Understanding the dynamics of COVID-19; implications for therapeutic intervention, vaccine development and movement control.

The COVID-19 disease is caused by the SARS-CoV-2 virus, which is highly infective within the human population. The virus is widely disseminated to almost every continent with over twenty-seven million infections and over ninety-thousand reported deaths attributed to COVID-19 disease. SARS-CoV-2 is a single stranded RNA virus, comprising three main viral proteins; membrane, spike and envelope. The clinical features of COVID-19 disease can be classified according to different degrees of severity, with some patients progressing to acute respiratory distress syndrome, which can be fatal. In addition, many infections are asymptomatic or only cause mild symptoms. As there is no specific treatment for COVID-19 there is considerable endeavour to raise a vaccine against SARS-CoV-2, in addition to engineering neutralizing antibody interventions. In the absence of an effective vaccine, movement controls of varying stringencies have been imposed. Whilst enforced lockdown measures have been effective, they may be less effective against the current strain of SARS-CoV-2, the G614 clade. Conversely, other mutations of the virus, such as the Δ382 variant could reduce the clinical relevance of infection. The front runners in the race to develop an effective vaccine focus on the SARS-Co-V-2 Spike protein. However, vaccines that produce a T-cell response to a wider range of SARS-Co-V-2 viral proteins, may be more effective. Population based studies that determine the level of innate immunity to SARS-CoV-2, from prior exposure to the virus or to other coronaviruses, will have important implications for government imposed movement control and the strategic delivery of vaccination programmes.

Synthetic 2'-O-methyl-modified hammerhead ribozymes targeted to the RNA component of telomerase as sequence-specific inhibitors of telomerase activity.

Telomerase is a ribonucleoprotein that synthesizes tandem arrays of the hexameric DNA sequence TTAGGG at chromosome termini using its RNA component as a template. As most normal cells lack telomerase activity, a progressive shortening of chromosome length occurs with each cell division because of incomplete DNA replication. Cell senescence ensues when a critical telomere length is reached, but importantly, senescence bypass and life span extension occur in normal cells transfected with functional telomerase activity. Almost 90% of all tumors express telomerase activity, implying that telomerase is an important determinant in tumor progression and cell immortalization. However, the exact role and regulation of the individual components of the telomerase complex are not fully understood and would benefit from the availability of specific inhibitors. In this study, we investigated the potential use of chemically stabilized, catalytic RNA molecules (hammerhead ribozymes) to inhibit telomerase activity by cleaving the RNA component in a sequence-specific manner. Catalytically competent (active) hammerhead ribozymes containing 2'-O-methyl ribonucleotides for enhanced biologic stability and designed to be complementary to the RNA component of human telomerase exhibited dose-dependent inhibition of telomerase activity in human glioma U87-MG cell lysates with an IC50 of around 0.4 microM. Catalytically incompetent (inactive) ribozymes or mismatched ribozymes with reduced hybridization capability to telomerase RNA did not inhibit telomerase activity, as detected by a PCR-based telomeric repeat amplification protocol (TRAP) assay. In vitro cleavage reactions using short substrates and RT-PCR analyses of the full-length RNA substrate in U87-MG cell lysates confirmed a sequence-specific catalytic cleavage of the targeted RNA component of telomerase. Exogenously administrable, synthetic ribozymes may have important uses in further understanding the role and regulation of this ribonucleoprotein in normal and diseased tissues as well as in the potential therapy of telomerase-positive tumors.