Stephen B. Gordon

Bacterial Meningitis in Malawian Adults: Pneumococcal Disease is Common, Severe, and Seasonal

We prospectively collected laboratory details and outcome data on all patients with laboratory-confirmed cases of meningitis that presented to our unit in Blantyre, Malawi, from 1 April 1998 through 31 March 1999. There were 502 patients with cases of meningitis; the most common causative organisms were Cryptococcus neoformans and Streptococcus pneumoniae. This pattern probably reflects the local human immunodeficiency virus (HIV) seroprevalence (31%) and is different from the pattern in 1974, when Neisseria meningitidis was the most common isolate. There has been an 8-fold increase in the number of meningitis cases per year since 1974, and a doubling of the percentage of medical admissions due to meningitis. The inpatient mortality rate among patients with cases of pneumococcal meningitis was 61%, and in the group as a whole was 41%. Despite the HIV-related pattern of infecting pathogens among these cases of meningitis and the increased incidence of the condition, there was evidence that the typical seasonal pattern of pneumococcal meningitis, which peaks in the cold, dry season, was preserved.

A cleaner burning biomass-fuelled cookstove intervention to prevent pneumonia in children under 5 years old in rural Malawi (the Cooking and Pneumonia Study): a cluster randomised controlled trial

Summary Background WHO estimates exposure to air pollution from cooking with solid fuels is associated with over 4 million premature deaths worldwide every year including half a million children under the age of 5 years from pneumonia. We hypothesised that replacing open fires with cleaner burning biomass-fuelled cookstoves would reduce pneumonia incidence in young children. Methods We did a community-level open cluster randomised controlled trial to compare the effects of a cleaner burning biomass-fuelled cookstove intervention to continuation of open fire cooking on pneumonia in children living in two rural districts, Chikhwawa and Karonga, of Malawi. Clusters were randomly allocated to intervention and control groups using a computer-generated randomisation schedule with stratification by site, distance from health centre, and size of cluster. Within clusters, households with a child under the age of 4·5 years were eligible. Intervention households received two biomass-fuelled cookstoves and a solar panel. The primary outcome was WHO Integrated Management of Childhood Illness (IMCI)-defined pneumonia episodes in children under 5 years of age. Efficacy and safety analyses were by intention to treat. The trial is registered with ISRCTN, number ISRCTN59448623. Findings We enrolled 10 750 children from 8626 households across 150 clusters between Dec 9, 2013, and Feb 28, 2016. 10 543 children from 8470 households contributed 15 991 child-years of follow-up data to the intention-to-treat analysis. The IMCI pneumonia incidence rate in the intervention group was 15·76 (95% CI 14·89–16·63) per 100 child-years and in the control group 15·58 (95% CI 14·72–16·45) per 100 child-years, with an intervention versus control incidence rate ratio (IRR) of 1·01 (95% CI 0·91–1·13; p=0·80). Cooking-related serious adverse events (burns) were seen in 19 children; nine in the intervention and ten (one death) in the control group (IRR 0·91 [95% CI 0·37–2·23]; p=0·83). Interpretation We found no evidence that an intervention comprising cleaner burning biomass-fuelled cookstoves reduced the risk of pneumonia in young children in rural Malawi. Effective strategies to reduce the adverse health effects of household air pollution are needed. Funding Medical Research Council, UK Department for International Development, and Wellcome Trust.

Opsonic Phagocytosis of Streptococcus pneumoniae by Alveolar Macrophages Is Not Impaired in Human Immunodeficiency Virus–Infected Malawian Adults

Streptococcus pneumoniae is a major cause of pneumonia, bacteremia, and meningitis, especially among adults infected with the human immunodeficiency virus (HIV). Alveolar macrophages (AMs) are critical components of cellular defense against bacterial infection and are both infected and affected by HIV. In this study, AMs obtained at bronchoscopy from 44 Malawian adults (24 HIV positive and 20 HIV negative) were exposed in vitro to opsonized S. pneumoniae and coagulase-negative staphylococci. AMs from HIV-positive and -negative volunteers showed no significant difference in binding to or internalization of either S. pneumoniae or coagulase-negative staphylococci. In HIV-positive subjects, the presence of detectable HIV in lung fluid was not associated with AM impairment. AMs from HIV-infected adults did not exhibit impaired pneumococcal phagocytosis in the assay used. This suggests that an alternative mechanism of susceptibility is operating in these individuals.

Pulmonary Immunoglobulin Responses to Streptococcus pneumoniae Are Altered but Not Reduced in Human Immunodeficiency Virus–Infected Malawian Adults

We tested the hypothesis that human immunodeficiency virus (HIV)-infected adults have a specific defect in anti-pneumococcal capsular polysaccharide (Pn-specific) immunoglobulin (Ig) in fluid obtained from the lower respiratory tract. Higher levels of total IgG and IgM were present in bronchoalveolar lavage samples from HIV-infected subjects than in those from HIV-uninfected subjects. Pn-specific IgG and IgM in bronchoalveolar lavage samples were not significantly different between HIV-infected and -uninfected subjects. After pneumococcal infection, HIV-infected patients had higher bronchoalveolar lavage levels of Pn-specific IgG than HIV-infected patients without recent infection (geometric means, 387 vs. 30 ng/mL, P=.001).

The alveolar microenvironment of patients infected with human immunodeficiency virus does not modify alveolar macrophage interactions with Streptococcus pneumoniae.

ABSTRACT We tested the hypothesis that HIV infection results in activation of alveolar macrophages and that this might be associated with impaired defense against pneumococcus. We compared alveolar macrophages and lymphocytes in 131 bronchoalveolar lavage samples from HIV-infected and healthy controls using inflammatory gene microarrays, flow cytometry, real-time PCR, and enzyme-linked immunosorbent assay (ELISA) to determine the pattern of macrophage activation associated with HIV infection and the effect of this activation on defense against pneumococcus. We used gamma interferon (IFN-γ) priming to mimic the cellular milieu in HIV-infected lungs. InnateDB and BioLayout 3D were used to analyze the interactions of the upregulated genes. Alveolar macrophages from HIV-infected adults showed increased gene expression and cytokine production in a classical pattern. Bronchoalveolar lavage from HIV-infected subjects showed excess CD8+ lymphocytes with activated phenotype. Toll-like receptor 4 (TLR4) expression was increased in macrophages from HIV-infected subjects, but function was similar between the groups; lung lavage fluid did not inhibit TLR function in transfected HeLa cells. Alveolar macrophages from HIV-infected subjects showed normal binding and internalization of opsonized pneumococci, with or without IFN-γ priming. Alveolar macrophages from HIV-infected subjects showed classical activation compared to that of healthy controls, but this does not alter macrophage interactions with pneumococci.

HIV-1 Infection Is Associated with Altered Innate Pulmonary Immunity

We obtained bronchoalveolar lavage (BAL) fluid from 45 Malawian adults, to measure the concentrations of innate pulmonary immune factors that are important in lung defense against infection. Increased concentrations of the beta -chemokine RANTES were found in BAL fluid from the human immunodeficiency virus (HIV)-1-infected subjects, compared with those in BAL fluid from the HIV-1-uninfected control subjects (mean, 86 pg/mL vs. 0 pg/mL; P<.001). Lysozyme concentrations were also elevated in the HIV-1-infected subjects, compared with those in the HIV-1-uninfected control subjects (1.9 mu g/mL vs. 1.1 mu g/mL; P=.03), but were not elevated in the HIV-1-infected subjects who had recently recovered from invasive pneumococcal disease. Concentrations of lactoferrin and secretory leukocyte protease inhibitor (SLPI) were not different when the subjects were compared by HIV-1 serostatus. Concentrations of RANTES (R2=0.68 and P<.0001) and SLPI (R2=0.29 and P=.001) correlated with BAL fluid HIV-1 load but not with plasma HIV-1 load.

A framework for Controlled Human Infection Model (CHIM) studies in Malawi: Report of a Wellcome Trust workshop on CHIM in Low Income Countries held in Blantyre, Malawi.

Controlled human infection model (CHIM) studies have pivotal importance in vaccine development, being useful for proof of concept, pathogenesis, down-selection and immunogenicity studies. To date, however, they have seldom been carried out in low and middle income countries (LMIC), which is where the greatest burden of vaccine preventable illness is found. This workshop discussed the benefits and barriers to CHIM studies in Malawi. Benefits include improved vaccine effectiveness and host country capacity development in clinical, laboratory and governance domains. Barriers include acceptability, safety and regulatory issues. The report suggests a framework by which ethical, laboratory, scientific and governance issues may be addressed by investigators considering or planning CHIM in LMIC.

HIV infected adults do not have an excess of colonising bacteria in their large airways

BackgroundHIV infected adults have increased susceptibility to bacterial pneumonia but the underlying immune defect is poorly understood. We tested the hypothesis that HIV infection might be associated with increased bacterial colonisation of distal airways by nasal flora, which would then predispose patients to bacterial pneumonia.MethodsHealthy volunteer adults with normal chest radiographs were recruited. Bronchoscopy was carried out and uncontaminated mucosal samples were collected from proximal and distal sites in the large airways using a protected specimen brush. Samples were cultured to detect typical respiratory tract colonising organisms, and the proportion of samples found to contain colonising bacteria compared between HIV infected and uninfected subjects using non-parametric tests.ResultsForty-nine subjects were studied of whom 27 were HIV infected. Colonising bacteria were identified in the nasopharynx of all subjects including Streptococcus pneumoniae in 6/49 subjects (5 HIV uninfected). Colonising bacteria were found in the distal airway of 6 subjects (3/27 HIV infected vs 3/22 HIV uninfected ; χ2 = 0.07, p = 0.8). Streptococcus pneumoniae was identified in the trachea of all subjects with nasal colonisation but in the distal airway of only 1 subject.ConclusionsThere was no evidence to support a hypothesis of increased airway bacterial colonisation in healthy HIV infected subjects.

Pneumococcal capsular polysaccharide immunity in the elderly

ABSTRACT Immunity to pneumococcal infections is impaired in older people, and current vaccines are poorly protective against pneumococcal disease in this population. Naturally acquired immunity to pneumococcal capsular polysaccharides develops during childhood and is robust in young adults but deteriorates with advanced age. In particular, antibody levels and function are reduced in older people. Pneumococcal vaccines are recommended for people >65 years old. However, the benefits of polysaccharide and protein-conjugated vaccines in this population are small, because of both serotype replacement and incomplete protection against vaccine serotype pneumococcal disease. In this review, we overview the immune mechanisms by which naturally acquired and vaccine-induced pneumococcal capsular polysaccharide immunity declines with age, including altered colonization dynamics, reduced opsonic activity of antibodies (particularly IgM), and impaired mucosal immunity.

Effect of Live Attenuated Influenza Vaccine on Pneumococcal Carriage

The widely used nasally-administered Live Attenuated Influenza Vaccine (LAIV) alters the dynamics of naturally occurring nasopharyngeal carriage of Streptococcus pneumoniae in animal models. Using a human experimental model (serotype 6B) we tested two hypotheses: 1) LAIV increased the density of S. pneumoniae in those already colonised; 2) LAIV administration promoted colonisation. Randomised, blinded administration of LAIV or nasal placebo either preceded bacterial inoculation or followed it, separated by a 3-day interval. The presence and density of S. pneumoniae was determined from nasal washes by bacterial culture and PCR. Overall acquisition for bacterial carriage were not altered by prior LAIV administration vs. controls (25/55 [45.5%] vs 24/62 [38.7%] respectively, p=0.46). Transient increase in acquisition was detected in LAIV recipients at day 2 (33/55 [60.0%] vs 25/62 [40.3%] in controls, p=0.03). Bacterial carriage densities were increased approximately 10-fold by day 9 in the LAIV recipients (2.82 vs 1.81 log10 titers, p=0.03). When immunisation followed bacterial acquisition (n=163), LAIV did not change area under the bacterial density-time curve (AUC) at day 14 by conventional microbiology (primary endpoint), but significantly reduced AUC to day 27 by PCR (p=0.03). These studies suggest that LAIV may transiently increase nasopharyngeal density of S. pneumoniae. Transmission effects should therefore be considered in the timing design of vaccine schedules. Trial registration The study was registered on EudraCT (2014-004634-26) Funding The study was funded by the Bill and Melinda Gates Foundation and the UK Medical Research Council.