Polymorphism at codon 54 of mannose-binding protein gene influences AIDS progression but not HIV infection in exposed children

Association between mannose binding lectin gene polymorphisms and clinical severity of COVID-19 in children

BACKGROUND

Mannose-binding lectin (MBL) is a member of innate immunity and acts with MASP (MBL-associated serine protease) to activate the lectin pathway of the complement system. MBL gene polymorphisms are associated with susceptibility to infectious diseases. This study investigated whether MBL2 genotype, serum MBL levels, and serum MASP-2 levels affect the course of SARS-CoV-2 infection.

METHODS AND RESULTS

Pediatric patients diagnosed with COVID-19 by positive real-time polymerase chain reaction (PCR) were included in the study. Single nucleotide polymorphisms in the promoter and exon 1 in the MBL2 gene (rs11003125, rs7096206, rs1800450, rs1800451, rs5030737) were identified by a PCR and restriction fragment length polymorphisms analysis. Serum MBL and MASP-2 levels were measured by ELISA. COVID-19 patients were divided into asymptomatic and symptomatic. Variables were compared between these two groups. A total of 100 children were included in the study. The mean age of the patients was 130 ± 67.2 months. Of the patients, 68 (68%) were symptomatic, and 32 (32%) were asymptomatic. The polymorphisms in the - 221nt and - 550nt promoter regions did not differ between groups (p > 0.05). All codon 52 and codon 57 genotypes were determined as wild-type AA. AB genotypes were found 45.6% in symptomatic patients while 23.5% in asymptomatics. Moreover, BB genotype was detected 9.4% in symptomatic and 6.3% in asymptomatic patients (p < 0.001). B allele was more frequent in symptomatic patients (46.3%) compared to asymptomatic patients (10.9%). (p < 0.001). Serum MBL and MASP-2 levels did not differ statistically between the groups (p = 0.295, p = 0.073).

CONCLUSION

These findings suggest that codon 54 polymorphism in the MBL2 gene exon-1 region can be associated with the symptomatic course of COVID-19.

MBL2 gene polymorphisms related to HIV-1 infection susceptibility and treatment response

Human Mannose-binding lectin (MBL) is a protein encoded by MBL2 gene involved in the activation of the lectin-complement pathway. Several studies emphasized the role of MBL2 gene in several infectious diseases' susceptibility, including HIV-1 infection. We aim to investigate the impact of 10 MBL2 gene polymorphisms located in the promoter, 5'UTR and exon 1 regions on HIV-1 physiopathology. The polymorphisms genotyping of 400 individuals, which 200 were HIV-1 positive patients and 200 were controls, was performed by PCR-sequencing. Our results showed that rs503037 and rs1800451 polymorphisms are associated with a high risk of HIV-1 infection susceptibility while rs7096206 and rs11003123 showed a protective effect. A significant association between haplotype CGA and HIV-1 infection susceptibility was also found in the exon 1 region. Moreover, rs11003124, rs7084554, rs36014597 and rs11003123 polymorphisms revealed an association with treatment response outcome as measured by RNA viral load. This study highlights the importance of MBL2 polymorphisms in the modulation of HIV-1 infection susceptibility and the contribution to treatment response outcomes among Moroccan subjects.

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.

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.

HIV-1 Vertical Transmission in Zimbabwe in 622 Mother and Infant Pairs: Rethinking the Contribution of Mannose Binding Lectin Deficiency in Africa

Vertical transmission of human immunodeficiency virus (HIV) remains a major global health problem. We assessed the association of mannose binding lectin (MBL) deficiency and vertical transmission of HIV. Novel diagnostics would be a major breakthrough in this regard. MBL is a liver-derived protein and a key component of the innate immune system. MBL levels may be classified as normal, intermediate, or deficient in the plasma and can use MBL2 haplotypes as a proxy. These haplotypes comprise polymorphisms in the MBL2 gene and promoter region and are known to result in varying levels of MBL deficiency. MBL deficiency can be defined as presence of A/O and O/O genotypes in the mothers and their children. MBL deficiency leads to defective opsonization activities of the innate immune system and increased susceptibility to several infections, including HIV-1. We determined the prevalence of MBL deficiency, using MBL2 haplotypes among 622 HIV-positive Zimbabwean mothers and their children aged 9-18 months old, in relation to the HIV-1 vertical transmission risk. The median age of the mothers was 30 (26-34, interquartile range [IQR]) years, and the babies' median age was 13 (11-15, IQR) months old at the time of enrollment. From the sample of 622 mothers who were HIV-1 infected, 574 babies were HIV negative and 48 were HIV-1-positive babies, giving a transmission rate of 7.7%. MBL2 normal structural allele A and variants B (codon 5 A>G), C (codon 57 A>G), and promoter region SNPs -550(H/L) and -221(X/Y) were detected. Prevalence of haplotype-predicted MBL deficiency was 34% among the mothers and 32% among the children. We found no association between maternal MBL2 deficiency and HIV-1 transmission to their children. We found no difference in the distribution of HIV-1 infected and uninfected children between the MBL2 genotypes of the mothers and those of the children. Taken together, the present study in a large sample of mother-infant pairs in Zimbabwe adds to the emerging literature and the hypothesis that MBL2 variation as predicted by haplotypes does not influence the vertical transmission risk for HIV. Research from other populations from the African continent is called for to test this hypothesis further.

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.

HIV mother-to-child transmission: a complex genetic puzzle tackled by Brazil and Argentina research teams

Human immunodeficiency virus (HIV) mother-to-child transmission is a complex event, depending upon environmental factors and is affected by host genetic factors from mother and child, as well as viral genetic elements. The integration of multiple parameters (CD4 cell count, virus load, HIV subtype, and host genetic markers) could account for the susceptibility to HIV infection, a multifactorial trait. The goal of this manuscript is to analyze the immunogenetic factors associated to HIV mother-to-child transmission, trying to unravel the genetic puzzle of HIV mother-to-child transmission and considering the experience in this topic of two research groups from Brazil and Argentina.

Mannose-binding lectin and the risk of HIV transmission and disease progression in children: a systematic review

BACKGROUND

Mannose-binding lectin (MBL) can activate the complement system by binding to carbohydrates, such as those presented on the HIV virion surface. It is unclear whether genetically determined MBL deficiency is related to vertical HIV transmission and disease progression in HIV-infected children.

METHODS

A literature search of Medline, Embase and Cochrane Central Register identified all relevant studies on MBL and HIV infection in children. We extracted information on the characteristics of the study group, method of MBL analysis, outcome definitions, follow-up and the risk estimates. The validity of each study was assessed.

RESULTS

Nine studies were retrieved. Most were of good validity, but risk adjustment for confounders was missing in 6 studies. Age, treatment and outcome definitions differed between the study groups. In most of the studies, MBL deficiency was associated with an increased frequency of vertical HIV transmission and an increased speed of disease progression. In the 2 most valid studies, carriers of variant genes had an increased odds ratio for transmission and an increased relative hazard for disease progression and central nervous system impairment, especially in children <2 years of age.

CONCLUSIONS

MBL deficiency is associated with an increased risk of vertical HIV transmission. How this risk relates to other factors that influence transmission is unclear. The association between HIV disease progression and MBL deficiency is most pronounced in children <2 years of age, probably due to immaturity of their adaptive immunity.

Host polymorphism in steps of the HIV-1 lifecycle after entry and other genetic variants influencing HIV-1 pathogenesis

PURPOSE OF REVIEW

Dominant host factors modifying the susceptibility to HIV-1 include diversity in the major histocompatibility complex class I, and alleles of chemokine and chemokine receptor genes. Additional host factors, particularly those determining cell permissiveness to viral replication, are expected to play a significant role in HIV-1 pathogenesis.

RECENT FINDINGS

A growing number of publications (n = 32) propose new variants (n = 27) modifying HIV-1 susceptibility in genes (n = 17) needed for the viral lifecycle, in antiviral innate defense, and in a number of soluble and membrane proteins.

SUMMARY

Although there are multiple publications describing putative associations of host genetic variants and susceptibility to HIV-1, most reports are yet to be confirmed by subsequent publications, or have led to conflicting data among laboratories.

HIV-1 control in battlegrounds: important host genetic variations for HIV-1 mother-to-child transmission and progression to clinical pediatric AIDS

HIV-1 mother-to-child transmission (MTCT) is the passing of maternal HIV-1 to the offspring during pregnancy, labor and delivery, and/or breastfeeding. HIV-1 MTCT and the evolution to pediatric AIDS are multifactorial, dynamic and variable phenotypic conditions. Both genetic and nongenetic variables can influence susceptibility to HIV-1 MTCT or the rate of progression to clinical pediatric AIDS. In this review, we summarize the current state of knowledge about the roles of genetic variations seen in host immune response genes, and those that have been independently associated, mostly through population genetics of candidate genes, with interindividual susceptibility to HIV-1 MTCT, and progression to pediatric AIDS. We examine common and rare host genetic variations at coding and noncoding polymorphisms, whether functional or not, in agonists and antagonists of the immune response, which have been implicated in HIV-1 control in battlegrounds of cell entry, replication and evolution to AIDS. Further, we point to over 380 single-nucleotide polymorphisms, mostly within the HLA super region, recently identified in unbiased genome-wide association studies of HIV replication and evolution in adults, still unexplored in the context of HIV-1 MTCT, and which are likely to also influence susceptibility to pediatric HIV-1/AIDS.

Human immunodeficiency virus type 1 mother-to-child transmission and prevention: successes and controversies

The World Health Organization (WHO) and United Nations Programme on HIV/AIDS (UNAIDS) estimated that an additional 370 000 new human immunodeficiency virus type 1 (HIV-1) infections occurred in children in 2009, mainly through mother-to-child transmission (MTCT). Intrapartum transmission contributes to approximately 20-25% of infections, in utero transmission to 5-10% and postnatal transmission to an additional 10-15% of cases. MTCT accounts for only a few hundred infected newborns in those countries in which services are established for voluntary counselling and testing of pregnant women, and a supply of antiretroviral drugs is available throughout pregnancy with recommendations for elective Caesarean section and avoidance of breastfeeding. The single-dose nevirapine regimen has provided the momentum to initiate MTCT programmes in many resource-limited countries; however, regimens using a combination of antiretroviral drugs are needed also to effectively reduce transmission via breastfeeding.

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.

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.

Recombinant form of human wild type mannan-binding lectin (MBL/A) but not its structural variant (MBL/C) promotes phagocytosis of zymosan by activating complement

Mannan-binding lectin (MBL) mediates innate immune responses, such as activation of the complement lectin pathway and phagocytosis, to help fight infections. In the present study, employing recombinant forms of human MBL (rMBL), the role of wild type MBL (rMBL/A) and its structural variant rMBL/C in mediating THP-1 phagocytosis of fluorescent-labeled zymosan was examined and compared to MBL purified from human plasma (pMBL/A). Flow cytometric analyses revealed that opsonization of zymosan with rMBL/A and pMBL/A (0.5-30microg/ml) resulted in a 1.9- and 2.7-fold enhancement in its uptake by THP-1 cells in the presence of serum that was depleted of both MBL and the classical pathway component, C1q (MBL/C1q Dpl serum). In contrast, no enhancement in phagocytosis was observed when zymosan was opsonized with rMBL/C. Addition of MBL monoclonal antibody, EDTA, or mannan to the opsonization reaction mixture inhibited THP-1 phagocytosis of pMBL/A opsonized zymosan. Heat inactivation of MBL/C1q Dpl serum abolished the 2-fold increase in phagocytosis and in the absence of serum the direct opsonic activity of MBL did not contribute significantly to the uptake of zymosan into THP-1 cells. Activation products of complement components C3 and C4 were deposited on zymosan opsonized with pMBL/A and rMBL/A but not rMBL/C indicating that MBL-mediated phagocytosis of zymosan requires activation of the complement lectin pathway. The findings imply that impaired MBL-mediated phagocytosis may put individuals homozygous for the mutant allele MBL/C but not wild type MBL/A at increased risk to infections such as yeast.

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.

Association between HLA-G 3'UTR 14-bp polymorphism and HIV vertical transmission in Brazilian children

OBJECTIVES

The aim of our study was to verify the possible association between an HLA-G 14-bp deletion/insertion polymorphism and perinatal HIV transmission in Brazilian children.

DESIGN

We analyzed the 14-bp deletion/insertion polymorphisms in seronegative (i.e., exposed uninfected, N = 71) and seropositive (exposed infected, N = 175) Brazilian children born from HIV-positive mothers and in healthy controls (n = 175).

METHODS

HLA-G 14-bp deletion/insertion polymorphism (rs16375) was detected by PCR amplification of the target sequence followed by agarose gel electrophoresis. All the samples were also analyzed by direct sequencing in order to validate the genotyping results.

RESULTS

HIV-exposed uninfected children showed significant differences in their allele and genotype frequencies of the HLA-G 14-bp polymorphism when compared to both seropositive children and healthy controls. The 14-bp-deleted (D) allele was more frequent in exposed uninfected children (79%) than in healthy controls (60%) and HIV-positive children (58%); the higher percentage of the D allele found in the exposed uninfected children with respect to HIV-positive individuals was significantly associated with a reduced risk of vertical transmission. This effect was ascribable to the presence of the D/D homozygous genotype.

CONCLUSION

Our findings support the possible role for the HLA-G 14-bp deletion/insertion polymorphism in the HIV vertical transmission in Brazilian children. The presence of the D allele and D/D genotype is associated with a protective effect toward HIV perinatal infection.

Detrimental effects of mannose-binding lectin (MBL2) promoter genotype XA/XA on HIV-1 vertical transmission and AIDS progression

BACKGROUND

The literature on the involvement of mannose-binding lectin (MBL) in human immunodeficiency virus (HIV) transmission and acquired immunodeficiency syndrome (AIDS) is conflicting. Polymorphisms in the MBL2 gene reduce the level of protein and alter its structure. Thus, we investigated whether MBL2 alleles and plasma concentrations of MBL are associated with perinatal HIV transmission and disease progression.

METHODS

Frequencies of MBL2 allelic variants (B, C, D, and X) were estimated among 345 HIV-exposed children and 147 blood donors. AIDS-free time was evaluated for different MBL2 genotypes and MBL plasma levels. The median duration of follow-up was 96.5 months.

RESULTS

In the Argentinean population, gene frequencies of MBL2 variants were 18%, 15%, and 3% for the X, B, and D alleles, respectively, with no identified C allele. The haplotype XA/XA was associated with an 8-fold risk of acquiring HIV-1 (P= .054; odds ratio [OR], 8.11 [95% confidence interval {CI}, 0.96-67.86]) and almost a 3-fold risk of progression to pediatric AIDS (P= .026; OR, 2.81 [95% CI, 1.14-7.47]). We also found an independent positive correlation between the rate of AIDS progression and MBL plasma concentration (P= .008; OR, 1.28 [95% CI, 1.07-1.55]).

CONCLUSIONS

Our results demonstrate that homozygosity for the MBL2 promoter genotype XA/XA is an important genetic determinant of HIV-1 acquisition through vertical transmission and the pathogenesis of pediatric HIV/AIDS, via a mechanism that remains to be established.

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

BACKGROUND

The in vivo impact of mannose-binding lectin (MBL), a molecule involved in innate immunity, on the pathogenesis of human immunodeficiency virus (HIV)-1 infection and AIDS is unknown.

METHODS

A total of 1102 HIV-positive and 2213 HIV-negative adult subjects were screened for polymorphisms in the coding and promoter regions of MBL2, the gene that encodes MBL.

RESULTS

Variations in MBL2 did not influence the risk of acquiring HIV-1. Heterozygosity for coding mutations (O allele) and homozygosity for the -221 promoter polymorphism (X allele) in MBL2 were associated with a delay in and an accelerated rate of disease progression, respectively. MBL2 variations influenced the rate of progression to AIDS-defining illnesses. In a multivariate model, the effects of MBL2 variations were independent of several parameters known to influence disease progression, including steady-state viral load, baseline CD4(+) T cell counts, and delayed-type hypersensitivity skin test responses, an in vivo marker of cell-mediated immunity. The effects of MBL2 variations were most evident in those who possessed protective genotypes of CCR5 and a high copy number of CCL3L1, the most potent HIV-suppressive CCR5 ligand.

CONCLUSIONS

MBL2 genotypes are independent determinants of HIV disease progression and heterozygosity for MBL2 coding mutations confer disease-retarding effects. MBL-dependent immune responses may play a role in the pathogenesis of HIV infection.

Mannose-binding lectin in HIV infection

Infection with HIV represents a significant global health problem, with high infection rates and high mortality worldwide. Treatment with antiretroviral therapy is inaccessible to many patients and efficacy is limited by development of resistance and side effects. The interactions of HIV with the human immune system, both innate and humoral, are complex and complicated by the profound ability of the virus to disable the host immune response. Mannose-binding lectin, a component of the innate immune system, has been demonstrated to play a role in host-virus interactions. This protein may have a key role in determining host susceptibility to infection, pathogenesis and progression of disease, and may contribute to the extensive variability of host response to infection. Further understanding and manipulation of the mannose-binding lectin response may represent a target for immunomodulation in HIV infection, which may, in conjunction with highly active antiretroviral therapy, allow development of a novel therapeutic approach to HIV infection.

Mannose binding lectin gene variants and susceptibility to tuberculosis in HIV-1 infected patients of South India

Mannose binding lectin (MBL) plays an important role in innate immunity. Plasma MBL levels and MBL2 gene polymorphisms were studied in HIV-1 infected patients without tuberculosis (HIV+TB-) (n=151) and with tuberculosis (HIV+TB+) (n=109), HIV negative tuberculosis patients (HIV-TB+) (n=148) and healthy controls (n=146) by ELISA and genotyping by polymerase chain reaction based methods. MBL levels were significantly increased among HIV-TB+ and HIV+TB+ patients than controls and HIV+TB- patients (P<0.05). A significantly increased frequency of OO genotype of structural polymorphism and YY genotype of -221Y/X was observed among HIV-TB+ patients than controls. In HIV+TB+ patients, a significantly increased frequency of YA/YA diplotype (associated with very high MBL levels) was observed compared to controls (P=0.03). In HIV+TB+ patients, a significantly decreased frequency of medium MBL expression diplotypes (XA/XA and YA/YO) were noticed compared to HIV+TB- and healthy controls. The results suggest that YA/YA diplotype associated with very high MBL levels may predispose HIV-infected patients to tuberculosis while O/O genotype associated with very low MBL levels may be associated with susceptibility to tuberculosis in HIV uninfected individuals. Medium MBL expression diplotypes might protect against development of TB in HIV-infected patients.

Mannose-binding lectin in innate immunity: past, present and future

The human collectin, mannose‐binding lectin (MBL), is an important protein of the humoral innate immune system. With multiple carbohydrate‐recognition domains, it is able to bind to sugar groups displayed on the surfaces of a wide range of microorganisms and thereby provide first‐line defence. Importantly, it also activates the complement system through a distinctive third pathway, independent of both antibody and the C1 complex. Three single point mutations in exon 1 of the expressed human MBL‐2 gene appear to impair the generation of functional oligomers. Such deficiencies of functional protein are common in certain populations, e.g. in sub‐Saharan Africa, but virtually absent in others, e.g. indigenous Australians. MBL disease association studies have been a fruitful area of research and implicate a role for MBL in infective, inflammatory and autoimmune disease processes. Overall, there appears to be a genetic balance in which individuals generally benefit from high levels of the protein. However, in certain situations, reduced levels of circulating MBL may be beneficial to the host and this may explain the persistence of the deleterious gene polymorphisms in many population groups.

Synergy between mannose-binding lectin gene polymorphisms and supplementation with vitamin A influences susceptibility to HIV infection in infants born to HIV-positive mothers

BACKGROUND

Mannose-binding lectin (MBL-2) allele variants are associated with deficiencies in innate immunity and have been found to be correlated with HIV infection in adults and children.

OBJECTIVE

We tested whether MBL-2 variants among infants born to HIV-positive mothers have an increased susceptibility to HIV.

DESIGN

MBL-2 allele variants were measured among 225 infants born to HIV-positive mothers enrolled in a trial in Durban, South Africa. Mothers of 108 infants were randomly assigned to receive vitamin A and beta-carotene supplementation and 117 to receive placebo. Infants were followed with regular HIV tests to determine rates of mother-to-child HIV transmission.

RESULTS

A high proportion of infants were either homozygous (10.7%) or heterozygous (32.4%) for MBL-2 variants. MBL-2 variants within the placebo arm were associated with an increased risk of HIV transmission (odds ratio: 3.09; 95% CI: 1.21, 7.86); however, MBL-2 variants within the supplementation arm were not associated with an increased risk of transmission (P = 0.04; test of interaction). Among infants with MBL-2 variants, supplementation was associated with a decreased risk of HIV transmission (odds ratio: 0.37; 95% CI: 0.15, 0.91).

CONCLUSION

We observed what appears to be a gene-environment interaction between MBL-2 variants and an intervention with vitamin A plus beta-carotene that is relevant to mother-to-child HIV transmission.

A cost-effective melting temperature assay for the detection of single-nucleotide polymorphism in the MBL2 gene of HIV-1-infected children

We report a fast (less than 3 h) and cost-effective melting temperature assay method for the detection of single-nucleotide polymorphisms in the MBL2 gene. The protocol, which is based on the Corbett Rotor Gene real time PCR platform and SYBR Green I chemistry, yielded, in the cohorts studied, sensitive (100%) and specific (100%) PCR amplification without the use of costly fluorophore-labeled probes or post-PCR manipulation. At the end of the PCR, the dissociation protocol included a slow heating from 60 degrees to 95 degrees C in 0.2 degrees C steps, with an 8-s interval between steps. Melting curve profiles were obtained using the dissociation software of the Rotor Gene-3000 apparatus. Samples were analyzed in duplicate and in different PCR runs to test the reproducibility of this technique. No supplementary data handling is required to determine the MBL2 genotype. MBL2 genotyping performed on a cohort of 164 HIV-1-positive Brazilian children and 150 healthy controls, matched for age and sex and ethnic origin, yielded reproducible results confirmed by direct sequencing of the amplicon performed in blind. The three MBL2 variants (Arg52Cys, Gly54Asp, Gly57Glu) were grouped together and called allele 0, while the combination of three wild-type alleles was called allele A. The frequency of the A/A homozygotes was significantly higher among healthy controls (0.68) than in HIV-infected children (0.55; P = 0.0234) and the frequency of MBL2 0/0 homozygotes was higher among HIV-1-infected children than healthy controls (P = 0.0296). The 0 allele was significantly more frequent among the 164 HIV-1-infected children (0.29) than among the 150 healthy controls (0.18; P = 0.0032). Our data confirm the association between the presence of the mutated MBL2 allele (allele 0) and HIV-1 infection in perinatally exposed children. Our results are in agreement with the literature data which indicate that the presence of the allele 0 confers a relative risk of 1.37 for HIV-1 infection through vertical transmission.

Mannose-Binding Lectin in Susceptibility and Progression of HIV-1 Infection in Children

Background

Mannose-binding lectin (MBL; encoded by MBL-2) is a circulating pattern-recognition molecule that recognizes microbial carbohydrate motifs, leading to complement activation and cell lysis. Mutations in the MBL-2 promoter and of the MBL-2 gene exon 1 result in reduced protein levels and increased susceptibility to infection. We have investigated the effect of MBL-2 polymorphisms on susceptibility and progression of HIV-1 infection in children.

Patients and methods

One-hundred and twenty-eight children, aged 2–16 years were recruited. MBL-2 genotypes were determined by PCR and heteroduplex analyses. Serum MBL levels were measured by ELISA. Comparison of genotypes (A=wild type, 0=variant alleles) and protein levels between groups was performed using χ2, Mann–Whitney U or Kruskal–Wallis tests.

Results

Children were classified according to the Centers for Disease Control and Prevention clinical classification: A, B or C (mildly symptomatic [ n=39], moderately symptomatic [ n=58] or severely symptomatic AIDS [ n=31]) or immune category 1 ( n=77), 2 ( n=46) or 3 ( n=5). Analysis of MBL-2 genotypes with respect to clinical classification yielded minimal differences. However, patients in immunological categories 2 and 3 (<25% CD4+ T cells) were more likely to have MBL-2 variant alleles ( P=0.01). We further explored MBL status with respect to disease progression. Only 1/10 long-term non-progressors (LTNPs) had an MBL-2 mutation (A/D) with a corresponding protein level of 611 ng/ml.

Conclusions

MBL deficiency was more frequent in patients with severe disease as assessed by CD4+ T-cell status. MBL-2 variants may be less frequent in children classified as LTNPs. MBL analysis could be useful in identifying children with slow disease progression and, consequently, may not require immediate antiretroviral treatement.

Host genetics of HIV-1 susceptibility

Susceptibility to HIV-1 and the rate of disease progression reflect the influence of the genetic diversity of the virus as well as the variation in host factors. The virus will co-evolve with the host, escaping and adapting to host-determined influences. Dominant host factors currently identified include diversity in the major histocompatibility complex class I, and alleles of chemokine, chemokine receptor and cytokine genes. Recent work proposes new variants in life cycle genes and in antiviral innate defense, which modify HIV-1 susceptibility. Comparative genomics generates information on host cell barriers that may explain the current distribution of these viruses among human and nonhuman primates. A greater understanding of the genetic basis of human susceptibility to HIV-1 contributes to an understanding of the pathogenesis of the disease, helps identify new targets for prophylaxis and vaccine development and will lead to predictive tools to identify those at risk of rapid disease progression.

Haplotype analysis of the SDF-1 (CXCL12) gene in a longitudinal HIV-1/AIDS cohort study

The stromal-derived factor-1 (SDF-1) chemokine gene encodes the only natural ligand for CXCR4, the coreceptor for the pathogenic X4 HIV-1 strains. A single-nucleotide polymorphism (SNP) in the 3' untranslated region (SDF1-3'A=rs1801157) of SDF-1 was reported to be protective against infection and progression in some, but not other, epidemiological studies. To identify additional alleles that may influence HIV-1 infection and progression to AIDS, nine SNPs (including rs1801157) spanning 20.2 kb in and around the SDF-1 gene were genotyped in over 3000 African American (AA) and European American (EA) participants enrolled in five longitudinal HIV-1/AIDS natural cohort studies. Six or five haplotypes were present at frequencies greater than 5% in AA or EA, respectively. Six of the nine SNPs occur on only one common haplotype (>5%), while the remaining three SNPs were found on multiple haplotypes, suggesting a complex history of recombination. Among EA, rs754618 was associated with an increased risk of infection (OR=1.50, P=0.03), while rs1801157 (=SDF1-3'A) was associated with protection against infection (OR=0.63, P=0.01). In the MACS cohort, rs1801157 was associated with AIDS-87 (RH=0.31, P=0.02) and with death (RH=0.18, P=0.02). Significant associations to a single disease outcome were found for two SNPs and one haplotype in AA.

Impact of Mannose-Binding Lectin on Susceptibility to Infectious Diseases

When the adaptive immune response is either immature or compromised, the innate immune system constitutes the principle defense against infection. Mannose-binding lectin (MBL) is a C-type serum lectin that plays a central role in the innate immune response. MBL binds microbial surface carbohydrates and mediates opsonophagocytosis directly and by activation of the lectin complement pathway. A wide variety of clinical isolates of bacteria, fungi, viruses, and parasites are bound by MBL. Three polymorphisms in the structural gene MBL2) and 2 promoter gene polymorphisms are commonly found that result in production of low serum levels of MBL. Clinical studies have shown that MBL insufficiency is associated with bacterial infection in patients with neutropenia and meningococcal sepsis. Low MBL levels appear to predispose persons to HIV infection. Numerous other potential infectious disease associations have been described. Therapy to supplement low MBL levels is being explored using either plasma-derived or recombinant material.

Mannose-binding lectin in HIV infection: relation to disease progression and highly active antiretroviral therapy

To gain insight into the possible role of mannose-binding lectin (MBL) in HIV infection, we analyzed serum levels and the functional complement activation capacity of MBL in different clinical stages of HIV infection during cross-sectional analysis (n = 62) and longitudinal testing (n = 23) as well as during highly active antiretroviral therapy (HAART) (n = 40). The results were correlated with serum levels of C-reactive protein (CRP). Our main findings were as follows. MBL levels and the capacity of complement activation by the MBL pathway were increased in HIV-infected patients with advanced clinical disease as shown in both cross-sectional analysis and longitudinal testing. There was no "normalization" of these parameters during HAART. In fact, MBL levels increased during therapy, and this increase was associated with a good virologic response. Although both MBL and CRP are regarded as acute-phase proteins, no correlation was seen between these proteins. Thus, the notably diverse patterns of MBL responses among patients with different clinical courses and treatments suggest that MBL and complement activation by the MBL pathway could be involved in the pathophysiology of HIV infection. It is not inconceivable that the net effects of MBL responses may vary in different clinical settings.

Absence of association between mannose-binding lectin gene polymorphisms and HIV-1 infection in a Colombian population

Mannose-binding lectin (MBL) is a calcium-dependent lectin shown to play an important role in innate immunity to infection by activating the classical complement pathway and phagocytosis. In vitro studies have shown that MBL is able to bind to the gp120 HIV-1 surface antigen, and variants of the gene are associated with increased risk of HIV infection among Scandinavians. We investigated the association of genetic MBL variants and HIV-1 infection in 278 Colombian HIV-infected and control individuals. MBL genotype frequencies were similar for both groups, and no association was detected between MBL alleles B, C, and D and susceptibility to HIV-1 infection ( P=1.0). Since there is a well-documented link between the tested MBL alleles and very low MBL serum concentration, these results do not support the hypothesis that MBL levels are a risk factor for HIV-1 infection in Colombia.

The genomics and genetics of human infectious disease susceptibility

A genetic basis for interindividual variation in susceptibility to human infectious diseases has been indicated by twin, adoptee, pedigree, and candidate gene studies. This has led to the identification of a small number of strong genetic associations with common variants for malaria, HIV infection, and infectious prion diseases. Numerous other genes have shown less strong associations with these and some other infectious diseases, such as tuberculosis, leprosy, and persistent hepatitis viral infections. Many immunogenetic loci influence susceptibility to several infectious pathogens. Recent genetic linkage analyses of measures of infection as well as of infectious disease, including some genome-wide scans, have found convincing evidence of genetic linkage to chromosomal regions wherein susceptibility genes have yet to be identified. These studies indicate a highly polygenic basis for susceptibility to many common infectious diseases, with some emerging examples of interaction between variants of specific polymorphic host and pathogen genes.