Harr Freeya Njai

The predominance of Human Immunodeficiency Virus type 1 (HIV-1) circulating recombinant form 02 (CRF02_AG) in West Central Africa may be related to its replicative fitness

BackgroundCRF02_AG is the predominant HIV strain circulating in West and West Central Africa. The aim of this study was to test whether this predominance is associated with a higher in vitro replicative fitness relative to parental subtype A and G viruses. Primary HIV-1 isolates (10 CRF02_AG, 5 subtype A and 5 subtype G) were obtained from a well-described Cameroonian cohort. Growth competition experiments were carried out at equal multiplicity of infection in activated T cells and monocyte-derived dendritic cells (MO-DC) in parallel.ResultsDual infection/competition experiments in activated T cells clearly indicated that CRF02_AG isolates had a significant replication advantage over the subtype A and subtype G viruses. The higher fitness of CRF02_AG was evident for isolates from patients with CD4+ T cell counts >200 cells/μL (non-AIDS) or CD4+ T cell counts <200 cells/μL (AIDS), and was independent of the co-receptor tropism. In MO-DC cultures, CRF02_AG isolates showed a slightly but not significantly higher replication advantage compared to subtype A or G isolates.ConclusionWe observed a higher ex vivo replicative fitness of CRF02_AG isolates compared to subtype A and G viruses from the same geographic region and showed that this was independent of the co-receptor tropism and irrespective of high or low CD4+ T cell count. This advantage in replicative fitness may contribute to the dominant spread of CRF02_AG over A and G subtypes in West and West Central Africa.

Cytotoxic T lymphocytes recognize structurally diverse, clade‐specific and cross‐reactive peptides in human immunodeficiency virus type‐1 gag through HLA‐B53

Human immunodeficiency virus type‐1 (HIV‐1) cytotoxic T lymphocyte (CTL) epitopes have largely been defined in Caucasian populations infected with clade B virus. Identification of potentially protective CTL epitopes in non‐B clade‐infected African subjects is important for vaccine development. In a study of CTL responses in clade A‐infected Gambians, using cytotoxicity, interferon‐γ (IFN‐γ) enzyme‐linked immunospot (ELISpot) and HLA‐B53‐peptide tetramer assays, we identified three HLA‐B53‐restricted epitopes in HIV‐1 gag p24. CTL specific for an epitope in a highly immunogenic region of the p24 protein showed no cross‐reactivity to other HIV‐1 clades. Two of the epitopes would not have been predicted from the peptide‐binding motif due to the absence of a proline anchor at position 2. Structural analysis of HLA‐B53 and its relative, HLA B35, enabled us to re‐define the peptide‐binding motif to include other P2 anchors. These results demonstrate the value of combined immunological and structural analyses in defining novel CTL epitopes and have implications for HIV‐1 vaccine design.

Natural history of chronic HBV infection in West Africa: a longitudinal population-based study from The Gambia

Background The natural history of chronic HBV infection in sub-Saharan Africa is unknown. Data are required to inform WHO guidelines that are currently based on studies in Europe and Asia. Methods Between 1974 and 2008, serosurveys were repeated in two Gambian villages, and an open cohort of treatment-naive chronic HBV carriers was recruited. Participants were followed to estimate the rates of hepatitis B e (HBeAg) and surface antigen (HBsAg) clearance and incidence of hepatocellular carcinoma (HCC). In 2012–2013, a comprehensive liver assessment was conducted to estimate the prevalence of severe liver disease. Results 405 chronic carriers (95% genotype E), recruited at a median age of 10.8 years, were followed for a median length of 28.4 years. Annually, 7.4% (95% CI 6.3% to 8.8%) cleared HBeAg and 1.0% (0.8% to 1.2%) cleared HBsAg. The incidence of HCC was 55.5/100 000 carrier-years (95% CI 24.9 to 123.5). In the 2012–2013 survey (n=301), 5.5% (95% CI 3.4% to 9.0%) had significant liver fibrosis. HBV genotype A (versus E), chronic aflatoxin B1 exposure and an HBsAg-positive mother, a proxy for mother-to-infant transmission, were risk factors for liver fibrosis. A small proportion (16.0%) of chronic carriers were infected via mother-to-infant transmission; however, this population represented a large proportion (63.0%) of the cases requiring antiviral therapy. Conclusions The incidence of HCC among chronic HBV carriers in West Africa was higher than that in Europe but lower than rates in East Asia. High risk of severe liver disease among the few who are infected by their mothers underlines the importance of interrupting perinatal transmission in sub-Saharan Africa.

Validation of Rapid Point-of-Care (POC) Tests for Detection of Hepatitis B Surface Antigen in Field and Laboratory Settings in the Gambia, Western Africa

ABSTRACT Hepatitis B virus (HBV) infection is a leading cause of death in sub-Saharan Africa (SSA). Point-of-care tests for hepatitis B surface antigen (HBsAg) could be an ideal tool for a large-scale HBV screening/treatment program in SSA. Using data from the PROLIFICA (Prevention of Liver Fibrosis and Cancer in Africa) program, we conducted a cross-sectional study to assess the diagnostic accuracy of three point-of-care tests (Determine, Vikia, and Espline) for the detection of HBsAg in the field or a laboratory setting in the Gambia. In the field, we used finger-prick whole blood for the Determine and Vikia tests and dried blood spots for the reference standard test (AxSYM HBsAg enzyme-linked immunosorbent assay [ELISA]). In the laboratory we used serum for the Determine, Espline, and reference test (Architect chemiluminescent microparticle immunoassay). Of 773 participants recruited at the community and 227 known chronic HBV carriers (1,000 subjects in total), 293 were positive for HBsAg. The sensitivity and specificity of the Determine test were 88.5% and 100% in the field and 95.3% and 93.3% in the laboratory setting, respectively. The sensitivity and specificity were 90.0% and 99.8% for the Vikia test (in the field) and 93.9% and 94.7% for the Espline test (in the laboratory). There was no evidence that one kit was better than another. Most of the patients with false-negative results (18/19) were classified as inactive chronic carriers. In summary, the three point-of-care tests had acceptable ranges of diagnostic accuracy. These tests may represent accurate, rapid, and inexpensive alternatives to serology testing for the screening of HBV infection at field level in SSA.

Acceptability and feasibility of a screen-and-treat programme for hepatitis B virus infection in The Gambia: the Prevention of Liver Fibrosis and Cancer in Africa (PROLIFICA) study

BACKGROUND Despite the introduction of immunisation for hepatitis B virus (HBV) in the 1990s, HBV-related morbidity and mortality remain high in sub-Saharan Africa. Identification and treatment of asymptomatic people with chronic HBV infection should reduce the disease burden. We therefore assessed the feasibility of a screen-and-treat programme for HBV infection in The Gambia, west Africa, and estimated the proportion of HBV-infected people who had significant liver disease in need of treatment. METHODS Between Dec 7, 2011, and Jan 24, 2014, individuals living in randomly selected communities in western Gambia were offered hepatitis B surface antigen (HBsAg) screening via a point-of-care test. The test was also offered to potential blood donors attending the central hospital in the capital, Banjul. HBsAg-positive individuals were invited for a comprehensive liver assessment and were offered treatment according to international guidelines. We defined linkage to care as visiting the liver clinic at least once. Eligibility for treatment was judged in accordance with the 2012 European Association for the Study of the Liver guidelines. FINDINGS HBsAg screening was accepted by 5980 (weighted estimate 68·9%, 95% CI 65·0-72·4) of 8170 adults from 27 rural and 27 urban communities and 5559 (81·4%, 80·4-82·3) of 6832 blood donors. HBsAg was detected in 495 (8·8%, 7·9-9·7) individuals in communities and 721 (13·0%, 12·1-13·9) blood donors. Prevalence was higher in men (239 [10·5%, 8·9-12·1] of 2328 men vs 256 [7·6%, 6·5-8·7] of 3652 women; p=0·004) and middle-aged participants. Linkage to care was high in the communities, with 402 (81·3%) of 495 HBsAg-positive individuals attending the clinic. However, only 300 (41·6%) of 721 HBsAg-positive people screened at the blood bank linked into care. Of those who attended the clinic, 18 (4·4%, 2·5-7·7) patients from the communities and 29 (9·7%, 6·8-13·6) from the blood bank were eligible for treatment. Male sex was strongly associated with treatment eligibility (odds ratio 4·35, 1·50-12·58; p=0·007). INTERPRETATION HBV infection remains highly prevalent in The Gambia. The high coverage of community-based screening, good linkage into care, and the small proportion of HBsAg carriers who need treatment suggest that large-scale screening and treatment programmes are feasible in sub-Saharan Africa. FUNDING European Commission (FP7).

Discovery and validation of urinary metabotypes for the diagnosis of hepatocellular carcinoma in West Africans

There is no clinically applicable biomarker for surveillance of hepatocellular carcinoma (HCC), because the sensitivity of serum alpha‐fetoprotein (AFP) is too low for this purpose. Here, we determined the diagnostic performance of a panel of urinary metabolites of HCC patients from West Africa. Urine samples were collected from Nigerian and Gambian patients recruited on the case‐control platform of the Prevention of Liver Fibrosis and Cancer in Africa (PROLIFICA) program. Urinary proton nuclear magnetic resonance (1H‐NMR) spectroscopy was used to metabolically phenotype 290 subjects: 63 with HCC; 32 with cirrhosis (Cir); 107 with noncirrhotic liver disease (DC); and 88 normal control (NC) healthy volunteers. Urine samples from a further cohort of 463 subjects (141 HCC, 56 Cir, 178 DC, and 88 NC) were analyzed, the results of which validated the initial cohort. The urinary metabotype of patients with HCC was distinct from those with Cir, DC, and NC with areas under the receiver operating characteristic (AUROC) curves of 0.86 (0.78‐0.94), 0.93 (0.89‐0.97), and 0.89 (0.80‐0.98) in the training set and 0.81 (0.73‐0.89), 0.96 (0.94‐0.99), and 0.90 (0.85‐0.96), respectively, in the validation cohort. A urinary metabolite panel, comprising inosine, indole‐3‐acetate, galactose, and an N‐acetylated amino acid (NAA), showed a high sensitivity (86.9% [75.8‐94.2]) and specificity (90.3% [74.2‐98.0]) in the discrimination of HCC from cirrhosis, a finding that was corroborated in a validation cohort (AUROC: urinary panel = 0.72; AFP = 0.58). Metabolites that were significantly increased in urine of HCC patients, and which correlated with clinical stage of HCC, were NAA, dimethylglycine, 1‐methylnicotinamide, methionine, acetylcarnitine, 2‐oxoglutarate, choline, and creatine. Conclusion: The urinary metabotyping of this West African cohort identified and validated a metabolite panel that diagnostically outperforms serum AFP. (Hepatology 2014;60:1291–1301)

Food intake increases liver stiffness measurements and hampers reliable values in patients with chronic hepatitis B and healthy controls: the PROLIFICA experience in The Gambia

By increasing the hepatic blood circulation, food intake has been suggested to increase liver stiffness measurement (LSM) values in HCV‐infected patients.

CD8+ T cell responses to human immunodeficiency viruses type 2 (HIV-2) and type 1 (HIV-1) gag proteins are distinguishable by magnitude and breadth but not cellular phenotype.

The mechanisms underlying the relatively slow progression of human immunodeficiency virus type 2 (HIV‐2) compared with HIV‐1 infection are undefined and could be a result of more effective immune responses. We used HIV‐2 and HIV‐1 IFN‐γ enzyme‐linked immunospot assays to evaluate CD8+ T cell responses in antiretroviral‐naive HIV‐2‐ (‘HIV‐2+’) and HIV‐1‐infected (‘HIV‐1+’) individuals. Gag‐specific responses were detected in the majority of HIV‐2+ and HIV‐1+ subjects. Overlapping gag peptide analysis indicated a significantly greater magnitude and breadth of responses in the HIV‐1+ cohort, and this difference was attributable to low responses in HIV‐2+ subjects with undetectable viral load (medians 2107 and 512 spot‐forming units per 106 PBMC, respectively, p=0.007). We investigated the phenotype of viral epitope‐specific CD8+ T cells identified with HLA‐B53‐ and HLA‐B58‐peptide tetramers (8 HIV‐2+, 11 HIV‐1+ subjects). HIV‐2‐specific CD8+ T cells were predominantly CD27+ CD45RA–, and only a minority expressed perforin. The limited breadth and low frequency of CD8+ T cell responses to HIV‐2 gag in aviremic HIV‐2+ subjects suggests that these responses reflect antigen load in plasma, as is the case in HIV‐1 infection. Immune control of HIV‐2 does not appear to be related to the frequency of perforin‐expressing virus‐specific CD8+ T cells.

Cost-effectiveness of community-based screening and treatment for chronic hepatitis B in The Gambia: an economic modelling analysis

BACKGROUND Despite the high burden of hepatitis B virus (HBV) infection in sub-Saharan Africa, absence of widespread screening and poor access to treatment leads to most people remaining undiagnosed until later stages of disease when prognosis is poor and treatment options are limited. We examined the cost-effectiveness of community-based screening and early treatment with antiviral therapy for HBV in The Gambia. METHODS In this economic evaluation, we combined a decision tree with a Markov state transition model to compare a screen and treat intervention consisting of adult community-based screening using a hepatitis B surface antigen (HBsAg) rapid test and subsequent HBV antiviral therapy versus current practice, in which there is an absence of publicly provided screening or treatment for HBV. We used data from the PROLIFICA study to parameterise epidemiological, primary screening, and cost information, and other model parameter inputs were obtained from a literature search. Outcome measures were cost per disability-adjusted life-year (DALY) averted; cost per life-year saved; and cost per quality-adjusted life-year (QALY) gained. We calculated the incremental cost-effectiveness ratios (ICERs) between current practice and the screen and treat intervention. Costs were assessed from a health provider perspective. Costs (expressed in 2013 US

Birth order and risk of hepatocellular carcinoma in chronic carriers of hepatitis B virus: a case-control study in The Gambia.

) and health outcomes were discounted at 3% per year. FINDINGS In The Gambia, where the prevalence of HBsAg is 8·8% in people older than 30 years, adult screening and treatment for HBV has an incremental cost-effectiveness ratio (ICER) of