An unusual cause of cerebellar ataxia in an immunocompromised elderly patient

Exploring the link between parvovirus B19 and encephalitis: a systematic review and comprehensive meta-analysis of molecular and serological evidence

Encephalitis, a severe brain inflammation, can arise due to various infectious agents, including viruses like Parvovirus B19 (B19V). Previously linked to mild neonatal and young one's illnesses and some haematological diseases, recent evidence associates B19V with encephalitis, with no clear prevalence and mechanisms in place. This systematic review and meta-analysis aim to determine the prevalence of B19V in cases of encephalitis, exploring variations associated with diagnostic approaches, and identifying gaps in existing research to enhance clinical comprehension and diagnostic methods. An extensive search (1994-2024) was performed through PubMed, Scopus, ScienceDirect, and Cochrane databases for research and epidemiological investigations related to B19V in cases of encephalitis. Inclusion criteria focused on studies that verified B19V using molecular (PCR, NGS) or serological (IgM/IgG) techniques in cerebrospinal fluid or serum. Data analysis was done to pool the prevalence data of included studies using a random-effects model. Heterogeneity was evaluated using I2 statistics. Sensitivity and meta-regression analyses were conducted to evaluate variability and the effects of moderators. A total of fourteen studies involving 3,135 encephalitis patients resulted in a combined prevalence of 3% (95% CI: 2-4%). Studies using PCR indicated a greater prevalence (3%) in comparison to ELISA (1%) and NGS (2%). A moderate level of heterogeneity (I2 = 57.4%) was attributed to the variability in diagnostic methods and geographic distribution. Sensitivity analyses validated strong estimates, while meta-regression revealed country as a key moderator accounting for heterogeneity. Publication bias was modest. The research indicates that B19V may be involved in certain encephalitis instances, with an overall prevalence of 3%. The differences observed in the studies emphasize the need for standardized diagnostic procedures and more extensive multicentric epidemiological research.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

The role of parvovirus B19 in the pathogenesis of autoimmunity and autoimmune disease

Human parvovirus B19 is a single-stranded DNA virus which preferentially targets the erythroblasts in the bone marrow. B19 infection commonly causes erythema infectiosum, arthralgia, fetal death, transient aplastic crisis in patients with shortened red cell survival, and persistent infection in people who are immunocompromised. Less common clinical manifestations include atypical skin rashes, neurological syndromes, cardiac syndromes, and various cytopenias. B19 infection has also been associated with development of a variety of different autoimmune diseases, including rheumatological, neurological, neuromuscular, cardiovascular, haematological, nephrological and metabolic. Production of a variety of autoantibodies has been demonstrated to occur during B19 infection and these have been shown to be key to the pathogenesis of the particular disease process in a significant number of cases, for example, production of rheumatoid factor in cases of B19-associated rheumatoid arthritis and production of anti-glutamic acid decarboxylase (GAD) in patients with B19-associated type 1 diabetes mellitus. B19 infection has also been associated with the development of multiple autoimmune diseases in 12 individuals. Documented mechanisms in B19-associated autoimmunity include molecular mimicry (IgG antibody to B19 proteins has been shown to cross react with a variety of recognised human autoantigens, including collagen II, keratin, angiotensin II type 1 receptor, myelin basic protein, cardiolipin, and platelet membrane glycoprotein IIb/IIIa), B19-induced apoptosis with presentation of self-antigens to T lymphocytes, and the phospholipase activity of the B19 unique VP1 protein.