Associations of CD4 Cell Count Measures With Infection-Related and Infection-Unrelated Cancer Risk Among People With HIV.

BACKGROUND: People with HIV are at higher risk of infection-related cancers than the general population, which could be due, in part, to immune dysfunction. Our objective was to examine associations between 4 CD4 count measures as indicators of immune function and infection-related and infection-unrelated cancer risk. SETTING: We conducted a cohort study of adults with HIV who were diagnosed with cancer in Ontario, Canada. Incident cancers were identified from January 1, 1997 to December 31, 2020. METHODS: We estimated adjusted hazard ratios (aHR) for the associations between CD4 measures (baseline CD4, nadir CD4, time-updated CD4, time-updated CD4:CD8) and cancer incidence rates using competing risk analyses, adjusted for socio-demographic factors, history of hepatitis B or C infection, baseline viral load, smoking, and alcohol use. RESULTS: Among 4771 people with HIV, contributing 59,111 person-years of observation, a total of 549 cancers were observed. Low baseline CD4 (<200 cells/µL) (aHR 2.08 [95% CI: 1.38 to 3.13], nadir (<200 cells/µL) (aHR 2.01 [95% CI: 1.49 to 2.71]), low time-updated CD4 (aHR 3.52 [95% CI: 2.36 to 5.24]) and time-updated CD4:CD8 ratio (<0.4) (aHR 2.02 [95% CI: 1.08 to 3.79]) were associated with an increased rate of infection-related cancer. No associations were observed for infection-unrelated cancers. CONCLUSIONS: Low CD4 counts and indices were associated with increased rates of infection-related cancers among people with HIV, irrespective of the CD4 measure used. Early diagnosis and linkage to care and high antiretroviral therapy uptake may lead to improved immune function and could add to cancer prevention strategies such as screening and vaccine uptake.

Trends in infection-related and infection-unrelated cancer incidence among people with and without HIV infection in Ontario, Canada, 1996-2020: a population-based matched cohort study using health administrative data.

BACKGROUND: People with HIV infection are at higher risk for certain cancers than the general population. We compared trends in infection-related and infection-unrelated cancers among people with and without HIV infection. METHODS: We conducted a retrospective population-based matched cohort study of adults with and without HIV infection using linked health administrative databases in Ontario, Canada. Participants were matched on birth year, sex, census division (rurality), neighbourhood income quintile and region of birth. We followed participants from cohort entry until the earliest of date of cancer diagnosis, date of death, Nov. 1, 2020, or date of loss to follow-up. Incident cancers identified from Jan. 1, 1996, to Nov. 1, 2020, were categorized as infection-related or-unrelated. We examined calendar periods 1996-2003, 2004-2011 and 2012-2020, corresponding to the early combination antiretroviral therapy (cART), established cART and contemporary cART eras, respectively. We used competing risk analyses to examine trends in cumulative incidence by calendar period, age and sex, and cause-specific hazard ratios (HRs). RESULTS: We matched 20 304 people with HIV infection to 20 304 people without HIV infection. A total of 2437 cancers were diagnosed, 1534 (62.9%) among infected people and 903 (37.0%) among uninfected people. The risk of infection-related cancer by age 65 years for people with HIV infection decreased from 19.0% (95% confidence interval [CI] 15.6%-22.3%) in 1996-2011 to 10.0% (95% CI 7.9%-12.1%) in 2012-2020. Compared to uninfected people, those with HIV infection had similar HRs of infection-unrelated cancer but increased rates of infection-related cancer, particularly among younger age groups (25.1 [95% CI 13.2-47.4] v. 1.9 [95% CI 1.0-3.7] for age 18-39 yr v. ≥ 70 yr); these trends were consistent when examined by sex.Interpretation: We observed significantly higher rates of infection-related, but not infection-unrelated, cancer among people with HIV infection than among uninfected people. The elevated rate of infection-related cancer in 2012-2020 highlights the importance of early and sustained antiretroviral therapy along with cancer screening and prevention measures.

HIV in MOTION: a community of practice on physical rehabilitation for and by people living with HIV and their allies.

Background: This paper describes the design, implementation, and evaluation of a community of practice (CoP), HIV in MOTION (HIM), to advance physical activity rehabilitation interventions with adults living with HIV, clinicians, researchers, and representatives from community-based organizations. We attracted a diverse audience of geographically dispersed people living with HIV, clinicians, exercise personnel, and trainees to eight HIM community of practice events that featured the clinical, research, and lived experience of people living with HIV. HIV in MOTION had (a) a domain related to physical rehabilitation, exercise, and social participation for people living with HIV; (b) a community of diverse individuals; and (c) a practice, that is, a series of sustained interactions online and offline, synchronous, and asynchronous. Our team included six diverse people living with HIV, two coordinators, and three academic researchers who planned, prepared, implemented, and evaluated each online session. To evaluate the HIV in MOTION CoP, we employed an evaluation framework composed of five criteria: Goals and Scope, Context and Structure, Process and Activities, Outcomes, and Impact. We collected quantitative and qualitative evaluative data using online evaluation, audiovisual archiving, and participant observations during the debriefing with all members of our team. Results: We widened the Goals and Scope of the HIV in MOTION CoP to include the HIV narrative of lived experiences, including autopathography, and participant storytelling. In matters of Context and Structure, we received explicit satisfaction with our governance and leadership. Also, being flexible to fit online formats was a productive strategy that made the HIV in MOTION CoP sessions agile and amenable to audiovisual archiving. Our indicators of success in Process, Activities, and Outcomes included participant retention online, elicited verbal interventions and comments in the chat room, and a rate of three repeat visits online. The indicators of success of Impact were the presence of voluntary and unscripted autopathography, the patient storytelling and how it reportedly caused changes in the participants, and the "legitimate peripheral participation" of emerging research and clinical students. In conclusion, we recommend our form of CoP for mixing the knowledge of diverse persons in this area. However, we recommend considering budget and burnout as serious challenges to sustainability.

Global Prevalence of Chronic Pain in Women with HIV: A Systematic Review and Meta-analysis.

Chronic pain is common among people with human immunodeficiency virus (HIV) and detrimental to quality of life and overall health. It is often underdiagnosed, undertreated, and frankly dismissed in women with HIV, despite growing evidence that it is highly prevalent in this population. Thus, we conducted a systematic review and meta-analysis to estimate the global prevalence of chronic pain in women with HIV. The full protocol can be found on PROSPERO (identifier CRD42022301145). Of the 2984 references identified in our search, 36 were included in the systematic review and 35 in the meta-analysis. The prevalence of chronic pain was 31.2% (95% confidence interval [CI], 24.6%-38.7%; I2 = 98% [95% CI, 97%-99%]; P < .0001). In this global assessment, we found a high prevalence of chronic pain among women with HIV, underscoring the importance of understanding the etiology of chronic pain, identifying effective treatments, and conducting regular assessments in clinical practice.

Role of fatty liver in the epidemic of advanced chronic liver disease among people with HIV: protocol for the Canadian LIVEHIV multicentre prospective cohort.

INTRODUCTION: Advanced chronic liver disease (ACLD) is a major cause of death for people with HIV (PWH). While viral hepatitis coinfections are largely responsible for this trend, metabolic dysfunction-associated steatotic liver disease (MASLD) is an emerging concern for PWH. We aimed to assess the contribution of MASLD to incident ACLD in PWH. METHODS AND ANALYSIS: This multicentre prospective observational cohort study will enrol 968 consecutive HIV monoinfected patients from four Canadian sites, excluding subjects with alcohol abuse, liver disease other than MASLD, or ACLD at baseline. Participants will be followed annually for 4 years by clinical evaluation, questionnaires, laboratory testing and Fibroscan to measure liver stiffness measurement (LSM) and controlled attenuation parameter (CAP). The primary outcome will be incidence of ACLD, defined as LSM>10 kPa, by MASLD status, defined as CAP≥285 dB/m with at least one metabolic abnormality, and to develop a score to classify PWH according to their risk of ACLD. Secondary outcomes will include health-related quality of life (HRQoL) and healthcare resource usage. Kaplan-Meier survival method and Cox proportional hazards regression will calculate the incidence and predictors of ACLD, respectively. Propensity score methods and marginal structural models will account for time-varying exposures. We will split the cohort into a training set (to develop the risk score) and a validation set (for validation of the score). HRQoL scores and healthcare resource usage will be compared by MASLD status using generalised linear mixed effects model. ETHICS AND DISSEMINATION: This protocol has been approved by the ethics committees of all participating institutions. Written informed consent will be obtained from all study participants. The results of this study will be shared through scientific publications and public presentations to advocate for the inclusion of PWH in clinical trials of MASLD-targeted therapies and case-finding of ACLD in PWH.

Piloting an online telecoaching community-based exercise intervention with adults living with HIV: protocol for a mixed-methods implementation science study.

INTRODUCTION: Our aim is to evaluate the implementation of an online telecoaching community-based exercise (CBE) intervention with the goal of reducing disability and enhancing physical activity and health among adults living with HIV. METHODS AND ANALYSIS: We will conduct a prospective longitudinal mixed-methods two-phased intervention study to pilot the implementation of an online CBE intervention with ~30 adults (≥18 years) living with HIV who consider themselves safe to participate in exercise. In the intervention phase (0-6 months), participants will take part in an online CBE intervention involving thrice weekly exercise (aerobic, resistance, balance and flexibility), with supervised biweekly personal training sessions with a fitness instructor, YMCA membership providing access to online exercise classes, wireless physical activity monitor to track physical activity and monthly online educational sessions on topics related to HIV, physical activity and health. In the follow-up phase (6-12 months), participants will be encouraged to continue independent exercise thrice weekly. Quantitative assessment: Bimonthly, we will assess cardiopulmonary fitness, strength, weight, body composition and flexibility, followed by administering self-reported questionnaires to assess disability, contextual factor outcomes (mastery, engagement in care, stigma, social support), implementation factors (cost, feasibility, technology), health status and self-reported physical activity. We will conduct a segmented regression analyses to describe the change in level and trend between the intervention and follow-up phases. Qualitative assessment: We will conduct online interviews with a subsample of ~10 participants and 5 CBE stakeholders at baseline (month 0), postintervention (month 6) and end of follow-up (month 12) to explore experiences, impact and implementation factors for online CBE. Interviews will be audiorecorded and analysed using content analytical techniques. ETHICS AND DISSEMINATION: Protocol approved by the University of Toronto Research Ethics Board (Protocol # 40410). Knowledge translation will occur in the form of presentations and publications in open-access peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT05006391.

The burden of cancer among people living with HIV in Ontario, Canada, 1997-2020: a retrospective population-based cohort study using administrative health data.

BACKGROUND: With combination antiretroviral therapy (ART) and increased longevity, cancer is a leading cause of morbidity among people with HIV. We characterized trends in cancer burden among people with HIV in Ontario, Canada, between 1997 and 2020. METHODS: We conducted a population-based, retrospective cohort study of adults with HIV using linked administrative health databases from Jan. 1, 1997, to Nov. 1, 2020. We grouped cancers as infection-related AIDS-defining cancers (ADCs), infection-related non-ADCs (NADCs) and infection-unrelated cancers. We calculated age-standardized incidence rates per 100 000 person-years with 95% confidence intervals (CIs) using direct standardization, stratified by calendar period and sex. We also calculated limited-duration prevalence. RESULTS: Among 19 403 adults living with HIV (79% males), 1275 incident cancers were diagnosed. From 1997-2000 to 2016- 2020, we saw a decrease in the incidence of all cancers (1113.9 [95% CI 657.7-1765.6] to 683.5 [95% CI 613.4-759.4] per 100 000 person-years), ADCs (403.1 [95% CI 194.2-739.0] to 103.8 [95% CI 79.2-133.6] per 100 000 person-years) and infection-related NADCs (196.6 [95% CI 37.9-591.9] to 121.9 [95% CI 94.3-154.9] per 100 000 person-years). The incidence of infection-unrelated cancers was stable at 451.0 per 100 000 person-years (95% CI 410.3-494.7). The incidence of cancer among females increased over time but was similar to that of males in 2016-2020. INTERPRETATION: Over a 24-year period, the incidence of cancer decreased overall, largely driven by a considerable decrease in the incidence of ADC, whereas the incidence of infection-unrelated cancer remained unchanged and contributed to the greatest burden of cancer. These findings could reflect combination ART-mediated changes in infectious comorbidity and increased life expectancy; targeted cancer screening and prevention strategies are needed.

Examining the association between stress and antiretroviral therapy adherence among women living with HIV in Toronto, Ontario.

BACKGROUND: We aimed to identify the association between stress and antiretroviral therapy (ART) adherence among women in HIV care in Toronto, Ontario participating in the Ontario HIV Treatment Network Cohort Study (OCS) between 2007 and 2012. MATERIALS AND METHODS: We conducted cross-sectional analyses with women on ART completing the AIDS Clinical Trial Group (ACTG) Adherence Questionnaire. Data closest to, or at the last completed interview, were collected from medical charts, through record linkage with Public Health Ontario Laboratories, and from a standardized self-reported questionnaire comprised of socio-demographic and psycho-socio-behavioral measures (Center for Epidemiologic Studies Depression Scale (CES-D), Alcohol Use Disorders Identification Test (AUDIT)), and stress measures (National Population Health Survey). Logistic regression was used to quantify associations with optimal adherence (≥95% adherence defined as missing ≤ one dose of ART in the past 4 weeks). RESULTS: Among 307 women, 65.5% had optimal adherence. Women with suboptimal compared to optimal adherence had higher median total stress scores (6.0 [interquartile range (IQR): 3.0-8.1] vs. 4.1 [IQR: 2.0-7.1], p = 0.001), CES-D scores (16 [IQR: 6-28] vs. 12 [IQR: 3-22], p = 0.008) and reports of hazardous and harmful alcohol use (31.1% vs. 17.9%, p = 0.008). In our multivariable model, we found an increased likelihood of optimal adherence with the absence of hazardous and harmful alcohol use (Adjusted Odds Ratio (AOR)=2.20, 95% confidence interval (CI): 1.12-4.32) and a decreased likelihood of optimal adherence with more self-reported stress (AOR = 0.56, 95% CI: 0.33-0.94). CONCLUSIONS: Interventions supporting optimal ART adherence should address stress and include strategies to reduce or eliminate hazardous and harmful alcohol use for women living with HIV.

Development of a non-radiolabeled glucosyltransferase activity assay for C. difficile toxin A and B using ultra performance liquid chromatography.

Clostridium difficile infection (CDI) is the leading cause of gastroenteritis-associated death in the United States. The major virulent factors of C. difficile are toxin A (TcdA) and toxin B (TcdB). Toxicity is mediated by the glucosyltransferase domains on TcdA and TcdB wherein a glucose is transferred from UDP-glucose to Ras homolog family member A (RhoA) receptor. This modification results in disruption of critical cell signaling events. Vaccination against these toxins is considered the best way to combat the CDI. In order to produce non-toxic TcdA and TcdB antigens, their glucosyltransferase domains were genetically mutated to inactivate the toxin activity. We have developed a reverse phase ultra performance liquid chromatographic (RP-UPLC) method to measure this glucosyltransferase activity by separating RhoA and glucosylated RhoA. Glucosylated RhoA and RhoA have a retention time (RT) of 31.25 and 31.95min. We determine for the first time the glucosyltransferase kinetics (Km and kcat) of both full length TcdA and TcdB to RhoA and demonstrate that the genetically mutated TcdA and TcdB show no glucosyltransferase activity. Furthermore, two-dimensional electron microscopy (2D EM) data demonstrates that the overall global structures of mutated toxins do not change compared to native toxins.

Soluble Human Cytomegalovirus gH/gL/pUL128-131 Pentameric Complex, but Not gH/gL, Inhibits Viral Entry to Epithelial Cells and Presents Dominant Native Neutralizing Epitopes.

Congenital infection of human cytomegalovirus (HCMV) is one of the leading causes of nongenetic birth defects, and development of a prophylactic vaccine against HCMV is of high priority for public health. The gH/gL/pUL128-131 pentameric complex mediates HCMV entry into endothelial and epithelial cells, and it is a major target for neutralizing antibody responses. To better understand the mechanism by which antibodies interact with the epitopes of the gH/gL/pUL128-131 pentameric complex resulting in viral neutralization, we expressed and purified soluble gH/gL/pUL128-131 pentameric complex and gH/gL from Chinese hamster ovary cells to >95% purity. The soluble gH/gL, which exists predominantly as (gH/gL)2 homodimer with a molecular mass of 220 kDa in solution, has a stoichiometry of 1:1 and a pI of 6.0-6.5. The pentameric complex has a molecular mass of 160 kDa, a stoichiometry of 1:1:1:1:1, and a pI of 7.4-8.1. The soluble pentameric complex, but not gH/gL, adsorbs 76% of neutralizing activities in HCMV human hyperimmune globulin, consistent with earlier reports that the most potent neutralizing epitopes for blocking epithelial infection are unique to the pentameric complex. Functionally, the soluble pentameric complex, but not gH/gL, blocks viral entry to epithelial cells in culture. Our results highlight the importance of the gH/gL/pUL128-131 pentameric complex in HCMV vaccine design and emphasize the necessity to monitor the integrity of the pentameric complex during the vaccine manufacturing process.

Development and optimization of a high-throughput assay to measure neutralizing antibodies against Clostridium difficile binary toxin.

Clostridium difficile strains producing binary toxin, in addition to toxin A (TcdA) and toxin B (TcdB), have been associated with more severe disease and increased recurrence of C. difficile infection in recent outbreaks. Binary toxin comprises two subunits (CDTa and CDTb) and catalyzes the ADP-ribosylation of globular actin (G-actin), which leads to the depolymerization of filamentous actin (F-actin) filaments. A robust assay is highly desirable for detecting the cytotoxic effect of the toxin and the presence of neutralizing antibodies in animal and human sera to evaluate vaccine efficacy. We describe here the optimization, using design-of-experiment (DOE) methodology, of a high-throughput assay to measure the toxin potency and neutralizing antibodies (NAb) against binary toxin. Vero cells were chosen from a panel of cells screened for sensitivity and specificity. We have successfully optimized the CDTa-to-CDTb molar ratio, toxin concentration, cell-seeding density, and sera-toxin preincubation time in the NAb assay using DOE methodology. This assay is robust, produces linear results across serial dilutions of hyperimmune serum, and can be used to quantify neutralizing antibodies in sera from hamsters and monkeys immunized with C. difficile binary toxin-containing vaccines. The assay will be useful for C. difficile diagnosis, for epidemiology studies, and for selecting and optimizing vaccine candidates.

Social determinants of health associated with hepatitis C co-infection among people living with HIV: results from the Positive Spaces, Healthy Places study.

BACKGROUND: Social determinants of health (SDOH) may influence the probability of people living with HIV also being infected with hepatitis C virus (HCV). We compared the SDOH of adults co-infected with HCV/HIV with that of HIV mono-infected adults to identify factors independently associated with HCV infection. METHODS: In this cross-sectional study, face-to-face interviews were conducted with 509 HIV-infected adults affiliated with or receiving services from community-based AIDS service organizations (CBAOs). The primary outcome measure was self-reported HCV infection status. Chi-square, Student's t tests, and Wilcoxon rank-sum tests were performed to compare SDOH of HCV/HIV co-infected participants with that of HIV mono-infected participants. Multivariable hierarchical logistic regression was used to identify factors independently associated with HCV co-infection. RESULTS: Data on 482 (95 HCV/HIV co-infected and 387 HIV mono-infected) adults were analyzed. Compared with participants infected with HIV only, those who were co-infected with HIV and HCV were more likely to be heterosexual, Aboriginal, less educated and unemployed. They were more likely to have a low income, to not be receiving antiretroviral treatment, to live outside the Greater Toronto Area (GTA), to use/abuse substances, experience significant depression, and utilize addiction counselling and needle-exchange services. They also were more likely to report a history of homelessness and perceived housing-related discrimination and to have moved twice or more in the previous 12 months. Factors independently associated with HCV/HIV co-infection were history of incarceration (odds ratio [OR] 8.81, 95% CI 4.43-17.54), history of homelessness (OR 3.15, 95% CI 1.59-6.26), living outside of the GTA (OR 3.13, 95% CI 1.59-6.15), and using/abusing substances in the past 12 months (OR 2.05, 95% CI 1.07-3.91). CONCLUSION: Differences in SDOH exist between HIV/HCV co-infected and HIV mono-infected adults. History of incarceration, history of homelessness, substance use, and living outside the GTA were independently associated with HCV/HIV co-infection. Interventions that reduce homelessness and incarceration may help prevent HCV infection in people living with HIV.

Contribution of variable domains to the stability of humanized IgG1 monoclonal antibodies.

Temperature-induced unfolding of three humanized IgG1 monoclonal antibodies and their Fab and Fc fragments was monitored by differential scanning calorimetry at neutral pH. With some exceptions, the thermogram of the intact antibody presents two peaks and the transition with the larger experimental enthalpy contains the contribution from the Fab fragments. Although the measured enthalpy was similar for all three Fab fragments studied, the apparent melting temperatures were found to vary significantly, even for Fab fragments originating from the same human germline. Therefore, we propose to use the measured enthalpy of unfolding as the key parameter to recognize the unfolding events in the melting profile of an intact IgG1 antibody. If the variable domain sequences, resulting from complementarity determining regions (CDRs) grafting and humanization, destabilize the Fab fragment with respect to the CH3 domain, the first transition represents the unfolding of the Fab fragment and the CH2 domain, while the second transition represents CH3 domain unfolding. Otherwise, the first transition represents CH2 domain unfolding, and the second transition represents the unfolding of the Fab fragment and the CH3 domain. In some cases, the DSC profile may present three transitions, with the Fab unfolding occurring at distinct temperatures compared to the melting of the CH2 and CH3 domains. If the DSC profile of a humanized IgG1 monoclonal antibody cannot be described by the model above, the result may be an indication of significant structural heterogeneity and/or of disruption of the Fab cooperative unfolding. Low stability or heterogeneity of the Fab fragment may prove problematic for long-term storage or consistency of production. Therefore, understanding the features of a DSC profile is important for clone selection and process maturation in the early stages of development of therapeutic monoclonal antibodies.

An automated microscale chromatographic purification of virus-like particles as a strategy for process development.

The development of fermentation processes for recombinant vaccines requires optimizing expression while maintaining high product quality. Changes to cell fermentation conditions are typically evaluated following cell disruption, with expression levels quantified by immunoassay, liquid chromatography or enzyme activity. However, assay titres do not always predict the effects that intracellular aggregation, proteolysis, post-translational modifications and differences in relative impurity levels can have on purification yield and product purity. Furthermore, heterogeneity in the size and surface properties inherent in viral particles makes unit operations such as chromatography less predictable. In these cases, the purification procedure (or a mimic thereof) must be carried out to give accurate information on the impact of changes in fermentation conditions on purification process performance. This was demonstrated for the development of a recombinant vaccine against human papillomavirus produced in Saccharomyces cerevisiae, where the most informative feedback on fermentation variables was obtained by completing a multistep chromatographic purification to evaluate process yield and product purity. To increase the purification throughput and reduce labour, the chromatography was miniaturized 1000-fold from the laboratory scale using microlitre volumes of adsorbent in a pipette tip and automated on a robotic workstation. The microscale purification is shown to be predictive of the laboratory-scale purification in terms of yield and purity, while providing over a 10-fold increase in throughput and allowing for increased monitoring of fermentation processes. In addition, by reducing the volume of cells needed for this assessment, the fermentation can be correspondingly reduced in scale and carried out in parallel for additional throughput gains.

A reversed phase HPLC assay for the simultaneous quantitation of non-ionic and ionic surfactants in bioprocess intermediates.

This report describes a rapid and accurate reversed phase HPLC method for the simultaneous quantitation of multiple surfactants in various bioprocess solution matrices including cell lysates. Separation and quantitation of a mixture of the cationic detergent domiphen bromide from the non-ionic detergent Triton X-100 in crude cell mixtures can be achieved within 15 min using a TSK-gel C18-NPR reversed phase column and an aqueous mobile phase gradient of acetonitrile:water with the reagent PIC-B8 as ion-pairing modifier. The linear dynamic range for quantitation of domiphen bromide (DB) and Triton in this assay extends from 20 to 2000 microM. Linear regression analyses from the standard curve determinations showed an R2 of > or = 0.990. The assay does not show any interferences from proteins or other cellular contaminants such as nucleic acids. The assay has been used to evaluate clearance of these compounds throughout the purification process of an adenovirus-based vaccine candidate, as well as to determine the effects of process changes on detergent clearance.

Universal influenza B vaccine based on the maturational cleavage site of the hemagglutinin precursor.

Conventional influenza vaccines can prevent infection, but their efficacy depends on the degree of antigenic "match" between the strains used for vaccine preparation and those circulating in the population. A universal influenza vaccine based on invariant regions of the virus, able to provide broadly cross-reactive protection, without requiring continuous manufacturing update, would solve a major medical need. Since the temporal and geographical dominance of the influenza virus type and/or subtype (A/H3, A/H1, or B) cannot yet be predicted, a universal vaccine, like the vaccines currently in use, should include both type A and type B influenza virus components. However, while encouraging preclinical data are available for influenza A virus, no candidate universal vaccine is available for influenza B virus. We show here that a peptide conjugate vaccine, based on the highly conserved maturational cleavage site of the HA(0) precursor of the influenza B virus hemagglutinin, can elicit a protective immune response against lethal challenge with viruses belonging to either one of the representative, non-antigenically cross-reactive influenza B virus lineages. We demonstrate that protection by the HA(0) vaccine is mediated by antibodies, probably through effector mechanisms, and that a major part of the protective response targets the most conserved region of HA(0), the P1 residue of the scissile bond and the fusion peptide domain. In addition, we present preliminary evidence that the approach can be extended to influenza A virus, although the equivalent HA(0) conjugate is not as efficacious as for influenza B virus.