Stability of cytomegalovirus antibodies in plasma during prolonged storage of blood components

Estimation of sensitivity and specificity of bulk tank milk PCR and 2 antibody ELISA tests for herd-level diagnosis of Mycoplasma bovis infection using Bayesian latent class analysis

Mycoplasmosis (due to infection with Mycoplasma bovis) is a serious disease of beef and dairy cattle that can adversely impact health, welfare and productivity (Maunsell et al. (2011)). Mycoplasmosis can lead to a range of often severe, clinical presentations. Mycoplasma bovis (M. bovis) infection can present either clinically or subclinically, with the potential for recrudescence of shedding in association with stressful periods. Infection can be maintained within herds because of intermittent shedding (Calcutt et al., 2018, Hazelton et al., 2018). M. bovis is recognized as poorly responsive to treatment which represents a major challenge for control in infected herds. Given this, particular focus is needed on biosecurity measures to prevent introduction into uninfected herds in the first place. A robust and reliable laboratory test for surveillance is important both for herd-level prevention and control. The objective of this study was to estimate the sensitivity and specificity of 3 diagnostic tests (one PCR and 2 ELISA tests) on bulk tank milk, for the herd-level detection of M. bovis using Bayesian latent class analysis. In autumn 2018, bulk tank milk samples from 11,807 herds, covering the majority of the main dairy regions in Ireland had been submitted to the Department of Agriculture testing laboratory for routine surveillance were made available. A stratified random sample approach was used to select a cohort of herds for testing from this larger sample set. A final study population of 728 herds had bulk tank milk samples analyzed using a Bio-X ELISA (ELISA 1), an IDvet ELISA (ELISA 2) and a PCR test. A Bayesian latent class analysis (BLCA) was conducted to estimate the sensitivity (Se) and specificity (Sp) of the 3 diagnostic tests applied to bulk tank milk (BTM) for the detection of the herd-level infection. An overall LCA was conducted on all herds within a single population (a 3-test, 1-population model). The herds were also split into 2 populations based on herd size (small herds had < 82 cattle) (a 3-test, 2-population model) and separately into 3 regions in Ireland (Leinster, Munster and Connacht/Ulster) (a 3-test, 3-population model). The latent variable of interest was the herd-level M. bovis infection status. In total, 363/728 (50%) were large herds, 7 (1.0%) were positive on PCR, 88 (12%) positive on ELISA 1, and 406 (56%) positive on ELISA 2. Based on the 2-population model, the sensitivity (95% Bayesian credible interval (BCI) was 0.03 (0.02, 0.05), 0.22 (0.18, 0.27), 0.94 (0.88, 0.98) for PCR, ELISA 1 and ELISA 2 respectively. The specificity (95% BCI) was 0.99 (0.99, 1.0), 0.97 (0.95, 0.99), and 0.92 (0.86, 0.97) for PCR, ELISA 1 and ELISA 2 respectively. The herd-level true prevalence was estimated at 0.43 (BCI 0.35, 0.5) for smaller herds. The true prevalence was estimated at 0.62 (BCI 0.55, 0.69) for larger herds. The true prevalence was estimated at 0.56 (BCI 0.49, 0.463) in the 1-population model. For the 3-population model, the sensitivity (95% BCI) was 0.03 (0.02, 0.05), 0.24 (0.18, 0.29), 0.95 (0.9, 0.98) for PCR, ELISA 1 and ELISA 2 respectively. The specificity (95% BCI) was 0.99 (0.99, 1.0), 0.98 (0.96, 0.99), and 0.88 (0.79, 0.95) for PCR, ELISA 1 and ELISA 2 respectively. The herd-level true prevalence (95% BCI) was estimated at 0.65 (0.56, 0.73), 0.38 (0.28, 0.46) and 0.53 (0.4, 0.65) for population 1, 2, 3 respectively. Across all 3 models, the range in true prevalence was 38% to 65% of Irish dairy herds infected with M. bovis. The operating characteristics vary substantially between tests. The IDvet ELISA had a relatively high Se (the highest Se of the 3 tests studied) but it was estimated at 0.95 at its highest in 3-test, 3-population model. This test may be an appropriate test for herd-level screening or prevalence estimation within the context of the endemically infected Irish dairy cattle population. Further work is required to optimize this test and its interpretation when applied at herd-level to offset concerns related to the lower than optimal test Sp.

Immune function, cortisol, and cognitive decline & dementia in an aging latino population

BACKGROUND

The etiology of dementias and cognitive decline remain largely unknown. It is widely accepted that inflammation in the central nervous system plays a critical role in the pathogenesis of dementia. However, less is known about the role of the peripheral immune system and interactions with cortisol, though evidence suggests that these, too, may play a role.

METHODS

Using data from 1337 participants aged 60+ years from the Sacramento Area Latino Study of Aging (observational cohort) we investigated variation in trajectories of cognitive decline by pathogen IgG and cytokine levels. Linear mixed effects models were used to examine the association between baseline Interleukin (IL)-6, C-reactive protein, tumor necrosis factor (TNF)-α, and five persistent pathogens' IgG response and trajectories of cognition over 10 years, and to examine interactions between immune biomarkers and cortisol. Stratified cumulative incidence functions were used to assess the relation between biomarkers and incident dementia. Inverse probability weights accounted for loss-to-follow-up and confounding.

RESULTS

IL-6, TNF-α, and CMV IgG were statistically significantly associated with a higher log of Modified Mini-Mental State Examination errors (IL-6, β=0.0935 (95%CI: 0.055, 0.13), TNF-alpha β= 0.0944 (95%CI: 0.032, 0.157), and CMV, β= 0.0409 (95%CI: 0.013, 0.069)). Furthermore, cortisol interacted with HSV-1 and IL-6, and CRP for both cross-sectional cognitive function and rate of decline. No statistically significant relationship was detected between biomarkers and incidence of dementia.

CONCLUSIONS

These findings support the theory that the peripheral immune system may play a role in cognitive decline but not incident dementia. Furthermore, they identify specific markers amenable for intervention for slowing decline.

Breast cancer, cytomegalovirus and Epstein-Barr virus: a nested case-control study

BACKGROUND

We investigated whether elevation in serum cytomegalovirus (CMV) or Epstein-Barr virus (EBV) immunoglobulin G (IgG) antibody levels precedes the development of breast cancer.

METHODS

A nested case-control study was carried out within the Janus Serum Bank cohort. Two serum samples, one taken at least 4 years before diagnosis (sample 2) and an earlier sample (sample 1) from 399 women with invasive breast cancer and from 399 controls, matched for date of blood samples and age were tested for CMV and EBV IgG antibodies. Odds ratios (ORs) with 95% confidence intervals (CIs) for CMV and EBV seroconversion between the samples and unit changes in IgG optical density (OD) examined as a continuous variable were calculated using conditional logistic regression.

RESULTS

Eleven cases and three controls seroconverted for CMV IgG between the first and second blood samples, with an adjusted OR for CMV IgG seroconversion of 4.0 (95% CI=1.1-14.4). The risk of breast cancer, adjusted for parity, increased per unit difference in CMV OD between samples (OR=1.7, 95% CI=1.1-2.5). In an analysis restricted to parous cases and age-matched parous controls, the OR for CMV seroconversion for IgG between the two samples, adjusted for parity and age at first birth, was 9.7 (95% CI=1.2-77.3). The EBV seroconversion or change in EBV OD was not associated with risk of breast cancer.

CONCLUSION

Our hypothesis that elevation in serum CMV IgG antibody levels precedes the development of breast cancer in some women is supported by the results of this study. Changes in EBV IgG antibody are not associated with risk of breast cancer.

Suitability of frozen serum stored in gel separator primary sampling tubes for serological testing

The suitability of frozen serum after storage in primary sampling tubes with a gel separator for serological enzyme-linked immunosorbent assay testing (hepatitis B virus surface antigen [HBs Ag], anti-HBs Ag, anti-Toxoplasma gondii immunoglobulin G [IgG], anti-rubella virus IgG, anti-cytomegalovirus IgM, and anti-Epstein-Barr virus IgM) was evaluated for 375 samples. No difference was found among test results using fresh or stored frozen serum