Estimating hepatitis C infection acquired in England, 1986–2000

The immunity gap in primates

Vertebrates exhibit sexual dimorphism in response to infectious diseases and in morbidity and mortality rates to various pathogens. Females are generally more immunocompetent than males, despite their increased reproductive burden and the immunosuppressive effects of gestation. In addition, females generally have lower incidences of cancer compared to males; however, they have higher rates of autoimmune disorders. These sex differences may be a result of life history differences, sexual selection, genetics, and/or the physiological effects of hormones. As highly social mammals with complex life histories, primates offer a unique opportunity to investigate the evolution of enhanced female immunocompetence. This review aims to examine the evidence of this immunity gap, understand current hypotheses for its evolution, and explore the potential role of X chromosome specific genes and heterozygosity within this framework.

Theiler’s virus-induced demyelinating disease as an infectious model of progressive multiple sclerosis

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease of unknown etiology. However, several studies suggest that infectious agents, e.g., Human Herpes Viruses (HHV), may be involved in triggering the disease. Molecular mimicry, bystander effect, and epitope spreading are three mechanisms that can initiate immunoreactivity leading to CNS autoimmunity in MS. Theiler’s murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD) is a pre-clinical model of MS in which intracerebral inoculation of TMEV results in a CNS autoimmune disease that causes demyelination, neuroaxonal damage, and progressive clinical disability. Given the spectra of different murine models used to study MS, this review highlights why TMEV-IDD represents a valuable tool for testing the viral hypotheses of MS. We initially describe how the main mechanisms of CNS autoimmunity have been identified across both MS and TMEV-IDD etiology. Next, we discuss how adaptive, innate, and CNS resident immune cells contribute to TMEV-IDD immunopathology and how this relates to MS. Lastly, we highlight the sexual dimorphism observed in TMEV-IDD and MS and how this may be tied to sexually dimorphic responses to viral infections. In summary, TMEV-IDD is an underutilized murine model that recapitulates many unique aspects of MS; as we learn more about the nature of viral infections in MS, TMEV-IDD will be critical in testing the future therapeutics that aim to intervene with disease onset and progression.

Alzheimer's disease-related transcriptional sex differences in myeloid cells

Sex differences have been identified in many diseases associated with dysregulated immune responses, including Alzheimer's disease (AD), for which approximately two-thirds of patients are women. An accumulating body of research indicates that microglia may play a causal role in the pathogenesis of this disease. We hypothesised that sex differences in the transcriptome of human myeloid cells may contribute to the sex difference observed in AD prevalence. To explore this, we assessed bulk and single-nuclear RNA sequencing data sets generated from four human derived myeloid cell populations: post-mortem microglial nuclei, peripheral monocytes, monocyte-derived macrophages (MDMs) and induced pluripotent stem cell derived microglial-like cells (MGLs). We found that expression of AD risk genes, gene signatures associated with the inflammatory response in AD, and genes related to proinflammatory immune responses were enriched in microglial nuclei isolated from aged female donors without ante-mortem neurological disease, relative to those from males. In addition, these inflammation-associated gene sets were found to be enriched in peripheral monocytes isolated from postmenopausal women and in MDMs obtained from premenopausal individuals relative to age-matched males. Expression of these gene sets did not differ in MDMs derived from women whose blood was sampled across the menstrual cycle or in MGLs cultured with 17β-oestradiol. This suggests that the observed gene set enrichments in myeloid cells from women were not being driven by acute hormonal influences. Together, these data support the hypothesis that the increased prevalence of AD in women may be partly explained by a myeloid cell phenotype biased towards expression of biological processes relevant to AD.

Sex Differences in Immunity

Strong epidemiological evidence now exists that sex is an important biologic variable in immunity. Recent studies, for example, have revealed that sex differences are associated with the severity of symptoms and mortality due to coronavirus disease 2019 (COVID-19). Despite this evidence, much remains to be learned about the mechanisms underlying associations between sex differences and immune-mediated conditions. A growing body of experimental data has made significant inroads into understanding sex-influenced immune responses. As physicians seek to provide more targeted patient care, it is critical to understand how sex-defining factors (e.g., chromosomes, gonadal hormones) alter immune responses in health and disease. In this review, we highlight recent insights into sex differences in autoimmunity; virus infection, specifically severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection; and cancer immunotherapy. A deeper understanding of underlying mechanisms will allow the development of a sex-based approach to disease screening and treatment.

Determinants of HCV-related complications in Italian primary care patients

BACKGROUND AND AIMS

This study aimed to assess the demographic and clinical determinants of liver complications in Hepatitis C virus (HCV)-positive patients in primary care setting.

METHODS

Using the Health Search database, we selected a cohort of patients aged ≥14 diagnosed with HCV between 2002 and 2017. Patients were followed up until the occurrence of cirrhosis and other disease progressions such as oesophageal varices, hepatocellular carcinoma and/or liver transplantation. The candidate determinants for the risk of HCV-related complications included sex, age, smoking status, liver fibrosis (measured by fibrosis 4 index [FIB-4]), infections by the human immunodeficiency virus (HIV), hepatitis B virus (HBV), other forms of hepatitis, abuse of alcohol or illicit substances or drugs, obesity, metabolic syndrome, diabetes mellitus and renal disease. Cox regression was used to test the association between candidate determinants and the outcome.

RESULTS

The cohort included 8299 HCV-positive patients (50.93% men) with an overall prevalence rate equal to 0.61%. At least one HCV-related complication was found in 12.2% of patients, with a mean time-to-event equal to 8.1 year. Along with male sex and advanced age, a FIB-4 greater than 3.25 and the presence of diabetes were associated with a greater risk of HCV-related complications.

CONCLUSION

Our study shows that patients with certain demographics and clinical characteristics are more prone to incur in HCV-related complications. The knowledge and early identification of these determinants by GPs may result in reducing disease progression and related healthcare costs through a closer monitoring.

Sex Differences in Immunity to Viral Infections

The ongoing COVID-19 pandemic has increased awareness about sex-specific differences in immunity and outcomes following SARS-CoV-2 infection. Strong evidence of a male bias in COVID-19 disease severity is hypothesized to be mediated by sex differential immune responses against SARS-CoV-2. This hypothesis is based on data from other viral infections, including influenza viruses, HIV, hepatitis viruses, and others that have demonstrated sex-specific immunity to viral infections. Although males are more susceptible to most viral infections, females possess immunological features that render them more vulnerable to distinct immune-related disease outcomes. Both sex chromosome complement and related genes as well as sex steroids play important roles in mediating the development of sex differences in immunity to viral infections.

Dissecting the decline of hepatitis C in first-time donors in England and Wales

BACKGROUND AND OBJECTIVES

The rate of confirmed hepatitis C virus (HCV) cases, in first-time donors, is much lower in 2015 than 20 years ago. We investigate reasons for the decline.

MATERIALS AND METHODS

HCV rates were analysed by gender and birth cohort for 1996 to 2015 and ethnic group for 2006 to 2015. Variables for confirmed positive cases were compared for two ten-year periods (1996 to 2005 and 2006 to 2015) including genotyping data for 2006 to 2015.

RESULTS

There were 2007 confirmed HCV cases identified between 1996 and 2015. The rate per 100 000 donations fell from 78·6 in 1996 to 26·9 by 2015. By birth cohort, HCV rates were highest in donors born in the 1950s and 1960s who contributed a decreasing proportion of first-time donors. Between 2006 and 2015, there was no significant decline in HCV rate. The HCV-positive donor profile has changed in the last 10 years with increased proportions of younger donors, donors born abroad and decreased reported injecting drug use. Genotype 1a remains predominate, but genotype 1b has increased associated with this change in birth cohort and ethnicity.

CONCLUSION

The decline in number and rate of confirmed HCV-positive first-time donors is mainly due to a decrease in first-time donors born before 1970, with the highest rate of HCV. However, the decline has slowed and the profile of HCV-positive first-time donors is changing. A better understanding of behaviour and sources of HCV in younger and ethnic minority donors are needed.

Systematic analysis of funding awarded for viral hepatitis-related research to institutions in the United Kingdom, 1997-2010

Viral hepatitis is responsible for great health, social and economic burden both globally and in the UK. This study aimed to assess the research funding awarded to UK institutions for viral hepatitis research and the relationship of funded research to clinical and public health burden of viral hepatitis. Databases and websites were systematically searched for information on infectious disease research studies funded for the period 1997-2010. Studies specifically related to viral hepatitis research were identified and categorized in terms of funding by pathogen, disease and by a research and development value chain describing the type of science. The overall data set included 6165 studies (total investment £2.6 billion) of which £76.9 million (3.0%) was directed towards viral hepatitis across 323 studies (5.2%). By pathogen, there were four studies specifically investigating hepatitis A (£3.8 million), 69 studies for hepatitis B (21.4%) with total investment of £14.7 million (19.1%) and 236 (73.1%) hepatitis C studies (£62.7 million, 81.5%). There were 4 studies investigating hepatitis G, and none specifying hepatitis D or E. By associated area, viral hepatitis and therapeutics research received £17.0 million, vaccinology £3.1 million and diagnostics £2.9 million. Preclinical research received £50.3 million (65.4%) across 173 studies, whilst implementation and operational research received £19.4 million (25.3%) across 128 studies. The UK is engaged in much hepatology research, but there are areas where the burden is great and may require greater focus, such as hepatitis E, development of a vaccine for hepatitis C, and further research into hepatitis-associated cancers. Private sector data, and funding information from other countries, would also be useful in priority setting.

Sexual dimorphism in immunity: improving our understanding of vaccine immune responses in men

Weaker immune responses are often observed in males compared to females. Since female hormones have proinflammatory properties and androgens have potent immunomodulatory effects, this sexual dimorphism in the immune response seems to be hormone dependent. Despite our current knowledge about the effect of sex hormones on immune cells, definition of the factors driving the sex differences in immunoclinical outcomes, such as the diminished response to infection and vaccination observed in men or the higher rates of autoimmunity observed in females, remains elusive. Recently, systems approaches to immune function have started to suggest a way toward establishing this connection. Such studies promise to improve our understanding of the mechanisms underlying the sexual dimorphism observed in the human immune system.

Sex differences in prophylaxis and therapeutic treatments for viral diseases

The intensity and prevalence of viral infections are typically higher in males than in females. In contrast, disease outcome can be worse for females. Males and females also differ in their responses to prophylaxis and therapeutic treatments for viral diseases. In response to vaccines against herpes viruses, hepatitis viruses, influenza viruses, and others, females consistently mount higher humoral immune responses and experience more frequent and severe adverse reactions than males. Males and females also differ in the absorption, metabolism, and clearance of antiviral drugs. The pharmacological effects, including toxicity and adverse reactions, of antiviral drugs are typically greater in females than males. The efficacy of antiviral drugs at reducing viral load also differs between the sexes, with antiviral treatments being better at clearing HIV and hepatitis C virus in females, but showing greater reduction of herpes simplex virus and influenza A virus loads in males. Biological variables, including hormone and genes, as well as gender-specific factors related to access and compliance to drug regimens must be considered when evaluating male-female differences in responses to treatments for viral diseases. Clinicians, epidemiologists, and basic biomedical scientists should design experiments that include both males and females, develop a priori hypotheses that the sexes will differ in their responses to and the outcome of vaccines and antiviral treatments, and statistically analyze outcome data by sex. Knowledge that the sexes differ in response to prophylaxis and therapeutic treatments for viral diseases should influence the recommended course of treatment differently for males and females.

A population-based study of the epidemiology of hepatitis C in a North American population

BACKGROUND & AIMS

Chronic hepatitis C virus (HCV) infection is a major public health problem with approximately 3% of the world's population thought to be chronically infected. However, population-based data regarding HCV incidence rates, prevalence, residence, age, and gender distributions within North America are limited. We aimed at providing a detailed descriptive epidemiology of HCV infection in a North American population with a focus on time trends in incidence rates and prevalence of newly diagnosed HCV infection since 1991, the time when laboratory testing for HCV infections became first available.

METHODS

A Research Database was developed linking records from multiple administrative sources. HCV positive residents of the Canadian province of Manitoba were identified during a twelve-year period (1991-2002). The cumulative and annual incidence rates and the prevalence of newly diagnosed HCV infection in Manitoba were examined and compared between different demographic groups and urban vs. rural residents.

RESULTS

A total of 5018 HCV positive cases were identified over a 12-year period. The annual number of newly diagnosed HCV infections peaked in 1998 (59.2/100,000). On the other hand, the known prevalence of HCV continued to increase (4.6-fold during the 12-year study period) among both men and women reflecting the chronic nature of the disease. Males were 1.7 times more often infected than females. HCV infections were more common in urban centers.

CONCLUSIONS

Between 1995 and 2002, there was a fairly constant trend for newly diagnosed HCV infection, ranging from approximately 500 to 600 new cases annually. Hence, with a stable population size, and a low case fatality rate, the prevalence of HCV infected persons in our population has been steadily rising. There is no evidence to suggest that the incidence of HCV infection will raise, however, the burden of chronic HCV infection will continue to increase, particularly amongst older males and those residing in urban centers.

Sex influences immune responses to viruses, and efficacy of prophylaxis and treatments for viral diseases

The intensity and prevalence of viral infections are typically higher in males, whereas disease outcome can be worse for females. Females mount higher innate and adaptive immune responses than males, which can result in faster clearance of viruses, but also contributes to increased development of immunopathology. In response to viral vaccines, females mount higher antibody responses and experience more adverse reactions than males. The efficacy of antiviral drugs at reducing viral load differs between the sexes, and the adverse reactions to antiviral drugs are typically greater in females than males. Several variables should be considered when evaluating male/female differences in responses to viral infection and treatment: these include hormones, genes, and gender-specific factors related to access to, and compliance with, treatment. Knowledge that the sexes differ in their responses to viruses and to treatments for viral diseases should influence the recommended course of action differently for males and females. Editor's suggested further reading in BioEssays X-chromosome-located microRNAs in immunity: Might they explain male/female differences Abstract.

A systematic review of hepatitis C virus epidemiology in Europe, Canada and Israel

BACKGROUND AND AIM

Decisions on public health issues are dependent on reliable epidemiological data. A comprehensive review of the literature was used to gather country-specific data on risk factors, prevalence, number of diagnosed individuals and genotype distribution of the hepatitis C virus (HCV) infection in selected European countries, Canada and Israel.

METHODOLOGY

Data references were identified through indexed journals and non-indexed sources. In this work, 13,000 articles were reviewed and 860 were selected based on their relevance.

RESULTS

Differences in prevalence were explained by local and regional variances in transmission routes or different public health measures. The lowest HCV prevalence (≤ 0.5%) estimates were from northern European countries and the highest (≥ 3%) were from Romania and rural areas in Greece, Italy and Russia. The main risk for HCV transmission in countries with well-established HCV screening programmes and lower HCV prevalence was injection drug use, which was associated with younger age at the time of infection and a higher infection rate among males. In other regions, contaminated glass syringes and nosocomial infections continue to play an important role in new infections. Immigration from endemic countries was another factor impacting the total number of infections and the genotype distribution. Approximately 70% of cases in Israel, 37% in Germany and 33% in Switzerland were not born in the country. In summary, HCV epidemiology shows a high variability across Europe, Canada and Israel.

CONCLUSION

Despite the eradication of transmission by blood products, HCV infection continues to be one of the leading blood-borne infections in the region.