Association of HLA alleles with Plasmodium falciparum severity in Malian children.

Pre-erythrocytic immunity to Plasmodium falciparum malaria is likely to be mediated by T-cell recognition of malaria epitopes presented on infected host cells via class I and II major histocompatibility complex (MHC) antigens. To test for associations of human leukocyte antigen (HLA) alleles with disease severity, we performed high-resolution typing of HLA class I and II loci and compared the distributions of alleles of HLA-A, -B, -C and -DRB1 loci in 359 Malian children of Dogon ethnicity with uncomplicated or severe malaria. We observed that alleles A*30:01 and A*33:01 had higher frequency in the group of patients with cerebral disease compared to patients with uncomplicated disease [A*30:01: gf = 0.2031 vs gf = 0.1064, odds ratio (OR) = 3.17, P = 0.004, confidence interval (CI) (1.94-5.19)] and [A*33:01: gf = 0.0781 vs gf = 0.0266, 4.21, P = 0.005, CI (1.89-9.84)], respectively. The A*30:01 and A*33:01 alleles share some sequence motifs and A*30:01 appears to have a unique peptide binding repertoire compared to other A*30 group alleles. Computer algorithms predicted malaria peptides with strong binding affinity for HLA-A*30:01 and HLA-A*33:01 but not to closely related alleles. In conclusion, we identified A*30:01 and A*33:01 as potential susceptibility factors for cerebral malaria, providing further evidence that polymorphism of MHC genes results in altered malaria susceptibility.

Ventriculitis complicating use of intraventricular catheters in adult neurosurgical patients.

Ventriculitis is a serious complication of intraventricular catheter (IVC) use, with rates of IVC-related infections ranging from 0% to 45% and gram-positive organisms predominating. We prospectively analyzed ventriculostomy-related infections occurring among 157 adult neurosurgical patients (mean age, 54.9 years; 90 [57%] were women) from 1995 through 1998, to determine the incidence of, risk factors for, and organisms that cause ventriculitis. A total of 196 IVC events resulted in 11 infections (5.6%; 9 were caused by gram-negative organisms and 2 by coagulase-negative staphylococci). Independent risk factors for IVC-related infection include length of IVC placement (8.5 days [infected] vs. 5.1 days [uninfected]; P=.007) and cerebrospinal fluid leakage about the IVC (P=.003). The length of hospital stay (30.8 days vs. 22.6 days; P=.03) and mean total hospital charges ($85,674.27 vs. $55,339.21; P=.009) were greater for infected patients than for uninfected patients. In addition, a microbiologic shift from gram-positive organisms toward gram-negative organisms was noted. This study suggests that IVC-related infections remain serious infections that increase the length of hospitalization.

Live attenuated malaria vaccine designed to protect through hepatic CD8⁺ T cell immunity.

Our goal is to develop a vaccine that sustainably prevents Plasmodium falciparum (Pf) malaria in ≥80% of recipients. Pf sporozoites (PfSPZ) administered by mosquito bites are the only immunogens shown to induce such protection in humans. Such protection is thought to be mediated by CD8(+) T cells in the liver that secrete interferon-γ (IFN-γ). We report that purified irradiated PfSPZ administered to 80 volunteers by needle inoculation in the skin was safe, but suboptimally immunogenic and protective. Animal studies demonstrated that intravenous immunization was critical for inducing a high frequency of PfSPZ-specific CD8(+), IFN-γ-producing T cells in the liver (nonhuman primates, mice) and conferring protection (mice). Our results suggest that intravenous administration of this vaccine will lead to the prevention of infection with Pf malaria.

A case of cutaneous ulcerative alternariosis: rare association with diabetes mellitus and unusual failure of itraconazole treatment.

Alternaria species are ubiquitous dematiaceous fungi that are increasingly recognized as pathogens in immunocompromised patients or those with significant underlying disease, but they are also pathogens in otherwise healthy hosts. We describe a case of dermal cutaneous ulcerative alternariosis in a frail 83-year-old patient with diet-controlled diabetes mellitus. Histological analysis revealed hyphal morphology in tissue sections that was initially confused with that of a zygomycetous fungus, and multiple positive culture results were necessary to identify the organism. Treatment with oral itraconazole and surgical debridement were ineffective; clinical improvement was achieved by means of treatment with intravenous amphotericin B lipid complex. We review the literature regarding the role of diabetes mellitus in cutaneous alternariosis and regarding the efficacy of treatment with itraconazole, which has been used very successfully. To our knowledge, this is only the second case report noting diabetes mellitus uncomplicated by steroid administration as a possible predisposing factor for cutaneous infection.

Identification of the Kna/Knb polymorphism and a method for Knops genotyping.

BACKGROUND: DNA mutations resulting in the McCoy and Swain-Langley polymorphisms have been identified on complement receptor 1 (CR1)-a ligand for rosetting of Plasmodium falciparum-infected RBCs. The molecular identification of the Kna/Knb polymorphism was sought to develop a genotyping method for use in the study of the Knops blood group and malaria. STUDY DESIGN AND METHODS: CR1 deletion constructs were used in inhibition studies of anti-Kna. PCR amplification of Exon 29 was followed by DNA sequencing. A PCR-RFLP was developed with NdeI, BsmI, and MfeI for the detection of Kna/Knb, McCa/McCb, and Sl1/Sl2, respectively. Knops phenotypes were determined with standard serologic techniques. RESULTS: A total of 310 Malian persons were phenotyped for Kna with 200 (64%) Kn(a+) and 110 (36%) Kn(a-). Many of the Kn(a-) exhibited the Knops-null phenotype, that is, Helgeson. The Kna/b DNA polymorphism was identified as a V1561M mutation with allele frequencies of Kna (V1561) 0.9 and Knb (M1561) 0.1. CONCLUSION: The high frequency (18%) of Knb in West African persons suggests that it is not solely a Caucasian trait. Furthermore, because of the high incidence of heterozygosity as well as amorphs, accurate Knops typing of donors of African descent is best accomplished by a combination of molecular and serologic techniques.

Serum levels of the proinflammatory cytokines interleukin-1 beta (IL-1beta), IL-6, IL-8, IL-10, tumor necrosis factor alpha, and IL-12(p70) in Malian children with severe Plasmodium falciparum malaria and matched uncomplicated malaria or healthy controls.

Inflammatory cytokines play an important role in human immune responses to malarial disease. However, the role of these mediators in disease pathogenesis, and the relationship between host protection and injury remains unclear. A total of 248 cases of severe Plasmodium falciparum malaria among children aged 3 months to 14 years residing in Bandiagara, Mali, were matched to cases of uncomplicated malaria and healthy controls. Using modified World Health Organization criteria for defining severe malaria, we identified 100 cases of cerebral malaria (coma, seizure, and obtundation), 17 cases of severe anemia (hemoglobin, <5 g/dl), 18 cases combined cerebral malaria with severe anemia, and 92 cases with hyperparasitemia (asexual trophozoites, >500,000/mm3). Significantly elevated levels (given as geometric mean concentrations in picograms/milliliter) of interleukin-6 (IL-6; 485.2 versus 54.1; P = <0.001), IL-10 (1,099.3 versus 14.1; P = <0.001), tumor necrosis factor alpha (10.1 versus 7.7; P = <0.001), and IL-12(p70) (48.9 versus 31.3; P = 0.004) in serum were found in severe cases versus healthy controls. Significantly elevated levels of IL-6 (485.2 versus 141.0; P = <0.001) and IL-10 (1,099.3 versus 133.9; P = <0.001) were seen in severe malaria cases versus uncomplicated malaria controls. Cerebral malaria was associated with significantly elevated levels of IL-6 (754.5 versus 311.4; P = <0.001) and IL-10 (1,405.6 versus 868.6; P = 0.006) compared to severe malaria cases without cerebral manifestations. Conversely, lower levels of IL-6 (199.2 versus 487.6; P = 0.03) and IL-10 (391.1 versus 1,160.9; P = 0.002) were noted in children with severe anemia compared to severe malaria cases with hemoglobin at >5 g/dl. Hyperparasitemia was associated with significantly lower levels of IL-6 (336.6 versus 602.1; P = 0.002). These results illustrate the complex relationships between inflammatory cytokines and disease in P. falciparum malaria.

Erythrocyte CR1 expression level does not correlate with a HindIII restriction fragment length polymorphism in Africans; implications for studies on malaria susceptibility.

Complement receptor 1 (CR1) expression level on erythrocytes is genetically determined, and in Caucasian populations is linked to high (H) and low (L) expression alleles identified by a HindIII restriction fragment length polymorphism (RFLP). Erythrocyte CR1 may be an important factor in determining malaria susceptibility, as low expression of CR1 reduces the rosetting of uninfected erythrocytes with Plasmodium falciparum-infected cells, a process that contributes to malaria pathogenesis. Prior to studying CR1 expression and malaria susceptibility, we have investigated whether the quantity of erythrocyte CR1 correlates with the H and L alleles in an African population. Mean erythrocyte CR1 in 149 Malian adults was 415 molecules per cell, which is comparable to Caucasian populations; however, there was no relationship between erythrocyte CR1 level and genotype for the HindIII RFLP (mean CR1 per erythrocyte HH = 414, HL = 419 and LL = 403, P > 0.1, Student's t-test). The conclusions of a previous study of erythrocyte CR1 expression level and malaria susceptibility in West Africa that was based on HindIII RFLP genotyping may therefore need to be re-evaluated.

Differentiation between African populations is evidenced by the diversity of alleles and haplotypes of HLA class I loci.

The allelic and haplotypic diversity of the HLA-A, HLA-B, and HLA-C loci was investigated in 852 subjects from five sub-Saharan populations from Kenya (Nandi and Luo), Mali (Dogon), Uganda, and Zambia. Distributions of genotypes at all loci and in all populations fit Hardy-Weinberg equilibrium expectations. There was not a single allele predominant at any of the loci in these populations, with the exception of A*3002 [allele frequency (AF) = 0.233] in Zambians and Cw*1601 (AF = 0.283) in Malians. This distribution was consistent with balancing selection for all class I loci in all populations, which was evidenced by the homozygosity F statistic that was less than that expected under neutrality. Only in the A locus in Zambians and the C locus in Malians, the AF distribution was very close to neutrality expectations. There were six instances in which there were significant deviations of allele distributions from neutrality in the direction of balancing selection. All allelic lineages from each of the class I loci were found in all the African populations. Several alleles of these loci have intermediate frequencies (AF = 0.020-0.150) and seem to appear only in the African populations. Most of these alleles are widely distributed in the African continent and their origin may predate the separation of linguistic groups. In contrast to native American and other populations, the African populations do not seem to show extensive allelic diversification within lineages, with the exception of the groups of alleles A*02, A*30, B*57, and B*58. The alleles of human leukocyte antigen (HLA)-B are in strong linkage disequilibrium (LD) with alleles of the C locus, and the sets of B/C haplotypes are found in several populations. The associations between A alleles with C-blocks are weaker, and only a few A/B/C haplotypes (A*0201-B*4501-Cw*1601; A*2301-B*1503-Cw*0202; A*7401-B* 1503-Cw*0202; A*2902-B*4201-Cw*1701; A*3001-B*4201-Cw*1701; and A*3601-B*5301-Cw*0401) are found in multiple populations with intermediate frequencies [haplotype frequency (HF) = 0.010-0.100]. The strength of the LD associations between alleles of HLA-A and HLA-B loci and those of HLA-B and HLA-C loci was on average of the same or higher magnitude as those observed in other non-African populations for the same pairs of loci. Comparison of the genetic distances measured by the distribution of alleles at the HLA class I loci in the sub-Saharan populations included in this and other studies indicate that the Luo population from western Kenya has the closest distance with virtually all sub-Saharan population so far studied for HLA-A, a finding consistent with the putative origin of modern humans in East Africa. In all African populations, the genetic distances between each other are greater than those observed between European populations. The remarkable current allelic and haplotypic diversity in the HLA system as well as their variable distribution in different sub-Saharan populations is probably the result of evolutionary forces and environments that have acted on each individual population or in their ancestors. In this regard, the genetic diversity of the HLA system in African populations poses practical challenges for the design of T-cell vaccines and for the transplantation medical community to find HLA-matched unrelated donors for patients in need of an allogeneic transplant.