Viral infections causing asthma exacerbations in the age of biologics and the COVID-19 pandemic

PURPOSE OF REVIEW

Asthma exacerbations are associated with substantial symptom burden and healthcare costs. Viral infections are the most common identified cause of asthma exacerbations. The epidemiology of viral respiratory infections has undergone a significant evolution during the COVID-19 pandemic. The relationship between viruses and asthmatic hosts has long been recognized but it is still incompletely understood. The use of newly approved asthma biologics has helped us understand this interaction better.

RECENT FINDINGS

We review recent updates on the interaction between asthma and respiratory viruses, and we address how biologics and immunotherapies could affect this relationship by altering the respiratory mucosa cytokine milieu. By exploring the evolving epidemiological landscape of viral infections during the different phases of the COVID-19 pandemic, we emphasize the early post-pandemic stage, where a resurgence of pre-pandemic viruses with atypical seasonality patterns occurred. Finally, we discuss the newly developed RSV and SARS-CoV-2 vaccines and how they reduce respiratory infections.

SUMMARY

Characterizing how respiratory viruses interact with asthmatic hosts will allow us to identify tailored therapies to reduce the burden of asthma exacerbations. New vaccination strategies are likely to shape the future viral asthma exacerbation landscape.

The Majority of SARS-CoV-2 Plasma Cells are Excluded from the Bone Marrow Long-Lived Compartment 33 Months after mRNA Vaccination

The goal of any vaccine is to induce long-lived plasma cells (LLPC) to provide life-long protection. Natural infection by influenza, measles, or mumps viruses generates bone marrow (BM) LLPC similar to tetanus vaccination which affords safeguards for decades. Although the SARS-CoV-2 mRNA vaccines protect from severe disease, the serologic half-life is short-lived even though SARS-CoV-2-specific plasma cells can be found in the BM. To better understand this paradox, we enrolled 19 healthy adults at 1.5-33 months after SARS-CoV-2 mRNA vaccine and measured influenza-, tetanus-, or SARS-CoV-2-specific antibody secreting cells (ASC) in LLPC (CD19 - ) and non-LLPC (CD19 + ) subsets within the BM. All individuals had IgG ASC specific for influenza, tetanus, and SARS-CoV-2 in at least one BM ASC compartment. However, only influenza- and tetanus-specific ASC were readily detected in the LLPC whereas SARS-CoV-2 specificities were mostly excluded. The ratios of non-LLPC:LLPC for influenza, tetanus, and SARS-CoV-2 were 0.61, 0.44, and 29.07, respectively. Even in five patients with known PCR-proven history of infection and vaccination, SARS-CoV-2-specific ASC were mostly excluded from the LLPC. These specificities were further validated by using multiplex bead binding assays of secreted antibodies in the supernatants of cultured ASC. Similarly, the IgG ratios of non-LLPC:LLPC for influenza, tetanus, and SARS-CoV-2 were 0.66, 0.44, and 23.26, respectively. In all, our studies demonstrate that rapid waning of serum antibodies is accounted for by the inability of mRNA vaccines to induce BM LLPC.

COVID-19 and plasma cells: Is there long-lived protection?

Infection with SARS-CoV-2, the etiology of the ongoing COVID-19 pandemic, has resulted in over 450 million cases with more than 6 million deaths worldwide, causing global disruptions since early 2020. Memory B cells and durable antibody protection from long-lived plasma cells (LLPC) are the mainstay of most effective vaccines. However, ending the pandemic has been hampered by the lack of long-lived immunity after infection or vaccination. Although immunizations offer protection from severe disease and hospitalization, breakthrough infections still occur, most likely due to new mutant viruses and the overall decline of neutralizing antibodies after 6 months. Here, we review the current knowledge of B cells, from extrafollicular to memory populations, with a focus on distinct plasma cell subsets, such as early-minted blood antibody-secreting cells and the bone marrow LLPC, and how these humoral compartments contribute to protection after SARS-CoV-2 infection and immunization.

Antiviral CD8+ T Cells Restricted by Human Leukocyte Antigen Class II Exist during Natural HIV Infection and Exhibit Clonal Expansion

CD8⁺ T cell recognition of virus-infected cells is characteristically restricted by major histocompatibility complex (MHC) class I, although rare examples of MHC class II restriction have been reported in Cd4-deficient mice and a macaque SIV vaccine trial using a recombinant cytomegalovirus vector. Here, we demonstrate the presence of human leukocyte antigen (HLA) class II-restricted CD8⁺ T cell responses with antiviral properties in a small subset of HIV-infected individuals. In these individuals, T cell receptor β (TCRβ) analysis revealed that class II-restricted CD8⁺ T cells underwent clonal expansion and mediated killing of HIV-infected cells. In one case, these cells comprised 12% of circulating CD8⁺ T cells, and TCRα analysis revealed two distinct co-expressed TCRα chains, with only one contributing to binding of the class II HLA-peptide complex. These data indicate that class II-restricted CD8⁺ T cell responses can exist in a chronic human viral infection, and may contribute to immune control.

•

CD8⁺ T cells restricted by HLA-DRB1 exist in a small number of HIV-infected persons

•

These CD8⁺ T cells exhibit potent antiviral functions against HIV-infected cells

•

TCRβ usage patterns indicate clonal expansion of class II-restricted CD8⁺ T cells

•

CD8⁺ T cells that violate immunologic paradigms may contribute to viral control

Role of T cell receptors in suppressing HIV infection in elite controllers

Virtually all HIV-infected patients progress to AIDS if not treated. A group of patients, called Elite Controllers (ECs), can suppress HIV infection without treatment. This ability of ECs is, in part, due to potent CD8+ T cell (CTL) responses against HIV epitopes presented by human leukocyte antigen (HLA) molecules. In this study, we focused on CTL responses restricted to HLA-B27, an allele that is enriched in ECs, but is not sufficient for protective ability. In HLA-B27+ ECs or non-controllers (NCs), immunodominant CTL responses specific to the KK10 epitope in Gag are found. Previous studies have shown that unlike NCs, B27-KK10-specific CTLs from ECs are efficient at eliminating HIV-infected or KK10-peptide pulsed cells. As the potency of CTLs can be modulated by their T cell receptor (TCR), we hypothesized that B27-KK10-specific TCRs play a significant role in suppressing HIV in ECs. Therefore, we cloned B27-KK10-specific TCRs from ECs or NCs, expressed them in primary T cells, and tested their cytotoxicity. We incubated TCR-transduced T cells with either HIV-infected or KK10-peptide pulsed target cells and measured target cell lysis. Unexpectedly, EC-TCRs were not significantly different than NC-TCRs in their cytotoxicity. We then tested the ability of these cells to suppress HIV in humanized mice and found no significant difference between EC- and NC-TCRs. We are currently investigating various aspects of these TCRs such as cross-reactivity to variants of KK10. The result that TCRs from ECs and non-controllers do not recapitulate the phenotype of CTLs is intriguing and warrants further studies to uncover the mechanism of immunologic control of HIV. Our studies also have implications in immunotherapy and vaccine approaches for HIV.

Endothelial dysfunction in recently diagnosed type 2 diabetic patients evaluated by PET

PURPOSE

To demonstrate the presence of endothelial dysfunction (ED) in asymptomatic patients with type 2 diabetes mellitus (DM) by using (13)N-ammonia-positron emission tomography (PET). PET can identify ED by quantifying myocardial blood flow (MBF) during rest, cold pressor test (CPT), and pharmacologic stress. The endothelial-dependent vasodilation index (EDVI), myocardial flow reserve (MFR), and the percentage of the change between rest and CPT (%DeltaMBF) are markers of endothelial function.

PROCEDURES

Thirty-nine subjects were studied (19 women and 20 men); 22 recently diagnosed type 2 diabetic patients and 17 healthy controls (HC). A three-phase (13)N-ammonia-PET was performed.

RESULTS

Mean EDVI was 1.208 +/- 0.34 vs. 1.55 +/- 0.37 (diabetic vs. HC group, respectively) (p = 0.002), MFR was 2.803 +/- 1.39 vs. 3.27 +/- 0.72 (p = NS), and the %DeltaMBF was 20 +/- 34% vs. 55 +/- 37% (p = 0.002). Rest MBF and CPT MBF were normalized to the rate pressure product (RPP). EDVI' and %DeltaMBF' were calculated using the corrected values for the RPP. Mean EDVI' was (0.864 +/- 0.250 vs. 1.110 +/- 0.238, p = 0.004) and mean %DeltaMBF' was (-8.2 +/- 14.7% vs. 4.5 +/- 12.1%, p = 0.005).

CONCLUSIONS

Asymptomatic, recently diagnosed type 2 diabetes patients present ED that can be quantified by (13)N-ammonia-PET.

Nutritional support of the chronically ill elderly female at risk for elective or urgent surgery

Among the elderly, those at highest risk are the chronically ill, inactive patients. Assessing macronutrient requirements and outcome depends on longitudinal studies. Seven chronically ill, elderly female patients suffering from persistent infections, were studied monthly, over a 6-month period to determine their protein and energy requirements. Calorie and protein requirements were based on clinical status. The results of the nutrition support program were monitored using: weight change, nitrogen balance, serum albumin levels, alterations in anthropometric measurements (triceps skinfold thickness and arm muscle circumference), and immune function tests. Based on the 6-month study period data, the calculated mean energy requirement for weight maintenance was 98% of calculated basal energy expenditure (BEE) and the mean protein required for nitrogen balance, 0.8 g/kg desired body weight (DBW). Excess caloric administration resulted in weight gain, determined to be fat (and/or fluid) but not lean body mass. When surgery is contemplated, there should be a 30% (factorial) increase over these base-line values. It is inadvisable to allow elderly patients to sustain any starvation, period given their inability to produce increases in body cell mass even in this 6-month period.