Independent effects of genetic variations in mannose-binding lectin influence the course of HIV disease: the advantage of heterozygosity for coding mutations

Impact of MBL-2 coding region polymorphism on modulation of HAND and HIV-1 acquisition

BACKGROUND

Mannose-binding lectin 2 (MBL2) gene has a significant role in the essential protective mechanism of the body. Variations reported in the genetic makeup of this gene influence the circulating MBL levels that could lead to the vulnerability to various viral infections including HIV. Hence, we assessed the MBL2 coding region (52A/D, 54A/B, and 57A/C) variations in HIV-associated neurocognitive disorders (HAND).

METHOD

In this proposed study, 208 HIV seropositive individuals were included, 104 were on ART undergone for IHDS evaluation (44 HAND+60 without HAND), and 104 HIV seropositive individuals naïve to ART, and 130 unrelated HIV uninfected individuals. PCR-RFLP was used to genotype the MBL2 coding region polymorphism (52A/D, 54A/B and 57A/C).

RESULTS

MBL-2 57AC genotype was associated with risk of HAND severity (OR = 4.69, P = 0.0009). MBL-2 57AC and 57C alleles were associated with susceptibility to HAND (OR = 3.14, P = 0.003). Furthermore, the MBL-2 57AC genotype and 57C allele were found to be significantly linked with the susceptibility to HIV disease severity. (OR = 6.34, P = 0.001; 16.82% vs. 3.46%, OR = 5.64, P = 0.001). Haplotype ACA was significantly linked with susceptibility to HAND and its severity (OR = 3.23, P = 0.004, 26.1%-8.1%, OR = 4.70, P = 0.0024), similarly, haplotype ACA was linked with the acquisition of HIV-1 (OR = 4.26, P = 0.005). MBL-2 57AC genotype in presence of tobacco showed a significantly higher risk for HIV disease severity (48.0% vs. 12.5%, OR = 7.00, P = 0.035). Alcohol-taking HIV seropositive individuals on ART showed a greater MBL-2 57AC genotype than with alcohol-taking naïve to ART (32.3% vs. 15.4%, OR = 2.75, P = 0.40).

CONCLUSION

MBL-2 57AC genotype and haplotype ACA were associated with the modulation of HAND. Individuals with haplotype ACA were at higher risk of HIV-1 acquisition.

Mannose-binding lectin concentrations in people living with HIV/AIDS infected by HHV-8

Background

Mannose-binding lectin (MBL) plays an important role in the innate immune response by activating the complement system via the lectin pathway, and it has been studied in several viral infections; however, the influence of MBL in PLWHA infected with HHV-8 is unknown. The objective of this study was to verify the association of MBL deficient plasma concentrations in HIV/HHV-8 coinfected and HIV monoinfected patients and to correlate these concentrations with HIV viral load and CD4 counts in both groups.

Results

This was an analytical study of case-controls consisting of PLWHA monitored at the medical outpatient of Infectious and Parasitic Diseases of the clinical hospital in the Federal University of Pernambuco. Plasma concentrations of MBL were obtained by an enzyme-linked immunosorbent assay (ELISA) using a commercial Human Mannose Binding Lectin kit (MyBioSource, Inc.) that was performed according to the manufacturer’s guidelines, with values < 100 ng/ml considered deficient. A total of 245 PLWHA samples were analysed; 118 were HIV/HHV-8 coinfected and 127 were HIV monoinfected; 5.1% (6/118) of the coinfected patients and 3.2% (4/127) of the monoinfected patients (p = 0.445) were considered plasma concentration deficient. The median of the plasma concentrations of MBL in the coinfected patients was 2803 log₁₀ ng/ml and was 2.959 log₁₀ ng/ml in the monoinfected patients (p = 0.001). There was an inverse correlation between the plasma concentrations of MBL and the HIV viral load in both groups, but no correlation with the CD4 count.

Conclusions

Although the plasma concentrations considered deficient in MBL were not associated with HHV-8 infection in PLWHA, the coinfected patients showed lower MBL concentrations and an inverse correlation with HIV viral load, suggesting that there may be consumption and reduction of MBL due to opsonization of HIV and HHV-8, leading to the reduction of plasma MBL and non-accumulation in the circulation.

MBL2 gene polymorphisms in HHV-8 infection in people living with HIV/AIDS

Background

Host genetic factors such as MBL2 gene polymorphisms cause defects in the polymerization of MBL protein and result in a functional deficiency and/or in low serum levels that can influence susceptibility to various viral infections. The aim of this study was to estimate the frequency of alleles, genotypes and haplotypes related to -550, -221 and exon 1 polymorphisms of the MBL2 gene and investigate their association with HHV-8 in people living with HIV/AIDS (PLWHA), as well as the impacts on CD4 cell count and HIV viral load in HIV/HHV-8 coinfected and HIV monoinfected patients.

Results

A cross sectional study in PLWHA, with and without HHV-8 infection, exploring associations between different factors, was performed in the outpatient infectious and parasitic diseases clinic at a referral hospital. Genomic DNA extractions from leukocytes were performed using a commercial Wizard^®Genomic DNA Purification kit (Promega, Madison, WI). The promoter region (-550 and -221) was genotyped with the TaqMan system (Applied TaqMan Biosystems^® genotyping Assays), and the structural region (exon1) was genotyped with Express Sybr Greener Supermix kit (Invitrogen, USA). In total, 124 HIV/HHV-8 coinfected and 213 HIV monoinfected patients were analysed. Median TCD4 counts were significantly lower in HIV/HHV-8 coinfected patients, whereas the mean of the first and last viral load of HIV did not present significant difference. There was no difference in frequency between the LL, YY and AA genotypes between the HIV/HHV-8 coinfected or HIV monoinfected patients. However, in a multivariate analysis, coinfected patients with the intermediate expression haplotype of the MBL2 gene had an odds ratio of 3.1-fold (CI = 1.2–7.6) of their last CD4 cell count being below 350 cells/mm³. Among the coinfected individuals, four developed KS and presented the intermediate expression MBL haplotype, with three being HYA/LXA and one being LYA/LYO.

Conclusions

Host genetic factors, such as -550, -221 and exon 1 polymorphisms, can be related to the may modify coinfections and/or to the development clinical manifestations caused by HHV-8, especially in HIV/HHV-8 coinfected patients who present the intermediate expression haplotypes of MBL.

MBL2 genetic polymorphisms and HIV-1 mother-to-child transmission in Zambia

Since antiretroviral drugs have been introduced to prevent mother-to-child transmission, the risk of HIV-1 infection in infants has decreased considerably worldwide. Nevertheless, many factors are involved in viral transmission and host susceptibility to infection. The immune system and its components, including mannose binding protein C (encoding by MBL2 gene), are already known to play an important role in this scenario. In the present study, 313 children and 98 of their mothers from Zambia were genotyped for the MBL2 promoter HL (rs11003125) and XY (rs7096206) polymorphisms and exon 1 D (rs5030737, at codon 52) B (rs1800450, at codon 54) and C (rs1800451, at codon 57) polymorphisms in order to investigate the potential role of these genetic variants in HIV-1 mother-to-child transmission. No statistical significant association was observed comparing transmitter and non-transmitter mothers and also confronting HIV-positive and HIV-negative children. The findings of the current study obtained on mother and children from Zambia evidence lack of association between MBL2 functional polymorphisms and HIV-1 mother-to-child transmission.

Psoriasis risk SNPs and their association with HIV-1 control

Human evolution has resulted in selection for genetic polymorphisms beneficial in the defense against pathogens. However, such polymorphisms may have the potential to heighten the risk of autoimmune disease. Here, we investigated whether psoriasis-associated single nucleotide polymorphisms influence host control of HIV-1 infection. We studied psoriasis and viral immune response variants in three HIV-positive cohorts: (1) HIV-1 controllers and non-controllers in the Study of the Consequences of the Protease Inhibitor Era (SCOPE) cohort (n=366), (2) Individuals with primary HIV infection in the Options cohort (n=675), and (3) HIV-positive injection drug users from the Urban Health Study (UHS) (n=987). We found a strong association of two psoriasis MHC variants, rs9264942 and rs3021366, with both HIV-1 controller status and viral load, and identified another Class III MHC variant rs9368699 to be strongly associated with viral load. A number of genetic variants outside the MHC (SOX5, TLR9, SDC4, PROX1, IL12B, TLR4, MBL-2, TYK2, IFIH1) demonstrated nominal significance. Overall, our data suggest that several psoriasis variants within the MHC have a robust impact on HIV-1 control, while variants outside the MHC require further investigation.

HIV-1 Disease Progression and Survival in an Adult Population in Zimbabwe: Is There an Effect of the Mannose Binding Lectin Deficiency?

HIV infection remains a major global health burden since its discovery in 1983. Sub-Saharan Africa is the region hardest hit by the HIV/AIDS pandemic where 63% of the 33 million infected people live. While there is marked person-to-person variability in susceptibility, progression, and survival with HIV infection, there is a paucity of predictive diagnostics associated with these clinical endpoints. In this regard, the deficiency in plasma Mannose Binding Lectin (MBL) is a common opsonic defect reported to increase susceptibility infections, including HIV. To the best of our knowledge, we report here the first study on the putative role of MBL deficiency on HIV progression and survival in an African adult population. We hypothesized that MBL deficiency has a role to play in HIV infection by increasing HIV disease progression and decreasing survival. We assessed the role of MBL deficiency on HIV disease progression and survival in a Zimbabwean adult population enrolled in the Mupfure Schistosomiasis and HIV (MUSH) cohort. We analyzed blood samples for MBL levels, MBL2 genotypes, HIV-1 status, viral load, and CD4(+) T cell counts. Participants were followed for 3 years wherein the endpoints were measured at baseline, 6 weeks, and 3, 6, 12, 24, and 36 months. Disease progression was measured as the rate of decline in CD4(+) T cell counts and the rate of increase in HIV viral load. We assessed 197 HIV positive adults where 83% (164) were women with a median age of 31 years. Prevalence of plasma MBL deficiency (less than 100 μg/L) and MBL2 deficient genetic variants (A/O and O/O genotypes) was 21% (42 out of 197) and 39% (74 out of 190), respectively. We did not observe a significant role to explain individual variation in mortality, change of CD4(+) T cell count, and viral load by MBL plasma deficiency or MBL2 genetic variants from baseline to 3 years follow up period in this adult population. We suggest the need for global OMICS research and that the present findings attest to the large between-population variability in a host of factors that can predispose individuals susceptible to HIV progression and mortality. We therefore cannot recommend at this time the use of plasma MBL levels or MBL2 genetic variants as a prognostic marker in HIV infection, disease progression, and survival in this adult population in Africa.

Role of mannose-binding lectin deficiency in HIV-1 and schistosoma infections in a rural adult population in Zimbabwe

BACKGROUND

Polymorphism in the MBL2 gene lead to MBL deficiency, which has been shown to increase susceptibility to various bacterial, viral and parasitic infections. We assessed role of MBL deficiency in HIV-1 and schistosoma infections in Zimbabwean adults enrolled in the Mupfure Schistosomiasis and HIV Cohort (MUSH Cohort).

METHODS

HIV-1, S. haematobium and S. mansoni infections were determined at baseline. Plasma MBL concentration was measured by ELISA and MBL2 genotypes determined by PCR. We calculated and compared the proportions of plasma MBL deficiency, MBL2 structural variant alleles B (codon 54A>G), C (codon 57A>G), and D (codon 52T>C) as well as MBL2 promoter variants -550(H/L), -221(X/Y) and +4(P/Q) between HIV-1 and schistosoma co-infection and control groups using Chi Square test.

RESULTS

We assessed 379 adults, 80% females, median age (IQR) 30 (17-41) years. HIV-1, S. haematobium and S. mansoni prevalence were 26%, 43% and 18% respectively in the MUSH baseline survey. Median (IQR) plasma MBL concentration was 800μg/L (192-1936μg/L). Prevalence of plasma MBL deficiency was 18% with high frequency of the C (codon 57G>A) mutant allele (20%). There was no significant difference in median plasma MBL levels between HIV negative (912μg/L) and HIV positive (688μg/L), p = 0.066. However plasma MBL levels at the assay detection limit of 20μg/L were more frequent among the HIV-1 infected (p = 0.007). S. haematobium and S. mansoni infected participants had significantly higher MBL levels than uninfected. All MBL2 variants were not associated with HIV-1 infection but promoter variants LY and LL were significantly associated with S. haematobium infection.

CONCLUSION

Our data indicate high prevalence of MBL deficiency, no evidence of association between MBL deficiency and HIV-1 infection. However, lower plasma MBL levels were protective against both S. haematobium and S. mansoni infections and MBL2 promoter and variants LY and LL increased susceptibility to S. haematobium infection.

Human lectins and their roles in viral infections

Innate recognition of virus proteins is an important component of the immune response to viral pathogens. A component of this immune recognition is the family of lectins; pattern recognition receptors (PRRs) that recognise viral pathogen-associated molecular patterns (PAMPs) including viral glycoproteins. In this review we discuss the contribution of soluble and membrane-associated PRRs to immunity against virus pathogens, and the potential role of these molecules in facilitating virus replication. These processes are illustrated with examples of viruses including human immunodeficiency virus (HIV), hepatitis C virus (HCV) and Ebola virus (EBOV). We focus on the structure, function and genetics of the well-characterised C-type lectin mannose-binding lectin, the ficolins, and the membrane-bound CD209 proteins expressed on dendritic cells. The potential for lectin-based antiviral therapies is also discussed.

The lectin pathway of complement: advantage or disadvantage in HIV pathogenesis?

The pattern recognition molecules of the lectin complement pathway are important components of the innate immune system with known functions in host-virus interactions. This paper summarizes current knowledge of how these intriguing molecules, including mannose-binding lectin (MBL), Ficolin-1, -2 and -3, and collectin-11 (CL-11) may influence HIV-pathogenesis. It has been demonstrated that MBL is capable of binding and neutralizing HIV and may affect host susceptibility to HIV infection and disease progression. In addition, MBL may cause variations in the host immune response against HIV. Ficolin-1, -2 and -3 and CL-11 could have similar functions in HIV infection as the ficolins have been shown to play a role in other viral infections, and CL-11 resembles MBL and the ficolins in structure and binding capacity.

Lectin-dependent enhancement of Ebola virus infection via soluble and transmembrane C-type lectin receptors

Mannose-binding lectin (MBL) is a key soluble effector of the innate immune system that recognizes pathogen-specific surface glycans. Surprisingly, low-producing MBL genetic variants that may predispose children and immunocompromised individuals to infectious diseases are more common than would be expected in human populations. Since certain immune defense molecules, such as immunoglobulins, can be exploited by invasive pathogens, we hypothesized that MBL might also enhance infections in some circumstances. Consequently, the low and intermediate MBL levels commonly found in human populations might be the result of balancing selection. Using model infection systems with pseudotyped and authentic glycosylated viruses, we demonstrated that MBL indeed enhances infection of Ebola, Hendra, Nipah and West Nile viruses in low complement conditions. Mechanistic studies with Ebola virus (EBOV) glycoprotein pseudotyped lentiviruses confirmed that MBL binds to N-linked glycan epitopes on viral surfaces in a specific manner via the MBL carbohydrate recognition domain, which is necessary for enhanced infection. MBL mediates lipid-raft-dependent macropinocytosis of EBOV via a pathway that appears to require less actin or early endosomal processing compared with the filovirus canonical endocytic pathway. Using a validated RNA interference screen, we identified C1QBP (gC1qR) as a candidate surface receptor that mediates MBL-dependent enhancement of EBOV infection. We also identified dectin-2 (CLEC6A) as a potentially novel candidate attachment factor for EBOV. Our findings support the concept of an innate immune haplotype that represents critical interactions between MBL and complement component C4 genes and that may modify susceptibility or resistance to certain glycosylated pathogens. Therefore, higher levels of native or exogenous MBL could be deleterious in the setting of relative hypocomplementemia which can occur genetically or because of immunodepletion during active infections. Our findings confirm our hypothesis that the pressure of infectious diseases may have contributed in part to evolutionary selection of MBL mutant haplotypes.

Characterization of mannose-binding lectin plasma levels and genetic polymorphisms in HIV-1-infected individuals

INTRODUCTION

The present study investigated the association between mannose-binding lectin (MBL) gene polymorphism and serum levels with infection by HIV-1.

METHODS

Blood samples (5 mL) were collected from 97 HIV-1-infected individuals resident in Belém, State of Pará, Brazil, who attended the Special Outpatient Unit for Infections and Parasitic Diseases (URE-DIPE). CD4+ T-lymphocyte count and plasma viral load were quantified. A 349bp fragment of exon 1 of the MBL was amplified via PCR, using genomic DNA extracted from controls and HIV-1-infected individuals, following established protocols. MBL plasma levels of the patients were quantified using an enzyme immunoassay kit.

RESULTS

Two alleles were observed: MBL*O, with a frequency of 26.3% in HIV-1-infected individuals; and the wild allele MBL*A (73.7%). Similar frequencies were observed in the control group (p > 0.05). Genotype frequencies were distributed according to the Hardy-Weinberg equilibrium in both groups. Mean MBL plasma levels varied by genotype, with statistically significant differences between the AA and AO (p < 0.0001), and AA and OO (p < 0.001) genotypes, but not AO and OO (p = 0.17). Additionally, CD4+ T-lymphocytes and plasma viral load levels did not differ significantly by genotype (p > 0.05).

CONCLUSIONS

The results of this study do not support the hypothesis that MBL gene polymorphism or low plasma MBL concentrations might have a direct influence on HIV-1 infection, although a broader study involving a large number of patients is needed.

Host genetic polymorphisms associated with innate immune factors and HIV-1

PURPOSE OF REVIEW

Our understanding of the early events in HIV-1 infection continues to grow, along with the heightened recognition of the important contribution that innate immunity plays in response to HIV-1. Here, we review the epidemiological and functional studies of genetic polymorphisms associated with innate immune factors that are believed to modulate host responses, focusing specifically on recent findings related to Toll-like receptor, cytokine, host restriction and KIR genes and their activities.

RECENT FINDINGS

A growing number of genomic studies have described polymorphisms in innate immune genes that are associated with early postseroconversion events, including TLR4, TLR9, IRF-3, TRIM5α and the ABOBEC3 gene family. Genetic and functional data confirm the importance of KIR-HLA interactions and provide new understanding of the role of innate restriction factors in resistance to HIV-1 and disease progression.

SUMMARY

Single-gene, genome-wide association and expression studies have permitted the identification of innate immune genes and their variants that contribute to protection from disease progression. Characterization of the pathogen-innate immune system interactions and discovery of new and rare host genetic variants that account for a portion of the observed variance in the HIV-1 phenotype is critical to gain new insights into promising treatment and prevention strategies.

Genotypes coding for mannose-binding lectin deficiency correlated with cryptococcal meningitis in HIV-uninfected Chinese patients

Background. There is increasing evidence that mannose-binding lectin (MBL) has a complex role in many diseases, particularly in infectious diseases. However, the relationship between MBL deficiency and cryptococcal meningitis has not been clarified. The purpose of this study was to investigate the correlation between MBL polymorphism and non-HIV cryptococcal meningitis.

Methods. A case-controlled genetic association study was conducted. Patients with cryptococcal meningitis and control subjects were genotyped for 6 alleles of MBL2 gene (H/L, Y/X, P/Q, A/D, A/B, and A/C). The distributions in allele frequency, genotypes, haplotypes, and genotype groups were compared between patients and control subjects.

Results. Study participants included 103 HIV-uninfected patients with cryptococcal meningitis and 208 healthy control subjects, all of Chinese Han ethnicity. The homozygous mutative genotypes (O/O) of the coding region were associated with cryptococcal meningitis (P = .023; odds ratio [OR], 4.29; 95% confidence interval [CI], 1.11–19.88), the correlation more overt in immunocompetent patients (P = .005; OR, 6.65; 95% CI, 1.49–33.05). MBL-deficient participant group was associated with cryptococcal meningitis (P = .039; OR, 2.09; 95% CI, .96–4.51), particularly in immunocompetent patients (P = .028; OR, 2.51; 95% CI, .96–6.22).

Conclusions. This is the first to show genotypes coding for MBL deficiency are associated with cryptococcal meningitis in nonimmunocompromised hosts.

The emergence of human-evolutionary medical genomics

In this review, I describe how evolutionary genomics is uniquely suited to spearhead advances in understanding human disease risk, owing to the privileged position of genes as fundamental causes of phenotypic variation, and the ability of population genetic and phylogenetic methods to robustly infer processes of natural selection, drift, and mutation from genetic variation at the levels of family, population, species, and clade. I first provide an overview of models for the origins and maintenance of genetically based disease risk in humans. I then discuss how analyses of genetic disease risk can be dovetailed with studies of positive and balancing selection, to evaluate the degree to which the 'genes that make us human' also represent the genes that mediate risk of polygenic disease. Finally, I present four basic principles for the nascent field of human evolutionary medical genomics, each of which represents a process that is nonintuitive from a proximate perspective. Joint consideration of these principles compels novel forms of interdisciplinary analyses, most notably studies that (i) analyze tradeoffs at the level of molecular genetics, and (ii) identify genetic variants that are derived in the human lineage or in specific populations, and then compare individuals with derived versus ancestral alleles.

The role of mannose-binding lectin gene polymorphisms in susceptibility to HIV-1 infection in Southern Brazilian patients

OBJECTIVE

This study investigates the role of mannose-binding lectin (MBL) in the susceptibility to HIV-1 infection analyzing polymorphisms located at the MBL2 promoter and exon 1 regions.

MATERIALS AND METHODS

The prevalence of MBL2 variant alleles was investigated in 410 HIV-1-infected patients from the South Brazilian HIV cohort and in 345 unexposed uninfected healthy individuals. The promoter variants were genotyped using polymerase chain reaction with sequence-specific primers (PCR-SSP) and exon 1 variants were analyzed by real-time PCR using a melting temperature assay and were confirmed by PCR-restriction fragment length polymorphism (RFLP). MBL2 genotypic and allelic frequencies were compared between HIV-1-infected patients and controls using the chi-squared tests.

RESULTS

The analyses were performed subdividing the individuals according to their ethnic origin. Among Euro-derived individuals a higher frequency of the LX/LX genotype was observed in patients when compared to controls (P < 0.001). The haplotypic analysis also showed a higher frequency of the haplotypes associated with lower MBL levels among HIV-1-infected patients (P = 0.0001). Among Afro-derived individuals the frequencies of LY/LY and HY/HY genotypes were higher in patients when compared to controls (P = 0.009 and P = 0.02).

CONCLUSIONS

An increased frequency of MBL2 genotypes associated with low MBL levels was observed in Euro-derived patients, suggesting a potential role for MBL in the susceptibility to HIV-1 infection in Euro-derived individuals.

Torque teno virus viremia load size in patients with selected congenital defects of innate immunity

Plasma loads of torque teno virus (TTV) among individuals differ extensively beginning early in life, suggesting a role for innate immunity. Here, congenital mannose-binding lectin deficiencies, but not deficiencies in respiratory ciliary function, correlated with increased TTV loads. Notably, however, the presence of either disorder was associated with particularly high TTV loads.

Infections of people with complement deficiencies and patients who have undergone splenectomy

The complement system comprises several fluid-phase and membrane-associated proteins. Under physiological conditions, activation of the fluid-phase components of complement is maintained under tight control and complement activation occurs primarily on surfaces recognized as "nonself" in an attempt to minimize damage to bystander host cells. Membrane complement components act to limit complement activation on host cells or to facilitate uptake of antigens or microbes "tagged" with complement fragments. While this review focuses on the role of complement in infectious diseases, work over the past couple of decades has defined several important functions of complement distinct from that of combating infections. Activation of complement in the fluid phase can occur through the classical, lectin, or alternative pathway. Deficiencies of components of the classical pathway lead to the development of autoimmune disorders and predispose individuals to recurrent respiratory infections and infections caused by encapsulated organisms, including Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. While no individual with complete mannan-binding lectin (MBL) deficiency has been identified, low MBL levels have been linked to predisposition to, or severity of, several diseases. It appears that MBL may play an important role in children, who have a relatively immature adaptive immune response. C3 is the point at which all complement pathways converge, and complete deficiency of C3 invariably leads to severe infections, including those caused by meningococci and pneumococci. Deficiencies of the alternative and terminal complement pathways result in an almost exclusive predisposition to invasive meningococcal disease. The spleen plays an important role in antigen processing and the production of antibodies. Splenic macrophages are critical in clearing opsonized encapsulated bacteria (such as pneumococci, meningococci, and Escherichia coli) and intraerythrocytic parasites such as those causing malaria and babesiosis, which explains the fulminant nature of these infections in persons with anatomic or functional asplenia. Paramount to the management of patients with complement deficiencies and asplenia is educating patients about their predisposition to infection and the importance of preventive immunizations and seeking prompt medical attention.

Mannose-binding lectin (+54) exon-1 gene polymorphism influence human immunodeficiency virus-1 susceptibility in North Indians

Mannose-binding lectin (MBL) is a circulating pattern-recognition molecule involved in the innate immune system that mediates phagocytosis and activates complement by binding to carbohydrate motifs. MBL-2 allelic variants are associated with deficiencies in innate immunity and have been found to be correlated with human immunodeficiency virus (HIV) infection. The present study investigated the role of MBL-2 exon-1 gene polymorphism (A, B, C and D) in 180 HIV-1 seropositive (HSP) stratified on the basis of disease severity (stage I, II, III), 50 HIV-1 exposed seronegative (HES) and 305 HIV-1 seronegative (HSN) individuals as a possible factor in the susceptibility to HIV-1 infection and the influence on disease progression among North Indian individuals. In our population, gene frequencies of MBL-2 variants were 15%, 5% and 2% for B, C and D alleles, respectively. The frequency of A/O heterozygous genotype was higher (42.00%), mainly because of A/D in HES group compared with HSP (35.00%) and HSN (36.72%) group. Homozygous B/B genotype was more frequent in HSP (6.11%) group than in HSN (1.31%; P = 0.005; odds ratio (OR) = 4.898) and was significantly associated with fourfold risk of acquiring HIV-1 infection. Our findings indicate that homozygosity for the codon 54-allele associated with low MBL production in the exon-1 of the MBL-2 gene is associated with increased susceptibility to HIV-1 infection in the studied population.

APOE epsilon4 and MBL-2 O/O genotypes are associated with neurocognitive impairment in HIV-infected plasma donors

BACKGROUND

Host genetic factors are important determinants for risk of HIV-1 infection and disease progression. This study examined associations of host genetic variants and neurocognitive impairment in Chinese individuals infected through contaminated blood products.

METHODS

Two hundred and one HIV-infected patients from Anhui, China, had neuropsychological tests at baseline and 12 months. DNA was genotyped for APOE epsilon2, epsilon3 and epsilon4 alleles; MBL2-A/O; CCR5-wt/Delta32; CCR5-59029-G/A; CCR2-180-G/A; SDF-1-G/A; IL4-589-C/T; MCP-1-2518-A/G; CX3CR1-745-G/A; -849-C/T polymorphisms and CCL3L1 copy number variants using real-time PCR. Univariate and multivariate analyses were performed.

RESULTS

The cohort included 61% men, with mean education 5.5 years, AIDS diagnosis 113 (55%), on antiretrovirals 114 (56%), mean baseline CD4(+) cell count 349 cells/microl and mean log10 RNA 4.09. At baseline, 37% had global neuropsychological impairment increasing to 44% after 12 months. Of 43 patients with the APOE epsilon4 allele, 58% were cognitively impaired compared with 31% without the epsilon4 allele (P = 0.001, odds ratio 3.09, 95% confidence interval 1.54-6.18). The mean global deficit score (GDS) for epsilon4-positive participants on antiretrovirals for 12 months was 0.88 (0.55) compared with 0.63 (0.54) for epsilon4-negative participants (P = 0.053, 95% confidence interval -0.004 to 0.51). For MBL2, 52% of patients with the O/O genotype declined in cognitive function over 12 months compared with 23% with A/A (odds ratio 3.62, 95% confidence interval 1.46-9.03, P = 0.004). No associations were observed for the other genetic variants.

CONCLUSION

The APOE epsilon4 allele was associated with increased risk for cognitive deficits, whereas the MBL2 O/O genotype was associated with increased risk for progressive cognitive decline in Chinese individuals infected with HIV through contaminated blood products.

Association of mannose-binding lectin polymorphisms and HBV outcome in a South Indian population

Mannose binding lectin (MBL) is an important innate immune system pattern recognition molecule. The MBL gene polymorphisms are reported to play a crucial role in outcome of hepatitis B virus (HBV) infection. In this study, we ascertained the association of MBL genotypes with HBV outcome in a South Indian population. The MBL gene polymorphisms at codons 52, 54 and 57 of exon I, and promoter polymorphisms at -221 were typed by polymerase chain reaction-sequence specific primer in spontaneously recovered and in chronic HBV group. The allele frequency of codon 52 'C' was significantly higher in chronic HBV group than in the recovered group (98.5% vs. 93.6%; P = 0.003) and codon 52 'T' was significantly higher in recovered group than in the chronic group (6.4% vs. 1.5%; P = 0.003). In multivariate analysis, after adjusting for age, sex and state of origin, codon 52 'CC' and 'CT' genotypes were significantly associated with chronicity and recovery respectively [odds ratio (OR), 0.25; 95% confidence interval (CI), 0.08-0.80, P = 0.02] in co-dominant analyzing models. This was re-affirmed in analysis performed exclusively on Tamil Nadu subjects (OR, 0.23; 95% CI, 0.06-0.93, P = 0.039). The frequency of low/none haplotype (XY/O) was significantly higher in recovered group than in chronic group (15.6% vs 7.5%) and associated with spontaneous recovery (OR, 2.28; 95% CI, 1.04-4.99, P = 0.035). Our results provide preliminary evidence that inheritance of codon 52 genotypes and XY/O haplotype associated with low MBL level substantially determine the outcome of HBV infection in a sympatrically isolated South Indian population.

Double role of mannose-binding lectin in relation to carotid intima-media thickness in patients with rheumatoid arthritis

BACKGROUND

Patients with rheumatoid arthritis (RA) have increased risk of atherosclerosis and cardiovascular disease (CVD) that cannot be explained by excess of traditional risk factors. Several studies indicate that mannose-binding lectin (MBL) may modify the development of atherosclerosis; both high and low serum levels of MBL are reported to be associated with CVD. Intima-media thickness of the common carotid artery (ccIMT) is a validated non-invasive anatomic measure of subclinical CVD. We examined the relation between ccIMT and MBL in 114 RA patients.

METHODS

In a cross-sectional study MBL2 genotypes and serum concentrations of MBL were assessed; ccIMT was determined by means of ultrasonography; traditional and RA related cardiovascular risk modifiers were measured.

RESULTS

The median ccIMT was 0.67 mm. The investigated MBL2 genotypes were not significantly associated with ccIMT. Using a general linear model, ccIMT was not linearly associated with serum MBL but was highly associated with the quadratic term of serum MBL (MBL(2)) (P=0.001) reflecting a U-shaped relation. MBL(2) was also significantly associated with ccIMT in a multivariable analysis adjusting for traditional and RA related cardiovascular risk modifiers (P=0.025).

CONCLUSION

In RA patients, a quadratic U-shaped relation between serum MBL and ccIMT was observed independently of the effects of traditional and RA related risk factors for CVD. These results provide further support to the notion that both high and low levels of MBL may be associated with CVD.

Deficient serum mannose-binding lectin levels and MBL2 polymorphisms increase the risk of single and recurrent Cryptosporidium infections in young children

Mannose-binding lectin (MBL) is an evolutionarily conserved protein that functions in human innate immunity by binding to microbial surfaces and promoting opsonophagocytosis. MBL has been shown to bind to Cryptosporidium sporozoites, and earlier work has suggested that the protective role of MBL may be most important in childhood. We evaluated the association between polymorphisms in the MBL gene (MBL2), serum MBL deficiency, and infection with Cryptosporidium, Entamoeba histolytica, and Giardia intestinalis in children. A large, prospective cohort of Bangladeshi preschool children was followed up for >3 years. Clinical outcomes, serum MBL levels, and MBL2 polymorphisms and haplotypes were determined. Statistically significant associations with E. histolytica and G. intestinalis were not found. Serum MBL deficiency, polymorphisms in the -221 promoter region, and the YO/XA MBL2 haplotype were strongly associated with Cryptosporidium infections, particularly recurrent infection. Children with multiple infections with Cryptosporidium were more likely to be MBL deficient (odds ratio [OR], 10.45), carry the -221 promoter variant (OR, 4.02), and have the YO/XA haplotype (OR, 4.91). We have identified a potentially important component of the human innate immune response to Cryptosporidum infection. Further work is needed to evaluate the mechanism of protection of MBL in Cryptosporidium infection.

Association between mannose-binding lectin and HIV infection and progression in a Chinese population

Mannose-binding lectin (MBL) is a circulating pattern recognition molecule involved in the innate immune system that mediates phagocytosis and activates complement by binding to a carbohydrate extremity. Some MBL genetic polymorphisms result in deficient protein levels and increased susceptibility to infection. The objective of this study was to investigate the association between MBL2 exon 1 polymorphisms, serum levels of normal MBL, and HIV-1 infection and progression in a Chinese population. A total of 1075 adult patients infected with HIV-1 (532 male and 543 female) were recruited. The genotype of 145 patients was determined and the genotype frequencies compared with healthy population controls. The disease status of patients was evaluated for different MBL2 genotypes and normal MBL serum levels. MBL2 exon 1 polymorphisms (A/O or O/O) were significantly more common in HIV-1-infected patients than in the healthy controls. Patients in clinical categories B/C with severe diseases were significantly more likely to have one variant allele. There was a statistical relationship between MBL2 genotypes and MBL serum levels. In addition, higher CD4(+) T cell counts and ratios of CD4(+) T cells:CD8(+) T cells were observed in patients with medium MBL levels than with low or high MBL levels. Patients with mild diseases were also more likely to have medium MBL levels than high levels. Analysis of MBL levels with respect to sex yielded differences. Median MBL levels were substantially higher in males than in females in HIV-1-infected patients. Lower CD4(+) T cell counts were detected in males with low MBL levels, but the opposite was observed in females. Our results suggest that genetic polymorphisms resulting in MBL deficiency are associated with increased susceptibility to HIV-1 infection and disease progression in the studied population. Moreover, serum circulating levels of normal MBL in HIV-1-infected patients could be an important auxiliary biological marker in association with CD4(+) T cell counts in the evaluation of HIV-1 disease progression. The sex differences in the regulation of MBL serum levels during infection merit further exploration.

Mannose-binding lectin genetics: from A to Z

MBL (mannose-binding lectin) is primarily a liver-derived collagen-like serum protein. It binds sugar structures on micro-organisms and on dying host cells and is one of the four known mediators that initiate activation of the complement system via the lectin pathway. Common variant alleles situated both in promoter and structural regions of the human MBL gene (MBL2) influence the stability and the serum concentration of the protein. Epidemiological studies have suggested that genetically determined variations in MBL serum concentrations influence the susceptibility to and the course of different types of infectious, autoimmune, neoplastic, metabolic and cardiovascular diseases, but this is still a subject under discussion. The fact that these genetic variations are very frequent, indicates a dual role of MBL. This overview summarizes the current molecular understanding of human MBL2 genetics.

HIV-1 disease-influencing effects associated with ZNRD1, HCP5 and HLA-C alleles are attributable mainly to either HLA-A10 or HLA-B*57 alleles

A recent genome-wide association study (GWAS) suggested that polymorphisms in or around the genes HCP5, HLA-C and ZNRD1 confer restriction against HIV-1 viral replication or disease progression. Here, we also find that these alleles are associated with different aspects of HIV disease, albeit mainly in European Americans. Additionally, we offer that because the GWAS cohort was a subset of HIV-positive individuals, selected based in part on having a low viral load, the observed associations for viral load are magnified compared with those we detect in a large well-characterized prospective natural history cohort of HIV-1-infected persons. We also find that because of linkage disequilibrium (LD) patterns, the dominant viral load- and disease-influencing associations for the ZNRD1 or HLA-C and HCP5 alleles are apparent mainly when these alleles are present in HLA-A10- or HLA-B*57-containing haplotypes, respectively. ZNRD1 alleles lacking HLA-A10 did not confer disease protection whereas ZNRD1-A10 haplotypes did. When examined in isolation, the HCP5-G allele associates with a slow disease course and lower viral loads. However, in multivariate models, after partitioning out the protective effects of B*57, the HCP5-G allele associates with disease-acceleration and enhanced viral replication; these associations for HCP5-G are otherwise obscured because of the very strong LD between this allele and a subset of protective B*57 alleles. Furthermore, HCP5 and HLA-C alleles stratify B*57-containing genotypes into those that associate with either striking disease retardation or progressive disease, providing one explanation for the long-standing conundrum of why some HLA-B*57-carrying individuals are long-term non-progressors, whereas others exhibit progressive disease. Collectively, these data generally underscore the strong dependence of genotype-phenotype relationships upon cohort design, phenotype selection, LD patterns and populations studied. They specifically demonstrate that the influence of ZNRD1 alleles on disease progression rates are attributable to HLA-A10, help clarify the relationship between the HCP5, HLA-C and HLA-B*57 alleles, and reaffirm a critical role of HLA-B*57 alleles in HIV disease. Furthermore, as the protective B*57-containing genotypes convey striking salutary effects independent of their strong impact on viral control, it is conceivable that T cell-based therapeutic vaccine strategies aimed at reducing viral loads may be inadequate for limiting AIDS progression, raising the potential need for complementary strategies that target viral load-independent determinants of pathogenesis.