A 37-year-old Caucasian male with Wiskott-Aldrich syndrome (WAS) (IVS6 + 5G>A) developed anosmia and ageusia, followed by cough, dyspnoea, and fatigue (henceforth day 0). Community nasopharyngeal reverse-transcription PCR (RT-PCR) testing 1 day later was positive for SARS-CoV-2. Contact tracing suggested workplace exposure. Past medical history included childhood splenectomy for thrombocytopenia, eczema, recurrent infections, early bronchiectasis, asthma, and persistent molluscum contagiosum. Following diagnosis of specific antibody deficiency aged 24 years (based on suboptimal conjugated and unconjugated vaccine responses and reduced class switched memory B cells, described online supplementary), he was commenced on subcutaneous immunoglobulin replacement (SCIg) and maintained on 8 g/week with trough IgG levels of 12-15 g/L. Sinopulmonary infection history included RT-PCR-confirmed HKU1-coronavirus infection 12 months previously.
The patient was monitored via our virtual COVID-19 ward. Home pulse oximetry showed maintained peripheral saturations >96% on room air and admission to hospital was not indicated. Incomplete improvement in sense of smell and taste was noted after 2 months; however, he experienced fluctuating symptoms of chest tightness, dyspnoea, poor concentration, and fatigue approximately every fourth week and serial RT-PCR testing remained persistently positive (Fig. 1A, B). Inflammatory markers such as C-reactive protein (CRP) remained less than 12 mg/L and computed-tomography (CT) imaging of the chest at day 153 showed small airway inflammatory changes with widespread bilateral basal tree-in-bud and centrilobular micro-nodularity, which had evolved from imaging 5 years prior (online supplementary, Figure S1). At day 140, anti-spike S1 SARS-CoV-2 IgG remained absent. Whole blood-based interferon-gamma (IFNγ) release assay showed an equivocal T cell response to a SARS-CoV-2 peptide megapool covering the spike, nucleocapsid, and membrane glycoproteins (see online supplementary), potentially reflecting prior HKU1-infection. The absence of serum neutralizing antibodies and immunocompromised status have previously been associated with isolation of infectious SARS-CoV-2 from the respiratory tract and in view of the individual’s occupation requiring close contact with members of the public, self-isolation was continued.
Given persistent RT-PCR positivity, ongoing fluctuating symptoms and impact on both work and mental health of prolonged self-isolation, we adopted an individualized therapeutic approach. A growing range of therapeutic strategies have been suggested to counter SARS-CoV-2 infection in immunocompromised individuals including antibody therapies (convalescent plasma (CPT), hyperimmune IgG, and monoclonal antibodies) and antivirals. Rapid symptomatic and virological response have been reported following convalescent plasma therapy (CPT) in B cell-deficient individuals with protracted SARS-CoV-2, including where antiviral therapy with remdesivir has failed . However, use of CPT has been questioned following suggestion it may accelerate vaccine-escape mutations . Passive immunization with neutralizing monoclonal antibodies appear efficacious in post-exposure settings, particularly in seronegative individuals; however, this was not clinically accessible . We hypothesized stimulation of the endogenous immune response through therapeutic vaccination could support viral clearance. Two doses of bnt162b2 mRNA vaccination were administered 1 month apart, with mild flu-like symptoms only. Enhanced cellular responses and seroconversion were demonstrated 14 days following the first vaccine dose (Fig. 1C, D), with anti-SARS-CoV-2 spike IgG response exceeding thresholds commonly used for selection of convalescent plasma therapy. SARS-CoV-2-specific IFN-γ+ T cell increased significantly following vaccination to levels comparable to those induced among healthy controls. Anti-SARS-CoV-2 antibodies in immunoglobulin SCIg replacement were negative at this time (data not shown). A contemporaneous rise in RT-PCR cycle threshold (Ct) for detection by 6 cycles was noted across both viral nucleocapsid (N)-gene and ORF1a-gene targets. Given a difference of 1 Ct unit is approximately equivalent to a factor of 2 in the number of viral particles per sample, this represents a 64-fold decrease in viral genetic material recovered by nasopharyngeal swabbing 2 weeks following initial vaccination. SARS-CoV-2 clearance followed 72 days following first therapeutic vaccination dose (day 218 following initial RT-PCR detection).