HLA and elephantiasis in lymphatic filariasis

Indonesians Human Leukocyte Antigen (HLA) Distributions and Correlations with Global Diseases

In Human, Major Histocompatibility Complex known as Human Leukocyte Antigen (HLA). The HLA grouped into three subclasses regions: the class I region, the class II region, and the class III region. There are thousands of polymorphic HLAs, many of them are proven to have correlations with diseases. Indonesia consists of diverse ethnicity people and populations. It carries a unique genetic diversity between one and another geographical positions. This paper aims to extract Indonesians HLA allele data, mapping the data, and correlating them with global diseases. From the study, it is found that global diseases, like Crohn's disease, rheumatoid arthritis, Graves' disease, gelatin allergy, T1D, HIV, systemic lupus erythematosus, juvenile chronic arthritis, and Mycobacterial disease (tuberculosis and leprosy) suspected associated with the Indonesian HLA profiles.

Insights into the pathogenesis of disease in human lymphatic filariasis

Although two thirds of the 120 million people infected with lymph-dwelling filarial parasites have subclinical infections, ∼40 million have lymphedema and/or other pathologic manifestations including hydroceles (and other forms of urogenital disease), episodic adenolymphangitis, lymphedema, and (in its most severe form) elephantiasis. Adult filarial worms reside in the lymphatics and lymph nodes and induce lymphatic dilatation. Progressive lymphatic damage and pathology results primarily from the host inflammatory response to the parasites but also perhaps from the host inflammatory response to the parasite's Wolbachia endosymbiont and as a consequence of superimposed bacterial or fungal infections. This review will attempt to shed light on disease pathogenesis in lymphatic filariasis.

Immunopathogenesis of lymphatic filarial disease

Although two thirds of the 120 million people infected with lymph-dwelling filarial parasites have subclinical infections, ~40 million have lymphedema and/or other pathologic manifestations including hydroceles (and other forms of urogenital disease), episodic adenolymphangitis, tropical pulmonary eosinophilia, lymphedema, and (in its most severe form) elephantiasis. Adult filarial worms reside in the lymphatics and lymph nodes and induce changes that result in dilatation of lymphatics and thickening of the lymphatic vessel walls. Progressive lymphatic damage and pathology results from the summation of the effect of tissue alterations induced by both living and nonliving adult parasites, the host inflammatory response to the parasites and their secreted antigens, the host inflammatory response to the endosymbiont Wolbachia, and those seen as a consequence of secondary bacterial or fungal infections. Inflammatory damage induced by filarial parasites appears to be multifactorial, with endogenous parasite products, Wolbachia, and host immunity all playing important roles. This review will initially examine the prototypical immune responses engendered by the parasite and delineate the regulatory mechanisms elicited to prevent immune-mediated pathology. This will be followed by a discussion of the proposed mechanisms underlying pathogenesis, with the central theme being that pathogenesis is a two-step process-the first initiated by the parasite and host innate immune system and the second propagated mainly by the host's adaptive immune system and by other factors (including secondary infections).

Mendelian and complex genetics of susceptibility and resistance to parasitic infections

Uncovering the complex genetic basis of susceptibility and resistance to parasitic infectious diseases is an enormous challenge. It probably involves many different host genes, interacting with multiple parasite genetic and environmental factors. Several genes of interest have been identified by family and association studies in humans and by using mouse models, but more robust epidemiological studies and functional data are needed to authenticate these findings. With new technologies and statistical tools for whole-genome association analysis, the next few years are likely to see acceleration in the rate of gene discovery, which has the potential to greatly assist drug and vaccine development.

Polymorphisms of innate immunity genes and susceptibility to lymphatic filariasis

We examined 906 residents of an area of Papua New Guinea where bancroftian filariasis is endemic for genetic polymorphisms in three innate immunity genes suspected of contributing to susceptibility to infection and lymphatic pathology. Active infection was confirmed by the presence of blood-borne microfilariae and circulating filarial antigen in plasma. Disease was ascertained by physical examination for the presence of overt lymphedema (severe swelling of an arm or leg) or hydrocele. There was no association of infection status, lymphedema of an extremity, or hydrocele with chitotriosidase genotype (CHIT1). Polymorphisms of toll-like receptor-2 and toll-like receptor-4 genes (TLR4 A896G; TLR2 T2178A, G2258A) were not detected (N=200-625 individuals genotyped) except for two individuals heterozygous for a TLR2 mutation (C2029 T). These results indicate that a CHIT1 genotype associated previously with susceptibility to filariasis in residents of southern India and TLR2 and TLR4 polymorphisms do not correlate with infection status or disease phenotype in this Melanesian population.

Clustering of filarial infection in an age-graded study: genetic, household and environmental influences

A statistical method that analyses correlation structures in families to delineate the contribution of genetic, household and environmental factors on clustering of infection, has been applied to data collected in an area endemic for brugian filariasis in South Sulawesi, Indonesia. Infection was assessed both by microfilaraemia and by anti-filarial IgG4. The results confirmed earlier findings that genetic factors play an important role in clustering of infection. When clustering of infection was analysed in children (< 10 years of age) and adults (> 20 years of age) separately, it was found that the genetic factors influence clustering of infection in children more profoundly than environmental or household effects. In contrast, genetic factors could not fully explain the clustering of infection seen in adults, which seemed to be mainly determined by household and environmental effects. The data have implications for genotyping studies in brugian filariasis; they indicate that it may be important to concentrate on the younger age groups where individual environmental effects have not yet overruled the genetic influences on gain/loss of infection.

Genetics of susceptibility to human helminth infection

Recent studies have shown that host genetics is an important determinant of the intensity of infection and morbidity due to human helminths. Epidemiological studies of a number of parasite species have shown that the intensity of infection (worm burden) is a heritable phenotype. The proportion of variance in human worm burden explained by genetic effects varies from 0.21 to 0.44. Human genome scans have identified a locus responsible for controlling Schistosoma mansoni infection intensity on chromosome 5q31-q33, and loci controlling Ascaris lumbricoides intensity on chromosomes 1 and 13, although the genes involved have not yet been identified. There is also evidence for genetic control of pathology due to S. mansoni, and linkage has been reported to a region containing the gene for the interferon-gamma receptor 1 subunit. There is some evidence for genetic control of filarial infection, though little information on filarial disease. Association studies have provided evidence for major histocompatibility complex control of pathology in schistosomiasis and onchocerciasis. Recent candidate gene studies suggest a role of other immune response genes in controlling helminth infection and pathology, but require replication. Identification of the genetic loci involved may be important in the understanding of helminth epidemiology and the mechanisms of resistance and pathology.

Impact of parental onchocerciasis and intensity of transmission on development and persistence ofOnchocerca volvulusinfection in offspring: an 18 year follow-up study

This study analysed the impact and the extent by which parentalOnchocerca volvulusinfection, intensity of transmission ofO. volvulusinfective 3rd-stage larvae (L3) and anthropometric factors may influence the acquisition, development and persistence ofO. volvulusinfection in offspring. A total of 15 290 individuals in 3939 families with 9640 children were surveyed for microfilariae ofO. volvulus, and prevalence and level ofO. volvulusinfection in children aged 0 to 20 years from infected and non-infected parents were followed longitudinally for 18 years. Children fromO. volvulus-infected mothers had not only a substantially higher risk to become infected; they also acquired infection earlier in life and developed higher infection levels. Multiple logistic regression analysis showed that maternalO. volvulusinfection and children's age are the predominant predictors for patentO. volvulusinfection, while the intensity of transmission, measured by the annual transmission potential (ATP) ofO. volvulusL3, was less decisive. Longitudinal follow up of children showed that during vector control activities by the Onchocerciasis Control Programme (OCP) and in low-level transmission areas, infection persisted at higher levels in children fromO. volvulus-positive mothers. In summary, the dominant risk factor for children to become infected is maternal onchocerciasis, and also age-associated factors will strongly impact on the development of patentO. volvulusinfection in offspring.

Genetic variation in immune function and susceptibility to human filariasis

The generation of a draft sequence of a the human genome has provided the opportunity to characterize human diversity, even as it pertains to differences in host response to parasitic infection with organisms that cause lymphatic filariasis, malaria and schistosomiasis. Worldwide, human infection with filarial pathogens represents a significant cause of morbidity throughout the tropics. In particular, epidemiologic evidence suggests that a genetic component contributes to susceptibility and possibly the outcomes of filarial infection. Different approaches can be applied in population-based studies in areas where filarial infection is endemic, such as genome linkage scans and candidate gene analysis for the purpose of identifying genetic risk factors. This review summarizes recent advances in our understanding of genetic contributions to human lymphatic filariasis and addresses the immediate questions facing the field. It is anticipated that the identification of susceptibility genes in filarial infection could provide new insights into therapeutic strategies, including pharmacological intervention and vaccine development, and influence public health measures to control or avert infection.

Genetic polymorphisms in molecules of innate immunity and susceptibility to infection with Wuchereria bancrofti in South India

A pilot study was conducted to determine if host genetic factors influence susceptibility and outcomes in human filariasis. Using the candidate gene approach, a well-characterized population in South India was studied using common polymorphisms in six genes (CHIT1, MPO, NRAMP, CYBA, NCF2, and MBL2). A total of 216 individuals from South India were genotyped; 67 normal (N), 63 asymptomatic microfilaria positive (MF+), 50 with chronic lymphatic dysfunction/elephantiasis (CP), and 36 tropical pulmonary eosinophilia (TPE). An association was observed between the HH variant CHIT1 genotype, which correlates with decreased activity and levels of chitotriosidase and susceptibility to filarial infection (MF+ and CP; P = 0.013). The heterozygosity of CHIT1 gene was over-represented in the normal individuals (P = 0.034). The XX genotype of the promoter region in MBL2 was associated with susceptibility to filariasis (P = 0.0093). Since analysis for MBL-sufficient vs insufficient haplotypes was not informative, it is possible the MBL2 promoter association results from linkage disequilibrium with neighboring loci. We have identified two polymorphisms, CHIT1 and MBL2 that are associated with susceptibility to human filarial infection, findings that merit further follow-up in a larger study.

Adults acquire filarial infection more rapidly than children: a study in Indonesian transmigrants

To dissociate the influence of host age from length of exposure on acquisition of filarial infection, we examined the development of microfilaraemia and anti-filarial IgG4 in all ages of a naive population that became suddenly exposed to Brugia malayi as a result of transmigration. Responses in 247 transmigrants, who had settled for periods of several months up to 6 years in their new homesteads, were compared with those of 133 life-long residents. As shown in earlier studies, anti-filarial IgG4 increased with age in the indigenous populations, whose age is equivalent to length of exposure. However, by examining transmigrants, it became clear that development of specific IgG4 was influenced by age, since levels of this antibody were consistently higher in transmigrant adults than in transmigrant children, despite an equal length of exposure to filarial infection. Examining microfilaraemia, it was confirmed that infection establishes more rapidly in adults than in children.

Vaccination against helminth parasites--the ultimate challenge for vaccinologists?

Helminths are multicellular pathogens which infect vast numbers of human and animal hosts, causing widespread chronic disease and morbidity. Vaccination against these parasites requires more than identification of effective target antigens, because without understanding the immunology of the host-parasite relationship, ineffective immune mechanisms may be invoked, and there is a danger of amplifying immunopathogenic responses. The fundamental features of the immune response to helminths are therefore summarised in the context of vaccines to helminth parasites. The contention between type-1 and type-2 responses is a central issue in helminth infections, which bias the immune system strongly to the type-2 pathway. Evidence from both human and experimental animal infections indicates that both lineages contribute to immunity in differing circumstances, and that a balanced response leads to the most favourable outcome. A diversity of immune mechanisms can be brought to bear on various helminth species, ranging from antibody-independent macrophages, antibody-dependent granulocyte killing, and nonlymphoid actions, particularly in the gut. This diversity is highlighted by analysis of rodent infections, particularly in comparisons of cytokine-depleted and gene-targeted animals. This knowledge of protective mechanisms needs to be combined with a careful choice of parasite antigens for vaccines. Many existing candidates have been selected with host antibodies, rather than T-cell responses, and include a preponderance of highly conserved proteins with similarities to mammalian or invertebrate antigens. Advantage has yet to be taken of parasite genome projects, or of directed searches for novel, parasite-specific antigens and targets expressed only by infective stages and not mature forms which may generate immunopathology. With advances under way in parasite genomics and new vaccine delivery systems offering more rapid assessment and development, there are now excellent opportunities for new antihelminth vaccines.

HLA-DQ alleles associate with cutaneous features of onchocerciasis. The Kaduna-London-Manchester Collaboration for Research on Onchocerciasis

Onchocerciasis is associated with a spectrum of cutaneous changes, ranging from clinically normal skin to acute and chronic pathology. An important aspect of disease expression may be the level of immune response to parasite antigens, which is likely to be regulated by MHC-encoded molecules. We therefore investigated HLA class I and class II phenotypes in Nigerian residents of an area endemic for onchocerciasis. All study subjects were carefully characterized for parasite load and skin pathology. Individuals with depigmentation had increased frequencies of DQA1*0501 and DQB1*0301 compared with persons with normal skin and high microfilarial load (NSHMF) (Odds Ratios 3.6 (95% CI 1.0 to 13.2) and 3.8 (1.0 to 15.2), respectively). Conversely, individuals with depigmentation had a decreased frequency of DQA1*0101 and Cw6 compared with NSHMF (Odds Ratios 0.2 (0.1 to 0.9) and 0.1 (0.02 to 0.8), respectively). When NSHMF subjects were examined by age, a further decrease in DQA1*0501 frequency and increase in DQA1*0101 frequency were observed in older NSHMF individuals. These results strongly suggest that there is an immunogenetic basis for the spectrum of cutaneous presentations in onchocerciasis and that HLA-DQ molecules are associated with the level of immune response to parasite antigens.

Genetics of infectious disease resistance

The identification of large numbers of candidates genes and the introduction of methodologies for whole-genome screening have provided new opportunities for elucidating the molecular basis of variable susceptibility to major infectious diseases. 12 genes have been implicated in variable susceptibility to malaria and susceptibility/resistance genes for several other infectious diseases are beginning to be identified. Recent work suggests that large-scale family linkage and population association studies will be a more successful route to human disease genes than extrapolation from mouse models of infection.