Influenza and HIV: lessons from the 2009 H1N1 influenza pandemic

A targeted single mutation in influenza A virus universal epitope transforms immunogenicity and protective immunity via CD4+ T cell activation

CD4+ T cells are central to adaptive immunity. Their role in cross-protection in viral infections such as influenza and severe acute respiratory syndrome (SARS) is well documented; however, molecular rules governing T cell receptor (TCR) engagement of peptide-human leukocyte antigen (pHLA) class II are less understood. Here, we exploit an aspect of HLA class II presentation, the peptide-flanking residues (PFRs), to "tune" CD4+ T cell responses within an in vivo model system of influenza. Using a recombinant virus containing targeted substitutions at immunodominant HLA-DR1 epitopes, we demonstrate limited weight loss and improved clinical scores after heterosubtypic re-challenge. We observe enhanced protection linked to lung-derived influenza-specific CD4+ and CD8+ T cells prior to re-infection. Structural analysis of the ternary TCR:pHLA complex identifies that flanking amino acids influence side chains in the core 9-mer peptide, increasing TCR affinity. Augmentation of CD4+ T cell immunity is achievable with a single mutation, representing a strategy to enhance adaptive immunity that is decoupled from vaccine modality.

Routine Vaccination During Pregnancy Among People Living With HIV in the United States

Importance

Pregnancy represents a window of opportunity for vaccination due to established maternal and fetal benefits of vaccination. Little is known about receipt of routinely recommended vaccines in pregnancy, specifically tetanus, diphtheria, plus acellular pertussis (Tdap) and influenza, among pregnant people living with HIV (PLHIV).

Objective

To estimate prevalence of vaccination receipt among pregnant people with HIV (PLHIV) and identify demographic and clinical characteristics associated with vaccination.

Design, Setting, and Participants

This multicenter cohort study included women participating in Women's Health Study (WHS) of the Surveillance Monitoring for ART Toxicities (SMARTT) Study of the Pediatric HIV/AIDS Cohort Study. The network has been enrolling pregnant PLHIV at 22 US sites since 2007. Participants for this study enrolled between December 2017 and July 2019. Data analysis was conducted from October 2021 to March 2022.

Exposure

Data on vaccination in pregnancy were collected through medical record abstraction.

Main Outcomes and Measures

Vaccination receipt was defined as Tdap vaccination received at less than 36 weeks' gestation and influenza vaccination at any gestational age, based on current guidelines. Log-binomial and modified Poisson regression models with generalized estimating equations were fit to identify factors associated with successful receipt of (1) Tdap, (2) influenza, and (3) both vaccinations.

Results

A total of 310 pregnancies among 278 people participating in the WHS were included (mean [SD] age, 29.5 [6.1] years; 220 [71%] Black, 77 [25%] Hispanic, and 77 [25%] race and ethnicity other than Black; 64 [21%] with perinatally acquired HIV). Less than one-third of pregnancies were vaccinated as recommended (Tdap, 32.6% [95% CI, 27.4%-38.1%]; influenza, 31.6% [95% CI, 26.5%-37.1%]; both, 22.6% [95% CI, 18.0%-27.6%]). People living with perinatally acquired HIV, those who did not identify as Black, or those who were multiparous had adjusted risk ratios (aRRs) less than 1, while older PLHIV had aRRs greater than 1, but these differences did not reach statistical significance (perinatally acquired HIV: adjusted risk ratio [aRR], 0.46; 95% CI, 0.21-1.02; race other than Black: aRR, 0.53; 95% CI, 0.26-1.08; multiparous: aRR, 0.59; 95% CI, 0.35-1.00; age 24-29 years: aRR, 2.03; 95% CI, 0.92-4.48).

Conclusions and Relevance

In this diverse, multicenter cohort of pregnant PLHIV, receipt of recommended vaccinations was low. Identifying and addressing barriers to vaccination receipt is urgently needed for pregnant people with HIV.

The Hypothiocyanite and Amantadine Combination Treatment Prevents Lethal Influenza A Virus Infection in Mice

The influenza virus has a large clinical burden and is associated with significant mortality and morbidity. The development of effective drugs for the treatment or prevention of influenza is important in order to reduce its impact. Adamantanes and neuraminidase inhibitors are two classes of anti-influenza drugs in which resistance has developed; thus, there is an urgent need to explore new therapeutic options. Boosting antiviral innate immune mechanisms in the airways represents an attractive approach. Hypothiocyanite (OSCN⁻) is produced by the airway epithelium and is effective in reducing the replication of several influenza A virus strains in vitro. It remains, however, largely unexplored whether OSCN⁻ has such an antiviral effect in vivo. Here we determined the therapeutic potential of OSCN⁻, alone or in combination with amantadine (AMT), in preventing lethal influenza A virus replication in mice and in vitro. Mice intranasally infected with a lethal dose of A/Puerto Rico/8/1934 (H1N1) or A/Hong Kong/8/1968 (H3N2) were cured by the combination treatment of OSCN⁻ and AMT. Monotherapy with OSCN⁻ or AMT alone did not substantially improve survival outcomes. However, AMT+OSCN⁻ treatment significantly inhibited viral replication, and in vitro treatment inhibited viral entry and nuclear transport of different influenza A virus strains (H1N1 and H3N2) including the AMT-resistant strain A/WSN/33 (H1N1). A triple combination treatment consisting of AMT, oseltamivir, and OSCN⁻ was also tested and further inhibited in vitro viral replication of the AMT-resistant A/WSN/33 strain. These results suggest that OSCN⁻ is a promising anti-influenza treatment option when combined with other antiviral drugs.

Post-Immune Antibodies in HIV-1 Infection in the Context of Vaccine Development: A Variety of Biological Functions and Catalytic Activities

Unlike many other viruses, HIV-1 is highly variable. The structure of the viral envelope changes as the infection progresses and is one of the biggest obstacles in developing an HIV-1 vaccine. HIV-1 infection can cause the production of various natural autoantibodies, including catalytic antibodies hydrolyzing DNA, myelin basic protein, histones, HIV-integrase, HIV-reverse transcriptase, β-casein, serum albumin, and some other natural substrates. Currently, there are various directions for the development of HIV-1 vaccines: stimulation of the immune response on the mucous membranes; induction of cytotoxic T cells, which lyse infected cells and hold back HIV-infection; immunization with recombinant Env proteins or vectors encoding Env; mRNA-based vaccines and some others. However, despite many attempts to develop an HIV-1 vaccine, none have been successful. Here we review the entire spectrum of antibodies found in HIV-infected patients, including neutralizing antibodies specific to various viral epitopes, as well as antibodies formed against various autoantigens, catalytic antibodies against autoantigens, and some viral proteins. We consider various promising targets for developing a vaccine that will not produce unwanted antibodies in vaccinated patients. In addition, we review common problems in the development of a vaccine against HIV-1.

Safety and immunogenicity of CoronaVac in people living with HIV: a prospective cohort study

Background

People living with HIV might have a poor or delayed response to vaccines, mainly when CD4 cell counts are low, and data concerning COVID-19 vaccines in this population are scarce. This prospective cohort study assessed the safety and immunogenicity of the inactivated SARS-CoV-2 vaccine CoronaVac in people with HIV compared with people with no known immunosuppression.

Methods

In this prospective cohort study, adults (aged ≥18 years) living with HIV who were regularly followed up at the University of Sao Paulo HIV/AIDS outpatient clinic in Sao Paulo, Brazil, were included in the study. Eligibility for people with HIV was independent of antiretroviral use, HIV viral load, or CD4 cell count. Adults with no known immunosuppression with CoronaVac vaccination history were included as a control group. CoronaVac was given intramuscularly in a two-dose regimen, 28 days apart. Blood was collected before vaccine administration and 6 weeks after the second dose (day 69). Immunogenicity was assessed at baseline (day 0), before second vaccine (day 28), and 6 weeks after second vaccine dose (day 69) through SARS-CoV-2 IgG titre and seroconversion, neutralising antibody (NAb) positivity and percentage activity, and factor increase in IgG geometric mean titres (FI-GMT). We investigated whether HIV status and CD4 count (<500 or ≥500 cells per μL) were associated with CoronaVac immunogenicity by use of multivariable models adjusted for age and sex.

Findings

Between Feb 9, 2021, and March 4, 2021, 776 participants were recruited. Of 511 participants included, 215 (42%) were people with HIV and 296 (58%) were people with no known immunosuppression. At 6 weeks after the second vaccine dose (day 69), 185 (91%) of 204 participants with HIV and 265 (97%) of 274 participants with no known immunosuppression had seroconversion (p=0·0055). 143 (71%) of 202 participants with HIV were NAb positive compared with 229 (84%) of 274 participants with no known immunosuppression (p=0·0008). Median IgG titres were 48·7 AU/mL (IQR 26·6–88·2) in people with HIV compared with 75·2 AU/mL (50·3–112·0) in people with no known immunosuppression (p<0·0001); and median NAb activity was 46·2% (26·9–69·7) compared with 60·8% (39·8–79·9; p<0·0001). In people with HIV who had CD4 counts less than 500 cells per μL seroconversion rates, NAb positivity, and NAb activity were lower than in those with CD4 counts of at least 500 cells per μL. In multivariable models for seroconversion, NAb positivity, IgG concentration, and NAb activity after a complete two-dose regimen, adjusted for age and sex, people with HIV who had CD4 counts of at least 500 cells per μL and people with no known immunosuppression had higher immunogenicity than did people with HIV with CD4 counts less than 500 cells per μL. No serious adverse reactions were reported during the study.

Interpretation

Immunogenicity following CoronaVac in people with HIV seems strong but reduced compared with people with no known immunosuppression. Our findings highlight the need for strategies to improve vaccine immunogenicity in people with HIV.

Funding

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and B3—Bolsa de Valores do Brasil.

The syndemic burden of HIV/AIDS in Africa amidst the COVID-19 pandemic

INTRODUCTION

The human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) has long affected millions of individuals across the globe. Historically, the prevalence of this disease is particularly noted within the African continent. Before the coronavirus disease 2019 (COVID-19) pandemic, many African countries struggled to effectively manage the increasing burden associated with HIV/AIDS. There is now a need to reassess this in a COVID-19 pandemic context so that the impact of COVID-19 on HIV/AIDS healthcare within Africa can be adequately evaluated.

METHODS

Data collection was performed on the PubMed, Ovid MEDLINE and Embase bibliographical databases with a predefined search strategy. Searches were performed in blind duplicate and all articles considering COVID-19 and HIV/AIDS within African healthcare were considered.

RESULTS

The COVID-19 pandemic has severely exacerbated the many issues surrounding HIV/AIDS care within many African countries. These impacts are noticeable in medical, psychological, and socio-political contexts.

CONCLUSIONS

Before efforts are made to improve the provision of HIV/AIDS and COVID-19 care within Africa, it is important that this issue is brought to the attention of the scientific and clinical community so that the continent can receive the necessary support and aid.

Effects of human immunodeficiency virus status on symptom severity in influenza-like illness in an otherwise healthy adult outpatient cohort

The impact of HIV on influenza-like illness (ILI) has been incompletely described in the era of combination antiretroviral therapy, particularly in the post-H1N1 pandemic period. This analysis informs on ILI in an otherwise healthy, predominantly outpatient cohort of adults with HIV in the USA. From September 2010 to March 2015, this multisite observational cohort study enrolled otherwise healthy adults presenting to a participating US military medical center with ILI, a subset of whom were HIV positive. Demographics, clinical data, and self-reported symptom severity were ascertained, and enrollees completed a daily symptom diary for up to 10 days. 510 men were included in the analysis; 50 (9.8%) were HIV positive. Subjects with HIV were older and less likely to be on active duty. Rhinovirus and influenza A were the most commonly identified pathogens. Moderate–severe diarrhea (p<0.001) and fatigue (p=0.01) were more frequently reported by HIV-positive men. HIV positivity was associated with higher gastrointestinal scores, but not other measures of ILI symptom severity, after controlling for age, race, military status, and influenza season. Few were hospitalized. HIV-positive subjects had more influenza B (p=0.04) and were more likely to receive antivirals (32% vs 6%, p<0.01). Antiviral use was not significantly associated with symptom scores when accounting for potential confounders. In this predominantly outpatient cohort of adult men, HIV had minimal impact on ILI symptom severity. Despite similar illness severity, a higher percentage of subjects with HIV reported undergoing antiviral treatment for ILI, likely reflecting differences in prescribing practices.Trial registration number: NCT01021098.

Difference in HIV testing behavior by injection status, among users of illicit drugs

Human Immunodeficiency Virus (HIV) infection remains prevalent among the marginalized and drug using population in the United States. Testing for HIV is an important and cost-effective way to reduce HIV prevalence. Our objective was to determine if there is a difference in the number of HIV testing by injection status among users of illicit drugs and if a person's social network characteristics is a contributing factor. Using a cross-sectional design and negative binomial regression models, we assessed HIV testing behavior of people who use non-injected drugs (PWND) compared to people who use injected drugs (PWID). In an analytic sample of 539 participants, PWND tested for HIV 19% less compared to PWID, PR (95% CI) = 0.81 (0.66, 0.98), p = 0.03. Other contributing factors of testing were education, condomless sex, STIs, heroin use, and participant's sex network. The interaction term between PWND and emotional support in relation to HIV testing was significant, 1.33 (1.03, 1.69), p=0.03. These findings suggest HIV testing behavior differed by injection status, and this relationship may be dependent on emotional support. To exert a greater impact on the HIV epidemic, interventions and policies encouraging HIV testing in PWND, an understudied at-risk sub-population, are warranted.

Growth capability of epidemic influenza viruses in Japan since the 2009 H1N1 pandemic

The correlation of viral growth capability (n = 156) with the viral load in nasopharyngeal swabs (n = 76) was assessed. Epidemic influenza A/H1N1, A/H3N2, and B viruses showed a wide range of growth capability (10⁴-10¹¹ copies/mL) in Madin-Darby canine kidney cells. The growth was correlated with the nasopharyngeal viral load (r = 0.53). Six selected strains showed growth-dependent cell death (r = 0.96) in a growth kinetics assay. Epidemic influenza viruses exhibit a wide range of growth capability. Growth capability should be considered one of the key factors in disease prognosis.

HIV infection and COVID-19 death: a population-based cohort analysis of UK primary care data and linked national death registrations within the OpenSAFELY platform

BACKGROUND

Whether HIV infection is associated with risk of death due to COVID-19 is unclear. We aimed to investigate this association in a large-scale population-based study in England.

METHODS

We did a retrospective cohort study. Working on behalf of NHS England, we used the OpenSAFELY platform to analyse routinely collected electronic primary care data linked to national death registrations. We included all adults (aged ≥18 years) alive and in follow-up on Feb 1, 2020, and with at least 1 year of continuous registration with a general practitioner before this date. People with a primary care record for HIV infection were compared with people without HIV. The outcome was COVID-19 death, defined as the presence of International Classification of Diseases 10 codes U07.1 or U07.2 anywhere on the death certificate. Cox regression models were used to estimate the association between HIV infection and COVID-19 death; they were initially adjusted for age and sex, then we added adjustment for index of multiple deprivation and ethnicity, and then for a broad range of comorbidities. Interaction terms were added to assess effect modification by age, sex, ethnicity, comorbidities, and calendar time.

RESULTS

17 282 905 adults were included, of whom 27 480 (0·16%) had HIV recorded. People living with HIV were more likely to be male, of Black ethnicity, and from a more deprived geographical area than the general population. 14 882 COVID-19 deaths occurred during the study period, with 25 among people with HIV. People living with HIV had higher risk of COVID-19 death than those without HIV after adjusting for age and sex: hazard ratio (HR) 2·90 (95% CI 1·96-4·30; p<0·0001). The association was attenuated, but risk remained high, after adjustment for deprivation, ethnicity, smoking and obesity: adjusted HR 2·59 (95% CI 1·74-3·84; p<0·0001). There was some evidence that the association was larger among people of Black ethnicity: HR 4·31 (95% CI 2·42-7·65) versus 1·84 (1·03-3·26) in non-Black individuals (p-interaction=0·044).

INTERPRETATION

People with HIV in the UK seem to be at increased risk of COVID-19 mortality. Targeted policies should be considered to address this raised risk as the pandemic response evolves.

FUNDING

Wellcome, Royal Society, National Institute for Health Research, National Institute for Health Research Oxford Biomedical Research Centre, UK Medical Research Council, Health Data Research UK.

Coronavirus disease 2019 (COVID-19) outcomes in HIV/AIDS patients: a systematic review

OBJECTIVES

The aim of the study was to systematically review current studies reporting on clinical outcomes in people living with HIV (PLHIV) infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

METHODS

We conducted a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. A comprehensive literature search was conducted in Global Health, SCOPUS, Medline and EMBASE using pertinent key words and Medical Subject Headings (MeSH) terms relating to coronavirus disease 2019 (COVID-19) and HIV. A narrative synthesis was undertaken. Articles are summarized in relevant sections.

RESULTS

Two hundred and eighty-five articles were identified after duplicates had been removed. After screening, eight studies were analysed, totalling 70 HIV-infected patients (57 without AIDS and 13 with AIDS). Three themes were identified: (1) controlled HIV infection does not appear to result in poorer COVID-19 outcomes, (2) more data are needed to determine COVID-19 outcomes in patients with AIDS and (3) HIV-infected patients presenting with COVID-19 symptoms should be investigated for superinfections.

CONCLUSIONS

Our findings suggest that PLHIV with well-controlled disease are not at risk of poorer COVID-19 disease outcomes than the general population. It is not clear whether those with poorly controlled HIV disease and AIDS have poorer outcomes. Superimposed bacterial pneumonia may be a risk factor for more severe COVID-19 but further research is urgently needed to elucidate whether PLHIV are more at risk than the general population.

Responses to Quadrivalent Influenza Vaccine Reveal Distinct Circulating CD4+CXCR5+ T Cell Subsets in Men Living with HIV

T cell help for B cells may be perturbed in people living with HIV (PLWH), even when HIV is suppressed, as evidenced by reports of suboptimal responses to influenza vaccination. We investigated cT_FH responses to the 2017-18 inactivated quadrivalent influenza vaccine (QIV) in men living with antiretroviral therapy (ART)-suppressed HIV infection who were treated in the early or chronic phase of infection, and control subjects. Here we show that seroprotective antibody responses in serum and oral fluid correlated with cT_FH activation and were equivalent in all three groups, irrespective of when ART was started. These responses were attenuated in those reporting immunisation with influenza vaccine in the preceding three years, independent of HIV infection. Measurement of influenza-specific IgG in oral fluid was closely correlated with haemagglutination inhibition titre. T-SNE and two-dimensional analysis revealed a subset of CD4⁺CXCR3⁺CXCR5⁺ cT_FH activated at one week after vaccination. This was distinguishable from cTFH not activated by vaccination, and a rare, effector memory CD4⁺CXCR5^hiCD32^hi T cell subset. The data support the use of QIV for immunisation of PLWH, reveal distinct circulating CD4⁺CXCR5⁺ T cell subsets and demonstrate oral fluid sampling for influenza-specific IgG is an alternative to phlebotomy.

Impact of Human Immunodeficiency Virus on the Burden and Severity of Influenza Illness in Malawian Adults: A Prospective Cohort and Parallel Case-Control Study

Background

The impact of human immunodeficiency virus (HIV) infection on influenza incidence and severity in adults in sub-Saharan Africa is unclear. Seasonal influenza vaccination is recommended for HIV-infected persons in developed settings but is rarely implemented in Africa.

Methods

We conducted a prospective cohort study to compare the incidence of laboratory-confirmed influenza illness between HIV-infected and HIV-uninfected adults in Blantyre, Malawi. In a parallel case-control study, we explored risk factors for severe influenza presentation of severe (hospitalized) lower respiratory tract infection, and mild influenza (influenza-like illness [ILI]).

Results

The cohort study enrolled 608 adults, of whom 360 (59%) were HIV infected. Between April 2013 and March 2015, 24 of 229 ILI episodes (10.5%) in HIV-infected and 5 of 119 (4.2%) in HIV-uninfected adults were positive for influenza by means of polymerase chain reaction (incidence rate, 46.0 vs 14.5 per 1000 person-years; incidence rate ratio, 2.75; 95% confidence interval, 1.02-7.44; P = .03; adjusted for age, sex, household crowding, and food security). In the case-control study, influenza was identified in 56 of 518 patients (10.8%) with hospitalized lower respiratory tract infection, and 88 or 642 (13.7%) with ILI. The HIV prevalence was 69.6% and 29.6%, respectively, among influenza-positive case patients and controls. HIV was a significant risk factor for severe influenza (odds ratio, 4.98; 95% confidence interval, 2.09-11.88; P < .001; population-attributable fraction, 57%; adjusted for season, sanitation facility, and food security).

Conclusions

HIV is an important risk factor for influenza-associated ILI and severe presentation in this high-HIV prevalence African setting. Targeted influenza vaccination of HIV-infected African adults should be reevaluated, and the optimal mechanism for vaccine introduction in overstretched health systems needs to be determined.

Vaccination in the Adult Patient Infected with HIV: A Review of Vaccine Efficacy and Immunogenicity

Patients infected with HIV remain at increased risk of mortality and morbidity from diseases that are preventable with vaccines partly due to the persisting immunopathology that results in impaired responses to vaccination despite virologic suppression. Because data on clinical effectiveness in patients who are immunocompromised remain limited, undervaccination of individuals with HIV poses a major concern. Multiple societies have published recommendations on vaccination in individuals infected with HIV. Many of these recommendations are based on extrapolation of data from clinical trials that usually exclude patients with HIV, although there is a growing body of data from patients infected with HIV as well. In this review, we describe the available literature on vaccine response in the adult patient with HIV as measured by immunogenicity or vaccine efficacy.

The Impact of Influenza and Tuberculosis Interaction on Mortality Among Individuals Aged ≥15 Years Hospitalized With Severe Respiratory Illness in South Africa, 2010-2016

Background

Data on the prevalence and impact of influenza–tuberculosis coinfection on clinical outcomes from high–HIV and –tuberculosis burden settings are limited. We explored the impact of influenza and tuberculosis coinfection on mortality among hospitalized adults with lower respiratory tract infection (LRTI).

Methods

We enrolled patients aged ≥15 years admitted with physician-diagnosed LRTI or suspected tuberculosis at 2 hospitals in South Africa from 2010 to 2016. Combined nasopharyngeal and oropharyngeal swabs were tested for influenza and 8 other respiratory viruses. Tuberculosis testing of sputum included smear microscopy, culture, and/or Xpert MTB/Rif.

Results

Among 6228 enrolled individuals, 4253 (68%) were tested for both influenza and tuberculosis. Of these, the detection rate was 6% (239/4253) for influenza, 26% (1092/4253) for tuberculosis, and 77% (3113/4053) for HIV. One percent (42/4253) tested positive for both influenza and tuberculosis. On multivariable analysis, among tuberculosis-positive patients, factors independently associated with death were age group ≥65 years compared with 15–24 years (adjusted odds ratio [aOR], 3.6; 95% confidence interval [CI], 1.2–11.0) and influenza coinfection (aOR, 2.3; 95% CI, 1.02–5.2). Among influenza-positive patients, laboratory-confirmed tuberculosis was associated with an increased risk of death (aOR, 4.5; 95% CI, 1.5–13.3). Coinfection with other respiratory viruses was not associated with increased mortality in patients positive for tuberculosis (OR, 0.7; 95% CI, 0.4–1.1) or influenza (OR, 1.6; 95% CI, 0.4–5.6).

Conclusions

Tuberculosis coinfection is associated with increased mortality in individuals with influenza, and influenza coinfection is associated with increased mortality in individuals with tuberculosis. These data may inform prioritization of influenza vaccines or antivirals for tuberculosis patients and inform tuberculosis testing guidelines for patients with influenza.

Back to the Future: Lessons Learned From the 1918 Influenza Pandemic

2018 marks the 100-year anniversary of the 1918 influenza pandemic, which killed ~50 million people worldwide. The severity of this pandemic resulted from a complex interplay between viral, host, and societal factors. Here, we review the viral, genetic and immune factors that contributed to the severity of the 1918 pandemic and discuss the implications for modern pandemic preparedness. We address unresolved questions of why the 1918 influenza H1N1 virus was more virulent than other influenza pandemics and why some people survived the 1918 pandemic and others succumbed to the infection. While current studies suggest that viral factors such as haemagglutinin and polymerase gene segments most likely contributed to a potent, dysregulated pro-inflammatory cytokine storm in victims of the pandemic, a shift in case-fatality for the 1918 pandemic toward young adults was most likely associated with the host's immune status. Lack of pre-existing virus-specific and/or cross-reactive antibodies and cellular immunity in children and young adults likely contributed to the high attack rate and rapid spread of the 1918 H1N1 virus. In contrast, lower mortality rate in in the older (>30 years) adult population points toward the beneficial effects of pre-existing cross-reactive immunity. In addition to the role of humoral and cellular immunity, there is a growing body of evidence to suggest that individual genetic differences, especially involving single-nucleotide polymorphisms (SNPs), contribute to differences in the severity of influenza virus infections. Co-infections with bacterial pathogens, and possibly measles and malaria, co-morbidities, malnutrition or obesity are also known to affect the severity of influenza disease, and likely influenced 1918 H1N1 disease severity and outcomes. Additionally, we also discuss the new challenges, such as changing population demographics, antibiotic resistance and climate change, which we will face in the context of any future influenza virus pandemic. In the last decade there has been a dramatic increase in the number of severe influenza virus strains entering the human population from animal reservoirs (including highly pathogenic H7N9 and H5N1 viruses). An understanding of past influenza virus pandemics and the lessons that we have learnt from them has therefore never been more pertinent.

Possible explanations for why some countries were harder hit by the pandemic influenza virus in 2009 - a global mortality impact modeling study

BACKGROUND

A global pandemic mortality study found prominent regional mortality variations in 2009 for Influenza A(H1N1)pdm09. Our study attempts to identify factors that explain why the pandemic mortality burden was high in some countries and low in others.

METHODS

As a starting point, we identified possible risk factors worth investigating for Influenza A(H1N1)pdm09 mortality through a targeted literature search. We then used a modeling procedure (data simulations and regression models) to identify factors that could explain differences in respiratory mortality due to Influenza A(H1N1)pdm09. We ran sixteen models to produce robust results and draw conclusions. In order to assess the role of each factor in explaining differences in excess pandemic mortality, we calculated the reduction in between country variance, which can be viewed as an effect-size for each factor.

RESULTS

The literature search identified 124 publications and 48 possible risk factors, of which we were able to identify 27 factors with appropriate global datasets. The modelling procedure indicated that age structure (explaining 40% of the mean between country variance), latitude (8%), influenza A and B viruses circulating during the pandemic (3-8%), influenza A and B viruses circulating during the preceding influenza season (2-6%), air pollution (pm10; 4%) and the prevalence of other infections (HIV and TB) (4-6%) were factors that explained differences in mortality around the world. Healthcare expenditure, levels of obesity, the distribution of antivirals, and air travel did not explain global pandemic mortality differences.

CONCLUSIONS

Our study found that countries with a large proportion of young persons had higher pandemic mortality rates in 2009. The co-circulation of influenza viruses during the pandemic and the circulation of influenza viruses during the preceding season were also associated with pandemic mortality rates. We found that real time assessments of 2009 pandemic mortality risk factors (e.g. obesity) probably led to a number of false positive findings.

Mortality amongst patients with influenza-associated severe acute respiratory illness, South Africa, 2009-2013

INTRODUCTION

Data on the burden and risk groups for influenza-associated mortality from Africa are limited. We aimed to estimate the incidence and risk-factors for in-hospital influenza-associated severe acute respiratory illness (SARI) deaths.

METHODS

Hospitalised patients with SARI were enrolled prospectively in four provinces of South Africa from 2009-2013. Using polymerase chain reaction, respiratory samples were tested for ten respiratory viruses and blood for pneumococcal DNA. The incidence of influenza-associated SARI deaths was estimated at one urban hospital with a defined catchment population.

RESULTS

We enrolled 1376 patients with influenza-associated SARI and 3% (41 of 1358 with available outcome data) died. In patients with available HIV-status, the case-fatality proportion (CFP) was higher in HIV-infected (5%, 22/419) than HIV-uninfected individuals (2%, 13/620; p = 0.006). CFPs varied by age group, and generally increased with increasing age amongst individuals >5 years (p<0.001). On multivariable analysis, factors associated with death were age-group 45-64 years (odds ratio (OR) 4.0, 95% confidence interval (CI) 1.01-16.3) and ≥65 years (OR 6.5, 95%CI 1.2-34.3) compared to 1-4 year age-group who had the lowest CFP, HIV-infection (OR 2.9, 95%CI 1.1-7.8), underlying medical conditions other than HIV (OR 2.9, 95%CI 1.2-7.3) and pneumococcal co-infection (OR 4.1, 95%CI 1.5-11.2). The estimated incidence of influenza-associated SARI deaths per 100,000 population was highest in children <1 year (20.1, 95%CI 12.1-31.3) and adults aged 45-64 years (10.4, 95%CI 8.4-12.9). Adjusting for age, the rate of death was 20-fold (95%CI 15.0-27.8) higher in HIV-infected individuals than HIV-uninfected individuals.

CONCLUSION

Influenza causes substantial mortality in urban South Africa, particularly in infants aged <1 year and HIV-infected individuals. More widespread access to antiretroviral treatment and influenza vaccination may reduce this burden.

B cell function and influenza vaccine responses in healthy aging and disease

Influenza vaccination is less effective in elderly as compared to young individuals. Several studies have addressed the identification of immune biomarkers able to monitor or predict a protective humoral immune response to the vaccine. In this review, we summarize these data, with emphasis on the effects of aging on influenza vaccine-specific B cell responses in healthy individuals and patients with Type-2 Diabetes, HIV and cardiovascular diseases.

Outcomes of influenza A(H1N1)pdm09 virus infection: results from two international cohort studies

BACKGROUND

Data from prospectively planned cohort studies on risk of major clinical outcomes and prognostic factors for patients with influenza A(H1N1)pdm09 virus are limited. In 2009, in order to assess outcomes and evaluate risk factors for progression of illness, two cohort studies were initiated: FLU 002 in outpatients and FLU 003 in hospitalized patients.

METHODS AND FINDINGS

Between October 2009 and December 2012, adults with influenza-like illness (ILI) were enrolled; outpatients were followed for 14 days and inpatients for 60 days. Disease progression was defined as hospitalization and/or death for outpatients, and hospitalization for >28 days, transfer to intensive care unit (ICU) if enrolled from general ward, and/or death for inpatients. Infection was confirmed by RT-PCR. 590 FLU 002 and 392 FLU 003 patients with influenza A (H1N1)pdm09 were enrolled from 81 sites in 17 countries at 2 days (IQR 1-3) and 6 days (IQR 4-10) following ILI onset, respectively. Disease progression was experienced by 29 (1 death) outpatients (5.1%; 95% CI: 3.4-7.2%) and 80 inpatients [death (32), hospitalization >28 days (43) or ICU transfer (20)] (21.6%; 95% CI: 17.5-26.2%). Disease progression (death) for hospitalized patients was 53.1% (26.6%) and 12.8% (3.8%), respectively, for those enrolled in the ICU and general ward. In pooled analyses for both studies, predictors of disease progression were age, longer duration of symptoms at enrollment and immunosuppression. Patients hospitalized during the pandemic period had a poorer prognosis than in subsequent seasons.

CONCLUSIONS

Patients with influenza A(H1N1)pdm09, particularly when requiring hospital admission, are at high risk for disease progression, especially if they are older, immunodeficient, or admitted late in infection. These data reinforce the need for international trials of novel treatment strategies for influenza infection and serve as a reminder of the need to monitor the severity of seasonal and pandemic influenza epidemics globally.

TRIAL REGISTRATION

ClinicalTrials.gov Identifiers: FLU 002--NCT01056354, FLU 003--NCT01056185.

Community-Acquired Pneumonia in HIV-Infected Individuals

Community-acquired pneumonia continues to be an important complication of HIV infection. Rates of pneumonia decrease with the use of antiretroviral therapy but continue to be higher than in HIV uninfected individuals. Risk factors for pneumonia include low blood CD4+ count, unsuppressed plasma HIV load, smoking, injection drug use and renal impairment. Immunization against Streptococcus pneumoniae and smoking cessation can reduce this risk. It is unclear whether newly reported viral respiratory pathogens (such as the Middle East respiratory syndrome coronavirus, will be more of a problem in HIV-infected individuals than the general population.

Impaired antibody response to influenza vaccine in HIV-infected and uninfected aging women is associated with immune activation and inflammation

Background

Aging and HIV infection are independently associated with excessive immune activation and impaired immune responses to vaccines, but their relationships have not been examined.

Methods

For selecting an aging population we enrolled 28 post-menopausal women including 12 healthy volunteers and 16 HIV-infected women on antiretroviral treatment with <100 HIV RNA copies/ml. Antibody titers to trivalent influenza vaccination given during the 2011-2012 season were determined before and 4 weeks after vaccination.

Results

Seroprotective influenza antibody titers (≥1:40) were observed in 31% HIV⁺ and 58% HIV-uninfected women pre-vaccination. Following vaccination, magnitude of antibody responses and frequency of seroprotection were lower in HIV⁺ (75%) than in HIV^– (91%) women. Plasma IL-21, the signature cytokine of T follicular helper cells (Tfh), and CD4 T cell IL-21R were upregulated with seroconversion (≥4 fold increase in antibody titer). Post-vaccine antibody responses were inversely correlated with pre-vaccination plasma TNFα levels and with activated CD4 T cells, including activated peripheral (p)Tfh. Plasma TNFα levels were correlated with activated pTfh cells (r=0.48, p=0.02), and inversely with the post-vaccination levels of plasma IL-21 (r=-0.53, p=0.02). In vitro TNFα blockade improved the ability of CD4 T cells to produce IL-21 and of B cells to secrete immunoglobulins, and addition of exogenous IL-21 to cell cultures enhanced B cell function. Higher frequencies of activated and exhausted CD8 T and B cells were noted in HIV⁺ women, but these markers did not show a correlation with antibody responses.

Conclusions

In aging HIV-infected and uninfected women, activated CD4 and pTfh cells may compromise influenza vaccine-induced antibody response, for which a mechanism of TNFα-mediated impairment of pTfh-induced IL-21 secretion is postulated. Interventions aimed at reducing chronic inflammation and immune activation in aging, HIV-infected patients may improve their response to vaccines.

Safety and immunogenicity of 2009 pH1N1 vaccination in HIV-infected pregnant women

BACKGROUND

Pregnant women infected with human immunodeficiency virus (HIV) may have particular vulnerability to 2009 pandemic H1N1 influenza (pH1N1) infection. The safety and immunogenicity of pH1N1 vaccination in HIV-infected pregnant women are unknown.

METHODS

HIV-infected women 18-39 years of age and 14-34 weeks' gestation on antiretroviral therapy received two 30-μg doses of unadjuvanted, inactivated pH1N1 vaccine 21 days apart. Hemagglutination inhibition titers were measured at entry, 21 days after dose 1, and 10 and 21 days after dose 2, and, in mothers and infants, at delivery and 3 and 6 months postdelivery.

RESULTS

No severe vaccine-related adverse events were observed among 127 subjects. At entry, 21% had seroprotective (≥1:40) titers. Seroprotection and seroresponse (≥4-fold rise) occurred in 73% and 66% after dose 1 and 80% and 72% after dose 2, respectively. Of women lacking seroprotection at entry, 66% attained seroprotection after dose 1 and 75% after dose 2. Seroprotective titers were present in 67% of mothers and 65% of infants at delivery (median 66 days after dose 2), 60% of mothers and 26% of infants at 3 months postdelivery, and 59% of mothers and 12% of infants at 6 months postdelivery.

CONCLUSIONS

Two 30-μg doses were moderately immunogenic in HIV-infected pregnant women. No concerning vaccine-related safety signals were observed. Seroprotection persisted in most women postpartum. Efficient transplacental antibody transfer occurred, but seroprotection in infants waned rapidly. Vaccination to protect HIV-infected pregnant women and their newborns from new influenza strains is feasible, but more immunogenic platforms should be evaluated. Clinical Trials Registration. NCT00992017.

Cellular and humoral immune responses to pandemic influenza vaccine in healthy and in highly active antiretroviral therapy-treated HIV patients

Influenza vaccination is recommended for HAART-treated HIV patients to prevent influenza illness and complications. Due to the known ability of T cells to mediate a broadly cross-reactive response, vaccination effectiveness in cell-mediated immune (CMI) response induction is a main objective in new influenza vaccination strategies. Nevertheless, data on CMI responses after pandemic vaccination in HIV subjects are still missing. In the present study, the ability of a single dose of adjuvanted pandemic influenza vaccine to induce humoral and CMI responses was compared in HAART-treated HIV patients and in healthcare workers. Healthcare workers (HCW, n=65) and HAART-treated HIV patients (HIV, n=67) receiving pandemic vaccination were enrolled and analyzed before (t0) and after (t1) vaccination. The analysis of strain-specific humoral response was performed by HAI assay; CMI against pandemic (A/H1N1/Cal/09) and seasonal (A/H1N1/Brisb/07 and A/H3N2/Brisb/07) strains was analyzed by ELISpot and intracellular staining followed by flow cytometry. Pandemic vaccination was effective in inducing both humoral and cell-mediated responses in HAART-treated HIV patients as well as in HCWs. A large fraction of both HCWs and HIV-infected patients showed a T cell response to the pandemic strain before vaccination, suggesting possible previous exposure to A/H1N1/pdm/09 and/or cross-reactive T cells. Notably, pandemic vaccine was also able to boost cross-reactive immune responses to seasonal strains. Finally, a weaker boost of both strain-specific and cross-reactive T cell immunity was found in individuals showing a higher baseline response. These data show the effectiveness of adjuvanted pandemic vaccine to induce both humoral and cellular (strain-specific and cross-reactive) immune responses in HIV patients similar to HCWs.

Updating our understanding of pulmonary disease associated with HIV infection

The introduction of highly active antiretroviral therapy (HAART) has resulted in a reduction of opportunistic infections associated with cellular and humoral immunosuppression. However, what is still unclear is the impact of HAART on the development of other diseases not associated with AIDS, such as lung cancer and COPD. The aim of this paper is to review the most innovative and relevant aspects of lung pathology in patients infected with HIV.