A transfusion-transmitted hepatitis B virus (HBV) infection caused by blood only positive for anti-hepatitis B surface antigen (anti-HBs) was reported. Occult HBV infection (OBI) with sole anti-HBs among blood donors is an issue. The incidence of HBV infection among repeat blood donors was investigated with a detailed HBV infection phase, focusing on the influence of anti-HBs level. This study followed 3 435 653 donors for HBV DNA conversion over 4 years and 9 months. Infection phase was determined based on marker changes over DNA conversion. This study identified 115 hepatitis B surface antigen (HBsAg) conversions, 72 DNA-only conversions, and 15 DNA plus anti-hepatitis B core (anti-HBc) conversions among donors all negative for HBV DNA, HBsAg, and anti-HBc. Total incidence was 2.38/100 000 person-years (PY). None of these 202 new HBV infections arose in the group with anti-HBs titer ≥ 10 mIU/mL. In total, 30 anti-HBc-negative OBIs were identified (incidence; 0.35/100 000 PY); 7 showed typical secondary anti-HBs response, and 23 showed stable anti-HBc and anti-HBs levels at DNA conversion. The HBV infection-protective ability of anti-HBs ≥ 10 mIU/mL was reinforced. In addition to new infections, the blood donor population includes anti-HBc-positive- and negative OBI with immune reactions or abortive HBV infection.

BACKGROUND: Accurate laboratory confirmation for Hepatitis B diagnosis and monitoring are crucial. Recently an ultrasensitive immunoassay test, the HBsAg Next (HBsAgNx), has been reported approximately eight times more sensitive than current HBsAg assays. The aim of our study was to assess the analytical performances of this new test.
METHODS: 253 clinical samples from Saint Louis University Hospital were analyzed, splitted into four panels: (1) routine prospectively screening serums (n = 196), (2) retrospective serum samples before HBV reactivation (HBV-R) (n = 18), (3) occult HBV infection (OBI) (n = 10) and (4) a selection of wild type HBV genotypes (n = 29) RESULTS: Panel 1, showed robust agreement with the HBsAg Qualitative II (HBsAgQII) assay (Cohen\'s kappa = 0.83). Despite this agreement, 7 false positive with the HBsAgQII assay were found negative with HBsAgNx. One OBI was detected only with HBsAgNx. Panel 2 showed potential time savings in diagnosing HBV-R using HBsAgNx among 4/18 HBsAg positives samples. Panel 3 highlighted the ability of HBsAgNx to detect HBsAg in OBI patients defined by negative for HBsAg with HBsAgQII assay and positive for HBV DNA. Furthermore, the HBsAgNx assay detected all different genotypes.
CONCLUSIONS: The study highlights the effectiveness of the HBsAgNx assay, showing its performance. It excels in detecting weakly positive samples and addressing challenging cases. HBsAgNx assay demonstrates promising analytical performances, with improved sensitivity and specificity compared to standard HBsAgQII assay, able to detect all genotypes. Its potential impact on early detecting and monitoring reactivations, and occult infections could be very useful in clinical practice.

Occult hepatitis B virus (HBV) infection (OBI) is a significant challenge for HBV prevention and control. We investigated the prevalence and surface (S) gene mutations of OBI among blood donors in Huzhou City, eastern China. The hepatitis B surface antigen (HBsAg) was routinely screened among 44,256 blood donors. HBV-DNA was detected using the Roche cobas®system. Serum samples that were HBsAg negative and HBV-DNA positive were selected, and the HBV S gene was amplified and sequenced. HBV genotype and S gene mutations were analyzed. The OBI rate in these blood donors was 0.070 % (31/44,256). Among the blood donors with OBI, only two cases (2/31, 6.5 %) were anti-HBc negative. The S gene sequences of 28 samples were successfully obtained, and we found that HBV genotype C (21/28, 70 %) was predominant among blood donors with OBI. Most S gene mutations were associated with OBI, and the high frequency mutations included N40S, G44E, Q51R/P, T113A/S,T118K/M, P120Q/S/T, and Y161F/S. Notably, amino acid substitutions at some sites differed from those reported previously, such as Y72F, G102V, P127L, Q129P, and S143T. Additionally, six novel mutations (S31I/N/R, P46L, S58C, C76Y, Y200F/C, and I208T) that may be associated with OBI were found. OBI was detected in a certain proportion of blood donors in Huzhou City. S gene mutations play an important role in OBI development. Further research is required to explore the functions of novel S gene mutants in OBI pathogenesis. The findings of this study may provide important insights to prevent HBV transmission through blood transfusions.

Despite good vaccine coverage and careful blood donor selection policies, hepatitis B virus (HBV) is still the most frequent viral infection among blood donors (BDs) in Italy, mostly in the occult form (OBI). We studied the virological features of OBI in BDs from South Italy by serology, molecular testing for HBV-DNA, and sequencing for HBV genotypes and mutations. One hundred and two samples from 95 BDs (22.1% first time, 87.9% regular, median age 57 years) positive for HBV-DNA and negative for HBsAg were retrospectively analyzed. HBV biomarkers were detected in 96.9% (anti-HBc in 44.2%, anti-HBc plus anti-HBs in 49.5%, anti-HBs alone in 3.2%). No risk factor was declared by 45.3% of donors. HBV-DNA levels were very low (median: 7 IU/mL). All samples harbored HBV genotype D and single or multiple mutations in the S gene were found in 28/36 sequences analyzed and in 75% of donors. Mutations were unrelated to gender, donor group or serological patterns. An HBsAg assay with enhanced sensitivity was positive in samples from seven donors (7.4%), two of which negative for HBV-DNA by real-time PCR. OBI still represents a risk for HBV transmission from blood donations; screening by highly sensitive serological and molecular assays is warranted.

We report a case of hepatitis B virus (HBV) reactivation in a renal transplant recipient. Reactivation manifested as an occult infection with detectable HBV-DNA and negativity for hepatitis B surface antigen (HBsAg). The anti-HBs antibody titre was above the protective threshold and continued to rise, to 951.36 mIU/ml, after HBV reactivation. Sequencing revealed multiple vaccine- and diagnostic-escape mutations in the major hydrophilic region of HBsAg. This case demonstrates both reactivation of an HBV escape mutant in a vaccinated patient and host immunity after virus mutation.

UNASSIGNED: Occult infections in spinal pseudarthrosis revisions have been reported in the literature, but the relevance of such an infection on patient outcomes is unknown. We aimed to elucidate clinical outcomes and re-revision risks between patients with and without occult infections in spinal revision surgery for pseudarthrosis.
UNASSIGNED: In this matched case-control study, we identified 128 patients who underwent thoracolumbar revision surgery from 2014-2019 for pseudarthrosis of the spine. Among them, 13 (10.2%) revealed an occult infection (defined by at least two positive intraoperative tissue samples with the same pathogen), and nine of these 13 were available for follow-up. We selected 18 of the 115 controls using a 2:1 fuzzy matching based on fusion length and length of follow-up. The patients were followed up to assess subsequent re-revision surgeries and the following postoperative patient-reported outcome measures (PROMs): overall satisfaction, Oswestry Disability Index, 5-level EQ-5D, and Short Form 36.
UNASSIGNED: Patient characteristics, surgical data, and length of follow-up were equal between both study groups. The rate of re-revision free survival after the initial pseudarthrosis revision surgery was higher in the occult infection group (77.8%) than the non-infectious controls (44.4%), although not significantly (0.22). The total number of re-revision surgeries, including re-re-revisions, was thirteen (in ten patients) in the control and two (in two patients) in the occult infection group (p = 0.08) after a median follow-up of 24 months (range 13-75). Four cases in the control group underwent re-revision for pseudarthrosis compared to none in the infected group. Satisfactory scores were recorded in all PROMs, with similar scores between the two groups.
UNASSIGNED: The presence of an occult infection accompanying spinal pseudarthrosis revision was not inferior to non-infected pseudarthrosis revisions in a matched, small sample size cohort study. This may be explained due to the possibility of targeted treatment of the identified cause of pseudarthrosis.

Pyomyositis is an infective involvement of systemic skeletal muscles. We discuss the case of 43-year-old male who presented with quadriparesis, anemia, and hypercalcemia, leading to suspicion of multiple myeloma, and on FDG PET-CT, incidentally, pyomyositis was found. FDG PET-CT thus helped in diagnosing an occult infection which helped in the treatment of the patient.

Absence of anti-HBc reactivity with detectable anti-HBs was observed in blood donors with occult hepatitis B virus (HBV) infection (OBI). The prevalence and mechanisms underlying this uncommon condition were investigated over time in Chinese blood donors with OBI. Isolated anti-HBs OBI status was identified from 466,911 donors from Dalian, China, and monitored in follow-up (range: 2.6-84.3 months). HBV vaccination status was documented, and infecting viral strains were characterized. Of 451 confirmed OBIs (1:1035), 43 (9.5%; 1:10,858) had isolated anti-HBs as only serological marker. Isolated anti-HBs OBIs differed from anti-HBc-reactive OBIs by significantly younger age (median 24 years), higher HBV DNA (median: 20 IU/ml) and anti-HBs (median 60.5 IU/L) levels, paucity of mutations in HBV Core and S proteins, and high vaccination rate (72%). Vaccinated isolated anti-HBs OBIs (n = 31) differed from unvaccinated (n = 11) by significantly younger age (22 vs 38 years), higher anti-HBs level at index (48% vs 9% with anti-HBs >100 IU/L) and higher frequency of anti-HBs immune response (44% vs 20%). Of 15 vaccinated and 5 unvaccinated OBIs follow-up, 65% (8 vaccinated and 5 unvaccinated) became HBV DNA negative suggesting aborted recent infection, while 35% (7 vaccinated) had low persistent viraemia 2 to 65 months post index. In conclusion, isolated anti-HBs OBI in Chinese blood donors appears associated with young, vaccinated, adults exposed to HBV who predominantly develop low level aborted infection revealed by transient HBV DNA and immune anti-HBs response. However, a subset of individuals still experienced low but persistent viral replication whose clinical outcome remains uncertain.

Dirofilaria repens is the causative agent of the zoonotic canine skin condition called subcutaneous dirofilariosis. Despite being endemic throughout much of Europe, little is known about host humoral responses to D. repens. To address this, we analyzed serum immunoglobulin isotypes recognizing D. repens somatic antigens (DrSA) in naturally infected dogs. Titers of anti-DrSA IgG and IgE, but not IgM were significantly higher in dogs infected with D. repens compared to those that were negative. Moreover, microfilaremic infections were associated with higher levels of IgG1 than IgG2, while occult infections occurred with significantly higher levels of IgG2 than IgG1. Finally, the measurement of anti-DrSA IgG antibodies allowed the detection of occult subcutaneous dirofilariosis in dogs.

This retrospective study was performed on 71 dogs which had been admitted for heartworm screening or with clinical suspicion of heartworm disease. The examination methods included polymerase chain reaction (PCR) to identify Dirofilaria immitis and/or Dirofilaria repens infections and a heartworm antigen (Ag) test (VetScan). By using PCR, 26 dogs were found positive only for Dirofilaria immitis (Group 1), while 21 dogs for both D. immitis and D. repens (Group 2). Group 3 included 24 dogs with D. repens infection only according to the PCR results. The sensitivity of the VetScan Ag test for the Group 1 and 2 animals proved to be 97.7% (95% Blaker confidence interval; CI 89.0%-99.9%). The specificity of the VetScan Ag test, calculated from the results of Group 3, was found to be 66.7% (95% CI 45.6%-83.1%), which was lower than that reported from the USA, where D. repens does not occur. In cases when PCR results were positive for D. repens but negative for D. immitis, the occult dirofilariosis was the likely explanation for the positive D. immitis Ag tests. These observations highlight the importance of performing more Ag tests simultaneously in those areas where both Dirofilaria species are present.