Pathogenesis of Viral Respiratory Infection

Abstract

The term pathogenesis refers to the processes or mechanisms to generate an injury or illness, in this case induced by a viral infection. The results of a viral infection depend on factors related to the nature of the virus, the host and the environment. They include number of infectious particles, the way to reach the target tissue, the rate of multiplication, the effect of virus on cell functions and the host's immune response. Three requirements must be satisfied to ensure the infection of an individual host [ ]• Sufficient virus must be available to initiate infection,• Cells at the site of infection must be accessible, susceptible, and permissive for the virus• Local host anti-viral defense systems must be absent or initially ineffective.To infect its host, a virus must first enter cells at a body surface. Common sites of entry include the mucosal linings of the respiratory, alimentary and urogenital tracts, the outer surface of the eye conjunctival membranes or cornea , and the skin."mong the factors that affect the infection process are . Virus-dependent factors. They usually are dependent on the virus structure. a. Virulence. Virulence is under polygenic control and is not assignable to any isolated property of the virus, but is often associated to characteristics that favor viral replication and cellular injury. For example, virulent viruses multiply themselves readily at high temperatures prevailing during the disease, block the synthesis of interferon and macromolecules related to immune system. Viral virulence is a quantitative statement of the degree or extent of pathogenesis. In general, a virulent virus causes significant disease, whereas an avirulent or attenuated virus causes no or reduced disease, respectively.b. Measuring Viral Virulence. Virulence can be quantified in a number of different ways. One approach is to determine the concentration of virus that causes death or disease in % of the infected organisms. This parameter is called the % lethal dose LD , the % paralytic dose PD , or the % infectious dose ID , depending on the parameter that is measured. Other measurements of virulence include mean time to death or appearance of symptoms, as well as the measurement of fever or weight loss. Virus-induced tissue damage can be measured directly by examining histological sections or blood samples. For example, safety of live attenuated poliovirus vaccine is determined by assessing the extent of pathological lesions in the central nervous system in experimentally inoculated monkeys. Indirect measures of virulence include assays for liver enzymes alanine or aspartate amino-transferases that are released into the blood as a result of virus-induced liver damage [ ].

Lung transcriptome of a COVID-19 patient and systems biology predictions suggest impaired surfactant production which may be druggable by surfactant therapy

“…Antiviral immune responses and organ specific functions are dysregulated in lungs. During respiratory virus infections, many host pathways are fine-tuned to battle against the invading pathogen; on the other side, the infecting viruses also try to hijack and modulate host pathways for immune evasion and survival inside the host 22 . These complex interactions lead to the disease complexity, causing several critical pathophysiological conditions in host's respiratory system 22 .…”

“…During respiratory virus infections, many host pathways are fine-tuned to battle against the invading pathogen; on the other side, the infecting viruses also try to hijack and modulate host pathways for immune evasion and survival inside the host 22 . These complex interactions lead to the disease complexity, causing several critical pathophysiological conditions in host's respiratory system 22 . To explore which particular biological processes/pathways are dysregulated in SARS-CoV-2 infection, we first identified the dysregulated-genes in both SARS-CoV and SARS-CoV-2 infections and performed comparative functional enrichment analyses 23 .…”

Virus Mimetic Poly (I:C)-Primed Airway Exosomes Enter Brain and Induce Mitochondrial Reactive Oxygen Species in Microglia

“…Upper respiratory tract infections result in 10 million outpatient visits per year, and 70-90% of these infections are of viral origin [31,32]. Viral infections promote innate or non-specific and acquired or specific immune responses.…”

Formulations for COVID-19 Early Stage Treatment via Silver Nanoparticles Inhalation Delivery at Home and Hospital

“…Aggravation of the condition occurs once the pathogens and associated inflammation migrates to lower portions of the respiratory system. Moreover, as the infection spreads, the increased immune response is exacerbated and may cause a greater damage [3]. Therefore, we contend that a desirable effective treatment would be to suppress the proliferation of the pathogens at early stages of the infection, when it is cantered in the upper respiratory system.…”