Influenza in patients with human immunodeficiency virus infection

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.

Vaccinations for the HIV-Infected Adult: A Review of the Current Recommendations, Part I

Vaccination is a critical component for ensuring the health of those living with the human immunodeficiency virus (HIV) by protection against vaccine-preventable diseases. Since HIV-infected persons may have reduced immune responses and shorter durations of protection post-vaccination, HIV-specific guidelines have been published by global and national advisory organizations to address these potential concerns. This article provides a comprehensive review of the current guidelines and evidence-based data for vaccinating HIV-infected adults, including guidance on modified vaccine dosing and testing strategies, as well as safety considerations, to enhance protection among this vulnerable population. In the current article, part I of the two-part series, inactivated vaccines with broad indications as well as vaccines for specific risk and age groups will be discussed.

Live versus attenuated influenza vaccine uptake and post-vaccination influenza-like illness outcomes in HIV-infected US Air Force members

BACKGROUND

Although clinical data is limited, guidelines recommend avoiding live attenuated intranasal influenza vaccine (LAIV) in HIV-infected persons.

OBJECTIVES

To evaluate non-guideline LAIV use and resulting adverse effects in an HIV-infected population.

STUDY DESIGN

A retrospective analysis of influenza vaccination in US Air Force (USAF) members with HIV infection immunized between 2005 and 2015 was performed. Influenza vaccination history after HIV diagnosis was evaluated, including receipt of LAIV or inactivated influenza vaccine (IIV). The proportion with influenza-like illness (ILI) diagnoses within 30days after vaccination with IIV or LAIV was assessed by ICD-9 codes.

RESULTS

437 patients met inclusion criteria, with 121 (27.7%) receiving at least one dose of LAIV and 316 (72.3%) receiving only IIV during follow-up. The mean number of LAIV doses received was 1.5±0.89 (range, 1-4) and the majority (n=50, 82%) received their first LAIV vaccination within the first year after HIV diagnosis. Patients were predominantly males and the LAIV group had a lower mean age at HIV diagnosis (27.5±6.6) compared to the IIV group (30±7.8; p <0.001). Overall, IIV was associated with ILI diagnosis within 30days of vaccination (X² 4.58; p=0.032), with 16 cases (94.1%) occurring in those who received IIV compared to 1 case (5.9%) in those who received LAIV.

CONCLUSION

Although over a quarter of USAF members received LAIV after HIV diagnosis, LAIV administration did not show an increased frequency of post-vaccine ILI diagnoses. Further education is needed to ensure that USAF members with HIV infection are vaccinated according to guideline recommendations, particularly newly diagnosed patients.

Duration of Influenza Virus Shedding Among HIV-Infected Adults in the cART Era, 2010-2011

The duration of influenza virus shedding in HIV-infected adults is unknown and could affect quarantine and treatment recommendations. Participants were monitored for influenza-like illness (ILI), defined as fever and cough or sore throat, using weekly telephone audio computer-assisted self-interviews. Those with ILI were further evaluated at three HIV specialty clinics. For those with influenza, we collected nasopharyngeal washes every 3 days after the date of confirmed influenza infection for 21-28 days; specimens underwent reverse transcriptase - polymerase chain reaction (RT-PCR) and viral culture. Duration of influenza virus shedding was the interval from the date of onset (day 0) of ILI to the date of last culture-positive specimen. Characteristics were compared between patients with and without influenza using Fisher's exact test. We used the Wilcoxon rank-sum test to examine factors that may have affected influenza virus shedding. From October 2010 to April 2011, we enrolled 961 participants in syndromic surveillance and diagnosed 20 patients with influenza whose characteristics were as follows: median age 48 years (interquartile range [IQR]: 43-53), 60% male, 50% non-Hispanic black, 95% had been prescribed combination highly active antiretroviral therapy (cART), 85% were virologically suppressed (HIV RNA <400 copies/ml), median CD4 cell count 317 cells/mm³ (IQR: 190-544), and median follow-up time 21 days (IQR: 19-22). Compared with persons without influenza, persons with influenza were more likely to be older, use injection drugs, and have a lower median CD4 cell count and were less likely to have had an influenza vaccination in the past 12 months. Median durations of shedding, PCR detection, and ILI symptoms were 3 (IQR: 0-5), 10 (IQR: 6-15), and 14 days (IQR: 12-26), respectively. Median days of shedding were similar among patients with and without any prior influenza vaccination (0 vs. 4, p = .448), HIV viral suppression (2 vs. 6, p = .053), and oseltamivir use (5 vs. 0, p = .083). HIV-infected persons on cART in our study shed influenza virus for a similar duration as that reported for HIV-uninfected persons.

Vitamin D levels and influenza vaccine immunogenicity among HIV-infected and HIV-uninfected adults

BACKGROUND

Vaccination is the most important preventive strategy against influenza, however post-vaccination antibody responses are often inadequate especially among HIV-infected persons. Vitamin D deficiency has been suggested to adversely influence immune responses and is highly prevalent among HIV-infected adults. Therefore, we evaluated the association between 25-hydroxyvitamin D [25(OH)D] levels and post-influenza vaccination responses.

METHODS

We conducted a prospective cohort study evaluating the immunogenicity of monovalent influenza A (H1N1) vaccination among both HIV-infected and HIV-uninfected adults (18-50years of age) during the 2009-2010 influenza season. Antibody titers were evaluated at baseline, day 28, and 6months post-vaccination using hemagluttination inhibition assays. Serum 25(OH)D levels were measured at day 28. Univariate and multivariate regression analyses examined the association between 25(OH)D levels [categorized as <20ng/ml (deficiency) vs. ⩾20ng/ml] with the primary outcome of seroconversion. Secondary outcomes included seroprotection; a ⩾4-fold increase in titers; and geometric mean titers post-vaccination. Analyses were repeated using 25(OH)D levels as a continuous variable.

RESULTS

A total of 128 adults [64 HIV-infected (median CD4 count 580cells/mm(3)) and 64 HIV-uninfected] were included. Seroconversion at day 28 post-vaccination was achieved in fewer HIV-infected participants compared with HIV-uninfected participants (56% vs. 74%, p=0.03). Vitamin D deficiency was more prevalent among HIV-infected persons vs. HIV-uninfected persons (25% vs. 17%), although not significantly different (p=0.39). There were no associations found between lower 25(OH)D levels and poorer antibody responses at day 28 or 6months for any of the study outcomes among either HIV-infected or HIV-uninfected adults.

CONCLUSION

Vitamin D deficiency was common among both HIV-infected and HIV-uninfected adults, but lower levels did not predict antibody responses after H1N1 (2009) influenza vaccination. Low 25(OH)D levels do not explain poorer post-vaccination responses among HIV-infected persons.

Increased Rates of Respiratory and Diarrheal Illnesses in HIV-Negative Persons Living With HIV-Infected Individuals in a Densely Populated Urban Slum in Kenya

BACKGROUND

Prolonged pathogen shedding and increased duration of illness associated with infections in immunosuppressed individuals put close human immunodeficiency virus (HIV)-negative contacts of HIV-infected persons at increased risk of exposure to infectious pathogens.

METHODS

We calculated incidence and longitudinal prevalence (number of days per year) of influenzalike illness (ILI), diarrhea, and nonspecific febrile illness during 2008 from a population-based surveillance program in the urban slum of Kibera (Kenya) that included 1830 HIV-negative household contacts of HIV-infected individuals and 13 677 individuals living in exclusively HIV-negative households.

RESULTS

For individuals ≥5 years old, incidence was significantly increased for ILI (risk ratio [RR], 1.47; P < .05) and diarrhea (RR, 1.41; P < .05) in HIV-negative household contacts of HIV-infected individuals compared with exclusively HIV-negative households. The risk of illness among HIV-negative persons was directly proportional to the number of HIV-infected persons living in the home for ILI (RR, 1.39; P < .05) and diarrhea (RR, 1.36; P < .01). We found no increased rates of illness in children <5 years old who lived with HIV-infected individuals.

CONCLUSIONS

Living with HIV-infected individuals is associated with modestly increased rates of respiratory and diarrheal infections in HIV-negative individuals >5 years old. Targeted interventions are needed, including ensuring that HIV-infected persons are receiving appropriate care and treatment.

The Role of HIV in the Household Introduction and Transmission of Influenza in an Urban Slum, Nairobi, Kenya, 2008-2011

BACKGROUND

Little is known about how human immunodeficiency virus (HIV) infection affects influenza transmission within homes in sub-Saharan Africa.

METHODS

We used respiratory illness surveillance and HIV testing data gathered in Kibera, an urban slum in Nairobi, Kenya, to examine the impact of HIV status on (1) introducing influenza to the home and (2) transmitting influenza to household contacts.

RESULTS

While HIV status did not affect the likelihood of being an influenza index case, household contacts of HIV-infected influenza index cases had twice the risk of developing secondary influenza-like illness than contacts of HIV-negative index cases.

CONCLUSIONS

HIV-infected influenza index cases may facilitate transmission of influenza within the home.

Cellular and humoral cross-immunity against two H3N2v influenza strains in presumably unexposed healthy and HIV-infected subjects

Human cases of infection due to a novel swine-origin variant of influenza A virus subtype H3N2 (H3N2v) have recently been identified in the United States. Pre-existing humoral and cellular immunity has been recognized as one of the key factors in limiting the infection burden of an emerging influenza virus strain, contributing to restrict its circulation and to mitigate clinical presentation. Aim of this study was to assess humoral and cell-mediated cross immune responses to H3N2v in immuno-competent (healthy donors, n = 45) and immuno-compromised hosts (HIV-infected subjects, n = 46) never exposed to H3N2v influenza strain. Humoral response against i) H3N2v (A/H3N2/Ind/08/11), ii) animal vaccine H3N2 strain (A/H3N2/Min/11/10), and iii) pandemic H1N1 virus (A/H1N1/Cal/07/09) was analysed by hemagglutination inhibition assay; cell-mediated response against the same influenza strains was analysed by ELISpot assay. A large proportion of healthy and HIV subjects displayed cross-reacting humoral and cellular immune responses against two H3N2v strains, suggesting the presence of B- and T-cell clones able to recognize epitopes from emerging viral strains in both groups. Specifically, humoral response was lower in HIV subjects than in HD, and a specific age-related pattern of antibody response against different influenza strains was observed both in HD and in HIV. Cellular immune response was similar between HD and HIV groups and no relationship with age was reported. Finally, no correlation between humoral and cellular immune response was observed. Overall, a high prevalence of HD and HIV patients showing cross reactive immunity against two H3N2v strains was observed, with a slightly lower proportion in HIV persons. Other studies focused on HIV subjects at different stages of diseases are needed in order to define how cross immunity can be affected by advanced immunosuppression.

Vaccination in HIV-infected adults

Vaccines are critical components for protecting HIV-infected adults from an increasing number of preventable diseases. However, missed opportunities for vaccination among HIV-infected persons persist, likely due to concerns regarding the safety and efficacy of vaccines, as well as the changing nature of vaccine guidelines. In addition, the optimal timing of vaccination among HIV-infected adults in regards to HIV stage and receipt of antiretroviral therapy remain important questions. This article provides a review of the current recommendations regarding vaccines among HIV-infected adults and a comprehensive summary of the evidence-based literature of the benefits and risks of vaccines among this vulnerable population.

High level antibody avidity is achieved in HIV-seropositive recipients of an inactivated split adjuvanted (AS03A) influenza vaccine

PURPOSE

More severe influenza disease and poor vaccine immunogenicity is reported in HIV-infected patients. We measured antibody avidity after influenza vaccination in HIV patients to assess vaccine efficacy.

METHODS

Two dosing strategies (Group1: single dose, n = 28. Group2: single dose plus booster, n = 36) with an AS03A-adjuvanted H1N12009 pandemic influenza vaccine (Arepanrix, GSK) were assessed in HIV patients. Serum hemagglutination inhibition (HAI) titers and antibody avidity reported as an avidity index (AI) were measured at days 21 and 42 and at 6 months.

RESULTS

Baseline HIV parameters were similar among all participants. Eighteen participants had measurable baseline HAI titers. In these subjects, AI was at ~9 at baseline and was not significantly increased by one or two vaccine doses. In those without detectable baseline antibodies, immunization induced modest antibody titers [Group1 HAI, 61 (26-144); Group2 HAI, 46 (28-76)] with high AI after one dose at day 21 [Group1 AI, 8.8 (7.3-10.7); Group2 AI, 8.9 (7.8-10.1)]. A second dose of vaccine generated significantly higher HAI titers at day 42 [Group1 HAI, 41 (18-90); Group2 HAI, 92 (64-132)] and persisted to 6 months [Group1 HAI, 9 (6-13); Group2 HAI, 19 (13-30)]. All subjects who produced detectable HAI titers after vaccination generated high antibody avidity (AI, 9-10), which persisted up to 6 months.

CONCLUSION

In participants initially seronegative, two doses of vaccine enabled a greater percentage of subjects to respond to the vaccine and elicited higher HAI titers. All subjects who produced detectable HAI titers also rapidly generated high AI in the short and long term. We demonstrate that high avidity antibodies can be achieved after vaccination and support a two-dose immunization strategy for HIV-positive subjects.

The natural history of influenza infection in the severely immunocompromised vs nonimmunocompromised hosts

Introduction. Medical advances have led to an increase in the world's population of immunosuppressed individuals. The most severely immunocompromised patients are those who have been diagnosed with a hematologic malignancy, solid organ tumor, or who have other conditions that require immunosuppressive therapies and/or solid organ or stem cell transplants.

Materials and methods. Medically attended patients with a positive clinical diagnosis of influenza were recruited prospectively and clinically evaluated. Nasal washes and serum were collected. Evaluation of viral shedding, nasal and serum cytokines, clinical illness, and clinical outcomes were performed to compare severely immunocompromised individuals to nonimmunocompromised individuals with influenza infection.

Results. Immunocompromised patients with influenza had more severe disease/complications, longer viral shedding, and more antiviral resistance while demonstrating less clinical symptoms and signs on clinical assessment.

Conclusions. Immunocompromised patients are at risk for more severe or complicated influenza induced disease, which may be difficult to prevent with existing vaccines and antiviral treatments. Specific issues to consider when managing a severely immunocompromised host include the development of asymptomatic shedding, multi-drug resistance during prolonged antiviral therapy, and the potential high risk of pulmonary involvement.

Clinical trials registration, ClinicalTrials.gov identifier NCT00533182.

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.

Higher antigen content improves the immune response to 2009 H1N1 influenza vaccine in HIV-infected adults: a randomized clinical trial

BACKGROUND

The immunogenicity of a high hemagglutinin (HA) dose or a second dose of influenza vaccine in human immunodeficiency virus (HIV)-infected individuals has not been fully explored.

METHODS

One hundered ninety-two HIV-infected individuals aged 18-64 years were stratified by CD4 cell count (<200 cells/mL or ≥200 cells/mL) and randomized to receive 2 doses of 15 μg or 30 μg HA 2009 H1N1 vaccine 21 days apart. Hemagglutination inhibition (HAI) and microneutralization (MN) antibodies were measured on days 0, 10, 21, 31, 42, and 201.

RESULTS

Recipients of 30 μg HA had significantly higher HAI geometric mean titers (GMTs), compared with recipients of 15 μg HA on days 10 (139.0 vs 51.9; P = .01), 21 (106.7 vs 51.9; P = .001), and 31 (130.0 vs 73.7; P = .03) but not on days 42 (91.8 vs 61.6; P = .11) and 201 (43.0 vs 27.0; P = .08). When analyzed by CD4 cell count stratum, HAI GMTs were significantly higher among 30 μg HA recipients than among 15 μg HA in the CD4 cell count <200 cells/mL stratum on days 21 and 31 and the MN GMTs on days 10, 21, 31, and 42 (P < .05). In the CD4 cell count ≥200 cells/mL stratum, MN GMTs were significantly higher among recipients of 30 μg HA than among recipients of 15 μg HA on day 10 (P = .03).

CONCLUSION

Increasing the HA dose of the 2009 H1N1 vaccine improves the vaccine's immunogenicity in HIV-infected individuals.

CLINICAL TRIALS REGISTRATION

NCT00992433.

A review of influenza vaccine immunogenicity and efficacy in HIV-infected adults

BACKGROUND

HIV-seropositive adults are at an increased risk for influenza infection. They also develop more severe influenza disease and are hyporesponsive to current influenza vaccinations.

METHODS

The authors examined findings from a systematic review of influenza vaccination in HIV-seropositive adults, and evaluated other relevant studies. A narrative overview of findings formulated to summarize the implications of currently available literature is presented. The primary goal of the present review is to assess the limitations of current evidence and to provide a framework for additional research.

RESULTS

There is a paucity of knowledge regarding the relative value of prophylactic influenza vaccination in HIV-positive adults compared with immunocompetent populations. There are shortcomings related to study methodology and temporal changes in the characteristics of patient baseline immune status, which limit the utility of this information to shape public health policy.

CONCLUSIONS

There is a pressing need to pursue methodologically rigorous studies that will increase knowledge related to improving the effectiveness of preventive influenza measures in this patient population.

Pandemic influenza is a strong motivator for participation in vaccine clinical trials among HIV-positive Canadian adults

BACKGROUND

HIV-positive patients represent an immunosuppressed population at risk for severe influenza. In the event of a pandemic, such as 2009 H1N1, rapid implementation of vaccine clinical trials in target populations will be critical. In the present paper, knowledge and attitudes of HIV-positive adults regarding seasonal/pandemic influenza vaccination were evaluated, and facilitators and barriers to participation in vaccine clinical trials were explored.

METHODS

A validated, 70-item, self-administered questionnaire was distributed to all HIV patients presenting for routine follow-up at eight Canadian Institutes of Health Research Canadian HIV Trials Network (CTN) sites from October 2008 to February 2009, as well as all participants in CTN trial 237. This study has representation from all Canadian provinces.

RESULTS

In total, 610 HIV-positive adults responded (298 CTN 237 participants; 312 non-CTN 237 participants). Most reported receiving influenza vaccine last season (83% of CTN 237 participants versus 83% non-CTN 237 participants; P not significant) and most would receive a pandemic influenza vaccine if offered (76% versus 73%; P not significant). A majority believed that it was important to include HIV patients in vaccine clinical trials (65% versus 53%; P<0.001) and would agree to participate in trials of a pandemic vaccine if invited (86% versus 51%; P≤0.0001). Predictors of willingness to participate in a pandemic vaccine trial were 'desire to be protected from pandemic flu', OR 4.5 (95% CI 2 to 8) and 'desire to help others', OR 2.3 (95% CI 1.3 to 4.5). 'Fear of needles', OR 0.49 (95% CI 0.1 to 1.5) and 'need for extra blood tests', OR 0.49 (95% CI 0.2 to 1.4) were key barriers to participation.

CONCLUSION

Most HIV-positive Canadian adults surveyed receive influenza vaccination. Protection from pandemic influenza is considered important and is a motivator for receiving influenza vaccine and future trial participation. Modifiable barriers to these objectives identified in the present study should be the focus of efforts to increase influenza immunization in this population.

Influenza in immunocompromised patients: considerations for therapy

Influenza infection results in substantial morbidity and mortality in immunocompromised patients, and the risks for influenza and its related complications depend on the degree of immunosuppression. In addition to influenza vaccination and infection control precautions, two classes of antiviral drugs are currently approved for treatment and prophylaxis in uncomplicated infected patients. However, there are no randomized controlled trials assessing the efficacy and safety of licensed antivirals for influenza management in immunocompromised patients. The purpose of this article is to highlight some considerations for therapy in immunocompromised patients, the usefulness of vaccination for the prevention of influenza and the clinical interest in surveillance of antiviral resistance.

Seroincidence of 2009 H1N1 infection in HIV-infected and HIV-uninfected women prior to vaccine availability

The 2009 H1N1 pandemic was a unique opportunity to investigate differences in influenza infection using serology by HIV status. Using serial serum specimens collected from 1 April to 30 September 2009 and the prior 2 years from Women's Interagency HIV study participants, there was no difference in serologic evidence of 2009 H1N1 infection among HIV-infected women with a CD4 cell count at least 350 cells/μl compared with HIV-uninfected women. Owing to evidence showing a greater risk of influenza-related complications, HIV-infected individuals should continue to be a priority group for vaccination.

HIV-infected hospitalized patients with 2009 pandemic influenza A (pH1N1)--United States, spring and summer 2009

We describe the clinical findings of HIV-infected patients hospitalized with 2009 pandemic influenza A (pH1N1). Data were derived from 3 separate case series in the United States. Among 911 adults hospitalized with pH1N1 influenza, 31 (3.4%) were HIV infected compared with an HIV prevalence of 0.45% in the general US adult population. HIV-infected influenza patients experienced similar rates of intensive care unit admission (29% vs 34%) and death (13% vs 13%) compared with non-HIV-infected patients. Among HIV-infected patients with available data, 14 (50%) of 28 patients had a CD4 cell count <200 cells/μL, which was not associated with an increased risk of an intensive care unit admission or death. Overall, 25 (81%) HIV-infected patients received influenza antiviral therapy, but treatment was initiated within 48 h of illness onset in only 33% of cases. Clinicians should consider early empiric influenza antiviral treatment in HIV-infected patients presenting with suspected influenza.

Influenza susceptibility, severity, and shedding in HIV-infected adults: a review of the literature

Influenza is a common cause of respiratory illness in adults infected with human immunodeficiency virus (HIV), but current knowledge about seasonal and 2009 H1N1 pandemic influenza A (H1N1pdm) virus infections in HIV-infected persons is limited. In this paper, we review the existing literature regarding influenza susceptibility, severity, and shedding in HIV-infected adults. Data show HIV infection does not significantly increase susceptibility to influenza. AIDS is associated with greater seasonal influenza-related morbidity and mortality, but the risk associated with HIV infection among those with less immune suppression is largely unknown. Immunologic compromise has been shown to increase the magnitude and duration of influenza virus shedding; however, these studies are limited within HIV-infected populations. With regards to H1N1pdm, data are even more limited. Reports raise concern of increased severity among HIV-infected persons, although this may be driven by other comorbid illnesses. Prospective studies are needed among HIV-infected persons to more definitively investigate influenza susceptibility, severity, and shedding.

Durability of antibody responses after receipt of the monovalent 2009 pandemic influenza A (H1N1) vaccine among HIV-infected and HIV-uninfected adults

BACKGROUND

Human immunodeficiency virus (HIV)-infected persons are at risk for severe influenza infections. Although vaccination against the H1N1 pandemic influenza strain is recommended, currently there are no data on the durability of post-vaccination antibody responses in this population.

METHODS

HIV-infected and HIV-uninfected adults (18-50 years old) received a single dose of monovalent 2009 influenza A (H1N1) vaccine (strain A/California/7/2009H1N1). Antibody levels to the 2009 H1N1 pandemic strain were determined at day 0, day 28, and 6 months by hemagglutination-inhibition assay. A seroprotective response was a post-vaccination titer of ≥1:40 among those with a pre-vaccination level of ≤1:10. Geometric mean titers (GMT) and factors associated with higher levels were also evaluated.

RESULTS

We studied 127 participants with a median age of 35 (interquartile range (IQR) 28, 42) years. Among the HIV-infected arm (n=63), the median CD4 count was 595 (IQR 476, 819)cells/mm(3) and 83% were receiving HAART. Thirty-five percent of all participants had a pre-vaccination level of >1:10. HIV-infected compared to HIV-uninfected adults were less likely to generate a seroprotective response at day 28 (54% vs. 75%, adjusted OR 0.23, p=0.021) or have a durable response at 6 months post-vaccination (28% vs. 56%, adjusted OR 0.19, p=0.005). Additionally, although pre-vaccination GMT were similar in both arms (median 7 vs. 8, p=0.11), the GMT at 6 months was significantly lower among HIV-infected versus HIV-uninfected adults (median 20 vs. 113, p=0.003). Among HIV-infected persons, younger age (p=0.035) and receipt of HAART (p=0.028) were associated with higher GMTs at 6 months.

CONCLUSIONS

Despite vaccination, most HIV-infected adults do not generate durable seroprotective antibody responses to the 2009 influenza A (H1N1) virus, and hence may remain vulnerable to infection. In addition to HAART use, more immunogenic vaccines are likely needed for improving protection against influenza in this population.

Immunogenicity is not improved by increased antigen dose or booster dosing of seasonal influenza vaccine in a randomized trial of HIV infected adults

INTRODUCTION

The risk of poor vaccine immunogenicity and more severe influenza disease in HIV necessitate strategies to improve vaccine efficacy.

METHODS

A randomized, multi-centered, controlled, vaccine trial with three parallel groups was conducted at 12 CIHR Canadian HIV Trials Network sites. Three dosing strategies were used in HIV infected adults (18 to 60 years): two standard doses over 28 days, two double doses over 28 days and a single standard dose of influenza vaccine, administered prior to the 2008 influenza season. A trivalent killed split non-adjuvanted influenza vaccine (Fluviral™) was used. Serum hemagglutinin inhibition (HAI) activity for the three influenza strains in the vaccine was measured to assess immunogenicity.

RESULTS

297 of 298 participants received at least one injection. Baseline CD4 (median 470 cells/µL) and HIV RNA (76% of patients with viral load <50 copies/mL) were similar between groups. 89% were on HAART. The overall immunogenicity of influenza vaccine across time points and the three influenza strains assessed was poor (Range HAI ≥ 40 =  31-58%). Double dose plus double dose booster slightly increased the proportion achieving HAI titre doubling from baseline for A/Brisbane and B/Florida at weeks 4, 8 and 20 compared to standard vaccine dose. Increased immunogenicity with increased antigen dose and booster dosing was most apparent in participants with unsuppressed HIV RNA at baseline. None of 8 serious adverse events were thought to be immunization-related.

CONCLUSION

Even with increased antigen dose and booster dosing, non-adjuvanted influenza vaccine immunogenicity is poor in HIV infected individuals. Alternative influenza vaccines are required in this hyporesponsive population.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00764998.

Enhancing effects of adjuvanted 2009 pandemic H1N1 influenza A vaccine on memory B-cell responses in HIV-infected individuals

OBJECTIVE

To assess the humoral immune response to low-dose AS03-adjuvanted and standard-dose nonadjuvanted 2009 pandemic H1N1 influenza A vaccine in HIV-infected aviremic individuals receiving antiretroviral therapy and in uninfected individuals.

DESIGN

A three-arm study.

SETTING

Two clinics: one at the National Institutes of Health in Bethesda, Maryland, USA; and the other at the Maple Leaf Medical Clinic in Toronto, Ontario, Canada.

PARTICIPANTS

HIV-infected and HIV-uninfected adults.

INTERVENTION

Single intramuscular 15 μg dose of the monovalent inactivated 2009 pandemic H1N1 influenza A vaccine without adjuvant or 3.75 μg dose of the same strain with adjuvant AS03.

MAIN OUTCOMES

Immunogenicity, as measured by hemagglutination inhibition (HAI) antibody titers and vaccine-specific memory B-cell responses.

RESULTS

A total of 74 participants were enrolled. Twenty-one HIV-infected individuals received the low-dose adjuvanted 2009 pandemic H1N1 influenza A vaccine. Twenty-nine HIV-infected and 24 HIV-uninfected individuals received the standard-dose nonadjuvanted vaccine. There were no significant differences in antibody responses at 9 weeks postvaccination among the three groups studied. However, the IgG memory B-cell response against the vaccine was significantly higher in the HIV-infected group that received the low-dose adjuvanted vaccine when compared to the HIV-infected and uninfected groups that received the standard-dose nonadjuvanted vaccine. Conclusions remained unchanged after regression adjustment for age, gender, CD4 T-cell count, and baseline HAI titer.

CONCLUSION

These data suggest that adjuvants could be used to expand coverage through dose sparing and improve humoral immune responses in immunocompromised individuals.

Immunogenicity of a monovalent 2009 influenza A (H1N1) vaccine in an immunocompromised population: a prospective study comparing HIV-infected adults with HIV-uninfected adults

BACKGROUND

Limited data exist on the immunogenicity of the 2009 influenza A (H1N1) vaccine among immunocompromised persons, including those with human immunodeficiency virus (HIV) infection.

METHODS

We compared the immunogenicity and tolerability of a single dose of the monovalent 2009 influenza A (H1N1) vaccine (strain A/California/7/2009H1N1) between HIV-infected and HIV-uninfected adults 18-50 years of age. The primary end point was an antibody titer of ≥ 1:40 at day 28 after vaccination in those with a prevaccination level of ≤ 1:10, as measured by hemagglutination-inhibition assay. Geometric mean titers, influenza-like illnesses, and tolerability were also evaluated.

RESULTS

One hundred thirty-one participants were evaluated (65 HIV-infected and 66 HIV-uninfected patients), with a median age of 35 years (interquartile range, 27-42 years). HIV-infected persons had a median CD4 cell count of 581 cells/mm(3) (interquartile range, 476-814 cells/mm(3)) , and 82% were receiving antiretroviral medications. At baseline, 35 patients (27%) had antibody titers of >1:10. HIV-infected patients (29 [56%] of 52), compared with HIV-uninfected persons (35 [80%] of 44), were significantly less likely to develop an antibody response (odds ratio, .20; P = .003). Changes in the median geometric mean titer from baseline to day 28 were also significantly lower in HIV-infected patients than in HIV-uninfected persons (75 vs 153; P = .001). Five influenza-like illnesses occurred (2 cases in HIV-infected persons), but none was attributable to the 2009 influenza H1N1 virus. The vaccine was well tolerated in both groups.

CONCLUSIONS

Despite high CD4 cell counts and receipt of antiretroviral medications, HIV-infected adults generated significantly poorer antibody responses, compared with HIV-uninfected persons. Future studies evaluating a 2-dose series or more-immunogenic influenza A (H1N1) vaccines among HIV-infected adults are needed (ClinicalTrials.gov NCT00996970).

Clinical presentation and prognosis of the 2009 H1N1 influenza A infection in HIV-1-infected patients: a Spanish multicenter study

OBJECTIVE

The aim of the study was to describe the clinical presentation and prognosis in HIV-1-infected patients with hospital admission and pandemic influenza A 2009 (H1N1) confirmed, and compare this data with those of a general population.

DESIGN

: This is a prospective study in nature.

METHODS

All adult patients admitted to 13 hospitals in Spain with confirmed influenza A 2009(H1N1) virus infection by real-time reverse transcriptase PCR assay or culture from June 12 to November 10, 2009 were recruited and followed up until 1 month after discharge. In the HIV group risk factors for HIV infection, AIDS criteria, last CD4 cell count and viral load, and antiretroviral therapy and pneumococcal vaccines were collected.

RESULTS

Five hundred and eighty-five patients were recruited, 26 with HIV-1 infection and 559 non-HIV. The HIV patients had a long-term well controlled infection with a median CD4 cell count 503 cells/μl and 84% with undetectable viral load, although more frequently they had chronic liver and chronic obstructive pulmonary disease. No significant differences were observed about reported symptoms and physical findings on hospital admission. About 50% of patients in both groups present radiological infiltrates and 30% present respiratory failures. Practically all the patients in both groups received influenza antiviral therapy and in each group 80% received antibacterial therapy. No differences were observed in clinical outcomes.

CONCLUSION

In HIV patients, well controlled on HAART, the pandemic influenza virus AH1N1 had a similar clinical outcome and prognosis to that of non-HIV patients.

Differences in the epidemiological characteristics and clinical outcomes of pandemic (H1N1) 2009 influenza, compared with seasonal influenza

BACKGROUND

There are limited data comparing the clinical presentations, comorbidities, and outcomes of patients with infections due to seasonal influenza with patients with infections due to pandemic (H1N1) 2009 influenza.

OBJECTIVE

To compare the epidemiological characteristics and outcomes of pandemic (H1N1) 2009 influenza with those of seasonal influenza.

METHODS

A cross-sectional study was conducted among patients who received diagnoses during emergency department and inpatient encounters at 2 affiliated academic medical centers in Philadelphia, Pennsylvania. Cases of seasonal influenza during the period November 1, 2005, through June 1, 2008, and cases of pandemic influenza during the period from May 1, 2009, through August 7, 2009, were identified retrospectively.

RESULTS

Forty-nine cases of pandemic influenza and 503 cases of seasonal influenza were identified. Patients with pandemic H1N1 were younger (median age, 29 years) than patients with seasonal influenza (median age, 59 years) (P<.001). More patients with pandemic H1N1 (35 [71%] of 49) were African American, compared with patients with seasonal influenza (267 [53%] of 503; P=.02). Several symptoms were more common among patients with pandemic influenza infections than among patients with seasonal influenza infections: cough (98% vs 83%; P=.007), myalgias (71% vs 46%; P=.001), and pleuritic chest pain (45% vs 15%; P<.001). Pregnancy was the only comorbidity that occurred significantly more often in the pandemic influenza group than in the seasonal influenza group (16% vs 1%; P<.001). There were no significant differences in frequencies of deaths of hospitalized patients, intensive care unit admission, or length of hospitalization between groups.

CONCLUSION

Other than pregnancy, there were few clinically important differences between infections due to seasonal influenza and those due to pandemic influenza. The greater rate of lower respiratory tract symptoms in pandemic cases might serve to differentiate pandemic influenza from seasonal influenza.

Antibody response to tetravalent influenza subunit vaccine in patients infected with human immunodeficiency virus type 1

The capacity of patients infected with human immunodeficiency virus (HIV) to develop an adequate antibody response to influenza vaccination in relation to the CD4 cell count has been studied in a prospective study. A total of 73 subjects (54 HIV-infected patients and 19 healthy control persons) were vaccinated with influenza subunit vaccine containing 15 mug hemagglutinin of each of the following strains: A/Beijing/353/89(H3N2), A/Singapore/6/86(H1N1), B/Panama/45/90, and B/Beijing/1/87. Hemagglutinin inhibition (HI) antibody titers were determined prior to vaccination, 3 weeks afterwards, and at the end of the influenza season. The percentage of subjects with HI antibody titers above the assumed protective level was significantly lower in the HIV-infected patients for all 4 vaccine strains compared with those in the control group (7-26% and 42-74%, respectively). There was an association between CD4 cell count and antibody response to the B/Panama strain only. The serologic response to tetravalent subunit influenza vaccine is severely impaired in the majority of HIV-infected patients compared with control subjects. The results of this study challenges the recommendation to vaccinate HIV-infected patients.

Viral infections of the respiratory tract: prevention and treatment

The rapid discovery of specific viral agents as the cause of many acute respiratory diseases was accompanied by considerable optimism that vaccines or other control measures could be developed quickly. Subsequent experience has demonstrated that effective control of these important public health problems has been an elusive goal. However, recent exciting developments in our understanding of the molecular biology and immunology of these viruses may provide the basis for more effective strategies in the future.

Predictors of reported influenza vaccination in HIV-infected women in the United States, 2006-2007 and 2007-2008 seasons

OBJECTIVE

To estimate the cumulative incidence of self-reported influenza vaccination ("vaccination coverage") and investigate predictors in HIV-infected women.

METHODS

In an ongoing cohort study of HIV-infected women in five US cities, data from two influenza seasons (2006-2007 n=1209 and 2007-2008 n=1161) were used to estimate crude and adjusted prevalence ratios (aPR) and 95% confidence intervals ([,]) from Poisson regression with robust variance models using generalized estimating equations (GEE).

RESULTS

In our study, 55% and 57% of HIV-infected women reported vaccination during the 2006-2007 and 2007-2008 seasons, respectively. Using data from both seasons, older age, non-smoking status, CD4 T-lymphocyte (CD4) count > or =200 cells/mm(3), and reporting at least one recent healthcare visit was associated with increased vaccination coverage. In the 2007-2008 season, a belief in the protection of the vaccine (aPR=1.38 [1.18, 1.61]) and influenza vaccination in the previous season (aPR=1.66 [1.44, 1.91]) most strongly predicted vaccination status.

CONCLUSION

Interventions to reach unvaccinated HIV-infected women should focus on changing beliefs about the effectiveness of influenza vaccination and target younger women, current smokers, those without recent healthcare visits, or a CD4 count <200 cells/mm(3).

H1N1 novel influenza A in pregnant and immunocompromised patients

OBJECTIVE

To describe the increased risk of severe disease and the appropriate management of patients at high risk such as pregnant women and immunosuppressed patients who acquire novel influenza A (H1N1).

DESIGN

Review of the literature regarding influenza A in these patient groups, and review of published and unpublished data with regard to novel influenza A (H1N1).

MAIN RESULTS

Pregnant women are at increased risk for severe pneumonitis and respiratory failure from influenza infection, particularly during pandemics, including the current pandemic. Fetal morbidity is significant, usually resulting from maternal fever and severe hypoxemia. Early antiviral therapy using oseltamivir may be beneficial, and intensive care unit support should target adequate oxygenation at all times. Immunosuppressed patients are at increased risk for influenza, as well as at risk for more severe or prolonged infection. Patients after hematopoietic stem cell transplantation, after lung transplantation, and those receiving chemotherapy for leukemia are at highest risk, whereas the risk for human immunodeficiency virus-infected individuals appears relatively low. Treatment with antiviral therapy may be beneficial, even after the usual cut-off of 48 hrs after symptom onset.

CONCLUSIONS

Optimal management of these patients is preventive by influenza vaccination, but the neuraminidase inhibitor antiviral agents provide effective treatment.

Rapid selection of a transmissible multidrug-resistant influenza A/H3N2 virus in an immunocompromised host

BACKGROUND

The overall impact of influenza virus infection in immunocompromised patients is largely unknown. Antigenic drift and genetic variations during prolonged influenza infection have been demonstrated. In this report we describe a multidrug-resistant H3N2 influenza virus isolated from an immunocompromised patient after 5 days of therapy.

METHODS

Multiple nasal wash samples were collected from an infected patient, and viral isolates were characterized. Sensitivity to antiviral agents was evaluated. Fitness and transmissibility were assessed in ferrets and tissue culture.

RESULTS

An in-frame 4-amino acid deletion emerged in the neuraminidase (NA) gene of an H3N2 virus after 5 days of oseltamivir therapy. No other changes in the NA or hemagglutinin genes were noted. Drug sensitivity assays revealed resistance to oseltamivir (>10-fold increase in 50% inhibitory concentration [IC(50)]) and reduction in sensitivity to zanamivir (3-7-fold increase in IC(50) or 50% effective concentration). No change in fitness or transmissibility was observed.

CONCLUSIONS

An in-frame NA gene deletion was rapidly selected for in an immunocompromised patient, resulting in decreased sensitivity of the isolate to available NA inhibitors without a change in fitness or transmissibility. This finding has implications for our understanding of the emergence of antiviral resistance and treatment of patients with influenza A infection, especially those who are immunocompromised.

A case of pandemic 2009 influenza A (H1N1) in a patient with HIV infection

Little is known about pandemic 2009 influenza A (H1N1) among patients with human immunodeficiency virus (HIV) infection. We report a case of 2009 influenza A (H1N1) in a patient who was newly diagnosed as having HIV. His general condition was good, and he was successfully treated in an outpatient setting. The literature was reviewed for the diagnosis, treatment, prevention, and infection control of pandemic 2009 influenza A (H1N1) among those who have HIV infection.

Risk factors for pneumonia in immunocompromised patients with influenza

BACKGROUND

Immunocompromised patients with influenza are at higher risk of pneumonia and death. However, risk factors for progression to pneumonia still need evaluation.

METHODS

Retrospective study in immunocompromised patients with influenza-related respiratory infections. Risk factors for pneumonia were identified by multivariable logistic regression.

RESULTS

We identified 100 immunocompromised patients infected with influenza (68 hematological malignancies, 11 HIV, 21 iatrogenic immunosuppression). Immunofluorescence was positive in 95% of patients, mainly on nasopharyngeal aspirates (84%). Influenza A virus was involved in 80% of patients. Associated infection was documented in 34 patients. All patients presented with upper respiratory tract infection and 53 progressed to pneumonia. Thirty-two patients were critically ill, 11 received mechanical ventilation, and 10 died. All the patients who died had pneumonia. Patients with pneumonia were older (46y (36-63) vs. 33y (13-51), P=0.003) and more often had influenza A (89% vs. 70%, P=0.04) and associated infection (56% vs. 9%, P<0.0001). Factors independently associated with progression to pneumonia were influenza A (OR 5.54, 95% CI [1.16-26.47]) and hematological malignancies (OR 3.85, 95% CI [1.1-14.5]).

CONCLUSIONS

In our cohort of hospitalized immunocompromised patients, influenza progresses to pneumonia in more than half the patients. Patients with hematological malignancies and influenza A infection are at higher risk for pneumonia and should be included in preemptive antiviral therapy trials.

Pandemic influenza: implications for programs controlling for HIV infection, tuberculosis, and chronic viral hepatitis

Among vulnerable populations during an influenza pandemic are persons with or at risk for HIV infection, tuberculosis, or chronic viral hepatitis. HIV-infected persons have higher rates of hospitalization, prolonged illness, and increased mortality from influenza compared with the general population. Persons with tuberculosis and chronic viral hepatitis may also be at increased risk of morbidity and mortality from influenza because of altered immunity and chronic illness. These populations also face social and structural barriers that will be exacerbated by a pandemic. Existing infrastructure should be expanded and pandemic planning should include preparations to reduce the risks for these populations.

Influenza in immunosuppressed populations: a review of infection frequency, morbidity, mortality, and vaccine responses

Patients that are immunosuppressed might be at risk of serious influenza-associated complications. As a result, multiple guidelines recommend influenza vaccination for patients infected with HIV, who have received solid-organ transplants, who have received haemopoietic stem-cell transplants, and patients on haemodialysis. However, immunosuppression might also limit vaccine responses. To better inform policy, we reviewed the published work relevant to incidence, outcomes, and prevention of influenza infection in these patients, and in patients being treated chemotherapy and with systemic corticosteroids. Available data suggest that most immunosuppressed populations are indeed at higher risk of influenza-associated complications, have a general trend toward impaired humoral vaccine responses (although these data are mixed), and can be safely vaccinated--although longitudinal data are largely lacking. Randomised clinical trial data were limited to one study of HIV-infected patients with high vaccine efficacy. Better trial data would inform vaccination recommendations on the basis of efficacy and cost in these at-risk populations.

Influenza

OBJECTIVE

Influenza is a major concern for intensivists in all communities in the U.S. While there is considerable concern whether or not the country will be ready for a pandemic influenza, even seasonal influenza poses a major challenge to hospitals. The objective of this review is to summarize current knowledge of influenza with emphasis on the issues that intensivist will encounter.

SETTING

Intensive care unit in a 450-bed, tertiary care, teaching hospital.

METHODS

Source data were obtained from a PubMed search of the medical literature. PubMed "related articles" search strategies were likewise employed frequently.

SUMMARY AND CONCLUSIONS

Seasonal influenza causes more than 200,000 hospitalizations and 41,000 deaths in the U.S. every year, and is the seventh leading cause of death in the U.S. Despite this impact there is a shortcoming in knowledge of influenza among many health care workers, and a paucity of clinical data and studies to guide therapy. Intensivists need to recognize the importance of seasonal influenza as a cause of severe morbidity and mortality. This review summarizes current knowledge of the diagnosis, complications, therapy, and infection control measures associated with influenza.

Shedding of live vaccine virus, comparative safety, and influenza-specific antibody responses after administration of live attenuated and inactivated trivalent influenza vaccines to HIV-infected children

HIV-infected children (N=243), >or=5 to <18 years old, receiving stable antiretroviral therapy, were stratified by immunologic status and randomly assigned to receive intranasal live attenuated influenza vaccine (LAIV) or intramuscular trivalent inactivated influenza vaccine (TIV). The safety profile after LAIV or TIV closely resembled the previously reported tolerability to these vaccines in children without HIV infection. Post-vaccination hemagglutination inhibition (HAI) antibody responses and shedding of LAIV virus were also similar, regardless of immunological stratum, to antibody responses and shedding previously reported for children without HIV infection. LAIV should be further evaluated for a role in immunizing HIV-infected children.

Distinct cellular immune responses following primary and secondary influenza virus challenge in cotton rats

To evaluate cell-mediated immunity in influenza-infected cotton rats, we compared the cellular composition of spleen, mediastinal lymph nodes (MLN) and bronchoalveolar lavage (BAL) after primary and secondary infection. There was an increase in cellularity in the MLN after primary infection that was further expanded upon rechallenge. CD4(+) T cells expanded after primary infection, but there was preferential increase in the number of CD4-negative T cells following secondary challenge. After primary infection, a large proportion of the monocytes and NK cells were present in the BAL while a T cell population dominated after secondary infection. CD4(+) T cells were predominant in this population unless the animals had been challenged with heterosubtypic influenza A virus. These studies are the first to show evidence of a memory T cell response to influenza infection in cotton rats and show quantitative and qualitative differences between the recall response to homosubtypic and heterosubtypic viruses.

Vaccination in patients with HIV infection

Although vaccine-preventable diseases are common in HIV, concerns about vaccine safety and lack of efficacy in this patient population often lead to missed opportunities for vaccination. In this article, we review the literature regarding vaccine risks and benefits and offer recommendations regarding their use and timing in patients with HIV infection.

Pharmacotherapy, vaccines and malaria advice for HIV-infected travellers

Since the introduction of effective antiretroviral therapy (ART), HIV-infected individuals are travelling more frequently and international travel has become much safer. Specific concerns include the safety of ART during travel, drug adherence and interaction considerations, and effects of immunosuppression. This review describes potentially important infections, vaccine effectiveness, safety and special approaches for their use, and HIV-related issues regarding predeparture counselling. With advanced immunosuppression (CD4+ T-cell count < 200/microl or < 14%), the immunogenicity of several vaccines is reduced, complications could occur after live attenuated vaccines and certain infections acquired during travel may be more frequent or severe. Challenges include the best options for malaria chemoprophylaxis, standby treatment and medical follow-up of the increasing number of HIV-infected long-term travellers.

Preventing pneumonia: the role for pneumococcal and influenza vaccines

Streptococcus pneumoniae and influenza cause a wide spectrum of illness and result in substantial morbidity and mortality. They are significant public health concerns, and vaccines against both organisms exist. The pneumococcal polysaccharide vaccine has been available in its current form for over 20 years. Nonetheless, definitive evidence from prospective trials of its efficacy is lacking. Experts recommend that patients at high risk for pneumococcal infection and complications from this process be vaccinated. The role for revaccination remains controversial. Traditional influenza vaccine is composed of three virus types and decreases rates of serologically confirmed cases of influenza, hospital admissions for respiratory infection, and mortality. The pneumococcal and influenza vaccines are considered cost-effective options for pneumonia prevention.

Influenza virus activates human immunodeficiency virus type-1 gene expression in human CD4-expressing T cells through an NF-κB-dependent pathway

Influenza virus infection can cause severe complications in human immunodeficiency virus type-1 (HIV-1)-infected individuals leading to an increased risk of complications and death compared to that seen in uninfected individuals. We assessed the capacity of influenza virus (Flu) to modulate transcription of the HIV-1 long terminal repeat (LTR) in human CD4+ T cells. We found that Flu is able to promote expression of both the transiently transfected and stably integrated HIV-1 LTR-driven reporter gene. Experiments performed with Arthrobacter-derived neuraminidase and ammonium chloride revealed that Flu-dependent activation of HIV-1 transcription required an intimate contact between Flu and the target cell and efficient entry of Flu inside human CD4+ T cells. Amplification of a Flu-specific mRNA by RT-PCR indicated that human T cells were indeed productively infected with Flu. Virus preparations rendered noninfectious after UV irradiation could no longer upregulate HIV-1 LTR activity. Furthermore, experiments conducted with wild type and NF-kappaB-mutated HIV-1 LTR-directed reporter vectors suggested that the positive action of Flu on HIV-1 LTR activity was mediated through the induction of NF-kappaB. Our data show that fully competent Flu can lead to NF-kappaB-dependent activation of HIV-1 transcription in CD4+ T cells.