Infectious diseases result from the interplay between pathogens and the defenses of the hosts they infect. Pathogens include viruses, bacteria, fungi, parasites, protozoa and prions (infectious protein molecules such as the ones causing Bovine Spongiform Encephalopathy (BSE), also known as mad cow disease). Infectious diseases are transmissible (communicable). Infecting agents may be transmitted through liquids, food, body fluids, contaminated objects, airborne inhalation, or through vector-borne spread.
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Human diseases caused by viruses include the common cold, chickenpox,
shingles, influenza, avian influenza, hepatitis, acquired Immunodeficiency
syndrome (AIDS), SARS, multiple sclerosis, type I diabetes, and certain types of
cancer. Cancer-causing viruses are human papillomavirus, hepatitis B virus,
hepatitis C virus, Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus,
and human T-lymphotropic virus. Also, Merkel cell polyomavirus causes most cases
of a rare form of skin cancer called Merkel cell carcinoma.
The innate immune system is the first line of defense against viruses. RNA
interference is an important innate defense mechanism in which the RNA-Inducing
Silencing Complex (RISC) degrades the viral mRNA and the cell survives the
infection. Adaptive immunity - humoral immunity and cellular immunity, is the
second line of defense evoked by virus infection. Many viruses, however, such as
human immunodeficiency virus (HIV), can evade the immune system by constantly
changing the amino acid sequence of the proteins on the surface of the virus.
SABiosciences' Innate and Adaptive Immune Response PCR arrays, Toll-Like
Receptors PCR arrays, T-Cell and B-Cell Activation PCR arrays, and Interferon
alpha, beta Response PCR arrays can be used to study the genes involved in the
activation of immune system.
HIV causes acquired Immunodeficiency syndrome (AIDS), a disease first
discovered in 1981. HIV is a lentivirus (lenti-, Latin for "slow"),
which are members of retrovirus family. More than 30 million people worldwide
are living with HIV infection. HIV infects immune cells such as helper CD4+ T
cells, macrophages, dendritic cells, and microglial cells. When CD4+ T cell
numbers decline below a critical level, cellular immunity is lost, and the body
becomes progressively more susceptible to opportunistic infections. There are
two species of HIV: HIV-1 and HIV-2. HIV-2 is much less pathogenic than HIV-1
and is restricted in West Africa. Currently there is no publicly available
vaccine or cure for AIDS. However, progression from HIV infection to AIDS and
HIV-related mortality can be reduced effectively by several years of treatment
with highly active antiretroviral therapy (HAART). SABiosciences' HIV Infection
and Host Response PCR arrays can help you study the gene expression involved in
this pathological process.
Hepatitis A is an acute, non-progressive liver inflammation caused by the
hepatitis A virus (HAV), which is most commonly transmitted by contaminated food
or drinking water. Persistent hepatitis B (HBV) or C virus (HCV) infection,
however, often leads to liver cirrhosis and hepatocellular carcinoma (HCC). HAV,
HBV, and HCV are distinctively different both genetically and clinically with
HBV and HCV infection also sharing common autoimmune manifestations and
lymphoproliferative nature. More than 170 million people are infected by HCV.
The highly replicative nature of HCV, coupled with error-prone viral RNA
synthesis and considerable genome diversity, pose extraordinary challenges to
therapy development. Unlike hepatitis A and B, currently there is neither an
effective antiviral therapy nor a vaccine for hepatitis C. Two essential factors
involved in HCV entry into hepatocytes are the tight junction proteins claudin-1
and occludin. Cell polarity therefore seems to be a key for HCV entry. Endocrine
and cytokine metabolic abnormalities in HCV and HIV infections have been
observed. In particular, insulin resistance and liver damage in the
pathophysiology of HCV and HIV infections are prominent.
Another two serious infectious diseases affecting a vast number of people are
malaria and tuberculosis. Each year, there are approximately 350-500 million
cases of malaria, killing between 1 and 3 million people, especially children.
Malaria is transmitted by the bite of a female mosquito. The malaria parasites
multiply within human red blood cells, causing symptoms of fever and headache. A
wide variety of antimalarial drugs are available to treat malaria. Vaccines for
malaria are under development, with no completely effective vaccine yet
available.
Respiratory infections are the most common communicable infectious diseases.These diseases include tuberculosis, influenza, SARS, and measles, together
accounting for 25% of infectious causes of death worldwide. Tuberculosis is
caused by various strains of mycobacteria, usually Mycobacterium tuberculosis in
humans. A third of the world's population is infected with Mycobacterium
tuberculosis, and 2 million people die from it every year. The only tuberculosis
vaccine currently available is an attenuated strain of Mycobacterium bovis BCG.
Multi-drug resistance is becoming a major challenge for tuberculosis treatment.
Most infections in humans result in a latent asymptomatic infection, and about
one in ten latent infections eventually progresses to active disease, which, if
left untreated, kills more than 50% of its victims. Toll-like receptors (TLRs)
seem to play a major role in this immune latency. Immune evasion allows
Mycobacterium tuberculosis to establish persistent or latent infection in
macrophages and results in Toll-like receptor 2 (TLR2)-dependent inhibition of
MHC class II transactivator expression, MHC class II molecule expression, and
antigen presentation. SABiosciences' T-Cell Anergy and Immune Tolerance PCR
arrays and Dendritic and Antigen Presenting Cell PCR arrays can be used to study
the immune latency.
Fungal infection is another category of infection. It usually occurs in
immunocompromised (a person who has an immunodeficiency of any kind is
considered immunocompromised) or hospitalized people with serious underlying
diseases, such as diabetic patients. Fungal infection is also called mycosis.
Like other pathogens, fungi initially interact with the innate immune system
through binding between fungus-specific chemical motifs and pattern recognition
receptors (PRRs) on mononuclear phagocytes. Therefore Toll-like receptors (TLRs)
are key mediators in innate anti-fungal immunity. In general, the recent
understanding of the interaction between pathogens and the host immune system
recognizes that autophagy is a key component of both innate and adaptive
immunity to pathogens. Signaling through innate pattern recognition receptors (PRRs)
leads to the induction of autophagy. Autophagy restricts viral infections as
well as replication of intracellular bacteria and parasites and delivers
pathogenic determinants for TLR stimulation and for MHC class II presentation to
the adaptive immune system. Apart from its role in defense against pathogens,
autophagy-mediated presentation of self-antigens has a crucial role in the
induction and maintenance of T-cell tolerance. SABiosciences' Autophagy PCR
arrays and TLRs PCR arrays are two powerful tools that can be used to study
infection.
