John N. Nkengasong

Laboratory Diagnosis of Tuberculosis in Resource-Poor Countries: Challenges and Opportunities

SUMMARY With an estimated 9.4 million new cases globally, tuberculosis (TB) continues to be a major public health concern. Eighty percent of all cases worldwide occur in 22 high-burden, mainly resource-poor settings. This devastating impact of tuberculosis on vulnerable populations is also driven by its deadly synergy with HIV. Therefore, building capacity and enhancing universal access to rapid and accurate laboratory diagnostics are necessary to control TB and HIV-TB coinfections in resource-limited countries. The present review describes several new and established methods as well as the issues and challenges associated with implementing quality tuberculosis laboratory services in such countries. Recently, the WHO has endorsed some of these novel methods, and they have been made available at discounted prices for procurement by the public health sector of high-burden countries. In addition, international and national laboratory partners and donors are currently evaluating other new diagnostics that will allow further and more rapid testing in point-of-care settings. While some techniques are simple, others have complex requirements, and therefore, it is important to carefully determine how to link these new tests and incorporate them within a countrys national diagnostic algorithm. Finally, the successful implementation of these methods is dependent on key partnerships in the international laboratory community and ensuring that adequate quality assurance programs are inherent in each countrys laboratory network.

The puzzle of HIV-1 subtypes in Africa

HIV has a high degree of genetic variability. While much is known about the differences between HIV-1 and HIV-2 in terms of transmissibility pathogenesis and pattern of spread much remains to be learned about the biological characteristics and epidemic spread of the different HIV-1 strains. Before 1992 HIV-1 strains were classified on the basis of their geographic origin into North American and African variants. However since 1992 the env coding sequence has been used to classify globally prevalent viruses. Subtypes A through J have been classified according to differences between their env and gag coding sequences while 10 additional subtypes comprise the M group of HIV-1 viruses. The epidemics in all parts of sub-Saharan Africa except Southern Africa appear to be dominated by subtype A the largest variety of HIV-1 subtypes is found in Central Africa and subtype C plays an important role in the epidemics in Southern Africa. The authors review the distribution patterns of HIV-1 subtypes in sub-Saharan Africa and discuss the implications of such distribution for the development of diagnostic tests and vaccines as well as for surveillance.

Cutting edge : Resistance to HIV-1 infection among african female sex workers is associated with inhibitory KIR in the absence of their HLA ligands

NK cells are regulated in part by killer Ig-like receptors (KIR) that interact with HLA molecules on potential target cells. KIR and HLA loci are highly polymorphic and certain KIR/HLA combinations were found to protect against HIV disease progression. We show in this study that KIR/HLA interactions also influence resistance to HIV transmission. HIV-exposed but seronegative female sex workers in Abidjan, Côte d’Ivoire, frequently possessed inhibitory KIR genes in the absence of their cognate HLA genes: KIR2DL2/KIR2DL3 heterozygosity in the absence of HLA-C1 and KIR3DL1 homozygosity in the absence of HLA-Bw4. HIV-seropositive female sex workers were characterized by corresponding inhibitory KIR/HLA pairings: KIR2DL3 homozygosity together with HLA-C1 and a trend toward KIR3DL1/HLA-Bw4 homozygosity. Absence of ligands for inhibitory KIR could lower the threshold for NK cell activation. In addition, exposed seronegatives more frequently possessed AB KIR genotypes, which contain more activating KIR. The data support an important role for NK cells and KIR/HLA interactions in antiviral immunity.

Protease sequences from HIV-1 group M subtypes A-H reveal distinct amino acid mutation patterns associated with protease resistance in protease inhibitor-naive individuals worldwide.

BackgroundAlthough numerous mutations that confer resistance to protease inhibitors (PRI) have been mapped for HIV-1 subtype B, little is known about such substitutions for the non-B viruses, which globally cause the most infections. ObjectivesTo determine the prevalence of PRI-associated mutations in PRI-naive individuals worldwide. DesignUsing the polymerase chain reaction, protease sequences were amplified from 301 individuals infected with HIV-1subtypes A (79), B (95), B’ (19), C (12), D (26), A/E (23), F (26), A/G (11), and H (3) and unclassifiable HIV-1 (7). Amplified DNA was directly sequenced and translated to amino acids to analyze PRI-associated major and accessory mutations. ResultsOf the 301 sequences, 85% contained at least one codon change giving substitution at 10, 20, 30, 36, 46, 63, 71, 77, or 82 associated with PRI resistance; the frequency of these substitutions was higher among non-B (91%) than B (75%) viruses (P < 0.0005). Of these, 25% carried dual and triple substitutions. Two major drug resistance-conferring mutations, either 20M or 30N, were identified in only three specimens, whereas drug resistance accessory mutations were found in 252 isolates. These mutations gave distinct prevalence patterns for subtype B, 63P (62%) > 77I (19%) > 10I/V/R (6%) = 36I (6%) = 71T/V (6%) > 20R (2%), and non-B strains, 36I (83%) > 63P (17%) > 10I/V/R (13%) > 20R(10%) > 77I (2%), which differed statistically at positions 20, 36, 63, 71, and 77. ConclusionsThe high prevalence of PRI-associated substitutions represent natural polymorphisms occurring in PRI-naive patients infected with HIV-1 strains of subtypes A−H. The significance of distinct mutation patterns identified for subtype B and non-B strains warrants further clinical evaluation. A global HIV-1 protease database is fundamental for the investigation of novel PRI.

Breast-feeding and Transmission of HIV-1.

Breast-feeding substantially increases the risk of HIV-1 transmission from mother to child, and although peripartum antiretroviral therapy prophylaxis significantly decreases the risk of mother-to-child transmission around the time of delivery, this approach does not affect breast-feeding transmission. Increased maternal RNA viral load in plasma and breast milk is strongly associated with increased risk of transmission through breast-feeding, as is breast health, and it has been suggested that exclusive breast-feeding could be associated with lower rates of breast-feeding transmission than mixed feeding of both breast- and other milk or feeds. Transmission through breast-feeding can take place at any point during lactation, and the cumulative probability of acquisition of infection increases with duration of breast-feeding. HIV-1 has been detected in breast milk in cell-free and cellular compartments; infant gut mucosal surfaces are the most likely site at which transmission occurs. Innate and acquired immune factors may act most effectively in combination to prevent primary HIV-1 infection by breast milk.

Detection of Recent HIV-1 Infection Using a New Limiting-Antigen Avidity Assay: Potential for HIV-1 Incidence Estimates and Avidity Maturation Studies

Background Accurate and reliable laboratory methods are needed for estimation of HIV-1 incidence to identify the high-risk populations and target and monitor prevention efforts. We previously described a single-well limiting-antigen avidity enzyme immunoassay (LAg-Avidity EIA) to detect recent HIV-1 infection. Methods We describe here further optimization and characterization of LAg-Avidity EIA, comparing it to the BED assay and a two-well avidity-index (AI) EIA. Specimen sets included longitudinal sera (n = 393), collected from 89 seroconverting individuals from 4 cohorts representing 4 HIV-1 subtypes, and sera from AIDS patients (n = 488) with or without TB co-infections from 3 different cohorts. Ninety seven HIV-1 positive specimens were purchased commercially. The BED assay, LAg-Avidity EIA, AI-EIA and HIV serology were performed, as needed. Results Monitoring quality control specimens indicated high reproducibility of the LAg-Avidity EIA with coefficient of variation of <10% in the dynamic range. The LAg-Avidity EIA has an overall mean duration of recency (ω) of 141 days (95% CI 119–160) at normalized optical density (ODn) cutoff of 1.0, with similar ω in different HIV-1 subtypes and populations (132 to 143 days). Antibody avidity kinetics were similar among individuals and subtypes by both the LAg-Avidity EIA and AI-EIA compared to the HIV-IgG levels measured by the BED assay. The false recent rate among individuals with AIDS was 0.2% with the LAg-Avidity EIA, compared to 2.9% with the BED assay. Western blot profiles of specimens with increasing avidity confirm accurate detection of recent HIV-1 infections. Conclusions These data demonstrate that the LAg-Avidity EIA is a promising assay with consistent ω in different populations and subtypes. The assay should be very useful for 1) estimating HIV-1 incidence in cross-sectional specimens as part of HIV surveillance, 2) identifying risk factors for recent infections, 3) measuring impact of prevention programs, and 4) studying avidity maturation during vaccine trials.

The World Health Organization African region laboratory accreditation process: improving the quality of laboratory systems in the African region.

Few developing countries have established laboratory quality standards that are affordable and easy to implement and monitor. To address this challenge, the World Health Organization Regional Office for Africa (WHO AFRO) established a stepwise approach, using a 0- to 5-star scale, to the recognition of evolving fulfillment of the ISO 15189 standard rather than pass-fail grading. Laboratories that fail to achieve an assessment score of at least 55% will not be awarded a star ranking. Laboratories that achieve 95% or more will receive a 5-star rating. This stepwise approach acknowledges to laboratories where they stand, supports them with a series of evaluations to use to demonstrate improvement, and recognizes and rewards their progress. WHO AFROs accreditation process is not intended to replace established ISO 15189 accreditation schemes, but rather to provide an interim pathway to the realization of international laboratory standards. Laboratories that demonstrate outstanding performance in the WHO-AFRO process will be strongly encouraged to enroll in an established ISO 15189 accreditation scheme. We believe that the WHO-AFRO approach for laboratory accreditation is affordable, sustainable, effective, and scalable.

Cervicovaginal Secretory Antibodies to Human Immunodeficiency Virus Type 1 (HIV-1) that Block Viral Transcytosis through Tight Epithelial Barriers in Highly Exposed HIV-1–Seronegative African Women

Antibodies to human immunodeficiency virus (HIV) of the IgA, IgG, and IgM isotypes and high levels of the HIV suppressive beta-chemokine RANTES (regulated on activation, normally T cell expressed and secreted) were found in the cervicovaginal secretions (CVSs) of 7.5% of 342 multiply and repeatedly exposed African HIV-seronegative female sex workers. The antibodies are part of a local compartmentalized secretory immune response to HIV, since they are present in vaginal fluids that are free of contaminating semen. Cervicovaginal antibodies showed a reproducible pattern of reactivity restricted to gp160 and p24. Locally produced anti-env antibodies exhibit reactivity toward the neutralizing ELDKWA epitope of gp41. Study results show that antibodies purified from CVSs block the transcytosis of cell-associated HIV through a tight epithelial monolayer in vitro. These findings suggest that genital resistance to HIV may involve HIV-specific cervicovaginal antibody responses in a minority of highly exposed HIV-seronegative women in association with other protecting factors, such as local production of HIV-suppressive chemokines.

Laboratory Systems and Services Are Critical in Global Health: Time to End the Neglect?

Abstract The

Strengthening public health surveillance and response using the health systems strengthening agenda in developing countries.

63 billion comprehensive global health initiative (GHI) emphasizes health systems strengthening (HSS) to tackle challenges, including child and maternal health, HIV/AIDS, family planning, and neglected tropical diseases. GHI and other initiatives are critical to fighting emerging and reemerging diseases in resource-poor countries. HSS is also an increasing focus of the