Here are a couple more quotes that I found online about it. I'm sure you're researching plenty yourself and may have found the same thing:

Zoologix
Feline calicivirus (FCV) infection causes upper respiratory tract (pneumotropic form) infection and occasionally causes joint pain and lameness (rheumatic form). Feline calicivirus is a single-stranded RNA virus with a worldwide distribution, affecting domestic cats and a few wild felid species.

FCV is transmitted by ingestion or inhalation of infectious virus present in saliva and excretions from affected cats. The oral route of infection is most important, and direct contact with infected cats or contaminated fomites is the primary method of transmission rather than aerosolized particulates. The virus is highly contagious. Cats of all ages can be affected by FCV infection but kittens are more likely to develop symptoms.

FCV mainly infects the oral and respiratory tissues. Different strains of FCV may have affinities to different tissues. Some strains have a predilection for the lung, and other strains have been found in the macrophages within the synovial membrane of joints. The virus can also be found in visceral tissues, feces, and occasionally in urine.

Infected cats usually develop vesicles and erosions of the tongue, hard palate, and nasal planum. Healing takes more than two weeks. Recovered cats often remain lifelong carriers of FCV and can shed virus continually. PCR testing of throat swabs is extremely helpful for the monitoring of viral shedding. Feline calicivirus carriers are quite common despite vaccination. Vaccination protects against full blown disease but does not reliably prevent infection.
An indepth article from AnimalHealthChannel.com

Symptoms
Calicivirus affects the upper respiratory system, the eyes, the musculoskeletal system, and the gastrointestinal tract. Common symptoms include the following:

Acute, painful lameness due to tenderness in the joints (arthritis) or muscles (myalgia)
Fever
Mild loss of appetite
Pneumonia, often accompanied by labored, difficult breathing
Ulcerations (pus-filled sores) on the tongue, palate, lips, or tip of the nose
Ulcers around the claws, on the bottom of the feet and between the toes
Upper respiratory infection with eye and nose discharge, (usually with little sneezing)
Calicivirus infection usually develops suddenly. Most infected cats appear healthy and alert; they may have ulcers and no other symptoms (i.e., no fever or pain). Some cats may have mild secondary bacterial infections that are similar to those associated with FHV.
I do find it interesting that none of the information I'm finding, these I posted and others, mention coughing as a symptom. Perhaps he has something else. Does he have any of these other symptoms being mentioned?