Dimeric IgA is a specific biomarker of recent SARS-CoV-2 infection

Current tests for SARS-CoV-2 antibodies (IgG, IgM, IgA) cannot differentiate recent and past infections. We describe a point of care, lateral flow assay for SARS-CoV-2 dIgA based on the highly selective binding of dIgA to a chimeric form of secretory component (CSC), that distinguishes dIgA from monomeric IgA. Detection of specific dIgA uses a complex of biotinylated SARS-CoV-2 receptor binding domain and streptavidin-colloidal gold. SARS-CoV-2-specific dIgA was measured both in 112 cross-sectional samples and a longitudinal panel of 362 plasma samples from 45 patients with PCR-confirmed SARS-CoV-2 infection, and 193 discrete pre-COVID-19 or PCR-negative patient samples. The assay demonstrated 100% sensitivity from 11 days post-symptom onset, and a specificity of 98.2%. With an estimated half-life of 6.3 days, dIgA provides a unique biomarker for the detection of recent SARS-CoV-2 infections with potential to enhance diagnosis and management of COVID-19 at point-of-care.

Frequent occurrence of low-level positive autoantibodies in chronic hepatitis C

Evidence of autoimmune disease associated with hepatitis C virus (HCV)-infection has important clinical implications. A systematic profile of these autoantibodies in relevant clinical cohorts relative to healthy controls is needed to better inform current standard of care for chronic hepatitis C. Samples from an Australian cohort of chronic HCV-infected subjects (n=127) were tested for the presence of 19 diagnostic autoantibodies and compared with data available from a control cohort representing a general Caucasian population (n=198). Chronic HCV-infected individuals had a greater number of autoantibodies than controls (p<0.0001). Anti-nuclear antibodies (ANA) followed by anti-smooth muscle antibodies (SMA) were the most frequently detected autoantibodies within the HCV cohort and significantly more than in the control cohort (p<0.0001 and p=0.006, respectively). However, for most autoantibody assays the 95th percentile approximated the reference value for positivity. None of the autoantibodies were significantly associated with age or sex for the HCV cohort, except SMA positivity that was significantly higher in chronic HCV-infected male subjects (p<0.0001). Autoantibodies found in chronic HCV-infected subjects were commonly low positive and not disease-specific. Accordingly, general screening for autoimmunity in HCV-infected subjects should not be performed unless there is high clinical suspicion of an underlying autoimmune disease.

Detection of HCV-Specific IFN-γ Responses in HCV Antibody and HCV RNA Negative Injecting Drug Users

BACKGROUND

Detectable HCV-specific cellular immune responses in HCV antibody and RNA negative people who inject drugs (PWID) raise the question of whether some are resistant to HCV infection. Immune responses from people who have been exposed to hepatitis C virus (HCV) and remain anti-HCV negative are of interest for HCV vaccine development; however, limited research addresses this area.

OBJECTIVES

In a cohort of HCV antibody and RNA negative PWID, we assessed whether the presence of HCV-specific IFN-γ responses or genetic associations provide any evidence of protection from HCV infection.

PATIENTS AND METHODS

One hundred and ninety-eight participants were examined longitudinally for clinical, behavioral, social, environmental and genetic characteristics (IFNL3 genotype [formally IL-28B] and HLA type). Sixty-one of the 198 participants were HCV antibody and RNA negative, with 53 able to be examined longitudinally for HCV-specific IFN-γ ELISpot T cell responses.

RESULTS

Ten of the 53 HCV antibody and RNA negative participants had detectable HCV-specific IFN-γ responses at baseline (18%). The magnitude of IFN-γ responses averaged 131 +/- 96 SFC/106 PBMC and the breadth was mean 1 +/- 1 pool positive. The specificity of responses were mainly directed to E2, NS4b and NS5b. Participants with (10) and without (43) HCV-specific IFN-γ responses did not differ in behavioral, clinical or genetic characteristics (P > 0.05). There was a larger proportion sharing needles (with 70%, without 49%, P = 0.320) and a higher incidence of HCV (with 35.1 per 100 py, 95% CI 14.6, 84.4, without 16.0 per 100 py, 95% CI 7.2, 35.6, P = 0.212) in those with IFN-γ responses, although not statistically significant. Half the participants with baseline IFN-γ responses became HCV RNA positive (5/10), with one of these participants spontaneously clearing HCV. The spontaneous clearer had high magnitude and broad Th1 responses, favorable IFNL3 genotype and favorable HLA types.

CONCLUSIONS

This study demonstrated the detection of HCV-specific IFN-γ responses in HCV antibody and RNA negative individuals, with a tendency for HCV-specific IFN-γ responses to be associated with HCV exposure. The potential role of HCV-specific IFN-γ responses in those who remained HCV RNA negative is of value for the development of novel HCV therapeutics.

Incidence of primary hepatitis C infection and risk factors for transmission in an Australian prisoner cohort

BACKGROUND

Hepatitis C virus (HCV) infection is common in prisoner populations, particularly those with a history of injecting drug use (IDU). Previous studies of HCV incidence have been based on small case numbers and have not distinguished risk events in prison from those in the community.

METHODS

HCV incidence was examined in a longitudinal cohort of 488 Australian prisoners with a history of IDU and documented to be seronegative within 12 months prior to enrollment. Inmates were tested for anti-HCV antibodies and viremia, and interviewed about demographic and behavioral risk factors for transmission.

RESULTS

The cohort was predominantly male (65%) with high rates of prior imprisonment (72%) and tattooing (73%), as well as longstanding IDU (mean 8.5 years). Ninety-four incident HCV cases were identified (incidence 31.6 per 100 person years). Independent associations were observed between incident infection and prior imprisonment (p = 0.02) and tattooing (p = 0.03), and surprisingly also with methadone maintenance treatment (MMT) (p < 0.001).

CONCLUSIONS

High rates of new HCV infection were found in this prisoner cohort reflecting their substantive risk behavior profile, despite having remained uninfected for many years. The association with MMT is challenging and highlights the need for better understanding of prison-specific HCV transmission risks, as well as the uptake and effectiveness of prevention programs.

Effective treatment of injecting drug users with recently acquired hepatitis C virus infection

BACKGROUND & AIMS

Patients with acute hepatitis C virus (HCV) infection who receive treatment achieve high rates of sustained virologic response (SVR), but few studies have examined outcomes among injecting drug users (IDUs). We evaluated the efficacy of treatment of recent HCV infection in IDUs with acute and early chronic HCV.

METHODS

We analyzed data from the Australian Trial in Acute Hepatitis C-a prospective study of the natural history and treatment outcomes of patients with recent HCV infection. Participants eligible for the study had their first anti-HCV antibody-positive test result within the past 6 months and either acute clinical HCV within the past 12 months or documented anti-HCV seroconversion within 24 months. Participants with HCV received pegylated interferon-alfa-2a (180 microg/wk, n = 74); those with HCV/human immunodeficiency virus (HIV) co-infection received pegylated interferon-alfa-2a (180 microg/wk) with ribavirin (n = 35) for 24 weeks.

RESULTS

From June 2004 to February 2008, 167 participants were enrolled in the Australian Trial in Acute Hepatitis C; 79% had injected drugs in the previous 6 months. Among 74 with only HCV, the SVRs were 55% and 72% by intention-to-treat and per-protocol analysis, respectively. In multivariate analyses, baseline factors independently associated with lower SVR included decreased social functioning and current opiate pharmacotherapy. Adherent participants had higher SVR rates (63% vs 29%; P = .025). Of the 35 participants with HCV/HIV co-infection, the SVRs were 74% and 75% by intention-to-treat and per-protocol analysis, respectively.

CONCLUSIONS

Treatment of recent HCV infection among IDUs, including those with HIV co-infection, is effective. Strategies to engage socially marginalized individuals and increase adherence should improve treatment outcomes in this population.

Heterosubtypic T-cell responses against avian influenza H5 haemagglutinin are frequently detected in individuals vaccinated against or previously infected with human subtypes of influenza

Background  Cellula r immune responses play a critical role in providing help for the production of neutralizing antibodies to influenza virus, as well as producing anti‐viral cytokines and killing infected cells in the lung. Heterosubtypic T‐cell responses between different subtypes of influenza have been shown to exist in humans and to provide protection against morbidity and mortality associated with H5N1 infection in animal challenge models. Therefore, existing T‐cell responses induced by natural infection or vaccination in humans may provide some degree of protection from infection with H5N1 strains, or may attenuate the severity of disease.

Objectives  To investigate heterosubtypic T‐cell responses to avian influenza in humans.

Methods  T‐cell responses to an overlapping set of H5 HA peptides and inactivated viruses (H1N1, H3N2 and H5N1) were assessed using IFN‐γ and IL‐2 enzyme‐linked immunospot (ELISpot) assays in a cohort of adults either vaccinated against seasonal influenza in the last 3 years (n = 20) or previously infected (n = 40).

Results  T‐cell responses to all three subtypes of virus were found in both infected and vaccinated individuals by IFN‐γ and IL‐2 ELISpot assays. Approximately half of the participants from each group had a positive T‐cell response to the H5 HA peptides in the IFN‐γ or IL‐2 ELISpot assay.

Conclusions  Heterosubtypic T‐cell responses to H5 HA occur quite frequently in vaccinated and infected individuals. Further investigation of these responses and what role they may play upon challenge or vaccination against H5N1 may assist in vaccine design for avian influenza.

Prolonged Illness after Infectious Mononucleosis Is Associated with Altered Immunity but Not with Increased Viral Load

BACKGROUND

Primary Epstein-Barr virus (EBV) infection causes a spectrum of characteristics that range from asymptomatic seroconversion to severe infectious mononucleosis (IM), sometimes with prolonged symptoms and disability. We examined the relationships between clinical course, number of viral copies, and immunological parameters in a prospective cohort of subjects with recent IM.

METHODS

Eight case patients with at least 6 months of disabling symptoms and 31 matched control subjects who had recovered promptly were included. Symptom scores were recorded at regular intervals over the course of 12 months. Cellular EBV load, EBV-specific antibody responses, lymphocyte subsets, and EBV-specific interferon (IFN)- gamma induction were measured.

RESULTS

In case patients with prolonged illness, the severity of acute-phase symptoms was greater, the development of anti-EBV nuclear antigen-1 immunoglobulin G was more rapid, and the time to development of the peak IFN- gamma response to the majority of latent-cycle EBV peptides was generally slower than those in control subjects. However, in both groups, neither viral nor immune parameters correlated with the severity or duration of symptoms.

CONCLUSIONS

The resolution of symptomatic IM is not determined by control of viremia, nor is it easily explained by altered host responses to EBV infection. The detailed determinants of delayed recovery remain to be elucidated.

A randomized, placebo-controlled phase I trial of DNA prime, recombinant fowlpox virus boost prophylactic vaccine for HIV-1

An HIV-vaccine consisting of a DNA prime, recombinant fowlpox virus (rFPV) boost was evaluated in a double-blind placebo controlled trial. One milligram of pHIS-HIV-B expressing mutated gag, pol, env, vpu, tat and rev was administered at weeks 0 and 4 boosted by 5 x 10(7) pfu rFPV-HIV-B expressing gag/pol at week 8. The vaccine regimen was safe, but there was no difference between vaccine (n = 18) and placebo recipients (n = 6) for Gag or Pol-specific T-cell immune responses at week 9.

Evaluation in macaques of HIV-1 DNA vaccines containing primate CpG motifs and fowlpoxvirus vaccines co-expressing IFN? or IL-12

Induction of HIV-specific T-cell responses by vaccines may facilitate efficient control of HIV. Plasmid DNA vaccines and recombinant fowlpoxvirus (rFPV) vaccines are promising HIV-1 vaccine candidates, although either vaccine alone may be insufficient to protect against HIV-1. A consecutive immunisation strategy involving priming with DNA and boosting with rFPV vaccines encoding multiple common HIV-1 antigens was further evaluated in 30 macaques. The DNA vaccine vector included CpG immunostimulatory molecules, and rFPV vaccines were compared with rFPV vaccines co-expressing the pro-T cell cytokines IFNgamma or IL-12. Vaccines expressed multiple HIV-1 genes, mutated to remove active sites of the HIV proteins. The vaccines were well tolerated, and a significant enhancement of DNA-vaccine primed HIV-1 specific T lymphocyte responses was observed following rFPV boosting. Co-expression of IFNgamma or IL-12 by the rFPV vaccines did not further enhance immune responses. Non-sterilising protection from a non-pathogenic HIV-1 challenge was observed. This study provides evidence of a safe, optimised, strategy for the generation of T-cell mediated immunity to HIV-1.

Carrier identification in X-linked immunodeficiency diseases

OBJECTIVE

Carrier identification in X-linked immunodeficiency disorders can be based on the demonstration of non-random X inactivation (NRXI) in affected blood cell lineages when growth is impaired in cells expressing the abnormal gene. We examined the utility of seeking evidence of NRXI to test the carrier status of women in families affected by X-linked severe combined immunodeficiency (XSCID) and X-linked hypogammaglobulinaemia (XLH), to identify as carriers the mothers of boys with SCID or hypogammaglobulinaemia whose phenotype suggested X-linkage and to infer X-linkage in boys with SCID or hypogammaglobulinaemia whose disease was not clearly X-linked on the basis either of family history or clinical and immunological characteristics.

METHODOLOGY

A polymerase chain reaction-based method was used to amplify a polymorphic CAG repeat in the first exon of the androgen receptor gene after selective digestion of the active X chromosome with a methylation-sensitive enzyme, HpaII to distinguish between the paternal and maternal alleles and to identify their methylation status.

RESULTS

Heterozygosity was found in 24 of 31 female subjects (77%). As anticipated, NRXI could be demonstrated in all lymphoid cells studied from obligate carriers of XSCID and an obligate carrier of XLH but not on a carrier of X-linked immunodeficiency with hyper-IgM. The finding of NRXI in the mother of a boy with a SCID variant showed her to be a carrier of XSCID and establishes that her son has XSCID, not otherwise evident from available data.

CONCLUSIONS

This PCR assay provides a rapid method for carrier detection of X-linked immunodeficiencies, and has allowed us to expand the phenotype of XSCID

Managing HIV. Part 3. Mechanisms of disease. 3.2 How HIV produces immune deficiency

Initially, the immune system controls HIV infection, but over time the virus depletes the population of CD4+ T cells and disturbs the homoeostasis and function of other cells in the immune system. Extensive destruction of the immune system eventually leaves the body defenceless.