Human Herpesvirus-6 Pneumonitis around the Engraftment of Cord Blood Transplantation following Foscarnet Prophylaxis in a Patient with Acute Leukemia

Post-allogeneic hematopoietic stem cell transplantation viral reactivations and viremias: a focused review on human herpesvirus-6, BK virus and adenovirus

Human cytomegalovirus and Epstein-Barr virus have been recognized as potential drivers of morbidity and mortality of patients undergoing allogeneic stem cell transplantation for years. Specific protocols for monitoring, prophylaxis and pre-emptive therapy are in place in many transplant settings. In this review, we focus on the next three most frequent viruses, human herpesvirus-6, BK virus and adenovirus, causing reactivation and/or viremia after allogeneic transplant, which are increasingly detected in patients in the post-transplant period owing to emerging techniques of molecular biology, recipients' characteristics, treatment modalities used for conditioning and factors related donors or stem cell source. Given the less frequent detection of an illness related to these viruses, there are often no specific protocols in place for the management of affected patients. While some patients develop significant morbidity (generally older), others may not need therapy at all (generally younger or children). Furthermore, some of the antiviral therapies used are potentially toxic. With the addition of increased risk of secondary infections, risk of graft failure or increased risk of graft-versus-host disease as well as the relationship with other post-transplant complications, the outcomes of patients with these viremias remain unsatisfactory and even long-term survivors experience increased morbidity.

Human herpes virus-6 (HHV-6) pneumonitis and meningitis with viraemia in an immunocompetent adult patient

Human herpes virus-6 (HHV-6) infection is a common infection in the paediatric population and is increasingly reported in immunosuppressed adult patients. It has been reported as the causative agent of disease in few case reports in immunocompetent adults. We report herein an unusual case of HHV-6-associated viraemia, pneumonitis and meningitis in a patient who presented with dyspnoea, hypoxia, dry cough and headache. She was treated for atypical pneumonia with no improvement. Meningitis was suspected as headache kept worsening. HHV-6B was detected by PCR in the cerebrospinal fluid, and subsequently, in the bronchoalveolar lavage and serum samples. Studies were negative for the most common primary and secondary immunodeficiency syndromes, and serology could not be performed to differentiate virus reactivation from a primary infection. The patient was successfully treated with ganciclovir and had no residual sequelae.

The Presence of Human Herpesvirus 6 in the Brain in Health and Disease

The human herpesvirus 6 (HHV-6) -A and -B are two dsDNA beta-herpesviruses infectingalmost the entire worldwide population. These viruses have been implicated in multipleneurological conditions in individuals of various ages and immunological status, includingencephalitis, epilepsy, and febrile seizures. HHV-6s have also been suggested as playing a role inthe etiology of neurodegenerative diseases such as multiple sclerosis and Alzheimer's disease. Theapparent robustness of these suggested associations is contingent on the accuracy of HHV-6detection in the nervous system. The effort of more than three decades of researching HHV-6 in thebrain has yielded numerous observations, albeit using variable technical approaches in terms oftissue preservation, detection techniques, sample sizes, brain regions, and comorbidities. In thisreview, we aimed to summarize current knowledge about the entry routes and direct presence ofHHV-6 in the brain parenchyma at the level of DNA, RNA, proteins, and specific cell types, inhealthy subjects and in those with neurological conditions. We also discuss recent findings relatedto the presence of HHV-6 in the brains of patients with Alzheimer's disease in light of availableevidence.

Human herpesvirus-6 pneumonitis in a patient with follicular lymphoma following immunochemotherapy with rituximab

Primary infection with human herpesvirus-6 (HHV-6) commonly occurs at an early age in children, most often at 3 years of age, and is associated with childhood diseases, such as exanthema subitum, hepatitis, febrile convulsions, or encephalitis. However, the virus occasionally reactivates from its latent state in immunosuppressed adults, especially post-transplant, resulting in serious disseminated, sometimes life-threatening end-organ complications. Herein, we report a case of a 68-year-old man with relapsed follicular lymphoma who developed HHV-6 pneumonitis. Eighteen months after achieving second complete remission by salvage immunochemotherapy with rituximab, the patient was complicated by pneumonia, with chest computed tomography finding showing disseminated nodular shadows with ground-glass opacity in both lungs. While empiric antibiotic and antifungal therapies did not improve the pneumonia, polymerase chain reaction–based viral screening tests on his bronchoalveolar lavage fluid detected the presence of HHV-6 DNA, and ganciclovir treatment quickly resolved the pneumonia, indicating that he suffered from HHV-6 pneumonitis. He had no other HHV-6–related end-organ damage, such as encephalitis. This case suggests that, although extremely rare, HHV-6 reactivation should be considered as one of the candidate pathogens for pulmonary complications of uncertain etiology in patients who have been treated with intensive immunosuppressive chemotherapy, even without hematopoietic stem cell transplantation. Furthermore, polymerase chain reaction–based viral screening testing on bronchoalveolar lavage fluid is a powerful diagnostic tool for pneumonitis due to viral reactivation, including HHV-6 reactivation.