Classification of Acellular Organisms

The HIV envelope protein gp120 binds to CD4. This targets the virus to this T-cell subset.

Pan Troglodytes Endogenous Retrovirus-1 is a retrovirus that putatively infected the chimpanzees about 4 million years ago and may have been involved in the process of speciation, making the chimpanzee and human lines diverge.

MASA syndrome, is a rare X-linked recessive neurological disorder. It is caused by mutations in the L1CAM gene.

Viroid RNA does not code for any protein. Their replication mechanism uses RNA polymerase II, a host cell enzyme normally associated with synthesis of messenger RNA from DNA, which instead catalyzes "rolling circle" synthesis of new RNA using the viroid's RNA as template.

In human Burkitt's lymphoma, work is in progress to develop a vaccine to exploit the ability of cytotoxic T-cells to target EBV-related antigens on the cells of all Burkitt's tumors. It may be an advantage to treat the patients at the same time with cytokines to upregulate the expression of ICAM-1, LFA-3 and possibly of the virus itself.

Theodor Otto Diener is an American plant pathologist and was the first in the field to describe viroids.Viroids were discovered and named by Theodor Otto Diener, a plant pathologist at the Agricultural Research Service in Maryland, in 1971.

Antibody-based immune responses form a first layer of protection of the host from viral infection; however, in many cases a vigorous cellular immune response mediated by T-cells and NK-cells is required for effective viral clearance. When cellular immunity is unable to clear the virus, the infection can become chronic, and serum antibodies to the viral pathogen are used as first indicator for the diagnosis of the disease.

CD8 numbers are largely unaffected. It is the ratio of CD4:CD8 that falls dramatically.

Proteins showing prion-type behavior are also found in some fungi, which has been useful in helping to understand mammalian prions. Fungal prions do not appear to cause disease in their hosts.

In plant tissue this virus makes characteristic viral inclusion bodies which can be diagnostic. They are hexagonal in shape   and stain both in a protein stain and a nucleic acid stain.The inclusions can also be rhomboidal   may appear hollow  and can form larger aggregates. The inclusions are not uniformly distributed and can be found in epidermal, mesophyll and stomata cells.

it thereby prevents effective presentation of antigen peptides to the T-cell receptor

Interferon inhibits the intracellular replication of viruses.

FDCs naturally express high levels of the normal prion protein which then becomes abnormal following exposure to the transmissible spongiform encephalopathy (TSE) agent.

Exotic ungulate encephalopathy is a transmissible spongiform encephalopathy (TSE), or prion disease, identified in infected organs of zoo animals.

In this group, some or all of the genes are translated into protein from an RNA strand complementary to that of the genome (as packaged in the virus particle). There are some plant viruses in this group and it also includes the viruses that cause measles, influenza and rabies.

Hoppers transmit viruses from several genera, including those in the families Rhabdoviridae and Reoviridae.

Virusoids are circular single-stranded RNAs dependent on plant viruses for replication and encapsidation.[1] The genome of virusoids consist of several hundred nucleotides and does not code for any proteins

This is not thought to be due to an infection but a relatively benign form of leukaemia in the elderly.

There are at least 93 serotypes in the world, though 23 prevalent serotypes that cause disease in different parts of the world, but no switching of the bacterium between serotypes. Infections with these organisms are common and often infect those with antibody or innate or combined deficiencies.

This is contracted by wrestlers. It apparently spreads by direct contact from skin lesions on one wrestler to his/her opponent, and usually appears in the head and neck region (which are frequently sites of contact in wrestling holds).

CMV is an example of a herpes virus; these are all large DNA viruses of which CMV is the largest; is also known as human herpesvirus-5 (HHV-5).

SV40 virus was initially discovered in the rhesus monkey kidney cells that were used to make inactivated Salk polio vaccine virus.

Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome and may have relatively simple or elaborate structures. Their genomes may encode as few as four genes and as many as hundreds of genes.

The ability to interchange large segments of the genome with a viral reservoir in other animal species is the basis of antigenic shift leading to radical change in antigen, particularly crucial antigens giving protective immunity such as the viral hemagglutinin.

CXCR4 is a chemokine receptor which HIV utilizes as a coreceptor for entry into naive CD4+ T-cells and mature dendritic cells. Another chemokine receptor, CCR5, is used particularly for entry of HIV into immature dendritic cells, macrophages and activated effector or memory CD4+ T-cells.

gp120 is an envelope protein which binds to CD4 on the T-cell. Antibodies to the V3 loop of gp120 arise during the disease and are particularly effective as neutralising agents in vitro, although less so in vivo. Generally, neutralising antibodies are more effective against HIV-2 than against HIV-1.

LMP1 is the best-documented oncoprotein of the Epstein–Barr virus (EBV), latent gene products.

They protect by neutralizing a function of the pathogen such as the harmful part of a toxin or a viral coat protein which binds to a cell-surface viral receptor on the host cells.

Oat blue dwarf virus (OBDV) is a plant pathogenic virus of the family Tymoviridae. It replicates within leafhopper vectors, and when these vectors feed, the virus is transmitted to the plant. It can infect oats and barley.

Geminate viruses are twinned isometric particles about 30 x 18 nm. These particles are diagnostic for viruses in the family Geminiviridae which are widespread in many crops especially in tropical regions. The example includes Maize streak virus, genus Mastrevirus.

Jonas Edward Salk was an American medical researcher and virologist. He discovered and developed the first successful inactivated polio vaccine.

The virion enters early endosomes by Macropinocytosis.Attachment to host receptors through GP glycoprotein mediates is endocytosed into vesicles in the host cell. Host DC-SIGN and DC-SIGNR play a role in virion attachment.

Cucumber yellows virus (CuYV) is a species of virus that infects plants, specifically the cucumber and melon. It is transmitted by the greenhouse whitefly. The cucumber yellows virus genome was completely sequenced in 2003.

The virion RNA is infectious and serves as both the genome and the viral messenger RNA. The whole genome is translated in a polyprotein, which is processed co- and post-translationally by host and viral proteases.

The smooth unblemished skin of milkmaids gave Jenner the idea of using cowpox. The cowpox virus is non-virulent in man but shares antigens with the related smallpox virus and is therefore able to elicit protection against subsequent infection with smallpox.

Type I genomes are characterized by a small circular DNA genome (approximately 2-kb), with the Rep protein and the major open reading frame (ORF) in opposite orientations. This type is characteristic of the circoviruses, geminiviruses and nanoviruses.

Celery mosaic, like most potyviruses, is non-persistently transmitted by aphids. This means that the aphid can pick up the virus on its stylet (its mouthparts) and transfer it quickly to the next plant it probes. The virus can also be transmitted mechanically by tools and machinery. There is no evidence of seed transmission.