Case report: oseltamivir-induced resistant pandemic influenza A (H1N1) virus infection in a patient with AIDS and Pneumocystis jirovecii pneumonia

Pneumocystis jirovecii Pneumonia after Heart Transplantation: Two Case Reports and a Review of the Literature

Post-transplant Pneumocystis jirovecii pneumonia (PcP) is an uncommon but increasingly reported disease among solid organ transplantation (SOT) recipients, associated with significant morbidity and mortality. Although the introduction of PcP prophylaxis has reduced its overall incidence, its prevalence continues to be high, especially during the second year after transplant, the period following prophylaxis discontinuation. We recently described two cases of PcP occurring more than one year after heart transplantation (HT) in patients who were no longer receiving PcP prophylaxis according to the local protocol. In both cases, the disease was diagnosed following the diagnosis of a viral illness, resulting in a significantly increased risk for PcP. While current heart transplantation guidelines recommend Pneumocystis jirovecii prophylaxis for up to 6-12 months after transplantation, after that period they only suggest an extended prophylaxis regimen in high-risk patients. Recent studies have identified several new risk factors that may be linked to an increased risk of PcP infection, including medication regimens and patient characteristics. Similarly, the indication for PcP prophylaxis in non-HIV patients has been expanded in relation to the introduction of new medications and therapeutic regimens for immune-mediated diseases. In our experience, the first patient was successfully treated with non-invasive ventilation, while the second required tracheal intubation, invasive ventilation, and extracorporeal CO2 removal due to severe respiratory failure. The aim of this double case report is to review the current timing of PcP prophylaxis after HT, the specific potential risk factors for PcP after HT, and the determinants of a prompt diagnosis and therapeutic approach in critically ill patients. We will also present a possible proposal for future investigations on indications for long-term prophylaxis.

Pathogenesis of Respiratory Viral and Fungal Coinfections

Individuals suffering from severe viral respiratory tract infections have recently emerged as "at risk" groups for developing invasive fungal infections. Influenza virus is one of the most common causes of acute lower respiratory tract infections worldwide. Fungal infections complicating influenza pneumonia are associated with increased disease severity and mortality, with invasive pulmonary aspergillosis being the most common manifestation. Strikingly, similar observations have been made during the current coronavirus disease 2019 (COVID-19) pandemic. The copathogenesis of respiratory viral and fungal coinfections is complex and involves a dynamic interplay between the host immune defenses and the virulence of the microbes involved that often results in failure to return to homeostasis. In this review, we discuss the main mechanisms underlying susceptibility to invasive fungal disease following respiratory viral infections. A comprehensive understanding of these interactions will aid the development of therapeutic modalities against newly identified targets to prevent and treat these emerging coinfections.

Pulmonary coinfection by Pneumocystis jirovecii and Cryptococcus species in a patient with undiagnosed advanced HIV

Pneumocystis jirovecii is a common cause of pneumonia in patients with advanced HIV. In a lot of cases, there is a concomitant pulmonary infection. Cryptococcosis presents as a common complication for people with advanced HIV. However, it usually presents as meningitis rather than pneumonia. We present a case of a patient with coinfection by P. jirovecii and Cryptococcus spp without neurological involvement and a single nodular pulmonary lesion.

Pulmonary complications of influenza infection: a targeted narrative review

Severe influenza infection represents a leading cause of global morbidity and mortality. Several clinical syndromes that involve a number of organs may be associated with Influenza infection. However, lower respiratory complications remain the most common and serious sequel of influenza infection. These include influenza pneumonia, superinfection with bacteria and fungi, exacerbation of underlying lung disease and ARDS. This review analyzes the available literature on the epidemiology and clinical considerations of these conditions. It also provides an overview of the effects of type of influenza, antiviral therapy, vaccination and other therapies on the outcome of these complications.

A Molecular Window into the Biology and Epidemiology of Pneumocystis spp

Pneumocystis, a unique atypical fungus with an elusive lifestyle, has had an important medical history. It came to prominence as an opportunistic pathogen that not only can cause life-threatening pneumonia in patients with HIV infection and other immunodeficiencies but also can colonize the lungs of healthy individuals from a very early age. The genus Pneumocystis includes a group of closely related but heterogeneous organisms that have a worldwide distribution, have been detected in multiple mammalian species, are highly host species specific, inhabit the lungs almost exclusively, and have never convincingly been cultured in vitro, making Pneumocystis a fascinating but difficult-to-study organism. Improved molecular biologic methodologies have opened a new window into the biology and epidemiology of Pneumocystis. Advances include an improved taxonomic classification, identification of an extremely reduced genome and concomitant inability to metabolize and grow independent of the host lungs, insights into its transmission mode, recognition of its widespread colonization in both immunocompetent and immunodeficient hosts, and utilization of strain variation to study drug resistance, epidemiology, and outbreaks of infection among transplant patients. This review summarizes these advances and also identifies some major questions and challenges that need to be addressed to better understand Pneumocystis biology and its relevance to clinical care.

Influenza and Pneumocystis jirovecii pneumonia in an allogeneic hematopoietic stem cell transplantation recipient: Coinfection or superinfection?

Influenza infection and Pneumocystis jirovecii pneumonia (PJP) in hematopoietic stem cell transplant (HSCT) patients are well characterized; however, no dual infections have been reported in this patient population and little evidence of mechanisms of interaction between the two infections exists. We present a 53-year-old male allogeneic HSCT patient on immunosuppressive therapy for the treatment of graft versus host disease initially diagnosed with influenza A H3 and later PJP. Despite the development of acute respiratory distress syndrome, the patient was successfully treated with appropriate antimicrobial therapy and aggressive supportive care. This case demonstrates the necessity of maintaining a high index of suspicion for fungal (including PJP) coinfection or superinfection in the setting of worsening influenza infection.

Discovery of dapivirine, a nonnucleoside HIV-1 reverse transcriptase inhibitor, as a broad-spectrum antiviral against both influenza A and B viruses

The emergence of multidrug-resistant influenza viruses poses a persistent threat to public health. The current prophylaxis and therapeutic interventions for influenza virus infection have limited efficacy due to the continuous antigenic drift and antigenic shift of influenza viruses. As part of our ongoing effort to develop the next generation of influenza antivirals with broad-spectrum antiviral activity and a high genetic barrier to drug resistance, in this study we report the discovery of dapivirine, an FDA-approved HIV nonnucleoside reverse transcriptase inhibitor, as a broad-spectrum antiviral against multiple strains of influenza A and B viruses with low micromolar efficacy. Mechanistic studies revealed that dapivirine inhibits the nuclear entry of viral ribonucleoproteins at the early stage of viral replication. As a result, viral RNA and protein synthesis were inhibited. Furthermore, dapivirine has a high in vitro genetic barrier to drug resistance, and its antiviral activity is synergistic with oseltamivir carboxylate. In summary, the in vitro antiviral results of dapivirine suggest it is a promising candidate for the development of the next generation of dual influenza and HIV antivirals.

Impact of HIV on the severity of influenza

Despite current antiretroviral therapy, HIV/AIDS is one of the most prelevant problems in healthcare worldwide. Similarly, influenza viruses are causes of epidemics outbreaks. HIV-infected patients are considered a high risk group for severe influenza infection, although several recent observational studies suggest that not all HIV-infected patients are equally susceptible to complications and that these patients should be stratified by their immunodeficiency status and other factors (such as smoking or comorbidities). Here, we have compiled the most recent data on the impact that HIV has on influenza infection.

Assessment of influenza virus hemagglutinin stalk-based immunity in ferrets

Therapeutic monoclonal antibodies that target the conserved stalk domain of the influenza virus hemagglutinin and stalk-based universal influenza virus vaccine strategies are being developed as promising countermeasures for influenza virus infections. The pan-H1-reactive monoclonal antibody 6F12 has been extensively characterized and shows broad efficacy against divergent H1N1 strains in the mouse model. Here we demonstrate its efficacy against a pandemic H1N1 challenge virus in the ferret model of influenza disease. Furthermore, we recently developed a universal influenza virus vaccine strategy based on chimeric hemagglutinin constructs that focuses the immune response on the conserved stalk domain of the hemagglutinin. Here we set out to test this vaccination strategy in the ferret model. Both strategies, pretreatment of animals with a stalk-reactive monoclonal antibody and vaccination with chimeric hemagglutinin-based constructs, were able to significantly reduce viral titers in nasal turbinates, lungs, and olfactory bulbs. In addition, vaccinated animals also showed reduced nasal wash viral titers. In summary, both strategies showed efficacy in reducing viral loads after an influenza virus challenge in the ferret model.

IMPORTANCE

Influenza virus hemagglutinin stalk-reactive antibodies tend to be less potent yet are more broadly reactive and can neutralize seasonal and pandemic influenza virus strains. The ferret model was used to assess the potential of hemagglutinin stalk-based immunity to provide protection against influenza virus infection. The novelty and significance of the findings described in this report support the development of vaccines stimulating stalk-specific antibody responses.

Influenza virus hemagglutinin stalk-based antibodies and vaccines

Antibodies against the conserved stalk domain of the hemagglutinin are currently being discussed as promising therapeutic tools against influenza virus infections. Because of the conservation of the stalk domain these antibodies are able to broadly neutralize a wide spectrum of influenza virus strains and subtypes. Broadly protective vaccine candidates based on the epitopes of these antibodies, for example, chimeric and headless hemagglutinin structures, are currently under development and show promising results in animals models. These candidates could be developed into universal influenza virus vaccines that protect from infection with drifted seasonal as well as novel pandemic influenza virus strains therefore obviating the need for annual vaccination, and enhancing our pandemic preparedness.