are in decline, zoonotic P. knowlesi infections are rising in some areas. In this study, the cross-species reactivity and growth inhibition activity of P. vivax blood-stage antigen-specific antibodies against P. knowlesi parasites were investigated. Bioinformatics analysis, immunofluorescence assay, western blotting, protein microarray, and growth inhibition assay were performed to investigate the cross-reactivity. P. vivax blood-stage antigen-specific antibodies recognized the molecules located on the surface or released from apical organelles of P. knowlesi merozoites. Recombinant P. vivax and P. knowlesi proteins were also recognized by P. knowlesi- and P. vivax-infected patient antibodies, respectively. Immunoglobulin G against P. vivax antigens from both immune animals and human malaria patients inhibited the erythrocyte invasion by P. knowlesi. This study demonstrates that there is extensive cross-reactivity between antibodies against P. vivax to P. knowlesi in the blood stage, and these antibodies can potently inhibit in vitro invasion, highlighting the potential cross-protective immunity in endemic areas.

In recent years, malaria initiatives have increasingly shifted focus from achieving malaria control to achieving malaria elimination. However, the interventions used are leading to drastic changes in the proportions of different Plasmodium species causing clinical infection, particularly within Southeast Asia. Little is known about how these different parasite species interact/compete in nature or whether exposure to one species could cause some level of protection against another. We examined cross-reactive antibody responses to key parasite proteins with roles in red blood cell invasion and identified novel cross-species reactivity among the closest of malaria affecting the human population (P. vivax and P. knowlesi). This comprehensive analysis provides evidence that cross-reactive immunity could play an important role in areas where species distributions are perturbed by malaria control measures, and future efforts to identify the specific cross-reactive epitopes involved would be invaluable both to our understanding of malaria immunity and vaccine development.

Diversity analysis of MSP1 identifies conserved epitope organization in block 2 amidst high sequence variability in Indian Plasmodium falciparum isolates

Background

Despite its immunogenicity, the polymorphic nature of merozoite surface protein 1, an important vaccine candidate for Plasmodium falciparum malaria, remains a concern. This study analyses the impact of genetic variability and parasite population structure on epitope organization of different MSP1 segments.

Methods

Altogether 98 blood samples collected from P. falciparum infected mild and severe malaria patients of Chhattisgarh and West Bengal were used to sequence regions encoding block 2 and MSP1-19 of msp1. Sequences were analysed using MEGA7, DnaSPv5, Arlequin3.5 and BepiPred.

Results

All three major MSP1 block 2 allele families namely K1, MAD20 and RO33 were detected in the samples and they together resulted in 41 indel variants. Chhattisgarh samples displayed an average MOI of 2.07 ± 1.59 which was higher in mild malaria and in age group < 18 years. Ultra-structure of block 2 alleles revealed that mutation and repeat expansion were two major mechanisms responsible for allelic variability of K1 and MAD20. Regions flanking block 2 were highly variable in Chhattisgarh with average mismatch differences (k) ranging from 1.198 to 5.156 for three families. In contrast, region encompassing MSP1-19 exhibited limited heterogeneity (k_Chhattisgarh = 1.45, k_{West Bengal} = 1.363). Of the 50 possible B cell linear epitopes predicted from block 2 variants, 94.9% (131 of 138) of the parasites could be represented by three conserved antigens.

Conclusions

Present data indicates that natural selection and transmission intensity jointly play a role in controlling allelic diversity of MSP1 in Indian parasite isolates. Despite remarkable genetic variability, a limited number of predominant and conserved epitopes are present in Indian parasite isolates reinstating the importance of MSP1 as a promising malaria vaccine candidate.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2592-y) contains supplementary material, which is available to authorized users.

Genetic diversity and antibody responses against Plasmodium falciparum vaccine candidate genes from Chhattisgarh, Central India: Implication for vaccine development

The genetic diversity in Plasmodium falciparum antigens is a major hurdle in developing an effective malaria vaccine. Protective efficacy of the vaccine is dependent on the polymorphic alleles of the vaccine candidate antigens. Therefore, we investigated the genetic diversity of the potential vaccine candidate antigens i.e. msp-1, msp-2, glurp, csp and pfs25 from field isolates of P.falciparum and determined the natural immune response against the synthetic peptide of these antigens. Genotyping was performed using Sanger method and size of alleles, multiplicity of infection, heterogeneity and recombination rate were analyzed. Asexual stage antigens were highly polymorphic with 55 and 50 unique alleles in msp-1 and msp-2 genes, respectively. The MOI for msp-1 and msp-2 were 1.67 and 1.28 respectively. A total 59 genotype was found in glurp gene with 8 types of amino acid repeats in the conserved part of RII repeat region. The number of NANP repeats from 40 to 44 was found among 55% samples in csp gene while pfs25 was found almost conserved with only two amino acid substitution site. The level of genetic diversity in the present study population was very similar to that from Asian countries. A higher IgG response was found in the B-cell epitopes of msp-1 and csp antigens and higher level of antibodies against csp B-cell epitope and glurp antigen were recorded with increasing age groups. Significantly, higher positive responses were observed in the csp antigen among the samples with ≥42 NANP repeats. The present finding showed extensive diversity in the asexual stage antigens.

Non-allele specific antibody responses to genetically distinct variant forms of Plasmodium vivax Duffy binding protein (PvDBP-II) in Iranians exposed to seasonal malaria transmission

Duffy binding protein (DBP) is a leading vaccine candidate of Plasmodium vivax. The binding domain of DBP (DBP-II) is polymorphic, that may be a major challenge for development of a broadly effective vaccine against vivax malaria. The present investigation was undertaken to explore whether the sequence diversity of DBP-II causes variation in naturally acquired anti-DBP-II antibodies. In this study, the five genetically distinct variants were expressed, and anti-DBP-II responses were measured in P. vivax-infected individuals (n=202). Finally, by performing immune-depletion ELISA experiments, antibody responses to the conserved sites of all allelic forms were evaluated using the corresponding and non-corresponding patients' sera (n=20). In this study, natural P. vivax infection produces IgG against all five examined variant forms of PvDBP-II with no statistically difference. Sequence analysis in the 20 selected samples (for antibody depletion experiment) showed eight distinct haplotypes, DBPI (n=1), DBPIII (n=3), DBPIV (n=1), DBPV (n=1), DBPVI (n=5), DBPIX (n=6), DBPX (n=1), and DBP XI (n=2). The results showed the presence of the cross-reactive antibody responses to heterologous variants of PvDBP-II in Iranian individuals who were infected with distinct allelic forms of the PvDBP-II. Therefore, it is proposed that the majority of antibodies recognized sharing B-cell epitopes and this could overcome the PvDBP-II variation as a one of the biggest challenges of PvDBP-II-based vaccine development.

Genetic diversity in merozoite surface protein-1 and 2 among Plasmodium falciparum isolates from malarious districts of tribal dominant state of Jharkhand, India

INTRODUCTION

The genetic make-up of malaria parasite is potent for understanding the parasite virulence, designing antimalarial vaccine and evaluating the impact of malaria control measures. There is a paucity of information on genetic structure of Plasmodium falciparum in Jharkhand, India where malaria is rampant and this study aimed to establish molecular characterization of P. falciparum field isolates from Jharkhand measured with two highly polymorphic genetic markers, i.e. the merozoite surface proteins (MSPs) 1 and 2.

METHODS

The genetic diversity of P. falciparum population from low transmission area, Ranchi, Bokaro and Hazaribagh and highly malarious area, Latehar and Palamau districts of Jharkhand were evaluated by polymerase chain reaction-sequencing analyzing msp-1 and msp-2 genes to explore the genetic structure of parasite from this understudied region.

RESULTS

A total of 134 P. falciparum isolates were analyzed by polymorphic regions of msp-1 and msp-2 and classified according to prevalence of allelic families. The majority of patients from all the five sites had mean monoclonal infections of 67·1 and 60·4% of P. falciparum for msp-1 and msp-2, respectively, whereas, mean multiple genotypes of 32·8 and 39·5% for msp-1 and msp-2, respectively. Interestingly, we observed higher multiclonal infection in low transmission area as compared to highly malarious area in the case of msp-1 genotypes, whereas in msp-2 higher multiclonal infection was observed in highly malarious area compared to low transmission area. The overall multiplicities of infection of msp-1 and msp-2 were 1·38 and 1·39, respectively.

CONCLUSION

This is the first report on molecular characterization of P. falciparum field isolates from Jharkhand. The genetic diversity and allelic distribution found in this study is somewhat similar to other reports from India and Southeast Asian countries. However, P. falciparum infection can be highly complex and diverse in these disease-endemic regions of Jharkhand, suggesting continual genetic mixing that could have significant implications for the use of antimalarial drugs and vaccines.

IgG subclass antibodies to three variants of Plasmodium falciparum merozoite surface protein-1 (PfMSP-1(19)) in an area with unstable malaria transmission in Iran

Plasmodium falciparum remains globally an important cause of mortality and morbidity and despite decades of research, no effective vaccine is available against this deadly parasite. The 19-kDa C-terminal fragment of P. falciparum merozoite surface protein 1 (PfMSP-1(19)) is a target for protective immunity against malaria and the major concern in development of vaccine based on this antigen is the presence of polymorphisms. This investigation was designed to evaluate naturally acquired antibodies and antigen-binding avidity of IgG antibodies to three variant forms of PfMSP-1(19) antigen (E/TSG/L, E/KNG/F and Q/KNG/L) in malaria individuals who are living in hypoendemic areas in Iran (n=92, 4-75 years old). The three variant forms of PfMSP-1(19) were expressed in Escherichia coli and IgG isotype composition and avidity of naturally acquired antibodies to the 19-kDa antigen were measured by ELISA assay. Results showed that almost 72% of the studied individuals had positive antibody responses to three PfMSP-1(19) variants and the prevalence of responders did not differ significantly (P>0.05). High-avidity IgG (62.7%, 65.7% and 47.76%) and IgG1 (64.2%, 50.75%, and 50.75%) were found in positive sera for E/TSG/L, E/KNG/F and Q/KNG/L variants, respectively. Moreover, the prevalence and titers of IgG1 antibody responses to the three variants increased with age (P<0.05). In summary, individuals in low transmission areas in Iran can develop and maintain equal immune responses with high avidity to the PfMSP-1(19) variants (E/TSG/L, E/KNG/F and Q/KNG/L); however, the precise role of the total IgG and its isotypes in protection requires further investigation. These results could support the design of a universal PfMSP-1(19)-based vaccine.

Malaria immunoepidemiology in low transmission: correlation of infecting genotype and immune response to domains of Plasmodium falciparum merozoite surface protein 3

Malaria caused by Plasmodium falciparum is a major cause of global infant mortality, and no effective vaccine currently exists. Multiple potential vaccine targets have been identified, and immunoepidemiology studies have played a major part in assessing those candidates. When such studies are carried out in high-transmission settings, individuals are often superinfected with complex mixtures of genetically distinct P. falciparum types, making it impossible to directly correlate the genotype of the infecting antigen with the antibody response. In contrast, in regions of low transmission P. falciparum infections are often genetically simple, and direct comparison of infecting genotype and antigen-specific immune responses is possible. As a test of the utility of this approach, responses against several domains and allelic variants of the vaccine candidate P. falciparum merozoite surface protein 3 (PfMSP3) were tested in serum samples collected near Iquitos, Peru. Antibodies recognizing both the conserved C-terminal and the more variable N-terminal domain were identified, but anti-N-terminal responses were more prevalent, of higher titers, and primarily of cytophilic subclasses. Comparing antibody responses to different PfMSP3 variants with the PfMSP3 genotype present at the time of infection showed that anti-N-terminal responses were largely allele class specific, but there was some evidence for responses that cross-reacted across allele classes. Evidence for cross-reactive responses was much stronger when variants within one allele class were tested, which has implications for the rational development of genotype-transcending PfMSP3-based vaccines.

Non-variant specific antibody responses to the C-terminal region of merozoite surface protein-1 of Plasmodium falciparum (PfMSP-119) in Iranians exposed to unstable malaria transmission

Background

The C-terminal region of Plasmodium falciparum merozoite surface protein-1 (PfMSP-1₁₉) is a leading malaria vaccine candidate antigen. However, the existence of different variants of this antigen can limit efficacy of the vaccine development based on this protein. Therefore, in this study, the main objective was to define the frequency of PfMSP-1₁₉ haplotypes in malaria hypoendemic region of Iran and also to analyse cross-reactive and/or variant-specific antibody responses to four PfMSP-1₁₉ variant forms.

Methods

The PfMSP-1₁₉ was genotyped in 50 infected subjects with P. falciparum collected during 2006-2008. Four GST-PfMSP-1₁₉ variants (E/TSR/L, E/TSG/L, E/KNG/F and Q/KNG/L) were produced in Escherichia coli and naturally occurring IgG antibody to these proteins was evaluated in malaria patients' sera (n = 50) using ELISA. To determine the cross-reactivity of antibodies against each PfMSP-1₁₉ variant in P. falciparum-infected human sera, an antibody depletion assay was performed in eleven corresponding patients' sera.

Results

Sequence data of the PfMSP-1₁₉ revealed five variant forms in which the haplotypes Q/KNG/L and Q/KNG/F were predominant types and the second most frequent haplotype was E/KNG/F. In addition, the prevalence of IgG antibodies to all four PfMSP-1₁₉ variant forms was equal and high (84%) among the studied patients' sera. Immunodepletion results showed that in Iranian malaria patients, Q/KNG/L variant could induce not only cross-reactive antibody responses to other PfMSP-1₁₉ variants, but also could induce some specific antibodies that are not able to recognize the E/TSG/L or E/TSR/L variant forms.

Conclusion

The present findings demonstrated the presence of non-variant specific antibodies to PfMSP-1₁₉ in Iranian falciparum malaria patients. This data suggests that polymorphism in PfMSP-1₁₉ is less important and one variant of this antigen, particularly Q/KNG/L, may be sufficient to be included in PfMSP-1₁₉-based vaccine.

Genetic structure of Plasmodium vivax and Plasmodium falciparum in the Bannu district of Pakistan

BACKGROUND

Plasmodium vivax and Plasmodium falciparum are the major causative agents of malaria. While knowledge of the genetic structure of malaria parasites is useful for understanding the evolution of parasite virulence, designing anti-malarial vaccines and assessing the impact of malaria control measures, there is a paucity of information on genetic diversity of these two malaria parasites in Pakistan. This study sought to shed some light on the genetic structure of P. vivax and P. falciparum in this understudied region.

METHODS

The genetic diversities of P. vivax and P. falciparum populations from the densely populated, malaria-endemic Bannu district of Pakistan were evaluated by analysis of their merozoite surface protein (msp) genes by PCR-RFLP. Specifically, the Pvmsp-3alpha and Pvmsp-3beta genes of P. vivax and the Pfmsp-1 and Pfmsp-2 genes of P. falciparum were analysed.

RESULTS

In P. vivax, genotyping of Pvmsp-3alpha and Pvmsp-3beta genes showed a high level of diversity at these loci. Four distinct allele groups: A (1.9 kb), B (1.5 kb), C (1.2 kb), and D (0.3 kb) were detected for Pvmsp-3alpha, type A being the most prevalent (82%). Conversely, amplification of the P. vivax msp-3beta locus produced two allele groups: A (1.7-2.2 kb, 62%) and B (1.4-1.5 kb, 33%), with 5% mixed-strain infections. Restriction analysis of Pvmsp-3alpha and Pvmsp-3beta yielded 12 and 8 distinct alleles, respectively, with a combined mixed genotype prevalence of 20%. In P. falciparum, all three known genotypes of Pfmsp-1 and two of Pfmsp-2 were observed, with MAD20 occurring in 67% and 3D7/IC in 65% of the isolates, respectively. Overall, 24% P. falciparum samples exhibited mixed-strain infections.

CONCLUSION

These results indicate that both P. vivax and P. falciparum populations in Pakistan are highly diverse.

The Plasmodium falciparum merozoite surface protein-1 19 KD antibody response in the Peruvian Amazon predominantly targets the non-allele specific, shared sites of this antigen

Background

Plasmodium falciparum re-emerged in Iquitos, Peru in 1994 and is now hypoendemic (< 0.5 infections/person/year). Purportedly non-immune individuals with discrete (non-overlapping) P. falciparum infections can be followed using this population dynamic. Previous work demonstrated a strong association between this population's antibody response to PfMSP1-19KD and protection against febrile illness and parasitaemia. Therefore, some selection for PfMSP1-19KD allelic diversity would be expected if the protection is to allele-specific sites of PfMSP1-19KD. Here, the potential for allele-specific polymorphisms in this population is investigated, and the allele-specificity of antibody responses to PfMSP1-19KD are determined.

Methods

The 42KD region in PfMSP1 was genotyped from 160 individual infections collected between 2003 and 2007. Additionally, the polymorphic block 2 region of Pfmsp1 (Pfmsp1-B2) was genotyped in 781 infection-months to provide a baseline for population-level diversity. To test whether PfMSP1-19KD genetic diversity had any impact on antibody responses, ELISAs testing IgG antibody response were performed on individuals using all four allele-types of PfMSP1-19KD. An antibody depletion ELISA was used to test the ability of antibodies to cross-react between allele-types.

Results

Despite increased diversity in Pfmsp1-B2, limited diversity within Pfmsp1-42KD was observed. All 160 infections genotyped were Mad20-like at the Pfmsp1-33KD locus. In the Pfmsp1-19KD locus, 159 (99.4%) were the Q-KSNG-F haplotype and 1 (0.6%) was the E-KSNG-L haplotype. Antibody responses in 105 individuals showed that Q-KNG and Q-TSR alleles generated the strongest immune responses, while Q-KNG and E-KNG responses were more concordant with each other than with those from Q-TSR and E-TSR, and vice versa. The immuno-depletion ELISAs showed all samples responded to the antigenic sites shared amongst all allelic forms of PfMSP1-19KD.

Conclusions

A non-allele specific antibody response in PfMSP1-19KD may explain why other allelic forms have not been maintained or evolved in this population. This has important implications for the use of PfMSP1-19KD as a vaccine candidate. It is possible that Peruvians have increased antibody responses to the shared sites of PfMSP1-19KD, either due to exposure/parasite characteristics or due to a human-genetic predisposition. Alternatively, these allelic polymorphisms are not immune-specific even in other geographic regions, implying these polymorphisms may be less important in immune evasion that previous studies suggest.

Plasmodium falciparum circumsporozoite protein: epidemiological variations among field isolates prevalent in India

OBJECTIVE

To investigate the extent of genetic variations in T-helper-cell epitopic regions of circumsporozoite (CS) protein in Plasmodium falciparum field isolates collected from different regions of India at different phases of malaria transmission.

METHODS

Genomic DNA was isolated from 507 P. falciparum wild-parasite isolates obtained from six geographical locations of India at three time points coinciding with malaria transmissions. The T-helper-cell epitopic regions were polymerase chain reaction (PCR)-amplified and the products were purified and then sequenced.

RESULTS

Based on sequences, nine variants were found among isolates and they were categorized into nine groups (V-1 to V-9), where V-1 and V-2 were observed in all three time points (TP). The variants V-1 to V-4 in TP-1; V-1, V-2, V-5 to V-8 in TP-2; and V-1, V-2, V-5 and V-9 in TP-3 were present and they showed restricted heterogeneity. During peak transmission (TP-2), parasite populations were more diverse and heterogeneous and the variants regionally unbiased and restricted. However, the alleles of V-6 and V-9 in both Th2R and Th3R showed identical sequence variation with those observed in other geographical regions of the world. The remaining seven groups did not show such similarity.

CONCLUSION

The Th2R and Th3R epitopes are implicated in host immune response to P. falciparum. The polymorphism in these epitopic regions indicates antigenic diversity, which may cause adverse outcome of a subunit vaccine including the CS prototype variant. Therefore, the formulation of a vaccine considering the restricted local repertoire parasite populations may be helpful.

Antibody responses to the merozoite surface protein-1 complex in cerebral malaria patients in India

BACKGROUND

Plasmodium falciparum infection causes cerebral malaria (CM) in a subset of patients with anti-malarial treatment protecting only about 70% to 80% of patients. Why a subset of malaria patients develops CM complications, including neurological sequelae or death, is still not well understood. It is believed that host immune factors may modulate CM outcomes and there is substantial evidence that cellular immune factors, such as cytokines, play an important role in this process. In this study, the potential relationship between the antibody responses to the merozoite surface protein (MSP)-1 complex (which consists of four fragments namely: MSP-1(83), MSP-1(30), MSP-1(38) and MSP-1(42)), MSP-6(36) and MSP-7(22) and CM was investigated.

METHODS

Peripheral blood antibody responses to recombinant antigens of the two major allelic forms of MSP-1 complex, MSP-6(36) and MSP-7(22) were compared between healthy subjects, mild malaria patients (MM) and CM patients residing in a malaria endemic region of central India. Total IgG and IgG subclass antibody responses were determined using ELISA method.

RESULTS

The prevalence and levels of IgG and its subclasses in the plasma varied for each antigen. In general, the prevalence of total IgG, IgG1 and IgG3 was higher in the MM patients and lower in CM patients compared to healthy controls. Significantly lower levels of total IgG antibodies to the MSP-1(f38), IgG1 levels to MSP-1(d83), MSP-1(19) and MSP-6(36) and IgG3 levels to MSP-1(f42) and MSP-7(22) were observed in CM patients as compared to MM patients.

CONCLUSION

These results suggest that there may be some dysregulation in the generation of antibody responses to some MSP antigens in CM patients and it is worth investigating further whether perturbations of antibody responses in CM patients contribute to pathogenesis.