Effect of early two-dose measles vaccination on childhood mortality and modification by maternal measles antibody in Guinea-Bissau, West Africa: A single-centre open-label randomised controlled trial

BACKGROUND

Early 2-dose measles vaccine (MV) at 4 and 9 months of age vs. the WHO strategy of MV at 9 months of age reduced all-cause child mortality in a previous trial. We aimed to test two hypotheses: 1) a 2-dose strategy reduces child mortality between 4 and 60 months of age by 30%; 2) receiving early MV at 4 months in the presence versus absence of maternal measles antibodies (MatAb) reduces child mortality by 35%.

METHODS

Single-centre open-label community-based randomised controlled trial in Guinea-Bissau, with 2:1 block-randomisation by sex to a 2-dose (4 + 9 months) vs. 1-dose (9 months) MV strategy. Healthy children were eligible 4 weeks after the 3rd diphtheria-tetanus-pertussis-containing vaccine. Before randomisation a blood sample was collected to determine MatAb level. The primary outcome was all-cause mortality. Hazard ratios (HR) were derived from Cox regression in the per protocol population. We tested for interactions with national campaigns with oral polio vaccine (C-OPV). Trial registration: NCT01486355.

FINDINGS

Between August 2011-April 17th 2015, 6,636 children were enroled, 6,598[n_2-dose=4,397; n_1-dose=2,201] were included in the analysis of the primary outcome, The HR(2-dose/1-dose) between 4 and 60 months was 1.38 (95%CI: 0.92-2.06) [deaths: n_2-dose=90; n_1-dose=33]. Before the 9-month MV and the HR(1-dose/no dose) was 0.94 (0.45-1.96) [deaths: n_2-dose=21; n_1-dose=11]. The HR(2-dose/1-dose) was 0.81 (0.29-2.22) for children, who received no C-OPV [deaths/children: n_2-dose=10/2,801; n_1-dose=6/1,365], and 4.73 (1.44-15.6) for children, who received C-OPV before and after enrolment (p for interaction=0.027) [deaths/children: n_2-dose=27/1,602; n_1-dose=3/837]. In the 2-dose group receiving early MV at 4 months, mortality was 50% (20-68%) lower for those vaccinated in the presence of MatAb vs. the absence of MatAb [deaths/children: n_MatAb=51/3,132; n_noMatAb=31/1,028].

INTERPRETATION

The main result contrasts with previous findings but may, though based on a small number of events, be explained by frequent OPV campaigns that reduced the mortality rate, but apparently interacted negatively with early MV. The beneficial non-specific effects of MV in the presence of MatAb should be investigated further.

FUNDING

ERC, Danish National Research Foundation, the Danish Council for Development Research, Ministry of Foreign Affairs, Novo Nordisk Foundation, European Union and the Lundbeck Foundation.

Limited Impact of Human Cytomegalovirus Infection in African Infants on Vaccine-Specific Responses Following Diphtheria-Tetanus-Pertussis and Measles Vaccination

Human cytomegalovirus (HCMV) infection has a profound effect on the human immune system, causing massive clonal expansion of CD8, and to a lesser extend CD4 T cells. The few human trials that have explored the effect of HCMV infection on responses to vaccination are conflicting, with some studies suggesting no effect whilst others suggest decreased or increased immune responses. Recent studies indicate substantial differences in overall immune system reactivity to vaccines based on age and sex, particularly cellular immunity. 225 nine-month old Gambian infants were immunized with diphtheria-tetanus-whole cell pertussis and/or measles vaccines. HCMV infection status was determined by the presence of CMV DNA by PCR of urine samples prior to vaccination. The effect of HCMV infection on either protective antibody immunity or vaccine-specific and overall cellular immune responses 4 weeks post-vaccination was determined, further stratified by sex. Tetanus toxoid-specific antibody responses were significantly lower in HCMV+ infants compared to their HCMV- counterparts, while pertussis, diphtheria and measles antibody responses were generally comparable between the groups. Responses to general T cell stimulation with anti-CD3/anti-CD28 as well as antigen-specific cytokine responses to purified protein derivative (PPD) were broadly suppressed in infants infected with HCMV but, perhaps surprisingly, there was only a minimal impact on antigen-specific cellular responses to vaccine antigens. There was evidence for subtle sex differences in the effects of HCMV infection, in keeping with the emerging evidence suggesting sex differences in homeostatic immunity and in responses to vaccines. This study reassuringly suggests that the high rates of HCMV infection in low income settings have little clinically significant impact on antibody and cellular responses to early life vaccines, while confirming the importance of sex stratification in such studies.

Measles Vaccination in Presence of Measles Antibody May Enhance Child Survival

Background: In trials of early two-dose measles vaccination (MV), with the first dose being given before 9 months of age, vaccination in the presence of maternal antibody reduced mortality 2- to 3-fold compared with MV in the presence of no measles antibody. We tested this finding in two historical studies in which the children had received one dose of MV. Methods: We used data from a surveillance study of seroconversion after standard-titer MV (Schwarz strain) (Study 1) and a trial of early medium-titer MV (Edmonston-Zagreb strain) in which a pre-vaccination blood sample had been collected (Study 2). Both studies had control children, who were enrolled under similar conditions, but did not receive effective MV. Study 1 was a natural experiment where all children measles vaccinated during 1 month did not seroconvert and had therefore received an ineffective vaccine. In Study 2, the controls were randomized to an inactivated polio vaccine (IPV). We compared mortality for children with undetectable levels of measles antibody (<31.25 mIU) at baseline with children with detectable levels (≥31.25 mIU). Results: In both studies, children who were measles vaccinated in the presence of measles antibody had lower mortality compared with children who were measles vaccinated in presence of no measles antibody, the combined mortality rate ratio (MRR) being 0.51 (0.27-0.96). In the control groups, a detectable level of measles antibody vs. an undetectable level was not associated with lower mortality, the MRR being 1.40 (0.31-6.38). Conclusion: The results supported previous findings: measles vaccination in the presence of measles antibody had beneficial effects on child survival. Since maternal antibody levels are declining, it may be time to consider giving MV earlier and/or to provide MV to adolescent girls to boost antibody levels.

A Two-Center Randomized Trial of an Additional Early Dose of Measles Vaccine: Effects on Mortality and Measles Antibody Levels

Background

In addition to protecting against measles, measles vaccine (MV) may have beneficial nonspecific effects. We tested the effect of an additional early MV on mortality and measles antibody levels.

Methods

Children aged 4-7 months at rural health and demographic surveillance sites in Burkina Faso and Guinea-Bissau were randomized 1:1 to an extra early standard dose of MV (Edmonston-Zagreb strain) or no extra MV 4 weeks after the third diphtheria-tetanus-pertussis-hepatitis B-Haemophilus influenzae type b vaccine. All children received routine MV at 9 months. We assessed mortality through home visits and compared mortality from enrollment to age 3 years using Cox proportional hazards models, censoring for subsequent nontrial MV. Subgroups of participants had blood sampled to assess measles antibody levels.

Results

Among 8309 children enrolled from 18 July 2012 to 3 December 2015, we registered 145 deaths (mortality rate: 16/1000 person-years). The mortality was lower than anticipated and did not differ by randomization group (hazard ratio, 1.05; 95% confidence interval, 0.75-1.46). At enrollment, 4% (16/447) of children in Burkina Faso and 21% (90/422) in Guinea-Bissau had protective measles antibody levels. By age 9 months, no measles-unvaccinated/-unexposed child had protective levels, while 92% (306/333) of early MV recipients had protective levels. At final follow-up, 98% (186/189) in the early MV group and 97% (196/202) in the control group had protective levels.

Conclusions

Early MV did not reduce all-cause mortality. Most children were susceptible to measles infection at age 4-7 months and responded with high antibody levels to early MV.

Clinical Trials Registration

NCT01644721.

KIR content genotypes associate with carriage of hepatitis B surface antigen, e antigen and HBV viral load in Gambians

BACKGROUND

Hepatocellular carcinoma (HCC) causes over 800,000 deaths worldwide annually, mainly in low income countries, and incidence is rising rapidly in the developed world with the spread of hepatitis B (HBV) and C (HCV) viruses. Natural Killer (NK) cells protect against viral infections and tumours by killing abnormal cells recognised by Killer-cell Immunoglobulin-like Receptors (KIR). Thus genes and haplotypes encoding these receptors may be important in determining both outcome of initial hepatitis infection and subsequent chronic liver disease and tumour formation. HBV is highly prevalent in The Gambia and the commonest cause of liver disease. The Gambia Liver Cancer Study was a matched case-control study conducted between September 1997 and January 2001 where cases with liver disease were identified in three tertiary referral hospitals and matched with out-patient controls with no clinical evidence of liver disease.

METHODS

We typed 15 KIR genes using the polymerase chain reaction with sequence specific primers (PCR-SSP) in 279 adult Gambians, 136 with liver disease (HCC or Cirrhosis) and 143 matched controls. We investigated effects of KIR genotypes and haplotypes on HBV infection and associations with cirrhosis and HCC.

RESULTS

Homozygosity for KIR group A gene-content haplotype was associated with HBsAg carriage (OR 3.7, 95% CI 1.4-10.0) whilst telomeric A genotype (t-AA) was associated with reduced risk of e antigenaemia (OR 0.2, 95% CI 0.0-0.6) and lower viral loads (mean log viral load 5.2 vs. 6.9, pc = 0.022). One novel telomeric B genotype (t-ABx2) containing KIR3DS1 (which is rare in West Africa) was also linked to e antigenaemia (OR 8.8, 95% CI 1.3-60.5). There were no associations with cirrhosis or HCC.

CONCLUSION

Certain KIR profiles may promote clearance of hepatitis B surface antigen whilst others predispose to e antigen carriage and high viral load. Larger studies are necessary to quantify the effects of individual KIR genes, haplotypes and KIR/HLA combinations on long-term viral carriage and risk of liver cancer. KIR status could potentially inform antiviral therapy and identify those at increased risk of complications for enhanced surveillance.

Negative Correlation between Circulating CD4+FOXP3+CD127- Regulatory T Cells and Subsequent Antibody Responses to Infant Measles Vaccine but Not Diphtheria-Tetanus-Pertussis Vaccine Implies a Regulatory Role

Regulatory T cells (Tregs) play a key homeostatic role by suppressing immune responses. They have been targeted in mouse and human cancer studies to improve vaccine immunogenicity and tumor clearance. A number of commercially available drugs and experimental vaccine adjuvants have been shown to target Tregs. Infants have high numbers of Tregs and often have poor responses to vaccination, yet the role Tregs play in controlling vaccine immunogenicity has not been explored in this age group. Herein, we explore the role of CD4⁺FOXP3⁺CD127^- Tregs in controlling immunity in infant males and females to vaccination with diphtheria-tetanus-whole cell pertussis (DTP) and/or measles vaccine (MV). We find correlative evidence that circulating Tregs at the time of vaccination suppress antibody responses to MV but not DTP; and Tregs 4 weeks after DTP vaccination may suppress vaccine-specific cellular immunity. This opens the exciting possibility that Tregs may provide a future target for improved vaccine responses in early life, including reducing the number of doses of vaccine required. Such an approach would need to be safe and the benefits outweigh the risks, thus further research in this area is required.

Campaigns with oral polio vaccine may lower mortality and create unexpected results

Three studies from Guinea-Bissau found conflicting effects of OPV-at-birth (OPV0) on child survival. One study from 2004 suggested excess male mortality among children receiving OPV0 compared with children receiving NoOPV0 during a period of shortage of OPV. However, two subsequent studies showed beneficial effects of OPV0. In 2004, two national OPV-campaigns had been conducted in Guinea-Bissau. In a reanalysis of the 2004-study, in a survival analysis the age-adjusted mortality rate of study participants was 67% (95% CI=42-81%) lower after the OPV-campaigns than before the campaigns. In the OPV0 group only 22% (655/3031 person-years (pyrs)) of follow-up time was "after" the OPV-campaigns whereas 55% (473/859 pyrs) of the time in the NoOPV0 group was post-campaign (p<0.0001, Chi²). Censoring for OPV-campaigns in the original study removed excess male mortality and made the three studies more homogeneous. Overall, there is now considerable evidence that OPV, like other live vaccines, has important beneficial non-specific effects.

Does oral polio vaccine have non-specific effects on all-cause mortality? Natural experiments within a randomised controlled trial of early measles vaccine

BACKGROUND

BCG and measles vaccine (MV) may have beneficial non-specific effects (NSEs). If an unplanned intervention with a vaccine (a natural experiment) modifies the estimated effect in a randomised controlled trial (RCT), this suggests NSEs. We used this approach to test NSEs of triple oral polio vaccine (OPV).

METHODS

During an RCT of 2 doses of MV at 4.5 and 9 months versus 1 dose of MV at 9 months of age, we experienced 2 natural experiments with OPV. We assessed whether these OPV experiments modified the effect of 2-dose MV in the MV trial.

SETTING

MV RCT conducted in urban Guinea-Bissau 2003-2009.

INTERVENTIONS

Natural experiments with OPV due to missing vaccine and the implementation of OPV campaigns.

MAIN OUTCOME MEASURE

Changes in the mortality rate ratio (MRR) for 2-dose MV versus 1-dose MV.

RESULTS

First, the MRR (2-dose/1-dose MV) overall was 0.70 (0.52 to 0.94), but the MRR was 1.04 (0.53 to 2.04) when OPV at birth (OPV0) was not given, suggesting that early priming with OPV was important for the effect of 2-dose MV. The effect of OPV0 depended on age of administration; the MRR (2-dose/1-dose MV) was 0.45 (0.29 to 0.71) for children receiving OPV0 in the first week of life, but 3.63 (0.87 to 15.2) for those receiving OPV0 after the first month of life (p=0.007, test of no interaction). Second, campaign-OPV may have reduced the difference between the randomisation groups since the MRR (2-dose/1-dose MV) was 0.60 (0.42 to 0.85) for children who had not received campaign-OPV before RCT-enrolment versus 0.72 (0.23 to 2.31) and 1.42 (0.70 to 2.90) for children who had received 1 or 2 doses of campaign-OPV-before-enrolment, respectively.

CONCLUSIONS

Bissau had no polio infection during this trial, so OPV0 and campaign-OPV may have NSEs since they modified the effect of 2-dose MV in an RCT. Different interventions may interact to a much larger effect than usually assumed.

Revaccination with Live Attenuated Vaccines Confer Additional Beneficial Nonspecific Effects on Overall Survival: A Review

BACKGROUND

Live vaccines against measles (MV), tuberculosis (BCG), polio (OPV) and smallpox reduce mortality more than explained by target-disease prevention. The beneficial nonspecific effects (NSEs) of MV are strongest when MV is given in presence of maternal antibodies. We therefore hypothesised that revaccination in presence of prior immunity enhances beneficial NSEs.

METHODS

Literature search for studies of revaccination and mortality.

FINDINGS

In two randomised trials (RCTs), two doses versus one dose of MV reduced all-cause mortality by 63% (95% CI: 23-83%) from 9 to 18months of age. In a quasi-experimental study two doses before and after 9months compared with one dose of MV after 9months of age reduced mortality by 59% (25-81%). BCG-revaccination significantly enhanced BCG's effect against overall child mortality in two RCTs. In a natural experiment study of OPV campaigns over a 13-year-period in Guinea-Bissau, each additional dose of OPV was associated with a 13% (4-21%) reduction in mortality rate. The beneficial NSEs of smallpox vaccination for survival increased significantly with the number of smallpox vaccination scars.

INTERPRETATION

Revaccination with live vaccines led to substantial reductions in overall mortality. These findings challenge current understanding of vaccines and may explain the beneficial effects of campaigns with live vaccines.

The presence of prolines in the flanking region of an immunodominant HIV-2 gag epitope influences the quality and quantity of the epitope generated

Both the recognition of HIV‐infected cells and the immunogenicity of candidate CTL vaccines depend on the presentation of a peptide epitope at the cell surface, which in turn depends on intracellular antigen processing. Differential antigen processing maybe responsible for the differences in both the quality and the quantity of epitopes produced, influencing the immunodominance hierarchy of viral epitopes. Previously, we showed that the magnitude of the HIV‐2 gag‐specific T‐cell response is inversely correlated with plasma viral load, particularly when responses are directed against an epitope, ₁₆₅DRFYKSLRA₁₇₃, within the highly conserved Major Homology Region of gag‐p26. We also showed that the presence of three proline residues, at positions 119, 159 and 178 of gag‐p26, was significantly correlated with low viral load. Since this proline motif was also associated with stronger gag‐specific CTL responses, we investigated the impact of these prolines on proteasomal processing of the protective ₁₆₅DRFYKSLRA₁₇₃ epitope. Our data demonstrate that the ₁₆₅DRFYKSLRA₁₇₃ epitope is most efficiently processed from precursors that contain two flanking proline residues, found naturally in low viral‐load patients. Superior antigen processing and enhanced presentation may account for the link between infection with HIV‐2 encoding the “PPP‐gag” sequence and both strong gag‐specific CTL responses as well as lower viral load.

Early virological and immunological events in asymptomatic Epstein-Barr virus infection in African children

Epstein-Barr virus (EBV) infection often occurs in early childhood and is asymptomatic. However, if delayed until adolescence, primary infection may manifest as acute infectious mononucleosis (AIM), a febrile illness characterised by global CD8+ T-cell lymphocytosis, much of it reflecting a huge expansion of activated EBV-specific CD8+ T-cells. While the events of AIM have been intensely studied, little is known about how these relate to asymptomatic primary infection. Here Gambian children (14-18 months old, an age at which many acquire the virus) were followed for the ensuing six months, monitoring circulating EBV loads, antibody status against virus capsid antigen (VCA) and both total and virus-specific CD8+ T-cell numbers. Many children were IgG anti-VCA-positive and, though no longer IgM-positive, still retained high virus loads comparable to AIM patients and had detectable EBV-specific T-cells, some still expressing activation markers. Virus loads and the frequency/activation status of specific T-cells decreased over time, consistent with resolution of a relatively recent primary infection. Six children with similarly high EBV loads were IgM anti-VCA-positive, indicating very recent infection. In three of these donors with HLA types allowing MHC-tetramer analysis, highly activated EBV-specific T-cells were detectable in the blood with one individual epitope response reaching 15% of all CD8+ T-cells. That response was culled and the cells lost activation markers over time, just as seen in AIM. However, unlike AIM, these events occurred without marked expansion of total CD8+ numbers. Thus asymptomatic EBV infection in children elicits a virus-specific CD8+ T-cell response that can control the infection without over-expansion; conversely, in AIM it appears the CD8 over-expansion, rather than virus load per se, is the cause of disease symptoms.

Measles vaccination in the presence or absence of maternal measles antibody: impact on child survival

BACKGROUND

Measles vaccine (MV) has a greater effect on child survival when administered in early infancy, when maternal antibody may still be present.

METHODS

To test whether MV has a greater effect on overall survival if given in the presence of maternal measles antibody, we reanalyzed data from 2 previously published randomized trials of a 2-dose schedule with MV given at 4-6 months and at 9 months of age. In both trials antibody levels had been measured before early measles vaccination.

RESULTS

In trial I (1993-1995), the mortality rate was 0.0 per 1000 person-years among children vaccinated with MV in the presence of maternal antibody and 32.3 per 1000 person-years without maternal antibody (mortality rate ratio [MRR], 0.0; 95% confidence interval [CI], 0-.52). In trial II (2003-2007), the mortality rate was 4.2 per 1000 person-years among children vaccinated in presence of maternal measles antibody and 14.5 per 1000 person-years without measles antibody (MRR, 0.29; 95% CI, .09-.91). Possible confounding factors did not explain the difference. In a combined analysis, children who had measles antibody detected when they received their first dose of MV at 4-6 months of age had lower mortality than children with no maternal antibody, the MRR being 0.22 (95% CI, .07-.64) between 4-6 months and 5 years.

CONCLUSIONS

Child mortality in low-income countries may be reduced by vaccinating against measles in the presence of maternal antibody, using a 2-dose schedule with the first dose at 4-6 months (earlier than currently recommended) and a booster dose at 9-12 months of age.

CLINICAL TRIALS REGISTRATION

NCT00168558.

Efficacy and effectiveness of infant vaccination against chronic hepatitis B in the Gambia Hepatitis Intervention Study (1986-90) and in the nationwide immunisation program

BACKGROUND

Gambian infants were not routinely vaccinated against hepatitis B virus (HBV) before 1986. During 1986-90 the Gambia Hepatitis Intervention Study (GHIS) allocated 125,000 infants, by area, to vaccination or not and thereafter all infants were offered the vaccine through the nationwide immunisation programme. We report HBV serology from samples of GHIS vaccinees and unvaccinated controls, and from children born later.

METHODS

During 2007-08, 2670 young adults born during the GHIS (1986-90) were recruited from 80 randomly selected villages and four townships. Only 28% (753/2670) could be definitively linked to their infant HBV vaccination records (255 fully vaccinated, 23 partially vaccinated [1-2 doses], 475 not vaccinated). All were tested for current HBV infection (HBV surface antigen [HBsAg]) and, if HBsAg-negative, evidence of past infection (HBV core-protein antibody [anti-HBc]). HBsAg-positive samples (each with two age- and sex-matched HBsAg-negative samples) underwent liver function tests. In addition, 4613 children born since nationwide vaccination (in 1990-2007) were tested for HBsAg. Statistical analyses ignore clustering.

RESULTS

Comparing fully vaccinated vs unvaccinated GHIS participants, current HBV infection was 0.8% (2/255) vs 12.4% (59/475), p < 0.0001, suggesting 94% (95% CI 77-99%) vaccine efficacy. Among unvaccinated individuals, the prevalence was higher in males (p = 0.015) and in rural areas (p = 0.009), but adjustment for this did not affect estimated vaccine efficacy. Comparing fully vaccinated vs unvaccinated participants, anti-HBc was 27.4% (70/255) vs 56.0% (267/475), p < 0.00001. Chronic active hepatitis was not common: the proportion of HBsAg-positive subjects with abnormal liver function tests (ALT > 2 ULN) was 4.1%, compared with 0.2% in those HBsAg-negative. The prevalence of antibodies to hepatitis C virus was low (0.5%, 13/2592). In children born after the end of GHIS, HBsAg prevalence has remained low; 1.4% (15/1103) in those born between 1990-97, and 0.3% (9/35150) in those born between 1998-2007.

CONCLUSIONS

Infant HBV vaccination achieves substantial protection against chronic carriage in early adulthood, even though approximately a quarter of vaccinated young adults have been infected. This protection persists past the potential onset of sexual activity, reinforcing previous GHIS findings of protection during childhood and suggesting no need for a booster dose. Nationwide infant HBV vaccination is controlling chronic infection remarkably effectively.

Host iron redistribution as a risk factor for incident tuberculosis in HIV infection: an 11-year retrospective cohort study

BACKGROUND

Identifying people at higher risk of developing tuberculosis with human immunodeficiency virus (HIV) infection may improve clinical management of co-infections. Iron influences tuberculosis (TB) pathogenesis, but understanding the exact mechanisms of how and timing of when iron is involved remains challenging since biological samples are rarely available from the disease susceptibility period due to the difficulty in predicting in who and when, if ever, TB will develop. The objective of this research was to determine how host iron status measured at HIV diagnosis and genotypes related to host iron metabolism were associated with incident TB.

METHODS

Archived clinical data, plasma and DNA were analyzed from 1139 adult participants in a large HIV-1, HIV-2 and dual seroprevalent cohort based at the Medical Research Council Laboratories in The Gambia. Incident pulmonary and/or extrapulmonary TB diagnoses a minimum of 28 days after HIV diagnosis were independently re-confirmed using available evidence (n=152). Multiple host iron status biomarkers, Haptoglobin and solute carrier family 11, member 1 (SLC11A1) genotypes were modeled to characterize how indicators of host iron metabolism were associated with TB susceptibility.

RESULTS

Hemoglobin (incidence rate ratio, IRR=0.88, 95% CI=0.79-0.98), plasma transferrin (IRR=0.53, 0.33-0.84) and ferritin (IRR=1.26, 1.05-1.51) were significantly associated with TB after adjusting for TB susceptibility factors. While genotype associations were not statistically significant, SLC11A1 associations replicated similar directions as reported in HIV-seronegative meta-analyses.

CONCLUSIONS

Evidence of host iron redistribution at HIV diagnosis was associated with incident TB, and genetic influences on iron homeostasis may be involved. Low hemoglobin was associated with subsequent diagnosis of TB, but when considered in combination with additional iron status biomarkers, the collective findings point to a mechanism whereby anemia and iron redistribution are likely due to viral and/or bacteria-driven processes and the host immune response to infection. As a result, iron supplementation may not be efficacious or safe under these circumstances. Clinical and nutritional management of HIV and Mycobacterium tuberculosis co-infected individuals, especially in regions where food insecurity and malnutrition co-exist, may be further improved when the iron-related TB risk factors identified here are better understood and managed to favor host rather than pathogen outcomes.

Clinical predictors cannot replace biological predictors in HIV-2 infection in a community setting in West Africa

Objective

To identify clinical predictors of mortality in HIV-2-infected individuals that may be used in place of CD4 count or plasma viral load (PVL) to guide treatment management in resource-limited settings.

Methods

A prospective community cohort study of HIV-infected and HIV-negative individuals in a rural area of Guinea-Bissau has been ongoing since 1989. In 2003 participants were invited for a clinical examination and blood tests. They were followed-up for vital status until 2010. Antiretroviral treatment (ART) became available in 2007. Cox regression was used to examine the association of clinical measures (World Health Organization (WHO) stage, body mass index (BMI), mid-upper arm circumference (MUAC), and WHO performance scale) measured in 2003 with subsequent mortality.

Results

In 2003, 146 HIV-2-infected individuals (68% women; mean age 56 years) were examined. Over the next 7 years, 44 (30%) died. BMI < 18.5 kg/m² was associated with a crude mortality hazard ratio (HR) of 1.9 (95% confidence interval (CI) 1.0–3.9, p = 0.08); adjusted for age and sex, HR 1.8 (95% CI 0.9–3.8, p = 0.1). MUAC <230 mm in women and <240 mm in men was also associated with an elevated mortality HR, though statistical evidence was weak (crude HR 2.2, 95% CI 0.9–5.3, p = 0.1). WHO clinical stage and WHO performance scale were not associated with mortality (p = 0.6 and p = 0.2, respectively, for crude associations).

Conclusions

Baseline BMI, MUAC, WHO stage, and WHO performance scale were not strong or statistically significant predictors of mortality among HIV-2-infected individuals. CD4 count and PVL are more reliable tools, when available, for the management of HIV-2-infected patients in the community setting.

Non-specific effects of standard measles vaccine at 4.5 and 9 months of age on childhood mortality: randomised controlled trial

OBJECTIVE

To examine in a randomised trial whether a 25% difference in mortality exists between 4.5 months and 3 years of age for children given two standard doses of Edmonston-Zagreb measles vaccines at 4.5 and 9 months of age compared with those given one dose of measles vaccine at 9 months of age (current policy).

DESIGN

Randomised controlled trial.

SETTING

The Bandim Health Project, Guinea-Bissau, which maintains a health and demographic surveillance system in an urban area.

PARTICIPANTS

6648 children aged 4.5 months of age who had received three doses of diphtheria-tetanus-pertussis vaccine at least four weeks before enrolment. A large proportion of the children (80%) had previously taken part in randomised trials of neonatal vitamin A supplementation.

INTERVENTION

Children were randomised to receive Edmonston-Zagreb measles vaccine at 4.5 and 9 months of age (group A), no vaccine at 4.5 months and Edmonston-Zagreb measles vaccine at 9 months of age (group B), or no vaccine at 4.5 months and Schwarz measles vaccine at 9 months of age (group C). Main outcome measure Mortality rate ratio between 4.5 and 36 months of age for group A compared with groups B and C. Secondary outcomes tested the hypothesis that the beneficial effect was stronger in the 4.5 to 9 months age group, in girls, and in the dry season, but the study was not powered to test whether effects differed significantly between subgroups.

RESULTS

In the intention to treat analysis of mortality between 4.5 and 36 months of age the mortality rate ratio of children who received two doses of Edmonston-Zagreb vaccine at 4.5 and 9 months of age compared with those who received a single dose of Edmonston-Zagreb vaccine or Schwarz vaccine at 9 months of age was 0.78 (95% confidence interval 0.59 to 1.05). In the analyses of secondary outcomes, the intention to treat mortality rate ratio was 0.67 (0.38 to 1.19) between 4.5 and 9 months and 0.83 (0.83 to 1.16) between 9 and 36 months of age. The effect on mortality between 4.5 and 36 months of age was significant for girls (intention to treat mortality rate ratio 0.64 (0.42 to 0.98)), although this was not significantly different from the effect in boys (0.95 (0.64 to 1.42)) (interaction test, P=0.18). The effect did not differ between the dry season and the rainy season. As neonatal vitamin A supplementation is not WHO policy, the analyses were done separately for the 3402 children who did not receive neonatal vitamin A. In these children, the two dose Edmonston-Zagreb measles vaccine schedule was associated with a significantly lower mortality between 4.5 and 36 months of age (intention to treat mortality rate ratio 0.59 (0.39 to 0.89)). The effect was again significant for girls but not statistically significant from the effect in boys. When measles cases were censored, the intention to treat mortality rate ratio was 0.65 (0.43 to 0.99).

CONCLUSIONS

Although the overall effect did not reach statistical significance, the results may indicate that a two dose schedule with Edmonston-Zagreb measles vaccine given at 4.5 and 9 months of age has beneficial non-specific effects on children's survival, particularly for girls and for children who have not received neonatal vitamin A. This should be tested in future studies in different locations.

TRIAL REGISTRATION

Clinical trials NCT00168558.

Host genetic factors and vaccine-induced immunity to HBV infection: haplotype analysis

Hepatitis B virus (HBV) infection remains a significant health burden world-wide, although vaccines help decrease this problem. We previously identified associations of single nucleotide polymorphisms in several candidate genes with vaccine-induced peak antibody level (anti-HBs), which is predictive of long-term vaccine efficacy and protection against infection and persistent carriage; here we report on a haplotype-based analysis. A total of 688 SNPs from 117 genes were examined for a two, three and four sliding window haplotype analysis in a Gambian cohort. Analysis was performed on 197 unrelated individuals, 454 individuals from 174 families, and the combined sample (N = 651). Global and individual haplotype association tests were carried out (adjusted for covariates), employing peak anti-HBs level as outcome. Five genes (CD44, CD58, CDC42, IL19 and IL1R1) had at least one significant haplotype in the unrelated or family analysis as well as the combined analysis. Previous single locus results were confirmed for CD44 (combined global p = 9.1×10⁻⁵ for rs353644-rs353630-rs7937602) and CD58 (combined global p = 0.008 for rs1414275-rs11588376-rs1016140). Haplotypes in CDC42, IL19 and IL1R1 also associated with peak anti-HBs level. We have identified strong haplotype effects on HBV vaccine-induced antibody level in five genes, three of which, CDC42, IL19 and IL1R1, did not show evidence of association in a single SNP analyses and corroborated the majority of these effects in two datasets. The haplotype analysis identified associations with HBV vaccine-induced immunity in several new genes.

Polyfunctional CD4(+) and CD8(+) T cell responses to tuberculosis antigens in HIV-1-infected patients before and after anti-retroviral treatment

Tuberculosis (TB) kills 2 million people per year and infection with HIV is the most potent known risk factor for progression to active TB. An understanding of the immune response to TB Ags in HIV-infected patients is required to develop optimal TB vaccines and diagnostics. We assessed polyfunctional (IFN-gamma(+)IL-2(+)TNF-alpha(+)) T cell responses to TB Ags in three groups of HIV-1-infected patients dependent on their TB status, CD4 counts, and anti-retroviral exposure. We found that although the proportion of IFN-gamma cells in response to TB Ags was higher in patients with low CD4 counts, the responding cells changed from a polyfunctional CD4(+) to a monofunctional CD8(+) response. The overall polyfunctionality of the cells was restored by 12 mo of anti-retroviral therapy and primarily involved CD4(+) T cells with an effector memory phenotype. These findings have major implications for diagnosis of TB and in vaccine development strategies for TB in HIV-1-infected patients.

Acquisition of antibody isotypes against Plasmodium falciparum blood stage antigens in a birth cohort

Information on the period during which infants lose their maternally derived antibodies to malaria and begin to acquire naturally their own immune responses against parasite antigens is crucial for understanding when malaria vaccines may be best administered. This study investigated the rates of decline and acquisition of serum antibody isotypes IgG1, IgG2, IgG3, IgG4, IgM and IgA to Plasmodium falciparum antigens apical membrane antigen (AMA1), merozoite surface proteins (MSP1-19, MSP2 and MSP3) in a birth cohort of 53 children living in an urban area in the Gambia, followed over the first 3 years of life (sampled at birth, 4, 9, 18 and 36 months). Antigen-specific maternally transferred antibody isotypes of all IgG subclasses were detected at birth and were almost totally depleted by 4 months of age. Acquisition of specific antibody isotypes to the antigens began with IgM, followed by IgG1 and IgA. Against the MSP2 antigen, IgG1 but not IgG3 responses were observed in the children, in contrast with the maternally derived antibodies to this antigen that were mostly IgG3. This confirms that IgG subclass responses to MSP2 are strongly dependent on age or previous malaria experience, polarized towards IgG1 early in life and to IgG3 in older exposed individuals.

Host genetic contribution to the cellular immune response to Chlamydia trachomatis: Heritability estimate from a Gambian twin study

If the cellular immune response to Chlamydia trachomatis is subject to genetic influences, the degree and mechanisms of such genetic control may have important implications for vaccine development. We estimated the relative contribution of host genetics to the total variation in lymphoproliferative responses to C. trachomatis antigen by analyzing these responses in 64 Gambian twin pairs from trachoma endemic areas. Zygosity was determined by restriction fragment length polymorphism analysis of minisatellite probes and microsatellite typing. Proliferative responses to serovar A elementary body antigen were estimated in monozygotic (MZ) and dizygotic (DZ) twin pairs. We found a stronger correlation and lower within-pair variability in these responses in MZ than in DZ twin pairs. The heritability estimate was 0.39 (P = 0.07) suggesting that host genetic factors contributed 39% of the variation. A better understanding of these genetic influences will contribute to the elucidation of preventive therapies for ocular C. trachomatis infection and may identify important mechanisms in protection for rational vaccine construction.

Heritability of antibody isotype and subclass responses to Plasmodium falciparum antigens

Background

It is important to understand the extent to which genetic factors regulate acquired immunity to common infections. A classical twin study design is useful to estimate the heritable component of variation in measurable immune parameters.

Methodology/Principal Findings

This study assessed the relative heritability of different plasma antibody isotypes and subclasses (IgG1, IgG2, IgG3, IgG4, IgM, IgA and IgE) naturally acquired to P. falciparum blood stage antigens AMA1, MSP1-19, MSP2 (two allelic types) and MSP3 (two allelic types). Separate analyses were performed on plasma from 213 pairs of Gambian adult twins, 199 child twin pairs sampled in a dry season when there was little malaria transmission, and another set of 107 child twin pairs sampled at the end of the annual wet season when malaria was common. There were significantly positive heritability (h²) estimates for 48% (20/42) of the specific antibody assays (for the seven isotypes and subclasses to the six antigens tested) among the adults, 48% (20/42) among the children in the dry season and 31% (13/42) among the children in the wet season. In children, there were significant heritability estimates for IgG4 reactivity against each of the antigens, and this subclass had higher heritability than the other subclasses and isotypes. In adults, 75% (15/20) of the significantly heritable antigen-specific isotype responses were attributable to non-HLA class II genetic variation, whereas none showed a significant HLA contribution.

Significance

Genome-wide approaches are now warranted to map the major genetic determinants of variable antibody isotype and subclass responses to malaria, alongside evaluation of their impact on infection and disease. Although plasma levels of IgG4 to malaria antigens are generally low, the exceptionally high heritability of levels of this subclass in children deserves particular investigation.

Mortality in HIV infection is independently predicted by host iron status and SLC11A1 and HP genotypes, with new evidence of a gene-nutrient interaction

BACKGROUND

Iron-related genes and iron status may independently contribute to variable HIV outcomes. The nature of the biologically plausible gene-nutrient interaction remains unknown.

OBJECTIVES

The objectives were to investigate whether iron-related genotypes and clinically abnormal iron status independently predict mortality in HIV and whether a gene-nutrient interaction exists.

DESIGN

Baseline plasma, DNA, and clinical data were obtained from 1362 HIV-seropositive Gambian adults followed for 11.5 y to ascertain all-cause mortality. Iron status was estimated on the basis of plasma iron, soluble transferrin receptor (sTfR), ferritin, transferrin, transferrin index, and log(sTfR/ferritin). One haptoglobin (HP) and 5 SLC11A1 (NRAMP1) polymorphisms were genotyped.

RESULTS

SLC11A1-SLC3 and CAAA polymorphisms were the best independent genetic predictors of mortality [adjusted mortality rate ratio (95% CI)]: SLC3:G/C = 0.59 (95% CI: 0.45, 0.85), CAAA:del/ins = 1.51 (95% CI: 1.10, 2.07). In an adjusted model that included all polymorphisms, SLC1:199/199, SLC1:other/other, SLC6a:A/A, and CAAA:del/ins were associated with significantly greater mortality, whereas Hp 2-1 and SLC3:G/C were protective. In unadjusted analyses, all biomarker concentrations were significantly associated with mortality. In an extension of previous findings, both low and elevated iron states were associated with mortality, but the nature of the risk was variable, with linear, inversely linear, and U-shaped associations depending on the biomarker. Mortality was significantly lower in HIV-2 than in HIV-1 infection in the presence of abnormal (low or elevated) iron status. A gene-iron interaction was detected (likelihood-ratio test P = 0.018); however, subject numbers restricted category-specific interpretation.

CONCLUSIONS

Iron-related genes, iron status, and their interaction predict mortality in HIV. These findings illustrate the complexity and uncertainty surrounding best practice for managing abnormal iron status and anemia during HIV infection and in regions with a high risk of infection.

Changes in malaria indices between 1999 and 2007 in The Gambia: a retrospective analysis

BACKGROUND

Malaria is a major cause of morbidity and mortality in Africa. International effort and funding for control has been stepped up, with substantial increases from 2003 in the delivery of malaria interventions to pregnant women and children younger than 5 years in The Gambia. We investigated the changes in malaria indices in this country, and the causes and public-health significance of these changes.

METHODS

We undertook a retrospective analysis of original records to establish numbers and proportions of malaria inpatients, deaths, and blood-slide examinations at one hospital over 9 years (January, 1999-December, 2007), and at four health facilities in three different administrative regions over 7 years (January, 2001-December, 2007). We obtained additional data from single sites for haemoglobin concentrations in paediatric admissions and for age distribution of malaria admissions.

FINDINGS

From 2003 to 2007, at four sites with complete slide examination records, the proportions of malaria-positive slides decreased by 82% (3397/10861 in 2003 to 337/6142 in 2007), 85% (137/1259 to 6/368), 73% (3664/16932 to 666/11333), and 50% (1206/3304 to 336/1853). At three sites with complete admission records, the proportions of malaria admissions fell by 74% (435/2530 to 69/1531), 69% (797/2824 to 89/1032), and 27% (2204/4056 to 496/1251). Proportions of deaths attributed to malaria in two hospitals decreased by 100% (seven of 115 in 2003 to none of 117 in 2007) and 90% (22/122 in 2003 to one of 58 in 2007). Since 2004, mean haemoglobin concentrations for all-cause admissions increased by 12 g/L (85 g/L in 2000-04 to 97 g/L in 2005-07), and mean age of paediatric malaria admissions increased from 3.9 years (95% CI 3.7-4.0) to 5.6 years (5.0-6.2).

INTERPRETATION

A large proportion of the malaria burden has been alleviated in The Gambia. Our results encourage consideration of a policy to eliminate malaria as a public-health problem, while emphasising the importance of accurate and continuous surveillance.

Protective efficacy of standard Edmonston-Zagreb measles vaccination in infants aged 4.5 months: interim analysis of a randomised clinical trial

OBJECTIVE

To examine the protective efficacy of measles vaccination in infants in a low income country before 9 months of age.

DESIGN

Randomised clinical trial.

PARTICIPANTS

1333 infants aged 4.5 months: 441 in treatment group and 892 in control group.

SETTING

Urban area in Guinea-Bissau.

INTERVENTION

Measles vaccination using standard titre Edmonston-Zagreb vaccine at 4.5 months of age.

MAIN OUTCOME MEASURES

Vaccine efficacy against measles infection, admission to hospital for measles, and measles mortality before standard vaccination at 9 months of age.

RESULTS

28% of the children tested at 4.5 months of age had protective levels of maternal antibodies against measles at enrolment. After early vaccination against measles 92% had measles antibodies at 9 months of age. A measles outbreak offered a unique situation for testing the efficacy of early measles vaccination. During the outbreak, 96 children developed measles; 19% of unvaccinated children had measles before 9 months of age. The monthly incidence of measles among the 441 children enrolled in the treatment arm was 0.7% and among the 892 enrolled in the control arm was 3.1%. Early vaccination with the Edmonston-Zagreb measles vaccine prevented infection; vaccine efficacy for children with serologically confirmed measles and definite clinical measles was 94% (95% confidence interval 77% to 99%), for admissions to hospital for measles was 100% (46% to 100%), and for measles mortality was 100% (-42% to 100%). The number needed to treat to prevent one case of measles between ages 4.5 months and 9 months during the epidemic was 7.2 (6.8 to 9.2). The treatment group tended to have lower overall mortality (mortality rate ratio 0.18, 0.02 to 1.36) although this was not significant.

CONCLUSIONS

In low income countries, maternal antibody levels against measles may be low and severe outbreaks of measles can occur in infants before the recommended age of vaccination at 9 months. Outbreaks of measles may be curtailed by measles vaccination using the Edmonston-Zagreb vaccine as early as 4.5 months of age. TRIAL REGISTRATION CLINICAL TRIALS: NCT00168558 [ClinicalTrials.gov].

Polyfunctional T cell responses are a hallmark of HIV-2 infection

HIV-2 is distinguished clinically and immunologically from HIV-1 infection by delayed disease progression and maintenance of HIV-specific CD4(+) T cell help in most infected subjects. Thus, HIV-2 provides a unique natural human model in which to investigate correlates of immune protection against HIV disease progression. Here, we report a detailed assessment of the HIV-2-specific CD4(+) and CD8(+) T cell response compared to HIV-1, using polychromatic flow cytometry to assess the quality of the HIV-specific T cell response by measuring IFN-gamma, IL-2, TNF-alpha, MIP-1beta, and CD107a mobilization (degranulation) simultaneously following Gag peptide stimulation. We find that HIV-2-specific CD4(+) and CD8(+) T cells are more polyfunctional that those specific for HIV-1 and that polyfunctional HIV-2-specific T cells produce more IFN-gamma and TNF-alpha on a per-cell basis than monofunctional T cells. Polyfunctional HIV-2-specific CD4(+) T cells were generally more differentiated and expressed CD57, while there was no association between function and phenotype in the CD8(+) T cell fraction. Polyfunctional HIV-specific T cell responses are a hallmark of non-progressive HIV-2 infection and may be related to good clinical outcome in this setting.

Changes in viral load and HBsAg and HBeAg status with age in HBV chronic carriers in The Gambia

Background

Little is known about changes in hepatitis B viral load (HBV DNA) in relation to age in Africa. The aim of this study is to determine the natural course of HBV chronic infection, particularly in relation to sequential changes in serum HBV DNA levels and hepatitis B surface (HBsAg) antigen/hepatitis e antigen (HBeAg) status by age.

Methods

The study was conducted on 190 HBV chronic carriers, aged 1–19 years who were followed for 19 years. 160, 99 and 123 were traced at 5, 9 and 19 years later. All available samples were tested for HBsAg and HBeAg, whilst 170, 61, 63 and 81 were tested for HBV DNA at the baseline, and at 5, 9 and 19 years following recruitment.

Results

In general HBeAg which correlated with high levels of HBV DNA was lost at a much faster rate than HBsAg. 86% of the carriers who were recruited at the age of 1–4 yrs lost HBeAg by the age of 19 years compared to 30% who lost HBsAg. HBeAg negative carriers had serum HBV DNA levels of < 10⁵ copies per mL, HBV DNA positivity declined from 100% in 1–4 yrs old carriers at recruitment to 62.5%,60% and 88% at 5, 9 and 19 years respectively following recruitment.

Conclusion

After 19 years of follow up, the majority of HBV surface antigen carriers had lost HBeAg positivity and had low levels of viral replication. However small proportions (10–20%) retained HBeAg and continue to have high levels of viral replication.

Host genetic factors and vaccine-induced immunity to hepatitis B virus infection

Background

Vaccination against hepatitis B virus infection (HBV) is safe and effective; however, vaccine-induced antibody level wanes over time. Peak vaccine-induced anti-HBs level is directly related to antibody decay, as well as risk of infection and persistent carriage despite vaccination. We investigated the role of host genetic factors in long-term immunity against HBV infection based on peak anti-HBs level and seroconversion to anti-HBc.

Methods

We analyzed 715 SNP across 133 candidate genes in 662 infant vaccinees from The Gambia, assessing peak vaccine-induced anti-HBs level and core antibody (anti-HBc) status, whilst adjusting for covariates. A replication study comprised 43 SNPs in a further 393 individuals.

Results

In our initial screen we found variation in IFNG, MAPK8, and IL10RA to affect peak anti-HBs level (GMTratio of <0.6 or >1.5 and P≤0.001) and lesser associations in other genes. Odds of core-conversion was associated with variation in CD163. A coding change in ITGAL (R719V) with likely functional relevance showed evidence of association with increased peak anti-HBs level in both screens (1st screen: s595_22 GMTratio 1.71, P = 0.013; 2nd screen: s595_22 GMTratio 2.15, P = 0.011).

Conclusion

This is to our knowledge the largest study to date assessing genetic determinants of HBV vaccine-induced immunity. We report on associations with anti-HBs level, which is directly related to durability of antibody level and predictive of vaccine efficacy long-term. A coding change in ITGAL, which plays a central role in immune cell interaction, was shown to exert beneficial effects on induction of peak antibody level in response to HBV vaccination. Variation in this gene does not appear to have been studied in relation to immune responses to viral or vaccine challenges previously. Our findings suggest that genetic variation in loci other than the HLA region affect immunity induced by HBV vaccination.

Dendritic cells are less susceptible to human immunodeficiency virus type 2 (HIV-2) infection than to HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) infection of dendritic cells (DCs) has been documented in vivo and may be an important contributor to HIV-1 transmission and pathogenesis. HIV-1-specific CD4(+) T cells respond to HIV antigens presented by HIV-1-infected DCs and in this process become infected, thereby providing a mechanism through which HIV-1-specific CD4(+) T cells could become preferentially infected in vivo. HIV-2 disease is attenuated with respect to HIV-1 disease, and host immune responses are thought to be contributory. Here we investigated the susceptibility of primary myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) to infection by HIV-2. We found that neither CCR5-tropic primary HIV-2 isolates nor a lab-adapted CXCR4-tropic HIV-2 strain could efficiently infect mDCs or pDCs, though these viruses could infect primary CD4(+) T cells in vitro. HIV-2-exposed mDCs were also incapable of transferring virus to autologous CD4(+) T cells. Despite this, we found that HIV-2-specific CD4(+) T cells contained more viral DNA than memory CD4(+) T cells of other specificities in vivo. These data suggest that either infection of DCs is not an important contributor to infection of HIV-2-specific CD4(+) T cells in vivo or that infection of DCs by HIV-2 occurs at a level that is undetectable in vitro. The frequent carriage of HIV-2 DNA within HIV-2-specific CD4(+) T cells, however, does not appear to be incompatible with preserved numbers and functionality of HIV-2-specific CD4(+) T cells in vivo, suggesting that additional mechanisms contribute to maintenance of HIV-2-specific CD4(+) T-cell help in vivo.

Long-term protection against HBV chronic carriage of Gambian adolescents vaccinated in infancy and immune response in HBV booster trial in adolescence

Background

Chronic infection with hepatitis B virus (HBV) arising in childhood is associated with hepatocellular carcinoma in adult life. Between 1986 and 1990, approximately 120,000 Gambian newborns were enrolled in a randomised controlled trial to assess the effectiveness of infant HBV vaccination on the prevention of hepatocellular carcinoma in adulthood. These children are now in adolescence and approaching adulthood, when the onset of sexual activity may challenge their hepatitis B immunity. Thus a booster dose in adolescence could be important to maintain long-term protection.

Methods

Fifteen years after the start of the HBV infant vaccination study, 492 vaccinated and 424 unvaccinated children were identified to determine vaccine efficacy against infection and carriage in adolescence. At the same time, 297 of the 492 infant-vaccinated subjects were randomly offered a booster dose of HBV vaccine. Anti-HBs was measured before the booster, and two weeks and 1 year afterwards (ISRCTN71271385).

Results

Vaccine efficacy 15 years after vaccination was 67.0% against infection as manifest by anti-HBc positivity (95% CI 58.2–74.6%), and 96.6% against HBsAg carriage (95% CI 91.5–100%). 31.2% of participants had detectable anti-HBs with a GMC of 32 IU/l. For 168 boosted participants GMC anti-HBs responses were 38 IU/l prior to vaccination, 524 IU/l two weeks after boosting, and 101 IU/l after 1 year.

Conclusions

HBV vaccination in infants confers very good protection against carriage up to 15 years of age, although a large proportion of vaccinated subjects did not have detectable anti-HBs at this age. The response to boosting persisted for at least a year.

Trial Registration

Controlled-Trials.com ISRCTN71271385

Risk factors for and clinical outcome of congenital cytomegalovirus infection in a peri-urban West-African birth cohort

BACKGROUND

Congenital cytomegalovirus (CMV) infection is the most prevalent congenital infection worldwide. Epidemiology and clinical outcomes are known to vary with socio-economic background, but few data are available from developing countries, where the overall burden of infectious diseases is frequently high.

METHODOLOGY/PRINCIPAL FINDINGS

As part of an ongoing birth cohort study in The Gambia among term infants, urine samples were collected at birth and tested by PCR for the presence of CMV DNA. Risk factors for transmission and clinical outcome were assessed, including placental malaria infection. Babies were followed up at home monthly for morbidity and anthropometry, and at one year of age a clinical evaluation was performed. The prevalence of congenital CMV infection was 5.4% (40/741). A higher prevalence of hepatomegaly was the only significant clinical difference at birth. Congenitally infected children were more often first born babies (adjusted odds ratio (OR) 5.3, 95% confidence interval (CI) 2.0-13.7), more frequently born in crowded compounds (adjusted OR 2.9, 95%CI 1.0-8.3) and active placental malaria was more prevalent (adjusted OR 2.9, 95%CI 1.0-8.4). These associations were corrected for maternal age, bed net use and season of birth. During the first year of follow up, mothers of congenitally infected children reported more health complaints for their child.

CONCLUSIONS/SIGNIFICANCE

In this study, the prevalence of congenital CMV among healthy neonates was much higher than previously reported in industrialised countries, and was associated with active placental malaria infection. There were no obvious clinical implications during the first year of life. The effect of early life CMV on the developing infant in the Gambia could be mitigated by environmental factors, such as the high burden of other infections.

Out of Africa: what can we learn from HIV-2 about protective immunity to HIV-1?

Most people infected with human immunodeficiency virus 2 (HIV-2) do not progress to disease, even though the minority who do cannot be distinguished clinically from HIV-1-infected patients. Here we review what is known about the basis of viral control in HIV-2 infection.

Prophylactic antibiotics to prevent pneumonia and other complications after measles: community based randomised double blind placebo controlled trial in Guinea-Bissau

OBJECTIVE

To investigate whether prophylactic antibiotics can prevent complications of measles.

DESIGN

Community based, randomised, double blind, placebo controlled trial.

SETTING

Bandim Health Project study area in Bissau, Guinea-Bissau, west Africa.

PARTICIPANTS

84 patients with measles during a measles epidemic in Bissau in 1998 (fewer than originally planned owing to interruption by war).

INTERVENTIONS

Sulfamethoxazole-trimethoprim (co-trimoxazole) or placebo for seven days.

MAIN OUTCOME MEASURES

Pneumonia and admission to hospital. Also weight change during the first month of infection, diarrhoea, severe fever, oral thrush, stomatitis, conjunctivitis, and otitis media.

RESULTS

The median age of the patients with measles was 5.4 (range 0.49-24.8) years. One of 46 participants who received co-trimoxazole developed pneumonia, in contrast to six of 38 participants who received placebo (odds ratio 0.08 (95% confidence interval 0 to 0.56), adjusted for age group). The number needed to treat was 7 (4 to 48). All three participants admitted to hospital had received placebo (P=0.09). The weight gain during the first month after inclusion was 15 (2-29) g/day in the placebo group and 32 (23-42) g/day in the co-trimoxazole group (P=0.04, adjusted for age group, weight for age at inclusion, measles vaccination status, and duration of disease). Significantly less conjunctivitis occurred among recipients of co-trimoxazole than placebo, as well as a non-significant tendency to less diarrhoea, severe fever, oral thrush, and stomatitis. Complications of otitis media were the same in the two groups.

CONCLUSIONS

The group that received prophylactic antibiotics had less pneumonia and conjunctivitis and had significantly higher weight gains in the month after inclusion. The results indicate that prophylactic antibiotics may have an important role in the management of measles infection in low income countries.

TRIAL REGISTRATION

Clinical trials NCT00168532.

Similar long-term vaccine efficacy of two versus three doses of HBV vaccine in early life

WHO currently recommends three vaccinations against hepatitis B to provide optimal protection against infection and carriage. However, immunological theory and mathematical modelling suggest that similar protection could be induced with two doses, and trials among adolescents and adults have shown comparable rates for both primary seroprotection and geometric mean titres following vaccination. We determined vaccine efficacy among 60 children who only received two doses of hepatitis B vaccine as infants and among 463 children who had received three doses after 4-7 years of follow-up. Vaccine efficacy among the two-dose group was 86.3% against anti-HBc positivity (infection) and 92.3% against HBsAg positivity (carriage), which was similar to the vaccine efficacy found among the participants who had received three doses. To confirm this comparable vaccine efficacy a randomised controlled non-inferiority trial with long-term follow-up is needed.

The role of Chlamydia pneumoniae in acute respiratory tract infections in young children in The Gambia, West Africa

BACKGROUND

Little is known about the role of Chlamydia pneumoniae in the aetiology of acute respiratory tract infections (ARI) in children in developing countries.

AIMS

To obtain better information, we studied the presence of C. pneumoniae and its association with clinical signs and symptoms of ARI in children under 5 years of age in The Gambia.

METHODS

C. pneumoniae was sought by polymerase chain reaction in nasopharyngeal secretions and/or lung puncture aspirates from 324 infants under 3 months of age and 325 children between 3 months and 5 years of age with malnutrition, with or without pneumonia, and in control children. Clinical signs and symptoms for ARI and the spectrum of other viral and bacterial organisms were compared between those positive for C. pneumoniae and those negative.

RESULTS

Of 324 young infants, ten (3.1%) showed the presence of C. pneumoniae whereas in the older children 50 of 325 (15%) were positive for C. pneumoniae. There was no significant association between clinical signs and symptoms of ARI and C. pneumoniae positivity in the young infants. Among older infants and children, there was a trend to more frequent lobar alveolar changes in those positive for C. pneumoniae. No bacterial pathogens were found to be significantly associated with C. pneumoniae infection. However, there was an association with measles in the malnutrition group and with RSV in the young infants group.

CONCLUSIONS

In this study, C. pneumoniae was not associated with any particular clinical syndrome. We found no evidence that the organism plays a major role in ARI in young children in developing countries such as The Gambia.

Maintenance of HIV-specific CD4+ T cell help distinguishes HIV-2 from HIV-1 infection

Unlike HIV-1-infected people, most HIV-2-infected subjects maintain a healthy CD4+ T cell count and a strong HIV-specific CD4+ T cell response. To define the cellular immunological correlates of good prognosis in HIV-2 infection, we conducted a cross-sectional study of HIV Gag-specific T cell function in HIV-1- and HIV-2-infected Gambians. Using cytokine flow cytometry and lymphoproliferation assays, we show that HIV-specific CD4+ T cells from HIV-2-infected individuals maintained proliferative capacity, were not terminally differentiated (CD57-), and more frequently produced IFN-gamma or IL-2 than CD4+ T cells from HIV-1-infected donors. Polyfunctional (IFN-gamma+/IL-2+) HIV-specific CD4+ T cells were found exclusively in HIV-2+ donors. The disparity in CD4+ T cell responses between asymptomatic HIV-1- and HIV-2-infected subjects was not associated with differences in the proliferative capacity of HIV-specific CD8+ T cells. This study demonstrates that HIV-2-infected donors have a well-preserved and functionally heterogeneous HIV-specific memory CD4+ T cell response that is associated with delayed disease progression in the majority of infected people.

Class II cytokine receptor gene cluster is a major locus for hepatitis B persistence

Persistent hepatitis B virus infection is a major risk factor for hepatocellular carcinoma, the most frequent cancer in some developing countries. Up to 95% of those infected at birth and 15% of those infected after the neonatal period fail to clear hepatitis B virus, together resulting in approximately 350 million persistent carriers worldwide. Via a whole genome scan in Gambian families, we have identified a major susceptibility locus as a cluster of class II cytokine receptor genes on chromosome 21q22. Coding changes in two of these genes, the type I IFN receptor gene, IFN-AR2, and the IL-10RB gene that encodes a receptor chain for IL-10-related cytokines including the IFN-lambdas, are associated with viral clearance (haplotype P value = 0.0003), and in vitro assays support functional roles for these variants in receptor signaling.

Long‐Term Protection against Carriage of Hepatitis B Virus after Infant Vaccination

BACKGROUND

Carriage of hepatitis B virus (HBV) is a major risk factor for liver cirrhosis and hepatocellular carcinoma. Infant vaccination has been effective in preventing horizontal transmission during early childhood. It is unknown whether protection is maintained into early adulthood.

METHODS

In 1984, early childhood vaccination was introduced in 2 rural Gambian villages. In 2003, serological assessment of 81.5% of 1,350 eligible participants 1-24 years old was done, to determine vaccine efficacy against infection and carriage.

RESULTS

Overall vaccine efficacy against infection and carriage was 83.4% (95% confidence interval [CI], 79.8%-86.6%) and 96.5% (85% CI, 93.9%-98.9%), respectively. Vaccine efficacy against infection was similar when restricted to primary responders (85.3%), but a significant effect of peak antibody concentration was found. Both vaccine efficacy and levels of hepatitis B surface antibody (anti-HBs) decreased with age, resulting in a vaccine efficacy against infection and carriage among 20-24-year-old participants of 70.9% (95% CI, 60.4%-80.5%) and 91.1% (95% CI, 75.8%-100%), respectively. Fifteen years after vaccination, fewer than half of the vaccinees had detectable anti-HBs. The prevalence of carriage in the unvaccinated population was similar to the prevalence 20 years earlier.

CONCLUSIONS

HBV vaccination early during life can provide long-lasting protection against carriage, despite decreasing antibody levels. The role played by subclinical boosting and the necessity of a booster need to be evaluated.

Sixteen years of HIV surveillance in a West African research clinic reveals divergent epidemic trends of HIV-1 and HIV-2

BACKGROUND

The HIV-1 epidemic in West Africa is characterized by a slower rise than that in Eastern and Southern Africa. The HIV-2 epidemic in West Africa may be declining, but few long-term data exist.

METHODS

In a research clinic in The Gambia, HIV-1 and HIV-2 prevalence trends among all new patients being tested for HIV were examined over a 16 year period (1988 till 2003). In newly diagnosed patients a baseline CD4 count was done.

RESULTS

An HIV test was done in 23 363 patients aged 15 years or older. The prevalence of HIV-1 was 4.2% in 1988-91 and rose to 17.5% in 2001-03 (P < 0.0001, chi(2)-test for trend). The prevalence of HIV-2 was 7.0% in 1988-91 and declined to 4.0% in 2001-03 (P < 0.0001). HIV-1 prevalence increased and HIV-2 prevalence decreased with time in logistic regression models adjusting for age, sex, and indication for test (P < 0.0001). Baseline CD4 counts were available for 65% of patients. The median CD4 count was 215 cells/mm3 [interquartile range (IQR) 72-424] for HIV-1, and 274 (IQR 100-549) for HIV-2 infected patients. There was no marked trend of rise or decline in baseline CD4 count in either HIV-1 or HIV-2 infected patients over the study period. Forty-five per cent of newly diagnosed HIV patients had a CD4 count <200 cells/mm3.

CONCLUSIONS

These data suggest that HIV-1 prevalence is rising in The Gambia, and that HIV-2 is declining. HIV patients in The Gambia present late and almost half of patients would qualify for anti-retroviral treatment at their first visit.

Body mass index at time of HIV diagnosis: a strong and independent predictor of survival

BACKGROUND

Identification of basic prognostic indicators of HIV infection is essential before widespread antiretroviral therapy can be implemented in low-technology settings. This study assessed how well body mass index (BMI:kg/m2) predicts survival.

METHODS

BMI within 3 months of HIV diagnosis was obtained from 1657 patients aged > or = 15 years, recruited in a seroprevalent clinical cohort in The Gambia since 1992 and followed up at least once. Baseline CD4+ counts and clinical assessment at time of diagnosis were done.

RESULTS

The mortality hazard ratio (HR) of those with a baseline BMI <18 compared with those with a baseline BMI > or = 18 was 3.4 (95% CI, 3.0-3.9). The median survival time of those presenting with a BMI <16 was 0.8 years, in contrast to a median survival of 8.9 years for those with a baseline BMI > or = 22. Baseline BMI <18 remained a highly significant independent predictor of mortality after adjustment for age, sex, co-trimoxazole prophylaxis, tuberculosis, reported wasting at diagnosis, and baseline CD4+ cell count (adjusted HR = 2.5, 95% CI 2.0-3.0). Sensitivity and specificity of baseline BMI <18 was comparable to that of a CD4+ count <200 in predicting mortality within 6 months of diagnosis.

DISCUSSION

BMI at diagnosis is a strong, independent predictor of survival in HIV-infected patients in West Africa. In the absence of sophisticated clinical and laboratory support, BMI may also prove a useful guide for deciding when to initiate antiretroviral therapy.

Increased levels of aflatoxin-albumin adducts are associated with CYP3A5 polymorphisms in The Gambia, West Africa

OBJECTIVES

Major risk factors for hepatocellular carcinoma (HCC) are hepatitis viruses and exposure to aflatoxins, including aflatoxin B1 (AFB1). The mutagenic effect of AFB1 results from hepatic bioactivation to AFB1-exo-8,9-epoxide. This is in part catalysed by CYP3A5, an enzyme expressed polymorphically. We investigated the role of CYP3A5 polymorphisms in the formation of AFB1-exo-8,9-epoxide in The Gambia, a population exposed to high aflatoxin levels.

METHODS

Common CYP3A5 polymorphisms were identified in an African-American population. Subsequently, 288 Gambian subjects were genotyped and CYP3A5 activity predicted using haplotypes of the three variant loci (CYP3A5*3, *6 and *7) associated with decreases in protein expression. CYP3A5 expression was then compared to aflatoxin-albumin (AF-alb) adduct, a biomarker of AFB1 bioactivation; data were also analysed in relation to expression of other aflatoxin-metabolizing enzymes.

RESULTS

CYP3A5 haplotypes reflecting high CYP3A5 protein expression were associated with increased AF-alb. Compared to individuals with predicted low expression those predicted to express CYP3A5 from one allele displayed 16.1% higher AF-alb (95% CI: -2.5, 38.2, P = 0.093) and homozygous expressers displayed 23.2% higher AF-alb levels (95% CI: -0.01, 52.0, P = 0.051). The effect of the CYP3A5 polymorphism was strongest in individuals with low CYP3A4 activity with a 70.1% increase in AF-alb (95% CI: 11.8, 158.7, P < 0.05) in high compared to low expressers. A similar effect was observed for individuals with null alleles of GSTM1, which conjugates the AFB1-exo-8,9-epoxide to reduced glutathione.

CONCLUSIONS

The CYP3A5 polymorphism is associated with increased levels of the mutagenic AFB1-exo-8,9-epoxide, particularly in individuals with low CYP3A4, and this may modulate individual risk of HCC.

Baseline plasma viral load and CD4 cell percentage predict survival in HIV-1- and HIV-2-infected women in a community-based cohort in The Gambia

OBJECTIVES

To estimate and compare the all-cause mortality rates among HIV-1-infected, HIV-2-infected, and uninfected women and to assess the predictive value of baseline plasma viral load (PVL) and CD4 cell percentage (CD4%) for mortality.

DESIGN

Cohort study.

METHODS

At presentation to antenatal clinics in The Gambia in 1993-1995, pregnant women were screened for antibodies to HIV-1 and HIV-2. Seropositive subjects and a similar number of seronegative controls were enrolled, and baseline PVL and CD4% were measured. Participants were visited regularly by field-workers until 18 months after delivery and again 4-7 years later.

RESULTS

Thirty-two of 101 women infected with HIV-1, 23 of 243 infected with HIV-2, and 9 of 468 seronegative women died during a median follow-up of 6.9 years. The mortality rate was 56 deaths per 1000 person years of observation (pyo) for HIV-1-infected, 16 deaths per 1000 pyo for HIV-2-infected, and 3.1 deaths per 1000 pyo for HIV-uninfected women. After 8 years of follow-up, >50% of HIV-1-infected women were still alive. In multivariate analysis, a 1-log increase of HIV-1 PVL was associated with a 1.8-fold higher rate of mortality (95% confidence interval [CI], 0.9-3.4). In HIV-2 infection, women with a high PVL (>10,000 copies/mL) had an 8.7-fold (95% CI, 2.8-28) higher rate of mortality than did those with a low PVL (<1000 copies/mL). A 10% decrease in CD4% was associated with higher mortality rates among HIV-1-infected (1.6-fold; 95% CI, 1.1-2.3) and HIV-2-infected (1.5-fold; 95% CI, 1.0-2.3) subjects.

DISCUSSION

Survival of HIV-1-infected women in The Gambia is similar to that in industrialized countries before the introduction of antiretroviral treatment. Survival of HIV-2-infected women is much better. However, women with high PVLs die as quickly as their HIV-1-infected counterparts.

EPI vaccines-induced antibody prevalence in 8-9 year-olds in The Gambia

OBJECTIVES

We evaluated antibody prevalence to measles, polio 1 and 3, and tetanus toxoid antibodies in 8-9 year-old children in The Gambia within the framework of the Gambia Hepatitis Intervention Study (GHIS), a large vaccine trial aimed at evaluating vaccine efficacy against hepatitis B virus (HBV) infection, chronic carriage and primary liver cancer in a high risk population. The results of the present survey were compared with a previous survey performed with the same objectives and same methodology but in different children at 3-4 years of age.

METHODS

Four clusters of 200 children each were sampled as representative of the whole country. Children would have received BCG, diphtheria-pertussis-tetanus vaccine (DPT), poliovirus vaccine (OPV), measles and yellow fever immunization. The measles haemoagglutination inhibition test (HAI) was used to detect measles antibody. Antibodies to polioviruses 1 and 3 were tested using the standard polio neutralization assay described in the EPI manual (WHO 1990). An enzyme-linked immuno-sorbent assay (ELISA) was used to measure tetanus toxoid antibodies.

RESULTS

A high proportion of children were fully vaccinated in both age groups. Measles antibody concentrations were < or =1 : 8 in 8.2% of 8-9 year-old vaccinated children. In the previous survey of 3-4 year-old children this was 11.3%. In the present survey, GMC was lower than in the 3-4 year-old children; 88% of 3-4 year-olds and 89% of 8-9 year-olds had detectable antibody levels against poliovirus type 1. Fewer children at 8-9 years of age had antibodies against poliovirus type 3 than 3-4 year-olds (78%vs. 89% P < 0.001). A significant overall lower proportion of 8-9 year-old children had detectable tetanus toxoid antibodies compared to 3-4 year-old children (87%vs. 95% P < 0.001), as well as those who received four doses of DPT (90%vs. 97% P < 0.001). Conclusions High vaccine coverage is achieved in The Gambia with EPI. With time the number of vaccinated children who are not protected against measles, poliovirus 3 and tetanus increases. Besides the maintenance of high vaccine coverage in infants and young children, booster doses of some of the EPI vaccines in adolescents should be considered.

Incidence of tuberculosis and survival after its diagnosis in patients infected with HIV-1 and HIV-2

BACKGROUND

In sub-Saharan Africa, tuberculosis (TB) is the most frequently diagnosed opportunistic infection and cause of death among HIV-infected patients. HIV-2 has been associated with less immune suppression, slower disease progression and longer survival.

OBJECTIVE

To examine whether the incidence of TB and survival after TB are associated with CD4 cell count rather than HIV type.

METHODS

Clinical and immunological data were retrospectively evaluated among an open clinic-based cohort of HIV-1- and HIV-2-infected patients to determine incidence of TB (first diagnosis > 28 days after HIV diagnosis) and subsequent mortality. Patients were grouped by CD4 cell count into those with < 200, 200-500 and > 500 x 10 cells/l.

RESULTS

Incident TB was diagnosed among 159 of 2012 patients, with 4973 person-years of observation time. In 105/159 (66.0%), the diagnosis was confirmed by direct microscopy or culture. Incidence of TB was highest in the group with < 200 x 10 cells/l (9.1/100 and 8.8/100 person-years in HIV-1 and HIV-2, respectively). Adjusted for CD4 cell count, there was no significant difference in incidence or mortality following TB between HIV-1- and HIV-2-infected patients. Mortality rate was higher in those with incident TB and HIV infection, most markedly in the group with the highest CD4 cell count (hazard ratio, 10.0; 95% confidence interval, 5.1-19.7).

CONCLUSION

Adjusted for CD4 cell count, incidence of TB was similar among HIV-1- and HIV-2-infected patients. Mortality rates after TB diagnosis were similar in both groups and high compared with those without TB.

Seasonal variation in respiratory syncytial virus epidemics in the Gambia, West Africa

Respiratory syncytial virus outbreaks tend to occur seasonally and are a major cause of childhood morbidity. In The Gambia a regular pattern of outbreaks during six consecutive annual seasons was disrupted by 2 years of irregular outbreaks, followed by another 2 years of regular seasonal outbreaks. Improved understanding of the transmission dynamics of respiratory syncytial virus is essential to design and test effective interventions.

Regional differences in HIV trends in The Gambia: results from sentinel surveillance among pregnant women

OBJECTIVE

To monitor HIV-1 and HIV-2 trends in The Gambia, West Africa.

METHODS

In 1993-1995 a nationwide survey among 29 670 pregnant women attending eight antenatal clinics estimated the seroprevalence of HIV-1 at 0.6%, and of HIV-2 at 1.1%. Five years later, sentinel surveillance in pregnant women was established, using unlinked anonymous testing in four clinics. A dried blood spot on filter paper was obtained and tested for HIV antibodies.

RESULTS

Between May 2000 and August 2001, 8054 analysable samples were collected at four sites. The prevalence of HIV-1 rose sharply in one rural area from 0.6 to 3.0% (P < 0.0001), but the increase was small and non-significant in two other rural sites and in the urban site. The prevalence of HIV-2 did not change significantly at any of the sites. The overall prevalence of HIV-1 was 1.0% [95% confidence interval (CI) 0.8-1.3%], and of HIV-2 0.8% (CI 0.6-1.0%). Site, nationality and higher age were significantly associated with HIV-1 infection, and higher parity and site were significantly associated with HIV-2 infection.

CONCLUSION

Fifteen years after the first case of HIV-1 was described in The Gambia, the epidemic is still at a low level. There is heterogeneity within the country, with one rural area experiencing a fivefold increase in 6 years. The prevalence of HIV-2 in The Gambia is stable.

BCG scar and positive tuberculin reaction associated with reduced child mortality in West Africa. A non-specific beneficial effect of BCG?

Previous studies have suggested that the bacille Calmette-Guérin (BCG) vaccine may have a non-specific beneficial effect on childhood survival in areas with high mortality. We examined whether BCG-vaccinated children with a BCG scar or a positive tuberculin reaction had better survival than children without such reactions. As part of an ongoing two-dose measles vaccine trial for which children were recruited at 6 months of age, we examined 1813 children for BCG scar at 6 months of age and 813 BCG-vaccinated children were skin-tested for delayed hypersensitivity to tuberculin, tetanus and diphtheria. We found that BCG-vaccinated children with a BCG scar had significantly lower mortality compared with BCG scar-negative children, the mortality ratio in the first 12 months of follow-up being 0.41 (0.25-0.67). BCG-vaccinated children with a positive tuberculin test had a mortality ratio of 0.45 (0.24-0.85) compared with tuberculin negative children. These results were unchanged by control for potential confounders or using different cut-off points for a tuberculin-positive response. Exclusion of dead children who had HIV antibodies did not modify the estimate (mortality rate (MR)=0.46 (0.23-0.94)). After censoring for tuberculosis (TB) exposure at home, the mortality ratios for having a scar and being tuberculin-positive were 0.46 (0.27-0.79) or 0.42 (0.21-0.84), respectively. Children positive to tetanus or diphtheria in the skin test had the same mortality as children not responding to these vaccine-related antigens. Thus, BCG scar and a positive tuberculin reaction were associated with better survival in early childhood in an area with high mortality. Since nothing similar was found for responders to diphtheria-tetanus-pertussis (DTP) vaccine, and the effect could not be explained by protection against tuberculosis, the effect of BCG vaccination could be due to non-specific immune-stimulation protecting against other infections.